AUTONOMOUS VALVE, SYSTEM, AND METHOD

Abstract

A method for controlling a Steam Assisted Gravity Drainage (SAGD) System including injecting steam through an injector well into a formation in thermal contact with the system; automatically admitting, reducing or denying entry of fluid to a producer well through a valve based upon both of temperature and pressure. Further, a Steam Assisted Gravity Drainage (SAGD) System including a producer well having a valve that automatically admits, reduces or denies entry of fluid to a producer well through the valve based upon both of temperature and pressure.

Description

BACKGROUND

In the resource recovery industry, it has been found that bitumen may exist in some deposits in a form too viscous for production in the traditional method. These deposits can be produced however using a process known in the art as Steam Assisted Gravity Drainage (SAGD). While the method is quite effective, it is known that steam breakthrough to the producing well is detrimental. Many efforts have been made to avoid such breakthrough and these all have utility but the art is always in search of alternative methods and apparatuses that that can account for particular situations or improve the effectiveness of the effort.

SUMMARY

A method for controlling a Steam Assisted Gravity Drainage (SAGD) System including injecting steam through an injector well into a formation in thermal contact with the system; automatically admitting, reducing or denying entry of fluid to a producer well through a valve based upon both of temperature and pressure.

Further disclosed is a Steam Assisted Gravity Drainage (SAGD) System including a producer well having a valve that automatically admits, reduces or denies entry of fluid to a producer well through the valve based upon both of temperature and pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is an illustration of the system disclosed herein within a SAGD environment;

FIG. 2 schematically illustrates a system comprising a tubular with a valve configuration as taught herein in an open condition;

FIG. 3 is the view of FIG. 2 with the valve in a closed condition;

FIGS. 4 and 5 are similar to those of FIGS. 2 and 3 but with a portion of the housing spaced from the tubular to create a fluid pathway therebetween; and

FIG. 6 is an exemplary saturation curve.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring to FIG. 1, a system 10 is illustrated. The system is a part of a larger SAGD system 2 that is only schematically illustrated but will be understood by one of ordinary skill in the art to contain a steam injector well 4, and a producer well 6. Steam warms the formation between the injector 4 and producer 6 wells causing target fluid to become mobile and migrate with gravity to the producer well 6. Target fluids are then drawn out of the producer well 6. Steam in the producer well 6 can occur due to breakthrough of steam directly or by evolution of steam from liquid due to thermodynamic conditions at the producer well. Both are undesirable. The temperature at which steam occurs is dependent upon pressure. System 10 is disposed at one or more portions of the producer well 6 where fluids exterior to the well may freely enter if the system 10 is in the open condition illustrated in FIG. 2, may enter at a reduced rate if in a choked position between the positions illustrated in FIGS. 2 and 3, and where fluids may not enter if the valve configuration is in the condition illustrated in FIG. 3 (unless provision has been made to allow choked flow in this condition, such as by providing castellation or similar construction on one or more portions of the valve configuration).

System 10 is configured to require more than one physical property to which it is exposed to ensure activation at the appropriate time and only under appropriate conditions. More specifically, temperature alone or other parameter alone does not activate the system 10. Rather simultaneous parameters of temperature and pressure are required to activate the system 10. This will avoid erroneous closures that otherwise would limit production without need. The system 10 includes a tubular 12 having ports 14 (one or more ports, the depiction of several around the circumference of tubular 12 is not intended to be limiting). Tubular 12 is a part of a producer well and in an embodiment is a part of the production string 8 therein (see FIG. 1). There may be one or more system 10 configurations in any given producer well 6. These systems may be separated by one or more packers 11. System 10 further includes an autonomous valve 16 comprising a housing 18, a fluid chamber 20, and a piston 22 exposed on one end 24 to the chamber 20 and at the other end 26 to the ambient conditions in the well. The piston 22 includes a closure member 28 configured to interact with the ports 14 to either openly allow flow through the ports 14, choke flow through the ports 14, or prevent flow through the ports 14. In embodiments, the autonomous valve may also include a seat 30 against which the closure member 28 may seat when in the condition of FIG. 3. Also illustrated is a base 32 that may be an insulator to thermally separate the balance of the autonomous valve 16 from the tubular 12.

While the autonomous valve 16 is illustrated in FIGS. 2 and 3 in close proximity to the tubular 12, it is also contemplated to move the housing 18 away from the tubular 12 to allow fluid external to the tubular 12 to essentially surround the autonomous valve 16 (See FIGS. 4 and 5). This helps to ensure the autonomous valve 16 temperature input is from the environment, flowing fluid 13 from the exterior into the tubular 12 or both. Such an embodiment insulates the autonomous valve 16 from affect by temperature of fluid within the tubular 12, which may be different due to commingling with fluid from different zones as that fluid makes its way to surface through the production string.

The autonomous valve 16 is responsive to a combination of pressure and temperature but to neither alone. The exposed nature of piston 22 at end 26 to the ambient while the other end 24 of piston 22 is exposed to the chamber 20 means that in order for the piston to move, both temperature and pressure must be within certain parameters. This is related to the phase diagram/saturation curve of a fluid 34 contained within the chamber 20. All fluids have a phase diagram and a saturation curve where the gas phase is in equilibrium with the liquid phase for a given temperature and pressure acting on the particular fluid. A basic representation of a generic phase diagram/ saturation curve is illustrated in FIG. 6. When the fluid is in the liquid region of the phase diagram, the valve will be in the open position and stay in that position until the combination of temperature and pressure changes causes the fluid to reach conditions represented by the saturation curve. The saturation curve represents the conditions at which the fluid in the valve will start to evolve steam. This evolution of steam will cause the piston to move the valve to a choked or closed position.

When conditions of the fluid in the chamber 20 change along the saturation curve line or into the liquid region, the piston 22 will move until equilibrium is again established. For example, the piston may move in the closing direction if temperature is increased or pressure is decreased from where either of those parameters were immediately prior or may move in the opening direction if temperature is decreased or pressure is increased from where either of those parameters were immediately prior. When the temperature is increased and the valve reaches its full stroke, the pressure in the chamber will climb, therefore keeping the valve closed. The effects of changes in pressure and temperature can also happen simultaneously. This is because whenever the system experiences a temperature and pressure that intersect somewhere along the saturation curve other than where on the saturation curve line the intersection was before the change, the equilibrium of fluid in the chamber 20 is lost and reestablishment of equilibrium may result in piston movement if at the new equilibrium the piston movement is not otherwise constrained by mechanical limits. The new equilibrium will include a different volume of the fluid 34 in the gas phase. Because the density of the gas phase is less than of the liquid phase, a greater or lesser occupancy of the chamber volume by one or the other (gas or liquid) will proportionally grow or contract the chamber causing the piston 22 to move toward or away from the ports 14, respectively. The degree of movement of piston 22 depends upon how far along the saturation curve the temperature and pressure intersection move from the immediately previous position limited, of course, by mechanical constraints of system 10. For any given pressure and temperature, the greater the distance between the intersection, the greater the movement of the piston 22 limited, of course, by mechanical constraints of system 10.

In embodiments, the autonomous valve 16 can be modified to react to the temperature and pressure in a different manner by incorporating a biasing member 36 (see FIG. 5) in the chamber 20. The biasing member 36 may be a compression member or a tension member, a tension member of course needing to be attached to the piston 22, to achieve opposing results. How much deviation will be achieved from the natural response to temperature and pressure depends upon the spring force of the biasing member 36 and the piston area. This allows the autonomous valve 16 to be adjusted to react to close or to open in a delayed manner relative to what the temperature and pressure would do alone or in an advanced manner to the conditions experienced. The biasing member 36 may be placed within the chamber 20 in embodiments or elsewhere providing a biasing force may be applied to the piston in one direction or the other.

The foregoing embodiments generally have fluid in the chamber 20 that has the same saturation curve as the surrounding fluid such that as conditions allow the surrounding fluid to evolve steam, the fluid in the chamber will also evolve steam. This is advantageous for controlling the wellbore because the valve will restrict inflow when that inflow is evolving steam (or close to evolving steam if the piston is biased). Restricting steam can improve the overall well drawdown profile and also reduce equipment wear caused by the high velocity steam flow. In an alternate embodiment however, the composition of the fluid in the chamber 20 may be modified from the surrounding fluid so that the chamber fluid has a different saturation curve than the surrounding fluid. This will allow the chamber fluid to evolve steam earlier or later than the surrounding fluid to create an actuation of the piston in an advanced or delayed manner, respectively.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1: A method for controlling a Steam Assisted Gravity Drainage (SAGD) System including injecting steam through a well into a formation in thermal contact with the system; automatically admitting, reducing or denying fluid out of the formation through a valve based upon both of temperature and pressure.

Embodiment 2: The method as in any previous embodiment wherein the automatically admitting, reducing or denying entry of fluid is by enlarging or reducing a flow passage of the valve.

Embodiment 3: The method as in any previous embodiment wherein the enlarging or reducing is by retracting or extending a piston relative to the flow passage of the valve.

Embodiment 4: The method as in any previous embodiment wherein the automatically admitting, reducing or denying entry of fluid is in response to pressure and temperature on a graph intersecting at a point on a saturation curve line for a particular fluid in the valve different than a point on the saturation curve line where temperature and pressure intersected immediately previously.

Embodiment 5: The method as in any previous embodiment wherein the extending occurs when temperature and pressure intersect on the saturation curve line at a point consistent with more steam evolution than the point at which temperature and pressure intersected immediately previously.

Embodiment 6: The method as in any previous embodiment wherein the retracting occurs when temperature and pressure intersect on the saturation curve line at a point consistent with less steam evolution than the point at which temperature and pressure intersected immediately previously.

Embodiment 7: The method as in any previous embodiment further including biasing the piston to a position.

Embodiment 8: The method as in any previous embodiment wherein the biasing is in the direction of the extending of the piston.

Embodiment 9: The method as in any previous embodiment wherein the biasing is in the direction of the retracting of the piston.

Embodiment 10: The method as in any previous embodiment further comprising selecting a fluid to be resident in the valve, the fluid having a particular saturation curve.

Embodiment 11: The method as in any previous embodiment wherein the injecting is through an injector well.

Embodiment 12: The method as in any previous embodiment wherein the automatically admitting, reducing or denying fluid flow is to a producer well.

Embodiment 13: A Steam Assisted Gravity Drainage (SAGD) System including a wellbore system in a subsurface formation, the wellbore system having a valve that automatically admits, reduces or denies entry of fluid to a production flow through the valve based upon both of temperature and pressure.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited.

Claims

1. A method for controlling a Steam Assisted Gravity Drainage (SAGD) System comprising: injecting steam through a well into a formation in thermal contact with the system;automatically admitting, reducing or denying fluid flow out of the formation through a valve based upon both of temperature and pressure.

2. The method as claimed in claim 1 wherein the automatically admitting, reducing or denying entry of fluid is by enlarging or reducing a flow passage of the valve.

3. The method as claimed in claim 2 wherein the enlarging or reducing is by retracting or extending a piston relative to the flow passage of the valve.

4. The method as claimed in claim 1 wherein the automatically admitting, reducing or denying entry of fluid is in response to pressure and temperature on a graph intersecting at a point on a saturation curve line for a particular fluid in the valve different than a point on the saturation curve line where temperature and pressure intersected immediately previously.

5. The method as claimed in claim 3 wherein the extending occurs when temperature and pressure intersect on the saturation curve line at a point consistent with more steam evolution than the point at which temperature and pressure intersected immediately previously.

6. The method as claimed in claim 3 wherein the retracting occurs when temperature and pressure intersect on the saturation curve line at a point consistent with less steam evolution than the point at which temperature and pressure intersected immediately previously.

7. The method as claimed in claim 3 further including biasing the piston to a position.

8. The method as claimed in claim 7 wherein the biasing is in the direction of the extending of the piston.

9. The method as claimed in claim 7 wherein the biasing is in the direction of the retracting of the piston.

10. The method as claimed in claim 1 further comprising selecting a fluid to be resident in the valve, the fluid having a particular saturation curve.

11. The method as claimed in claim 1 wherein the injecting is through an injector well.

12. The method as claimed in claim 1 wherein the automatically admitting, reducing or denying fluid flow is to a producer well.

13. A Steam Assisted Gravity Drainage (SAGD) System comprising: a wellbore system in a subsurface formation, the wellbore system having a valve that automatically admits, reduces or denies entry of fluid to a production flow through the valve based upon both of temperature and pressure.