US2749991A - Oil production method - Google Patents

Description

JunelZ, 1956 R. sPEARow on. PRODUCTION METHQD Filed June 12, 1952 INVENToR. Fa/7 pea/"0W BY nr @RNEK United States Patent() OIL PRODUCTION METHOD Ralph Spearow, Paola, Kans. i Application June 12, 1952, Serial No. 293,056

1 Claim. (Cl. 166''4Z) This invention relates to methods for producing oil from oil sands and more particularly to methods for producing only oil from sands which normally produce oil contaminated with water.

Many producing oil formations including those requiring repressurizing of some sort often present the problem of water being produced with the oil. This problem is especially serious and aggravated when the repressurizing and oil recovery is by water drive where extra 'water is pumped into the oil sand. Further, when the water drive method has been used and the maximum recovery achieved thereby, there still remains a large quantity of oil in the sand together with the added Water which by present methods must be recovered together and separation made at the surface. ln all s'uch cases, lthe primary problem is to handle and dispose of the large quantities of water which are produced with the oil. Another problem requiring much surface equipment is the separation of simultaneously produced oil and water which is in emulsifled form.

Therefore, the primary object of the instant invention is to provide a method which will produce only oil from oil sands which normally would produce both oil and water.

A further object is to provide a method by which the oil is separated from the water under ground and the water is retained in the sand to aid in maintaining the bottom hole pressure.

Still another object is to provide a method which produces uncontaminated oil from sand normally producing both oil and water thus avoiding the expense and trouble of separating equipment.

Other and further objects of this invention will appear in the following description.

In the accompanying drawing, which forms a part of the instant specification and is to be read in conjunction therewith, there is shown an embodiment of the invention.

The single figure is a sectional view of an oil well wherein the necessary casing and tubing for practicing the invention have been set.

In the drawing, the numeral indicates a primary outer casing positioned in the hole bore 11 of an oil well and extending from the ground level 12 to the vicinity of the top 13 of an oil sand 14. It should be understood that the casing may as well extend into or through the formation with perforations to permit ingress and egress of the formation fluids therethrough. The hole bore 11 is shown in dotted lines extending through the oil sand 14 and at 15, in full lines, is shown the probable outline of a bottom hole cavern produced by shooting the well without the extension of the casing through the oil sand. The casing 10 is cemented to the surrounding formations through which it passes as shown at 16. Although the casing in the drawing terminates at the top of the producing sand, it is contemplated that it may be desirable to extend the lower end of the casing into the producing formation as hereinafter explained. A secondary tubing 17 is positioned within the casing ICE and may extend below the lower end of the casing into the oil sand 14. A discharge valve18 in the tubing above ground level controls the flow of iluid through the tubing. A check valve 19'1ocated in the lower end of tubing 17 has ball valve 20 which seats downwardly. The casing head 21 furnishes apressure-tight connection 22 between the tubing 17 and the casing 10. Casing 10 is equipped with an inlet connection 23 controlled by valve 24 and an outlet connection 25 controlled by valve 26.

In operation, it is assumed that some pressure, natural or artificial, exists on the oil sand thus bringing fluid into the hole bore 1l or shot hole 15 where it tends to rise in the casing and tubing. To institute the method, valve 26 in the casing and valve 18 in the tubing are opened, thus permitting the fluid from the oil sand to rise both in the casing and tubing to a level according to the pressure existing in the sand. If the bottom hole pressure is great enough, the yfluid may rise all the way to the valves 18 and 26, at which time they would be closed. However, in the drawing only such pressure is assumed as will raise the fluid in the casi-ng and tubing to the level designated by dotted line A and this level is the top of the oil portion of the uid column which enters the casing and tubing. Dotted line B designates the interface between the water and oil portions of the column which rises in the casing and tubing. At this time, the oil and water have no particular tendency toward emulsication but separate naturally according to their respective specific gravities, the well fluid not having been subjected to any mixing turbulence. When the fluid has risen to a level such as is indicated at A in the casing and tubing, the valve 26 and the valve 18 are closed. Inlet valve 24 is then opened and pressure is applied through connection 23 to the top of the fluid column in the casing. Sulllcient pressure is imposed to force the fluid column downwardly until the base of the oil portion of the column or interface B is lowered to a position below the check valve 19 designated as D. Level C then indicates the probable position of the top of the oil portion of the column. With the above-mentioned pressure continuously applied, valve 18 in the tubing is then opened. The water and oil contained originally in the tubing are rst drained off and then all the available oil included between levels C and D is likewise withdrawn, As the oil between levels C and D is removed, the water level D will rise and it is desirable to terminate the llow of fluid from the tubing before level D rises to the check valve. When substantially all the available oil between these levels has been drained olf through tubing 17, valve 18 and valve 24 are closed. Outlet valve 26 is then opened to release the pressure imposed on the fluid column in the casing thereby permitting the fluid to accumulate again in the casing. As previously suggested, by extending the casing into the producing sand the area of interface levels B and D are restricted within the contines of the casing, thus effectively reducing the area of pressure application, since otherwise the interface level must be lowered in the entire producing formation.

Repeated cycles of the foregoing operations will reveal the necessary pressure and the time period of application of pressure to the fluid column in the casing to correctly displace the oil portion of the column to its proper position in relation to check valve 20. Likewise, the time period during which oil is withdrawn from the tubing is determined. A repetitive cycle of the foregoing operations thereafter is conducted as a continuous process thereby withdrawing measured amounts of oil unmixed with water from the sand.

A method is thus provided which produces only oil from an oil sand which normally would produce both water and oil.

A method has also been provided by which the oil is separated from the water under ground and the water is retained in the sand to aid in maintaining the bottom hole pressure.

Furthermore, a method has been provided which produces uncontaminated oil from a sand normally producing both oil and water-thus avoiding the expense and trouble of separating equipment.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claim.

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 accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

A process for the production of oil from a well producing water-contaminated fluid, said well having a casing cemented to the surrounding formations, a pressuretight casing head and a tubing extending through the casing head and within the casing into the producing horizon with a check valve at the lower extremity of the tubing comprising the steps of opening the casing and tubing at the surface to cause the fluid to rise in the casing and tubing under the influence of the rock pressure in the producing formation and form a column in the casing rising to'a height commensurate with the rock pressure, maintaining said column for a period suicient to permit gravitational separation of the water and oil therein, then sealing the casing and tubing at the surface and imposing pressure 0n the column in the casing sufcient to drive the water back into the formation and lower the interface between the oil and water to a position below the check valve in the tubing, unsealing the tubing at the surface to flow oil from the tubing and maintaining the tubing unsealed until the interface rises almost level with the lower end of the tubing, then sealing the tubing and removing the applied pressure on the column in the casing for a period to cause fluid from the formation to rise in the casing and again form a column of water and oil rising to a height commensurate with the rock pressure, again maintaining the column for a period sufficient to cause separation of the oil and water, and repeating in order and at successive intervals the application of pressure, flowing of oil from the tubing and release of pressure in the casing thereby to establish a cyclic production operation.

References Cited in the le of this patent UNITED STATES PATENTS 1,499,509 Dunn n July 1, 1924 1,499,589 Navin July 1, 1924 1,885,807 Doherty Nov. 1, 1932 2,258,614 Kendrick Oct. 14, 1941 OTHER REFERENCES The Oil Weekly, October 12, 1936, pp. 39, 40, and 42.

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