US3220491A

US3220491A - Core taker devices

Info

Publication number: US3220491A
Application number: US331234A
Authority: US
Inventors: Harvey O Mohr
Original assignee: Schlumberger Well Surveying Corp
Current assignee: Schlumberger Well Surveying Corp
Priority date: 1963-12-17
Filing date: 1963-12-17
Publication date: 1965-11-30
Anticipated expiration: 1982-11-30

Description

Nov. 30, 1965 H. o. MOHR 3,220,491

CORE TAKER DEVICES Filed Dec. 17, 1963 ,34 flax vey 0. Mofir 36 INVENTOR.

WM /Jdzu 49 ATTORNEY free Patented Nov. 3%, 1965 3,220,491 QGRE TAKER DEVICES Harvey 0. Mohr, Houston, Tex assignor to Sehiumherger Welt Surveying Corporation, Houston, Tex a corporation of Texas Filed Dec. 17, W63, Ser. No. 331,234 Claims. (Cl. 175-4) This invention relates to apparatus for obtaining solid samples of earth formations and, more particularly, pertains to a new and improved core-taking apparatus for obtaining a solid sample of earth formation material.

Generally, cores or samples of earth formation material are obtained by lowering a side wall sample taker assembly into the borehole to the level of the formation to be investigated. The sample taker assembly ineludes a gun body which receives a number of hollow core-taking bullets together with explosive means which are selectively operable so that the bullets may be im pelled towards and into a formation, with the hollow interior of the bullets thereby receiving the formation material. Usually, the core bullet is secured to the gun body by one or more flexible retrieving connections so that a pull, as by raising the gun body, serves to withdraw the core bullet with a formation sample from the earth formations. Thus, a formation core sample can be retrieved to the surface of the earth for examination and testing.

However, many problems are presented by the variety of formations which are encountered in sampling operations. For example, the types of formations may be generally classified as (1) soft, (2) medium, (3) firm, (4) hard, and (5) extra hard. Thus, the problems may vary from the difficulty in geting the bullet into the extra hard formations without damage to the difficulty encountered in soft formations in the withdrawal of the core bullet from the formation. To obtain core samples from the various types of formations, different types of core bullets have been designed to meet the various conditions arising. Aside from the problem of retrieving the core bullets, it is, of course, necessary to obtain a core-sample with is representative of the formation tested.

Particularly in the soft to firm formations, recovery of core bullets has been facilitated by providing the core bullet with a separable forward portion in the form of an annular cutting ring which generally has a slightly greater outer diameter than the core barrel. Thus, the ring forms an enlarged hole relative to the body of the bullet to alleviate sticking of the bullet body in the formation. When a poll is exerted on the body of the bullet, it should separate from the cutting ring thereby to leave the cutting ring in the formation. Various cutting ring attachments have heretofore been used such as the types disclosed in Patents No. 2,923,530, No. 3,101,- 797 or No. 3,072,202.

It has been found in many instances that the core bullet becomes so firmly embedded that in pulling on the bullet in the formations, the wire-retrieving connections are broken.

Accordingly, it is an object of the present invention to provide new and improved core-taking apparatus for minimizing the retrieval pull required on a core-taking bullet.

Another object of the present invention is to provide new and improved core-taking apparatus which is selfretracting from earth formations.

Still another object of the present invention is to provide new and improved core-taking apparatus which is explosively self-retracting from earth formations.

In apparatus for obtaining a core sample, in accordance with the present invention, a gun body receives one or more core-sampling bullets which may be disposed lengthwise of the gun body. The bullet is adapted to be impelled toward and into earth formations by explosive means and has a body member with a cutting ring member releasably received on its forward end. Means are provided to operate after the bullet has left a gun body and is in the earth formations to move the body member rearwardly relative to the ring member. Thus, the body member is retractable from earth formations relative to the ring member independent of the usual retrieving wire members.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view in partial cross-section of apparatus embodying the present invention for obtaining a core sample and illustrated in a well bore;

FIG. 2 is a view in cross-section of a bullet embodying the present invention;

FIG. 3 is a view in cross-section of a bullet embodying another form of the present invention;

FIG. 4 is a view in cross-section of a bullet embodying another form of the present invention.

In FIG. 1 of the drawings, there is shown a gun block or body It! disposed in a borehole l1 opposite a formation 12 of interest. Usually, borehole 11 contains a drilling mud 13.

Gun block it has a cylindrical bore 14 adjoining a bore 15 of smaller diameter, the bore 15 forming a powder chamber which terminates short of the rear surface 16 of the gun block. Chamber 15 contains an appropriate and conventional explosive propellant 17 while bore 14 receives a generally cylindical core-taking device or bullet assembly 18 constructed in accordance with the present invention. Although not illustrated, gun block 10 generally contains additional bullet assemblies in respective bores distributed along a vertical axis for the gun block.

Bullet assembly or bullet 18, near its rearward end, has an annular groove which receives an O-ring 19 to provide a fluid-tight seal for the bullet assembly 18 in the bore 14, and flexible retrieving wires 20 are secured in a conventional manner between the bullet assembly and gun block it to permit the bullet body of the assembly to be retrieved. A conventional igniter 21 suitably mounted in the block 10 may be employed to detonate the explosive propellant 17 and thereby propel the bullet is toward and into the formation.

Referring now to FIG. 2, bullet or bullet body member 18 is comprised of three parts, to wit, a forward tubular sample-receiving core part 21, an intermediate coupling part 22 and a rearward bottom part 23. Forward part 21 has a forwardly facing shoulder 24 which releasably receives a cutting ring or release member 25 and a snap ring 26 is provided to insure retention of ring 25 on the shoulder 24 of part 21. Ring member 25 has the usual, conically shaped forward surface and disposed slightly rearwardly of the forward cutting edge 27 on the tubular part 21. Ring member 25 is also slightly greater in over-all diameter than the diameter of the body portion rearwardly of the cutting ring member to reduce the area of the bullet in the formation subject to hydrostatic pressure. The purpose of the cutting ring member 25 is to provide an oversized hole so that the outer body of the bullet 18 is prevented from initimate contact with the earth formations, the ring member 25 being left embedded in the earth formations. Of course,

azasr I the precise connection and arrangement of the ring member relative to the bullet body is immaterial to the present invention so long as the ring member when in the earth formations is releasable from the bullet body. The above-described ring arrangement, however, is preferable since the forwar dend of member 21 extends beyond ring 25 and obtains a better core sample more reliably.

Tubular core part 21 also has ports 28 in its side walls and connections 29 for attachment of retrieving wire elements 20 to the bullet body.

Coupling part 22 of bullet 18 provides a bottom 30 for the tubular core part 21 and has a rearward threaded bore 31 receiving a threaded tubular extension 32 of bottom part 23. Bottom 23 has a portion 33 forming a piston which is slidably and sealingly received in gun bore 14 by means of the O-ring 19. An annualr recess 22a which faces forwardly from the bottom part is formed between portion 33 and extension 32. Slidably and sealingly received in recess 22a is a piston portion 34 of self-releasing sleeve 35. Piston 34 has inner and outer grooves receiving O-ri-

ngs

36, 37 so that the sleeve 35 is sealed in the recess while a shoulder 38 on the sleeve abuts the upper end of bottom portion 33. An O-ring 39 is provided on the intermediate part 22 to seal this part relative to sleeve 35 and chamber 40 is formed between sleeve 35 and

parts

22, 23 and is pressure sealed by the O-

rings

37, 39. Sleeve 35 has a forward end suitably slotted to accommodate connections 29 and an end surface 41 which is adjacent to the cutting ring member 25.

Coupling part 22 has .a chamber 42 in which a centrally located, downwardly facing firing pin 43 is located. Spaced from the firing pin 43 by a frangible tube 44 is a tubular hammer 45 carrying a percussion explosive cap 46, the hammer normally being held above expolosive material 48 in the extension. Hammer also carries a power train 47. The lowermost end of extension 32 i coupled by a passage 49 to the annular recess 22a below piston 34.

In operation, when the powder 17 is ignited, the bullet is accelerated from bore 14 toward and into adjacent earth formations. Snap ring 26 is displaced from its groove leaving the cutting ring 25 free, the cutting ring staying on the bullet body due to the forward movement of the bullet body. As the forward end of the bullet pentrates the formation, the cutting n'ng makes a large hole and keeps the portion of the bullet and sleeve 35 rearwardly of the ring from intimate contact with the formation.

As the bullet assembly impacts and lodges itself in the formation, it has a very rapid deceleration. The firing hammer 45 which is loosely fitted inside the tubular extension 32 has the same velocity as the bullet assembly, but as the bullet assembly decelerates from formation impact, the firing hammer 45, being a loosely fitted or a floating member, will fly forward and crush the crushable spacer 44. Theprimer cap 46, which is held in the firing hammer 47, will then strike the firing pin 43 which is held in coupling part 22. The primer cap 46 will then ignite. This ignition sets ofi the powder 47 located inside the firing hammer. The power 47 in the firing hammer will, in turn, set off the powder 48 located inside the extension 32. The powder 47 can be used also as a timing device by varying the length or diameter of the column of powder or by using powders of different burning speeds. These variations could be easily made to be a time delay device before powder 48 is ignited. The burning of the powder 48 creates a high pressure as it burns in the enclosed volume. This high pressure bleeds through the passage 49 causing a pressure build-up behind piston 34. The size of the passage 49 can also be used as a metering device. The pressure building up behind piston 34 will move sleeve 35 in such a manner with respect to the bullet assembly so as to reduce the air chamber 40 bounded by seals 39 land 37. As the chamber 40 is reduced, the sleeve 35 is forced against the release ring 25. The force pushing on the release ring is equal to area bounded by the

seals

36 and 37 times the pressure created by the burning powder 48. There is an equal and opposite force acting on the part 22 from the burning powder, and this force pulls the bullet from the formation and through the release ring 25. The pulling of the bullet from the formation breaks the seal of the differential pressure caused by the mud. With the differential pressure seal broken, the bullet can easily be pulled from the formation by the retrieving wires.

The entire assembly, with core, but less snap ring 26 and release ring 25, is returned to the surface via the wires 20 attached to the gun block 1.

The apparatus of FIG. 3 is essentially the same as the apparatus of FIG. 2 except that the explosive material 48 is coupled by an explosive delay train 47a in a passage to the main explosive 17 for the bullet.

Thus, at the same instant the powder 17 in gun block 1% is ignited, the relatively slow-burning powder 17 in part 22 is ignited. The burning speed of powder 47 and the length and diameter of the column of powder are to insure that the bullet has struck the formation before the powder 48 is ignited. Powder 48 is also a relatively slow-burning powder which burns and creates a high pressure inside the chamber behind the piston 34. The pressure build-up will move sleeve 35 in such a manner with respect to the bullet assembly so as to reduce the air chamber 40 so that sleeve 35 is forced against the release ring 25. The force pushing on the release ring is equal to the area bounded by the

seals

36 and 37 times the pressure created by the burning powder 48. There is an equal and opposite force acting on the bottom part 22 from the pressure created by the burning powder 48, and this force pulls the bullet from the formation and through the release ring 25. The pulling of the bullet from the formation breaks the seal of the differential pressure caused by the mud. With the differential pressure seal broken, the bullet can easily be pulled from the formation.

The entire assembly, with core, but less snap ring 26 and release ring 25, is returned to the surface via the fasteners 20 attached to gun block 16.

Referring now to FIG. 4, another embodiment of the present invention is illustrated which is essentially the same as the embodiment of FIG. 2. In this embodiment, instead of explosive material, the tubular extension 38 contains a glass assembly with chambers enclosing gas

pressure forming chemicals

50, 51 disposed above an elastomer shock absorber 52.

As the bullet penetrates the formation, the release ring 25 makes a large hole. As the bullet assembly impacts and lodges itself in the formation, it has a very rapid deceleration. The deceleration will cause the glass or fragile capsule assembly, being loosely fitted in the piston 9, to fly forward, crushing the crushable spacer 44. The breakable capsule assembly will then strike pin 43 which will break the capsule assembly. The capsule assembly containing two or

more chemicals

50 and 51 which, when the capsule assembly is broken, will react and form a gas when they come in contact with each other. The capsule assembly is protected from breakage due to rapid acceleration, when powder 17 is ignited, by shock-absorbing material 52.

As the chemicals 5!), 51 come in contact due to the capsule assembly being broken, a high-pressure gas is formed in their place. The high-pressure gas bleeds through the passage 49 and builds up a pressure behind piston 34. The pressure build-up will move the sleeve 35 in such a manner with respect to the bullet assembly so as to reduce the air chamber 40. As the air chamber 40 is reduced, the sleeve 35 is forced against the release ring 25. The force pushing on the release ring is equal to area bounded by the

seals

36 and 37 times the pressure created by the reacting

chemicals

50 and 51. There is an equal and opposite force acting on the part 22 from the reacting chemicals, and this force pulls the bullet from the formation and through the release ring 25. The pulling of the bullet from the formation breaks the seal of the differential pressure caused by the mud. With the differential pressure seal broken, the bullet can easily be pulled from the formation.

The entire assembly, with core, but less snap ring 26 and release ring 25, is returned to the surface via the fasteners 20 attached to the gun block 1.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A formation core-taking device adapted to be fired from a gun body into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, means operatively coupled between said body member and said ring member and responsive to gas pressures developed after ejection from a gun body for providing a force on said ring member, and means coupled to said pressure-responsive means for developing gas pressures in said body member upon impact of said device with earth formations and providing a force between said body member and said pressure-responsive means to urge said body member and ring member in opposite directions relative to one another when said ring member and forward end of said body member are embedded in earth formations.

2. A formation core-taking device including a portion adapted to be received in a gun body and fired therefrom into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, a sleeve member with a piston portion, means forming a cylinder in said body member for receiving said piston portion, said sleeve member having a forward portion for engagement with said ring member, and means in said body member for supplying gas pressure to said piston portion upon impact of said device with earth formations.

3. A formation core-taking device including a portion adapted to be received in a gun body and fired therefrom into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, a sleeve member with a piston portion, means forming a cylinder in said body member for receiving said piston portion, said sleeve member having a forward portion for engagement with said ring member, and means for supplying gas pressure to said piston portion upon impact of said device with earth formations including explosive means and impact-responsive igniter means.

4. A formation core-taking device including a portion adapted to be received in a gun body and explosively fired therefrom into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, a sleeve member with a piston portion, means forming a cylinder in said body member for receiving said piston portion, said sleeve member having a forward portion for engagement with said ring member, and means for supplying gas pressure to said piston portion after said device is in earth formations including explosive means with a time-delay explosive train adapted to be disposed in igniting relationship to explosive for firing said device from a gun body.

5. A formation core-taking device including a portion adapted to be received in a gun body and fired therefrom into earth formations about a well bore comprising: a tubular core-taking body member having a forward end, a formation-cutting ring member releasably received on said forward end, a sleeve member with a piston portion, means forming a cylinder in said body member for receiving said piston portion, said sleeve member having a forward portion for engagement with said ring member, and means for supplying gas pressure to said piston portion including chemical gas-forming means and impact responsive means for activating said gas-forming means upon impact of said device with earth formations.

References Cited by the Examiner UNITED STATES PATENTS 2,809,805 10/1957 Laval 4 2,923,530 2/1960 Fields 175-4 XR 3,072,202 1/1963 Brieger 175-4 3,101,797 8/1963 Brieger 175-4 CHARLES E. OCONNELL, Primary Examiner.

Claims

2. A FORMATION CORE-TAKING DEVICE INCLUDING A PORTION ADAPTED TO BE RECEIVED IN A GUN BODY AND FIRED THEREFROM INTO EARTH FORMATIONS ABOUT A WELL BORE COMPRISING: A TUBULAR CORE-TAKING BODY MEMBER HAVING A FORWARD END, A FORMATION-CUTTING RING MEMBER RELEASABLY RECEIVED ON SAID FORWARD END, A SLEEVE MEMBER WITH A PISTON PORTION, MEANS FORMING A CYLINDER IN SAID BODY MEMBER FOR RECEIVING SAID PISTON PORTION, SAID SLEEVE MEMBER HAVING A FORWARD PORTION FOR ENGAGEMENT WITH SAID RING MEMBER, AND MEANS IN SAID BODY MEMBER FOR SUPPLYING GAS PRESSURE TO SAID PISTON PORTION UPON IMPACT OF SAID DEVICE WITH EARTH FORMATION.