DEBRIS REMOVAL SYSTEM AND METHOD FOR PRESSURE CONTROLLED WELLBORE DRILLING AND INTERVENTION OPERATIONS

Abstract

A wellbore debris screening system used with controlled annulus pressure wellbore intervention and drilling operations includes a wellbore annulus seal configured to pressure isolate an annular space between a conduit inserted into the wellbore and the wellbore wall. A first screening device is coupled to an output of the annulus seal. second screening device is coupled to the output of the annulus seal. Valves are provided that are operable to selectively divert flow out of the annulus to the first and to the second screening sections.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Priority is claimed from U.S. Provisional Application No. 61/305,708 filed on Feb. 18, 2010.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to the field of wellbore drilling wherein a drilling fluid circulation system is closed. More specifically, the invention relates to devices for removing cuttings and debris from a well annulus when the annulus is pressure controlled and allowing cuttings size and shape inspections, either remotely or by automatically or manually removing samples from the system.

2. Background Art

Certain types of wellbore drilling and intervention operations are performed such that a pipe string, coiled tubing or drill string is inserted into the wellbore and wherein an annular space between the pipe string, coiled tubing or drill string is closed by an annular pressure control device such as a dynamic hydraulic seal, a rotating control head, rotating blowout preventer and the like.

During the drilling or intervention operations, fluid may be pumped through the pipe string, drill string or coiled tubing, enter the wellbore at the lower end of the string or tubing, and move up the annular space. In any drilling operation the normal parameters monitored to determine performance include the rate of penetration and rate and constituents of material returning up the annulus. This is true of both a hand drill and a deep drilling rig. In the case of drilling with an annular pressure control device such as those described above, however, the return fluid and any solids therein are circulated to a pressurized separation tank. It is often only very intermittently that the tank is opened and inspected for accumulation of debris.

There exists a need for a system to enable more frequent characterization of debris returning from a well being operated using an annular pressure control device.

SUMMARY OF THE INVENTION

A wellbore debris screening system according to one aspect of the invention used with controlled annulus pressure wellbore intervention and drilling operations includes a wellbore annulus seal configured to pressure isolate an annular space between a conduit inserted into the wellbore and the wellbore wall. A first screening device is coupled to an output of the annulus seal. A second screening device is coupled to the output of the annulus seal. Valves are provided that are operable to selectively divert flow out of the annulus to the first and to the second screening sections.

A method for collecting debris from a wellbore during wellbore intervention operations according to another aspect of the invention includes circulating fluid through the interior of a pipe disposed in the wellbore to conduct the intervention operations. The fluid is returned up an annular space between a wall of the wellbore and an exterior of the pipe. A fluid seal is maintained at the surface between the annular space and the pipe. The fluid is discharged from below the fluid seal to at least two parallel-connected, pressure sealed screening devices, the discharging performed so that the fluid flows only through a first one of the at least two screening devices. When the first one of the screening devices is determined to be full, flow is diverted to a second one of the at least two screening devices.

Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a system according to the invention.

DETAILED DESCRIPTION

1. General Principles of a Debris Catcher According to the Invention

This invention combines one or more pressurized debris catchers that are connected upstream of a return separator pressure tank. The debris catcher can have one or more screen sections that are selectably inserted into the flow path to catch debris. The screen sections can be individually hydraulically isolated while the flow of drill debris and fluid from the well continues. The concept is that periodically the screens are hydraulically isolated and emptied, and the debris is weighed and characterized for size and shape. The rate at which the debris fills the catcher can also be recorded. In addition, pressure differential monitors and other sensors can measure the pressure drop across each screen section, providing data on the size of the cuttings generated or the particles unloaded from the well. This sensing can be remote and coupled with an automatic dump/flush of the screen, eliminating need to manually disassemble the apparatus for cleaning and debris removal.

The debris catcher facilitates the optimization of drilling parameters such as weight on bit, flow rate, mud motor differential pressure, and fluid return rate (in the case of a circulating or flowing well condition). Changes in drilling parameters can be correlated to changes in the return debris. Feedback can be used to optimize the drilling process.

The pressurized debris catcher can also include pressure sensors or gauges upstream and downstream of each screen section so that fill up or plugging of the screen section can be identified if pressure drop across the screen increases.

2. An Example Debris Catcher Structure.

Referring to FIG. 1, an example of a debris catcher according to the invention will be explained. A wellbore 10 may be subject to operations such as drilling, workover, recompletion of other intervention. In the present example, the well drilling or intervention may be performed by a coiled tubing unit 12. As explained in the Background section herein, the operations in the wellbore 10 may also be performed, without limitation, by a workover pipe string, a drill string or any other tubular device that can be extended into the wellbore 10 for the purpose of operating in the wellbore 10, and has the capability of having fluid pumped through an internal passage 11 therethrough. An annular space 13 between the coiled tubing 12 or other pipe may be sealed at or near the surface by a rotating diverter, rotating control head, rotating blowout preventer or similar device 14 that seals the upper end of the wellbore annulus 13 while enabling movement of the intervention pipe (e.g., coiled tubing 12) therethrough.

During the wellbore intervention operation, fluid may be pumped through the internal passage 11 in the intervention pipe (e.g., coiled tubing 12) and returned to the surface in the annulus 13. The annular sealing device 14 has a discharge line 16. In the present example the discharge line 16 may be coupled to a debris screening device 17 according to the invention. The debris screening device 17 may include an inlet control valve 20 that can be closed to stop all flow to the device 17. The debris screening device 17 may be divided into three operating sections 1, 2, 3. The first operating section 1 may be coupled to the discharge line 16 by an inlet manifold 24 that divides flow from the discharge line 16 to the three operating sections 1, 2, 3. The first operating section 1 may include a first screening device 18, and may be controllably sealed at its input end and output end by valves V1, V2, V6, V7. Correspondingly, the second operating section 2 may include a second, similarly configured screening device 22, controllably sealed at its input and output ends by valves V3, V4, V8 and V9, respectively. The purposes for including double valves on each of the input and output of the first screening device 18 and the second screening device 22 is to enable maintaining the contents of each screening device at a selected pressure while disassembling the respective screening device from the debris catcher 17, and to enable safe bleed off of pressure from the respective screening section when removed from the debris catcher 17 prior to opening the screening section.

The third operating section 3 may be optionally provided for safety purposes and include a valve V5 that can be opened in the case the screening sections 18, 22 both become inoperable for any reason or the pipe operation is in a section of the well where cuttings collection and analysis is not necessary. Alternatively, valve V5 in operating section 3 may be omitted or may be normally open, and a burst disk 32 may be included in section 3 so that in the event the screening pressure becomes excessive, the burst disk 32 will rupture, enabling fluid passage through section 3 before pressure caused failure of either screening section 18, 22 may occur. The burst disk 32 could also be included in either or both screening sections.

The flow out of the three operating sections 1, 2, 3 is coupled by an output manifold 26. The output manifold 26 may be coupled to a fixed, manually operable or automatically operable choke 28, that restricts flow out the annulus 13 to a maintain a selected pressure therein. Output of the choke 28 is coupled to a pressure tank 30 of any type known in the art.

During ordinary operation of the system shown in FIG. 1, flow may be conducted through the first screening device 18 and stopped from the second screening device by suitable operation of the valves V1, V2, V6, V7. Pressure at the input and output of the first screening device 18 may be measured by suitably disposed pressure sensors or gauges P1, P2. After a selected time, or when the differential pressure across the first screening device 18 (e.g., as measured by gauges P1, P2) reaches a selected threshold, the valves V1, V2, V6, V7 may be operated to divert flow from the discharge line 16 to the second screening section 22 and to isolate the first screening section 18. The first screening section 18 may then be opened, and debris, cuttings, etc. may be removed therefrom and characterized as appropriate for the well intervention operation being performed.

After a selected time, or when the differential pressure, e.g., as measured by gauges P3 and P4, across the second screening section 22 reaches a selected threshold, the valves V3, V4, V8, V9 may be operated to isolate the second screening section 22, and return flow to the first screening section 18 by opening valves V1, V2, V6, V7.

If any hazards or problems occur during operating the first 18 and second 22 screening sections, flow from the annulus 13 may be diverted through the third operating section 3, and the screening sections 18, 22, may be isolated by suitable operation of the valves and opening valve V5.

In the present example, suitable sensors S1 and S2 may be provided for the respective screening sections 18, 22 to enable characterization of the debris trapped in the respective screening section without the need to open the screening section. Such sensors may include, without limitation, induction resistivity, nuclear magnetic resonance relaxation time distribution, acoustic velocity, density and neutron porosity. Such sensors are intended to enable characterization of the debris according to particle shape and size, particle composition and analysis of fluids flowing through the screening sections (e.g., gas, oil, water and relative fractions thereof).

Each screening section may include screens having at least two or variable mesh sizes to enable capture larger amounts of various size particles between screening section cleanings.

In some examples, the screening sections may be configured to dump cuttings automatically. The depth of the wellbore may be recorded automatically at the time of dumping to enable making a record of depth with respect to cuttings dump.

A wellbore discharge screening device according to the invention may enable more frequent characterization of the debris leaving a wellbore during controlled annulus pressure drilling or intervention operations than using only a pressure tank as is known in the art prior to the present invention.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

1. A wellbore debris screening system used with controlled annulus pressure wellbore intervention and drilling operations, comprising:

a wellbore annulus seal configured to pressure isolate an annular space between a conduit inserted into the wellbore and the wellbore wall;

a first screening section coupled to an output of the annulus seal;

a second screening device coupled to the output of the annulus seal; and

valves operable to selectively divert flow out of the annulus to the first and to the second screening sections.

2. The system of claim 1 further comprising pressure sensors in hydraulic communication with an intake side and an outlet side of each of the first and second screening sections.

3. The system of claim 1 further comprising a bypass line coupled between the output of the annulus seal and an outlet manifold coupled to outlet side of the first and second screening sections.

4. The system of claim 1 further comprising a controllable orifice choke disposed between the outlet manifold and a pressure tank, the choke operable to maintain a selected pressure in the wellbore annulus.

5. The system of claim 1 wherein each screening section includes valves at its inlet and outlet to enable removal from the system while maintaining fluid pressure within the screening section.

6. The system of claim 1 further comprising sensors associated with each screening section, the sensors selected and arranged to enable at least one of characterization of debris particle size, debris particle shape, presence of water, oil, gas and fractional amounts thereof.

7. The system of claim 3 further comprising a pressure actuated burst disk disposed in either of the screening sections or the bypass line.

8. The system of claim 1 wherein screens in each screening section comprise at least two mesh sizes.

9. A method for collecting debris from a wellbore during wellbore intervention operations, comprising:

circulating fluid through the interior of a pipe disposed in the wellbore to conduct the intervention operations;

returning the fluid up an annular space between a wall of the wellbore and an exterior of the pipe;

maintaining a fluid seal at the surface between the annular space and the pipe;

discharging the fluid from below the fluid seal to at least two parallel-connected, pressure sealed screening devices, the discharging performed so that the fluid flows only through a first one of the at least two screening devices; and

when the first one of the screening devices is determined to be full, diverting flow to a second one of the at least two screening devices.

10. The method of claim 9 wherein determining when the first one of the screening devices is full comprises measuring a pressure drop between and inlet and outlet of the first one of the screening devices.

11. The method of claim 9 further comprising hydraulically isolating the first one of the screening devices and removing it from any hydraulic circuit including the at least two screening devices.

12. The method of claim 9 further comprising bypassing flow of fluid around the at least two screening devices if at least one of the screening devices become clogged and debris samples are not needed at selected times.

13. The method of claim 9 further comprising sensing selected parameters of the fluid moving through the at least to screening devices to determine at least one of debris particle size, debris particle shape, and fluid composition.

14. The method of claim 9 further comprising automatically dumping one of the at least two screening sections at selected times and recording a depth of the pipe in the wellbore at the selected times.