APPARATUS FOR CONTROLLING WELL PRESSURE

• US 3,677,353 A
• Filed: 07/15/1970
• Issued: 07/18/1972
• Est. Priority Date: 07/15/1970
• Status: Expired due to Term

• Current Assignee: Gerald S. Baker
• Original Assignee: Gerald S. Baker
• Inventors: Baker, Gerald S.
• Primary Examiner(s): Brown, David H.
• Application Number:
  US05/055,105
• Time in Patent Office: 734 Days
• Field of Search: 175/25,38,218 166/91
• US Class Current: 175/25
• CPC Class Codes: E21B 21/08 Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure valve arrangements therefor E21B21/10

Abstract

There is disclosed apparatus which includes a choke for connection to the annulus between a well bore and a drill string extending into the bore, and a means for operating the choke to impose a back pressure on drilling fluid in the annulus either manually or automatically in response to certain well characteristics so as to maintain a predetermined pressure differential between it and formation fluid at the bottom of the well bore.

Claims

1. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there being a deviation, positive or negative, by which said pressure differential exceeds a predetermined value thereof;

apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke including a flow-restricting member movable toward and away from a seat for regulating the outlet fluid pressure, means for causing the flowrestricting member to move toward and away from the seat to respectively increase or decrease the outlet fluid pressure automatically in response to said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, means for producing a signal representing the position of said flow-restricting member, and means responsive to said signal for controlling the rate of change of said position.

2. Apparatus of the character defined in claim 1, including means for causing the flow-restricting member to move away from the seat for decreasing said outlet fluid pressure automatically in response to the value thereof exceeding a predetermined level and regardless of other well characteristics.

3. Apparatus of the character defined in claim 1, including means for causing the flow-restricting member to move away from the seat for decreasing the outlet fluid pressure automatically in response to the rate of increase thereof exceeding a predetermined level and regardless of other well characteristics.

4. Apparatus of the character defined in claim 6, including means for producing a sixth signal which represents outlet fluid pressure to cause the flow-restricting member to move away from the seat for decreasing said outlet fluid pressure automatically in response to the value thereof exceeding a predetermined level and regardless of other well characteristics, and means for producing a seventh signal which represents the rate of change of outlet fluid pressure to cause the flow-restricting member to move away from the seat for decreasing the outlet fluid pressure automatically in response to the rate of increase thereof exceeding a predetermined level and regardless of other well characteristics.

5. Apparatus of the character defined in claim 4, including means for manually producing an eighth signal to selectively cause the choke to increase or decrease the outlet fluid pressure regardless of said well characteristics.

6. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there Being a deviation, positive or negative, by which said pressure differential exceeds a predetermined value thereof;

apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke including a flow-restricting member movable toward and away from a seat for regulating the outlet fluid pressure in response to first and second signals, means for producing a first signal, and means for producing a second signal which represents the sum of inlet fluid pressure in a static state as adjusted to include said pressure differential and fluid pressure loss due to circulation within the well bore and which cooperates with the first signal to cause the flow-restricting member to move toward and away from the seat to respectively increase or decrease the outlet fluid pressure automatically in response to said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, said means for producing the first signal comprising means for producing a third signal representing inlet fluid pressure, means for producing a fourth signal representing the position of the flow-restricting member with respect to said seat, means for producing a fifth signal representing a damped position representing signal, and means for combining said signals in accordance with the equation;

First Signal Third Signal - Fourth Signal + Fifth Signal, so as to control the rate at which the flow-restricting member changes position with respect to said seat.

7. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there being a deviation, positive or negative, by which said pressure differential exceeds a predetermined value thereof;

apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke for regulating the outlet fluid pressure in response to signals, means for producing a first signal, means for producing a second signal which varies with well characteristics and cooperates with the first signal to cause the choke to increase or decrease the outlet fluid pressure automatically in response to said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, and means for producing a third signal which represents the value of fluid pressure within the outlet and overrides the first and second signals to cause the choke to decrease the outlet fluid pressure automatically in response to the value thereof exceeding a predetermined level and regardless of said well characteristics.

8. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there being a deviation, positive or negative, by which said pressure differential exceeds a predetermined value thereof;

apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke for regulating the outlet fluid pressure in response to signals, means for producing a first signal, means for producing a second signal which varies with well characteristics and cooperates with the first signal to cause the choke to increase or decrease the outlet fluid pressure automatically in response To said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, and means for producing a third signal which represents the rate of change of fluid pressure within the outlet and overrides the first and second signals to cause the choke to decrease the outlet fluid pressure automatically in response to the rate of increase thereof exceeding a predetermined level.

9. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there being a deviation, positive or negative, by which said pressure differential exceeds a predetermined value thereof;

apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke for regulating the outlet fluid pressure in response to signals, means for producing a first signal, means for producing a second signal which varies with well characteristics and cooperates with the first signal to cause the choke to increase or decrease the outlet fluid pressure automatically in response to said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, means for producing a third control signal which represents the value of fluid pressure within the outlet and overrides the first and second signals to cause the choke to decrease the outlet fluid pressure automatically in response to the value thereof exceeding a predetermined level and regardless of other well characteristics, and means for producing a fourth control signal which represents the rate of change of fluid pressure within the outlet and overrides the first and second signals to cause the choke to decrease the outlet fluid pressure automatically in response to the rate of increase thereof exceeding a predetermined level.

10. Apparatus for operating a drilling choke in response to the comparative values of characteristics within a well to the outlet of which the choke is connected, said apparatus comprising a reciprocable actuator for connection to the flow-restricting member of the choke, a source of hydraulic fluid under pressure, a four-way valve having a spool with oppositely reacting surfaces thereon responsive to fluid pressure for urging it toward alternate positions, conduits connecting the source of hydraulic fluid with the valve and the valve with the actuator for supplying hydraulic fluid to one side and exhausting it from the other side of said actuator, upon shifting of said spool to one alternate position, and means responsive to an imbalance of said values for selectively admitting pneumatic fluid to one of said surfaces which is at a higher level than that admitted to the other of said surfaces so as to move said spool to one of its positions irrespective of the magnitude of the imbalance.

11. Apparatus of the character defined in claim 10, including means for producing first and second signals representing the values of said well characteristics, and means for admitting said pneumatic fluid includes means for receiving and comparing said signals so as to determine the imbalance.

12. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there being a deviation, positive or negative, By which said pressure differential exceeds a predetermined value thereof, apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke for regulating the outlet fluid pressure in response to signals, means for producing a first signal, means for producing a second signal which varies with well characteristics and cooperates with the first signal to cause the choke to increase or decrease the outlet fluid pressure automatically in response to said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, means for manually producing a third signal which overrides the first and second signals to selectively cause the choke to increase or decrease the outlet fluid pressure, and means for producing a fourth signal which represents the value of fluid pressure within the outlet and which overrides the first, second and third signals to cause the choke to decrease the outlet fluid pressure automatically in response to the value thereof exceeding a predetermined level.

13. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there being a deviation, positive or negative, by which said pressure differential exceeds a predetermined value thereof;

apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke for regulating the outlet fluid pressure in response to signals, means for producing a first signal, means for producing a second signal which varies with well characteristics and cooperates with the first signal to cause the choke to increase or decrease the outlet fluid pressure automatically in response to said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, means for manually producing a third signal which overrides the first and second signals to selectively cause the choke to increase or decrease the outlet fluid pressure, and means for producing a fourth signal which represents the rate of change of fluid pressure within the outlet and which overrides the first, second and third signals to cause the choke to decrease the outlet fluid pressure automatically in response to the rate of increase thereof exceeding a predetermined level.

14. For use in drilling a well into an earth formation containing fluid under pressure, wherein drilling fluid is circulated through a drill string extending into a wellbore and through the annulus therebetween, said string and annulus having upper ends, one of which is an inlet and the other an outlet, there being a pressure differential, positive or negative, by which the bottom hole pressure of the drilling fluid exceeds the formation fluid pressure, and there being a deviation, positive or negative, by which said pressure differential exceeds a predetermined value thereof;

apparatus for maintaining said pressure differential at the predetermined value thereof, comprising a choke for regulating the outlet fluid pressure in response to signals, means for producing a first signal, means for producing a second signal which varies with well characteristics and cooperates with the first signal to cause the choke to increase or decrease the outlet fluid pressure automatically in response to said deviation being respectively negative or positive, whereby the outlet pressure approaches a value at which said deviation is zero, and means for manually producing a third signal which overrides the first and second signals to selectively cause the choke to increase or decrease the outlet fluid pressure, means for producing a fourtH control signal which represents the value of fluid pressure within the outlet and which overrides the first, second and third signals to cause the choke to decrease the outlet fluid pressure automatically in response to the value thereof exceeding a predetermined level, and means for producing a fifth control signal which represents the rate of change of fluid pressure within the outlet and which overrides the first, second and third signals to cause the choke to decrease the outlet fluid pressure automatically in response to the rate of increase thereof exceeding a predetermined level.