METHOD AND APPARATUS FOR CONTROLLING BOTTOM HOLE PRESSURE IN A SUBTERRANEAN FORMATION DURING RIG PUMP OPERATION

• US 20100288507A1
• Filed: 10/23/2007
• Published: 11/18/2010
• Est. Priority Date: 10/23/2006
• Status: Active Grant

• Current Assignee: M-I LLC (Schlumberger NV), Smith International Incorporated (Schlumberger NV)
• Original Assignee: M-I LLC (Schlumberger NV)
• Inventors: May, James, Duhe, Jason
• Granted Patent: US 8,490,719 B2
• Time in Patent Office: Days
• US Class Current: 166/370
• 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

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 off pressurized fluid from the annulus, separating solids from the fluid, and directing the fluid back 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 calculated set point backpressure, and a processor for controlling the adjustable choke and backpressure pump is also disclosed.

Claims

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

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 off pressurized fluid from the annulus;

separating solids from the fluid; and

directing the fluid back to the reservoir.

2. The method of claim 1 further comprising:

determining the amount of fluid lost or gained in the wellbore.

3. The method of claim 2 wherein determining the amount of fluid lost or gained in the wellbore further comprises:

measuring the flow rate of fluid from the reservoir to the wellbore; and

measuring the flow rate of the diverted fluid.

4. The method of claim 1 further comprising:

inputting fixed parameters related to the wellbore into a processor;

measuring a flow rate of fluid provided from the reservoir to the wellbore;

inputting the measured flow rate of fluid provided from the reservoir to the wellbore into the processor;

measuring a flow rate of fluid diverted from the wellbore to the controllable choke;

inputting the measured flow rate of fluid diverted from the wellbore to the controllable choke into the processor;

measuring a downhole pressure;

inputting the measured downhole pressure into the processor;

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

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:

pumping fluid from the reservoir through a backpressure line to apply back pressure to the annulus.

7. The method of claim 1 further comprising:

measuring a drill pipe pressure;

inputting the drill pipe pressure into a processor;

calculating a target drill pipe pressure;

transmitting the target drill pipe pressure to a PID controller;

generating an hydraulic set point pressure;

applying the hydraulic set point pressure to the choke;

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

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

8. An apparatus for maintaining pressure in a wellbore during drilling operations, wherein the wellbore has casing set and cemented into place, the apparatus comprising:

a reservoir containing fluid for the wellbore;

a drill string in fluid communication with the reservoir, wherein an annulus is defined between the wellbore and the drillstring;

a pressure transducer in the drill string to measure pressure in the annulus;

a rotating control device isolating pressure in the annulus and communicating fluid from the reservoir to the drill string and diverting fluid and solids from the annulus;

an adjustable choke in fluid communication with the rotating control device controllably bleeding off pressurized fluid from the annulus;

solids control equipment receiving fluid and solids from the adjustable choke and removing the solids from the fluid;

wherein the fluid from the solids control equipment is directed to the reservoir;

a processor receiving the measured pressure from the pressure transducer and calculating a set point backpressure; and

a backpressure pump in fluid communication with the reservoir and applying a backpressure between the rotating control device and the automatic choke based on the calculated set point backpressure.

9. The apparatus of claim 8, further comprising

a flow meter between the reservoir and the drill string measuring a first flow rate therethrough;

a second flow meter between the annulus and the choke measuring a second flow rate therethrough; and

wherein the processor receives the first and second flow rates and determines an amount of fluid lost or gained in the wellbore.

10. The apparatus of claim 8, further comprising:

a PID controller receiving communication from the processor;

wherein the PID controller generates an hydraulic set point pressure and applies it to the choke;

wherein the choke automatically adjusts in response to the hydraulic set point pressure to apply a casing pressure to the wellbore.

11. The apparatus of claim 8, further comprising:

a programmable logic controller for controlling the backpressure pump;

wherein the processor calculates a set point downhole pressure and transmits the set point downhole pressure to the programmable logic controller; and

wherein the backpressure pump is controlled by the programmable logic controller based on the set point downhole pressure.

12. The apparatus of claim 8, wherein the backpressure pump provides up to approximately 2200 psi of backpressure.

13. The apparatus of claim 8, further comprising:

a choke manifold;

a back up choke on the choke manifold;

wherein the choke and the back up choke are selectively in fluid communication with the rotating control device controllably bleeding off pressurized fluid from the annulus.