CONTROL VALVE TIMING
A method for lifting drilling mud from subsea to a drilling vessel which a pump having a body with a chamber, and a bladder in the chamber. The bladder attaches to the body and defines water and mud sides in the chamber. A mud inlet valve allows mud into the mud side of the chamber; which moves the bladder into the water side and urges water in the water side from the chamber and through a water exit valve. Pressurized water enters the chamber through a water inlet valve, which in turn pushes the bladder and mud from the chamber through a mud exit valve. The bladder separates the mud and water as it reciprocates in the chamber. Water and/or mud inlet valves are opened before associated exit valves to reduce pressure fluctuations in the fluid lines.
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This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/792,157, filed Mar. 15, 2013, the full disclosure of which is hereby incorporated by reference herein for all purposes.
BACKGROUND OF THE INVENTION1. Field of Invention
The present disclosure relates in general to a system and method for timing the opening and closing of inlet and outlet valves used with a bladder pump to reduce pressure spikes within the pump.
2. Description of Prior Art
Subsea drilling systems typically employ a vessel at the sea surface, a riser connecting the vessel with a wellhead housing on the seafloor, and a drill string. A drill bit is attached on a lower end of the drill string, and used for excavating a borehole through the formation below the seafloor. The drill string is suspended subsea from the vessel into the riser, and is protected from seawater while inside of the riser. Past the lower end of the riser, the drill string inserts through the wellhead housing just above where it contacts the formation. Generally, a rotary table or top drive is provided on the vessel for rotating the string and bit. Drilling mud is usually pumped under pressure into the drill string, and is discharged from nozzles in the drill bit. The drilling mud, through its density and pressure, controls pressure in the well and cools the bit. The mud also removes formation cuttings from the well as it is circulated back to the vessel. Traditionally, the mud exiting the well is routed through an annulus between the drill string and riser. However, as well control depends at least in part on the column of fluid in the riser, the effects of corrective action in response to a well kick or other anomaly can be delayed.
Fluid lift systems have been deployed subsea for pressurizing the drilling mud exiting the wellbore. Piping systems outside of the riser carry the mud pressurized by the subsea lift systems. The lift systems include pumps disposed proximate the wellhead, which reduce the time for well control actions to take effect.
SUMMARY OF THE INVENTIONIn an example, disclosed herein is a method of lifting drilling mud from a subsea wellbore that includes directing an inlet flow of fluid to mud pumps that are disposed subsea, controlling portions of the inlet flow of fluid to individual mud pumps with inlet valves, and opening a one of the inlet valves while closing another one of the inlet valves. Timing the opening and closing of the selected inlet valves keeps individual mud pumps respectively associated with the one of the inlet valves, and the another one of the inlet valves are at the same time in communication with the inlet flow of fluid. This also enables a flow rate of the inlet flow of fluid to remain above a threshold value. The inlet flow of fluid can be drilling mud from the subsea wellbore, and opening and closing of the inlet valves is staggered to maintain the flow rate of the inlet flow of fluid at a substantially constant value. In an alternative, the inlet flow of fluid is water for driving the mud pumps, and opening and closing of the inlet valves is staggered to maintain the flow rate of the inlet flow of fluid at a substantially constant value. The mud pumps can be first, second, and third mud pumps that reciprocate between a mud intake cycle to a mud discharge cycle, and wherein the one of the inlet valves controls flow to the first mud pump and wherein the another one of the inlet valves controls flow to the second mud pump. In this example, the first mud pump changes from the mud intake cycle to the mud discharge cycle when the second pump changes from the mud discharge cycle to the mud intake cycle. Further in this example, the second mud pump changes from the mud intake cycle to the mud discharge cycle when the third pump changes from the mud discharge cycle to the mud intake cycle, and wherein a third inlet valve controls flow to the third mud pump, and wherein the third inlet valve begins to open prior to the another one of the inlet valves closing. Optionally, the another one of the inlet valves is a mud inlet valve, and wherein the mud pumps are driven by selectively flowing pressurized water to water spaces in the mud pumps through water inlet valves, and discharging water from the pumps through water discharge valves. In this example, the method can further include opening a one of the water discharge valves in a one of the mud pumps that is associated with the mud inlet valve.
An alternate method of lifting drilling mud from a subsea wellbore is disclosed herein and that includes directing an inlet flow of drilling mud from the subsea wellbore, controlling a first portion of the inlet flow of drilling mud to a first mud pump with a first mud inlet valve, controlling a second portion of the inlet flow of drilling mud to a second mud pump with a second mud inlet valve, and maintaining a flow rate of the inlet flow of drilling mud above a threshold value by opening the first mud inlet valve prior to closing the second inlet valve. The method can further include controlling a third portion of the inlet flow of drilling mud to a third mud pump with a third mud inlet valve, and opening the second inlet valve prior to closing the third inlet valve. The first mud inlet valve can begin to open at least about 0.5 seconds prior to when the second mud inlet valve is closed. The first and second mud pumps may reciprocatingly discharge mud through first and second mud discharge valves, and wherein pressurized water is selectively delivered to a water side of the first and second mud pumps for discharging mud from the first and second mud pumps.
In another alternative embodiment, disclosed is a method of pumping drilling mud from a subsea wellbore that includes providing first, second and third mud pumps subsea. In this example each pump includes a housing, a water space in the housing, a mud space in the housing, and a membrane in the housing that defines a barrier between the mud space and water space. The method further includes directing first, second, and third portions of a total flow of drilling mud respectively through first, second, and third mud inlet lines and to the first, second and third mud pumps, controlling the first, second, and third portions of the total flow of drilling mud in the first, second, and third mud inlet lines with first, second, and third mud inlet valves that are respectively disposed in the first, second, and third mud inlet lines. Also included with this method are the steps of sequencing the first, second, and third portions of the total flow of drilling mud in the first, second, and third mud inlet lines by closing the first mud inlet valve when opening the second mud inlet valve, selectively directing a flow of pressurized water to the water spaces in the housings of each of the first, second, and third mud pumps to urge drilling mud from the first, second, and third mud pumps, and maintaining the total flow of drilling mud above a threshold value by beginning to open the second inlet valve prior to fully closing the first inlet valve. In an example, the third inlet valve can be opened prior to fully closing the second inlet valve. In another alternative, water can be discharged from the water space of the second mud pump prior to beginning to open the second mud inlet valve.
Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:
While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF INVENTIONThe method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.
It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.
Shown in
A lower open space 54 is formed on a lower end of bladder 42 distal from upper open space 48, which in the example of
Still referring to
Water may be selectively delivered into water space 46 via a water supply line 76 shown depending from vessel 22 and connecting to lift pump assembly 34 (
A water inlet valve 96 shown in water inlet lead line 78 provides selective water communication from vessel 22 (
In one example of operation of pump 38 of
An example of pressurizing mud within mud space 44 is illustrated in
In the examples of
Bladders 42A-C respectively illustrated in pumps 38A-C are oriented to reflect an example of a pump stroke sequence of each pump 38A-C. In the illustrated embodiment, bladder 42A is biased towards manifold 80A and away from lead 68A, so that pump chamber 41A includes a greater volume of mud than water. Pump 38A thus represents an example of a transition from a mud filling stroke to a water filling stroke, which can range from an end of a mud filling stroke to the beginning of a water filling stroke. The illustrated embodiment of pump 38B depicts bladder 42B biased towards lead 68B and away from manifold 80B, which can be a transition from a water filling stroke to a mud filling stroke. Bladder 42C spans generally across a mid-portion of chamber 41C, thus representing pump 38C approximately mid-way through a mud or water filling stroke. Because the filling/discharging strokes of pumps 38A-C of
In one example of operation of the lift pump assembly 34 of
Still referring to
The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.
Claims
1. A method of lifting drilling mud from a subsea wellbore comprising:
- directing an inlet flow of fluid to mud pumps that are disposed subsea;
- controlling portions of the inlet flow of fluid to individual mud pumps with inlet valves; and
- opening a one of the inlet valves while closing another one of the inlet valves so that individual mud pumps respectively associated with the one of the inlet valves and the another one of the inlet valves are at the same time in communication with the inlet flow of fluid, and so that a flow rate of the inlet flow of fluid remains above a threshold value.
2. The method of claim 1, wherein the inlet flow of fluid comprises drilling mud from the subsea wellbore, and opening and closing of the inlet valves is staggered to maintain the flow rate of the inlet flow of fluid at a substantially constant value.
3. The method of claim 1, wherein the inlet flow of fluid comprises water for driving the mud pumps, and opening and closing of the inlet valves is staggered to maintain the flow rate of the inlet flow of fluid at a substantially constant value.
4. The method of claim 1, wherein the mud pumps comprise a first, a second, and third mud pumps that reciprocate between a mud intake cycle to a mud discharge cycle, and wherein the one of the inlet valves controls flow to the first mud pump and wherein the another one of the inlet valves controls flow to the second mud pump.
5. The method of claim 4, wherein the first mud pump changes from the mud intake cycle to the mud discharge cycle when the second pump changes from the mud discharge cycle to the mud intake cycle.
6. The method of claim 5, wherein the second mud pump changes from the mud intake cycle to the mud discharge cycle when the third pump changes from the mud discharge cycle to the mud intake cycle, and wherein a third inlet valve controls flow to the third mud pump, and wherein the third inlet valve begins to open prior to the another one of the inlet valves closing.
7. The method of claim 1, wherein the another one of the inlet valves comprises a mud inlet valve, and wherein the mud pumps are driven by selectively flowing pressurized water to water spaces in the mud pumps through water inlet valves, and discharging water from the pumps through water discharge valves, the method further comprising opening a one of the water discharge valves in a one of the mud pumps that is associated with the mud inlet valve.
8. A method of lifting drilling mud from a subsea wellbore comprising:
- directing an inlet flow of drilling mud from the subsea wellbore;
- controlling a first portion of the inlet flow of drilling mud to a first mud pump with a first mud inlet valve;
- controlling a second portion of the inlet flow of drilling mud to a second mud pump with a second mud inlet valve; and
- maintaining a flow rate of the inlet flow of drilling mud above a threshold value by opening the first mud inlet valve prior to closing the second inlet valve.
9. The method of claim 8, further comprising controlling a third portion of the inlet flow of drilling mud to a third mud pump with a third mud inlet valve, and opening the second inlet valve prior to closing the third inlet valve.
10. The method of claim 8, wherein the first mud inlet valve begins to open at least about 0.5 seconds prior to when the second mud inlet valve is closed.
11. The method of claim 8, wherein the first and second mud pumps reciprocatingly discharge mud through first and second mud discharge valves, and wherein pressurized water is selectively delivered to a water side of the first and second mud pumps for discharging mud from the first and second mud pumps.
12. A method of pumping drilling mud from a subsea wellbore comprising:
- providing first, second and third mud pumps subsea, and that each comprise a housing, a water space in the housing, a mud space in the housing, and a membrane in the housing that defines a barrier between the mud space and water space;
- directing first, second, and third portions of a total flow of drilling mud respectively through first, second, and third mud inlet lines and to the first, second and third mud pumps;
- controlling the first, second, and third portions of the total flow of drilling mud in the first, second, and third mud inlet lines with first, second, and third mud inlet valves that are respectively disposed in the first, second, and third mud inlet lines;
- sequencing the first, second, and third portions of the total flow of drilling mud in the first, second, and third mud inlet lines by closing the first mud inlet valve when opening the second mud inlet valve;
- selectively directing a flow of pressurized water to the water spaces in the housings of each of the first, second, and third mud pumps to urge drilling mud from the first, second, and third mud pumps; and
- maintaining the total flow of drilling mud above a threshold value by beginning to open the second inlet valve prior to fully closing the first inlet valve.
13. The method of claim 12, further comprising beginning to open the third inlet valve prior to fully closing the second inlet valve.
14. The method of claim 12, further comprising discharging water from the water space of the second mud pump prior to beginning to open the second mud inlet valve.
Type: Application
Filed: Sep 6, 2013
Publication Date: Sep 18, 2014
Applicant: Hydril USA Manufacturing LLC (Houston, TX)
Inventors: Ahmet Duman (Houston, TX), Dat Manh Nguyen (Houston, TX), Devon Daniel (Houston, TX)
Application Number: 14/020,586
International Classification: E21B 41/00 (20060101); E21B 34/06 (20060101);