US3385227A - Bottom hole separator - Google Patents

Description

May 28, 1968 w. J. HART, JR

BOTTOM HOLE SEPARATOR Filed NOV. 14, 1966 INVENTOR. 14444 7'5? J. HARZJA.

United States Patent 3,385,227 BOTTOM HOLE SEPARATOR Walter J. Hart, Jr., Odessa, Tex., assignor to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 14, 1966, Ser. No. 594,194 9 Claims. (Cl. 103-434) ABSTRACT OF THE DISCLOSURE Apparatus for intermittently producing liquids from a well penetrating a subterranean formation producing gas and liquids in which a housing is mounted on the lower end of production tubing which opens into the housing. Liquid is conducted from within the well below a gas-oil interface therein into the housing, and gas is periodically introduced into the housing to displace the liquid therein upwardly through the production tubing. Pressure responsive valves control flow of fluids into the housing.

This invention resides in an apparatus for producing fluids from wells which are incapable of flowing naturally or have gas-fluid ratios which are detrimental to ultimate production.

In the production life of an oil well a static condition will be reached wherein there is insufiicien-t gas pressure to overcome the hydrostatic head created by fluid accumulation in the well bore. This condition is principally caused by a decrease of reservoir pressure. Another contributing factor to the termination of a wells ability to flow is the presence of formation Water entering the well bore which will produce a fluid hydrostatic head equal the pressure of the gas which enters the well bore.

As a well becomes watered out or the formation gas is depleted to the extent that production is seriously restricted or terminated, it has heretofore been necessary to periodically swab the well, thereby reducing the fluid hydrostatic head in the well bore, or install mechanical pumping equipment in the well. Either operation decreases the economic efliciency of producing oil, requires additional supervision and the utilization of expensive equipment. In the situation where mechanical pumping equipment is installed, the gas-fluid ratio of the produced fluids may gas lock the pump and seriously decrease the pumping efficiency.

This invention resides in an apparatus for intermittently producing fluids from wells which possess high gasfluid ratios or are incapable of flowing naturally. More specifically this apparatus is adapted for use in wells which produce suflicient gas pressure to flow intermittent slugs of fluids to the surface if the fluid hydrostatic head within the well bore is maintained at a low level. This apparatus functions to separate the gas from the liquids entering the well bore and controls the height of liquid accumulating in the well bore by intermittently opening the tubing to deliver fluid from the well to the surface.

Production tubing extends from the surface of the earth into the housing of the apparatus of this invention. A differential pressure flow valve is mounted on the housing to control communication of the inner chamber of the apparatus with the annulus formed between the casing and the production tubing. A spring and bellows operated fill valve, as preferred in this invention, is mounted on the tool and control-s the flow of liquid into the inner chamber of the apparatus housing for subsequent delivery to the surface by fluid pressure passing through the differential pressure flow valve.

In the drawing:

The drawing is a diagrammatic view partially in vertical cross section showing the bottom hole separator of this invention. 'In the drawing, a well bore 2 extends from the surface of the earth downward through a hydrocarbon-containing formation 4. Casing '6, as preferred in this invention, is installed within the well bore 2 and set through the hydrocarbon-containing formation 4 with cement 8 placed in the annulus formed bet-ween the casing 6 and the well bore 2. Perforations 10 are created through the casing 6, cement sheath '8 and into the hydrocarbon-containing formation 4.

Production tubing 12 extending from the surface downward through the casing 6 is attached to the housing 14 of the apparatus of this invention and terminates within the inner chamber '15 of the housing 14. A differential pressure flow valve 16 is mounted on the housing 14 to control the flow of fluid from the annulus 1 8- into the inner chamber 15.

-A fill valve 20- is mounted in the inner chamber '15 and, as preferred in this invention, actuated by bellows 22 which are in communication with the annulus 18. A helical spring 24 is attached to the actuating rod 26 of the fill valve 20 and adapted to hold the till valve 20 in an open position. The fill valve 20 operates to control the passage of fluid through the fill tube 28, fill ports 30, into the inner chamber 15 and upward through the production tubing 12 to the surface. 7

At the start of the filling operation of this invention the pressure within the inner housing 15 and annulus 18 has stabilized, therefore the helical spring 24 is holding the till valve open and the differential pressure flow valve 16 is closed. Fluids enter the casing 6- through perforations 10. The gas separates from the liquid and occupies the upper portion of the annulus 18. As gas pressure increases within the annulus 18, a downward force is exerted on the valve 20 by the bellows 22 thereby closing the valve 20. The pressure in the annulus causes liquid to rise in the fill tube 28 and exert a pressure on the bottom of the valve 20.

As liquid continues to rise in the annulus it causes an increase in pressure within the fill tube 28 below the valve 20. The pressure below the valve 20 will increase to a point at which the spring 20 opens the valve 20 and allows liquid to flow from the annulus 18, up the fill tube *28, through the valve 20 and fill ports 30 and into the inner chamber 15.

As liquids flow into the inner chamber 15, the height of liquid in the annulus decreases thereby increasing the hydrostatic head of liquid in the fill tube 28 and decreasing the pressure exerted on the bottom of the valve 20. This decrease in pressure on the bottom of the valve 20 permits the valve 20 to be closed by the force exerted by the bellows 22.

Liquids are intermittently delivered to the inner chamber 15 until the hydrostatic head within the inner chamber 15 produces a pressure which actuates the ditferential pressure flow valve 16 and causes flow valve 16 to open and communicate the gas filled annulus 18 with the inner chamber 15. Gas enters the inner chamber 15 and forces the slug of liquid from the inner chamber upwardly through the production tubing 12 to the surface where it is gathered in a field stock tank (not shown).

The production of gas from the annulus 15 through the tubing 12 to the surface lowers the pressure exerted on the differential pressure flow valve 16 and causes it to close. A new filling cycle will then be initiated.

The operation of this apparatus is regulated by the gravity of the well fluid, the compressive strength of the valve spring, the area of the fill valve, the area of the bellows, the distance the apparatus housing is spaced above the liquid level in the well bore, the pressure ranges which actuate the differential area flow valve and the amount of back pressure that is held on the annulus. Owing to these numerous variables, it is obvious that the operation of this apparatus may readily be adapted to an extremely wide range of well conditions and hence be utilized to extend the flowing life of practically any well.

It is preferred in this invention that the flow valve be a ball and seat type valve. Regardless of the type of valve used, it is preferred however that the effective orifice area of the valve should be substantially equal to the effective area of the bellows. By so sizing the effective bellows and valve orifice areas, the operator is provided a relationship between the upward and downward forces subjected on the valve. Such a 1:1 ratio will simplify further calculations and help the operator correctly match the operation of the tool to the particular producing characteristics of the well.

The first step in matching apparatus operation to the producing characteristics is to determine the stabilized liquid level in the annulus when the well is open to the stock tank. This level may be easily obtained by opening the well to the surface field gathering equipment until the well ceases to produce. A weight bar may subsequently be run into the well to determine the height of liquid in the annulus. This height of liquid in the well bore substantially represents the head of fluid which the formation pressure of the well will support.

To minimize the back pressure held on the formation and thereby decrease the resistance to fluids entering the well bore, it is preferred that the housing of this apparatus be positioned above the perforations a distance equal to approximately one-fourth of the height of the liquid level of the well during stabilized conditions. By so positioning the inner chamber of the apparatus the operator is also assured a greater operating pressure range while maintaining optimum production.

After choosing the desired inner chamber position, the operator must determine the length of fill tube to be installed below the apparatus housing. It is preferred that the fill tube extend downward from the apparatus housing to a position adjacent to or below the hydrocarbon-containing formation.

The preferred compressive strength of the spring is determined by the position of the apparatus housing and the weight of the produced liquid. It is preferred in this invention that the pressure exerted on the valve by the spring should be substantially equal to the pressure exerted by a column of the produced liquid having a height equal to the distance from the top of the housing of the apparatus to the lower end of the fill tube. Although springs exerting more or less pressure may be utilized, it is preferred that the operator should choose a spring which will produce a pressure as nearly equal to this calculated value as may be readily obtained commercially. Obviously the operator may adjust the position of the housing to more nearly match the types of springs which are available so long as he does not deviate from the preferred housing position so radically that the entry of fluid will be restricted by the fluid head in the annulus.

An alternate method of positioning this apparatus and correctly sizing the spring for optimum apparatus operation is to install a spring producing 100 pounds per square inch pressure. The minimum length of fill tube may then be calculated. A spring of this strength dictates a minimum fill tube length of 250 feet for salt water to 350 feet for 62 API gravity condensate. Knowing the characteristics of the produced fluids the operator may thereby interpolate the minimum length of fill tube to install below the tool housing.

Having determined the position of the apparatus within the well, the spring strength, and knowing the producing characteristics of this particular well, the operator may choose a differential pressure flow valve for the tool. It is preferred in this invention that the valve should be actuated to open by an inner chamber pressure equal to approximately one-fourth the pressure exerted by the head of the liquid in the well during stabilized conditions 4 and adapted to close when the pressure within the inner chamber is approximately balanced with the annulus pressure. By so regulating the producing cycle of the tool, the slug of fluid will be discharged from the well before the annulus pressures increase sufficiently to restrict fluid entry into the well bore.

Where the spring strength and tool placement was determined by the above described alternate method, the selection of the differential flow valve is simplified. Where a pound per square inch spring is employed a differential flow valve of pounds per square inch will produce optimum performance of the apparatus of this invention.

Further control of this apparatus is obtained by holding a back pressure on the annulus by installing an orifice on the casing discharge line. This control is particularly useful where the well produces large amounts of gas and very little liquid. In this arrangement gas can be produced continually at the surface while the liquid enters the well bore and fills the inner chamber of the apparatus. The only requisite is that the orifice be of such limited size that all the gas entering the well bore will not be produced through the casing. The annulus pressure will then gradually increase to a pressure which will actuate the differential pressure flow valve.

The installation of the bottom hole separator of this invention will enable the operator to extend the flowing life of the well. By so extending the wells flowing life, production costs will be decreased with a corresponding decrease in well supervision, maintenance and the utilization of producing equipment.

Therefore I claim:

1. Apparatus for intermittently producing liquids from a well penetrating a subterranean formation producing gas and liquids comprising:

a string of production tubing extending down the well;

a housing mounted on the lower end of the production tubing, said production tubing opening into the housing near the lower end thereof;

a fill tube extending downwardly from the housing, said fill tube opening into the housing above the level at which the production tubing opens into the housing;

a pressure-responsive valve controlling flow from the fill tube into the housing adapted to permit flow when pressure within the fill tube increases; and

a flow valve opening into the housing above the level of the opening of the producing tubing in the housing, said flow valve adapted to open .and permit flow from within the well bore into the housing on an increase in pressure within the housing.

2. Apparatus for intermittently producing liquids from a well penetrating a subterranean formation producing gas and liquids comprising:

a string of production tubing extending down the well;

a housing mounted on the lower end of the production tubing, said production tubing opening into the housing near the lower end thereof;

a fill tube extending downwardly from the housing, said fill tube opening into the housing above the level at which the production tubing opens into the housing;

a pressure-responsive valve controlling flow from the fill tube into the housing adapted to permit fiow when pressure within the fill tube increases; and

a differential pressure flow valve opening into the housing above the level of the opening of the production tubing in the housing, said dififerential pressure flow valve adapted to open and permit flow from within the well bore into the housing on an increase in pressure within the housing.

3. Apparatus for intermittently producing liquids from a well bore penetrating a subterranean formation producing gas and liquids which form a gas-liquid interface within said well bore comprising:

a string of production tubing extending down the well bore;

a housing mounted on the lower end of the production tubing, said production tubing opening into the housing near the lower end thereof;

a fill tube extending downwardly from the housing, said fill tube opening into the housing above the level at which the production tubing opens into the housing and terminating within the well bore below the gas-liquid interface;

a pressure-responsive valve controlling flow from the fill tube into the housing adapted to permit flow when pressure within the fill tube increases; and

a differential pressure flow valve opening into the housing above the level of the opening of the production tubing in the housing, said differential pressure flow valve adapted to open and permit flow from with n the well bore into the housing on an increase in pressure within the housing.

4. An apparatus for intermittently producing liquids from a well bore comprising:

a string of production tubing extending from the surface of the earth downward through the well bore;

a housing mounted on the lower end of the production tubing and having an inner chamber in communication with the production tubing;

a fill tube extending downwardly from the housing to permit liquid within the fill tube to enter the inner chamber;

a fill valve positioned within the fill tube to control the passage of liquid from the fill tube into the inner chamber;

a bellows mounted on the inner wall of the housing;

an actuating rod connected on its upper end to the bellows, passing through the housing, connected on its lower end to the fill valve and adapted to be actuated by the bellows to close the fill valve;

a spring adjacent the actuating rod and adapted to urge the actuating rod to an upper extended position thereby urging the fill valve open; and

a differential pressure flow valve mounted on the housing and in communication with the well bore and the inner chamber and adapted to be actuated by the pressure within the inner chamber and the pressure in the well bore.

5. An apparatus as set forth in claim 3 wherein the fill valve is a ball type valve.

6. An apparatus for intermittently producing liquids from a well bore comprising:

a string of production tubing extending from the surface of the earth downward through the well bore;

a housing connected to the production tubing and having a hollow inner chamber which encompasses the lowermost end of said production tubing;

a bellows mounted on the outer surface of the housing;

a fill valve mounted within the inner chamber of the housing adjacent the bellows with the orifice through said fill valve being substantially equal to the effective area of the bellows;

an actuating rod connected on its upper end to the bellows, passing through the housing, connected on its lower end to the fill valve and adapted to actuate the fill valve;

a spring in contact with the actuating rod and adapted to oppose any downward force transmitted to the actuating rod by the bellows and urge the actuating rod upward to open the valve;

a fill tube connected to the lower end of the fill valve, passing through the inner chamber and extending downwardly through the well bore to provide a conduit for liquids from the well bore into the production tubing and the inner chamber of the housing; and

a differential pressure flow valve mounted on the housing and adapted to intermittently permit gas in the well bore to enter the inner chamber of the housing.

7. An apparatus as set forth in claim 5 wherein the compressive force of the spring will urge the bellows upward and oppose a downward force on the bellows substantially equal to the pressure exerted on an area equal to the orifice area of the valve by a column of the liquids which enter the well bore whose height is equal to the length of the fill tube.

8. An apparatus as set forth in claim 6 wherein the length of the fill tube is substantially one-fourth the length of a column of the produced liquids which will stabilize in the well bore when the well bore is open to the atmosphere.

9. An apparatus for intermittently producing liquids from a well bore extending from the surface of the earth downward through a hydrocarbon-containing formation comprising:

a string of production tubing extending from the surface of the earth downward through the well bore;

a housing connected to the production tubing and having a hollow inner chamber which encompasses the lowermost end of said production tubing, and said housing positioned within the well bore at a location above the hydrocarbon-containing formation a dis tance equal to at least one-fourth the distance to which produced liquids will rise above the hydrocarbon-containing formation when the well bore is open to the atmosphere and the fluids within the well bore have stabilized;

a bellows mounted on the outer surface of the housing;

a fill valve with an orifice area substantially equal to the effective area of the bellows, mounted within the inner chamber of the housing adjacent the bellows;

an actuating rod connected on its upper end to the bellows, passing through the housing, connected on its lower end to the fill valve and adapted to transmit forces from the bellows to the fill valve;

a compression spring in contact with the actuating rod and adapted to oppose any downward force transmitted to the actuating rod by the bellows and urge the actuating rod upward to open the valve, said compression spring having a compressive strength which will oppose a downward force on the bellows substantially equal to the pressure produced by a column of the produced liquids whose height is equal to the length of the fill tube and Whose area. is equal to the orifice area of the valve;

a fill tube connected to the inlet end of the fill valve, passing through the inner chamber and extending downwardly from the housing to a position in the well bore adjacent the hydrocarbon-containing formation to provide a conduit for liquids from the well bore into the production tubing and the inner chamber; and

a differential pressure flow valve mounted on the housing adapted to be actuated by the pressure of the well bore and the inner chamber to intermittently permit gas in the well bore to enter the inner housing and be delivered to the surface of the earth.

References Cited UNITED STATES PATENTS DONLEY J. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

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