US3490530A - Initiating in situ combustion using an autoignitible composition - Google Patents

Description

United States Patent O US. Cl. 166-260 8 Claims ABSTRACT OF THE DISCLOSURE A mixture of tung oil and tall oil fatty acid is used for initiating in situ combustion in oil stratum containing water and having a low initial temperature.

This invention relates to a process for initiating in situ combustion in oil stratum. In one aspect this invention relates to a process for initiating in situ combustion in oil stratum containing water at low initial temperatures. In another aspect this invention relates to a process wherein a mixture of tung oil and tall oil fatty acid is used for initiating in situ combustion in oil stratum containing water and having a low initial temperature.

There has been much work done in the past few years involving in situ combustion in oil stratum to increase the oil and oil products produced from the stratum. One area of work has been with autoignitible fluids. General y the autoignitible fluid is injected into the oil stratum and then the autoignitible fluid in the stratum is contacted with air or other oxgen-containing, combustion supporting gases. When the air or other oxygen-containing, combustion supporting gas comes in contact with the autoignitible fluid, the temperature in the formation is in creased to at least the combustion temperature of the car bonaceous material (such as oil, oil residue, tar, etc.) in the stratum. This incerase in temperature is due to the oxidation reaction of the autoignitible fluid when it contacts the air or other oxygen-containing, combustion supporting gas. The use of tung oil, linseed oil or other known autoignition fluids has worked well for oil wells where the initial temperature is high, for example 140 F. or above. There has, however, been a problem in achieving the combustion temperature for the carbonaceous material when the initial temperature in the formation is low, for example 140 F. or below. This has been especially true in the formations which have low initial temperatures and contain water. When the. initial temperature is low, the autoignitible fluids such as linseed and tung oil increase in temperature slowly when contacted with air or other oxygen-containing, combustion-supporting gas. This slow increase toward the combustion temperature of the carbonaceous material may result in failure to reach that temperature. This is due to the fact that the heat from the reaction can be dissipated into the surrounding stratum if the temperature rise is slow.

I have discovered that the above problem of heat dissipation can be overcome by using as an autoignitible fluid a combination of tung oil and tall oil fatty acid. The temperature of the tung oil-tall oil fatty acid mixture will rise rapidly when air or other oxygen-containing, combustion-supporting gas is contacted with the mixture in the stratum. This fast rise in temperature eliminates the possibility that the heat may be dissipated in the stratum before the combustion temperature of the carbonaceous material is reached.

Accordingly, it is the object of the present invention to provide an improved process for igniting oil in an oil stratum wherein the stratum contains water and has a low initial temperature. A further object is to provide l 3,490,530 Patented Jan. 20, 1970 an improved process for igniting oil in an oil stratum wherein the stratum contains water and has a low initial temperature by utilizing a mixture of tung oil and tall oil fatty acid as an autoignitible fluid. Other objects, aspects and advantages of the invention will be apparent from a study of the disclosure and the appended claims of the invention.

A broad aspect of the invention comprises dispersing a mixture of tung oil and tall oil fatty acid in a stratum containing carbonaceous material and water and thereafter injecting an O -containing oxidizing gas into the stratum and into contact with the mixture so as to increase the temperature of the stratum and the in place carbonaceous material rapidly to a point at or above the combustion point of the carbonaceous material. The tung oil makes up beween 70 to weight percent of the total mixture and the tall oil fatty acid between 10 to 30 weight percent of the total mixture.

A normal procedure for placing the mixture of tung oil and tall oil fatty acid into an oil stratum is as follows: the mixture of tung oil and tall oil fatty acid is physically mixed in tanks on the surface. After the fuel is mixed, a slug is sent down the oil well. It has been found that incorporation of an oxidation catalyst in minor concentration in the mixture facilitates spontaneous ignition of the mixture and makes it feasible to ignite the mixture with ordinary air at atmospheric pressure. It is preferred to utilize the catalyst in liquid form so as to avoid plugging the stratum. A preferred catalyst is cobalt naphthenate, which is readily soluble in the tung oiltall oil fatty acid mixture. Other catalysts include oil soluble salts and other compounds of the metals listed as oxidation catalysts in Berkman et al., Catalysis, Reinhold Publishing Corporation, 330 W. 42nd St., New York, N.Y., 1940, pages 797-809. Next a nonoxidizing gas such as nitrogen or exhaust gas (nitrogen and C 2) is pumped into the well to disperse the mixture in the stratum. The mixture will generally be dispersed out for a distance between about 1 and 10 feet from the well hole in the surrounding stratum.

After the mixture is dispersed into the stratum then an oxidizing gas such as air or other Op-containing, combustion-supporting gases is injected into contact with the mixture. There will be a rapid increase in the temperature of the mixture when contacted with the air or other oxygen-containing, combustion-supporting gases. This is true even when the initial temperature in the stratum is below F. (such as 80 F.). Also, there will be autoignition of the carbonaceous material even when there is water present in the stratum in percentages up to about 3 weight percent water with particularly good results in stratum containing up to about 2.5 weight percent water. The temperature will continue to rise in the stratum until the combustion temperature of the carbonaceous material in the stratum is reached. After the combustion temperature of the carbonaceous material is reached, injection of the oxidizing gas is continued to ignite and burn the carbonaceous material in place in the stratum.

Tests were run to demonstrate the facility with which the mixture of tung oil and tall oil fatty acid reached the combustion temperature for oil. In all the tests the initial temperature was 80 F. and the time required to reach 250 F. was measured. The temperature of 250 F. was used because it was known that all autoignition fuels which reached 250 F. will rapidly move on up to the combustion point of oil at about the same rate. In other words, once the autoignition fuels reached 250 F., then they all went from 250 F. to the combustion point of oil in approximately the same amount of time. Also, since the temperature of combustion for oil is differentfor different oils and formations, the use of 250 F. made the data easier to compare.

The procedure used for the first six tests was as follows: The autoignition fuel was mixed with a 30-40 mesh silica sand Wetted with 2.5 weight percent water. This mixture of fuel, water and sand was packed into a nearadiabatic (heated wall) glass cylinder which was in turn installed in a steel pressure jacket. Air at a pressure of 900 p.s.i. was put through the pack at controlled rates which started out at 50 s.c.f. hour/ square foot and 80 F. The autoignitible fuels contained 0.2 weight percent cobalt as cobalt naphthenate as oxidation catalyst. The procedure used for the last five tests was the same as for the first six tests except that no water was added to the sand in the last five tests. All other conditions were the same. The initial temperature for all tests, as stated above, was 80 F. The followmg results were tabulated:

Water Time to in Sand Reach (Weight 250 F. Run Autoignition Fuel percent) (Minutes) 1 100 Tun Oil 2.5 115 2 t 2. 100 3 90% Tung Oil, Tall Oil Fatty ci 2. 5 75 4 70% Tung Oil, 30% Tall Oil Fatty Acid 2. 5 70 5 d0 2. 5 65 6 100% Tall Oil Fatty Acid--. 2. 5 7 100% Tung Oil 0 73 8 70% Tung Oil, 30% Tall O11 Fatty 1 Did not reach 250 F.

As shown by the above results, with the tung oil and tall oil fatty acid mixture there was a substantial decrease in the amount of time that was required to reach the 250 F. point. This decrease in the time at which 250 F. was reached assures that a system will reach the combustion temperature of the oil and that the heat will not be dissipated faster than the temperature can rise. It is also shown that the oil can be ignited from low initial temperatures even in the presence of water. This will eliminate the requirement that the water be evacuated from the stratum before the in place burning takes place.

We claim:

1. A process for injecting and burning carbonaceous material in an oil stratum, said stratum containing amounts of water up to 3 percent by weight, which comprises the steps of:

(1) injecting into said stratum a mixture comprising tung oil and tall oil fatty acid where in said mixture said tung oil is from about to percent by weight of the total mixture and said tall oil fatty acid is from about 10 to 30 percent by weight of the total mixture; and

(2) subsequent to step (1), injecting an oxidant providing suflicient 0 concentration to cause autoignition of said mixture into said stratum into contact with said mixture.

2. A process in accordance with claim 1 comprising, in addition, a step subsequent to step 1) but prior to step (2) of injecting a nonoxidizing fluid into said stratum to force said mixture into said stratum.

3. A process in accordance with claim 1 comprising, in addition, a step subsequent to step (2) of continuing injection of said oxidant at a rate to ignite and burn the in place carbonaceous material.

4. A process in accordance with claim 1 wherein an oxidation catalyst is added to said mixture in step (1).

5. A process in accordance with claim 4 wherein said oxidation catalyst is cobalt naphthenate.

6. A process in accordance With claim 1 wherein said stratum contains amounts of water up to 2.5 percent by weight.

7. A process in accordance with claim 1 wherein the initial temperature of said stratum and said mixture is less than F.

8. A process in accordance with claim 7 wherein the initial temperature of said stratum and said mixture is about 80 F.

References Cited UNITED STATES PATENTS 2,863,510 12/1958 Tadema et a1. 166260 3,026,937 3/1962 Simm 16626O 3,180,412 4/1965 Bednarski 166-260 3,205,944 9/1965 Walton 166-26l 3,209,822 10/1965 Marberry 166'256 3,221,809 12/1965 Walton 166263 3,285,336 11/1966 Gardner 166261 3,314,476 4/1967 Staples et a1 166260 3,363,687 1/1968 Dean 16626O X 3,379,254 4/1968 Holmes 166260 STEPHEN J. NOVOSAD, Primary Examiner U.S. Cl. X.R. 166-261