US3270668A

US3270668A - Well-treating apparatus

Info

Publication number: US3270668A
Application number: US421896A
Authority: US
Inventors: Silver Bernard
Original assignee: Atlantic Research Corp
Current assignee: Atlantic Research Corp
Priority date: 1964-12-29
Filing date: 1964-12-29
Publication date: 1966-09-06
Anticipated expiration: 1983-09-06

Description

B. SILVER 3,270,668

Sept 6, 1966 34 35 Ma 24 5/ 52 l3 g INVENTOR /0 BERNARD SILVER ATTORNEY United States Patent O 3,270,668 WELL-TREATING APPARATUS Bernard Silver, Alexandria, Va., assignor to Atlantic Research Corporation, Fairfax County, Va., a corporation of Virginia Filed Dec. 29, 1964, Ser. No. 421,896 Claims. (Cl. 102-20) This invention relates to well-treating apparatus and, more particularly, to means for generating high-pressure gas and high flow rate for improving oil, gas or water recovery.

In the art of oil, gas and water recovery, it is a common problem for the quantum of recovery to be reduced considerabyl due to the presence of sedimentation, petroleum wax, or other foreign matter. It is also necessary to provide fissures or cracks in the earth formation tionin order to effect flow of the desired recoverable substance into the well from which it can be extracted. Several methods have been employed in the past to overcome these obstacles, however, each of these methods has distinct disadvantages which are overcome by the subject invention.

The most common fracturing and cleaning method employs a liquid under pressure, this being known as hydrofracting. Hydrofracting requires supplying large quantities of water under high pressure down the well and into the earth formation. Attaining the high pressures and/or high injection rates required necessitates the use of expensive and large, relatively non-portable equipment as well as the availability of several thousand gallons of water. The fracturing fluid must be pumped down the well in tubing and applied at the desired depth through perforations in the well tubing or through the bottom of the tubing which results in highfriction loss with concomitant reductions in injection rates and pressures and often results in failure to fracture or in inadequate fracturing or cleaning.

Another common and well-established method is the use of an explosive, such as nitroglycerin; however, in order to avoid fracture and destruction of the well tubing, it is necessary to raise the tubing above the level at whihc the explosive is to be detonated. This process is time-consuming and expensive. Furthermore, the need to maintain nitroglycerin or other explosives in the field provides logistics problems due to the dangerous nature of the explosives.

A third method which has been recently adopted is the use of containers of pressurized carbon dioxide, the containers having a heating element therein and a burst diaphra-gm closing off one end of the container. The container is lowered into the well and the heating element is energized causing heating of the carbon dioxide and an increase in internal pressure. At a predetermined pressure, the burst diaphragm fails and the pressurized CO is expelled into the well. The results received with this method have been generally unsuccessful thus accounting for its limited acceptance.

It can be seen, therefore, that there is a substantial need for Well-treating apparatus which effectively removes the foreign matter in the earth formation preventing successful recovery of the desired product (oil, gas, or water) and which can fracture the earth formation when desired. This apparatus should be easily portable, inexpensive, both in manufacturing and operation, and reliable.

Accordingly, it is one object of the present invention to provide a well-treating apparatus capable of reliably supplying a prescribed fluid pressure and flow rate at a desired depth in the well.

It is another object of the present invention to provide a well-treating apparatus which is portable, inexpensive to manufacture, easy and inexpensive to operate, and relatively safe to use and store.

Further objects and attendant advantages of the present invention will become better understood from the following description and accompanying drawings.

Briefly stated, this invention in one form provides a neutral-thrust gas generator comprising a tubular cylindrical casing, a solid propellant grain mounted within the casing, ignition means, and removable apertured means secured at both ends of the casing. Additionally, a diaphragm is provided to obturate the apertures at both ends of the casing in order to prevent moisture and foreign particles from entering the interior of the gas generator. The diaphragm also assists in providing accurate means for permitting establishment of a predetermined pressure within the gas generator casing.

The gas generator is lowered into the well to the desired depth at which time the ignition means is energized to effect ignition of the solid propellant grain. Burning of the grain rapidly produces gaseous combustion products which are maintained within the casing by the diaphragms until a predetermined pressure is attained. Upon attainment of the predetermined pressure, the diaphragms at both ends of the casing are ejected and the combustion products rapidly flow through both apertured means into the well and the surrounding earth formation. The gas generator can be reused by simply removing one or both apertured means and reloading the casing.

In the accompanying drawings, in which identical parts are denoted by the same reference numerals,

FIGURE 1 is a sectional view of a gas generator formed in accordance with one embodiment of this invention.

FIGURES 2, 3, and 4 are sectional views of solid propellant grains illustrating various internal surface configurations,

FIGURE 5 is a sectional view of one end of a gas generator formed in accordance with a second embodiment of this invention,

FIGURE 6 is a sectional view of one end of a gas generator formed in accordance with a third embodiment of this invention,

FIGURE 7 is a sectional view of one end of a gas generator formed in accordance with a fourth embodiment of this invention,

FIGURE 8 is a sectional view of one end of a gas generator formed in accordance with a fifth embodiment of this invention.

With reference to the drawings and, more particularly, FIGURE 1, there is illustrated a gas generating welltreating apparatus 10 comprising a tubular cylindrical casing 12 having a combustion section 13, a solid propellant grain 14 mounted centrally within the combustion section 13, a pair of apertured means or inserts 16, 18, one being mounted at each end of the casing 12, and diaphragms 20, 22, for obturating each of the

inserts

16, 18, respectively. Ignition means 24 is located within the grain 14 in order to ignite the grain upon command.

The casing 12 may be made of any suitable material which can withstand the pressures and temperatures to which it will be subjected. For example, the casing is made preferably of steel or aluminum tubing, however, other materials such as glass fiber or reinforced plastics can also be employed.

If the material used for the casing 12 so requires, and if the particular burning rate of the grain makes it necessary, an insulator liner 26 may be located between the grain 14 and the casing. The liner an be an independent member or molded directly on theouter surface of the grain 14. Examples of suitable insulator material are phenolicchamber, and the duration of gas generation.

impregnated asbestos, phenolic-impregnated paper and plastic-reinforced cloth.

In order to fracture the earth formation it is necessary to supply high pressure fluid at a high flow rate. Consequently, it is necessary to design the propellant grain 14 such that it burns rapidly thus producing the desired pressure and flow rate. In addition, it is necessary to keep the costs as low as possible. One type of grain that can produce the desired result is the conventional internalburning grain such as illustrated in FIGURE 1. The particular configuration of the internal surface is determined by the characteristics of the particular propellant used and the desired performance requirements. Examples of various internal configurations are the straight cylindrical grain 14a shown in FIGURE 1, the ruciform 14b shown in FIGURE 2, the star 140 shown in FIGURE 3, and the wagon wheel 14d shown in FIGURE 4. These are merely four examples of internal-burning grains and it is not intended to imply that they are the only configurations that can be used.

The particular propellant formulation can be chosen from the many well-known moldable, castable or extrudable formulations, for example, double-base, e.g., nitrocellulose plasticized with nitroglycerin or other nitrated liquid plasticizer; composite propellants comprising an organic binder, e.g., polyvinyl chloride, polyurethane, polyether ,polysulfide (Thiokol), polybutadiene acrylic acid, etc., and

an oxidizer, e.g., ammonium and alkali metal nitrates and perchlorate, metal peroxides, etc.

Because of the simplicity of grain design, the grain can be'manufactured by any of the conventional propellant molding methods, however, the grain is particularly adaptable to being manufactured by a continuous extrusion process' wherein agrain of continuous length is extruded and cut to the desired length. The finished grain 14 is then cartridge-loaded into the casing 12.

In order to restrict burning to the internal surface of the grains 14 a pair of resilient

annular inhibitor members

28, 30 are placed at the ends of the grain and are held in a partially compressed state by the

inserts

16, 18 as described below. The

annular members

28, 30 additionally serve as as seal between the grain 14 and the inserts and restrict the flow of combustion products to an axial direction thus preventing the flow of the combustion products across the ends of the grain and around the outer surface thereof. The

annular members

28, 30 can be fabricated from any heat-resistant resilient material. Selection of a particular material depends upon many factors such as the environ- .mental temperatures in which the gas generator will be stored, the operating temperature within the combustion Because natural and synthetic rubbers are poor thermal conductors and because the operating time of the gas generator is very short, almost any of these rubbers can be used to .fabricate the

annular members

28, 30. The preferred materials are the resilient silicon rubbers which are well recognized in the art and have been used extensively in making gaskets and the like. The annular members are attached to the ends of the grain with a suitable heatresistant adhesive. Many well-known adhesives are available for attaching rubber to plastics and other materials. The epoxy adhesives are a particular suitable class for this purpose.

The discussion above concerns an internal-burning grain. It should be noted that this invention is not limited to internal-burning grains but can be effectively practiced with other grains such as combination end-internal-burning grains or internal-end-external-burning grains. If it is desired to use an end-internal-burning grain, the

annular inhibitor members

28, 30 are not employed thus permitting the end faces of the grain 14 to become burning surfaces. If the grain is very accurately manufactured so as to form a tight fit within the casing 12, or the insulator liner 26 if used, it may not be necessary to inhibit the outer surface of the grain since flow of hot gases around the outer surface would be prohibited by the tight fit. A bsent such a tight fit, however, it would be necessary to inhibit the outer surface of the grain through the use of an inhibitor sleeve (not shown) made of any conventional inhibiting materials such as polysulfides, polyepoxides, alkyne resins, etc. The inhibitor may have inorganic fibers such as glass and asbestos or organic fibers such as cord, rayon, nylon, or combinations thereof incorporated therein as a reinforcing member. The means for applying the inhibitor to the grain are well-known in the propellant and rocket art and since it does not comprise this invention, it will not be explored further.

If it is desired to have burning along all the exposed surfaces of the grain 14, i.e., internal surface, end faces and external surface, the

annular members

28, 30 are not employed and the grain is formed so as to have a fit within the casing which permits the flow of hot gases around the outer surface of the grain. When the grain is permitted to burn on its external surface it may be necessary to'insulate the internal surface of the casing 12 through means of a liner 26 such as was described above.

The

inserts

16, 18 serve to position the grain 14 in place and to provide

apertures

31, 32 through which the combustion products exhaust into the external atmosphere contiguous to each end of the casing 12. The apertures are sized so as to provide the desired pressure within the combustion section 13, the particular internal pressure being dictated by the particular application of the gas generator and the particular propellant used. For example, the pressure must be sufficiently higher than the ambient pressure to eflfect the desired degree of fracturing and/ or cleaning. Furthermore, the propellant burning rate varies directly with the pressure and, therefore, the

apertures

31, 32 are sized to provide the pressure required for a desired burning rate. The

apertures

31, 32 are identical in size and shape and are oriented in exactly opposed directions in order to avoid the generation of a positive resultant thrust.

The

inserts

16, 18 are fixedly mounted within the easing 12 and held in place by expandable retention means 33, 34, such as snap rings. The retention means 33, 34 are reecived within

annular grooves

36, 38 provided in the outer surface of the

inserts

16, 18, respectively. An annular recess is provided in the inner surface of the casing 12 adjacent each end thereof and is spaced from end so as to-eoincide with the

grooves

36, 38 of the insert when the inserts are properly located within the casing 12. The recesses are denoted as 40, 42. The

inserts

16, 18 are slipped into place and when they are in the proper position the retention means 33, 34 expand and concurrently seat within the grooves 26, 28 and their corresponding recesses 40, 42 respectively. The retention means lock the inserts in place and prevent their removal thus making the gas generator tamper entering the interior of the casing 12 and in order to effect build-up of a predetermined pressure within the casing 12 when the grain 14 is ignited, the apertures 31,

32 of the

inserts

16, 18 are obturated by diaphragms 20,

22, respectively. The diaphragms, which may be in the form of metal discs, are fixedly mounted adjacent the exterior surface of the

inserts

16, 18. This is accomplished by providing

annular recesses

48, 50 in the outer surface of the

insents

16, 18, respectively, the

recesses

48, 50 communicating with the

apertures

31, 32 as shown in FIGURE 1. The recesses circumscribe the apertures such that when the diaphragms 20, 22 are placed therein, the

apertures

31, 32 are completely obturated. In order to hold the diaphragms in place, the ends of the inserts are .coldrolled causing the insert material immediately adjacent the diaphragms to flow over the peripheral surface of the diaphragms thus retaining them in place. The pressure within the casing is controlled by the resisting strength of the diaphragms. This strength is a function of the diaphragm material, the diaphragm size, and the amount of insert material rolled over the diaphragm periphery.

One or more conventional igniter means, 24, comprising a squib and pyrotechnic igniter, are located Within the propellant grain 14. The igniter means 24 is supported within the grain by a plug 51 made of inert material such as foamed polyurethane or foamed polystyrene. Igniter leads 52 are led to the exterior of the casing through an orifice 54 provided in one diaphragm 20. To avoid leakage through the orifice 54 appropriate sealing between the leads 52 and the diaphragm 20 is required such as is indicated at 55.

The gas generating well-treating apparatus is operated as follows. The gas generator 10 is lowered into the well to the desired depth at which time the igniter means 24 is energized by use of any conventional electrical source (not shown), such as an electric storage battery. Energization of the igniter means 24 causes ignition of the propellant grain 14 which, in turn, effects generation of high temperature combustion products. The pressure within the casing 12 increases to a predetermined value at which time the diaphragms 20, 22 are ejected. The combustion gases then flow through the

apertures

31, 32 and into the well. Because the

apertures

31, 32 are equal in design and cross-sectional area there will be no result-ant thrust, thus avoiding propulsion of the gas generator 10.

A second embodiment of this invention, illustrated in FIGURE 5, employs inserts one of which is shown at 60, which are removably mounted on the ends of the casing 12. One particu-alr design of such an insert is shown as having .a flanged portion 62 which abuts the end of the casing 12 and is secured to the casing 12 by any conventional attaching means such as a plurality of bolts 64. When bolts are employed, a plurality of internally threaded bolt holes 66 is provided through the end of the casing 12 to receive the bolts 64. Use of removably mounted inserts 60 permits reloading of the casing 12 by merely removing the gas generator from the well, disassembling the inserts 60, and reloading the casing with a new propellant grain 14 and then replacing the inserts 60 back on the casing. It should be noted that in such a reloadable gas generator, it is necessary only to have one of the inserts removable, however, for simplicity of manufacture and storage of parts, and for symmetry of design it may be desirable to have the inserts at both ends of the casing 12 removable.

FIGURE 6 illustrates another removable insert 68 which is secured to the casing 12 by means of bolts 70 passing radially through the casing 12. FIGURE 6 additionally illustrates another means for fixedly mounting the diaphragm 20 to the gas generator. The diaphragm mounting is accomplished by welding the diaphragm 20 to the casing 12, as indicated by the weld beads 72. While the welded mounting will not provide pressures within the casing as accurately and reproducibly as will the mounting described above in the discussion of the first embodiment, such a method is suflicient for welltreating apparatus where strict accuracy is not critical.

Another method of removably mounting an insert in the casing 12 is illustrated in FIGURE 7 wherein the insert 74 is held in place by a resilient snap ring 76. The snap ring 76 is received within an annular groove 78 provided in the inner surface of the casing 12 adjacent the end thereof. The snap ring 76 protrudes radially inwardly beyond the inner surface of the casing 12 and abuts the exposed surface 80 of the insert 74. The insert is urged rearwardly against the snap ring 78 by the resilient annular member 28 when such a member is used or by the grain 14 when the annular member is not employed.

Still another method of removably mounting an insert in the casing 12 is illustrated in FIGURE 8 wherein the external surface of the insert 82 is threaded as shown at 84 and is received by the casing 12 having a threaded inner surface 86. It should be clear from the several particular embodiments described above and illustrated in FIGURE 1, and FIGURES 5 through 8, that many con ventional means may be employed to mount the inserts and, therefore, this invention is not limited to those specific means described herein.

It can be seen that the gas generating well-treating apparatus of this invention provides a means which is very inexpensive to manufacture since all parts can be easily mass-produced. Furthermore, use of the gas generator is similarly inexpensive since all that is required in addition to the gas generator itself is a source of electricity such as an electric storage battery. Obviously, such equipment can be easily and safely stored and transferred from location to location. Furthermore, it is well established that solid propellants may be successfully stored over wide ranges of temperatures and pressures without detrimental eifects, thus permitting storage of the gas generators for a long period of time over wide climatic conditions. The gas generator is a rapid-burning nonexplosive device which produces high pressure, high-flowing gas without the detrimental effects of an explosive such as nitroglycerin.

What is claimed as new and intended to be secured by Letters Patent of the United States is:

1. In combination with a well bore, a well-treating apparatus including a neutral-thrust gas generator adapted to be lowered into said bore, said gas generator comprising (a) a tubular cylindrical casing having a combustion section therein,

(b) a solid propellant grain mounted within said combustion section,

(c) ignition means mounted within said combustion section to ignite said grain,

(d) apertured means at each end of said casing to provide flow communication between said combustion section and the external atmosphere contiguous to each end of said casing, and

(e) means to obturate each of said apertured means to effect prevention of moisture from entering said casing and to effect build-up of a predetermined pressure within said combustion section, the obturation means being ejected upon attainment of said predetermined pressure within said combustion section.

2. In combination with a well bore, a well-treating apparatus including a neutral-thrust gas generator adapted to be lowered into said bore, said gas generator comprismg (a) a tubular cylindrical casing having a combustion section therein,

(b) a solid propellant grain mounted within said combustion section,

(c) ignition means mounted within said combustion section to ignite said grain,

(d) an apertured insert removably mounted on each end of said casing to provide flow communication between said combustion section and the external atmosphere contiguous to each end of said casing, and i (e) means to obturate said apertured insert to effect prevention of moisture from entering said casing and to effect build-up of a predetermined pressure within said combustion section, the obturation means being ejected upon attainment of said predetermined pressure within said combustion section.

3. In combination with a well bore, a well-treating apparatus including a neutral-thrust gas generator adapted to be lowered into said bore, said gas genera-tor 'comprising (d) ignition means mounted Within said combustion section to ignite said grain,

(e) an apertured insert removably mounted on each end of casing to provide flow communication between said combustion section and the external atmosphere contiguous to each end of said casing,

(f) attachment means securing said aperture-d insert to said casing, and

(g) a diaphragm fixedly mounted against the outwardly exposed surface of each of said apertured inserts to effect prevention of moisture from entering said casing and to effect build-up of a predetermined pressure within said combustion section, said diaphragm being ejected upon attainment of said predetermined pressure within said combustion section.

4. Well-treating apparatus as defined in claim 3 Wherein said attachment means includes an expandable retention means and an annular groove provided in the inner surface of said casing adjacent said exposed surface of each of said inserts, said retention means residing in said groove and projecting radially inwardly beyond said inner surface of said casing to secure said insert in said casmg.

5. In combination with a Well bore, a Well-treating apparatus including a neutral-thrust gas generator adapted to be lowered into said bore, said gas generator comprising (a) a tubular cylindrical casing having a combustion section therein, said casing having a recess provided in the internal surface adjacent each end thereof,

(b) an internal-burning solid propellant grain mounted Within said combustion section,

(c) ignition means mounted within said combustion section to ignite said grain,

(d) a pair of apertured inserts, one of said inserts being mounted in said casing at each end thereof, each of said inserts having a groove in the outer surface thereof, each of said grooves being radial-1y aligned with one of said recesses,

(e) expandable retentionmeans for retaining each of said inserts Within said casing, one of said retaining means being seated concurrently Within each of said grooves and in the corresponding recess aligned with said each of said grooves, and

(f) means to obturate each of said apertured inserts to effect prevention of moisture from entering said casing and to effect build-up of a predetermined pressure Within said combustion section, said means being ejected upon the attainment of said predetermined pressure within said combustion section.

References Cited by the Examiner UNITED STATES PATENTS 2,613,497 10/1952 MacDonald 6035.6 2,816,418 12/1957 Loedding 60-35.6 2,952,972 9/ 1960 Kimmel et a1 10249 2,958,185 11/1960 Sanders 6035.6 3,001,584 9/1961 Scott 166-63 3,044,255 7/ 1962 Precoul 102-49 3,064,423 11/1962 Frey 10298 X 3,066,734 12/ 1962 Meiklejohn 16642 3,010,117 8/1963 Scott et al 16667 3,171,248 3/1965 Ledwith 60-35.6

OTHER REFERENCES Amer. Rocket Society Journal, vol. 29, No. 7, July 1959, Recent Advances in Solid Propellant Grain Design, pp. 483, 484 required.

BENJAMIN A. BORCHELT, Primary Examiner.

R. F. STAHL, Assistant Examiner.

Claims

1. IN COMBINATION WITH A WELL BORE, A WELL-TREATING APPARATUS INCLUDING A NEUTRAL-THRUST GAS GENERATOR ADAPTED TO BE LOWERED INTO SAID BORE, SAID GAS GENERATOR COMPRISING (A) A TUBULAR CYLINDRICAL CASING HAVING A COMBUSTION SECTION THEREIN, (B) A SOLID PROPELLANT GRAIN MOUNTED WITHIN SAID COMBUSTION SECTION, (C) IGNITION MEANS MOUNTED WITHIN SAID COMBUSTION SECTION TO IGNITE SAID GRAIN, (D) APERTURED MEANS AT EACH END OF SAID CASING TO PROVIDE FLOW COMMUNICATION BETWEEN SAID COMBUSTION SECTION AND THE EXTERNAL ATMOSPHERE CONTIGUOUS TO EACH END OF SAID CASING, AND (E) MEANS TO OBTURATE EACH OF SAID APERTURED MEANS TO EFFECT PREVENTION OF MOISTURE FROM ENTERING SAID CASING AND TO EFFECT BUILD-UP OF A PREDETERMINED PRESSURE WITHIN SAID COMBUSTION SECTION, THE OBTURATION MEANS BEING EJECTED UPON ATTAINMENT OF SAID PREDETERMINED PRESSURE WITHIN SAID COMBUSTION SECTION.