Method and apparatus for controlling bottom hole pressure in a subterranean formation during rig pump operation

• US 9,435,162 B2
• Filed: 04/16/2013
• Issued: 09/06/2016
• Est. Priority Date: 10/23/2006
• Status: Active Grant

• Current Assignee: M-I LLC (SLB), Smith International Incorporated (SLB)
• Original Assignee: M-I LLC (SLB), Smith International Incorporated (SLB)
• Inventors: Duhe, Jason, May, James
• Primary Examiner(s): HUTCHINS, CATHLEEN R
• Application Number:
  US13/863,883
• Publication Number:
  US 20140305705A1
• Time in Patent Office: 1,239 Days
• US Class Current: 1/1
• 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
• CPC Class Codes: E21B 44/00 Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
• CPC Class Codes: E21B 47/06 Measuring temperature or pressure

Abstract

A method for maintaining pressure in a wellbore during drilling operations is disclosed. The method includes the steps of providing fluid from a reservoir through a drill string, circulating the fluid from the drill string to an annulus between the drill string and the wellbore, isolating pressure in the annulus, measuring pressure in the annulus, calculating a set point backpressure, applying back pressure to the annulus based on the set point back pressure, diverting fluid from the annulus to a controllable choke, controllably bleeding pressurized fluid from the annulus, separating solids from the fluid, and directing the fluid to the reservoir. An apparatus for maintaining pressure in a wellbore during drilling operations that includes an adjustable choke for controllably bleeding off pressurized fluid from the wellbore annulus. A backpressure pump for applying a set point backpressure, and a processor for controlling the adjustable choke and backpressure pump are also disclosed.

Claims

1. A method for maintaining pressure in a wellbore during drilling operations comprising:

feeding a drill fluid through a reservoir conduit from a reservoir;

diverting the drill fluid from the reservoir conduit to a first drill fluid line and through a drill string;

circulating the drill, fluid through, the drill string to an annulus between the drill string and the wellbore wherein the drill fluid exits the annulus as a return fluid;

directing the drill fluid from the reservoir conduit to a second drill fluid line and through a backpressure pump;

mixing the return fluid with the drill fluid fed through the backpressure pump from the reservoir conduit to form a mixed fluid; and

feeding the mixed fluid to a controllable choke for applying backpressure to the annulus.

2. The method of claim 1 further comprising:

measuring the volume of the drill fluid through the backpressure pump;

determining an amount of fluid lost or gained in the well bore based on a measured flow rate of the drill fluid in the first drill fluid line, a measured flow rate of the return fluid, and the measured volume of the drill fluid fed through the backpressure pump.

3. The method of claim 1 further comprising:

isolating pressure in the annulus;

measuring pressure in the annulus;

calculating a set point back pressure; and

applying back pressure to the annulus based on the set point back pressure.

4. The method of claim 1 further comprising:

inputting fixed parameters related to the wellbore into a processor;

inputting a measured flow rate of the drill fluid into the processor;

determining a flow rate of the drill fluid fed through the backpressure pump;

inputting a measured flow rate of the return fluid into the processor;

measuring a downhole pressure;

inputting the downhole pressure into the processor;

calculating a set point down link pressure from the fixed parameters, measured and determined flow rates and measured downhole pressure; and

adjusting the backpressure applied to the annulus based on the calculated set point downhole pressure.

5. The method of claim 1 further comprising:

adjusting the backpressure applied to the annulus.

6. The method of claim 1 further comprising:

measuring a drill pipe pressure;

inputting t he drill pipe pressure into a processor;

calculating a target drill pipe pressure;

transmitting the target drill pipe pressure to a proportional-integral-differential controller;

generating an hydraulic set point pressure;

applying the hydraulic set point pressure;

wherein the choke automatically adjusts in response to the hydraulic set point pressure to apply a easing pressure to the wellbore;

wherein the casing pressure in the wellbore affects the drill pipe pressure.

7. The method of claim 1, wherein the mixed fluid comprises solids from the wellbore returned with the return fluid, and wherein the method further comprises;

separating the solids from the mixed fluid; and

directing the mixed fluid back to the reservoir.

8. A system for maintaining pressure in a wellbore during drilling operations comprising;

a reservoir conduit extending from, a reservoir and having a controllable variable valve provided therein, wherein drill fluid flows from the reservoir through the reservoir conduit and the controllable variable valve to a drill string disposed in the wellbore and further flows from the drill string into an annulus defined between the wellbore and the drill string, wherein the drill fluid returns from the annulus as return fluid;

a return conduit through which the return fluid flows from the annulus toward a backpressure control device;

backpressure pump in fluid communication with the reservoir conduit via the controllable variable valve, the backpressure pump pumping the drill fluid from the reservoir to the return conduit at a location along the return conduit upstream of the backpressure control device;

and a controller configured to determine a backpressure set point based on one or more measurements taken from the system.

9. The system of claim 8, wherein the controller is configured to determine a property of the return fluid diverted from the annulus based on the one or more measurements taken from the system.

10. The system of claim 8, wherein the controller determines the backpressure set point using feedforward logic control.

11. The system of claim 8, further comprising:

a sensor for measuring drill pipe pressure;

a sensor for measuring easing pressure; and

a sensor for measuring downhole pressure.

12. The system of claim 8, wherein the controller is configured to determine an amount of fluid lost or gained in the wellbore based on a measured flow rate of the drill fluid flowing to the drill string, a measured flow rate of the return fluid flowing through the return conduit, and a flow rate of the fluid pumped by the backpressure pump.

13. A system for maintaining pressure in a wellbore during drilling operations comprising:

a reservoir conduit extending from a reservoir and having a three-way fluid junction provided therein;

a first drill fluid line extending from the three-way fluid junction to a drill string disposed in the wellbore;

wherein drill fluid flows from the reservoir through the reservoir conduit, the three-way fluid junction, and the first drill fluid line to the drill string and further flows from the drill string into an annulus defined between the wellbore and the drill string, wherein the drill fluid returns from the annulus as return fluid;

a return conduit through which the return fluid flows from the annulus toward a backpressure control device;

a second drill fluid line extending from the three-way fluid junction to a backpressure pump, the backpressure pump pumping the drill fluid from the reservoir conduit to the return conduit at a location along the return conduit upstream of the backpressure control device; and

a controller configured to determine a backpressure set point based on one or more measurements taken from the system.

14. The method of claim 13, wherein a first variable flow restricting device is provided in the first drill fluid line between the three-way fluid junction and the drill string, and wherein a second variable flow restricting device is provided in the second drill fluid line between the three-way fluid junction and the backpressure pump.