US2386036A - Method for secondary recovery of oil - Google Patents

Description

Oct. 2, 1945.

R. CROSS METHOD FOR SECONDARY RECOVERY OF OIL 2 Shee'ts-Sheet 1 Filed Sept. 6, 1943 INVENTOR.

Patented Oct 2, 1945' METHOD FOR SECONDARY RECOVERY OF OIL Roy Cross, Kansas City, Mo.

Application September 6, 1943, Serial No. 501,409 p 1 Claim. (01. 166-21) This invention relates to.a method of increasing the amount of oilrecovered from oil wells.-

It applies more particularly to wells which protest.

One of the objects of the invention is to provide a new and improved cyclic system of adding a fluxing agent to oil wells to reduce the viscosity of the oil therein, the fiuxing agent being a light petroleum oil of the same general character as the oil in the formation of the well and acting as a solvent for said oil.

Another object is to provide a new and improved method of heating the oil in the formation to reduce the viscosity and increase the rates of flow in the interstices of the mineral particles duce oil that'has a high viscosity or high cold allowed to vaporize by its own self-contained heat so that from to 50% passes into the vapor state depending upon the specific method of operation. The vapors from this flash distillation are introduced into the well at the level of the formation bearing the oil. The rock pressure in this particular lease is 250 pounds per square inch. Sufllcient pressure is carried against this formation so that the desired amount of vapors will enter the formation. Ordinarily this is over 250 pounds per square inch, although it varies in different wells. The temperature of the entering vapor will vary ordinarily from 250 F. up to of the formation in such manner that as little heat as possible is dissipated into the non-oil bearing formations adjacent to the oil bearing formations. Y

Another primary object of theinvention is to increase the rate of flow from the region of the well wherethe treating takes place to the region of the well from whichthe oil is lifted."

As an illustration of the application of this invention, I refer to oil produced in Allen County,

Kansas. There is a vast quantity of this oil,in

- many cases amounting to 30,000 or more barrels per acre. By the ordinary method of extraction with wells approximately 400 feet apart, the total amount of oil taken out in a period of years 750 F. When it is desirable that the residue or fuel oil have a low viscosity, then the temperature of the vapors is decreased but if an asphaltic residue is desired, then the temperature of the vapors is increased. These vapors enter the oil formation most easily at the point where there is has been about 1%, or 300 barrels per acre. By

the method of this invention the amount taken out, depending upon circumstances, will vary from 10% to 50%, or from 3000 .to 15,000 barrels per acre. This particular oil has a specific gravity of 0.939 or A. P. I. gravity. of 192, a viscosity of 956 Saybolt Universal. cold test of ---10 F., a color of over 15,000, a flash point of 265 F., residue and water of 1% and contains no natural gasoline or naphtha. .By cracking, it will yield well over 60% of gasoline, however, so the oil is basically of considerable value and it contains a small amount of sulphur. The oil is excellent stock for lubricating oil and it is practically free from wax. In other words, it has practically the,

same value as light crude.

oil which has an aflinity for the oil vapors, thus the heat is selectively introduced into the oil in the formation, rather than being wasted in the heating up of the adjacent sand or rock and water. The input well or well into which the vapor is introduced is centrally located in respect to other wells. "Normally there will be eight wells immediately surrounding the input well,

in some cases 24 or more wells. There should preferably be not less than 4 wells or preferably not more than 24 wells surrounding each input well, although if the formations are very porous the oil may. be forced to migrate by reason of its lower viscosity to considerable distances.

7 With this lowered viscosity, the oil will prefer- In this invention, the method may be illustrated by one particular lease where there is a daily production of 100 to 200 barrels of the heavy oil, each well producing about two barrels per day. In thiscase, this crude oil is subjected to an incipient cracking temperature of approxi- ,mately 800 F. in a continuous tube still. moment the oil attains this temperature it is The entially flow into the adjacent well from which the oil ispumped in the usual manner. Or, if any particular well shows a high temperature in relation to the others, then this well is not pumped out so frequently. A varying head can be maintained on each well to equalize the flow from the input well to the various wells. One set-up for the operation will usually take care of production from 16 to 64 acres. After the viscosity of the-oil produced from all of the surrounding wells has been considerably lowered or the temperature substantially increased, then the operation can be moved to a new point in the field. Air, either cold or heated, may now be introduced into the input well to displace a large amount of the residual oil of lower viscosity and increase production by the usual compression methods.

The method and apparatus for secondary'reases of combustion into the formation of the In general, the operation involves the introduc-' tion of compressed air through the line IIO to maintain the pressure of the air in the combustion chamber, the introduction of gas or oil throughline I I4 against the pressure in the combustion chamber, the continuous ignition of the fuel by means of a spark or other ignition means and the continuous removal of the gases to the input well controlled by the automatic valve I02 which releases pressure above the desired or necessary amount. A manhole I22 is provided for inspection, cleaning, and the like.

The following illustrates the operation of the invention in one field (Allen County, Kansas) A B o D Gravity, A. P. I .degrees.. 19. 2 22. 3 28. 0 21.8 Gasoline and naphtha content.per cent. 0 7. 5 32.0 7. 5 Burning oil d 0 10. 0 10.0 10.0 Fuel oil residue do 100 82.5 61. 6 82.

051 112 4 Cold test 0 S .per cent. 1 0

A" is the natural crude as it comes from the ground at a depth of 875 feet.

B is .A which has been brought to incipient cracking at 800 F. and is then flashed into a still to remove 17.5% of gasoline and distillate. This amount of cracking is insufficient to form any appreciable amount of carbon so that it could be directly introduced into a well advantageously without clogging the pores in the sand. At the same time it not only heats and fluxes the oil in the formation but reduces the viscosity by solvent action also. Its viscosity is well below the viscosity of the crude. However, the best effect is attained by the introduction of the hot overhead vapors which when condensed have a viscosity of and have a perfect solvent action on the crude. The 82.5% residue has a viscosity practically the same as original crude (I04) and cold test of 5 F.

C is a typical "synthetic crude oil made from A and contains an amount of carbon which results are produced are derived from the crude oil itself. Thus, the invention is especially applicable to wells which have ceased to flow or from which the oil can be extracted only with difficulty. In practicing the invention it is essential that the pressure in the cyclic system be greater than the pressure in the formation and the latter may vary within relatively wide limits, say '100 pounds per square inch to 1000 pounds per square inch, depending upon the particular formation. The pressure in the cyclic system may be derived either by virtue of the temperature of the recycled materials, which will usually be within the range of 650 F. to 1000 F. in conduit 56, or by virtue of additional pressure supplied through suitable pumping means. The temperature of the overhead distillate (kerosene, gasoline and gas oil) passing through line It will ordieventually. occludes the input well but is very v effective in increasing production.

D is the crude oil after the 17.5% taken out of B" is mixed with 82.5% of the natural crude in the ground. The viscosity is much less than one half and the cold test is 20 lower than the crude and the blend is perfectly uniform. This illustrates the change of character of the crude in the ground after injection of vapors.

This process results in the thinning of the natural crude oil in situ, thereby increasing its production and, secondly, the dehydration of the crude oil for a high grade marketable fuel oil with an improvement in all operations and products. The results are obtained in a closed cyclic system and the raw materials whereby the improved tion is to be subjected .to cracking.

narily be at least 400 F. and the temperature of hot gases introduced through conduit I00 will ordinarily vary within the range of 400 F. to 1000 F.

While the illustration given above applies to the use of oil from the least from which secondary recovery of oil is being taken, in many cases it is'advantageous to bring in oil from sources outside the lease. These problems are largely economic in character. Whereoil such as cheap gas oil may be had more cheaply than crude oil then such outside sources are desirable. As previously indicated, the crude distillate may contain kerosene, gasoline and gas oil. When the lighter distillates are used then it is not necessary to have as substantial equipment as in those cases where the oil to be injected into the forma- Cracking equipment is mechanically more substantial and is very much more expensive than mere heating equipment so that cheap low viscosity oils of any character may often be used economically without cracking. The introduction of the heated oil will ordinarily be continuous and more or less simultaneous with the withdrawal of crude from i any adjacent point. This, however, is 'not neceswithdrawn even from the same well often with at least a portion of the extracted petroleum to a temperature of 650 F. or above in order to obtain a lighter fraction therefrom (3) thereafter reintroducing into the deposit at least a part of the lighter fraction thus obtained and (4) causing said fraction to penetrate to a considerable distance within the deposit in order to decrease the viscosity of the residual heavy petroleum within the deposit and to facilitate the further recovery of such petroleum therefrom.

ROY cRoss.

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