US3422672A - Measurement of earth formation pressures - Google Patents

Description

'aa a Jan. 21, 1969 P. A. PAYNE 3,422,672

MEASUREMENT OF EARTH FORMATION PRESSURES Filed Dec. 27, 1966 Sheet INVENTOR. PERCY A. PAYNE,

AT TORNEY.

Jan. 21, 1969 P. A. PAYNE MEASUREMENT OF EARTH FO RMATIQN PRESSURES Sheet Filed Dec.

ATTORNEY.

United States Patent 3,422,672 MEASUREMENT OF EARTH FORMATION PRESSURES Percy A. Payne, Tylertown, Miss., assignor to Esso Production Research Company, a corporation of Delaware Filed Dec. 27, 1966, Ser. No. 604,854 U.S. Cl. 73-151 Int. Cl. E21b 47/06 8 Claims ABSTRACT OF THE DISCLOSURE Apparatus is incorporated in a drill bit that can be extended through the lower end of the bit to seal against the earth formation to isolate the drill string bore from the annulus around the drill string. Channels in the drill BACKGROUND OF THE INVENTION This invention is directed to apparatus for measurement of earth formation pressures, and more particularly to apparatus for inclusion as part of a drill stein for measuring formation pressures at the bottom of a borehole.

During the course of drilling boreholes using the rotary drilling technique, often it is desirable to measure the pressure of a formation being penetrated by the drill string at its lowest end. To this end, usually it is necessary to pack of]? the lower end of the borehole, so that a pressure measurement can be obtained which is not affected by the weight of the drilling fluid in the borehole above the level at which the pressure measurement is conducted. Such an operation usually involves pulling the conventional drill stem and running special equipment into the borehole or using a special drill stem wherein expandible packers are incorporated on the outer surface thereof. For obvious reasons, it is desirable, if possible, to avoid the use of packers in connection with formation pressure measurements.

SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, there is provided a drill string section having a longitudinal bore therein and an annular drill bit connected to the lower end of the drill string section. An annular cavity is provided in the drill string section and the drill bit section that opens into the borehole at the lower end of the drill bit section. Formation sealing means is provided in the cavity which is adapted to move into the cavity from a normally retracted position, and is further adapted to extend from the lower end of the drill bit to contact the earth formation below the drill bit. The sealing means includes an actuating piston for moving the sealing means downwardly under the impetus of hydraulic pressure exerted thereon. A passageway means in the drill string section provides fluid communication between the longitudinal bore and the upper end of the cavity. Within the drill string section there is provided a second cavity for receiving a pressure recorder means, said cavity intersects the longitudinal bore at a position below the opening of the passageway into the bore. Annular valve means in the bore of the drill string section normally closes the openings of the second cavity and the passageway into the bore and is movable under the impetus of hydraulic pressure exerted from the upper end of the drill string section to a position whereat it opens the passageway and the second cavity into fluid communication with the drill string bore. The upper end of the valve means BRIEF DESCRIPTION OF THE DRAWING Objects and features of the invention not apparent from the above discussion will become evident upon consideration of the following detailed description of the invention taken in connection with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a preferred embodiment of the invention;

FIG. 2 is a view similar to FIG. 1 illustrating an actuated position of the apparatus;

FIG. 3 is a sectional view taken along section 33 of FIG. 1;

FIG. 4 is a cross section of the formation sealing apparatus illustrated in FIG. 1;

FIG. 5 is a sectional view taken along section 5-5 of FIG. 4;

FIG. 6 is a sectional view taken along section 6--6 of FIG. 4;

FIG. 7 is a view similar to FIG. 6 illustrating a modi fication of the invention; and

FIG. 8 is a sectional view of a pressure recorder suitable for use with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now generally to FIGS. 1, 2, and 3, there is illustrated the lower end of a drill string comprising drill collar sections 1 and 5 and a drill bit 49. The drill bit 49 is here illustrated as being of the diamond type, being generally annular in shape, and having a diamond studded matrix 53 on the outer and lower surfaces thereof. The drill collar sections 1 and 5 and the bit 49 are scrcw-threadedly connected together. A chamber 41 in the lower end of drill collar section 1 extends through the drill bit 49 and opens into the borehole at the lower face of the drill bit. A passageway 11 interconnects the upper end of the chamber 41 and the bore of the drill string section, the passageway terminating at the upper end in the bore of the drill collar 1 through passageway section 11A. The passageway 11 also communicates with the bore of the drill collar sub 1 through a passageway section 23 which is controlled by a check valve 21 that permits fluid flow only from the passageway into the bore of the drill collar. Within the chamber 41 is positioned a ring-shaped piston 43 adapted to reciprocally move in the chamber 41 and urged upwardly therein by a plurality of coil springs 51 (see FIG. 4). The ring piston 43 is connected to an annular formation sealing ring 47 by means of a plurality of connecting ribs 45. The formation sealing ring 47 terminates at its lower end in substantially a knife edge so as to cut into the formation immediately below the drill bit 49 responsive to pressure thereon exerted through the ring piston 43 and connecting ribs 45. A pair of O-rings and 56 provide a fluid seal between the ring piston 43 and the drill collar sub 1, and a pair of O- Iings 57 and 58 provide a seal between the drill bit 49 and the formation sealing ring 47. The ring piston 43 may be formed of tool steel, and the sealing ring 47 may be formed of tungsten carbide. The springs 51 are positioned between the lower end of the ring piston 43 and a shoulder in the chamber 41 so as to urge the ring piston 43 upwardly, as viewed. The sealing ring 47 may be circular in cross section as illustrated in FIG. 6, but is preferably oval in cross section, as illustrated at 47A in FIG. 7, so that a concentric core will not be cut during drilling operations.

Within the drill collar sub 1 there is positioned an annular sleeve 9, the outer surface of which conforms to the inner surface of the drill collar sub 1. An annular flange 31 at the bottom of the sleeve 9 bears against a shoulder formed by a narrowing of the bore of the drill collar sub 1 to prevent further upward movement thereof. In this position, a port 25 in the sleeve 9 is aligned with the passageway section 23 to permit flow of liquid through check valve 21. An annular nut 39 screwthreadedly engages the drill collar sub 1 within the bore of the drill collar sub and provides a reaction member for a coiled spring 36 that engages the sleeve 9 to urge the sleeve 9 upwardly. O- rings 17 and 19 above the passageway section 11A provide a. fluid seal between the sleeve 9 and the drill collar sub 1.

A pressure relief cavity 27, which is most perspicuously illustrated in FIGS. 1, 2, and 3, is threadedly ported to the exterior of the drill collar sub 1 so as to accommodate a differential pressure recorder 29: Effectively there is provided a passageway between the exterior and bone of the drill collar sub 1 that intersects the longitudinal bore of the sub 1 to accommodate the differential pressure recorder so as to measure the differential pressure between the bore and a reference pressure, such as a pressure equal to atmospheric.

In FIG. 8 there is illustrated a suitable pressure recorder for use as recorder 29. This recorder includes a housing member 71 sealed at one end by a diaphragm 73 and at the other end by an end section 91. A wall 85 acts as a journal and support for the shaft 84 of a revolving spool 89 on which is mounted a pressure recorder chart. The other end of the shaft 84 is supported by the end section 91. A pivot rod 79 is pivotally supported by a pivot member 77 between the diaphragm 73 and the wall 85. A rod 75 connects the pivot rod 79 to the diaphragm. A stylus linkage member 81 is connected to the other end of the pivot rod 79 and supports a stylus 86 which engages the chart on the spool 89. A release pin 83 is affixed to the stylus linkage member and is inserted in a recess (not shown) in the spool 89. Responsive to differential pressure across the diaphragm 73, the diaphragm will move to the right as viewed, causing the release pin 83 to be withdrawn from its slot in the spool 89, and allowing the spool to rotate. The stylus 86 engages the chart and moves to the left as viewed, thus providing an indication of the differential pressure across the diaphragm 73. When the differential pressure across the diaphragm 73 is reduced, the pin 83 will bear against the spool 89 and will fall into the recess in the spool 89 to stop the spool. An annular array of such slots can be provided so that the spool can be immediately stopped in the event that it is desired to make a number of pressure readings.

The operation of the apparatus described heretofore is as follows. During normal drilling operations the position of the components of the apparatus will be as illustrated in FIG. 1, with the piston 43 and the seal ring 47 retracted into the drill bit 49 and drill collar sub 1. When it is desired to perform, a pressure measurement, drilling operations are stopped. A wire line go-devil or retrievable plug 3, having a fishing-head 7, a cap member 13 adapted to seat on the upper end of sleeve 9, and a body member adapted to be inserted into this sleeve 9, is lowered into the well and seated on the upper end of the sleeve 9. Hydraulic pressure is then exerted through the drill string on the retrievable olug 3. The sleeve will be forced downwardly into the position illustrated in FIG. 2.. The function of port 33 at the lower end of sleeve 9 is to provide vacuum relief so that the sleeve can freely move downwardly against the coiled spring 36. When port is aligned with cavity 27 hydraulic pressure will be exerted through passage .vay 11 onto the upper end of ring piston 43 to force the ring piston and formation seal ring 47 downwardly, as illustrated in FIG. 2. The knife edge 4 lower end of the seal ring 47 will be forced into the formation immediately below the drill bit 49 so as to isolate the bore of the drill bit and the portion of the longitudinal bore of the drill collar sub 1 below plug3 from the borehole annulus and from the portion of the drill string bore above plug 3. The pressure of formation fluids thus will be exerted upwardly through the bore of the drill bit 49 and the drill collar sub 1 and through the port 25 against the diaphragm of the formation pressure recorder 29. As soon as the pressure recording has been made, the hydraulic pressure can be released so that the sleeve 9 will be forced upwardly again to the position illustrated in FIG. 1. Springs 51 will force the ring piston 43 upwardly and fluids in the passageway 11 will be forced through the check valve 21 into the bore of drill collar sub 1. Drilling operations may be resumed, and if desired, another formation pressure measurement may be made at a later time. When a round trip is made for the purpose of replacing the drill bit, or for other purposes, the formation pressure recorder can be removed and the chart recovered therefrom, and either the same recorder with another chart or a different recorder can be placed into the drill collar sub 1 for future measurements.

Having described the principle of the invention and the best mode in which I have contemplated applying that principle, I wish it to be understood that the apparatus described is illustrative only, and that other means can be employed without departing from the true scope of the invention defined in the following claims.

What is claimed is: 1. Apparatus for measuring bottom hole pressure in a borehole, comprising: an annular drill string section; a bit sub connected to the lower end of said drill 7,string section; sealing ring means in said bit sub extendible from the lower end of said bit sub to contact the lower end of said borehole responsive to hydraulic pressure exerted thereon; a channel in said drill string section from the bore of the drill string section to said sealing means; a pressure recorder opening to the interior of said drill string section; and means including valve means in said drill string section movable under hydraulic pressure from a first to a second position thereof, normally isolating the bore of said drill string section from said channel and from said recorder in said first position thereof, and in said second position thereof, permitting fluid communication between said channel and the upper end of said drill string section and between said pressure recorder and the lower end of said drill string section, said valve means being adapted to receive a removable plug to permit hydraulic pressure to be exerted thereon. 2. Apparatus for measuring bottom hole pressure in a borehole, comprising:

a drill string section having a longitudinal bore therein; an annular drill bit section connected to the normally lower end of said drill string section; an annular cavity in said drill string section and said drill bit section opening at the lower end of said drill bit section to the borehole; formation sealing means in said cavity normally retracted into said cavity and adapted to extend from the lower end of said drill bit to contact the earth formation below said drill bit, said sealing means including an extracting piston for moving said sealing means downwardly under the impetus of hydraulic pressure exerted thereon; passageway means in said drill string section opening into said longitudinal bore and into said cavity; pressure recording means; a second cavity in said drill string section for receiving said pressure recording means, said second cavity opening into said bore at a position below the opening of said passageway means into said bore;

an annular valve means insaid bore of said drill string section normally closing the opening of said second cavity and said passageway means into said bore, movable under the impetus of hydraulic pressure exerted from the upper end of said drill string section to a position whereat it opens said passageway means and said second cavity into fluid communication with said bore at the upper end of said valve means being adapted to receive a removable plug.

3. The apparatus of claim 2 wherein said annular valve means includes an annular sleeve in sliding contact with the interior of said drill string section, and port means in said sleeve means including spring means biasing said sleeve means to a position whereat said port means is isolated from said second cavity and whereat said sleeve means closes the openings of said second cavity and said passageway into said bore.

4. The apparatus of claim 3 wherein second passageway means including check valve means permits one-way fluid flow from said first passageway means to said bore at a position through said port means in said sleeve when said sleeve is in its normal position.

5. The apparatus of claim 3 further including an annular spring seat for supporting said coil spring.

6. The apparatus of claim 2 wherein at least the lower portion of said annular cavity is elliptical in cross section and the portion of said formation sealing means in said lower portion of said annular cavity is elliptical in cross section.

5 7. The apparatus of claim 2 wherein the lower end of said formation sealing means is tapered to knife edge to facilitate penetration of the earth.

8. The apparatus of claim 2 wherein said formation sealing means comprises:

10 an annular sealing member;

an annular piston member; a plurality of ribs connecting said sealing member and said piston member; and a plurality of coil springs between said ribs for engaging said bit and said piston upwardly to bias said piston.

References Cited UNITED STATES PATENTS 2,497,185 2/1950 Reistle 175-233 2,740,477 4/1956 Monaghan 175-233X RICHARD Ct QUEISSER, Primary Examiner.

JERRY W. MYRACLE, Assistant Examiner.

U.S. Cl. X.Rn

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