US2670801A - Recovery of hydrocarbons - Google Patents

Description

March 2, 1954 Y J. E. sHERBoRNE l RECOVERY OF' HYDROCARBONS 4 Shee'cs--Sheerl l Filed Aug. 13, 1948 March 2, 1954 f J. SHERBQRNE 2,670,801

RECOVERY OF HYDROCARBONS Filed Aug. 1s, 1948 4 sheets-sheet 2 March 2, 1954 J. E. SHERBORNE.

RECOVERY oF HYDRocARBoNs Filed Aug. 13, 1948 4 Sheets-Sheet 3 Fre. 3.

March 2, 1954 J. E. sHERBoRNE 2,670,801

RECOVERY oF HYDRocARBoNs Filled Aug. 13, 1948 4 Sheets-Shee1-I 4 y @www AWM/Vix Patented Mar. 2,A 1954 RECOVERY OF HYDROCARBONS John E. Sherborne, Whittier, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application August 13, 1948, Serial No. 44,073

(Cl. 16B-21) 8 Claims.

This invention relates to the use of sonic or supersonic waves'for increasing the recovery and production of crude petroleum from oil-bearing formations. More particularly, this invention relates to use of sonic and ultrasonic or supersonic vibrations in conjunction with secondary recovery processes employing fluid drive, such as Water flooding, gas drive and the like, whereby the efficiency of the driving liquid or gas for stripping oil from the oil-bearing formation is markedly improved by the employment of such vibrations.

As the age of an oil field increases the formation pressure nally decreases to a point where there is insufficient potential energy in the formation to cause the oil to flow to production wells at commercially significant rates. As producing wells approach this state, it has been the practice to force a driving agent or driving fluid such as water, oil field brine, natural gas, flue gas, air or the like into the oil-bearing formation from an input well centrally located with respect to several producing wells for the purpose of driving oil into the latter. The use of .driving agents has not been confined solely to widely varying textures and degrees of permeability. During flooding or driving operations water, gas or the like is forced into the oil-bearing formation under sufficient pressure to wash or push a part of the oil remaining in the formation toward and ultimately into the producing well or wells.

' The flooding or driving operation is of limited value for effecting secondary recovery and increasing the net yield of oil from a formation because of the fact that the Water or gas preferentially strips the oil from the most permeable channels initially and then continues to flow at steadily increasing rates through the partially oil-free channels of high permeability. This condition is further accentuated by the lower viscosity of water or gas as compared to that of most oils. The channeled flow of ooding liquid or driving gas progressively increases the water to oil ratio, or the gas to oil ratio, at the production well or wells until the point is reached at which it becomes Aeconomically unsound to continue the flooding or driving operation, and the wells must be abandoned even though the oil content of the formation is far from exhausted. A number of procedures are practiced in the art to improve the yield of oil by secondary recovery such as for example, the selective `plugging of the more permeable strata, but such methods have thus far proved to be of Vminor value.

It has now been found that sonic or supersonic vibrations when impressed upon an oil-bearing formation provide a method for markedly increasing the efficiency of a fluid or gas drive process. The vibration of the oil-bearing formation supplements the energy supplied by liquid ooding or gas driving processes thereby increasing the net yield of oil over that which would be obtained by the usual liquid ooding or gas driving processes. The formation can also be vibrated prior to the flooding or gas driving operation in order to dislodge a part of the oil from the less permeable areas thereby placing it in a condition to be more easily removed by the subsequent ooding or driving operations. Alternatively, the formation undergoing secondary recovery can be either heated or simultaneously heated and vibrated by employing high frequency Waves, or complex waves derived from both low and high frequency vibrations.

A primary object of this invention is to stimulate oil production prior to and/or during the liquid flooding or gas driving of oil-bearing formations by means of sonic or supersonic mechanical vibrations.

It is another object of this invention to agitato and/or heat oil-bearing formations undergoing secondary recovery by the application of high and/or low frequency vibrational energy to the formation. y

Another object of this invention is to. reduce undesirable channeling of the driving agent through the oil-bearing formation during a secondary recovery operation through the use of mechanical vibrations.

Another object of this invention is to increase the ratio of oil to Water obtained from the production wells during the ilooding of oil fields.

It is another object of this invention to employ sonic and/or supersonic pumps for introducing the driving liquid into an oil-bearing formation from an input Well during a secondary recovery operation and/or for removing the oil from the oil-bearing formation at an output well, which sonic and/or supersonic pumps simultaneously impart vibrational energy to the liquid being pumped, a part of which energy is in turn imparted to the oil-bearing formation uri-- dergoing secondary recovery and thereby increasing the yield of oil.

Briey, this invention relates to the iiqud flooding :or gas driving of oil within an :oil-'bearing formation wherein sonic or supersonic mechanical vibrations are impressed upon the oil'- bearing formation prior to and/or during the operation to enhance its efciency. 'The essential elements for carrying out this invention include a means for supplying the driving huid under sufcient pressure to force it into the `oil-bearing formation, one or more sonic or supersonic wave generators, a transducer and transducing medium to couple the vibration generating sys tem to the oil-bearing formation to be vibrated and a pumping system for removing the oil from the oil-bearing formation at a point away from the introduction of the Adriving huid. The driving fluid may be any suitable gas or liquid.

The means for supplying the driving fluid to the oil-bearing formation include centrifugal pumps, reciprocating pumps, sonic pumps, compressors and the like. The sonic Aor supersonic wave generator may be any mechanically or electrically driven wave generator capable of introducing large amounts of mechanical vibrational energy into the oil-bearing formation. Suitable generators may be purely mechanical types such as any of those which are described hereinafter, piezo-electric crystals coupled with low or high frequency koscillating electrical currents, magneto-strictive devices `and the like. The transducer and transducing medium comprises any suitable arrangement for coupling the mechanical vibrations generated by the wave generator to the oil-bearing formation. The transducing `medium is preferably solid or liquid. Under certain limited conditions such .as those which prevail in high pressure `formations gaseous media may be employed. However, .gases tend to absorb the mechanical vibrations thereby decreasing the intensity of the transmitted wave. In the specific case where 4a driving fluid is a liquid which is introduced into the Aoil-bearing formation by means of a sonic pump, the driving liquid itself may function as the coupling between the sonic vibrating generator and the formation to be vibrated. In other cases the transducer may comprise a solid metallic rod fastened 'to the wave generator and coupled to the oil-bearing formation through a large block of cement, concrete, plastic, melted or solidified alloys, various liquids, .or other material lodged within or in the vicinity of the oil-bearing formation. In any case oil is removed from the oil-bearing formation at an output well by conventional reciprocating oil pumps, by sonic pumps or by anyother suitable means.

Figure 1 shows one modification of the invention wherein a sonic pump is employed to introduce the driving liquid into the formation vand to impart vibrational energy to the formation simultaneously. The stripped oil is removed from the formation by means of a conventional pump.

Figure 2 shows another modication of this invention wherein sonic pumps are employed to introduce the driving liquid and to remove the stripped oil and wherein a wave generator is coupled to the formation to supply additional vibration energy to the formation.

Figure 3 shows another modification of this invention wherein conventional pumps are employed to introduce the driving liquid into the formation and to remove the stripped oil and wherein a wave generator is coupled to the formation to supply vibrational energy thereto.

Figure 4 shows one modification of a sonic check walve which is spring loaded `from .the underside to cause downward fluid flow in a son-ic pumped injection well. For upward fluid iiow such as in a sonic pumped output well the check valve shown in Figure .eis merely inverted and mounted in the pump tubing.

.Figure 5 shows Aa section taken along the line 5-5 of Figure 4.

Fig-ure 6 `shows a modication of the invention shown in Figure 2 wherein a conventional gas drive apparatus injects a gas into the formation land wherein a wave generator of the magnetostrictive type is coupled to the formation to sup- .ply additional vibrational energy to the .formation; as in Figure 2 the oil is removed from the formation by means of a sonic pump.. Apparatus common to Figures 2 and 6 carry the same reference numerals.

Figure l shows one means for directing yor focusing sound energy into .a chosen region of the formation wherein piezoelectric crystal 30 is actuated by alternating current source |31 and the vibrational energy generated thereby is .reflected from element 132.

Figure 8 shows another means for directing 'or focusing sound energy into a chosen region of the formation wherein piezoelectric -crystals V and |35 are actuated Yby alternating current source |31 and the vibrational energy .generated thereby is reflected from element 133.

Figure 9 shows .a heater for heating the Aformation during vibrating and injection of a driving fluid.

In the modification of this invention shown in attached Figure 1, the driving liquid is injected into the formation by means of a sonic punrp which also serves to vibrate .the oil-bearing formation surrounding and in the neighborhood of the point of entry of the driving liquid, thereby agitating the oil and dislodging it from the less permeable formation and permitting it .to `be swept by the driving liquid toa conventional :production well where it is removed from the forniation and transported to the earth surface. The .driving liquid itself, together with the pumping unit, function as the transducing medium yfor transmitting the vibrational energy to the formation .and to a block embedded in the formation which provides added coupling to the formation. Sonic pumps which are suitable for use `throughout this invention are known and have been described in U. S. Patent 2,355,618 to A. G. Bodine.

Referring more particularly to attached Figure l, the injection or input well is cased with well casing 28 which extends from the earth surface down to a transducing mass such as cement block 28 containing a duct 3'! which permit the flow of ydriving' liquid through ports 3E into oil-bearing formation 32 surrounding the cement block 28. Well casing 2E is fitted at the surface with casing head 25 .and packing gland 24. Pump tubing 23 is joined to vibratory housing 3e at junction 22, passes through packing gland 24 and extends almost to the bottom of casing 2E, passes through sealing gland 2e and joins the duct system yof ce- :ment block 23.

Pump tubing 23 is fitted with a number of sonic check valves, only two of which have been .shown Y as 21 and 21a. The check valves are so positioned -in the pump tubing 23With respect to each other and with respect to junction 22that kwhen vibrations of the desired sonic frequency are impressed on the system by wave generator 3S there is a net transfer of liquid down the pump tubing 2 3.

The sonic check valves for causing the downward fluid flow for example, may be spring loaded from the underside to permit the. downward liquid iiow under the action of a compressional wave from junction 22 andV areclosed by a wave of rarefaction to prevent the reverse iiow. A check valve of this type is shown in Figures 4 and 5. This particular check valve comprises a section of pump tubing |I, the end of which is fitted with a valve plate |02 containing four holes |03 which are located symmetrically about center of the valve plate. The bottom side of each of the four holes is normally covered by a single Washer shaped pressure plate |04 which is spring loaded from the lower side. The spring |05 is held in place by a Washer |05 and bolt |01 which is threaded into the center of the `valve plate |02 from the underside. Under the action of a pressure wave striking the upper or intake side of the valve, the pressure plate |04 is opened to permit a momentary surge of liquid to flow through the uncovered holes |03. Following the liquid surge the pressure plate |04 is pushed against the holes by the action of the spring I05`and prevents the reversed liquid flow until the next pressure wave again opens the pressure plate |04. It is apparent that the inversion of the check valve will produce a net upward fluid flow such as is required to pump liquids from the formation as is hereinafter described.

Referring again to Figure 1, motive means l5 drives wheel i6 through connecting drive belt 35 thereby rotating meshed gears I1 and I8 in opposite directions. Gears l1 and I8 are geared to eccentric heavymasses I9 and 20 respectively, which rotate in opposite directionsp The rotation of eccentric masses I9 and 20 is symmetrical and the centerof mass of the system has no horizontal movement during the rotational cycle. The net resultant of all horizontal forces is therefore zero. The center of mass for the system is continually shifted along a vertical axis during the rotation of I0r and 20 thereby producing alternate upward and downward thrusts on vibratory housing 30, which is mounted through springs 2| to stationary support 34. Through the rotation of masses I0 and 20, housing 30 is set into sonic vibratory motion at a frequency which is dependent upon the rotational speed of motive means I5.

The driving liquid, which also serves as a transducing medium, flows from storage tank |I through line I2 controlled by valve I3l into line I4 and into pump tubing 23. The vibration of housing 36 is transmitted through pump tubing 23 and the liquid contained therein. y The transmitted waves actuate sonic check valves 21 and 21a as well as the other check valves not shown thereby causing the downward flow of the liquid through tubing 23. the liquid flows through duct 31 and out of ports 30 into oil-bearingformation 32 in surgeswhich are of the same frequency as vibratory housing 36. The pulsating of the tubing and the liquid causes the cement block to vibrate thereby setting up a vibration pattern throughout a surrounding region of formation 32. The vibration of the formation cooperates the driving force of the liquidto;

,sweep the oil ahead of the water flow toward the output well. n. l

`At some distance from the input well there is located an output well for the removal of the oil which has been dislodged and driven from the formation as a result of the sonic vibrations and liquid drive. The output well is cased with Well casing 50 which extends from the surface somewhat into oil-bearing formation 32. The well bore throughthe oil-bearing formation may be lined with perforated liner 5I containing perforations 53 through which the oil from the oilbearing formation 32 flows and gathers in liquid pool 63 in the bottom of the Well bore. Pump tubing 52 extends into the oil pool B3 and is tted with standing valve 54 which permits an upward liquid flow and prevents the reverse flow. The upward fluid flow is maintained by traveling valve 55 which is actuated by sucker rod 56 which is in turn actuated by motive means at the earths surface not shown. Well casing 50 is sealed with casing head 51 which is fitted with packing gland 58 through which pump tubing 52 emerges. The liquid flow from pump tubing 52 enters line 59 controlled by valve 60 and passes through line 6I into product storage tank 62.

In the modification of this invention shown in Figure 2 the driving liquid is introduced into the formation by means of a sonic pump which also serves to impart sonic vibrations to the formation surrounding the point of entry of the driving liquid. The formation is also vibrated by a wave generator through a transducer at a point removed from the input well. The oilbearing fluid is removed from the outputwell which is in turn pumped by a sonic pump which alsoimparts sonic vibrations to the oil-bearing formation surrounding its location. Y

Referring more particularly to attached Figure 2, the injection or input Well is cased with well casing 22 which extends somewhat intoI oilebearing formation 28 and is fitted with perforated liner 25 containing perforations 26 through which the driving liquid is forced into oil-bearing formation 28. Well casing 22 is fitted at the surface with casing head 24 and packing gland 20. Sonic pump tubing 23 is fitted at the top with reciprocating piston I8 and the tubing extends through packing gland 20 to near the bottom of the bore hole. The pump tubing 23 is also fitted with several sonic check valves, only two 0f which are shown as 24 and 24a. These check valves may be spring loaded from the bottom side and open during the compressional wave travelling from the top of the tubing to permit a downward iiow of liquid and close on the rarefaction wave to prevent a reverse upward flow. The design and operation'of such valves has been described hereinbefore. V l

Motive means I5 rotates shaft l0 which is coupled to connecting rod I1 by means of an eccentric cam arrangement not shown in detail, which arrangement produces a reciprocatingI vertical motion to piston I8. The stroke of the pistonis adjustable by varying the eccentricity of the cam employed.

The driving liquid, which also serves `as a transducing medium, flows from storage tank II through line |2 controlled by valve |3 and through line .I4 into pump tubing 23 under the sonic pumping action produced by the `reciprocal motion of piston I3 on the driving liquidcontainedin pump tubing 23 wherein the fluid flow is in turn controlled by sonic check valves 24 and 24a and the others not'shown. "The driving rod or pipe 43 moves freely'. Casing 46 is fitted near the bottom of the well with mounting 33 which is fitted With packing gland 41 through which conductor 43 is permitted to move. Radiation surface y48 is attached to the lower end of conductor 43 and radiates the transmitted wave energy from wave generator 50 to transducing medium 49. The transducing medium is, for example, water, crude oil, molten sulfur, low melting alloys, mercury or any other suitable liquid for the transmission of vibrational energy from radiation surface 48 to the surrounding oil-bearing formation 32. The conical shape of radiation surface 48 and the vertical reciprocating motion produced by wave generator 34 results in a series of horizontal vibrational waves which agitate the liquids in the surrounding formation and assist in the stripping action of the liquid ooding for removing loil from the formation. Radiation surfaces other than cones such as discs, elipses and the like may also be employed.

At some distance from the input well there is located an output well for the removal of the oil which has been dislodged and driven from the formation as a combined result of the vibrations and liquid drive. The output well'is cased with well casing 50 which extends from the surface somewhat into oil-bearing formation 32. The well bore through the oil-bearing formation may be lined with perforated liner I containing perforations 53 through which the oil from the oilbearing formation 32 flows and gathers in liquid pool 63 in the bottom of the well bore. Pump tubing 52 extends into the oil pool 03 and is tted with standing valve 54 which permits an upward liquid flow and prevents the reverse flow. The upward uid ow is maintained by traveling valve 55 which is actuated by sucker rod 56 which is in turn actuated by motive means at the earth surface not shown. Well casing 50 is sealed with casing head 51 which is fitted with packing gland 58 through which p-ump tubing 52 emerges. The liquid flow from pump tubing 52 enters line 59 controlled by valve 60 and passes through line 6| into product storage tank E2.

The foregoing description and discussion of this invention has been primarily directed toward the application of sonic waves to improve liquid fiooding operations. However, it is understood that my invention may employ either sonic or supersonic waves, and that such vibrational waves may be employed in both liquid flooding and gas drive secondary recovery operations in order to dislodge and strip oil from an oil-bearing formation.

Frequencies in the subsonic and lower sonic range of about 10 to 5,000 and preferably 20 to 2,000 cycles per second provide the greatest amount of agitation of the oil in an oil-bearing formation with a minimum loss of mechanical energy to the production of heat. Vibrations of these frequencies which are sinusoidal in nature are easily generated by mechanical means such as have been described hereinbefore and can be employed to establish resonant vibratory states in most oil-bearing formations. Lower frequency waves are most useful in dislodging higher gravity crude oils such as those whose A. P. I. gravity at 60 F. is greater than about 20 in which case mechanical energy alone suffices to dislodge the trapped oil particles.

In certain other cases, such as when the crude oil to be dislodged has an A. P. I. gravity at 60 F. of less than 20, it is desirable to employ high frequency vibrations in the upper sonic and/or 10! in the supersonic range such as between about 5,000 and 100,000 or higher in order to heat and agitate the formation simultaneously thereby decreasing the viscosity of the crude oil and rendering it more susceptible to the purging action of the driving liquid or gas. The heating of the formation by upper sonic and/or supersonic vibrations has the advantage over heat transfer type heating agents such as steam, hot water, and

the like, in that the problem of heat transfer` through poorly conductive formations is largely eliminated. It is apparent, however, that vibrational shaking with or without heating by vibration together with heating by heat transfer means, such as is shown in Figure 9, may be employed conjuctively in the application of this invention wherever this is desirable for economic or other reasons.

Vibrations in the upper sonic and supersonic' range for use in agitating and/or heating'oilbearing formations .can be generated, such as in Figure 7, by impressing a high frequency alternating electrical current from source |3l, pro` duced by suitably amplifying the high frequency" currents produced by a vacuum tube oscillator,- across the polar axis of a piezo-electric quartz ing magnetic field produced by impressing a high frequency alternating current from source |22 across a suitably designed coil |23. Vibrations transmitted from nickel rod |24 to coupling rod 53 are then transmitted to the oil-bearing formation 2S in the manner which was described hereinbefore in connection with Figure 2. The construction of these and other devices is well known in the art.

In certain instances it is desirable to employ' complex or modulated vibrational waves derived from the combination or addition of two or more sinusoidal waves of dissimilar frequencies.' The component waves of the complex wave may, for example, bear a harmonic relationship to each other, i. e., the frequency of all but one of the component waves may be an integral multiple of the frequency of the one fundamental wave. As an example of the use of such componded wave forms, a fundamental sonic wave is gener'-v ated with any suitable generator and is transmitted to the formation through a transducer. A second wave generator is employed to generate a wave having a frequency of, for example, '7, 8, 9, or l0 times that of the fundamental frequency and is also coupled to the formation by a separate transducer or by a transducer which is also common to the generator producing the fundamentalA frequency. Figure 2 shows a modification of the invention wherein a total of three lsonic Wave generators are employed which may be employed f- .for the generation of compounded wave forms( transducing mass 6&3. A second wave generator'v actuated by motive means l5 is employed to generate a wave having a frequency of?, 8, 9 or 10' times that of the fundamental frequency. The

second wave generator is coupled to the formation through the transducing medium of the water u .being injected. =The third wave generator actu- Such vibrations can also be proated by :motive means 8|)Y yand coupled to the formation through the liquid medium of the oil being produced 'from the formation 'may be lvoperatedat any desired frequency which may, or may not, be the same as that of either of the first two wave generators. The formation is vibrated by the higher frequency Wave l,and Vintermittent'ly receives a boost or kick vibration as a result of the pressure wave of the lower frequency vibration. Complex waves of this type are yoften more `effective vthan simple sinusoidal Waves and particularly in those formations where resonant vibratory conditions .are ydifcult to establish. It is apparent that the relative amplitude of each of the wave forms can be varied in order to provide the maximum amount of agitation within the formation as is evidenced by the increased rate of oil production at the output well orwells.

It is apparent from kthe foregoing illustrations of this invention that I'may .employ one or more sonic or ultrasonic vibrational generators and transducers to vibrate an oil-hearing formation from one ormore locations. Such vibrations may he of identical or differing `frequencies such as has been discussed hereinbefore. In the event that the vibrations are all the same frequency, or `posses frequencies which vare simple integral multiples ofthe frequency of one of thevibrations, it is desirable but not necessary that a condition of synchronism exist `bei-,Ween the transducersV of the. various sources of vibration in the formation through the coupling racton of the formation. Where conditions `are conducive to the establishment of a condition of `resonance the motive means-of the generators tends to convert to a resonant condition. Any tendency towards departure resonant state results `in a marked decrease of the `load on the 'motive means, thereby tending 4.to speedup the motive means in order to maintain or .establish Vthe resonant condition. At the resonant state, the accumulated mechanical energy in the formation increases to a value considerably in excess of that which is supplied to the system with the result that a maximum agitation of the oil particles in the formation is obtained .at the yresonance state for a given amount of =vibratic-ma'l energy supplied to the system.

Although the transducers described hereinbefore in connection with attached figure are user ful 4in the application of this invention, other transducers may be yemployed which direct and focus the. vibrational energy along a given band or `Zone. Thus, radiators or reflectors `may be placed in the formation and coupled -to `or used in conjunction with transducers, such as those radiators or reectors which are substantially parabolic troughs .as shown in Figure A8. The vibrations radiating and/or reflected by such radiators are focused in a controlled band and can be focused yor beamed in any direction toward any desired objective. Similarly, radiators or reflectors can be employed which are paraboloids or paraboloidal in nature, as shown in Figure '7, in order to focus and direct the waves in a beam along a predetermined direction or toward a desired objective. Such radiators or reectors should be of such dimensions that the effective focal length -of the paraboloids in place in the formation is about one-quarter of the `wave length of vibration being employed or an vodd multiple thereof.

Although most of the foregoing discussion and description has pertained to the use of both sonic and supersonic vibrations in conjunction liquid flooding operations, the use of vibrational energy is equally applicable to gas drive operations. Gaseous media tend to absorb both sonic and supersonic vibrations with an attendantrgeneration of heat and diminution of the wave ,intensity. Accordingly, in gas drive operations it is desirable that the sonic orsupersonic generator and transducer be located between the injection and output Wells in such a manner that thetransducer contacts substantially a liquid phase, thereby facilitating the vtransmission of the undiminished wave front throughout the liquid phase of the oil-bearing formation. Operation .at `high pressures also facilitates the transmission of the vibrations through the gaseous phase. these conditions there is a minimum conversion of the mechanical energy to heat and a maximum utilization of the vibrational energy for the agitation of the format-ion at a given Wave energy" input. The situation is shown inFigure l6, which is a modicationof the invention shown in Figure 2, wherein the vliquid injection system on the far left-hand side of Figure 2 is replaced tby "a 'gas injection arrangement |2l of the type normally employed in gas drive operations for forcing air, fiue gas, naturalgas and the like supplied through line I-Zinto oil-bearing formation 28, and Wherein a wave generator of the magneto-strictive type is employed to vibrateoil-bearing formation 28 as described herei-nbefore.

Having fully described and illustrated my invention I claim:

l. A process for the production `of petroleum which comprises generating vibrations vof `a lower freuueny with one wave generator, Agenerating vibrations of a higher frequency with a second wave generator, coupling both generators `to .an oil-bearing formation thereby vibrating said oilbea-ring formation with a non-'sinusoidal vibration Wave, forcing a driving iin-id through said oil-bearing formation simultaneously with said vibrating, and producingoil from 4said Toil-bearing formation.

2. The process of claim 1 wherein the driving fluid is water.

3. In a secondary recovery process wherein a driving fluid is forced into an oil-bearing formation through an input Well and Apetroleum is recovered from an input Well located `somo distance from said input Well, the improvement which consists in locating a first vibrational Wave generator at the earths surface adjacent -to said input well, coupling said first generator to the oil-bearing formation adjacent said input well, locating a second vibrational Wave generator at the earths surface adjacent said output well, coupling said second generator to the oil-bearing formation adjacent said output Well, and simultaneously generating vibrational waves by means of said first and second generators While said driving fluid is forced into the oil-bearing forma-- tion through said input well and while said petroleum is Arecovered from said output Well, said generators being operated at different frequencies thereby vibrating said oil-bearing formation with a non-sinusoidal vibrational wave substantially continuously during the forcing vof said driving fluid thereinto and during the recovery of petroleum therefrom.

4. The process of claim V3 `wherein the 'driving uid is Water.

'5. In a secondary recovery process wherein `a driving fiuid is forced into an oil-bearing formation through an input well and petroleum is re covered from an output well located Asamedis- Under 13 tance from said input well, the improvement which consists in locating a first vibrational wave generator at the earths surface adjacent to said input well, coupling said first generator to the oil-bearing formation adjacent said input Well, locating a second vibrational wave generator at the earths surface adjacent said output well, coupling said second generator to the oil-bearing formation adjacent said output well, locating a third vibrational wave generator at the earths surface adjacent a, third well penetrating the oil-bearing formation at a point intermediate between said input and output Wells, coupling said third generator to the oil-bearing formation adjacent said third well, and simultaneously generating vibrational waves by means of said first, second and third generators while said driving fluid is forced into the oil-bearing formation through said input well and while said petroleum is recovered from said output well, at least two of said generators being operated at different frequencies thereby vibrating said oilbearing formation with a non-sinusoidal vibrational Wave substantially continuously during the forcing of said driving uid thereinto and during the recovery of petroleum therefrom.

6. The process of claim 5 wherein the driving fluid is water.

7. In a secondary recovery process wherein a driving fluid is forced into an oil-bearing formation through an input well and an effluent fluid is recovered from an output well located some distance from said input well, the improvement which consists in coupling a vibrational wave generator to the driving fluid in said input well, coupling a second vibrational Wave generator to the eilluent fluid in said output well, and simultaneously generating vibrational waves by means of said vibrational wave generators while said driving fluid is being forced into said formation through said input well and while said eluent fluid is recovered from said output well. said 14 wave generators being operated at different frequencies and thereby vibrating said formation with a non-sinusoidal vibrational wave substantially continuously during the forcing of said driving fluid thereinto and during the recovery of petroleum therefrom.

8. In a secondary recovery process wherein a driving lluid is forced into an oil-bearing formation through an input well and an efIluent lluid is recovered from an output Well located some distance from said input well, the improvement which consists in coupling a vibrational Wave generator to the driving fluid in said input Well, coupling a second vibrational wave generator to the eiuent fluid in said output well, coupling a third vibrational wave generator to said formation at an intermediate point between said input and output Wells, generating vibrational waves by means of said three vibrational wave generators while said driving fluid is being forced into said formation through said input well and while said effluent fluid is recovered from said output well, at least two of said three vibrational Wave generators being operated at different frequencies thereby vibrating said formation with a non-sinusoidal vibrational Wave substantially continuously during the forcing of said'driving uid thereinto and during the recovery of petroleum therefrom.

J OI-IN E. SHERBORNE.

References Cited in the ille of this patent UNITED STATES PATENTS l Date

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