CA2052691C - Method of dynamically monitoring the orientation of a curve drilling assembly - Google Patents

Abstract

A method for monitoring the rotational orientation of a downhole tool on a rotatable conduit while drilling, comprising the steps of establishing an initial rotational orientation of the downhole tool with respect to a plurality of reference points on the rotatable conduit, generating at least one reference signal each time the reference points and the rotatable conduit complete 360 degrees of rotation while drilling, generating a tool signal each time the rotatable conduit is in a defined rotational orientation with respect to the downhole tool while drilling, and measuring the angular displacement between the reference signal and the tool signal.

Description

PATENT
945,801 Warren, et al METHOD OF DYNAMICALLY MONITORING THE
ORIENTATION OF A CURVE DRILLING ASSEMBLY
The present invention relates to methods for rotationally orientating a downhole tool and, more partic-ularly, but not by way of limitation, the invention relates to rotationally orienting such a downhole tool during directional drilling. The present invention fur-ther relates to methods for dynamically monitoring the rotational orientation of a downhole curve drilling assem=
bly for drilling curved boreholes and, more particularly, to dynamically monitoring the rotational orientation of a reference location on the drillstring a plurality of times during each rotation of the drillstring. This application is a Continuation in Part of Application U.S. Serial No.
592,433 filed October 4, 1990.
In order to enhance the recovery of subterranean fluids, such as oil and gas, it is sometimes desirable to drill a borehole at an angle to a vertical borehole. For example, in an oil producing formation which has little vertical depth and relatively greater horizontal extent with respect to the surface of the earth, a borehole which extends horizontally through the oil producing formation can produce more oil than one extending vertically through the formation.
In order to directionally drill a borehole hor-izontally, or at any selected angle, it is necessary to be able to steer the rotating drill bit. Numerous devices have been patented for this task. U.S. Patent No. 4,699,224 (Burton) issued October 13, 1987, discloses one such apparatus and method which uses a flexible drillstring connected by a flexible joint to a drill bit collar equipped with a stabilizer and rotary drilling bit.
An eccentric cylindrical collar is connected circumferen-tially at the downhole end of the flexible drillstring over the flexible joint leading to the drill bit collar.
The presence of the eccentric collar forces the drillstr-ing to one side of the wellbore, thus lever arming the drill bit to the other side of the wellbore by virtue of pivoting on the stabilizer mounted to the drill bit collar between the flexible joint and the drill bit. Thus the drill bit's trajectory can be altered or steered.
,A borehole engaging mechanism is mounted to the outside surface of the thicker wall of the eccentric collar and digs into the borehole wall to prevent clock-wise rotation of the eccentric collar. When the drillstr-ing is rotated clockwise, it rotates freely within the eccentric collar; but when it is rotated counterclockwise, a spring-biased latch mechanism latches the eccentric collar to the drillstring and causes the eccentric collar to rotate with the drillstring. This allows the eccentric ,3 ..i ~,".':3.~. ~.C'~.i.' '~.rp ~..7'..'a,. '~."ViW."~.;.~.~~~~~~~ ~;Y ,t..
~.~i.3x.' ~.~d-'.°::.Y..r~~..i~ ~b.~ .:~.~ ~.~'~.:.i~5'.'w.'"'.:'~..
~..':...t ~5:,~~;.~:
~"'3n~"r~~'3.~.~.~ .
,"~.s'c'"3A~~'E~:~. 'S;;!'3 '~7:'.'cr~..~,?s;??'3.~:: ~.'.~'3a':?
.~:~i~.v:%3,:.;~'".~'.::~..~_ ~C:'.",:4:?'if.',~;3.E:'. <Y.'~~,~~~..",.' ~'~.":'3't~
'~ '~:ai~c~°::i.'~?~~ Yfa:~.v~"x ~zA~ r~.°...~.:'~
~,~.a'~'y~.,C~ "'~'°~.~.'~.~zfi~ r;~'~:.~s~_~.~.~ ?~$:
~:~:~:v'~.:.~i,.::ft~.
;$.~.;.~3. ~<;.~35~x:.~.'3~~.~.1~ 'w~.~'lt~~'~v~,Gl3, ~'3~~c i~fj~i~~#~f~ A~
~'~:'s.Cl:'a"sl~fe' :~Li~~,s :,.~
Cs'~"A . ~. 5. '.~ ~."~.r~ f ',f,; #~ i c?.~ ~c'. .'3 "~" s~ ~ c~ ~~!' '~ ,s f' L': f 1 ~ ."'~'.'..1' ; 'c~: ~'~. ~ v: ?'.~. i~ Y ",' ;a .::7'u' ~.. :.
.:.'~ i ~~' ;. ~~
x :.. a ~ s, n s r ~ ~,.. . r .
:. e'~ ss°.f":i.'3.: 40 . '~r, ~~>.., , ~~~~ ~ i~j..Y't ~. ~ Y: .~ ~~
i. r:3,~, w. <;i';i'l~'c-3%~
?,~t.'''.>~~~~,'"w'~..'rf':'e;j s'Y e:~,~..i.~:~':.G~,~. ~.~5".S.f~ i"'~.,f~.
v~.~.f:.~~.'"i "~.~">:~ ti'~~i,~~. ~~~'M '~~,.'~S.o'~~ti. it~~.'''.',.~~.5.
s."ii,~'~
~-.~.?~c.~~.:~>s~::~ '~.~~ E~a~v~~.'z ~.,a~;?~ ~:t: ;~~~;~~w'V:.sva ~
~,~z'~~;~az°~:
~:?'.~ ~, :w "c..-' w3 ~" 4 ~ t'~ i 3.c''~ 'E. 'Tffi?': c~'."'.h : c~ ~i ~;'Y' :~~ tE:" w~ ~' ~ ~.. ~: ~'i,;,.~ ~,"~ ~ 3.~',c ~ ~ 3.~ c3 ::f..'~. e'~ .'~, ..
~' ;~~',~,."
~.7 ~;~"~:~a~.~~,c~~.~.'s~y t:,'A-2.!?~'~:4,~C~ r"~';: ~~
~~.33:'E'':3'::~.~'.,~"',~~?'.;r. yw.'r.'.':i.XL'~.': .'.'.F' r.'3.
s:.'r'f~..~.r'~3."
~x ~;' C'~ c? ~ .;. F~ f ".'~~ 'w L°: ~'3 '': z.3 :~ .~.. . '~:.'~'3,~
~~ ~ t~3~ a"k ~. ~ ~;. w'~ :;~. ~ ~i ~#. t.". ~ .'#. ~ '~a ~ ?~C~ 'C :~ ~..

3.'3.t:~":. ~"
~'~~.,f' ~fw~~',f~ w':'.'r.'~..~~~~.~:~~.'~.i ~"~. C).3. i.".~?w' c~.'.':f°s'Ni:.i.'s~~..'".',~.'w. ~:s.~.~..'~..C~r.i." ::if.i ~;,~.s~~:
'~..'~~.~
'f; :~, :~ .'~ Ci ~" 3. t's ~'~'. z~ v ;~, <?~~. ~'a ~~.~ ~ ~.' .~"~"'.,. "~ ~
L." %~'.':3 <~ ?w '.~. O :; 8t'~:, ~. ~:3 F:;. t? ~ ~. ~~. y.~.t e~ .~_ i ; yi t~ ~' C~ Sx~..5. ~.~.~,~~I.i..~.~' ~a'~.~.:.~~~-C'5.~~~.flA:: ~v ~f.'~~".~.i'.;~S.~S,Y'.'',: r '<J'.C.t..~a3 ~~M: flA.~~ ~.ds.~'~t.'~.~.erii';.
.5..~.~.~,~fh e~~~?."'~.W'~.'~w i~.l"'~ i:'~~t~I3~'~::,t. G~, ~~"'~;.~.:v0~'w.L.
~:~;.~:"'~J~'~r,a,l'3,~F, a:3 :3~Tw ~~:a~t~~~t 'w~~ vAA~~~f:. ~''~:~ ~:'~tc~~. ~~.~ ~~.:~.~.'~~.~ h~: r:<~~
~:~~~:~ .~:va,aa ~.f: ~:~:.~ '~::~.t~..~=~ ~.~.~~ f.z~'i~~.~.~~.~.~i..t~cs :~.~ ~'3.~~-x Mrz~:~
~~.~ ~r...'.~~3.r~~~.
c''s:~~~~,'~: ~:.'~'"3~ '~~.'~'~''~~ 1.~ w'r:':c;<5w'c~aw::~,, %z 's.°c~~~'~~~~~,3-3,e,:E: .~Z.r.~>.'::c:°w1;3'i3. s;-e3'~,e~'~.°e.".
G'w.~'3. .~~ ~:?°'.'s'4:;s:3::;:i.'s,n~'3,t°'_'.f~ xi°' 't;,e: s"',~3~',~:~<~~::F: ::;I'1 '~;.'~~~: f.'.~'a'#."'1 ...~.
~''i:':"~.~..,.~, !.>~,' 3;'~3'~~~"syy 's,.:Y'.i...~,~.,w~'. 's::f.: t F:~c ': i~..~~r:C'.' ~:.~'~kC'.
."~.i"4".'~,3I. i...l.C'.tI'3 f'i~: as.".bsC': ~ai.~''a.~'..' ~_,=ssfJ'we.
.".. ':; ~..,.

2052~9~
and thus the latch mechanism. Since the rotational orien-tation of the collar recess with respect to the eccentric-ity is known, the rotational orientation of the eccentric collar with respect to the drillstring is known, and thus the reference location on the drillstring can be observed to indicate the direction that the bit is being steered.
After a period of drilling (clockwise rotation), drilling can be interrupted and the drillstring can be raised slightly and rotated counterclockwise to observe a pressure decrease when the orifice in the collar and the orifice in the drillstring are aligned, i.e., when the latch is radially coincident with the recess. Since the latch is then aligned with the recess in the eccentric collar, the orientation of the reference location at the surface can be interpreted to determine if the rotational orientation of the eccentric collar in the borehole has changed during the previous drilling period. Generally, the orientation is observed while rotating both clockwise and counterclockwise to account for twist in the drillstr-ing.
Prior to the present invention, determination of the orientation of the collar required that drilling be interrupted every three to eight minutes. The inter-ruptions are required to raise the drillstring, rotate the drillstring counterclockwise, observe the pressure pulse when the latch assembly opens, and determine whether the eccentric collar needs to be reoriented. These inter-ruptions last for about three to eight minutes each and are unnecessary if it is found that no eccentric collar ~o~~~~~
reorientation is needed. In some cases, the verification process itself may disturb the orientation of the eccen-tric collar. Additionally, if it found that the collar has moved, the amount of drilling that has occurred at unknown orientations and angles since the last verifica-tion of the proper positioning of the collar cannot be determined.
Winters et al. '925 discloses that the collar orienting apparatus may also serve as a collar orientation sensor. The point at which the valve opens and causes fluid pressure decrease during the orientation procedure is indicative of the collar position prior to readjust-ment. A clear indication of whether and to what extent the collar has moved during drilling is thus provided.
The valve is in effect a form of measurement while drill-ing wherein the latch means functions as the sensor which detects collar orientation, the valve serves as a pulsor, and the pressure gauge or pressure sensor which senses fluid pressure in the conduit coupled with visual observa-tion and interpretation of a reference mark on the drillstring at the surface provides a signal decoding function.
By this, the inventors of Winters et al. '925 meant that once drilling has been interrupted and the drillstring is raised slightly and rotated counterclock-wise to allow the latch to engage the collar, the signal generated to indicate that the latch has engaged the collar, coupled with visual observation and interpretation of a reference mark on the drillstring, can be used to 10~2G~1 determine how far the drillstring must be rotated to return the collar to its original orientation.
While Winters et al. '925 provides an advanta-geous technique for monitoring the orientation of a down-s hole curve drilling assembly for drilling curved boreholes, it is desirable to provide a technique for mon-itoring the orientation of a downhole curve drilling assembly for drilling curved boreholes without period-ically interrupting drilling, raising the drillstring, and rotating the drillstring counterclockwise.
The general object of the present invention is to provide a method for rotationally orientating a down-hole tool on a conduit, such as a curve drilling assembly for drilling curved boreholes on a drillstring, during a process involving continuous rotation of the conduit, such as drilling. A more specific object of the present invention is to provide a method for dynamically monitor-ing the rotational orientation of a curve drilling assem-bly for drilling curved boreholes, such as an eccentric collar on a drillstring. Further objects of the present invention shall appear hereinafter.
The objects of the present invention can be obtained by a method for dynamically monitoring the rota-tional orientation of a downhole tool on a rotatable con-duit comprising the steps: establishing an initial rotational orientation of a downhole tool with respect to a reference point on a rotatable conduit; generating a signal when the rotating conduit is in a defined rota-tional orientation with respect to the downhole tool _6-2(15~69~.
during drilling; and monitoring the rotational orientation of the rotating conduit at which the signal occurs.
In somewhat greater detail, the objects of the present invention can be obtained by a method for dynam-ically monitoring the rotational orientation of a downhole tool on a rotatable conduit, comprising the steps: estab-lishing an initial rotational orientation of a reference location on the downhole tool with respect to the conduit;
flowing fluid, such as drilling mud, through the conduit;
changing the size of the fluid flow path through the con-duit when the conduit is in a defined rotational orien-tation with respect to the downhole tool; sensing the response of the flowing fluid to the change in size in the fluid flow path to generate a signal; providing at least one reference location on the conduit; generating a refer-ence signal when. the at least one reference location rotates past a detector; recording the signals generated, preferably, each time the rotating conduit rotates through the defined rotational orientation with respect to the downhole tool; and monitoring the angular displacement between the reference signals and the signal in order to monitor the rotational orientation of the downhole tool.
The method of the present invention requires generation of a signal (orientation signal or collar signal) to indicate when a downhole reference location (reference mark or reference point) on the rotating drillstring is in a defined orientation relative to the eccentric collar. A second signal, referred to as the reference signal (conduit signal or surface signal) is generated at .Least once per rotation of the drillstring, for determining the orientation of an uphole reference location that rotates with the drillstring with respect to a stationary reference at the time the orientation signal is generated. Knowing the initial relationship between the downhole and uphole reference locations, the orien-tation of the collar is monitored by monitoring the orien-tation of the uphole reference location when the orientation signal is generated.
The orientation signal is generated by causing a decrease in fluid pressure within the drillstring when the drillstring is in the defined orientation relative to the eccentric collar and detecting the fluid pressure decrease at the surface by a conventional fluid pressure detection means, such as a pressure gauge or pressure sensor.
The reference signal is generated by providing an uphole reference point, such as ferromagnetic material, and a signal detector, such as a magnetic detector, at a stationary location such that the reference point will rotate past the signal detector as the drillstring rotates. The reference point can be a single reference point or multiple reference points for generating multiple reference signals. Detection of multiple reference sig-nals is desirable when the rotational speed of the drillstring is not constant.
The signal occurrences can be recorded by a con-ventional means, such as on chart paper, or can be detected by electronic equipment and recorded in computer memory.
_g_ ~o~~o~~
By monitoring these signal occurrences, and thus the orientation of the collar, without interrupting rota-tion of the dri.llstring, interruption of drilling can be avoided until it is determined that the collar needs to be reoriented. If desired, an alarm system can be used to alert operators to changes in collar orientation beyond allowable limits and need for reorientation of the collar.
Essential elements of the present invention are the orientation signal, means for monitoring orientation of an uphole reference location that rotates with the drillstring, and means for accounting for twist in the drillstring. The azimuthal orientation of the uphole ref-erence at the time of alignment of the orifices is deter-mined, and twist in the drillstring is used for determining the orientation of the collar.
In one embodiment, the objects of the present invention can be attained by a method of dynamically moni-toying the downhole rotational orientation of a curve drilling assembly on a rotatable drillstring, the method comprising the steps: generating a pressure signal when the drillstring is in a defined rotational orientation relative to the curve drilling assembly during drilling;
generating at least one reference signal for monitoring the rotational orientation of the drillstring at which the pressure signal occurs; and comparing the pressure signal and the at least one reference signal for dynamically mon-itoring the rotational orientation of the curve drilling assembly.
_g_ 20526~~1 The orientation signal is generated by changing the geometry of the fluid flow path through a conduit when the conduit is in the defined rotational orientation with respect to a downhole tool; flowing fluid through the con-s duit; and sensing the response of the flowing fluid to the change in geometry of the fluid flow path to generate the signal. More specifically, the orientation signal is gen-crated by pumping fluid through the conduit; changing the size of the fluid flow path through the conduit when the conduit is in the defined rotational orientation with respect to the tool in order to create a pressure change in the flowing fluid and initiate signal; recording a pressure profile of the pumped fluid when the conduit is not rotating; recording a pressure profile of the pumped 1S fluid when the conduit is rotating; and comparing the pressure profiles to generate the signals.
In one embodiment, the rotational orientation of the rotating conduit at which the orientation signal occurs is monitored by providing a reference point on the conduit; providing a stationary detector at a known orien-tation for a conduit reference point; determining the angular displacement of the reference point relative to the initial rotational orientation of the tool and con-duit, at which orientation the orientation signal is gen-2S crated; and monitoring the angular displacement as the conduit rotates in order to monitor the rotational orien-tation of the tool. More specifically, in this embod-invent, a reference signal is generated preferably at least each time the reference point and conduit complete 360° of zo~2sm rot.atlon; and the angular displacement between the refer-ence signal and the signal is monitored in order to moni-for the rotational orientation of the tool.
The present invention is better understood by reference to the following drawings;
Figure 1 is a partially sectioned side view of an embodiment of a downhole tool connected on a rotatable conduit utilized in the method of the present invention.
Figure 2 is a view taken along line 2-2 of Figure 1.
Figure 3 is a plot of fluid pressure versus time, of drilling fluid being pumped through a drillstring when the drillstring is not rotating and the orifice in the drillstring and the orifice in the tool are not aligned.
Figure 4 plots pumped drilling fluid pressure versus time when the drillstring is rotating and when the drillstring includes an embodiment of a tool orienting apparatus utilized in the method of the present invention.
Figure 5 is an overlay of Figure 3 on Figure 4.
Figure 6 illustrates an embodiment of the signal of the present invention obtained by subtracting Figure 3 from Figure 4.
Figure 7 is an illustration of the delay of the signal with respect to the rotary timing mark at rota-tional speeds of 15, 30, and 60 rpm.
Figure 8 is a plot of the angular position of the signal with respect to a reference point at rotational speeds of 15, 30, and 60 rpm.

Figure 9 is a partially sectioned side view of an embodiment of a downhole tool connected to a rotatable conduit utilized in the method o.f the present invention.
Briefly, the objects of the present invention S can be attained by a method for dynamically monitoring the rotational orientation of a downhole tool on a rotatable conduit, comprising the steps: establishing an initial rotational orientation of a downhole tool with respect to a reference point on a rotatable conduit; rotating the conduit and generating a signal when the rotating conduit is in a defined rotational orientation with respect to the downhole tool; and monitoring the rotational orientation of the rotating conduit when the signal occurs.
In somewhat greater detail, the objects of the present invention can be attained by a method for dynam-ically monitoring the rotational orientation of a downhole tool on a rotatable conduit, comprising the steps: estab-lishing an initial rotational orientation of a reference location on the downhole tool with respect to the conduit;
flowing fluid 'through the conduit; changing the size of the fluid flow path through the conduit when the conduit is in a defined rotational orientation with respect to the downhole tool; sensing the response of the flowing fluid to the change in size in the fluid flow path to generate a signal; providing at least one reference location on the conduit; generating a reference signal when the at least one reference location rotates past the detector; record-ing the signal generated when the rotating conduit rotates through the defined rotational orientation with respect to the downhple tool; and monitoring the angular displacement between the reference signal and the signal in order to monitor the rotational orientation of the downhole tool.
Figures 1-2 represent embodiments of downhole tools used in the method of determining the rotational orientation of a downhole tool on a rotatable conduit 22, such as a drillstring, As exemplified in Figure 1, in the preferred embodiment, the downhole ... , tool, such as a collar 20, is connected to the drillstring in the borehole 24 of an oil or gas well, although it is intended to be understood that the method can be used to rotationally orient virtually any type of tool or collar on any type of rotatable conduit in virtu-ally any type of environment, e.g., water wells, steam wells, underwater conduits or pipes, surface installations of conduit, etc.
Referring to the example of Figure 1, the method of the present invention can be generally described as including establishing the initial orientation of a con-duit 22 reference location, having a defined rotational orientation relative to the collar 20, to a conduit 22 surface reference location; generating a signal 26 (best exemplified in Figures 5-6) when the conduit 22 is in the defined rotational orientation with respect to the collar 20; monitoring rotational orientation of the rotat-ing conduit 22 at which the signal 26 occurs; and calcu-lating the orientation of the collar 20 with respect to true north. By rotational orientation is meant the angu-lar displacement of a surface reference location on the collar 20 or conduit 22 with respect to a reference point which does not rotate with the collar 20 or conduit 22, such as a reference point on the earth which is at a known direction with respect to true north.
In one embodiment, the signal 26 is generated by changing the size or structural characteristics of the fluid flow path through the conduit 22 when the conduit 22 is in the defined rotational orientation with respect to the collar 20 and sensing the response of the flowing fluid to the change in size or characteristics of the fluid flow path to generate the signal 26. The signal 26 can then be provided by sensing the changes in the flow or pressure of the fluid in the conduit 22. Commercially available flow or pressure sensing devices or transmitters (not illustrated) can be used to sense and transmit the flow or pressure changes, as is well known in the art. In this embodiment, the signal 26'is provided by changing the fluid pressure in the conduit 22 and, more specifically, is provided by decreasing the fluid pressure in the con-duit 22 and sensing the fluid pressure decrease, as fur-they discussed below.
In samewhat greater detail, referring to the example illustrated in Figure 2, the signal 26 is created by providing an orifice 34 through the wall of the conduit 22, providing an orifice 35 through the collar 20, pumping fluids through the conduit 22 and discharging fluid through orifice 34 and orifice 35 when the conduit 22 is in a defined rotational orientation with 2~~2691 respect to the collar 20 to create a pressure decrease in the flowing fluid and thereby to generate a signal.
The orifices 34 and 35 of the apparatus of the present invention are preferably configured to provide a signal 26 which is detectable at the surface. For exam ple, the orifices can be round. When the orifice 34 through the wall of the conduit 22 is round, orifice 35 through the collar 20 can be an elongated slot for strengthening or increasing the duration of signal 26. In one embodiment, the orifices 34 and 35 are square for pro-viding a sharper or more distinct signal.
In one embodiment, the signal 26 is generated using an orienting or signaling apparatus 32 which includes an orifice 34 through the wall of the conduit 22 and an orifice 35 through the wall of the collar 20. The collar 20 and conduit 22 are rotatable relative to one another about the longitudinal axis 38 of the conduit 22.
The latch 36 is used for latching the collar 20 to the conduit 22, when orifices 34 and 35 are aligned, and rotating the collar 20 when the conduit 22 is rotated in the first direction ("orienting") about the longitudinal axis 38 of the conduit 22. Conversely, the latch 36 is used for unlatching the collar 20 from the conduit 22 and allowing the conduit 22 to rotate relative to the collar 20 when the conduit 22 is .rotated in a second oppo-site direction ("drilling") about the longitudinal axis 38 of the conduit 22. For most purposes, the first "orient-ing" direction is counterclockwise and the second "drill-ing" direction is clockwise.

' ~ CA 02052691 2004-04-22 ) The collar orienting or signalling apparatus 32 is coaxially and rotatably mounted on the outside surface 42 of the conduit 22 with the fluid flowing within the inside sur-face 44 of the conduit 22. Further, the collar 20 has an outside surface 46 and an inside surface 48 with an eccen-tric collar, i.e., the collar 20 is a cylindrical sleeve with a cylindrical hole passing longitudinally thereth-rough with the axis of the hole being intentionally dis-placed to one side of the central axis of the collar 20.
The resulting offset creates a relatively thick wall 50 on one side of the collar 20 and a relatively thin wall 52 on the other, opposite side of the collar 20. A borehole engaging mechanism 54 is mounted on the outside surface 46 of the thick wall 50 of the collar 20 and the latch 36 latches to the inside surface 48 of the thick wall 50 of the collar 20, opposite the borehole engaging mechanism.
Referring to the example illustrated in Figure 2, the collar orienting or signalling apparatus 32 includes a recess 60 in the inside surface 48 of the collar 20. The recess 60 and the latch 36 are radially coincident with respect to the longitudinal axis of the conduit 22 at least once during each rotation of the conduit 22 relative to the collar 20. Being radially coincident means that the recess 60 arid the latch 36 coincide on the same radius extending from the longitudinal axis 38. In one embod-invent, the latch 36 and recess 60 also rotate in the same radial plane with respect to the longitudinal axis 38.
As exemplified in Figure 2, the collar includes a sealing surface for sealing orifice 34 when a fJ~~.s~~wL.rw 'w~ Ys:x~~ fJri'~.~M','z,: Jw ..F ~ ".f3ø. Ar~:~.~.~..4~
'.'.iJ'~.~';~"i. ~~.~' ~:. ....
..
~"''~.,~.';~x ~~3.~~.;'~ ~~' ~ ~~'~'is~:?'?. ~":~:.?'a !~~'"3~3C~~k.'s: s;~
:~.: .I3, '~zf. s;~,.:~.~::3,'3,'::'C~, ;::'f~ . e't'~
'~: ~.~~~I~.~~_ ~i;.._F.~~f:r"'3..'<:.'3I~. ~u:~.'~:i3. '3."~r.~~%;.'.x~i.;;;
''~::; 'st.".:,a? ;';G~ .'.% s:' ~~i, ~~S'..:!>
3 r_i ø. t,a's ~.5'.w c. ,''<~ ~. ~' t:', ~-?, F;~ 'c"~ "',,'t sr'~ .; ~' 4,~
L"s~.:.~ '~. . ~.. y% ,~-~ ~3 ~C ~'3 <" :~.:."~, ~'~: 'i:: :, :~.; '.t: ~s~.~
rk''.',.'.
fr'.~.'.'G,~.:.~'...E..:l~: .~.~t.'''.~.~.~ fJ','~..'.~.lr..,-,i...i:°,v:3 ~'.i,~.'Y"'' ~'c~:~>~'.,:: ,~.'~.f~.~.f'~~:.._~_ ~
L:v.:~..~.~<:.~_:~~~::f.~., ir,~~;,;~? ~~ 'C;: ~ 1 ~;:: ~,. ::~ ~:.' r': ~I ~.~~ ~y ~. ~'if.~t :. ~: :::
4~a ii u; t~,k %~ '~." ~ :.!; f~ ..~':E ' : i ; F? fas. ~ ~: . '~ : ~.~.,t ;~;' ~w ".; x's : ~, <?~3,c'~ ~. ~J ~,' .i, c~,'?~3, ~~ cW:, i, ~~'.il~:.
i's.~i ;;'E ~3, :.3 ~~. '#" ;~ t'~ . ~ .~...~_'~; :: ~."t . ~ z e: :~.';E s?x i~: , 'fi: ~~, ~~~::i~.<:%:~ >°tF~S;'''srt~,r.:l? ~~~ 3,'~ '~:,<:'s,~;:
!,f'.;~.~.Y:.'.' ~H~.,~.~ ~~.'G~;~;%c:w:'t,:.3.vc:~,zy' 'M;~..''.z%<.i.~~
v'~~~~a Z'? ;.~ ~. ~: ". ~:; ~ ~ ~~: , '.~.~'a c? .~. ~?. ~ ~:".:.~~: , fs r E5:" ~, ~' .'~. E:: ~ ~' i ~~ , r; ' ~, :: ~, t~; ~~. ~ ~ >:3, 3~:.C~
::~.d :~:'~:~'."~'~.ns4: . S,;,t i~'~~~ C"~.4~v".r:F~:~"a. C:!i i.<'~~.'i.'~
'~:;:.>:''. ~'1::."'~..~c.~:~.;~'e~ 'i~~. ~;~ix '".33". Fr'~..':;F' wi.~ c~N'~a ~~~.~tw?~';'4'ar.~, c~i3~ ~:.':~,~"1~..' ~~~~i'~
~."t.>A,:Cs~.:~~.°: ~.'. .F.1=Y x~'~ '~:~;::~~.~:"..~'i:a'~
~,':.~ '.'~",.~~, v.~.'.~,.y~~.".:~.~ ~;:,' .i~:.':~i,s'rxh.'i. L..'s.ii~:: ~
~.~..~i.~~S. r'E;Y~.i.~..~~~.a'~' '~' t.~'i.: '~:i.~: w~~i S...y..G:~:. fl ;
~~'fc':3H?:3,~,F;~,~<:i t;?~~ SS~~'::~.G'z:: f.~'<.;",'e':w:~'.:3.sws~~
v'~'~<'s? %...t..,;".;~~~:~.~:'; ~! ~.~i .':'!?i::;~": ~,;.''~, ~.r..E: ".ai:.?C~~,.:~'<'; ~ ~ ~ ; ~'.~~Mi a :,,~.t.;;' ~,'~~ii::
G°i:3~~~~.i~#,:~. ~:. ~M~ N'~.r°...sv:'i:a.?::i .<$ i:F;; Vii':' ~s '~:~3,"~iiiz~='% ~:~3,?a '.:i~''sfi' ~ s~E'~:i 'M'fJ i~c3''s~ ::::~~~~'.~,' ~~.. i:'~.'f.' ~ w'~:3';w:z''<°: a.C?~~ ,, ~;~3.E:S ?:,E,'~'::3 ~: ~. ~. iz~~~z ~'.'-%, 'w3 $' w :~ 3, f::'~~': <i ,Z ~ .;'~:: f.~ .:i '~~ >v ;I, ,F. ~ vl .~. 3 !.i cax '~ ~. a ~.F. ~:~ J s"3. 'r~-" :~ w :~ %v.' ~;'s"?:.'s3 ~,E' c~v ~5'i."'c,.''',~'.''s'.~~?~'cfyt 3.~3:.~~,l;."Y' F:k~::
a.~.i~zk:.3M ~ur.~,'' , '~~ ~:i~~."~r,'~'kE~~ø:' ~'..~.~::~'::~%::L'?.~.?i::I_'?~1 w'f..,'~ ~%.~~'~'.;3%:X~;~'~.~.3~~.~:.r~~.scc'~:~~,$.:a CJa '%::;3,i~>
~:'~~;'"'~c'.''~"~::',''~,.'~~ '.::t::.'~,~.w~.' CJ'~,".::~:~.3.'i,:..i3:~' F'~.~~c"~~ ~':ifr:3#,N,'. .:SG w.~,~'3s.E ~s'1~>j"~~f?E:~'', L;~'3.~3, ~:':4~?
i~:.3E..i~IC~. ~.~'1 fif ~.~'1~::~:'ir ~:':. ,.~~..~. , ~:':~.~i~:..''.'.~~.Y~~.. ~_'.':~~, %~, 'kr.""{i~ ~t ; ,.
Y.
Y
..~..c~'' ess.3.!~~ s~""3. ~~?ti~.~.~i3~ i.~': "~::;;.?'a ~ ..ras.Fc''..k, ~s :.3f 's3~':3;'%E~~.:~:E:~, ss~~;~:3:~~'3,ry~;:;8.rae~:>.~5.:,t'~,:'~~'f~F.~: ~~~~:3_#,a.C'~
's:'~..':~'t.>~.~s,~~ss": ~S.".;';.~x. r'c333!'~?:~.'f. ::'.;:, ~k"Et".;, W-.~'w.ww~~-:~~~? r.,>::<~.~.'~:~' ~.~~:~:~:~~.~:.ws~i~
G~'~:.~:,~~.~.':~'~;~.~~'~s:~; ,~~~.z'~'~~v.w.~'~ ~.
".t'r .e'i?c::?E.~,::"~.~,'~; ~,'S'"!%:'s:.'F..~S..~'!-.? t:~','."
~::~"ra~;~:'?:~; X3,3.>'.,''.~,~.fJ~ ~~ c~ zi'.;,c~:,;« ,'S~~f?~,": S.W3 'sz ~~s ;;~.~.~f~y~'~ ::,~,r~~3,~ ~::'u ~ sw i' ~ ,.s~- '~:~z~: i.i~;~'~zx ~ ~.?x .s'.~ 3v~:.~:::~: ~.'.~~s.w: r c~?'~C~;:.'~. : ,':;7 ~. ~- ~3.::3'~ ~;' e's s:: c3,'~. ;;. f ~ ~~ , s:~ 'Y~, ;:,r >w' ~' ~.:H ~, ~S: i ~.:.3 ~'~ .'#. <'~. '~:~~'3. s.'''.. :~.:~"'; , s'~.?"3!~ s'~.> ~
>:.~:..'~F: -°
~.f...'5.~~.:.~::~ :.~. ~.y3.i~.~~.d.~'~..~ ~~.'f .~.'ri'":v.k~f'f.~":.,~5~~
CY. ~n''..'y,i:'2~;~',.'Sa'~"~.~.;~.~t~'.'~"''. ~m...ri."~'~...'~..C: ~~' '~.~
'~s~:z,3,~~~'~.'sru':~, ~~ ~.~;_3''::C,~S ~4?'A~'~? f:i'3~.' ~:a'~'?!".~;~.''c~. ;~.:; '.'.i''~."'T~ ::E.a.~ ,, '.; rr.;:'.F~::3i:;.'s..
~..i '.~::>:~5.
r I A ~ Y: 's 'S ' z y~ Y~:S ~~ ~ r:a 'S Ia ~ ...
'#~'E -:~.'.:~:'~: . , ~.<.;::ys. f','Cy~Y,i~ sh "",'s,'3,r; ~:~'ir' ~> rwc. .
~~'EN ~~.~'~..~~, ~.,.. ~~:F~'s s;~..Lc."~;
.u ''~. "~ .f, CA 02052691 2004-04-22 i ate the collar signal 26, as illustrated in Figures 5 and 6.
Figure 3 is a recording of the fluid pressure versus time when the pump is operating and the drillstring '5 is not rotating. Figure 4 shows a recording of the fluid pressure in drillstring versus time while drilling with the drillstring rotating at 59 revolutions per minute (rpm). The predominant pressure variations on Figure 4 are the pressure fluctuations caused by the cyclic motion of the plungers and valves in the pump used for the test.
Figures 3 and 4 appear to be very similar until the Figures are overlaid, as illustrated in Figure 5, and the divergences identified. Since the divergences iden-tify the signal 26, the divergences are indicated by ref-erence number 26 on Figure 5.
The pump profiles of Figures 3 and 4 can also be subtracted, as is well known in the art, to make the signal 26 more evident as exemplified in Figure 6. The three collar signals 26 identified in Figure 6 correspond to the signals 26 on Figure 5. A pump timing signal, i.e., a signal generated at the same point in each cycle of the pump, can be used to facilitate placing the two pressure profiles in phase before they are subtracted.
The detection of the signal 26 can be determined from a simple trigger level (magnitude of the difference in the two profiles) above the baseline difference or the differ-ence signal can be differentiated to provide a more dis-tinct inflection point for detection, i.e., to exaggerate the slope or rate of change and the difference between the pressure profiles. When a collar signal is detected, it can be integrated and compared to the integral of the expected collar signal in order to help identify faulty signals. This differentiation and integration of the sig-nals are examples of well known techniques which can be used for identifying the signal 26 in its "noisy" environ-ment. Other techniques for identifying the signal 26 are readily apparent in view of the disclosure contained herein.
If a computer is used to implement the method of the present invention, it may be desirable to record and average the fluid pressure over several cycles of the pump while the drillstring is not rotating to obtain a more accurate pump signature. It may also be desirable to use the computer to proportionately expand or contract the measured pump profile (along either axis) in order to eliminate potential mismatches caused by slight variations in either the pump cycle and/or fluid pressure fluctu-ations in the drillstring.
Referring to Figure 1, in one embodiment, the rotational orientation of the rotating conduit 22 at which the collar signal 26 occurs is monitored by providing a reference point 72 on the conduit 22; determining the angular displacement 74 (best seen in Figure 6) of the reference point 72 relative to the initial rotational ori-entation of the collar 20 and conduit at which the signal 26 is generated; and monitoring or measuring the angular displacement of the reference point 72 relative to the.
initial rotational orientation of the collar 20 and con-duit 22, i.e., monitoring the angular displacement of the reference point 72. with respect to the signal 26 as the conduit 22 rotates in order to monitor the rotational ori-entation of the collar 20.
More specifically, the rotational orientation of the rotating conduit 22 at which the signal 26 occurs is monitored by generating a reference signal 76 each time the reference point 72 and conduit 22 complete 360° of rotation; generating a signal 26 each time the rotating conduit 22 is in the defined rotational orientation with respect to the collar 20; and monitoring the angular dis-placement 74 between the reference signal 76 and the signal 26, as exemplified in Figure 6, to monitor or meas-ure the rotational orientation of the collar 20.
Referring to the example of Figure 6, the time between reference signals 76 corresponds to 360,° of rota-tion of the conduit 22 and a signal 26 should occur with every 360° of rotation; the time or angular displacement between the signal 26 and the reference signal 76 should remain the same unless the rotational orientation of the collar 20 with respect to the borehole 24 has changed.
Therefore, the time between the reference signal 76 and the signal 26 can be used to calculate the angular dis-placement 74 of the eccentric collar 20 (since the posi-tion of the eccentric collar 20 relative to the recess 60 in collar 20 is known) relative to the reference point 72 and thereby to monitor any changes in the position of the eccentric collar 20 with respect to the borehole 24.
These calculations are dependant on the assumption that the drillstring rotates at a constant rate. As explained below, this assumption does not always hold for drillstr-ings over 1,000 ft long and additional signals must be generated to account for same.
The operation of the method of dynamically moni-toying the rotational orientation of a downhole tool on a rotatable conduit, such as an eccentric collar 20 on a drillstring in a borehole 24, will now be described in more detail. First, an initial relationship between rota-tional orientation of the latch 36 and a reference point, such as the mule shoe sub, near the bottom of the drillstring is established while tripping the drillstr-ing into the borehole.
If flexible collars having an asymmetrical cut are being used, this reference point is established with the flexible collars laid out horizontally and undergoing a clockwise torsional loading. A top mark is made at the top of each torsionally flexible section with a bubble level centering punch and a bottom mark is made at the bottom of each torsionally flexible section while applying a clockwise torque to the top of the section and holding the bottom stationary. The top mark and bottom mark are in line with the axis of the collar 20 when it is in the drilling configuration. When the curve assembly is tripped into the borehole, location of the top mark and the bottom mark are transferred across tool joints by mea-surfing and recording the circumferential distance between the top mark on a lower torsionally flexible section and the bottom mark on an upper torsionally flexible section.

~
~ CA 02052691 2004-04-22 y A consistent sign convention is used when recording the measurements. The offset of all of the connections are summed in determining the initial offset between the latch 36 and the mule shoe sub.
The above method works well with flexible pipe having an asymmetrical cut because indications are that the punch marks remain in the same configuration when the pipe is positioned in the curved section of the borehole as when the pipe is laid out horizontally. However, when a flexible pipe have a symmetrical cut is used, present indications are that the punch marks do not remain in the same configuration when the pipe is positioned in the curved section of the borehole as when the pipe is laid out horizontally. An empirical relationship can be devel-oped for determining the orientation of a top mark rela-tive to a bottom mark once flexible pipe having a symmetrical cut is positioned in the curved section of the borehole. For example, the orientation of a top mark is observed to move 2° /ft clockwise, relative to bottom marks, when a particular flexible pipe is positioned in a 28-ft radius curve. Present indications are that use of a flex-ible pipe having a symmetrical cut rather than an asymmet-rical cut provides a less noisy environment for identifying the signal 26.
After the drillstring is tripped into the borehole, the drillstring is rotated with the bit off bottom a sufficient number of times, e.g., about six times, to allow the upper, torsionally inflexible portion of the drillstring to twist due to friction, as it will twist during drilling. Torque in the drillstring is meas-ured at the surface. This torque is the tare or zero torque for torque measurements during drilling. A conven-tional technique such as magnetic or gyroscopic surveying is used to determine the orientation of the mule shoe sub while the drillstring is twisted. From the measured mule shoe orientation and the offset determined above, a refer-ence point72 is located on the drillstring to reference the orientation of the downhole latch. Normally, the ref-erence point72 may be located on a portion of the drilling rig that rotates with the drillstring but does not change elevational position with respect to the surface of the earth as does the drillstring. For example, on a rig operating with a kelly and a rotary table, the refer-ence point 72 is located on the rotary table. On a rig operating with a power swivel, the reference point72 is located on the rotating sub below the power swivel. A
detector 78 is located at a stationary point near the sur-face reference point72 so that the detector 78 can gener-ate a distinct surface reference signal 76 when the surface reference point 72 rotates past the detector 78.
The orientation of the detector 78 from the central line of the drillstring relative to a selected azimuthal point, such as true north, is determined. In one embod-invent, the surface reference point72 is a ferromagnetic material and the detector 78 is a magnetic detector.
Once the orientation of the collar latch 36 is established relative to the mule shoe sub, and the mule shoe sub orientation relative to the surface reference ' CA 02052691 2004-04-22 point72 is established, the drillstring can be rotated counterclockwise to rotationally orient, i.e., to position the eccentric collar 20 as needed. As previously dis-cussed, when the drillstring is rotated counterclock-wise the latch 36 engages recess 60 and rotates the collar 20 with the drillstring~ Once the eccentric collar 20 is properly positioned, the drillstring can be rotated clockwise to free the latch 36 from recess 60 and commence drilling. As previously discussed, a pres-sure signal 26 is generated each time the drillstring rotates through the defined rotational orientation with respect to the collar 20, i.e., each time the latch 36 encounters recess 60, orifice 34 is aligned with orifice 35 and a pressure decrease is generated in the drilling fluid. The rotational orientation of the eccen-trio collar 20 is then monitored by timing and comparing the occurrences of reference signals 76 and the pressure signal 26. The orientation of the collar 20 with respect to true north is determined from its orientation relative to the reference point 72 and the known azimuthal orien-tation of detector 78.~
Since a finite time is required for the signal to travel from the collar 20 to the surface, the relative position of the surface reference mark must be adjusted to account for its clockwise rotation while the collar signal 26 is traveling from the collar 20 to the earth's surface.
Similarly, an adjustment must be made for wind-up or twist in the drillstring due to changes in the torsional load on the bit. If the position, or rotational orientation, of the eccentric collar 20 changes in the borehole 24, such position will also change with respect to the initial ori-entation of the reference point 72 and reference signal 76. The signals can be recorded, as exemplified in Fig-ures 4-6, to continuously monitor the rotational orien-tation of the eccentric collar 20 without interrupting rotation of the drillstring. Thus, it can be seen that the present method greatly improves drilling efficiency and borehole trajectory control by providing a more accu-rate knowledge of the rotational orientation of the eccen-tric collar 20 at all times.
The method can also be implemented using a com-puter to time and compare the occurrences of the reference signal 76 and the signal 26, and to automatically provide an update of the rotational orientation of the eccentric collar 20 with each revolution of the drillstring, or at any lesser frequency as desired. The computer is pro-grammed to provide a continuously updated history of the rotational orientation of the eccentric collar 20. This history should be monitored so that drilling can continue uninterrupted until the rotational orientation of the eccentric collar 20 has changed sufficiently to require a repositioning of the eccentric collar 20.
The above-described orientation method is based upon determining the orientation of the drillstring at the surface when a signal arrives; knowing the travel time of the signal; and knowing the magnitude of twist, measured in degrees, in the drillstring. From these inputs, the downhole orientation of the tool at the time the signal ' CA 02052691 2004-04-22 was generated can be determined. The twist can be calcu-lated from well known theoretical relationships, if the torque is known. The signal travel time can be calculated from the sonic velocity in the mud inside the drillstring.
5~ There are well-known theoretical relationships between the sonic velocity, drillstring geometry and mechanical properties, and the fluid properties. However, in some embodiments of the present invention, the drillstring is composed of many different geometries ZO (including a pliable hydraulic hose in wiggly drill col-lars) and the mud properties may not be exactly known, it would be better if the sonic velocity could be directly measured.
If the drillstring is rotated at various 15 speeds at the drilling depth, the arrival of the signal 26 will shift with respect to the surface orientation. For example, in Figure 7 the arrival of the signal 26 is shown for three different rotational speeds at the drilling depth. The orientation of the eccentric collar 20 has not 20 changed for each of these three measurements. At 15 rpm the signal arrives 2.33 sec after the surface reference mark, at 30 rpm it arrives 1.33 sec after the surface mark, and at 60,rpm it arrives 0.83 sec after the surface reference mark. If this data is plotted as shown in 25 Figure 8, both the static orientation of the tool and the delay factor for the sonic travel time can be determined, by using well known techniques.
The twist can also be directly measured at the wellsite by monitoring the shift of the surface signal 26 as the torque changes. A linear relationship between twist and torque can be determined by applying weight to the bit and simultaneously measuring the signal shift and torque. This linear' relationship can then be used to cor-rect the measured signal arrival for twist while drilling.
Implementation of a correction procedure for signal delay can be accomplished by lowering the drillstr-ing into the wellbore until the drill bit enters the top of the proposed curve; rotating the drillstring at several rotary speeds; recording the arrival of the signal at each rotary speed; calculating the best fit slope and intercept data for arrival time versus rotary speed using well known methods; and using the slope and any new measured rota-tional speed to adjust subsequent orientation signals for the sonic delay time, as shown in Figures 7 and 8.
Implementation of the correction procedure for drillstring twist can be accomplished by lowering the drillstring into the welibore until the drill bit enters the top of the proposed curve; rotating the drillstring;
applying weight to the drill bit of several different mag-nitudes; recording the arrival of the signal and the torque at each such weight; calculating the linear relationship between the torque and signal shift using well known methods; and using the linear slope and any new measured torque to adjust subsequent orientation signals for the drillstring twist, as shown in Figures 7 and 8.
As indicated above, the above-described embod-iments of the method of the present invention are based on an assumption that the rotational speed of the drillstring '%':~'3.~ l;if~:~lC3s:~t. C~,i.~.T;3.T'3,C'g' F:~»:':~,'.,~..:x#'3.f~ c":.'f'.
:'~'~~3~ w~:~;iT ;,~.F~~.~~~:A;,~, ~S.~.C''f't .~'.-.-"s.:'.-: %.'isJiS$~3 :~~ ~s~eaa~:~::-~:' ~t~.~~.rz ~~~~.~.~: .~. ~.~s~'~ ~,.., w:~~::i.~~~~ rsx~.~
:~~. ~:~cf~:.~~
.s'i f: '~'~~ L"3 F.;. is.~.C:~s. ";." t~7'~ c:~ '.". y ;:i: ~: %.: ~, :a ~;~
~a ~Zx ::; .r~. '.'.~'3.~'=: t:~:' :3. ~. ~. <;i i; L' a. ~ ~E ~ s:, i~ :";
e;; ..'~ #~ E.'. ;.; "~';
''~'.A1~: X:'3-?~:~'?.r%C'~. s'.';'~z?~:::~~. is'ct~'aw'tt:::~.:..'t~:;v i"'~e;;i ~:;3'A-:%~~ .'s."'i,~:'wu::.i~"~_!aC-~~
.~~'~'c ~." x .~ ~. ~ '~.".~: .X:tR': ct3':liA. sl~'. i~ia~'~'~3.:a.~. ~
~'~..~. ~. >~z3,CE h3~-'' ~ iE~ ~?3. ~.:.,~'s.~ s.;~ 1 'i .~. .?.
.~: ~~f~~. >,r:~5~::~::~"~s~~~~~~~ ~ ~'~~°~:~~~::~.csn. i~'~~r:~~ ~z;~' ~~.a~ ~.~x;:~. ~"rf~:,>=i-.~.?~ c~"..'~..E.y~.t'a.i_ ;,~~2::~%.~ F3~~ ~5:~~~.F?
C~?.".1..~..~.f'..'.'f,'g. u'~»l~~"' ';%z;»~.y.'~'' ~'.~.~..i,~l:'.1~~:.~~ c:.
?"f:;~'~'.:.)'3.::..w;Y: :"~)'~:
sir 3~" f '~~.'~':: ...~ ~~" ~'3 s ~,?_i~~yJ.'~;~
~~'3~c,~~.f a~' v a.~3~= '~. ~ .~' .'~.. E?.i cc :s. fh''s '.."'ib 'F' F-w' ..e ;3..~ ~f ~ ,°"":~~':~..~ FC c"~ 3s ' C'3~ "s::'s <#,'? °;:< F~~,i.~~'.L~3.t~';'.~'1~ ",',°
.t~.,~''.".:?3.'t.' ""~., f:; ~ '.:3 ~ '~-.~3,t'~ f.~.~f: ~z..~_ ~. c:.
~;,sc:".:..~''Ei;;' .
sa?'~'~'~?:'.:.'s?.f~ ~i'S M .?.t:'~~.~::.'wr-: ~ ; 's',~3, >,:;~:3~
r:';~:~.'3f'ii":..'?.~'~.'3~'~."~.: C:;.'~.'~ u~lf,".
.~. ~ r't'~.~"xis:;?'3~.; ~,3'3;r'~:~~,~::,.'w~~~, ~t~?~3."..r'~ :~.c r°3.~'~,ie~3»'...'~.~~f'~'tJ;.i~: ~~'x~'~3. '~il.~ '."o~;r''~°-'~? L:."i.'~c"~,~" ~.~,~'~,?~'.~.'~ ~i'.~C-a ~~'~'.~.w~ L.;E:':3.~F.~i 3..~
i_s.~'':. s:.~'?%'a~~':c"t~'y ~ ~~~~~'~i ~,'°°
:E.'~'..',~ f'?,?o, 3'5:;3~::f'-~.'F::'s»f'rz ~,_~'~_.~~;::~ y.i.< ''~'" r ~';'ty~ C~~k~y'~r.,~.;~y,'~"~''~<~. .~Z~7 ~~:~.r'3.i~: i.~:,~i, >.' ~, =..?- f.t.': y...,°. ~;:a'r~:::r~..,::a "?.'",:'s' .y"c' " .,~
"r.'3r..._ y ... '' l 't~t:.. -.
'~3 _:. .~ ... 5.'a....~. ':. .., ~' .". ~5' ::i~.~... ..... ~~. t" ~ ~~'t'~
.'~_. ....,.. ....".E C. ... ~.. t. .,.. '~.: f ... :'.. ~ ...3~', v.3 E. a :'~ ~ ~' ' :'. _.. 4: .'~.~'?.... ~ .°t. ""
~w Awe ~,.~' ~~Z~ s:;t's'~~:~~~:~,~. ~~~ ~'~?~" ~.~.~~r~..7.:~.~:;~ ;~~' ~'~~'~~w?v~~.4a ~:~~w. .~~5,:.'t~''t"."~'sc.i..L';..~ t~~. ~'r'?.#.:'.~'..f.'3.i~
."?,"t~~'%=,>,"."',"~;r%,.'':.' ~L:%..'3..::.,.... ~~~ ~:i ~.".:'~~:
:'";r?S'~,~%.~~."?.3.~ ~. ~
'3,~t:'7;:~''s".!?.~ , '~'%~~:? s?'r'.i-'t~.'Y'~.....~.': j'' iS.rf.
<i::~;"sfic~.''.:lr ~;~>w>wc'.''.!'=:.'i~;:;r" #;iC%:1.~',..':::a 'l;:~t %.a~''M' '~:~v,'~,:3.-_.
:~ ~'::'f"?',s.~s'~ ~~t'~w,l,?Cy s ~'i ~-' ~.Y~;'::~.~.~ r ~:?'~':~. Mt ~~~
%~7. !3i;.3.3.~~ ø.5s'3.~ t,.. x ~:; k ;~"" .
~~ ~~w ~8.'7~ ~4~~L"~w~.~~~~ ~~ v ~y~~~~~~ uTr W ~..':.:.'ii'S/ .'_.i~~~. >.
tJ.i d;"'~ "'.:e~.. ~i:a..cF~'~~:~,.~ a~.,'"'','~,~ ~' >:iEC-.''.~.,~L:''''~~t;,.?
~'';4a~.~'~'..i:'~~',.°.;E,.': ','':i~.C,g~3.~:.". ~~.~ ~'K'r:~~1 '~":°~"i~
~~i~.;~.~."s'~'..~. ".."st,"."3 f.'3~.. 's~~''~~..~':'s,':~ ,~i.".~':
i:i'~.f~'~'k~~._~_as",-a 'Z~i , ~'~~r<y.., ~:".L'.,.:.~s't9~-.~.:.~.: f !,?
1C4. ~ ~.~» .,..
,,'?"~, ~ i;; ~? »."t~"~'~. ~'~."~ ~~~"f.", rri::f'.'..i.°c' '";:. ;' ~
::~ ..4w',:,~., w.'%~' ?., ;~i,e. s~~ ~' ~'~:%3.::~'.:. ~3 ~3,s:;:' ~: .''.:
''a:..~~. <.~, Yr r a..
4~~-~Ws~~~ v~~~r~~w~ r'~; ~~~-~i.ch ~"~~~r~r~~~~ s..h~: ~~:°.~~w v~~cY ~:.':..x ~~~: ;.~.~ ~ ~.~..~.~~:~ ~N:~~~~~~:~~ , ~: ~:~.~'~ A ~ ~: ~t-~
~:~:rE
'~; ~ ~, # i ~'e'~!: :'c.'~:~.E:# .~%Fri":ixf'.~,<'',3,'3 '~;.~3,':~' ut~~.~3'w:~.' i~~'~,::°t.'~f'x",t=> '~ , w:~y~~ r-.;., .~,; : ;~.~ .: :.;,.-~.-::
~-%~ ~ . ,. " ...%.'~:,.,,. .'~?..."., t.:'.....,.'...,.. .~ l , :~i.~,~.~
e....,.' ', :~. ;.% ~,-~. %. ~ ; ':: ~ f ..~':': ::i ~3: '.~, ~a ::: ~:: ~t~ ; :
~'~:"~: ~.;:: ~: ~: E' 'fi F:; ~;' fM h..'_"; ~ ~ ~ .~ s. .:5 ;:; <J~3 .'s'.
:~, fu,'' ~1 w:' ~!~ ''..~ i;;
A3"''.'f."~:.xAf:~.~ :~. >~,~;'~3,e"~~ '...» '~rat, L. ~~.~.~I ?:";g-~..
1'.,~~.~~$i'~.;:;f~ : 3 a o_. "y> ;
;;.t'~ :3 3, ;~.s~,,, . ~'~ ~i~~
fi v~''~ i~,~: ~3 '~"'c: ' s:, ~fa ~., % 'i t"xs' f-'. : ,,z j.. ~.;.'~tr.
,x~; ~ .-. o. ...
... '.. ~: ...:~. ....~'.:: .' ,~.%:.. ,.,..::3 ', ~.. "'.~.....~1 ..~...; ._ .:...... '_ .,. .~ %H~% ":..~'a'.~.:: a..:.;. ~ .w w .:wi : y .: f~~"''c~?:: ~;:.gw;~7.y~, 'f ~%
'.~.''~~? ~"s_i.;k.<:'~.~.~.~~' f"~.'y' ~;,'~;~f,~.'~"~3.f.~.~
~,~"G°$3,~t~.'~.;: ','w ;.L:":'a a:l ?'~Ci.
.yt 3:5. .tc rryy .~ W..~',::',3.:.':.~~# '~.t::~: i."i:3~;.f'~.'f" r.
.:'~.~:.< :, %.3~.' ~f fM:.~:.~~ . i.'::'i f ,r~~r f ,.

7:~ ';.~3,~":..:..;;.~:..~ .; .x. "~
L e~ . '.'~c~..'i kf: ~~- ~;3, ~:u:."y~'~"~~."~~' ~.:5~:''~~'.:'!."..,.'"'..'~." ~f 's~ !,~'lh'~,~~;~;'#,~4r 'a':.~"a~ 3''.
~.:..'i.-~..~, .:.':.'-'~ C)~..
'.'''.<i:~;':~ c'~ F;: ~ _ ._; <= t::~-~ _.~f.,. >,.. t , -~ -s r:%; ~y...t .., ;~a -~ ; ~ i: ,. », ;- ; ;.' :~ t.., ~.
,1:'~:.~..w.F.':::..w._ ~'w...~3~.;~ ,~ ...._.~_,._,.::.:.~ ,.'c~'....._ ;.c.....c;:~,-...~~. ,.:. .:~~.:~ i::~:;.:~:..~
.~s.~ '.'.~ ~ t:rs~?'~i~'?;'z '' .~.v~~ '~:'f, .-~~" ~.5.''~..'c'~' s #. ~
:~.~ sw~~ .~L::.~~.~~3, t',-~.:.f',~:. ;.: ~.is<3c'~.~.4~ ,''~a , 's'f'~.C.
f:2c.'~.~#.a,'':~F,'~~'3,c~',:wk:~ '::'t~~ ~~5.:3.:~3 i"~~~~G'r..'f,:3;yv.
.i<;i ci~iii'~3.~ ;':~:3,M: r~3,3:~iuy;'.;~: L,~,:x=' ~:.i.<::C'tv~i#~:.~''~. ~:3~:'.~~;.'~,~~:~~~1 'f:i"'.r''~.. ~r~::.~.~.t..
uFN<,~t :a'wiA.'A~~;Z.~ '#."C~.~ ~.?."t~?':~'.!" ~ ~'','hC:'~.
~,'~'.~.':;.~~. ~7~ f",y ,ls ~si,~'.F,:~f,~ .S'.:w>w.wx~r,a7~,4.r.;s yJ,rx~r5"'~.:J ~i. .f..' ~~.~.Jtls'S~.' ~_.:.....,.. 3..'y~:f-'~ .,'.
~ ~ ~ ~ ;" ~ ~ ~ s ~" s ..'.'.... ~J,:..»
'c;'~3, f ~:'v; ~,. !'s ~'~. f? s'~_ ';:.~:; ~ ,".-# ~. ~ t~? ~~ ~~' ~" ::,j, °,~'~ ~" ~. ~. i.; ~? <:' t: ~ ~ f:. ~. sv> 3: ~> fw ,'' : k ~ . ~' , ?.' a s:; ~~..".; .~. °~i a~ 3 s~3't,'".i3i:3w's.~''~a~~~ i'-;,rte n >." v ,-,.;~,~., ' ~rn {
~!..''.~3~:~'c'~'~~i".~., Yfa__ ~~:~~ ~,~~t~.'~:v~ :~~.~,a.'..~ ~. 'f~~ ~., ~':. s~:3r"'r~....'"7~.~.y"">3,3,''.?.~'. c'''..~t;G' Ni~:,'.r.".;3~aF.
~:~.i:"?,N.~~~4:<:i 3s:',~G~~'''i:s~'~n~.t~:0. ~ ~.:~.i:3:3,~~
f~~.':~,'3,.~'. 'v'~H ~..~3~ Li"A':".':.s'.%.f:'.'i ~.'sx~
~~~t':'.5..4::arf,f: ;.~.C:E i-:~.' ~~;'~,'.~, ~~;;;... -~:.3.'~0."'t'c.~~
Ci:~. ;:.t'':tC~
~i~'F~~,~s<;iia~."i's". ii::.fy,~xu._:_ .:;~> . .~#.'3. f~?~':~,i:''~.' 'y;
Z,~'.3~',f;~i~,~.~ ~ '~z~iE:
;~,~> :~a;;I:~ ~i.~.~"°~'~.~ <: ~~ 'r>,~ tar ,;r:.v~.'~:.~~.'3~ f'c.:"
i~~~'.'~~~,iN~'. ;~.;:'~'s~~f. 'l f.''~.~S:;.rx;"' %~3 u~~:: '-r~s'w~~G'':~'~~.~:''~'c::'~ '~'3.~a1:'?~~;~~~ 'c :? ~::>~3%~
...~~:~: ~'k''0.~~,: 'i:: zi:~ wy#::~~'v.!.:~:~ ~;~I-,:-~..~_5.~'.'.~'1~~f'~. f ~~.~:s ~.~..'f'x~:.': il't'..:~#..rik~'L:~~:5.
~~'i.~:,'.'~. ~',~;E': 'u~' ~,~f,~,~r'~j-~~~.i~:~~?f.~,' i'~: ~.f:~
~~'~'.'::'~; ~...,3"?.i~~:.
G;~ '~w~~« r~,'~iNy ~i~.'~:'~ >~,t;;~-3,~,~.i. s~°,.%a :~.'4a ~>~.~''o.~i: %."t'~f:;'i~;~>'.'~ ~'~'ii~3 '~:.~i~: !~.,~"~'s~"~t'~f.".
ts~...t:>?'3 .?.#Y~i~ 's~~C> ~.>~v.fz-t,.'~i..~'i: '~':.i':k~~. ;:~.~!~t? ~'.'X:.' 'fi3~:.~.t~.'~'4 '~,'f:.cr.~. i:',~'~ ;,3.t.:rf.'S''x:.? i3~'~:''.r<
s'~». .:~.t.;~'#.?:'~ , ~ ~' ~ ~'~." t~~, # ?:'; %: ~3, 's;' 's ~' C,~ ~' ~.. ~.... ~ ;'#.~ :h. #; 3 E;; :~ 'x:> '~'~"ice 'G''t ~'~:1.' ~;".;. !'~ I. '." t:'3 ".;'~.". s.
taw' ~G~~ ~:~:~~#.i.~'.:i.:':~ ~:~:~. ~. ~.~ w~~fw ~~.~:':~. . ~.a~ ~.~i~ :,:
~-. j::~3~ ~:::~.r#~ i~;~
~.~. s.~?.'if~'~y~a~3,~ ;~'yw ~::~s~'3.~? i~sx ~. ~: . tn~>;< . ~''C~~:' ~:>:fl~~.~5 .".; , s~t~':~:x r ., A-,r y.o v x, ~. ~_ ~; ..''i. C~ ; ... ..
'wy <~'k' ,'.n~'3. ~i~' i::'f:". ~ %?;3 ø'i:'s~'f.~~,~~ .
3?!F:'e~;~~:.';::'E°f.~sx.,;. ~w:~3, ~. ~:at.',.~:' ~ ".°c:F
''~~~~t.'~'C.'~. i:~i~#,~..~ w.';f~:.~..-.::. ..fiL' ~~"r.~:,in ~.°s.E
~c :.j,~' ~kf.ih'i,~''r.' ~ista:~.~~ ~.~. 'i':;'i.TS:C.4~~~.ø'' ~~~~."vz~:
'.3~~
, r~ w ' " ~ CA 02052691 2004-04-22 the rotary drilling rig. The time required for a tor-sional wave to travel from the drill bit to the surface is taken into account in determining the torque distributed in the drillstring at a given time. This time is deter-s mined from known theoretical relationships. -Knowing the rotational orientation of the drillstring~ and the twist in the drillstring - at the time of alignment of the orifices and knowing the angular relationship between the selected surface reference and the latch 36, the rotational orientation of the collar 20 at the time of alignment of the orifices is determined.
In one embodiment of the present invention, the curve drilling assembly comprises a PDC anti-whirl bit, connected through a bit sub to a flexible joint. The flexible joint is connected through an eccentric collar on a rotatable mandrel to a flexible drillstring. The eccen-tric collar has borehole engaging means for preventing clockwise rotation of the collar during drilling. In this embodiment, the rotatable mandrel functions as a part of the drillstring.
In an example application of the method of the present invention, during drilling of a curved borehole in an oil-producing formation, at a rotational speed of about 50 rpm and at a depth of about 5,000 ft, the rotational orientation of a collar on a rotatable mandrel of a curve drilling assembly is dynamically monitored by comparing pressure signals initiated at the collar to reference sig-nals at the surface.

During a three-second sampling interval, a pres-sure signal is detected at 2.2 seconds into the interval;
subtraction of a signal delay time of 1.2 seconds from the detection time, indicates that orifices in the collar and mandrel were aligned at 1.0 second into the interval, causing a decrease in drilling fluid pressure; reference signal data indicates that the azimuthal orientation of a primary magnetic reference location was S 74° E at the time the orifices were aligned; a 736° twist in the drillstring is calculated for a measured torque of 1,000 ft-lbs at the time the orifices were aligned; there-fore, the orientation of the collar at the time the orif-ices were aligned is determined to be due east, the same as its original orientation.
During a subsequent three-second sampling inter-val, a pressure signal is detected at 2.7 seconds into the interval; subtraction of the signal delay time of 1.2 sec-onds from the detection time, indicates that orifices in the collar and mandrel were aligned at 1.5 seconds into the interval, causing the decrease in drilling fluid pres-sure; reference signal data indicates that the azimuthal orientation of a primary magnetic reference location was S
64° E at the time the orifices were aligned; a 736° twist in the drillstring is calculated for a measured torque of 1,000 ft-lbs at the time the orifices were aligned; there-fore, the orientation of the collar at the time the orif-ices were aligned is determined to be S 80° E.
Drilling is stopped and the drillstring and man-drel are rotated counterclockwise. After a pressure signal at the surface indicates that a latch in the man-drel has engaged the collar, the drillstring is rotated counterclockwise another 10° to reorient the collar to due east.
The oil-producing formation in this example extends from a depth of. about 4,900 ft to a depth of about 5,100 ft and is penetrated by a vertical wellbore. A
workover rig, with a power swivel, and a curve drilling assembly for drilling short radius lateral boreholes are provided for drilling a lateral drainhole into the forma-tion.
Torque in the drillstring and mandrel is meas-ured during drilling with a strain gauge load cell located in the power swivel torque arm of the rotary drilling rig.
At 5,000 ft, a torsional wave travels from the drill bit to the surface in approximately 1/2 second. Thus the torque recorded for the next 1/2 second after alignment of the orifices is the torque distributed in the drillstring at the tame the orifices were aligned.
Prior to tripping the drillstring and curve drilling assembly into the borehole, an angular relation-ship is established between a latch on the mandrel and a mule shoe orienting sub key. Once the drillstring and curve drilling assembly are tripped into the borehole, for initiating directional drilling at a depth of about 5,000 ft., the drillstring is rotated clockwise six times with the bit off bottom to set the tare torque. A
magnetic survey tool is seated in the key of the mule shoe orienting tool for determining the orientation of the mule shoe key, and thus the latch on ~o5zoo~
the curve drilling assembly mandrel. A primary magnetic reference is established at the surface on a rotating sub below the power swivel to reference the azimuthal orien-tation of the mule shoe key and thus the latch. The drillstring and mandrel are rotated counterclockwise for establishing the original orientation of the collar at due east. Orientation of the primary magnetic reference location is also at due east.
A signal generator at the collar is utilized for dynamically monitoring rotational orientation of the collar during drilling. Signal delay time is established by rotating the drillstring clockwise at speeds of 20, 30, 40, 50, 60, 70, and 80 rpm. When an orifice in the man-drel aligns with an orifice in the collar during each rotation of the mandrel, drilling fluid pumped through the drillstring and mandrel flows out through the orifices causing a fluid pressure decrease which is detected with a pressure gauge at the surface. The orientation of the primary magnetic reference, relative to its initial orien-tation of due east, is monitored at the time each fluid pressure decrease is detected. Reliability of the data is .established by repeating the 20 rpm data point. Orien-tation of the primary magnetic reference at the time the pressure decrease is detected is plotted vs. drillstring rotational speed. The slope of a line fit to the data, 7.2 deg/rpm, is equivalent to a signal delay time of 1.2 sec at about 5,000 ft.
For generating the reference signals, the pri mary magnetic reference is established at the surface on ~(152G~1 the rotating sub below the power swivel at due east for referencing the orientation of the mule shoe key. Eleven smaller, secondary magnetic references are established on the rotating sub, with spacing of 30° between the magnetic references. A magnetic detector is located at a station-ary location due east of the rotating sub for generating a distinct reference signal each time a magnetic reference rotates past it.
In another embodiment, the present invention is directed toward an improved signaling apparatus and method for use in determining the orientation of a drilling assembly for drilling curved boreholes. In this embod-invent, the signal 26 is generated using an improved sig-haling apparatus 32 which includes an orifice 34 through Z5 the wall of the conduit 22 and an orifice 35 through the wall of the collar 20. The collar 20 and conduit 22 are rotatable relative to one another about the longitudinal axis 38 of the conduit 22. The orientation of the conduit 22 relative to the collar 20 when orifices 34 and 35 are aligned is related to a stationary reference, one that does not rotate with the drillstring, as described above.
Whenever orifices 34 and 35 are aligned, during drilling or when drilling is interrupted, fluid flowing in the con-duit 22 flows through the orifices 34 and 35, causing a fluid pressure decrease detectable at the surface. In this embodiment, the orifices 34 and 35 are configured to provide a distinct signal 26, which is detectable at the surface. When the orifice 34 in the conduit 22 is round, orifice 35 in the collar 20 can be an elongated slot for ~U5~6U1 strengthening or increasing the duration of signal 26.
When the orifice 34 is square, the orifice 35 is square for providing a sharper or more distinct signal.
While present embodiments of this invention are described herein for the purpose of disclosure, numerous changes in the construction and arrangement of parts and the performance of steps will suggest themselves in those skilled in the art, which changes are encompassed within the spirit of the invention as defined by the following claims.

Claims (4)

1. A method for monitoring the rotational orientation of a downhole tool on a rotatable conduit while drilling, comprising the steps of:
(a) establishing an initial rotational orientation of the downhole tool with respect to a plurality of reference points on the rotatable conduit;
(b) generating at least one reference signal each time said reference points and the rotatable conduit complete 360 degrees of rotation while drilling;
(c) generating a tool signal each time the rotatable conduit is in a defined rotational orientation with respect to the downhole tool while drilling, and (d) measuring the angular displacement between said at least one reference signal of step (b) and said tool signals of step (c), and using said initial rotational orientation of the downhole tool of step (a) to determine while drilling the angular displacement of the downhole tool.

2. A method of claim 1 in which step (c) comprises the steps of:
flowing fluid through the rotatable conduit;
changing the size of a fluid flow path through the rotatable conduit when the rotatable conduit is in said defined rotational orientation with respect to the downhole tool; and sensing the response of the flowing fluid to the change in size of the fluid flow path to generate said tool signal.

3. A method of claim 1 in which step (c) comprises the steps of:
pumping fluid through the rotatable conduit;
changing the size of the fluid flow path through the rotatable conduit when the rotatable conduit is in said defined rotational orientation with respect to the downhole tool in order to create a pressure change in the flowing fluid;
recording a pressure profile of the pumped fluid when the rotatable conduit is not rotating;
recording a pressure profile of the pumped fluid when the rotatable conduit is rotating; and comparing the pressure profiles.

4. The method of claim 1, further including the step of:
(e) stopping rotation of the rotatable conduit and reorienting the downhole tool when dynamic monitoring indicates that reorientation is necessary.