Method and Apparatus for Maintaining Bottom Hole Pressure During Connections

Abstract

A system for use in the drilling of oil or gas wells in conjunction with a mud injection device, said mud injection device adapted to maintain fluid pressure control within the borehole of a well bore when operating a drillstring therethrough, the system comprising: a gas reservoir containing gas; adapted for injection to control borehole pressure; compression system fluidly connected to the gas reservoir and the borehole; a pressure regulation system operatively connected to the gas reservoir and the borehole and adapted to measure the pressure within the annulus and relay such to a computer; wherein, when a drilling operation is halted to add a new stand to the drillstring and the mud injection device is stopped, the gas is injected to maintain the borehole pressure within the annulus of the borehole at a near constant value.

Claims

1. A method to maintain fluid pressure control to a well bore during an operation involving the addition or removal of a stand to a drill-string, said method comprising the injection of a compressible gas to maintain a bottom hole fluid pressure near-constant during the operation.

2. The method according to claim 1 wherein the compressible gas is selected from the group consisting of: carbon dioxide, air and nitrogen.

3. The method according to claim 1 wherein the compressible gas is nitrogen.

4. The method according to claim 1, further comprising a ramp-schedule comprising a number of parameters obtained from a pressure monitoring system, said parameters required by an operator to maintain a near-constant bottom hole pressure during a managed pressure drilling connection.

5. The method according to claim 4 wherein the parameters comprise at least one of the following: drilling fluid weight, primary pump pressures, drilling fluid flow rates, drill string rate of penetration, drill string rotation rate, surface applied backpressure and sensor data transmitted by said bottom hole assembly.

6. The method according to claim 5, comprising the steps of: ramping down a pump injecting drilling mud down the borehole and adjusting the managed pressure drilling choke following a ramp schedule; and simultaneously, injecting said gas and following said ramp-schedule.

7. A system for use in the drilling of oil or gas wells in conjunction with a mud injection device, said mud injection device adapted to maintain fluid pressure control within a borehole of a well bore when operating a drillstring therethrough, the system comprising: a gas reservoir containing gas adapted for injection to control borehole pressure; a compression system fluidly connected to the gas reservoir and the borehole; a pressure regulation system operatively connected to the gas reservoir and the borehole and adapted to measure the pressure within the annulus wherein, when a drilling operation is halted to add a new stand to the drillstring and the mud injection device is stopped, the gas is injected to maintain the borehole pressure within the annulus of the borehole at a near constant value.

8. The system according to claim 7 further comprising a gas injector fluidly connected to the gas reservoir and the borehole.

9. A system for use in the drilling of oil or gas wells adapted to purge lines when a drilling rig is operating a drillstring, the system comprising: a gas reservoir containing gas adapted for injection to purge flow lines of gas released from a borehole where the drillstring is inserted; a compression system fluidly connected to the gas reservoir, the flow lines and the borehole; a pressure regulation system operatively connected to the gas reservoir and the borehole and adapted to measure the pressure within the annulus of the borehole; wherein, at any given time during a drilling operation, said gas adapted for injection gas can be injected through the lines to purge the latter of formation released gases.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0033] The invention may be more completely understood in consideration of the following description of various embodiments of the invention in connection with the accompanying figure, in which:

[0034] FIG. 1 is a schematic of a drilling set-up incorporating the device according to a preferred embodiment of the present invention.

[0035] FIG. 2 is a graph representing the process-time estimates for the apparatus and method, based on classical thermodynamics.

[0036] FIG. 3 is a schematic of a drilling set-up incorporating the device according to a preferred embodiment of the present invention.

[0037] FIG. 4 is a schematic of a drilling set-up incorporating the device according to a preferred embodiment of the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0038] According to a preferred embodiment, FIG. 1 depicts a schematic layout of a system for use in the drilling of oil or gas wells in conjunction with a mud injection device, said mud injection device adapted to maintain fluid pressure control within the borehole of a well bore when operating a drill string therethrough, the system comprising: [0039] a compression system fluidly connected to the gas reservoir and the borehole; [0040] a gas reservoir containing gas adapted for injection to control borehole pressure; [0041] a pressure regulation system operatively connected to the gas reservoir and the borehole and adapted to measure the pressure within the annulus and relay such to a computer;
wherein, when a drilling operation is halted to add a new stand to the drillstring and the mud injection device is stopped, the gas is injected to maintain the borehole pressure within the annulus of the borehole at a near constant value.

[0042] According to a preferred embodiment of the present invention, there is provided an apparatus involve the following elements:

[0043] a) Nitrogen reservoir equipped with a compression system. Commercially available units having the technical to fulfill the requirements of the method according to a preferred embodiment of the present invention are readily available.

[0044] b) Remotely operated pressure regulation system. According to a preferred embodiment, this can be a simple combination of electrical actuators and pressure regulators.

[0045] c) Drilling fluid tank, rated at the same operating pressure as the primary flowline. This tank serves as a reservoir that prevents the addition of nitrogen pumped into the active fluid system.

[0046] According to a preferred embodiment of the present invention, the system, as described previously and schematically depicted in FIG. 1, is capable of: [0047] 1. operating in a time frame suitable for a drilling connection; [0048] 2. operating safely in a Zone 1 environment. This applies to all components of this apparatus: nitrogen tanks and compression, sensors/transducers, PLC or data processing computer, electrical cables, hydraulic actuators and fittings; and [0049] 3. automating the process of manipulating the pressure in the primary flowline by means of: surface data acquisition; signal processing; operator input; pressure regulators; and remotely operated actuators.

[0050] FIG. 1 shows a drilling set-up incorporating the device according to a preferred embodiment of the present invention. There is a gas reservoir (not shown) equipped with a gas compressor (10) connected to a computer (14) via connection (32). A user may operate the computer via a human-machine interface (16). The computer (14) monitors the pressure from inside the wellbore with the use of a pressure sensor (24) connected to the computer via wire (30) and controls the volume of gas injected into the wellbore. There is a drilling fluid reservoir (12) connected via drilling fluid line (13) to a choke (18) and a valve (V2)(20) connecting the drilling fluid to the primary flow line (22). Reservoir (12) further comprises a line (15) leading to the choke. The line (15) is equipped with a valve (17) to allow bleeding off of the line. This operation is determined and implemented by the computer through an activation through line (28). Line (26) leads the fluid to a separator (not shown). When a drillstring is stopped to add a stand, the drilling mud injection is halted and the gas compressor (10) is put in operation to maintain the pressure within the wellbore to within an acceptable range. The compressibility of the gas used allows to absorb kicks and prevent blowouts without having to work within a very tight window of pressure comparatively to conventional systems described hereinabove. A second advantage of the system depicted is that it prevents the unwanted fracking of formations again because of the compressibility of the gas used. This has substantial advantages in comparison to conventional systems all the while providing a valuable safety element during the addition/removal of a stand.

[0051] FIG. 2 is a graphical depiction representing the process-time estimates for the apparatus according to the present invention as well as the method using said apparatus, based on classical thermodynamics. It depicts the correlation between the rate of injection of the gas used (nitrogen) and the time (in seconds) to pressure up.

[0052] FIG. 3 illustrates an alternative preferred embodiment where the gas compressor (10) is fluidly connected to the drilling fluid reservoir (12) and the nitrogen can be pumped directly into the flowline upstream (40) of the MPD manifold (34) and/or inside the drilling fluid reservoir (12). A pressure transducer is located on the primary flow line (22) after the drilling fluid injection point (42). Beyond the pressure transducer is located the managed pressure drilling unit (MPD manifold) (34) comprising various valves and chokes (including Choke 1 (44) and Choke 2 (46)). Both of chokes 1 and 2 (44 and 46) are fluidly connected the gas compressor (10) and the primary flow line (22). To the left of the MPD manifold (34) is the flow line (26) leading to a separator (36). There is preferably a flow meter (38) located along the line to provide information to the user as to the rate of flow of the fluid going to the separator. A number of valves are located throughout the set-up both within the MPD and along various lines in order to provide operational flexibility in maintaining and/or optimizing the various fluids' pressures and flows.

[0053] FIG. 4 illustrates yet another alternative preferred embodiment where the drilling fluid tank is removed and the nitrogen is pumped directly from the gas compressor (10) into the flowline (48) upstream of the choke manifold or into a line (50) leading directly to the primary flowline (22) prior to the latter connection to the MPD manifold. There is a pressure transducer (25) located on the primary flow line (22) after the compressed gas injection point (52). Beyond the pressure transducer is located the managed pressure drilling unit (MPD manifold) (34) comprising various valves and chokes (including Choke 1 (44) and Choke 2 (46)). Both of chokes 1 and 2 (44 and 46) are fluidly connected the gas compressor (10) and the primary flow line (22). To the left of the MPD manifold (34) is the flow line (26) leading to a separator (36). There is preferably a flow meter (38) located along the line to provide information to the user as to the rate of flow of the fluid going to the separator. In this embodiment, the gas compressor is linked directly to the primary flow line in the absence of a drilling fluid reservoir.

[0054] The embodiments described herein are to be understood to be exemplary and numerous modification and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the claims appended hereto, the invention may be practiced otherwise than as specifically disclosed herein.