US3242987A

US3242987A - Methods and apparatus for completing wells

Info

Publication number: US3242987A
Application number: US177837A
Authority: US
Inventors: Maurice P Lebourg
Original assignee: Schlumberger Well Surveying Corp
Current assignee: Schlumberger Well Surveying Corp
Priority date: 1962-03-06
Filing date: 1962-03-06
Publication date: 1966-03-29
Anticipated expiration: 1983-03-29

Description

March 29, 1966 M. P. LEBOURG METHODS AND APPARATUS FOR COMPLETING WELLS 4 Sheets-$heet 1 Filed March 6, 1962 Mau/vce P. L ebawy INVENTOR.

BY M J/ AITO/P/VE) 1 /1 /01? ART March 29, 1966 M. P. LEBOURG 3,242,987

METHODS AND APPARATUS FOR COMPLETING WELLS Filed March 6, 1962 v 4 Sheets-Sheet 2 Maw/x6e R Zeour INVENTOR.

-March 29, 1966 M. p. LE QURG v 3,242,987

METHODS AND APPARATUS COMPLETING WELLS Filed March 6, 1962 4 Sheets-Sheet s Y Moor/ca f. Zeaary INVENTOR.

BYMjJQA ATTORNEY March 29, 1966 M. P. LEBOURG METHODS AND APPARATUS FOR COMPLETING WELLS Filed March 6, 1962 4 SheetsSheet 4 Maw/me lebau/g XNVENTOR. v ALM VJ AJ ATTO/PA/EV United States Patent Maurice P. Lebourg, Houston, Tex., assignor to Schlumberger Well Surveying Corporation, Houston, Tex., a

corporation of Texas Filed Mar. 6, 1962, Ser. No. 177,837 21 Claims. (Cl. 166-36) This invention relates to completion of wells and more particularly to methods and apparatus utilizing explosives for completing wells in a manner to increase the flow index for fluid recovery from earth formations.

In the usual well completion a jet perforating gun is lowered into a well to the required depth and fired. The resulting perforations extend through the steel casing which lines the well bore, the cement annulus in which the casing is set, and into the earth formation. Thus, relatively deep round holes are provided having a generally conical termination. The ability of such a hole or perforation to pass fluids to or from a formation is 'commonly measured in terms of a flow index.

To increase the flow index particularly for formations of relatively low permeability, hydraulic fracturing techniques are often utilized in conjunction with perforating, in both cased and uneased wells. However, the round perforations, unless a number of them are tired in the same plane, donot establish a controlled plane of fracture. In an attempt to establish such' control, a so-called pin point entry technique has been used wherein the formation is undercut or underreamed at a given depth by cut ting a 360 notch with a mechanical cutter or'an abrasive fluid jet. Hydraulic fluids are then forced under high pressures into the underreamed portions of formations to fracture them.

Either of such cutting techniques has a number of disadvantages e.g., a relatively long operating time and uncertainty of depth control. Particularly where selective fracturing by use of sealing balls is to be practiced, the creation of a slot rather than a round hole is disadvantageous. Hence, use of jet perforator in preparation for fracturing is generally preferred.

Accordingly, it is an object of the present invention to provide new and improved methods and apparatus utilizing explosives for completing wells in a manner to increase the flow index for fluid recovery from earth formations.

It is a further object of the present invention to provide new and improved methods and apparatus for developing new and improved shaped perforations in earth formations.

Another object of the present invention is to provide new and improved methods for fracturing a formation.

Still another object of the present invention is to provide new and improved methods and apparatus for perforating earth formations behind a casing in a Well bore to develop a new and improved shaped perforation in a selected preferential plane for promoting fractures in the plane when-hydraulic fluids are applied to the perforation.

In accordance with the present invention, after the drilling of the borehole and the lining of the borehole with acasing which is cemented in place,'at a selected level in the borehole, at least one perforation is developed in the formation which has a circular opening. The perforation further has a terminal portion in the formations which may be characterized as an out-of-round recess in a given plane. The perforation is then packed-01f by packer means above and below the perforation and liquids are pumped into the packed-off section of the casing under pressure sufiicient to fracture the formations behind the casing in the given plane in accord with their preferential weakening.

In accordance with the present invention, apparatus and methods are also provided to form a penetration in earth formations or the like with a generally cylindrical forward section and wedge-shaped termination. The wedge-shaped termination may be oriented to align with any selected plane. For example, with the orientation of the wedge-shaped termination in a horizontal plane, the introduction of hydraulic fracturing fluids under pressure will fracture earth formations preferentially along the horizontal plane with lower break-down pressure than would ordinarily be required by a conventional perforation. If the wedge-shaped termination is in a vertical plane, the earth formations can be preferentially fractured in the vertical plane.

The present invention also includes the steps of generating or developing a uniform perforating jet about a given axis to forma perforation with a cylindrical forward section and thereafter, generating or developing a non-uniform perforating jet along the same axis which has symmetry with respect to a given plane to form an expanding'recess in the formations along the given plane.

Apparatus in accordance with the present invention includes a shaped charge having a container element, an explosive element contained therein and a liner element therefor, the elements being assembled and disposed in a fixed spacial arrangement along a longitudinal axis through said container and the longitudinal axis corresponding to the axis for a perforating jet formed upon detonation of the shaped charge. The elements of the shaped charge which form the leading portion of the perforating jet are uniformly arranged relative to the longitudinal axis to form a uniform leading jet portion about the axis of the perforating jet. The elements of the shaped charge which form the trailing portion of the perforating jet ,are arranged non-uniformly about the longitudinal axis-but have symmetry with respect to a given plane thereby to form a non-uniform rearward jelt portion having symmetry with respect to the given p ane.

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 illustrates in longitudinal cross-section, a portion of earth formations, casing and cement and a perforation developed in accordance with the present invention;

FIG. 2 is a horizontal cross-section taken alon line 2-2 of FIG. 1;

FIG. 3 is a view in cross-section of a prior art shaped charge unit;

FIGS. 4A4C are respectively side, top and end views in cross-section of a shaped charge of the present invention;

FIGS. SA-SC are respectively side, top and end views in cross-section of another embodiment of the present invention;

FIGS. 6A-6C are respectively side, top and end views in cross-section of another embodiment of the present invention;

FIGS. 7A-7C are respectively side, top and end views in cross-section of another embodiment of the present invention;

FIG. 8 is a view in cross-section taken through a section of earth formations traversed by a well bore and illustrating apparatus for practicing the present invention;

FIG. 9 is a view in cross-section taken through a section of formations traversed by a well bore and illustrating different apparatus for practicing the present invention;

FIG. 10 is a view in cross-section taken along line 1010 of FIG. 9; and

FIG. 11 is a view similar to FIG. 9 showing other apparatus for use with the present invention.

Reference is now made to FIGS. 1 and 2, which respectively illustrate, in part, a vertical and a horizontal crosssection through earth formations 20, a casing 21, a column of cement 22, and a well bore 23. For a better understanding of the present invention, a typical perforation 24 produced by the present invention will be explained first.

As shown in FIGS. 1 and 2, perforation 24 traverses the casing 21, the cement 22 and a portion of the earth formation 20. Perforation 24 has a circular opening 27 in the casing and a forward, cylindrical entry portion 28 extending along a longitudinal axis 26. The cylindrical section 28 extends through the cement 22 and into the formations a distance indicated by the dimension a. Adjoining the cylindrical section 28 is a terminal end portion 25 which is characterized by a wedge-shaped configuration. End portion 25 extends into the formations from the cylindrical section 28 for a distance indicated by the dimension b. The wedge-shaped configuration of the terminal end portion 25 is illustrated by the fanlil re expansion of the perforation walls in a horizontal plane (FIG. 2), and the inwardly curving contraction of the perforation walls toward the central axis 26in a vertical plane.

It will immediately be obvious to those skilled in the art of fracturing that the described wedge-shaped configuration is extremely desirable for a number of reasons. For example, the round or circular entrance opening 27 in the casing 21 is less detrimental to the strength of the casing in tension than openings with similar areas but other shapes such as slots. A round or circular opening also minimizes the loss in power of the flow of the fracturing fluid therethrough. Moreover, the wedge-shaped termination 25 of the penetration 24 significantly decreases the break-down pressures necessary to fracture formations and finally, the orientation of the wedge-shaped termination 25 can be preselected to predetermine the preferred orientation of a fracture plane in the formation.

The present invention includes the steps of generating a perforating jet to form a generally cylindrical perforation with a circular entrance opening and cylindrical section, which perforation extends through the casing of a well bore and into'the earth formations, and thereafter generating a non-uniform perforating jet about the perforating axis which is symmetrical with respect to a given plane to pass through the developed cylindrical perforation and thereafter form a termination portion for theperforation in the shape of a wedge, which termination is behind the casing.

Apparatus suitable for performing this method is shown in FIG. 8 and may, for example, be a conventional shapedcharge 30 in a perforator 31, lowered into position in a casing 21. At a desired depth or level L from the earths surface, charge 30 is detonated in a well-known manner to produce a substantially cylindrical perforation or hole 32 with a conically tapered termination in a wellknown manner. Thereafter, a conventional, linear type of shaped charge 33 which produces a non-cylindrical but symmetrical jet with respect to a given plane is aligned with the cylindrical perforation 32 and detonated. Charge 33 is arranged so that its perforating jet passes through the perforation 32 and develops a wedge-shaped termination 25 in the perforation in a selected plane. In a linear type of shaped charge, of course, the explosive energy is substantially confined to a given plane and should pass through the cylindrical perforation so as not to disturb the entry configuration of the original perforation.

To position the charge 33 at the level L, the apparatus 31 may be slidably receivedwithin a friction spring assembly 34 which has a pin 35 received in a longitudinal slot 36 in the body of the perforator 31. Hence, the spring assembly 34 holds the entire apparatus in a given position in the casing 21 while the perforator 32 can be moved between the end limits of the slot 36 to position first the shaped charge 32 at level L and then position the charge 33 at level L.

Conventional selective firing systems are used to fire the shaped charges independently of one another.

In connection with the method of fracturing earth formations, reference is made to FIGS. 9-11 which illustrate a borehole 23 drilled through earth formations in a conventional manner. Thereafter, casing or pipe 2f is inserted into the bore 23 and cement 22 is pumped into the annulus between the casing and the well bore in a well-known manner. To fracture the earth formations after the cement has set, a perforating tool 37 is lowered in the casing by means of a wire line 38 in a well-known manner to a selected level. The perforating tool 37 may be of the type described previously with respect to FIG. 8 or may be of another type which will hereinafter be more fully explained. In any event, one or more perforations are developed in the casing, cement and earth formations in a given plane. The shaped charge apparatus 37 develops a cylindrical entry opening 27 in the casing and an expanding recess 25 in the earth formations along a given plane behind the casing. Following this step, as shown in FIG. 11, the casing 21 is suitably packed off by

packers

39 and 40a above and below the P an of perforations, and fracturing fluid from convention surface equipment E is pumped through a tubing 41a to the packed-01f section of the casing between the packers to induce fracture of the earth formations along the given plane of the expanding recess 25 behind the casing.

Before discussing in detail the above-mentioned apparatus 37 which is also a part of the present invention, a brief review of a conventional shaped charge will be given in order to highlight the features of the present invention. In a conventional shaped charge as Used in well bore perforating apparatus, the container 40, as shown in FIG. 3, is a hollow member which is elongated along a central or longitudinal axis 41 which is also coextensive with the axis of the perforating jet when formed. The container 40 generally has a uniform configuration about its certtral axis 41 with both a cylindrical interior wall surface 42 and an adjoining, tapered or conically shaped inner wall surface 43. Tapered Wall surface 43 extends from the cylindrical wall surface 42 to an end wall 44 in a rearward end section 45. A detonating explosive means for the shaped charge, such as a blasting cord 46, is located in a groove in the rearward section 45 for detonating a conventional explosive 47 received in the shaped charge container 4%. The explosive material 47 is fitted into the interior of the container 40 and has a forward hollow or recessed section 48 which is generally conically shaped.

A complementarily shaped, relatively thin-walled metallic liner 49 constructed of copper, for example, is fitt d? into the hollow section 48 of the explosive and the me lic liner and container thereby enclose the explosive 47.- When the explosive is detonated by the blasting cord 46, the container 40 which is constructed of lead, for example, contains the explosive pressures for a time sufficient for the pressures to form a perforating jet travelling along axis 41, the pressures causing a uniform collapse of the liner 49 toward the axis 41. The collapse of the liner is inwardly toward axis 41, the apex 50 of the liner being, projected in the forward or leading end of the jet andl the base 51 of the liner being projected in the rearward or; trailing end of the perforating jet as the jet travels in a; forward direction along axis 41. The jet is continuously,

formed by the progressive uniform collapsing of the liner collapsed on the axis 41 to form the end of the jet. Because the liner element, explosive element and container element have a uniform configuration about the central axis 41 of the charge, the perforating jet is substantially cylindrically shaped and forms a substantially cylindrical perforation in the perforated media. 7

With the foregoing description of a conventional shaped charge in mind, the present invention will be more clearly understood. Turning now to FIGS. 4A-4C, the basic elements of a shaped charge are illustrated, namely a hollow container element 52, and explosive element 53 and liner element 54. In this embodiment of the invention, the liner 54 and the explosive 53 are disposed uniformly about a central axis x of the charge. For convenience of description, Cartesian coordinate axes x, y and z are used in the drawings, the axes intersecting at an origin 0. Axes x and y, x and z, y and 2 respectively define perpendicular planes xy, xz and yz which intersect at the origin 0.

The container element 52 is formed with a rearward section 55 having a conical, uniform configuration about the central axis x and a forward section 56 with a nonuniform configuration about the central axis x. The

sections

55 and 56 of the container meet in the plane yz. The forward section 56 is formed with an elliptical outer surface 53 (FIG. 4C) and a cylindrical inner surface 59. Thus, the wall thicknesses of the container in the forward section 56 are greater in plane xz than in perpendicular plane xy. The ditferent thicknesses are illustrated more clearly in FIG. 4C where, in plane xy, the wall thickness is thin compared to the thickness of the wall in plane xz; Portions of'the liner 54 and the explosive 53 in the container are arranged to extend into the forward section 56 of. thecontainer. More particularly, the base 60 of the liner is roughly spaced a distance from the intersection origin 0 equal to about one-third of the height of the liner taken along the axis x from its base to its apex.

When the charge is detonated and the shock wave enters container section 56, the increased wall thickness of the container section in the plane xz contains the generated explosive forces more effectively than the thinner wall sections in-plane xy so that the speed of the liner collapse in the plane xz is increased relative to the speed of the liner collapse in the plane xy. The differential speed of liner collapse results in the trailing portion of the perforating jet being developed non-uniformly but symmetrical relative to a given plane.

The principle of operation of this charge is as follows: When the explosive 53 is detonated at its rearward end by a blasting cord (not shown), the explosive or shock wave travels forwardly. Collapse of the liner 54 occurs first at its apex which is propelled outwardly to form the leading end of the perforating jet. As the jet is propelled outwardly from the container, the shock wave of the explosive continues to symmetrically collapse the liner into the jet until the explosive wave reaches the plane yz whereupon the liner is non-uniformly collapsed, the speed of the liner collapse in the planes xz and xy being dissimilar causing the remaining trailing portion of the jet to form in a somewhat oval shape which is symmetrical about the planes xy and xz.

As the thus-formed jet enters into the formation, the leading portion of the perforating jet penetrates the casing, the cement, and the formations in that order, and in so doing, a hole or perforation is produced with a cylindrical opening and a cylindrical forward section. The rearward or trailing section of the jet entering into the cylindrical perforation follows through the cylindrical section and because of the oval configuration cuts into the formations along a preferential plane to form a wedge-shaped terminal section,

The foregoing description of FIGS. 4A-4C refers to a shaped charge for producing a perforation with a wedgeshaped termination by means of altering the wall configurationof a portion of a shaped charge container in a selected manner. The same type of perforation may be produced by altering the'configuration of the explosive.

Referring now to FIGS. SA-SC, in this embodiment of the invention, a hollow container 61 has a rearward section 62 which has a generally conical interior wall surface about an x axis and a forward section 63 which has a generally elliptical interior wall surface about the x axis, the major dimension of the elliptical wall surface being in the plane xz and the minor dimension of the elliptical wall surface, in the plane xy. The wall thicknesses of the container are generally uniform throughout.

A generally conical liner 66 is fitted into the forward open end of the container 62 and has its base 67 conformed to the inner elliptical surface of the forward portion 63 of the container. A conventional explosive 68 is disposed between the liner 66 and interior wall of the container 61. Portions of the liner and the explosive are arranged to extend into the elliptical forward section 63 of the container. More particularly, the base 67 of the liner is roughly spaced a distance from the intersection origin 0 equal to about one-third of the height of the liner taken along the axis x from its apex to its base.

This, the forward portions of the explosive 68 and the base 67 of the liner which extend beyond the plane yz are non-uniformly disposed about the axis x with more explosive effectively disposed about t-he'linei' along the z axis than is disposed about the liner along the y axis.

Hence, when the charge is detonated, the liner portion extending from the apex to the plane yz will form the leading end or portion of a perforating jet which is uniformly disposed about the perforating axis and substantially cylindrical in shape. As the jet is propelled outwardly from the container, .the detonating explosive continues the collapse of the elements of the liner into the jet and at the intersection of the plane yz, the speed of the liner collapse along axes y and 2: becomes dissimilar due to the non-uniform explosive load causing the trailing end of the jet to have a somewhat oval configuration with symmetry about a given plane xz.

As the ,thus-forme'd jet enters into the formation, the leading portion of the per-forating jet penetrates the casing, the cement and the formations in that order and in so doing, the perforation produced has a cylindrical open;

ing and a cylindrical forward section. The rearward or trailing section of the jet entering into the cylindrical perforation follows through the cylindrical section and because of its oval. configuration, cuts into the formations to form the wedge-shaped cavity in the plane xy.

Referring now to FIGS. 6A-6C, a modification of the I 72 are provided on diametrically opposite sides of the forward end of the container 70 along thez axis to form an oval configuration for the trailing portion of the jet. Specifically, explosive means 72 are blasting cord members attached to the forward, outer surface of the container 70 along the axis z. The length of the blasting cord members 72 as well as their composition is adjusted to delay the time of detonation on the z axis until after the main blasting cord 76 detonates the explosive 74' in the container. The explosive 74 in the container, when detonated by blasting cord 76, causes the conical liner 75 at its apex and initial forward portions to form the leading portion of a per-forating jet which is uniform about the perforating axis and substantially cylindrical. The later arriving detonation of the blasting cord members 72 near the base 73 of the liner, causes the elements of liner along the axis z to collapse faster than the elements of liner along the axis y so' that the speed of thecollapse of the elements in their respective planes is dissimilar to form an oval jet portion.

As the thus-formed jet enters into the formation, the

leading portion of the perforating jet penetrates the cas-' ing, the cement and the formations in that order, and in so doing, the perforation is produced with a cylindrical opening and a cylindrical forward section. The rearward or trailing section of the jet entering into the cylindrical perforation follows through the cylindrical section and because of the oval configuration, cuts into the formation to form the wedge-shaped terminal section.

The desired perforation can also be developed by altering any two elements of the liner, for example, the case and explosive configurations. As shown in FIGS. 7A- 7C, a container 80 has a rearward section 81 with a uniform configuration about the x axis to point 79 on the containers and has a forward section 82 with a uniform elliptical configuration about the x axis. The base 83 of the liner and portions of the explosive 84 are disposed in the forward section 82 a distance from the origin equal to about one-third of the height of the liner taken along its x axis from its apex to its base. I Rearwardly of the origin a of the axes, the liner is conically shaped while forwardly of the origin 0, the liner is elliptically shaped. The explosive 84 in the container has a rearwardly symmetrical portion 85 and a forward elliptical" section 86. Thus, when the chargejis detonated, the jet is formed from the apex of the liner and is propelled outwardly from the container to form a perforating jet with a forward section with a substantially cylindrical configuration. At the plane yz, the elliptical configuration of the case, explosive and liner cause a differential speed of collapse of the liner along perpendicular axes y andz to form a trailing portion of the jet with an oval configura-ton. The jet acts to form a perforation with a cy-lindr-ically shaped forward section followed bya terminal wedge-shaped section similar to that described previously.

From the foregoing description it will be appreciated that, in accordance with the present invention,.a single shaped charge is provided to sequentially produce a perforation having a generally cylindrical entry section and a terminating, wedge-shaped section. In the shaped charge, a portion of the charge is arranged to produce a perforating jet having a forward section with a substantially cylindrical configuration and a trailing section with an oval configuration. In this trailing section, the velocity or energy in a given axial plane is increased relative to the energy of the jet in a perpendicular axial plane to provide a desired wedge-shaped configuration in the resulting perforation.- It should be appreciated that the characteristic of a shaped charge to provide a perforating jet with selected cross-sectional configurations at any point along its length is determined by an interaction between the container element configuration, the explosive element configuration, and the liner element configuration.

Each of these element configurations may independently be altered to provide the desired cross-sectional config uration. As the above description clearly illustrates, the shape of the perforating jet along its length can be altered by a given change in any of the recited element configurations. Moreover, two or more of the recited element configurations can be altered in a complementary manner to provide the described perforating jet. With this understanding, it will be appreciated that the shaped charge of the present invention which provides a perforation with a wedge-shaped termination is not limited to a particular form of a given element since the three recited elements can independently be changed so as to provide the desired perforation.

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 for the purpose of increasing the production of a fluid therefrom which includes the steps of: developing in a well bore extending through earth formations a penetrating force uniform about and traveling along an axis to penetrate a well bore wall and provide a generally-circular opening therein, and following said penetrating-force with an enlarging force effective within the penetratedearth formations in a plane intersecting said axis to provide an out-of-round recess beyond said circular opening having symmetry with respect, to said plane thereby to weaken the formations and to increase the area subjected to parting forces when hydrostatic pressure is applied, and then applying a liquid under hydraulic pressure through the opening to the recessed portion of the formation sufficient to fracture the formation.

2. A method of treating earth formations behind a casing cemented in a well bore for the purpose of increasing the production of a fluid therefrom which includes the steps of: developing in the casing extending through earth formations a penetrating force uniform about and traveling along an axis to penetrate the casing wall and provide a generally-circular opening therein, and following said penetrating force with an enlarging force effec tive within the penetrated earth formations in a plane intersecting said axis to provide an out-of-round recess beyond said circular opening having symmetry with respect to said plane thereby to weaken the formations and to increase the area subjected to parting forces when hydrostatic pressure is applied, and applying a liquid under hydraulic pressure to the recessed portions of the formation sufficient to fracture the formation.

3. A method of treating earth formations behind a casing cemented in a well bore for the purpose of increasing the production of a fluid therefrom which includes the steps of: developing in the casing extending through earth formations a penetrating force uniform about and traveling along an axis to penetrate the casing wall and provide a generally-circular opening therein, and following said penetrating force with an enlarging force effective within the penetrated earth formations in a plane intersecting said axis to provide an expanding wedge-shaped recess beyond said circular opening having symmetry with respect tov said plane thereby to weaken the same and to increase the area subjected to parting forces when hydrostatic pressure is applied, and then applying a liquid under hydraulic pressure to the wedge-shaped portion of the formation sufficient to fracture the formation.

4. A method of treating earth formations behind a casing cemented in a well bore for the purpose of increasing the production of a fluid therefrom which includes the steps of: developing in the casing extending through earth formations a penetrating force uniform about and traveling along an axis to penetrate the casing wall and providea generally-circular opening therein, and following said penetrating force with an enlarging force eflective within the penetrated earth formations in a plane intersecting said axis to provide a wedge-shaped recess beyond said circular opening having symmetry with respect to said plane thereby to weaken the earth formations and to increase the area subjected to parting forces when hydrostatic pressure is applied, packing off the casing above and below the said cylindrical opening, and then applying a liquid under hydraulic pressure to the packed off section of the casing and to the recessed portion of the formation sufiicient to fracture the formation.

5. A method of treating earth formations behind a along a given axis and having uniform action aboutsaid axis for providing at least one generally round opening through the casing and also providing a second explosively derived penetrating jet along said axis having penetrating energy concentrated in a given plane and sized to pass relatively unhindered through said cylindrical opening. and

expand along said plane to form an out-of-round recess along said given plane behind said casing thereby to weaken the formations and to increase the area subjected to parting forces when hydrostatic pressure is applied, and then applying a liquid under hydraulic pressure to the recessed portion of the formation sufiicient to fracture the formation.

6. A method of perforating earth formations along a well bore comprising the steps of: providing at a selected level in a well bore a penetrating force arranged to provide a generally cylindrical penetration in the earth formations along a given axis with a generally round opening on the well bore wall, and also providing along said given axis, an explosively derived perforating jet with penetrating'energy concentrated in a given plane and sized to pass unhindered through said cylindrical opening thereafter to explan along said plane thereby to form an out-of-round recess along a given plane in the earth formations.

7. A method of perforating-earth formations along a well bore comprising the steps of: providing at a selected level in-a well bore, a first explosively derived perforating jet with penetrating energy generally uniformly generated about and along a given axis to form a generally cylindrical penetration in the earth formations witha generally round opening in the well bore wall, and also providing along said given axis, a second explosively derived perforatingjet complement with penetrating energy concentrated in a given plane and sized to pass unhindered through said round opening thereafter to expand along said plane thereby to form an out-of-round recess along a given plane in the earth formations.

8. A method of perforating earth formations along a well bore comprising the steps of: developing a first perforating jet with penetrating energy generally uniformly generated about and along a given axis at a selected level in a well bore to form a generally cylindrical penetration in the earth formations with a generally round opening in the well bore wall, and also developing a second perforating jet complement along said given axis with penetrating energy generally concentrated in a given plane, said second perforating jet being sized to pass substantially unhindered through said round opening thereafter to expand along said plane thereby to form an out-fround recess along a given plane in the earth formations.

9. A method of perforating earth formations along a well bore comprising the steps of: providing at a selected level in a well bore a first explosively derived perforating jet with penetrating energy generally generated uniformly about and along a given axis to form a generally cylindrical penetration in the earth formations with a generally round opening in the well bore wall, and also providing along said given axis, a second explosively derived perforating jet complement with penetrating energy concentrated to form an oval cross-section and sized to pass substantially unhindered through said round opening thereafter to expand along said plan-e thereby to form an out-of-round recess along a given plane in the earth formations.

10. A method of perforating earth formations behind a casing cemented in a well bore comprising the steps of: providing, at a selected level in the casing, a generally cylindrical perforation in the casing, cement and earth formations, and also providing along said given axis, an explosively derived perforating jet with penetrating energy concentrated to form an oval cross-section and sized to pass substantially unhindered through the round opening of said cylindrical perforation thereafter to expand along said plane thereby to form an out-of-round recess in a given plane in said earth formations behind said casing.

11. A method of perforating earth formations behind a casing cemented in a well bore comprising the stepsof: providing, at a selected level in the casing, a first explosively derived perforating jet along a given axis with a cylindrical configuration to form a generally cylindrical perforation in the casing, cement and earth formations,

and also providing along said given axis, a second explosively derived perforating jet complement with perforating energy concentrated to form an oval configuration and sized to pass substantially unhindered through the round opening of said cylindrical perforation thereafter to expand along said plane thereby to form an outof-round recess in a given plane in said earth formations behind said casing.

12. A method of perforating earth formations behind a casing cemented in a well bore comprising the steps of: providing, at a selected level in the casing, a first explosively derived perforating jet along a given axis with a cylindrical configuration to form a generally cylindrical perforation in the casing, cement and eanth formations, and also providing along said given axis, a second explosively derived perforating jet complement with perforating energy concentrated to form an oval configuration and sized to pass unhindered through the round opening of said cylindrical perforation thereafter to expand along said plane thereby to form a wedge-shaped recess in a given plane in said earth formations behind said casing.

13. Shaped charge apparatus for producing a perforation having a-characteristic round opening and an out-0fround recess in a given plane in a media comprising, means for developing an explosively generated perforating jet having a forward portion with substantially uniform configuration about a perforating jet axis and including means for preferentially forming the rearward portion of said perforating jet with a substantially oval configuration.

14. Shaped charge apparatus for producing a perforation having a characteristic round opening and an out-ofround recess in a given plane in a media comprising: a hollow shaped charge container element, an explosive element in said container element having a recessed portion, and a liner element fitted into said recessed portion of said explosive element, first portions of said elements being constructed and arranged for producing a forward portion of a perforating jet with a substantially uniform configuration about a perforating axis, second portions of said elements being constructed and arranged for producing the rearwand portion of said per-forating jet with non-uniform configuration about the perforating axis which has symmetry with respect to a plane which intersects the perforating axis.

15. The device of claim 14 wherein said explosive element of said second portions is increased in one plane relative to a perpendicular plane where said planes intersect with said perforating axis.

16. The device of claim 14 wherein said liner element of'said second portions is symmetrically distorted in one plane relative to a perpendicular plane where said planes intersect with said perforating axis. 7

17. The device of claim 14 wherein said container element of said second portions is symmetrically distorted in one plane relative to a perpendicular plane where said planes intersect with said perforating axis.

18. The device of claim 14 wherein said elements of said first portions are uniformly distributed about said perforating axis, and where at least one of said elements of said second portions is symmetrically distortedin one plane relative to the corresponding portions of said one element in a perpendicular plane where said planes intersect with said perforating axis.

19. Shaped charge apparatus for producing a perforation with a characteristic cylindrical opening and an outof-round recess along a given plane in a media comthe perforating jet, second means for altering the velocity of collapse of the portion of said liner which provides the rearward portion of a perforating jet.

20. Shaped charge apparatus for producing a perforation having a characteristic round opening and an out-ofround recess in a given plane in a media comprising: a hollow shaped charge container element, an explosive element in said container element having a recessed portion, and a liner element fitted into said recessed portion of said explosive element, said container element having a rearward section with substantially uniform configuration about a longitudinal axis through said container. element, and a forward section with increased wall thicknesses in one plane relative to the wall thickness in a perpendicular plane where said planes intersect said longitudinal axis, said explosive element and liner element having portions in said rearward section to form a forward portion of a perforating jet with a uniform configuration and remaining portions in said forward section to form a trailing portion of a perforating jet with an oval cross-sectional configuration.

21. Shaped charge apparatus for producing a perforation having a characteristic round opening and an out-ofround recess in a given plane in a media comprising: a hollow shaped charge container element, an explosive element in said container element having a recessed portion,

' and a liner element fitted into said recessed portion of said explosive element, said container element having a rearward section with substantially uniform configuration about a longitudinal axis through said container element and a forward section with a uniform but oval configura! tion, said explosive element and liner element having portions in said rearward section to form a forward portion of a perforating jet with a uniform configuration and remaining portions in said forward section to form a trailing portion of a perforating jet with an oval cross-sectional configuration.

References Citedby the Examiner UNITED STATES PATENTS 2,513,233 6/1950 Byers 102-24 2,587,243 2/ 1952 Sweetrnan 102-24 2,630,182 7 3/1953 Klotz 102-20 2,764,937 10/1956 Schlumberger 102-20 2,837,995 6/1959 Castel 89-1 2,919,646 1/1960 Foster 102-20 2,947,252 8/ 1960 Lindsay 102-24 2,980,018 4/ 1961 Turechek 102-24 2,986,214 5/1961 Wiseman et al. 89-1 3,013,491 12/1961 Poulter 102-20 3,029,732

4/1962 Greene 89-1 BENJAMIN A. BORCHELT, Primary Examiner.

ARTHUR M. HORTON, SAMUEL FEINBERG,

' Examiners.

Claims

1. A METHOD OF TREATING EARTH FORMATIONS IN A WALL BORE FOR THE PURPOSE OF INCREASING THE PRODUCTION OF A FLUID THEREFROM WHICH INCLUDES THE STEPS OF: DEVELOPING IN A WELL BORE EXTENDING THROUGH EARTH FORMATION A PENETRATING FORCE UNIFORMS ABOUT AND TRAVELING ALONG AN AXIS TOPENETRATE A WELL BORE WALL AND PROVIDE A GENERALLY-CIRCULAR OPENING THEREIN, AND FOLLOWING SAID PENETRATING FORCE WITH AN ENLARGING FORCE EFFECTIVE WITHIN THE PENETRATED EARTH FORMATIONS IN A PLANE INTERSECTING SAID AXIS TO PROVIDE AN OUT-OF-ROUND RECESS BEYOND SAID CIRCULAR OPENING HAVING SYMMETRY WITH RESPECT TO SAID THEREBY TO WEAKEN THE FORMATIONS AND TO INCREASE THE AREA SUBJECTED TO PARTING FORCES WHEN HYDROSTATIC PRESSURE IS APPLIED, AND THEN APPLYING A LIQUID UNDER HYDRAULIC PRESSURE THROUGH THE OPENING TO THE RECESSED PORTION OF THE FORMATION SUFFICIENT TO FRACTURE THE FORMATION.