US2725106A

US2725106A - Oil production

Info

Publication number: US2725106A
Application number: US262568A
Authority: US
Inventors: Spearow Ralph
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-12-20
Filing date: 1951-12-20
Publication date: 1955-11-29
Anticipated expiration: 1972-11-29

Description

Nov. 29, 1955 R, SPEARQW 2,725,106

OIL PRODUCTION Filed Deo. 20, 1951 2 Sheets-Sheet l .v A ,fr l I I i l TTORNEK Nov. 29, 1955 sPl-:ARow 2,725,106

OIL PRODUCTION 2 Sheets-Sheet 2 n .v0.7 0. 7/ V 0,. l N r ZZM N .f w

' INVENTOR.

United Statesl Patent O OIL PRODUCTION Ralph Spearow, Paola, Kans.

Application December 20, 1951, Serial No. 262,568

4 Claims. (Cl. 166-9) This invention relates to improvements in the process for producing oil from oil sands and refers more particularly to a process which may be utilized either as a primary oil production method or a secondary oil production method whereby oil is produced fromr an oil producing horizon or reservoir after conventional production methods or processes have become uneconomical.

This application is a continuation in part of a prior application Serial No. 750,396 filed May 26, 1947, now Patent No. 2,593,497 issued April 22, 1952. i

In many of the numerous oil producing areas all over the world there are fields where production is no longer commercially feasible due to the fact that the original pressure in the oil stratum has been exhausted to the extent that the fluid oil will no longer movethrough the sand into the wells in sufficient quantities to permit profitable operation. The mere fact thatthese fields are no longer commercially profitable does not mean that the oil supply has been depleted, for core samples taken from many of these fields after abandonment reveal that more oil remains than was removed.

Attempts have been made to improve the initial oil production methods and numerous secondary recovery methods have been devised to produce oil left in abandoned fields with varying degrees of success. No secondary method yet discovered has been successful in eliminating two principal objections: First is the fact that the method does not exceed substantially the efficiency of the original or primary production method, so there is still left in the reservoir too large a percentage of oil; second, cost of operating the secondary method seldom justies the oil recovered.

The instant process diifers from what has preceded in that pressure is applied to the top of the reservoir to cause the fluid in the sand to migrate downwardly as a body and recovery of the oil from the reservoir is from its lower regions at or near the bottom.

Fig. 1 is a cross-sectional View taken through the geologic structure of an oil field showing two wells each of which is both a pressure and production well.

Fig. 2 is a cross-sectional view taken through the geologic structure of an oil field showing three wells, one of which is a pressure well, the other two being production wells.

Referring to Fig. 2, at is indicated the overlying geologic structure with an impervious layer 11 above the oil sand 12. The structure below the oil sand is indicated at 13. The pressure well is drilled from the surface through the impervious layer 11 into the top of the oil sand, and a casing 14 is run into the Well and is cemented as shown at 15. The pressure well casing is capped by means of a iianged fitting 16, and connected into the top of the casing is a pipe 17. Pressure gauge A18 in the top of the casing indicates pressure on the casing at that point.

The production well or wells are drilled through the oil sand and casings are run as shown at 19. The pro-l duction well casings are cemented as is the pressure well ICC as indicated at 15. After the casings in the production wells have been cemented, both the casing and annular cement columns are shot with perforations 20,1ocatcd at or near the bottom of the sand 12. The production casings are capped to make them pressure tight and within the casing is a tubing 21. Oil may be produced, either by natural flow through the casing 19 or by pumping through tubing 21. Pump rods are indicatedl dia grammatically at 22, the pump being encased in' the tubing at the bottom of the well and mechanism for reciprocating the pump rod at the surface not shown. Discharge pipes 23 controlled by valves 24 are tapped into the casings 19 above ground level for removing the oil produced by flowing and discharge pipes 24 controlled by suitable valves 25 are connected into the tubing 21 to withdraw oil pumped from the sand through the tubing. n

The location of the pressure and production wells in the field will depend upon the size and shape of the oil reservoir and to a great extent will be governed by the engineer or person in charge of producing the oil. In so far as the process is concerned, it is essential only to drill the pressure wells into the top of the oil sand in locations where the air or gas charged to the oil sand will be distributed over the entire area of the field imposing a relatively constant and uniform pressure upon the sand being produced. The number of pressure wells necessary will to a great extent depend upon the size of the field and the rapidity at which the field is to be produced. It is especially important that the impervious layer 11 above the sand is tightly sealed by the cement columns to the well casings of both the pressure and production wells in order to reduce loss of pressure in so far as possible.

The location of the production wells likewise is a matter of judgment with the producer and the geologists in charge of the operations, since they should be located advantageouslyr to withdraw the oil from the bottom of the sand as it moves downwardly due to pressure applied on top of the sand by the pressure wells. The number of production wells necessary will to a great extent depend upon the size and shape of the field. The necessity for pumping the wells will of course be determined by whether the pressure imposed is sufhcient to ow l the wells without resorting to mechanical means to raise the oil to the surface.

Pressure may be imposed in the form of gas if available or by air and should be supplied into the pressure wells through pipe 17. The amount of pressure required will be determined by the necessity of supplementing gas pressure already in the sand to drive the oil downwardly through the sand to the production wells. In depleted oil sands Where little or no pressure exists, sufficient pressure must be supplied to force the oil into the production wells where it is accumulated and pumped to the surface where suflicient pressure is applied and the sand is at a shallow depth below the surface the wells may again flow naturally.

In Fig. l is shown a modification of the method illustrated in Fig. 2. In this figure like numerals are used to refer to like parts of Fig. 2. However, in this modification a packer 26 is employed to seal off the space between casing 19 and tubing 21 intermediate the top and bottom of sand 12. The casing 19 and cement column 15 are also shot above the packer 26 at 20a. Pipe 23a controlled by valve 24a is employed as an air pressure input into the space between casing 19 and tubing 21.

In an actual operation in eastern Kansas where a small shallow field had been abandoned for ten years or more, most of the old wells were plugged and nine new wells drilled through the producing sand. The old wells which were not plugged were cleaned and the casing cemented in the manner described in Fig. l. An inner casing and packer were set in each of the old wells according to the procedure described and shown in Fig. 1. The old wells and the new wells were cemented to seal olf the oil sand from the overlying geologic structure and provided a seal between the casings and the impervious layer above the producing sand.

After the wells had been completed, air pressure was applied to the old wells in which the packers had been placed by eight motor driven compressors. The pressure at the well heads of the pressure wells was 500 pounds per square inch and pressures ranging from 250 to 300 pounds at the well heads of the adjoining producing wells. During the initial stages of operation, the old wells began, within ka matter of hours after pressure was built up, to produce water which had accumulated over a period of years in these wells due to the fact that the field was along a river bottom which was under Water periodically and for short periods almost every year. The new wells drilled in the field never produced anything but oil.

From the available records, none of the Wells in this field had ever produced more than nine to ten barrels a day. The two old wells which were renovated and operated according to the procedure described in connection with Fig. l are currently being produced at the rate of 200 barrels for a 24-hour day. Some of the more remote wells from the pressure input location are being produced at the rate of from 50 to 75 barrels per day.

All of the wells which were drilled under the instant program of rehabilitation besides being carefully cemented, were perforated near the bottom of the sand and and the pressure wells perforated both at the bottom of the sand and at the top of the sand above the packer as indicated in Fig. 1 of the drawing.

It is recognized that in secondary production methods air, gas or water have been used to force the oil laterally through the sand from a location where the air, gas or water pressure is applied to the sand; but difficulties are encountered with these operations because it is almost impossible to force the oil laterally or horizontally through the sand. Attempts have also been made to bore ducts laterally into the producing sand from a pressure Well at different levels and introduce gas or air from the surface to cause the oil to migrate away from the pressure well into production wells. The objection to this type of operation is the difficulty encountered in drilling the lateral ducts into the oil sand for any distance or to so distribute the ducts in the field to render them effective for the purpose intended.

The instant method supplies the pressure medium, either air or gas, at the top of the sand where the sand is most porous and contains the least amount of uid oil so the gas or air supplied under pressure moves more freely and spreads laterally through the top of the sand building up a pressure space in the upper regions of the sand. Pressure applied in this manner causes a uniform migration of the fluid oil downwardly through the sand causing it to accumulate in the lower regions of the sand from which it may be Withdrawn more eiiicaciously through the producing wells. By this process the creation of gas or air pockets and the difliculties of channeling of the air and gas through the less impervious or porous regions of the sand is to a great extent eliminated.

From the foregoing it will be seen that the invention is well adapted to attain all lof the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the method and apparatus. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcornbinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. A method of producing oil from an oil reservoir by a gaseous pressure medium supplied from the ground level to said reservoir, comprising the steps of drilling a pressure input well to the top of the reservoir, running a casing in said input well, sealing said casing to the surrounding formation from the top of the reservoir to a level above said reservoir, drilling a production well to the vicinity of the bottom of said reservoir, running a casing in said production well to the bottom thereof, sealing said last mentioned casing to the surrounding formation from the vicinity of the bottom of said casing to a level above the top of the reservoir, applying a gaseous medium under pressure through said input Well onto the top of the oil reservoir, said input well casing seal being of such strength as to confine such pressures as may be applied to the top of the reservoir, and said production well casing seal being of such strength as to prevent vertical leakage of the pressure medium along the surface of contact of the sealing material and the surrounding formation whereby a vertical pressure is imposed and maintained in the reservoir to produce oil from the production well.

2. A method in claim l including the step of perforating the casing adjacent the bottom of the reservoir.

3. A method as in claim 1 wherein a plurality of production wells are used with a single input Well.

4. A method as in claim l wherein a plurality of production Wells are used with a plurality of input wells.

References Cited in the le of this patent UNITED STATES PATENTS 1,252,557 Dunn Jan. 8, 1918 l,722,679 Ranney July 30, 1929 .l,8ll,561 Ranney June 23, 1931 1,816,260 Lee July 28, 1831 2,188,737 Hixon Ian. 30, 1940 2,297,832 Hudson Oct. 6, 1942

Claims

1. A METHOD OF PRODUCING OIL FROM RESERVOIR BY A GASEOUS PRESSURE MEDIUM SUPPLIED FROM THE GROUND LEVEL TO SAID RESERVOIR, COMPRISING THE STEPS OF DRILLING A PRESSURE INPUT WELL TO THE TOP OF THE RESERVOIR, RUNNING A CASING IN SAID INPUT WELL, SEALING SAID CASING TO THE SURROUNDING FORMATION FROM THE TOP OF THE RESERVOIR TO A LEVEL ABOVE SAID RESERVOIR, DRILLING A PRODUCTIUON WELL TO THE VICINITY OF THE BOTTOM OF SAID RESERVOIR, RUNNING A CASING IN SAID PRODUCTION WELL TO THE BOTTOM THEREOF, SEALING SAID LAST MENTIONED CASING TO THE SURROUNDING FORMATION FROM THE VICINITY OF THE BOTTOM OF SAID CASING TO A LEVEL ABOVE THE TOP OF THE RESERVOIR, APPLYING A GASEOUS MEDIUM UNDER PRESSURE THROUGH SAID INPUT WELL ONTO THE TOP OF THE OIL RESERVOIR, SAID INPUT WELL CASING SEAL BEING OF SUCH STRENGTH AS TO CONFINE SUCH PRESSURES AS MAY BE APPLIED TO THE TOP OF THE RESERVOIR, AND SAID PRODUCTION WELL CASING SEAL BEING OF SUCH STRENGTH AS TO PREVENT VERTICAL LEAKAGE OF THE PRESSURE MEDIUM AND THE THE SURFACE OF CONTACT OF THE SEALING MATERIAL AND THE SURROUNDING FORMATION WHEREBY A VERTICAL PRESURE IS IMPOSED AND MAINTAINED IN THE RESERVOIR TO PRODUCE OIL FROM THE PRODUCTION WELL.