US2660887A - Method for detecting the source and analyzing the flow of water intrusions in oil wells - Google Patents

Description

Dec. 1, 1953 660,887

F. FRI-:l 2, ME D DETECTING THE SOURCE A ANALYZING F OF' WA INTRUS IN L WELLS Fil Sept my 2f Wasi l l l /l I 26a E *g 22 -:TILEL y l I l 23 ENTOR czieMc/G FWO' BY @www ATTORNEYS.

Patented Dec. l, 1953 OFFICE METHOD FOR DETE AND ANALYZING T CTING THE SOURCE HE FLOW vOF WATER INTRUSIONS IN OIL WELLS Frederick Frei, Los Angeles, Calif. Application September 1, 1950, Serial No. 182,770

19 Claims.

This invention relates to a method for detecting the source and analyzing the flow of water intrusions in oil wells. Y

In the drilling of oil wells it is the general experience thatthe well bore passes through one or more water sands before the oil bearing strata or pay formation is reached. Each of these Water sands is a source of water ow into the well and, if permitted to mix into the oil, destroys the well insofar as its commercial exploitation is cone cerned. It is the practice, therefore, to seal oii each of these water sands as the drilling of the Well progresses.

There are many methods of sealing off each of the overlying water bearing strata, the majority of these involving the cementing, in some manner, of the water sand. This cementing is accomplished as each water sand is met, and an attempt is made to completely seal the strata before the Well bore is pushed further down through the earth strata.

Probably the most common of the cementing methods is the one shown in connection with the present invention. As the well bit forms the bore a casing consisting of jointed sections of pipe is let down into the bore. When a water sand is encountered, the bore and casing are carried a short distance beyond the sand into a solid formation. A cement slurry is then dumped down the casing and forced upwardly in the `bore outside of the casing until it passes beyond the water bearing strata for a distance estimated to be sufficient. When the cement has hardened, the drilling of the Well bore is resumed with a smaller bit and a casing of smaller diameter than the original casing. This rleaves an annular shoulder upon which the surface casing and cement seal may rest. This isrepeated at each water sand.'

In wetcementing operations, however, it is very difcult to achieve a'tight waterseal. holes and the weight of the great length o1" casing often results in the casing not being disposed centrally of the hole. This may result in the slurry being unevenly distributed and the formation of a point of weakness. Although presumably forming a good seal at the time of. cementing, the seal may break as the drilling ofA the wellprogresses or after the oil strataghasbeen reached and the well 'is in operation; Therefore, when water appears in the bottom of awell bore there may be considerable doubt as to the source of the water, and especially when several water sands have been passed. In order to avoid premature and unnecessary abandonment of awel] it is `essential to know quickly and accurately the source of such Crooked 2 water. During the drilling it is important to know if the water is indigenous to the formation being cutor if it comes from a leak in one or more of the water seals above. It is especially important to know this when drilling in the Vexpected pay formation as the well may be prematurely abandoned as a well making water.

Chemical water analyses are quite often not available, or if available, may be too similar for identification purposes. In this and several of the other presently known methods of analysis of the source of intrudedwater, the human element of interpretation is present with the resultant inaccuracies, and such a study or analysis is usually long and costly, involvingv laboratory equipment, cessation of drilling operations, and manipulation of various types of equipment within the well bore.

In addition to the source of water, it is also helpful to know whether the flow of water from one or more leaks is increasing or decreasing and especially the increase or decrease of each individual leak.

It is an object of this invention to provide a positive and accurate method with a minimum of error due to human interpretation of determining the source of one or more water intrusions in an oil well. Y

It is a further object of the invention to provide a method of analysis of the rate of riiow of a water intrusion or of each of several intrusions.

It is another object of the invention to provide a direct and inexpensive visual method of analysis of water intrusions or the rate of flow thereof requiring but simple and inexpensive neld equipment. and within the capability of the average geologist or engineer at'the Well. f

Stillanother object of the invention is to provide a method of analysis that can be carried out while the drilling operation is in process. v

Still another object of the invention is .to provide a method of determination of the source of water intrusions or the rate of flow thereof which is adaptable to various types of water sealingin cluding cement seals and elastic and inatable packers.

With the aboveand otherobjects in view that will become apparent as the nature of the invention is better understood, the same consists in the novel form, combination and arrangement of parts hereinafter more fully described, shown in the accompanyingdrawing, and claimed.

In the accompanying drawing, like characters of reference indicate like parts in the several vieu/sand: y

Fig. l is a fragmentary sectional View of a well bore showing the method of the present invention as applied to a well employing one of the most common methods of cementing off water sands in a well bore and showing the bore passing through two water sands and into an oil bearing strata.

Fig. 2 is a fragmentary sectional View of aportion of a well bore showing a modification of the method of placing an identifiable substance in the cement of the water seal at a sealed water strata.

Fig. 3 is a fragmentary sectional-,view offa portion of a Well bore showing a further modification of the placing of the identifiable substance ,ata

water seal.

While the method of the present-invention iis shown as herein applied to one of lthe most common methods of cementing a well bore, it is to be understood that it may be applied to v arious methods of cementing and/or sealing oi the water strata thereof, and in its modified form also used in con-junction with many other water sealing methods, such yas by expansible or inflatable packings well bore and where plastic materials or other substance instead of cement are utilized in making the slurry with which the water is sealed off.

In Fig. 1 of 'the drawing is shown a well to which has been applied the preferred and basic method of the present invention, structural details of the casings and fittings thereof being omitted for the purpose of clarity. In the drawing the reference numeral I0 indicates the uppermost non-water bearing strata through which the well bore has passed. The numeral II indicates a strata of water `bearing (sand, and the reference numeral I3 a second water bearing Ystrata below and separated from .the water sand II by an 'intermediate strata I2. 'Ijhe numeral I5 designates Van oil bearing formation separated from the water sand I3 Vby Vvan intermediate non-water bearing vstrata -I 4' and which oil bearing formation' I5 the well bore is terminatedvThe well bore V has the usual enlarged upper portion I6 which extends through the Water sand II and some distance into the formation I2. The well bore is then Yreduced in diameter as at I1, forming the annular shoulder la, this bore I'I of reduced diameter extending downwardly through the water `sand I3 andinto the neutral formation I 4. The well bore is again reduced as at I9, forming the annular shoulder 2 3. yPositioned within the upper portion I6 of the bore is the `usual outer or surface casing 2|, within the bore I1 the intermediate casing 22, and within lthe bore portion I9 the oil string 23. In the oil string 23 are the oil intake ports 24.

In the bore portion -I6 and outside ,of the surface casing 2| is placed the usual cement seal 25 and a Asimilar seal 26 is placed in the A,bore portion I1 outside of the intermediate casing 22.

The structure thus far described and zshown in Fig. 1 represents an application of a standard method of cementing an oil well encountering water strata.

The basic step of the method of the present invention consists of the adding to yand/0r mixing with the cement Aslurry at the time of pouring of the seal an identifiable Vsubstance which does not chemically react with the cement during the setting thereof. A different lidentifibetween the casing and .uble dyes of .various colors, which able substance is placed in the cement seal of each water sand. In Fig. 1 the particles 21 represent the identifiable substance in the cement seal 25 and the particles 23 represent the identifiable substance in the seal 23, the two substances having a substantial difference.

Many different types of identifiable substances may be used, the 'important restriction being that they do not interfere with the chemical setting of the cement or lose their identity in the chemical reaction. One of the preferred substances is finely `ground colored glass or plastic -materiaL The colors should be bright and the particles preferably of colloidal dimension, but not finer than the cement particles. The identifiable substance may consist of Water solare easily identified by using a colorimeter. Other suitable substances are the luminescent minerals which maybe identified with ultra-violet light, or the radioactive mineral carnotite which may be identified with arGeiger counter. l

A suitable proportion for the identifiable substance and the cement mix is one to two pounds of Ythe substance to one hundred pounds of cement, although any desired proportion may be used.

When water appears in the bottom hole it may come from several sources as indicated by the directional arrows of Fig. 1. It may work down from the water sand II around the seal 25 into the bore Ii, enter a leal; in the casing 22 as indicated at 29, and thence run into the bottom hole. Water from the water sand I3 may likewise work around the seal 26. Or the water may be indigenous to the oil bearing formation. If the water is from overlying sands it will, in passing through or around the cement seal containing the identifiable substance, pick up a lcertain amount of such substance and carry it into the bottom hole where it remains in suspension in the bottom hole water.

It may be pointed out that where there are several seals one above the other, and where one ofthe upper seals developes a leak while the lower seal or seals and the casing remain tight, the leakage water will not find its way in to the well bore hole and no problem will be presented to the driller. The present invention is directed to the situation where the leakage water from an upper seal does manage to nd its way into the bore hole. As a practica l matter it is very difcult to keep a tight casing string and water under a pressure head very often finds its way through a casing fracture or defective threaded joint and down into the bore hole. In rarer cases it may also be true that a series of seals Will leak, and water from an upper seal will work its way down through the lower defective seals. In this case the present method clearly indicates that the series of VYseals are defective, and which ones. In summary, it is only when water appears in the borehole at the lower end of the well bore that the identifying means of the invention becomes necessary. The present method is equally effective where there is only one sealed water bear in g strata or a plurality thereof, since the presence or absence of identifying substance indicates whether the water is from the supposedly sealed water strat-a or the formation currently being drilled.

It will thus Ybe seen that a simple analysis of the water from the bottom hole will immediately and accurately indicate the source of the leak or abbassa'- leaifzs, or inform the drillerthat thefwater-is indigenous to the oil formation; yorto the formation being currently drilled if the well is in process of drilling.

In Fig. 2 is shown an important modification wherein the cos.J of the method may be reduced. Since the path -of the water from the water sand lia is downward, it isnecessary that at each water the identiiiable substance be added only to a portion of the cement seal 25e at some point below the water sand. Since a single seal may require as much as 56@ bags of cement the saving in the identifying material is substantial if such material is added to only a portion ofthe seal.

In Fig. 3 is shown a further modiiication wherein the identifiable substance 2lb is applied to the surface of the well bore 511 and/or the outer surface of the casing ilib at and within the section of the well bore to be cemented and/or sealed off, by spring or the like prior to the cementing of the water sand. in the case where elasticl or inflatable packers are used as water seals, this application. of the substance to the well bore serves the same purpose as when a cement seal is used and would work equally well. i

in rotary drilling where one or more water sands have been sealed the source of water appear-ing in the bore be determined without cessation ci the drilling operation if a separate identifiable substance has been incorporated in each water seal. A sample of the drilling fluid is taken where it Hows into the slush pit. This then placed in a centrifuge for a desired period of time and the fluid examined under a microscope for the identifying substance.

It is likewise possible to determine if there is an increase or decrease of water flow in an intrusion by incorporating in each water seal an identifiable substance, taking a new sample each two hours, preparing a plurality of slides on each sample, and then counting the identifying particles on each slide under a stage microscope. By comparing the average count of each group of slides, an acc rate conclusion as to whether the flow is increasing or decreasing may be formed.

While there are herein shown and described the preferred embodiments of the invention, it is nevertheless to be understood that minor changes may be made therein without departing from the spirit and scope of the invention as claimed.

What is claimed, is:

l. The method of determining the source oi' water in the bottom or" a Well bore wherein a water seal is established at each of a plurality of water bearing strata, consisting of the placing adjacent each such water strata, prior to the sealing thereof, of a different identiable substance adapted to be washed into the bore hole in the event cf leakage by said seal and subsequently analyzing the water in the well bore to determine the presence and type of identifiable substance or substances which may be contained therein as an index of any leaky seal or seals.

2. rThe method of determining the source of water in the bottom oi a well bore wherein a water seal is established by cementing at each of a plurality of water bearing strata, consisting of the placing adjacent each such Water strata prior to the cementing thereof of a diiferent identiable substance adapted t0 be washed into the bore hole in the event of leakage by said seal and subsequently analyzing the water in the well bore to determine the presence and type of identiable substance or substances which may becontained therein-as an index oil-any leaky seal orseals.v f 'Y 3. The method as set forth in claim 2 wherein the identiable'substance is applied to the surface of the well bore on and adjacent each water strata and the cement seal applied as a coating thereover. v

' i.' The method of determining the source'oi water in the bottom of'a well bore wherein a water seal is established by cementing at each of a plurality of water bearing strata, consisting of mixing with the cement used to seal each such strata a diierent identifiable substance adapted to tie-washed into the bore hole in the event of leakage by said seal, and subsequently analyzing the water'in the well bore to determine the presence and type of identiiiable substance or substances which may be contained therein as an index of any leaky seal or seals.

5. The method of determining the source of water in the bottom oi a well bore wherein a water seal is established by cementing at each of a plurality of water bearing strata and wherein such cement seal extends in the well bore slightly above and below each such strata, consisting of mixing with a portion of the cement used to seal each such strata a different identiiiable substance adapted to be washed into the bore hole in the event of leakage by said seal, at least some part of said vportion being below said strata, and subsequently analyzing the water in the well bore to determine the presence and type of identifiable substance or substances which may be contained therein as an index of any leaky seal or seals.

6. The method of determining the source or water in a well bore wherein a plurality of water bearing lstrata have been sealed and without interrupting the continuous drilling of said bore, consisting of placing a diierent identifying substance adjacent each strata prior to the sealing thereof, said substance being adapted to be washed into the bore hole in the event of leakage by said seal, taking a sample of the drilling mud where it flows into the slush pit, subjecting the same to a centrifuge, and then analyzing said concentrated sample to determine the presence and ,type of identiable substance or substances which may be contained therein as an index of any leaky seal or seals.

7. The method of determining the increase or decrease of the flow of each water leak in a well bore wherein a plurality of water bearing strata have been sealed, consisting of placing a different identifying substance in particle form adjacent each strata prior t0 the sealing thereof, said substance being adapted to be washed into the bore hole in the event of leakage by said seal, taking a new sample of the water in said well bore at frequent intervals, preparing a group of microscopic slides of each sample, counting the particles of said identifying substance on each slide of said group, averaging the number of said particles for each group, and recording said series of averages to thereby indicate the increase or decrease of the flow of each leak.

8. The method as set forth in claim 4 wherein said dilerent identifying' substances consist oi finely ground particles of various colored solids, said particles being at least as large as the cement particles but small enough to normally remain in suspension in a iiuid.

9. The method as set forth in claim 4 wherein said different identifying substances consist of various colored Water soluble dyes.

7 Y 10. The method as set forth in ,claimi wherein said identifying substance consists of a luminescent mineral.

11. The method as set forth in claim 4 wherein said identifying substance consists of a radioactive material.

12. The method as set forth in claim 2, wherein the identifiable substance is applied to the outer surface of the casing at and adjacent to each water strata and the cement seal applied as a coating thereover.

13. The method as set forth in claim 2, wherein the identifiable substance is applied to the surface of both the well bore and well casing placed within said bore, at and adjacent to each Water strata, and the cement seal applied as a coating thereover. Y

14. The method of determining the ,SOllrce f water in the bottom oi a well bore wherein a water seal has been established at each of the plurality of water bearing strata, consisting of mixing with a plastic or other substance used to seal each such strata a different identiiiable substance adapted to be washed into the bore hole in the event of leakage by said seal, and subsequently analyzing the water in the well bore to determine the presence and type of identifiable substance or substances which may be contained therein as an index of any leaky seal or seals.

15. The method oi determining the source of water in the bottom of a well bore wherein a water seal is established by cementing at each of a plurality of water bearing strata, consisting of associating with each said cement seal a different identiable substance adapted to be washed into the bore hole in the event of leakage by said seal, and subsequently analyzing the water in the well bore to determine the presence and type of identiable substance or substances which may be contained therein as an index of any leaky seal or seals.

1G. The method of determining the source of water in the bottom of a well bore wherein said well has a casing or" lesser diameter than said well bore and wherein a vcenfientitious sea-ling material is placed between said casing and the wall of said vbore at ea'ch of a plurality of water bearing strata to seal off said strata, consisting of associ'- ating with each said a different identiiiable sea substance adapted to be washed into the bore hole in the event of leakage by said seal, and subsequently analyzing the water in the well bore to determine the presence and type of identiable substance `or substances which may -be contained therein as an index of any leaky seal or seals.

17. The method of determining the source yof water in the bottom of a well bore wherein said Wellhas a casing of lesser diameter than said well bore and wherein a cementitious sealing material is placed between said casing and the wall of said bore at each of a plurality of water bearing strata to seal off vsaid strata, consisting of mixing with said cementitious material at each seal a different identiable substance adapted to be washed into the bore hole in the event of leakage by said seal, and subsequently analyzing the water in the well bore to determine the presence and type oi identifiable substance or substances which may be contained therein as an .index of any leaky seal or seals.

1 8. The method `of determining the source of water in the bottom of a Well bore wherein said well has a casing of lesser diameter than said well bore Aand wherein a cementitious sealing material is placed between said casing and the wall of said bore at each of a plurality of water bearing strata to seal oi vsaidstrata, consisting of placing between the cementitious material and the well bore at each seal a layer of different identiable substance adapted to be washed into the bore hole in the event of leakage by said seal, and subsequently analyzing the water in the well bore to determine the presence and type of identifiable substance or substances which may be contained therein as an index of a leaky seal or seals.

19. The method of determining the source of water in the bottom of a well bore wherein a water seal is established by cementing at at least one water bearing strata, consisting of associating with said cement seal an identifiable substance adapted to be washed into the bore hole in the event of leakage by said seal and subsequently analyzing the water in the well bore to determine the presence of said identifiable substance as an index o f a leak in said seal.

FREDERICK FREI.

References Cited in the file of this patent UNITED .STATES PATENTS Number Name Date 1,133,218 Beecher Mar. 23, 1915 2,183,654 Moore Dec. 19, 1939 2,301,190 Boynton Nov. 10, 1942 2,439,542 Hunt Apr. 13, 1948

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