US3773438A - Well stimulation apparatus and method - Google Patents

Abstract

An intensifier unit includes a pair of sequentially operated reciprocating ram assemblies, novel valving systems for controlling the relative movement of the ram assemblies to effect an output of working fluid having a minimum of pressure fluctuations, and a novel pneumatic control system for controlling the valving systems in response to the positions of the ram assemblies. In the preferred embodiment, the unit is mounted on a truck for use in high pressure operations, such as well fracturing, erosion drilling, or the like, and the rams have relatively large diameters and relatively long strokes for providing a minimum of wear and fatigue cycles. In the method, the ram assemblies are returned quicker than they are extended, and are sequentially pressurized prior to initiation of their forward strokes and prior to the decompression of the stroke of the preceding working cylinder to provide an essentially uninterrupted pressure delivery of working fluid to the well.

Description

United StatesPatent 1 Hall et al.

[ 1 Nov. 20, 1973 WELL STIMULATION APPARATUS AND METHOD [75] Inventors: Richard W. Hall, Springfield;

Richard H. Kerr, West Milton; Paul W. Padrutt, Springfield, all of Ohio 1 [73] Assignee: Kelsey-Hayes Company, Springfield,

Ohio

[22] Filed:, Apr. 29, 1971 [21] Appl. No.: 138,568

[52] US. Cl. 417/345, 417/346 [51] Int. Cl. F04b 35/00 [58] Field of Search 417/399, 401, 900, 417/3, 4, 5, 6, 515, 342, 344-347 [56] References Cited UNITED STATES PATENTS 3,280,749 10/1966 Sennet et al. 417/342 3,331,329 7/1967 Bauer 417/342 3,077,838 2/1963 Maglott 417/346 3,234,882 2/1966 Douglas et al. 417/342 2,274,224 2/ 1942 Vickers 417/250 3,205,906 9/1965 Wilkinson et a1. 417/900 X 3,327,641 6/1967 Klosterman 417/900 X 3,477,380 11/1969 Johanson et al.. 417/3 3,507,347 4/ 1970 Bennett 417/900 X Primary Examiner-William L Freeh Assistant Examiner-G. LaPointe Attorney-Marechal, Biebel, French & Bugg [57] ABSTRACT An intensifier unit includes a pair of sequentially operated reciprocating ram assemblies, novel valving systems for controlling the relative movement of the ram assemblies to effect an output of working fluid having a minimum of pressure fluctuations, and a novel pneumatic control system for controlling the valving systems in response to the positions of the ram assemblies. In the preferred embodiment, the unit is mounted on a truck for use in high pressure operations, such as well fracturing, erosion drilling, or the like, and the rams have relatively large diameters and relatively long strokes for providing a minimum of wear and fatigue cycles. In the method, the ram assemblies are returned quicker than they are extended, and are sequentially pressurized prior to initiation of their forward strokes and prior to the decompression of the stroke of the preceding working cylinder to provide an essentially uninterrupted pressure delivery of working fluid to the well.

7 Claims, 5 Drawing Figures Nov. 20, 1973 United StatesPatent 1 Hall et 31.

AVIA

L VI2A l I J mun-10mm 1915 3.7733138mm 1 nr 4 IN VE N TORS HARD W. HALL, HAR KERR 8| PAUL W. DRUTT ATTORNEYS PATEN-IED NEW 20 I973SHEET 3 OF 4 PAlENIEnuuvzo I975 SHEET h []F 4 WELL STIMULATION APPARATUS AND METHOD BACKGROUND OF THE INVENTION Hydraulic well stimulation operations such as those involved in fracturing geological formations adjacent deep well bores, erosion drilling, and the like present difficult problemsdue to the depth of the formation to be fractured, the high pressures required to be generated, the corrosive and abrasive nature of the fluids to be pumped, the long pumping times, and various other factors known to persons skilled to the art.

In conventional practice, these operations are often performed by a series of mechanically geared or revolving crank pumps having relatively short strokes and relatively high cycles per minute, for example 8 inch strokes and 120 cycles per minute. Such pumps tend to fatigue and to break-down rather readily when used for well stimulation, because of the extreme pressures and the high cycles per minute rate of operation, and becausethe working fluid is either abrasive (contains a high solids or sand concentration) or corrosive (contains a highhydrochloric acid concentration) or both, which causes the valves and packings to deteriorate quickly.

Such pumpsalso exhibit pressure pulsations or transient fluctuations which aggravate the adverse effects created by the high rate of fatigue and wear cycles. As a result, effective and profitable well stimulation may not have been realized.

The ideal hydraulic-well stimulating apparatus should have a pumping system with the following features: First, it should have a long stroke in order to reduce the number of fatigue and wear pressure cycles for longer servicelife; Second, it should minimize the pressure fluctuations in the output to minimize the strain on the pumping system; Third, it should be capable of operating at pressures from l20,000psi or more to be able to stimulate deep wells; Fourth, it should be portable, capable of being easily transported from site to site; Fifth, it should be capable of operating for long periods of time to stimulate hitherto unstimulatable wells; and

Sixth, it should be inexpensive to operate and maintain.

SUMMARY OF THE INVENTION The present invention is directed to a new apparatus and method for pumping high pressure contaminated and corrosive fluids at relatively high horsepower for "wen stimulation purposes and the like. In general, the invention provides a two-cylinder intensifier which -maximizes volume per stroke and reduces the rate of operation using large diameter pumping rams having relatively long strokes. 'The system circuit includes novel valve systems for controlling the supply of high pressure driving fluid to the rams and a novel control circuit for controlling the valve systems to effect movement of the rams for converting high horsepower to a smooth, high pressure fluid flow with a minimum of fatigue cycles.

A high horsepower source, such as 1,100 horsepower turbine engine, drives a series of pumps, preferably of variable output, and these pumps deliver driving fluid at a high pressure to the power rams. The pressure of the driving fluid is in turn multiplied by the ram assemblies, wherein the diameters of the power rams are greater than the diameters of the pumping rams, and the working fluid is delivered to a well or the like at an increased or multiplied pressure, for example l020,000 psi or more, by alternating forward strokes of the ram assemblies. The strokes of the pumping rams are relatively long, for example inches, to minimize the frequency of operation, and the consequent number of fatigue cycles and total wear.

The ram assemblies are driven on their return strokes by a precharged accumulator which is adapted to return the ram assemblies quicker than they are extended in order that the returning ram may be pressurized while the extending rarn decelerates. The ram assemblies, as controlled by the novel valve systems and the novel pneumatic control circuit, cooperate to produce a smooth, relatively pulseless output having a relatively constant pressure.

Each valve system comprises a control valve for admitting driving fluid to the ram to effect the forward stroke of the power ram, a pressure relief valve for decompressing the power ram, at the completion of its forward stroke, and an exhaust valve for exhausting the power ram after its decompression to enable the return rams to effect the return stroke. Each system also includes a differential check valve for pressurizing the power ram, prior to the admittance of driving fluid to the ram, to a pressure less than the driving pressure to achieve a smooth transition of output pressure as the rams reciprocate back and forth. In addition, each valve system includes a directional control valve for admitting driving fluid to the differential check control valve before the ram starts to extend and for admitting driving fluid to the exhaust valve to keep this valve open while the ram returns.

The pneumatic control circuit, on the other hand, includes a relay control valve and a holding valve for responding to the movement of each ram assembly, and a reversing valve actuated by the movement of both ram assemblies. The circuit is operatively connected to two pairs of tappet valves, one for each ram assembly, which signal the completion of the forward and return strokes of the ram assemblies. The circuit responds to actuation of the tappet valves and alternately pressurizes and actuates one ram while the other ram decelerates to reverse, by sequentially operating the valve systems, and provides a reliable means of controlling the intensifier output and of achieving the objects of the invention.

One object of the present invention is to provide a reliable, efficient and dependable pressure multiplier with an optimized service life, and an improved method of fracturing wells and the like.

Another object is to provide a pressure multiplier with reduced frequency of operation and with an increased stroke length and pumping ram diameter, so as to minimize wear and optimize valve life.

An important object isto provide a means for returning the rams faster than they are extended to provide a time interval, and to pressurize the return ram in that time interval to provide a smooth, relatively pulseless high pressure output.

These and other objects will become apparent from the drawings, the following description and the appended claims.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the two-cylinder fluid pressure intensifier of the present invention mounted on the bed of a truck;

,, FIG. 2 is an arrangement drawing of the partial system drawings shown in FIGS. 3A-C;

FIGS. 3A is a diagrammatic system drawing showing the intensifier ram assemblies, the air supply unit, the accumulator, the supply tank, and the main valve station of the present invention;

FIG. 3B is a diagrammatic system drawing showing the pneumatic control panel of the present invention;

FIG. 3C is a diagrammatic system drawing showing a main pumping unit for use in the practice of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment consists of a two-cylinder fluid pressure multiplier or intensifier which converts high pressure driving fluid flow into a smooth multiplied high pressure working fluid output especially adapted for fracturing geological formations adjacent well bores or the like. The apparatus accomplishes this result with a pair of intensifying ram assemblies having relatively long forward and return strokes and large diameters for reducing the frequency of operation, and includes means for effecting relative movement of the ram assemblies in a manner which minimizes pressure fluctuations in the working fluid output to provide for improved efficiency and service life.

Referring generally to FIG. 1, the intensifier of the present invention may be conveniently mounted on the bed of a truck, and includes a pair of ram assemblies comprising pumping rams PA and PB which receive working fluid throughinlets 20 and discharge working fluid throughoutlets 21 at the end of the truck, and power rams RA and RB connected to the pumping rams PA and PB respectively. The truck carries a driving fluid (preferably hydraulic oil) supply tank T1, and a high horsepower source such as a turbine engine TMl drives a pair of main pumps P1 and P2 which deliver driving fluid from tank T1 to a valve station M1 which sequentially admits fluid to the power rams RA and RB to effect the forward pumping strokes of the ram assemblies.

The intensifier also includes a precharged accumulator AC1 for driving a pair of twin return rams QA and QB (rams QB are not shown in FIG. 1) to effect the return strokes of the ram assemblies. A diesel engine D1 drives a pair of small pumps (not shown) which supply the accumulator AC1 and main pumps P1 and P2 respectively, and also a compressor (not shown) and the compressor supplies air to a pneumatic control panel APl mounted on one side of the truck and adapted to control the valve station M1 in response to movement of the ram assemblies.

The intensifying Ram Assemblies Referring more specifically to FIG. 3A, a preferred embodiment of the invention is shown wherein the power rams RA and RB have 9 inch diameters and are adapted to reciprocate on 70 inch strokes within hyare connected at the opposite ends of each bridge, and

preferably on opposite sides of each pumping ram to move the ram assemblies on their return strokes.

Accumulator The accumulator ACI is pre-charged with driving fluid to about 1,000 psi and has a pair ofbranch lines 35 and 36 including check valves V12A and V128 connected to thereturn ram cylinders 34. A small auxiliary pump P3 (approximately 6 GPM) driven by the diesel engine D1 is adapted to charge the accumulator by delivering fluid from the supply tank T1 through filter F2 to anintersection 38 to theaccumulator charge line 40 connected to the accumulator AC1 and tolines 35 and 36. This branch circuit includes a pressure relief valve V6 adapted to spill fluid over to tank T1 when the pressure inlines 35 and 36 exceeds 1,000 psi. The accumulator AC1 supplies 1,000 psi fluid to the return rams QA and QB to effect the return strokes of the intensifying ram assemblies, and receives fluid from thereturn cylinders 34 on the forward strokes of the pumping rams PA and PB. Pump P3 discharges at 1,000 psi and its discharge pressure is controlled by relief valve V13.

Main Hydraulic Pump Unit BPl Referring to FIGS. 3A and 3C, the main hydraulic pump unit BPl may include any of a number of pumping means, preferably of variable output, for supplying fluid to the intensifier ram assemblies. For purposes of the present disclosure, the unit BPl is shown as including a pair of Kelsey-Hayes 500600 HP hydraulic fluid pumps P1 and P2 driven in tandem by a variable speed 1800 rpm Solar turbine engine TMl and having a 1,100 hp or more output. The pumps P1 and P2 are charged through aline 42 and filters FlA and FIB by a supercharging pump P4 (approximately 600 GPM) which is driven by the diesel engine D1 and whose output is controlled at psi by the pressure relief valve V9.

Each pump P1 and P2 includes three six-piston sections which discharge through corresponding outlets 43-45 and 46-48, andoutlets 44 and 47 are preferably connected tooutlets 45 and 48, respectively, so that one section discharges throughline 50 and S1 and two sections discharge throughlines 52 and 53. The outputs of the pump P1 and P2 may be varied by control units PMl and PM2, respectively, each of which includes an unloadingvalve 54 consisting of a main by-pass andpressure relief valve 55 and a normally openpilot control valve 56.

Under normal operation, the pumps P1 and P2 deliver fluid through lines 50-53 to a mainfluid output line 60 connected to the main hydraulic valve station M1. The pump unit BPl is preferably provided with means for changing the outlet pressure when the turbine speed is changed, for example by a change in altitude, and includes a remote selector (not shown) adapted to selectively energize solenoid valves AV 1- 8A-D, to load selected pump sections according to the power available at the turbine. The selector is also used to protect the pumps P1 and P2 from being overloaded. A pressure sensing valve PV9 senses the pressure inline 50, and when the'pressure reaches 5,100 psi, actuates valves AV18A and AV18C which in turn cause theircorresponding control valves 54 to unload one section of each pump to tank T1, causingvalve 55 to act as a relief valve, and the pumps run at two thirds ca- ..pacity. In the present illustration, a maximum load condition with only two sections of each pump operating is set at 6,500 psi at the pump outlet, and is selected by actuating solenoid valve AV18E, so that fluid is returned through relief valve PVS to tank T1. Normally, however, the maximum load condition is 5,200 psi, and this pressure level ismaintained by relief valve PV6 also connected to returnline 62.

The flow through lines 50-53 is controlled by the air actuated check valve PV8 which receives hydraulic fluid throughline 65 from the auxiliary pump P3 (FIG. 3A). When valve PV8 is open, fluid is delivered through check valve PV7 and thence throughlines 50 and 52 to closecheck valves 66 and 67, and through line:.60 tolines 51 and 53 to closecheck valves 68 and 69. In this blocking mode, the fluid delivered by pumps P1 and P2 is diverted through the control units PMl and PM2 to the supply tank T1 via check valves 71-74 and returnline 62, or throughpressure relief valves 55 and returnline 75.

Main Hydraulic Valve Station M1 The main valve station Ml (FIG. 3A) includes two identical valve systems VA and VB for controlling the fluid supply fromline 60 to the power rams RA and RB respectively. The valve systems include pneumatically actuated shut-off valves VIA and V1B having ports 1-3. 'When valves VIA and VlB are open (connecting ports 1-2), they admit fluid fromline 60 to theinlet ports 24 of thepower ram cylinders 22 and 23 and effect the forward strokes of rams RA and RB.

The station M1 also includes pneumatically actuated directional control valves V2A and V2B having ports I-7 and loops LA and LB between control valves V2A and V2B and theinlets 24 ofcylinders 22 and 23. The loops LA and LB include decompression check valves V3A and V3B connected in parallel with differential check valves V4A and V4B, respectively, the latter valves V4A and V4B being set at 150 psi less than the driving pressure in line60.

The directional control valves V2A and V2B are movable between pressurizing and exhausting positions and are biased normally to the pressurizing position (connecting ports 2-5), so that fluid fromline 60 is normally delivered to the loops LA and LB enabling power rams RA and RB to be pressurized to 150 psi less than the working pressure ofline 60. When in their exhaust position (connecting ports 2-4), fluid fromline 60 flows into and opens exhaust valves VSA or VSB connected to theoutlets 25 ofcylinders 22 and 23, and

permits the rams RA and RB to be exhausted.

The valve systems VA and VB are adapted to effect the forward stroke of one ram while, at the same time, effecting the return stroke of the other ram at a faster rate, in order that the returning ram may be pressurized prior to its forward stroke. This feature enables the returning rarn to reverse and precharge to 5,050 psi (150 psi less than the working pressure 5,200 psi) as the first ,extending ram decelerates to reverse. This keeps high pressure fluctuations in the output to a minimum and insures that the intensifiers will deliver stable pressure output.

Pneumatic Control Panel Referring to FIGS. 3A-3B, the pneumatic control panel API is supplied with pressurized air from the air supply unit ASl, which includes an air tank supplied with air by acompressor 81 driven by the diesel engine D1. The panel APll receives air from thetank 80 throughline 82 and includes a solenoid operated remote start/stop switch AV16 and a manually operated start/stop switch AV12.

A directional control switch AVM having ports 14 is spring biased to the normal operating position (connecting ports 1-2) and has a reset position (connecting port 1-3). A reset circuit for returning the power rams RA and RB to their starting positions is connected toport 3 of switch AV14, and a manual directional control valve AVll is connected toport 2 of switch AV 14. The valve AVll has two positions,position 1 for automatic movement of the rams, andposition 2 for inching movement of the rams.

When pulled out toposition 1, valve AVll delivers air tointersection 85 and through shuttle-valve AV9 tointersection 86 where the air is diverted in three directions.Line 87 diverts air to the main pump unit BPI,line 88 diverts air to a reversing control valve AV7 having ports 1-6 and thence to shut off valve VlA or VlB in the main valve station M1, andline 89 diverts air to the relay valve AV3A.Branch line 90 diverts air fromline 87 to the relay valve AV3B. Air is also delivered viaintersection 85 andline 91 to tappet valves AVIA- B and AV2A-B (FIG. 3A) positioned for actuation by thecams 31 at the forward and return extensions of the ram assemblies. Abranch line 92 connects this air to ports 6 of directional control valves V2A and V2B, biasing them in their pressurizing position.

It will be noted that the reversing control valve AV7 has two positions: position 1 (opening ports I-2) for admitting air to valve VlA through check valve AV8A andline 94, and position 2 (opening ports 1-3) for admitting air to valve VlB through check valve AV8B andline 95. Panel API also includes holding valves AV4A and AV4B having ports 1-4 and movable between normally open positions (connecting ports l-2), and blocking positions (connecting ports 2-3). These valves are moved to their blocking positions when air passes through valve AV7, to valve AV4A by air inline 97, and to valve AV4B by air inline 98.

When pushed in toposition 2, valve AVlI delivers air to a crank-operated three-position inch controlvalve AVlt) spring biased toposition 3 which completely stops the flow of air and movement of the rams.

In position I, valve AVlll) connects with valve station Sequence of Operations Reset Before the operating cycle is commenced, the system is reset. To do this the diesel engine D1 is started and auxiliary pump P3 fully charges the accumulator AC1 to 1,000 psi. Engine D1 also starts thecompressor 81 so that air passes throughline 82 to the control panel API. The solenoid start/ stop valve AV16 is then energized, and the manual start/stop valve AV12 is placed in the stop position. The system reset valve AV14 is then depressed, held, and valve AV12 is pulled to the start position to connect air fromline 82 tointersection 100. The air branches vialine 101 to hydraulic valve PV8, opening this valve and admitting fluid into the pump unit BPl, where it is blocked by check valves 66-69 and flows throughline 60 to valve unit M1 at the accumulator pressure 1,000 psi.

Air also branches fromintersection 100 throughline 102 tointersection 103 and through shuttle valves AV17A and B andlines 104 and 105 toports 7 of directional control valves V2A and V2B, causing these valves to counteract the pressure on ports 6 thereof and to connectports 2 to ports 4 andports 3 toports 5. Air also passes fromline 102 viabranch lines 107 and 108 through shuttle valves AV13A and AV13B to ports 4 of air valves AV3A and AV3B, setting them inposition 1.

The opening of valve PV8 feeds fluid from auxiliary pump P3 throughsupply line 60 and through ports 2-4 of valves V2A and V2B to open exhaust valves V5A and VSB and connect the main intensifier rams RA and RB to exhaust. With these main rams to exhaust, the accumulator AC1 supplies oil to the small return rams QA and QB effecting the return strokes of both intensifier units. On completion of the return strokes, tappet valves AV2A and AV2B are depressed, completing the system reset cycle. The system reset valve AV14 is then released.

Neutral The system is then placed in the neutral or stop position. With the system in the cycle reset position, as de- Ram RA Forward Ram RB Prepressurized With the pumps recycling to tank, the system is ready to start an automatic cycle. With both main power rams RA and RB fully returned and resting on tappet valves AV2A and AV2B, with all pumps running, and with air valve AV7 inposition 1, shown, the inch/auto valve AVll is pulled to position 1 to connect air tointersection 85 from which it is diverted to the tappet valves AVlA-B and AVZA-B vialine 91 and tointersection 86 via shuttle valve AV9.

Since the tappet valves AV2A-B are initially engaged, air passes through these valves and throughlines 110 and 111 via shuttle valves AVSA and AVSB and shuttle valves AV13A and AV13B to port 4 of relay valves AV3A and AVSB, moving these valves to posi-Via line 88 through reversing valve AV7 toport 3 of I control valve VIA, opening this valve and commencing the forward stroke of ram RA, and throughbranch 97 to port 4 of ram RA, and throughbranch 97 to port 4 of valve AV4A to hold this valve in blocking position. 3. Vialine 89 toport 1 of relay valve AV3A where it is blocked.

The main pumps P1 and P2, when loaded, deliver fluid thru valve VlA into themain intensifier cylinder 22, starting the forward stroke of power ram RA and displacing oil from the small return rams QA into the accumulator AC1, or, the accumulator is fully charged, displacing fluid through relief valve V6 to tank T1. At the same time, driving fluid passes through ports 2-5 of valve V2B to valve V4B in loop LB. Valve V4B closes when the pressure on the outlet port, which is connected to intensifier ram RB, reaches 150 psi less than the pressure inline 60, causing the intensifier ram RB to be pressurized to within 150 psi of the moving intensifier ram RA.

Ram RB Forward Ram RA Stops On the completion of the forward stroke of intensifier ram RA, the tappet valve AVlA is depressed, causing air to be admitted vialine 115 and shuttle valve AV6A toport 1 of holding valve AV4A. However, since valve AV4A is still being held in a blocking position by air on port 4 thereof, it remains blocked. Air is also admitted viabranch line 116 toport 5 of reversing valve AV7, operating this valve (connecting ports l-3 and ports 2-4) and effecting a transfer of the air being delivered throughline 88 fromline 94 toline 95. Accordingly, air passes through check valve AV8B and is admitted vialine 95 toport 3 of valve VlB, opening this valve and permitting driving fluid to be admitted to ram RB to commence the start of its forward stroke. Air is also admitted vialine 98 to port 4 of holding valve AV4B, moving this valve to its blocking position.

At the same time, but at a slower rate set by valve AV8A,port 3 of valve VlA exhausts vialine 94 through valves AV8A and AV7, resetting valve VIA to the closed position. This stops the forward movement of intensifier ram RA. In this condition, ram RB is receiving the full main pump output through valve VlB.

Reversal-Ram RA Returns and Pressurizes Ram RB Stops As the pressure exhausts fromport 3 of VIA, port 4 of valve AV4A also exhausts, at the same rate and at the same time, resetting valve AV4A and openingport 1 toport 2. This allows air from the tappet valve AVlA to be admitted through valve AV4A toport 5 of relay valve AV3A, shifting this valve toposition 2 and connectingport 1 toport 2. The air inline 89 is therefore directed through this valve and through shuttle valve AV 17A toport 7 of the directional control valve V2A vialine 104, counteracting the air pressure against port 6 fromline 92 and opening ports 2-4 and ports 3-5. This action admits driving fluid to exhaust valve VSA.

Cylinder 22 decompresses at a rate set by valve V3A, and on completion of decompression, exhaust valve VSA opens and exhausts ram RA through valve VA. With intensifier ram RA fully opened to exhaust, the charged accumulator AC1 actuates the small return rams QA and ram RA starts its return stroke, first releasing tappet valve AVlA and, on completion of the return stroke, operating tappet valve AV2A. The releasing of tappet valve AVlA exhaustsport 5 of relay valve AVSA, and the operating of tappet AV2A admits air to port 4 of AVSA, causing this valve to move toposition 1 and block the air flow throughline 89. The releasing of tappet valve AVlA also exhaustsport 5 of reversing valve AV7 throughline 116. However, since this valve is not spring biased, it momentarily remains in the reversed position until actuated again.

Meanwhile, the intensifier ram RB is still making its forward stroke, displacing fluid from the return rams QB into the accumulator AC1. The intensifier ram RA is pressurized through valve V2A and sits at the start of its forward stroke. On completion of the forward stroke of ram RB, the tappet valve AVlB is actuated and air is admitted vialine 118, shuttle valve AV6B, andline 120 to port 6 of reversing valve AV7, moving this valve toposition 1 and connectingport 1 toport 2. Air is also admitted toport 1 of the blocked valve AV4B.

Rarn RA Forward Ram RB Prepressurized Again As it reverses, valve AV7 supplies air throughline 94 to open valve VIA, and this admits fluid from the main pump supply tocylinder 22, thereby starting ram RA on its forward stroke again. Simultaneously, valve AV7 cuts ofi air pressure tolines 95 and 98, and consequently these lines exhaust through valve AV8B and valve AV7. The exhausting ofline 95, as was the case for the exhausting ofline 94, described previously, causes valve VlB to close and cut off the supply of driving fluid to ram RB. As a result ram RB stops. The exhausting ofline 98 releases valve AV4B, openingport 1 toport 2 thereof and enabling air inline 118 to actuate relay valve AV3B toposition 2, connectingport 1 toport 2.

This action enables air frombranch line 90 to be admitted through relay valve AV3B and shuttle valve AVl7B toport 7 of directional control valve V2B, opening ports 2-4 and'enabling driving fluid to be admitted to exhaust valve VSB.Cylinder 23 is accordingly decompressed at a rate set by valve V3B in loop LB, and on completion of a decompression, exhaust valve V5A opens and, under the pressure exerted by the accumulator AC1 on return rams QB, and ram RB exhausts through valve V2B and starts its return stroke.

The system thus starts another cycle. The forward stroke takes a longer period of time to complete than the return stroke, in order that the returning ram may be pressurized while awaiting its next forward stroke. in addition, the system, by pressurizing the returned ram to within 150 psi of the forward moving ram, provides a smooth, relatively pulseless output flow which minimizes the mechanical wear on the valving and extends the service life of the system.

Adjustment of Ram RA or Ram RB A manual system is provided to set the tappet valves, check clearances, etc. Ram RA is adjusted by moving the air valve AVll to the inch position,position 2, thereby connecting the air supply to valve AV 10, and

to port 6 of reversing valve AV7, setting this valve inposition 1.

Fromintersection 125, air passes through shuttle valves AVIS and AV9 tointersection 86 where it is diverted in three directions.Line 87 supplies air to the solenoid valves AV 18A-E which control the supply pumps P1 and P2.Line 89 connects air toport 1 of relay valve AVSA, where it is blocked, andline 88 connects air through valves AV7 and AV8A toport 3 of VIA, thereby opening this valve and admitting driving fluid fromline 60 to ram RA, starting its forward stroke.

At the same time, branch.line 90 delivers air through relay valve AV3B and shuttle valve AV17B toport 5 of the directional control valve V2B, causing driving fluid to be admitted to valve VSB and effecting ram RBs return stroke.

Since all motion stops when valve AV10 is moved toposition 3, ram RA'may be adjusted forwardly by intermittently moving valve AV10 intoposition 1 and intoposition 3 to effect inching movement.

Ram RE is similarly adjusted by pushing air valve AV10 toposition 2. This connects air to intersections and 131. Fromintersection 131, air passes through shuttle valve AV6A and holding valve'AV4A toport 5 of relay AV3A, actuating this valve toposition 2, and also throughline 116 toport 5 of reversing valve AV7, also actuating this valve toposition 2. Air is also connected throughline 132 and via shuttle valves AVSB and AV13B to port 4 of relay valve AV3B, actuating this valve toposition 1.

Fromintersection 130 air is diverted through shuttle valves AVl5 and AV9 tointersection 86, where it is again diverted in three directions. Air inline 87 is again supplied to solenoid valves AV18A-E. This time, however, air inbranch line 90 is blocked atport 1 of relay AV3B; valve AV7 connects air inline 88 toport 3 of valve VlB, actuating this valve and admitting driving fluid to ram RB; to start its forward stroke; and air inline 89 passes through relay valve AVSA and shuttle valve AV17A toport 7 of directional control valve V2A, actuating this valve and admitting driving fluid to exhaust valve V5A effecting the return of ram RA.

Thus, by a similar pneumatic network, ram RB may be adjusted by intermittently moving valve AV10 intoposition 2 and into position No. 3 (stop position). Only when this valve is moved toposition 1 or 2 are the main pumps loaded. During inch conditions, the tappet valves AV lA-B and AV2A-B are inoperative.

Emergency Stops During movement of either intensifier unit, an emergency stop can be efiected by depressing valve AVl2 or de-energizing valve AV16. These valves interrupt the air supply and exhaust the system. This action immediately unloads the main pumps and stops any movement of the intersifier rams RA and RB.

It is therefore apparent that a pressure intensifier constructed in accordance with the present invention provides certain desirable features and advantages. For example, an intensifier using the turbine and main pumps described above has the following theoretical outputs:

-- 16,800psi X 108 gpm 1,060 hp 1,500 rpm at 5,200

2/3 Pumps 21,000psi X 72 gpm 980 hp 1,500 rpm at 6,500 psi The intensifier is thus capable of driving high pressure output which is useful for well fracturing purposes and the like.

Moreover, the intensifier is able to deliver high pressure output with a minimum of pressure fluctuation and at a variety of pressures so that the output consists of a smooth, relatively pulseless flow which minimizes the power shocks on the intensifier. The intensifier is well suited to a long stroke, large diameter intensifier ram assembly, which reduces the frequency of operation so that there are fewer fatigue and wear cycles on the valves producing improved service life and reducing the overall maintenance expense.

In addition, the valve systems together with the pneumatic control circuit of the present invention operate to return the rams faster than they. are extended to provide a time interval in which the return ram is pressurized while the extending ram is decelerating to reverse. As soon as the extending ram reverses, the valve system and pneumatic control circuit operate the pressurized ram to provide the relatively pulseless output flow described above. The valve systems and pneumatic control circuit are unique and enable the intensifier to operate nearly continuously and relatively free of maintenance expense.

The foregoing features enable hitherto low yielding wells to be fractured more economically than in the past, and also enable wells which have come untapped to be stimulated. The apparatus of the present invention, therefore, from the practical standpoint, provides a significant advance in the art.

While the methods and forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus,

.and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

l. Hydraulic well fracturing equipment including a first intensifier having a hydraulic ram and a second intensifier having a hydraulic ram, each said intensifier having a common outlet for delivering fracturing fluid at high pressure to a well or the like, a source of hydraulic operating fluid under high pressure for operating said rams, main control valves operable to apply fluid from said source to each of said rams, adjustable decompression valves operable to bleed off the hydraulic pressure from each of said rams, relatively larger valves for each of said rams providing for rapid exhaust of the hydraulic fluid therefrom, and pneumatic control means responsive to the approach of one of said intensifier rams toward the end of its stroke for performing the following steps insequence 1. open the main control valve to the other of said intensifiers to start its ram on a working stroke,

2. close the main control valve to said one intensifier ram,

3. operate the decompression valve of said one ram to bleed off hydraulic pressure therefrom, and

4. operate said larger exhaust valve of said one ram to provide for the rapid exhaust of the fluid therefrom.

2. The fracturing equipment ofclaim 1 further comprising means for returning said one intensifier to its starting position at a rate which substantially exceeds the movement of said other intensifier under the influence of said hydraulic pressure, and valve means for prepressurizing said one intensifier to a pressure somewhat less than the working pressure of said other intensifier.

3. The system ofclaim 2 in which said prepressurizing means includes a differential check valve.

4. In an intensifier having first and second reciprocating ram cylinders, a source of driving fluid at a driving pressure, means for effecting the return strokes of said ram cylinders, pneumatic control indicators positioned for actuation by said ram cylinders on their forward and return strokes, a pair of identical first and second valve systems for controlling the forward and return strokes of said ram cylinders, said first valve system comprising:

a directional control valve connected to said driving fluid source and movable to a prepressurizing position in response to actuation of the indicator on the return stroke of a first ram cylinder and to an exhausting position in response to actuation of the indicator on the forward stroke of said first ram cylinder, differential check valve connected between said first ram cylinder and said directional control valve for prepressurizing said first ram cylinder in response to movement of said directional control valve to its prepressurizing position, pressure release valve operatively connected between said first ram cylinder and said directional control valve for decompressing said first ram cylinder in response to actuation of the indicator on the forward stroke of said first ram cylinder,

an exhaust valve operatively connected between said first ram cylinder and said directional control valve for exhausting said first ram cylinder in response to movement of said directional control valve to its exhausting position, and

a control valve connected to the driving fluid source and responsive to actuation of the indicator on the forward stroke of a second ram cylinder to admit driving fluid to said first ram cylinder to effect its forward stroke.

5. In well fracturing equipment, the improvement comprising:

at least two sequentially operating reciprocating working cylinders for supplying a working fluid under high pressure to the well,

a separate ram cylinder connected for operating each of said working cylinders,

a source of driving fluid under pressure,

means for delivering the driving fluid to said ram cylinders at a driving pressure,

a separate valve system for each ram cylinder, including means for prepressurizing each ram cylinder to 13 14 a pressure less than said driving pressure, means for under high pressure to the well, admitting driving fluid to each ram cylinder at said a separate ram cylinder connected for operating each driving pressure to effect its forward stroke, and of said working cylinders, means for decompressing and exhausting eachram 3 Source of i i fl id under pressure, y at the completlon of its forward Stroke, 5 means for delivering the driving fluid to said ram cyla bridge member operatively connected between inders at a driving pressure 621?}! ram y f and each f Cylmder a aseparate valve system for each ram cylinder, includof F cylmders operatlveiy connected ing means for prepressurizing each ram cylinder to Gael; g g effechtmg F a pressure less than said driving pressure, means for es 0 Sal ram Cy m ers at t 6 Comp anon o 10 admitting driving fluid to each ram cylinder at said their forward strokes, d

rlvmg pressure to effect its forward stroke, and and control means for controlling said valve systems means for decompressmg and exhausting each ram and said return cylinders to effect return strokes of said ram cylinders at a rate substantially faster than said forward strokes thereof to provide time for prepressurization of said ram cylinders for enabling said ram cylinders to produce a smooth, relatively continuous and pulseless output flow of said working fluid to said well. 6. The equipment ofclaim 5 wherein said actuating means comprises a pre-charged accumulator connected to said return cylinders.

cylinder at the completion of its forward stroke, return cylinders operatively connected to effect the return strokes of said ram cylinders at the comple tion of their forward strokes, and control means for controlling said valve systems and said return cylinders to effect return strokes of said ram cylinders at a rate substantially faster than prepressurization of said ram cylinders for enabling 7. In Well fracturing equipment, the improvement said ram cylinders to produce a smooth, relatively comprising: continuous and pulseless output flow of said workat least two sequentially operating reciprocating ing fluid to said well.

working cylinders for supplying a working fluid said forward strokes thereof to provide time for

Claims (10)

1. Hydraulic well fracturing equipment including a first intensifier having a hydraulic ram and a second intensifier having a hydraulic ram, each said intensifier having a common outlet for delivering fracturing fluid at high pressure to a well or the like, a source of hydraulic operating fluid under high pressure for operating said rams, main control valves operable to apply fluid from said source to each of said rams, adjustable decompression valves operable to bleed off the hydraulic pressure from each of said rams, relatively larger valves for each of said rams providing for rapid exhaust of the hydraulic fluid therefrom, and pneumatic control means responsive to the approach of one of said intensifier rams toward the end of its stroke for performing the following steps in sequence 1. open the main control valve to the other of said intensifiers to start its ram on a working stroke, 2. close the main control valve to said one intensifier ram, 3. operate the decompression valve of said one ram to bleed off hydraulic pressure therefrom, and 4. operate said larger exhaust valve of said one ram to provide for the rapid exhaust of the fluid therefrom.

2. close the main control valve to said one intensifier ram,

2. The fracturing equipment of claim 1 further comprising means for returning said one intensifier to its starting position at a rate which substantially exceeds the movement of said other intensifier under the influence of said hydraulic pressure, and valve means for prepressurizing said one intensifier to a pressure somewhat less than the working pressure of said other intensifier.

3. The system of claim 2 in which said prepressurizing means includes a differential check valvE.

3. operate the decompression valve of said one ram to bleed off hydraulic pressure therefrom, and

4. operate said larger exhaust valve of said one ram to provide for the rapid exhaust of the fluid therefrom.

4. In an intensifier having first and second reciprocating ram cylinders, a source of driving fluid at a driving pressure, means for effecting the return strokes of said ram cylinders, pneumatic control indicators positioned for actuation by said ram cylinders on their forward and return strokes, a pair of identical first and second valve systems for controlling the forward and return strokes of said ram cylinders, said first valve system comprising: a directional control valve connected to said driving fluid source and movable to a prepressurizing position in response to actuation of the indicator on the return stroke of a first ram cylinder and to an exhausting position in response to actuation of the indicator on the forward stroke of said first ram cylinder, a differential check valve connected between said first ram cylinder and said directional control valve for prepressurizing said first ram cylinder in response to movement of said directional control valve to its prepressurizing position, a pressure release valve operatively connected between said first ram cylinder and said directional control valve for decompressing said first ram cylinder in response to actuation of the indicator on the forward stroke of said first ram cylinder, an exhaust valve operatively connected between said first ram cylinder and said directional control valve for exhausting said first ram cylinder in response to movement of said directional control valve to its exhausting position, and a control valve connected to the driving fluid source and responsive to actuation of the indicator on the forward stroke of a second ram cylinder to admit driving fluid to said first ram cylinder to effect its forward stroke.

5. In well fracturing equipment, the improvement comprising: at least two sequentially operating reciprocating working cylinders for supplying a working fluid under high pressure to the well, a separate ram cylinder connected for operating each of said working cylinders, a source of driving fluid under pressure, means for delivering the driving fluid to said ram cylinders at a driving pressure, a separate valve system for each ram cylinder, including means for prepressurizing each ram cylinder to a pressure less than said driving pressure, means for admitting driving fluid to each ram cylinder at said driving pressure to effect its forward stroke, and means for decompressing and exhausting each ram cylinder at the completion of its forward stroke, a bridge member operatively connected between each ram cylinder and each working cylinder, a pair of return cylinders operatively connected to each bridge member for effecting the return strokes of said ram cylinders at the completion of their forward strokes, and control means for controlling said valve systems and said return cylinders to effect return strokes of said ram cylinders at a rate substantially faster than said forward strokes thereof to provide time for prepressurization of said ram cylinders for enabling said ram cylinders to produce a smooth, relatively continuous and pulseless output flow of said working fluid to said well.

6. The equipment of claim 5 wherein said actuating means comprises a pre-charged accumulator connected to said return cylinders.

7. In well fracturing equipment, the improvement comprising: at least two sequentially operating reciprocating working cylinders for supplying a working fluid under high pressure to the well, a separate ram cylinder connected for operating each of said working cylinders, a source of driving fluid under pressure, means for delivering the driving fluid to said ram cylinders at a driving pressure, a separate valve system for each ram cylinder, including means for prepressurizing each ram cylinder to a pressure less than said driving pressure, means for admitting driving fluid to each ram cylinder at said driving pressure to effect its forward stroke, and means for decompressing and exhaUsting each ram cylinder at the completion of its forward stroke, return cylinders operatively connected to effect the return strokes of said ram cylinders at the completion of their forward strokes, and control means for controlling said valve systems and said return cylinders to effect return strokes of said ram cylinders at a rate substantially faster than said forward strokes thereof to provide time for prepressurization of said ram cylinders for enabling said ram cylinders to produce a smooth, relatively continuous and pulseless output flow of said working fluid to said well.

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