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 a bottom hole fluid pressure control to a wellbore of a drilling rig that utilizes a drillstring and to facilitate adding a new drill stand, said method comprising: providing a gas reservoir equipped with a gas compressor connected to a computer via a connection wherein a user operates the computer via a human-machine interface and wherein the computer monitors pressure inside the wellbore with the use of a pressure sensor and further wherein the computer controls a volume of gas injected into the wellbore; providing a drilling fluid reservoir connected via a drilling fluid line to a managed pressure drilling choke and a valve connecting the drilling fluid to a primary flow line; injecting drilling mud in the wellbore by a mud injection device adapted to maintain fluid pressure control; providing a managed pressure drilling manifold with a flowline connected to said gas compressor; conducting drilling by the drilling rig; executing a ramp-schedule computation; halting drilling to add a new stand to the drillstring, wherein the mud injection device is stopped; injecting the compressible gas directly into the managed pressure drilling manifold from said flowline to maintain borehole pressure within the annulus of the wellbore at the desired constant pressure; in response to said executing step, ramping down pumping of the drilling mud by ramping down revolutions per minute (RPM) of the mud injection device and adjusting the managed pressure drilling (MPD) choke following the execution of the ramp-schedule computation; wherein injecting the compressible gas into the wellbore occurs following execution of the ramp-schedule to maintain the borehole pressure; wherein the gas compressor is activated simultaneously to inject gas from the gas reservoir following execution of the ramp-schedule; breaking connection of the drill rig to add a new drill stand and then adding the new drill stand to the drill rig; ramping up RPM of the mud injection device while adjusting the MPD choke and bleeding down the gas compressor; executing the ramp-schedule computation comprising parameters obtained from a pressure monitoring system, said parameters enabling an operator to maintain a constant desired bottom hole pressure during a managed pressure drilling connection; and wherein the parameters comprise consideration of at least one of: drilling fluid weight, drilling fluid flow rates, drill string rates of penetration and drill string rotation rate.
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.
Description
BRIEF DESCRIPTION OF THE FIGURES
(1) 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:
(2) FIG. 1 is a schematic of a drilling set-up incorporating the device according to a preferred embodiment of the present invention.
(3) FIG. 2 is a graph representing the process-time estimates for the apparatus and method, based on classical thermodynamics.
(4) FIG. 3 is a schematic of a drilling set-up incorporating the device according to a preferred embodiment of the present invention.
(5) 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
(6) 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: a compression system fluidly connected to the gas reservoir and the borehole; a gas reservoir containing gas adapted for injection to control borehole pressure; 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.
(7) According to a preferred embodiment of the present invention, there is provided an apparatus involve the following elements:
(8) 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.
(9) b) Remotely operated pressure regulation system. According to a preferred embodiment, this can be a simple combination of electrical actuators and pressure regulators.
(10) 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.
(11) According to a preferred embodiment of the present invention, the system, as described previously and schematically depicted in FIG. 1, is capable of: 1. operating in a time frame suitable for a drilling connection; 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 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.
(12) 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 (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.
(13) 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.
(14) 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.
(15) 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.
(16) 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.
