US3057404A - Method and system for producing oil tenaciously held in porous formations - Google Patents

Description

Oct. 9, 1962 E. v. BERGSTROM 3,057,404

METHOD AND SYSTEM FOR PRODUOING OIL. TENACIOUSLY HELD IN POROUS FORMATIONS 2 Sheets-Sheet 1 mm. mz3 NLE O... mM.

3,057,404 cIoUsLY Oct. 9, 1962 E. v. BERGSTROM METHOD AND SYSTEM FOR PRODUCING OIL TENA HELD IN POROUS FORMATIONS 2 Shee'lzs--Sheefl 2 Filed Sept. 29, 1961 F/GZ CUTTING OIL INVENTOR.

A f/ofney nite 3,057,404 Patented Oct. 9, 1962 tice 3,057,404 METHD AND SYSTEM FR PRDUCING OIL TENACEUSLY HELD IN PRUS FORMATONS Eric V. Bergstrom, Byram, Conn., assigner to Socony Mobil Gil Company, Inc., a corporation of New York Fiied Sept. 29, 196i, Ser. No. 141,844 7 Claims. (Cl. 166-8) This application is a continuation-in-part of my prior application, Serial Number 708,678, tiled on January 13, 1958 for Method and System for Producing Oil Tenaciously Held in Porous Formations.

Throughout the United States, Canada and possibly in other countries, there exists vast deposits of oil in Athabasca tar sands and other formations. This oil, which may be of high viscosity, is tenaciously held in these formations to the extent t-hat, although a well is drilled into the formations, the oil will not ow of its own volition into the well so that it can be produced. Heretofore, such oil has been produced by a strip mining method followed by ythe separation of the oil from the sand. This method of producing such oil has met with some success but can only reach oil existing in relatively shallow formations. Although this prior method seems economically practical, it is subject to criticism in that it is limited to the recovery of oil underlying an overburden not exceeding 50 feet. For economic reasons, it is impossible to produce more than of the available oil so held due to the fact Ithat 95% of such formations are more than 50 feet deep. To approach depths of 50 to 100l feet by the strip mining method is obviously out of the question. Additionally, strip mining destroys the surface acreage from an agricultural point of view.

The present invention contemplates a method for producing oil from strata that exist at depths of from 50v to I1000 feet and even more below the earths surface. The instant method employs procedural steps, some of which are well known in the prior art in connection with a method for producing cavities in salt formations for the purpose of storing liquid petroleum gas and in the process of producing sulphur underlying a considera-ble overburden. The instant invention contemplates a method for the production of such oil which involves drilling a well from the surface to the upper face of the formation containing the oil, setting casing, then lowering into the Well tubing of lesser diameter than the casing through which air, steam and a cutting oil can be introduced. When this mixture strikes the formation containing the oil, it serves to heat and cut the oil to the extent that, for example, in an Athabasca tar sand, the oil will be thinned and will flow, thereby loosening the sand in which it was formerly trapped. The air, as a circulating agent, will maintain the sand in suspension in the circulating uid and force it to ow upwardly in the space between the tubing and the casing to the surface where the sand and iluid may be accumulated in a reservoir. This sand, having had the oil released therefrom, will settle to the bottom of the reservoir and water, due to steam condensation, will form a stratum immediately overlying the sand, while the cutting oil and the oil released from the sand will form a top stratum which can be pumped off and processed for tank storage, pipe line or further use. In order for the input steam, cutting oil and air to form an increasingly larger cavity in the formation being produced, the bottom end of lthe inlet tubing, which was initially adjacent the bottom end of the casing, is continuously lowered, while circulation progresses, to form a maximum cavity in the formation.

Therefore, the primary object of this invention is to produce oil which may be of high viscosity and be tenaciously held in the pores of formations to such an extent that it will not flow therefrom of its own volition. An-

other object of the invention is to recover oil from formations such as Athabasca tar sand and similar formations without resorting tothe Well known strip mining process. This invention also contemplates a method for producing oil from formations by which it is tenaciously held by the introduction of a cutting oil, steam and air. A further object of this invention is to use steam and a cutting oil for releasing oil from formations which tenaciously hold it and the use of air for producing circulation currents therein which will cause the mixture of sand, steam and oil to seek an outlet at the surface of the earth from which it can be conducted to a storage reservoir for separation. Still another object yof the instant invention is to accumulate the sand, water and oi-l in la surface reservoir in the manner described above and, by dredge pump, remove the sand therefrom and deposit it in previously formed caverns to thereby displace the oil and water contained therein to the reservoir for storage, pipe line or other requirements. Other objects and advantages of the present invention will become apparent from the following description when taken with the drawings in which:

FIGURE 1 is a schematic view which is in part a How diagram and in part a vertical sectional view of the earths surface showing the manner in which oil is recovered from a selected formation.

FIGURE 2 is a plan view showing the location of a surface reservoir, its associated pumping equipment and the manner in which recovery wells would be spaced over an area that is to be produced by the instant invention.

FIGURE 3 is a fragmentary, sectional View of the earths surface illustrating a slightly modified form of production which can be used where the formation to be produced is stratified with clay or rocks or contains gravel which would tend to choke oif circulation.

FIGURE 4 is a detailed, vertical, sectional View of the equipment that would be used in an operati-on as disclosed in FIGURE 3.

FIGURE 5 is a vertical elevation of the well head equipment that wou-ld be used on each well that is sunk into the producing formation.

Referring to the drawings in detail, particularly FIG- URE 1, there is illustrated in vertical section a frag-ment of the earths surface showing a formation 10 which may be tar sand that contains oil tenaciously held therein under insuflicient pressure head to flow into a well penetrating the formation. There is also shown in this ligure, schematically, a ow diagram which would be employed in the application of the instant invention to the production of oil from these tar sands underlying a substantial overburden. In order to release the oil from the tar sands, steam produced by a boiler plant 11, compressed air from air compressors 12 and a cutting oil from reservoir 21 are mixed and introduced into tubing 13 that is disposed within a drill hole 14. The steam and air are mixed at 9 and caused to iiow by means of laterals 8 into a pipe 7 which leads to the tubing 13 in the respective drill holes. At the point of introduction of the mixed air and steam into pipe 7, the cutting oil from reservoir 21, flowing through pipe 6 is mixed with the air and steam mixture to provide the air-steam-cutting oil mixture that is necessary in the operation. Drill hole 14 may or may not have casing 15 set therein. When cased, casing 1S extends from the surface to the top of the tar sand formation 10, tubing 13 is inserted in the well casing through a packer 16, or other conventional sealing means. The mixed fluid, which is at an elevated temperature, is introduced by way of the tubing into the formation and produces a return ow to the surface in the space between the casing 15 and the tubing 13. The circulation of this mixed fluid will, in the manner illustrated by wells 14, 17, 18 and 19, cut the oil tenaciously held by the tar sand and, in so doing, release particles of sand which will be carried to the surface by the return ow of the injected mixed fluid and released oil. The temperature of the injected fluids are so adjusted, as to achieve a temperature surrounding the bore-hole suiiicient to permit the condensation of steam (with concurring heat release) to water, giving rise to a mixed fluid consisting of water, air, and formation oil thinned by cutting oil. Temperatures are of the order of 150 F. to 212 F. (or slightly higher in deeper Working where pressure permits condensation of steam at slightly higher temperatures). At any rate, the temperature is so adjusted as to secure a mixture of air, water, oil, and sand, which vmay be flowed to the surface and there be separated in the manner hereinafter described. At the surface, this mixture is conducted by pipe line 20 to reservoir 21. It will be noted that the circulating fluid, in the removal of the oil and sand particles, will produce a cavity in the formation that will grow in size with the continued circulation of the heated mixed fluid. Depending upon the formation, these cavities may be as much as 80 feet in diameter. By lowering the tubing 13 while fluid is being circulated, the depth of the cavity can be extended to the bottom of the formation.

At the reservoir 21, air is separated from the fluid and sand mixture flowing into it from pipe line 20 by a separator 22. The oil and water owing into the reservoir will naturally separate themselves into different layers while the sand particles will settle to the bottom of the reservoir. The sand particles are removed by a dredge pump 23 and conducted by a pipe line 24 into previously formed caverns 25, 26, and 27. The introduction of the sand into these previously formed caverns will displace any water and oil contained therein. Since each of these Caverns, 25, 26 and 27, have been previously formed by the use of wells equipped with casing and tubing in the manner described in connection with wells 14, 17, 18 and 19, the sand is introduced through the tubing and the water and oil displaced thereby is caused to flow back to the reservoir 21, exteriorly o-f the tubing, but, within the respective casings. Return flow to the reservoir is by means of pipe line 28.

Cutting oil and released formation oil, together forming the stratum 29 in the reservoir, may, by means of a pump 30 and pipe line 31, be conducted to storage facilities such as illustrated by the tank 32. This mixed oil may be of such a viscosity that it can be introduced directly into a transportation pipe line 33. In any event, some of it must be processed to provide a cutting oil for continuing the operation. By a cutting oil is meant an oil of relatively low viscosity. Such processing may consist of charging the oil, with or without prior separation of the lighter fractions thereof by distillation, into a conventional viscosity-breaking and/or coking operation as known in the petroleum refining industry. In viscositybreaking the oil is subjected to elevated temperatures and pressures, preferably in a heated coil mounted in a furnace or heater 34 for a time suicient to reduce a suitably large fraction of heavy oil of high viscosity to an oil of gas oil nature; that is, an oil boiling in the general range of about 500 F. to about 700 F. and having a relatively low viscosity. This gas oil will be separated from heavier oil in a conventional fractionator 35. Also, it is contemplated that a conventional coking operation, not shown, could be used wherein a large percentage of a heavy oil is reduced to gas oil nature, some is changed to oil of the nature of gasoline, while the remaining small percentage is changed to a solid coke. The processed cutting oil may be returned to the producing system by pipe line 36. The heavy fractions can be conducted to the boiler plant 11 by pipe line 37 Where it is used as fuel for the production of the steam needed in the operation.

The invention, as described to this point, finds application to a clean sand formation; that is, to a tar sand formation which is relatively free of rock or clay stratilcation. Where rock or clay stratification is encountered, a modified form of the instant invention is employed. This modification is illustrated in FIGURESS and 4. Since rocks, in the form of gravel or clay, would tend to clog circulation, a second casing, which is perforated for a distance that is equal to the thickness of the formation, is used. Otherwise, the cased drill hole and tubing, through which the mixed fluid is introduced, are the same as those previously described. In this instance, the well is drilled completely through the formation from which oil is to be produced. Casing -15 is set therein, terminating at the top of the sand formation. Tubing 13, as previously described, is introduced through packing means 16. Concentrically disposed between the casing 15 and tubing 13 is a perforated casing 38. Casing 33 extends completely through the formation from which the oil is to be produced. Perforated casing 38 will serve to prevent rocks and clay from blocking the circulating fluid that is introduced through the tubing 13. As shown in FIG- URES 3 and 4, these rocks will accumulate in the bottom of the cavern formed by the circulating fluid and will be restrained by the perforated casing from blocking the fluid, which is being introduced through the tubing 13.

Since the caverns produced by this method of recovering oil from sand formations may be economically made having diameters up to feet, well locations may be made on the surface as illustrated in FIGURE 2. Using the scheme for locating the wells as shown in this ligure, each well would be drilled at the apexes of equilateral triangles that are 80 feet on each side.

Formations containing oil that can be recovered by the instant invention normally range in depth from a few feet to as much as 1000 feet. Therefore, the wells used can be drilled by conventional portable drilling rigs, such as are employed in drilling shot holes for seismic prospecting or in core drilling.

Although the instant invention has been described in detail with application to the recovery of oil from a sand formation such as an Athabasca tar sand, it is obvious that it iinds application in the recovery of oil from any formations that can be broken down by a circulating fluid and particles thereof transported to a surface reservoir where the fluids and formation particles can be separated.

I claim:

1. A method of producing oil of high viscosity from a formation in which it is held tenaciously to the extent that it will not flow into a well which penetrates the formation that comprises drilling a hole to the upper face of the formation, setting casing therein, placing tubing of a lesser diameter within said casing so that its lower end contacts the formation, circulating air, steam and a cutting oil at an elevated temperature downwardly through said tubing, the temperature and quantity of said fluids being such as to induce separation of oil and sand, to disrupt the formation, producing a continuously expanding cavity therein, to maintain formation particles in suspension, to produce a fluid mixture comprising water condensed from the steam, air, and oil, and producing a return flow to the surface of the fluid mixture, released formation oil and particles of the formation, through the casing exteriorly of the tubing, continuously lowering said tubing in the cased drill hole while said uid mixture is being circulated to increase the extent of said cavity while releasing particles of the formation and oil contained therein.

2. A method of producing oil from a formation in which it is held tenaciously to the extent that it will not flow into a well which penetrates the formation that comprises drilling a hole to the upper face of the formation, setting casing therein, placing tubing of a lesser diameter within said casing so that its lower end contacts the formation, circulating a fluid mixture comprising air, steam and a cutting oil at an elevated temperature downwardly through said tubing, the temperature and quantity of said uids being such as to heat the material adjacent the bore hole and fluid therein to a temperature of the order of 15G-212 F., to induce separation of oil and sand, to disrupt the formation, producing a continuously expanding cavity therein, to maintain formation particles in suspension, and producing a return flow to the surface of the fluid mixture, formation oil and particles of the formation, through the casing exteriorly of the tubing, continuously lowering said tubing in the cased drill hole while said fluid mixture is being circulated to increase the extent of said cavity in the formation, at the surface separating air from the fluid-particle mixture, and collecting the remaining uid, and particles in a reservoir.

3. A method of producing oil from a formation in which it is held tenaciously to the extent that it will not ow into a well which penetrates the formation that comprises drilling a hole to the upper face of the formation, setting casing therein, placing tubing of a lesser diameter within said casing so that its lower end contacts the formation, circulating air, steam and a cutting oil at an elevated temperature downwardly through said tubing, the temperature and quantity of said fluids being such as to produce a fluid mixture of air, oil, and water within the bore-hole at a temperature of the order of 15G-212 F., to induce separation of oil and sand, to disrupt the formation, producing a continuously expanding cavity therein, to maintain formation particles in suspension, and producing a return flow to the surface of the fluid mixture, forma-tion oil, and particles of the formation, through the casing exteriorly of the tubing, continuously lowering said tubing in the cased drill hole while said fluid mixture is being circulated to increase the extent of said cavity in the formation, at the surface separating air from the fluid-particle mixture, collecting the remaining fluid and particles in a reservoir, and after enlarging the cavity to its greatest extent, completing the operation by displacing the fluids remaining therein with sand pumped from the settling reservoir.

4. A method of producing oil from a formation in which it is held tenaciously to the extent that it will not flow into a well which penetrates the formation that comprises drilling a hole to the upper face of the formation, setting casing therein, placing tubing of a lesser diameter within said casing so that its lower end contacts the formation, circulating air, steam and a cutting oil at an elevated temperature downwardly through said tubing, the temperature and quantity of said fluids being such as to induce separation of oil and sand, to disrupt the formation, producing a continuously expanding cavity therein, to produce a fluid mixture of air, Water from steam condensation, and oil at temperatures of the order of 150- 212 F., in which fluid mixture formation particles may 4be maintained in suspension, and producing a return flow to the surface of the fluid mixture, formation oil, and particles of the formation, through the casing exteriorly of the tubing, continuously lowering said tubing in the cased drill hole while fluid mixture is being circulated to increase the extent of said cavity in the formation, at the surface separating air from the fluid-particle mixture, collecting the remaining fluid and particles in a reservoir, pumping the sand which has settled to the bottom of the reservoir into previously formed Caverns to displace any oil and water contained therein to the reservoir, and pumping the oil Which overlies the Water and sand in the reservoir into storage tanks and processing facilities for further use as cutting oil.

5. A system for producing a highly viscous oil from a formation that is bound together, at least in part, by the highly viscous oil contained therein and which formation has a thick overburden that comprises in combination, a cased drill hole extending from the surface of the earth through the overburden, terminating at the upper face of the formation from which oil is to be produced, a packing gland disposed within the top end of said casing, tubing concentrically disposed within the casing and adapted to make sliding engagement with the packing gland carried by the upper end of said casing, means for lowering and raising said tubing in the drill hole with respect to the casing and packing gland, sources of steam, compressed air, and cutting oil, respectively, means for mixing said compressed air, steam and cutting oil and for introducing the mixture into the tubing to produce a flow of the mixture downwardly therein into the oil containing formation and a return flow in the space between the tubing and casing of the condensed steam, cutting oil, released oil, air and particles of the formation that have been released by the circulation of the cutting oil, and means at the earths surface for conducting a portion of the mixture of cutting oil and released oil to storage or pipe line transportation facilities, and means for processing another portion thereof for use as cutting oil in the continuation of the operation.

6. A system for producing a highly viscous oil from a formation that is bound together, at least in part, by the highly viscous oil contained therein and which formation has a thick overburden that comprises in combination, a cased drill hole extending from the surface of the earth through the overburden, terminating at the upper face of the formation from which oil is to be produced, a packing gland disposed Within the top end of said casing, tubing concentrically disposed Within the casing and adapted to make sliding engagement with the packing gland carried by the upper end of said casing, means for lowering and raising said tubing in the drill hole with respect to the casing and packing gland, sources of steam, compressed air, and cutting oil, respectively, means for mixing said compressed air, steam and cutting oil and for introducing the mixture into the tubing to produce a fioW of the mixture downwardly therein into the oil containing formation and a return flow in the space between the tubing and casing of the condensed steam, cutting oil, released oil, air and particles of the formation that have been released by the circulation of the cutting oil to ultimately form a cavern therein, a reservoir formed on the earths surface, means for conducting the return flow mixture from the casing to the reservoir, means at the reservoir for separating air from the return flow mixture, means for removing the particles of the formation which have settled to the bottom of the reservoir and depositing them in previously formed caverns, and means for removing a portion of the oil from the surface of the reservoir to storage, and, means for reprocessing another portion thereof for use as `cutting oil in the continuation of the operation.

7. A method of producing oil from a sand formation which contains the oil in a manner such that it will not flow of its own volition into a drill hole which penetrates the formation that comprises the steps of introducing, through a well, into the formation a mixture of cutting oil, steam and air at an elevated temperature to cut the oil held in the sand formation and thereby release the oil and particles of sand and disrupt the formation to provide a continuously increasing cavity therein, providing a passageway for the formation oil, cutting oil, water, air and sand particles exteriorly of said introducing means so that the oil, Water, air and sand particles can be carried to the surface.

References Cited in the tile of this patent UNITED STATES PATENTS 47,410 Fraser Apr. 25, 1865 1,439,560 Lee Dec. 19, 1922 1,476,747 Wolever Dec. 11, 1923 2,178,194 Williams Oct. 31, 1939 2,218,533 Huebotter Oct. 22, 1940 2,265,923 Normand Dec. 9, 1941 2,421,528 Steffen June 3, 1947 2,825,408 Watson Mar. 4, 1958 2,881,838 Morse et al. Apr. 14, 1959

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