US2548059A - Rearrangement of oil and gas deposits in sealed domes and like natural formations - Google Patents

Description

April l0, 1951 Patented Apr. 10, 1951 REARRANGEMENT OF OIL AND GAS DEPOS- ITS IN SEALED DOMES AND LIKE NAT- URAL FORMATIONS Ralph H. Ramsey, Ardmore, Okla. Application october s, 1947, serially. 778,586

This invention relates to the re-arrangement of oil Yand gas in sealed natural formations, and has for its object to provide a method for'effecting the natural re-arrangement of' gas, oil and water in such domes, anticlines or similiar formations in which a plurality* of superposed sand strata voccur, separated by impervious earthV structure, each stratum containing gas, oil and water or any two of these uids, so that in the re-arrangement the gas occupies the uppermost, while theol-l occupies the lowermost of'such strata as-*are within the zone affected bythe re-arrangement.

Other objects of the invention will appear as the following description of an illustrative embodiment thereof proceeds.

In the drawing which accompanies and forms a part of the following specification, the sole figure is a diagrammatic sectional viewl in vertical plane through a plunging anticline, illustrating the nature of the stratification to which the method is applicable, and means for carrying out the method.

Referring now in detail. to the drawing, the numerals I`, 2` and' 3 represent strata of pervious sands separated by impervious layers, so that each stratum may be regarded as an independent reservoir. The strata follow the contours of a plunging anticline or dome, each having a pocket of gas 4 in the apex, a body of oil 5 at an intermediate level, and a body of water B, usually salt, at a level below the oil body, sealing the respective sand strata. The lines a-a indicate the interfaces between the gas and oil bodies, and the lines b-b the interfaces between the oil and water.

The several oil bodies actualy consist of ol containing a large proportion of gas held in saturation through the normal high pressure imposed by the gas in the pockets 4 and the surrounding water. If a production well were sunk to tap one of the oil bodies, the pressure in that body would be reduced and some of the dissolved gas would be freed. If the pressure reduction were gradual, this gas would come out of the oil in an orderly fashion and is a major factor in forcing the oil toward the production well. If the pressure reduction were rapid, due to more copious removal of oil from the production well, then the evolution of dissolved gas would be so rapid as to cause foaming in the sands, and foam clogs the interstices in the sand stratum and inhibits flow toward the production well, so that the rate of production would be unduly curtailed on this account.

If, with the oil and gas bodies in their natural arrangement as shown, a production well is sunk 2 lClaims. (Cl. 166-21) to tap all of the oil bodies, the pressure on each becomes at once proportional to their depth below the surface of the ground, so that for a given rate of production, the dissolved gas may come off relatively slowly from the oil in the lowermost stratum, promoting flow in this stratum toward the well, while it may be foaming in the uppermost stratum. Thus optimum production cannot be obtained from all of the strata. If the production well is sunk through .all three strata in the region of the gas pockets, then the gas content from all threewill be depletedbefore there is any oil production, after which the conditions attending the oil production will be the same as those last described. This is a particularly bad method'of production, for the eliminationV of the gas pressure removes one of the factors relied upon for promoting the flow of oil to production wells outside of the bounds of the gas pockets.

The present invention seeks to produce a gravitational re-arrangement of the fluids permeating the several strata, so that substantially all the freegas in the several Vstrata being light, will flow upwardly, and substantially'all the oil will gravitate downward, to the end that the uppermost stratum will contain nothing but gas, and the lowermost stratum nothing but oil (including dissolved gas). By this method the dome may be prepared for re-arrangement and left for years, if desired, before it is tapped for production.l

Referring to the drawings, previous exploration of the field having been made, cased wells 1 are sunk at the peripheries of the oil bodies in the. strata, with perforations 8 communicating with the surrounding water. These wells are closed at the top, the closures being preferably provided with cut-off valves 9 which are normally shut. Thus, the pressure of the sealing water is equalized upon all of the strata.

Another set of cased wells Il) is sunk through all the strata in the reg-ion of the oil bodies therein, having perforations Il communicating with each of the oil bodies. The wells I0 are permanently closed at the top.

Now, all of the sand strata are in communication, and under the same pressure, so that the gas from the lower strata ascends the wells IU into the upper strata, while the oil being heavier, descends the wells ill into the lower strata. In time, the gas pocket 4 at the top strata will have enlarged so as to occupy the entire upper stratum, while the lowermost stratum will contain nothing b-ut oil. Excess gas and oil beyond that which the upper and lower strata can contain, will be found in the intermediate stratum.

In working the re-arranged dome, a gas producing well I2 is sunk, penetrating only the topmost excessively gas containing stratum and an oil producing well I3 is sunk, penetrating through all of the sand strata, but communicating only With the lowermost, that is, the exclusively oil bearingstratum. These wells are provided with the respective cut-off valves I4 and I5 at the top, so that gas and oil can be independently produced and the rate of production of the well I3 so controlled as to maintain the optim-um oil, gas ratio With respect to the evolution of the dissolved gas in the oil.

When, through partial depletion of the oil or gas reserves, it is desired to increase the flow of oil, this can be done, on the one hand by pumping gas into the well I2, or on the other, by Dumping water into the wells 9, in either case increasing pressure n the oil and driving it toward the production well I3. As depletion of gas and oil in the respective top and bottom strata progresses, replenishment takes place gravitationally by the gas in the middle stratum 2, rising through the wells I0 into the top stratum, and the oil in said middle stratum gravitating into the bottom stratum 3.

While I have in the above description disclosed what I believe to be a practical embodiment of the invention, it will be understood by those skilled in the art that such variations in the technique of carrying out the method, and in the means employed as do not depart from the inventive principle, are to be regarded as within the scope of the invention.

What I claim as my invention is:

1. Method of effecting re-arrangement of the oil and gas reservoirs in natural domes and similar formations in which the bearing sands exist in superposed independent strata, gas occupying the higher levels of each and oil the lower levels, with surrounding water sealing said strata at independent pressures, comprising providing closed wells extending through all the strata adjacent the peripheral boundary of the oil body in each,

communicating with the water body in each, whereby the Water pressure becomes equalized in all of said strata, and providing closed wells extending through all of said oil bodies, communicating with each, whereby an interchange of the gas and oil in the several strata takes place, the gas rising in said second mentioned wells while the oil gravitates downward therein, resulting in the top stratum containing substantially solely gas While the bottom stratum contains substantially solely oil.

2. Method of effecting re-arrangement of the oil and gas in reservoirs in natural domes and similar formations in which the bearing sands exist in superposed independent strata, gas occupying the higher levels of each and oil the lower levels, with surrounding Water sealing said strata at independent pressures, comprising providing closed Wells extending through all the strata adjacent the peripheral boundary of the oil body in each, communicatingwith the Water body in each, whereby the water pressure becomes equalized in all of said strata, and providing closed Wells extending through all of said oil bodies, communicating with each, whereby an interchange of the gas and oil in the several strata takes place, the gas rising in said second mentioned wells while the oil gravitates downward therein, resulting in the top stratum containing substantially solely gas while the bottom stratum contains substantially solely oil, and providing a gas injection well tapping solely the top stratum and an oil production well tapping solel said bottom stratum.

RALPH H. RAMSEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,048,731 Doherty J-uly 28, 1936 2,133,730 Brundred Oct. 18, 1938

Images