US2342424A - Treatment of oil productive sands - Google Patents

Description

Patented' Feb. 22, 1944 UNITED STATES 2,342,424 I TREATMENT or on. PRODUCTIVE SANDS No Drawing. Original application June 28, 1938,

Serial No. 216,284. Divided and this application April 11, 1939, Serial No. 267,348

1 Claim.

. This invention relates to the treatment of oil or gas-productive sands in order to increase the flow of oil or gas into the well and is a division of my co-pending application Serial No. 216,284, filed June 28, 1938. The invention particularly relates to a method for increasing'the permeability of producing formations.

In the drilling of oil and gas wells, particularly by rotary tool methods, it is conventional to employ a drilling fluid to aid in the drilling operation. The fluid which is generally an aqueous suspension of solid matter such as clay, bentonite or other solid material 01' even' plain water is pumped down through the drill stem, circulates around the tool or drill bit employed for the .drilling operation and rises between the drill stem and the wall of the hole to the surface of the well. The purpose for the use of the drilling fluid is to carry to the surface of the hole the cuttings made by the drill bit. However, the drilling fluid also serves to lubricate and cool the drill bit and by its weight and pressure prevents the well from blowing in prematurely. Since the prevention of the entrance into the boreholeof the high pressurefluids in the penetrated 'formation, such as oil or gas, is accomplished by the hydrostatic head of the drilling fluid or mud, it is desirable that this fluid should have a maximum density compatible with its other desirable characteristics. For this purpose, it is conventional to add to the. drilling fluid such weighting in the pore spaces of formations containing oil and gas which has the same effect in preventing the flow of oil and gas to the well.

It is an object of our invention to treat oil and gas-producing sands or formations for the purpose of removing obstacles which prevent the flow of oil and gas into the well. A particular object of our invention is to treat the producing sands with a substance which is adapted to reduce the adhesion tension of the water for the sands. Other objects, advantages and features of our invention will be better understood from the following description of our invention.

We have discovered that if the sands are treated with a substance which will dissolve or emulsify the water present in the producing sands and which will lower the surface tension forces holding the water in the sand. such material containing the water in solution will be more readily expelled from the sand into the borehole by the flow of the oil and gas into the well.

the water from the drilling fluid and the connate Thus,

- zones of a material that will dissolve or emulsify materials as barytes;.nematite and finely divided iron.

The existence of a greater pressure due to the hydrostatic head of the drilling fluid in the borehole than that in the formation, however, results ordinarily in the penetration and loss to the formation ,of a quantity of the aqueous portion of the drilling fluid. This loss of water into the oil and gas productive strata seriously impairs the productivity of thewell particularly in low pressure zones since it has a higher adhesive tension than oil for the sand in the productive zone and therefore the water will displace the oil film from the sand grains and capillaries. In other words, the sand has a greater attraction for the water than for the oil, resulting in adsorption of water on the surface of the sand thereby reducing the porosity or permeability of the sand surrounding the borehole. Consequently, water that finds its way into and is present in a sand formation will remain in the finer capillary spaces within the structure interfering greatly with thesubsequent production of oil from the well. Furthermore, connate water is also present frequently water that may be pres nt in the sand and that will be subsequently readil driven from the sand into the welt by the 'production of oil-and gas.

' The materials which are capable of accomplishing the desired result are either of the type that dissolve water but would not be-dissolved in oil or of the type capable of being soluble in both oil and water, or of the type that will cause the Water to form an emulsion with the oil. We have found the following materials suitable for such purpose:

Materials which have mutual solubility for water and oil such as the alcohols, ethyl, methyl, normal and isopropyl; the ethers, such as ethyl ether and its water soluble homologues; ketones such as acetone, ethyl, methyl and di-ethyl ketone and their Water soluble homologues; and mixtures of alcohols and ethers and/or ketones;

phenols such as phenol and cresol surface active agents such as esters of sulfonated dicarboxylic acids and water-soluble salts thereof; sulfonated alcohols and sodium and potassium and other water-soluble salts thereof, sulfonated fatty esters and acids and water-soluble salts thereof; sulfonated mineral oil and water-soluble salts thereof and soluble salts of alkyl sulphates. An example of an effective surface active agent of the alkyl sulfate type is sodium lauryl sulfate and examples of the sulfonated fatty acid type by even flowing it down the well by gravity to the oil sands. The quantity of liquid to be employed for the operation will, of course, vary with each well, this depending primarily on the diameter of the hole at the bottom of the well and on the thickness of oil-producing sands. In general, however, a sufiicient amount of the liquid is in-' troduced into the well so thata column of liquid of sufficient height is maintained in the well to force the liquid about four or five feet into the formation by hydrostatic pressure. In' one particular well having an oil-producing formation of about 100 feet thick, approximately 2000 gallons of ethyl alcohol were introduced into the well which was allowed to flow by gravity down' the well to the oil sands. The alcohol was allowed to remain at the bottom of the well for approximately 12 hours in order to combine with the connate water present in the formation after which the liquid in the well consisting of a mixture of oil, alcohol and water was pumped out of the well. The treatment resulted in an increased production.

Another desirable method for effecting the penetration of the adhesion'tension reducing material into the above mentioned formation the required distance is to pour the required amount of the material down the well and then place the material under a superimposed pressure for a sufficient period of time to cause the material to penetrate into the formation and dissolve the water contained in it. The necessary pressure to force the material into the formation may be supplied by forcing a gas, such as airor a fixed hydrocarbon, into the well until a sufficient pressure is provided therein. After the material has been maintained under the superimposed 'gas pressure for a suflicient period of time, say -12 to 24 hours, the pressure is released to atmos pheric and the liquids in the well are pumped out. If desired, the application of gas pressure on the formation may be carried-out inter'm'iltently, that is, the material introduced into the well may be maintained under pressure for a shorter period of time, say for one hour. and then.

the pressure is released for a short period of time to allow the material and dissolved or emulsified water to flow back intothe well. The pressure is then reapplied tothe formation for another period of time and then again released. This alternate imposition and release of pressure may De repeated a number of times until the operator considers that-the formation has been treated sufficiently to remove substantially all of the ,water present in the producing sands for a distance of four or five feet from the borehole.

In some cases, it may be necessary to repeat the above operation using fresh liquid in order to obtain the desired result as the liquid employed in the previous operation may have become contaminated with considerable connate water and other substances before it has penetrated a sufficient distance in the oil- =producing sands to relieve the capillaries of the sands "sufliciently of connate and other water to permit the oil to flow freely into the well.

While the application of our invention is particularly suited to low producing wells in low pressure formations which have been in operation for a considerable period of time, the invention is equally adapted to the treatment of new wells; In the treatment of such wells, however,

it is preferable after the well has come into pro duction to allow the well to produce until the oil production is reduced materially before the treatment to remove connate and other water is made.

The-above description of our invention is not to be considered as limiting 'since many variations may be made by those skilled in the art within the scope of the following claim without departing from the spirit of the invention.

We claim: i i

A method of increasing the production of an oilor gas well comprising introducing an ester of a sulfonated dicarboxylic acid into the well.

forcing said esterof a sulfonated dicarboxylic.

acid into the interstices of the producing forma- -'tion to contact the dissolved water adsorbed therein and withdrawing said ester-of dicarboxylic acid together with the-dissolved water" from'said formation and directly thereafter producing said well.

' VJILLIAM M. NEWTON.

PHILIP H.JONES.