US2293196A - Method and apparatus for completing wells - Google Patents

Description

process and. apparatus for completing gas and oil obtained from PatentedAug. i8, 1942 l UNITED STATES PATENT OFFICE Alllqlxlyg ron commer@ mamon AND James S. Crump, Houston,

'.lex.,V assigner to i Standard Oil Development Company, a corporation oi' Delaware application August 2e, 1939, sensi No. 292,011

4The prsent invention relates to an improved l'oil wells.

'An object of the present invention is to complete high gas-oil ratio oil wells vso that'oil containing a low gas ratio may be obtained from the Well. l

Inv accordance withmy invention a mixture of a producing formation penetrated by a-borehole is separated within the borehole so that oil is'obtained which has a low oil-gas ratio and in addition gas is obtained from the well.' rIjhe gas may be obtained at a pressure substantially the same as that existing in the producing formation and may be returned to the producing zone by Vrepressuring by the expenditure of very little additional energy. Other objects and advantages may be seen from the following description taken with the drawing in which the sole ligure is asectional view through a well producing oil and gas havingapplied thereto a modiiication of the present invention, As shown by the'igure, `a borehole I penetrates a producing formation 2. is carried down Ia substantial distance'below the producing formation' 2 for reasons which will later be apparent. A casing -3 having its `end closed by clogre l isv lowered into the borehole so that end ing formation 2. This casing is provided with a cement plug i above andvcement plug 8 below producing formation 2, in order to prevent Iluid leakage between the wall of the borehole This Aborehole ed to a diil'erent source s claims. (ci. 16e-z) y Neilan Company. Regulatorspf this type have the valve mechanically connected to a diaphragm with each side ofthe diaphragm fluidly connectof pressure.

In the schematic drawing,A regulator Il is provided with diaphragm I8 -connected tovalve Ill by mechanical linkage I8. Pressure in casing 3 has access to one side of diaphragm I8 through at a substantial distance below produc and the casing as is well understood in the art.

Casing 3 is perforated 'with periorations 'I at a point opposite formation! so that iluid from the formation may enter directly into the casing.` A tubing 8 provided with check valve 8 is placed within casing 3 so that its lower end reaches well below' the producing formation 2..

l valve I8 are well known tothe art. A satisfactory regulator for use in: practicing the present invention is describedznand illustrated on pages 43. 44 and Fig. 24 of the University ot Oklahoma Bulletin of the 1938 Southwestern Gas Measurement Short Course,

' New Series No.. 748, and another is back pres- 'Sllre regulator #27 manufactured by the Mason.

space between the casing and the .Iltis `causes the difference in line I2 and pressure ingtubing 8 has access to the'other'side of the diaphragm through line 28. l vAs thus arranged, regulator. II will close valve I8 when pressure in the upper end of tubingI 3 approaches the pressure in the upper end of the casing, so the difference in the two pressures is small. In a similar manner regulator II will openvalve I8 when a substantial decrease in the pressure in the upperend of tubing 8 pressurebetween these two pipes to become relatively large. l

The formation pressure in producing formatio 2 causes a mixture -of oil and gas to owthrough the perforations 1 and into casing 3. When this mixture enters the space within Vcasing 8 the reduction in pressure and change in direction of the `iluid allows the oil to separate from the gas. The oil is heavier so it drops down and rests upon the bottom 4 of the casing while the gas iillsthe upper portion of casing 3. After a certain lperiod of time the system will come to equilibrium with the level of the oil'within casing 3 being at point I3. .It isevident that it after the system reaches this condition the valve I8 is opened the position of liquid level I3 will drop the gas pressure in the casingforcing the oil up through tubing 8 and out of the well at the. surface of the earth. If this valve allowed to remain open, eventually. all oi Y, the oil from casing 8 will be produced and a mixture 'of gas and oil as it comes from the formation 2 will then ow through tubing 8.

Inaccordance with my preferred method of carrying out the invention the regulator II `is set to close valve III as soon as the oil level I 3 drops to such a low point that it no longer forms a liquid seal I8 is provided with a small by-pass I4 which allows, gas to be produced from the tubing at a slow rate. After ,valve I8 has closed the bypass Il allows the gas withwhich tubing-8has become filled to be'slowly released so that as the oil `is produced from formation 2` and illls the lower end oi' casing v8 the oil level in tubin'g 8 is allowed to slowlyl rise.f After `the oil level is tubing .I rises to such a height that the and allows a mixture of oil and gas to be produced from the well. Valve.l

' a liquid seal.

gas-oil ratio oil well having its pressure difference between the oil in tubing 8 and that in the upper end of casing 3 reaches a predetermined amount the regulator II opens valve I0 and allows oil to be once again produced through tubing 8 until the oil level I3 drops so that there is no longer a liquid' seal and the pressure in tubing 8 and that in casing 3 are partially equalized, when the valve i0 is again closed and the cycle is repeated.

' As a modification of the present invention the regulator always above the lower end of tubing 8 and forms When this modification of the invention is desired, the regulator II opens valve I and allows oil to be produced, the liquid level I3 dropping. AS the liquid pressure in the top of tubing 8 gradually decreases because there isnot so much oil in casing 3 to balance the liquid in tubing 8. When the liquid level I3 is near the bottom of tubing- 8 the pressure becomes 'so low that the regulator closes Valve I0 and allows oil from formation 2 to flow into' the casing and partially balance the liquid in tubing 8. When the height of liquid I3 has risen to a certain distance the pressure in tubing 8 will be increased, regulator II will open valve I0, and the cycle will be repeated,

It is evident that if production of fluid through tubing 8 does not produce sufficient drop in the formation pressure gas may be withdrawn from the upper part of casing 3 by means of connection I5 provided with valve I5. The gas removed through Valve I6 is at a very high pressure and is particularly suitable for repressuring.

While I have disclosed several specific modifications of carrying o'ut my invention, it is evident that other procedures may be used for carrying out the broad features of the present invention and I do not intend to be bound by the specific examples but wish to claim my invention as broadly as the prior art permits.

I claim:

1. Apparatus for producing fluid from a high borehole penetrating a substantial distance below a producing formation comprising, in combination, a casing arranged within said borehole with its lower end a substantial distance below said producing formation, perforations in said casing opposite said producing formation, a string of tubing arranged in said casing with its lower end adjacent the lower end of said borehole, a closure for the upper end of said casing, a valve arranged in the upper end of said string of tubing, a relatively small by-pass around said valve and a pressure regulator arranged to open said valve when the may be set so that the oil level I3 is level I3 drops the pressure in the upper end of the tubingbecomes less than that in the upper end of the casing by a predetermined amount, and to close the valve when the pressure difference between thesel two points becomes less than a predetermined value.

2. Apparatus in accordance with claim 1 in which a conduit controlled by a valve is attached to the upper end of said casing in fluid communication with the interior thereof, l

3. In a high gas-oil ratio oil well having a borehole penetrating a substantial distance below a producing formation with a casing arranged therein, means for fluid communicationV between said producing formation and the interior of said casing, a string of tubing within said casing with its lower end adjacent the lower end of said borehole, and aA closure for the upper end of said casing, means for controlling the flow of iiuid through said tubing vcomprising in combination a valve arranged in the upper end of said string of tubing, a small by-pass around said valve, a pressure regulator in fluid communication with the upper portion of said casing arranged to open said valve when the pressure in the upper end of the tubing becomes less than that in the upper end of the casing by a predetermined amount, and to close the valve when the pressure diiference between these two points becomes less than a predetermined value.

4. A process for producing fluid from a high gas-oil ratio oil well in which the bore hole penetrates a substantial distance below. a producing formation and is provided with a casing perforated a-t the producing formation and lwith a string of tubing having its induction end a substantial distance .below the producing formation comprising the steps of allowing liquid to accumulate in the bottom of the borehole until its upper surface is substantially above the induction end of said tubing, producing liquid through said tubing until said liquid surface drops below the induction end of the tubing and gas fills the tubing, bleeding gas from the upper end of said tubing at a rate slower than the rate of liquid accumulation in said borehole whereby liquid accumulates in the bottom of the well and rises within said tubing and again allowing liquid to be produced through said tubing.

5. A process in accordance with claim 4 in which high pressure gas isnwithdrawn at the surface vof the earth from the space between the tubing and casing in order to allow liquid to accumulate in the bottom of the borehole at the desired rate.

I JAMES S. CRUMP.

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