US2808887A - Method for loosening stuck drill pipe - Google Patents

Description

Oct. 8, 1957 w. c. ERWIN METHOD FOR LOOSEN'IENG STUCK DRILL PIPE Filed Sept. 22, 1955 INVENTOR. WELDON c. ERWIN TTORNEYS METHOD FOR LOOSENIN G STUCK DRILL PIPE Weldon C. Erwin, South Gate, Calif. Application September 22, 1955, Serial No. 535,840

7 Claims. (Cl. 166-43) This invention generally relates to a method of loosening and freeing a drill pipe or equivalent string of pipe, casing, or tubing which has become stuck in the course of well operations. The invention will be illustratively described in connection with oil drilling operations where solid materials have settled or foreign objects or particles have lodged in the annulus between the operating string and the side walls of the well bore, although it will be appreciated that the method may be advantageously employed in other analogous applications. In its use in oil well operations, the method of the present invention, in common with certain methods here tofore used for the same purpose, is based upon creating a fluid surge within the well by varying the hydrostatic head of the liquid or circulating mud in the well. In the hydraulic methods previously used, it is usually essential that a normally closed chamber be lowered down within the well to a given location, and thereafter suddenly opened to admit the circulating fluid, whereby a fluid surge is effected tending to jar loose the stuck section of the drill pipe string. In other methods presently employed, it is required that the pipe be severed or parted above the stuck point by unscrewing, cutting, or blasting, and the free portion thereafter removed from the Well bore, before the actual stuck portion, or fish, as it is commonly called, can be recovered.

The primary object, therefore, of the present invention is to provide a method of loosening and freeing a stuck drill pipe or equivalent tubular string without the necessity of lowering or forming a closed chamber within the drill pipe, and without the necessity of severing the drill pipe string as a preliminary step before the utilization of 4 onventional recovery methods and devices.

A more specific object of the present invention is to provide an improved method of loosening and freeing a stuck drill pipe or equivalent tubular string wherein no additional apparatus or tools need be inserted into the well, and in which the hydrostatic column within the well is instead used as the primary means of creating the hydraulic or fluid surge required.

Briefly, these and other objects of the present invention are achieved by providing a controlled pressure source on the surface as a means of creating a pressure differential between the fluid column in the annulus, defined hv the drill string and the side walls of the well bore, and the fluid column within the drill pipe. In order to establish this condition, the upper end of the drill pipe is closed off and connected to the pressure source. Thereafter, the pressure source is used as a means of transmitting compressed air or gas, or conceivably a fluid United tates Patent 9 may be passed from the well at ground level through a conduit to a tank or reservoir for temporary storage or to the mud pit.

After the hydrostatic column within the drill pipe has been lowered to a predetermined location according to the pressure differential required, the pressure source may then be actuated so as to release the compressed gas from within the drill pipe string. In response to the releasing of the gaseous pressure, a surging inward fluid flow will occur from the annulus back through the bit opening and'up into the drill pipe. The surging flow will tend to wash loose any material which may have accumulated or settled in the annulus as well as dislodge any foreign objects stuck between the drill pipe and the well side walls.

If the initial injection and release of the compressed gas Within the drill pipe does not suflice to loosen-the stuck section of pipe, the control pressure source may be intermittently actuated to close off and release compressed gas within the drill pipe, as by opening and closing a control valve. As a result, a fluid ram effect will be created imparting a vibrating and jarring action to the drill pipe string.

According to the particular well conditions, an additional step as a part of this method may be required in order to prevent well caving or sloughing. This additional step consists of reinjecting or pumping fluid back into the annulus at substantially the same rate it flows back into the drill pipe in response to a releasing of the pressurized gases from within the pipe. In this manner, a full hydrostatic column can be maintained in the annulus so that the circulating fluid level will not drop below the bottom of the surface casing to create the possibility of sloughing or the danger of a well blowout in the event high pressures exist in the surrounding formations.

A better understanding of the present invention will be had by reference to the accompanying drawings, which merely illustrate one conceivable apparatus for the performance of the method, and in which:

Figure 1 is an elevational view of a typical oil Well and drilling rig, in which the drill pipe is stuck because of materials and foreign objects lodged between the drill pipe and well side walls; and,

Figure 2 is a view of the oil well of Figure 1 after pressurized gas has been injected into the drill pipe from the surface.

There is shown in Figure l a derrick 10 disposed above an oil well 11. The well is provided with a casing 12, and positioned Within the casing is an operating string or drill pipe 13. The drill pipe 13 terminates at its lower end in a conventional bit 14 having an opening 15.

In the annulus 9 formed by the drill pipe 13 and the well side walls or casing 12, there is shown a layer of impacted material 16 and foreign objects 17, near the bottom portion of the drill pipe 13, which have settled so as to prevent or hamper further movement of the drill pipe 13.

The entire well 11, as in conventional oil drilling operations, is filled with a circulating fluid or mud 18, which flows down through the drill pipe 13, out through the bit opening 15 and then up through the annulus 9 between the drill pipe and the casing 12 to flow out at the surface of the well into a mud ditch (not shown) and thereafter into a mud pond or pit 19. The mud 18 is recirculated through the well from the pit 19 by a conventional slush pump 20 and valving 21 to thereafter pass through a rotary hose 22 back into the drill pipe 13 through a conventional rotary table 23. I

The method of the present invention is primarily directed toward providing a controlled source of pressurized fluid, preferably gas or air. In consequence, there is additionally provided at the surface of the well awe iliary equipment in the form of a pressure system, generally designated by the numeral 24. This pressure system 24 is schematically shown as comprising a plurality of combustion chambers 25, each of which has aninlet 26 connecting into a manifold 27. The manifold 27 would, in turn, include appropriate high pressure control valving indicated at 28 and preferably located within the drill stem or pipe 13 and pressure relief valving indicated at 29. A flexible hose 30, similar to the rotary hose 22 used in connection with the circulating system, could be provided for connection between the manifold 27 and the drill pipe 13.

In, the practice of the method of the present invention, a rapid burning fuel (similar'tothat used inrockets and the like) is placed into the combustion chambers 25 where it is ignited or detonated, to in turn create high pressure gases that will pass through the valves 26 and thereafter into the manifold 27 to pass down into the drill pipe 13 as shown in Figure 2 at 31. A conventional fuel comprised of sticks of cordite, for example, encased in an inert material within the combustion chambers 25 might be employed for this purpose. By encasing the cordite sticks in an inert material, a controlled burning rate may be achieved over a period of sixty seconds or longer with a consequent gradual build up of pressure within the drill pipe 13. A plurality of electrical heating elements or coils couldbe located within the combustion chambers adjacent the end faces of the sticks, and might be connected to a suitable source of power at the well location for initiating the burning of the fuel within the combustion chambers. The inlet valves 26 are provided with check valve devices so that the high pressure gases formed in the individual combustion chambers 25 will have a cumulative effect, and whereby each chamber 25 actually operates as an individual unit. It is feasible, therefore, to utilize any number or combination of the combustion chambers 25 as a means of creating a particular pressure and volume of gas required.

Assuming that the drill pipe in the well 11 has become stuck because of the impacted material 16 and the foreign objects 17, the circulating system is first shut off, and the necessary steps are taken to properly close and seal off the drill pipe 13 at the surface of the well, as by the control valve 28, according to the particular type of equipment being used. Thereafter, the flexible hose 30 is connected to the closed ofl end of the drill pipe 13 so as to communicate thereto through the valve 28. The pressure system 24 is then actuated so as to pass the pressurized gases 31 from the individual combustion chambers 25 through the respective inlet valves 26, and thereafter into the manifold 27, through the control valving 28, and the flexible hose 3% down into the drill pipe 13. As a consequence, the mud 18, normally having a hydrostatic head rising within the well and within the drill pipe 13 to the surface, is forced down to a predetermined level, L, as shown in Figure 2, by the pressurized gases 31. The mud 18, being urged downwardly, will pass through the bit opening 15 and thereafter into the annulus 9 between the drill pipe 13 and the casing 16, which will result in an overflow of mud from the annulus into the mud ditch, to thereafter pass to the mud pit 19.

When the column of circulating mud has stabilized at the level L, according to the pressure of the gases 31, it will be evident that a pressure differential will exist between the column of mud within the drill pipe 13 and the column of mud in the annulus 3, proportional to the distance from the level L to the surface. This level may be readily ascertained by measuring the volume of fluid displaced from the annulus, at the surface of the well. At this time, the control valving 28 and relief valving 29 may be actuated so as to open a passage from the drill pipe 13 through the hose 36 and manifold 27 to atmosphere. In consequence, the gases 31 will suddenly, in response to the opening of this passage, expand upwardly out of the drill pipe. In response to the escape of the gases 31, the unbalanced columns of the circulating mud 18 will tend to re-level, and a violent surging flow will occur as the mud within the annulus 9 passes back through the bit opening 15 and up into the drill pipe 13. This surging fluid movement will frequently be sufficient to wash away the impacted material 16 and dislodge the foreign objects 17. i

In the event that the initial injection and release of the gases'31 is not suflicient to accomplish the loosening of the drill pipe 13, the control valving 28may be intermittently opened and closed, before the gases 31 have been totally expelled, to create a ramming fluid action vibrating and jarring the drill pipe 13 while at the same time washing through the impacted material 16 and foreign objects 17. The intermittent changing of the level of the fluid head within the drill pipe 13 will generally free the pipe and loosen it from the material 16 and objects 17.

It is desirable, in accordance with conventional practice, that the drilling cable, as at 32 in Figure 1, be placed in tension so as to exert an upward strain on the drill pipe 19 while the gases 31 are being injected and expelled; also, torque may be applied to the drill pipe in order to supplement the surging action of the circulating fluid or mud in freeing the stuck portion.

It will be appreciated, that in order to prevent cave-ins or damage to the casing 12, as aresult of high pressure formations existing in the area surrounding the well 11, it is desirable to maintain a high level of circulating mud 18 in the annulus 9 at all times. Therefore, as the hydrostatic column within the annulus is decreased as it flows back into the drill pipe 13, it is important that the annulus be replenished with mud at substantially the same rate that it being displaced. For this reason, under most well conditions, at the time the gases 31 are being expelled to the atmosphere, the circulating system should be re-actuated by starting the pump 20 and operating the valving 21 so as to bypass the hose 22 and cause a flow of circulating mud to pass back into the annulus of the well, as through a conventional fill line 33. Not only will the replenishing of the circulating mud 18 into the annulus serve to prevent possible cave-ins, but it will also have a tendency to lengthen the time during which the pressure differential between the column within the drill pipe 13 and in the annulus is maintained.

It will be evident, that although a preferredpressure system 24 has been shown for the performance of the method of this invention, that other systems are equally feasible. For example, air compressors or high pressure gas lines, or anyother apparatus capable of delivering fluid under the requisite pressure conditions may be utilized. The combustion chambers 25 are advantageous because of their portability and the fact that they do not require connecting power or pressure and are thus more versatile and adaptable for use at most drilling locations.

It is further conceivable under certain conditions that the compressed gases might be forced into the annulus to create a reversed flow. It is apparent, therefore, that certain changes may be made in the method, according to the application involved, without departing from the spirit and scope of the invention.

What is claimed is:

1. In well operations in which a hydrostatic column of circulating mud is normally disposed in the well and within a tubular string positioned within the well and spaced apart from the side walls, a method for loosening a stuck portion of said string comprising the steps of: closing off the upper end of said string to the circulation of mud; connecting a controlled pressure source of fluid to said upper end for communication therethrough into said string; actuating said source so as to inject under pressure into said string a given volume of said fluid to thereby decrease the hydrostatic column within said string; and actuating said source to release said pressure,

whereby a reverse surging flow will occur increasing the hydrostatic column within said string.

2. In well drilling operations in which a hydrostatic column of circulating mud is normally disposed in the well and within the operating string of pipe, a method for loosening a stuck portion of said string comprising the steps of: closing off the upper end of said string to the circulation of mud; connecting a controlled pressure source of fluid to said upper end for communication therethrough into said operating string; actuating said source so as to inject under pressure into said string a given volume of said fluid to thereby decrease the hydro static column within said string; and actuating said source to release said pressure, whereby a reverse surging flow will occur increasing the hydrostatic column within said string.

3. The method according to claim 1, in which said fluid comprises a compressed gas.

4. The method according to claim 1, in which said fluid comprises a liquid having a lower specific gravity than said circulating mud.

5. In well drilling operations in which a hydrostatic column of circulating mud is normally disposed in the well and within the operating string of pipe, a method for loosening a stuck portion of said string comprising the steps of: closing off the upper end of said string to the circulation of mud; connecting a controlled pressure source of gas to said upper end for communication therethrough into said operating string; actuating said source so as to inject under pressure into said string a given volume of said gas to thereby decrease the hydrostatic column of mud within said string by effecting an outward flow through a lower opening into the annulus between said string and the well side walls; actuating said source to release said pressure, whereby an inward surging flow will occur from the column within said annulus back through said lower opening into said operating string; and reinjecting circulating mud into said annulus at substantially the same rate it is displaced therefrom during its flow back into said operating string.

6. In well drilling operations in which a hydrostatic column of circulating mud is normally disposed in the well and within the operating string of pipe, a method for loosening a stuck portion of said string comprising the steps of: closing ofl? the upper end of said string to the circulation of mud; connecting a controlled pressure source of gas to said upper end for communication therethrough into said operating string; actuating said source so as to inject under pressure into said string a given volume of said gas to thereby decrease the hydrostatic column of mud within said string by effecting an outward flow through a lower opening into the annulus between said string and the well side walls; and actuating said source to intermittently release said pressure to cause a corresponding intermittent changing of level of fluid within the drill pipe and create a ramming fluid action within said operating string.

7. The method according to claim 6, in which a torque and axial strain is applied to said operating string.

References Cited in the file of this patent UNITED STATES PATENTS 1,774,640 Dunn Sept. 2, 1930 2,139,076 Gates Dec. 6, 1938 2,163,115 Beckman June 20, 1939 2,361,558 Mason Oct. 31, 1944

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