RU2788367C2 - Method for pressure control at bottom of wellbore - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: group of inventions relates to the oil and gas industry, in particular to adjustment of bottom pressure. For implementation of a method for control of pressure of well fluid in a wellbore, during a drilling operation with controllable pressure, injection of a drilling mud into the specified well is stopped. Compressible fluid is injected into an upper part of the specified well, downstream from a fitting located on a collector of a system for drilling with controllable pressure. A volume of injected compressible fluid is monitored for control of pressure in the specified well. Compressible gas is injected between the collector and the wellbore. A method for buffering pressure of well fluid in a wellbore during a drilling operation with controllable pressure is claimed. The system for use in drilling of oil or gas wells contains a device for injecting drilling mud, made with the possibility of maintenance of control of fluid pressure in the wellbore during operation of a drill string in it. A compression system is connected via fluid to a gas reservoir and a well. A pressure adjustment system is functionally connected to the gas reservoir and the well and is made with the possibility of measurement of pressure in an annular space. The system is made with the possibility of injection of gas into an upper part of the wellbore for maintenance of pressure in the well in the annular space of the wellbore, when stopping the drilling operation for addition of a new plug to the drill string and stopping a device for injection of the drilling mud. A system for use in drilling of oil or gas wells is claimed, made with the possibility of purification of lines, when a drilling installation operates with a drill string.

EFFECT: absorption of pressure impacts, prevention of emissions and formation of cracks in reservoirs.

10 cl, 4 dwg

Description

FIELD OF TECHNOLOGY

Apparatus and method for adjusting bottom hole pressure to near constant levels while making connections and/or maintaining constant back pressure on the surface, more specifically using managed pressure drilling (MPD) when the pumps are stopped.

BACKGROUND OF THE INVENTION

When drilling oil and gas wells, there are geological formations that have a narrower tolerance for bottom hole pressure changes. A well-known solution to this problem is the so-called Managed Pressure Drilling (MPD). In this drilling method, the annular space is sealed off from the atmosphere by means of a rotating deflecting preventer (RCD, Rotating Control Device). The RCD is a pressure control device used in the drilling process to create a seal around the drill string as it rotates. The RCD is designed to contain hydrocarbons or other well fluids and prevent their release to the atmosphere. The RCD diverts the well fluid to a manifold fitted with a special choke that provides downhole pressure control. Just before breaking the connection to add a new stand, the pumps slow down. At the same time, the dynamic component of the bottomhole pressure drops and needs to be compensated to keep the bottomhole pressure close to constant.

In the oil and gas industry, ensuring the safety of workers is paramount, and an issue that can compromise the safety of workers on a drilling rig is known as "blowout". When an abnormally high formation pressure zone is encountered during drilling and the pressure exceeds the hydrostatic pressure exerted by the drilling fluid, and the formation has sufficient permeability to allow fluid flow, the formation fluid will move into the wellbore and displace the drilling fluid. Such a phenomenon is called a "hit"; and if not controlled, it will result in a "blowout", which is an uncontrolled release of crude oil and/or natural gas from an oil or gas well following a failure of pressure control systems.

The traditional solution is to have a choke in the manifold connecting to the well annulus below the blowout preventer, which allows the choke to set and maintain back pressure on the drilling fluid deflected through the manifold when the blowout preventer (BOP) is deactivated. The back pressure, together with the hydrostatic pressure of the drilling fluid contained in the well, allows pressurized fluids to be retained in the formations through which the wellbore passes. The aforementioned choke is preferably adjustable so that in the event of formation fluid overpressure, also referred to as a blowout, it can be adjusted to maintain a predetermined pressure drop between the bottomhole pressure of the drilling fluid and the pressure generated by the formation fluid. It is very important to be able to retain the wellbore fluid, as well as to avoid excessive back pressure that could damage the drill string, casing, or formation.

As noted above, devices used in the art include back pressure pumps connected to a choke that pump drilling fluid down the wellbore to maintain a constant bottom hole pressure while the stand is added to the drill string. This allows for a plug to be added, but requires special vigilance, as excess drilling fluid can cause a sudden increase in bottomhole pressure and lead to formation fractures. This, in turn, increases the pressure in the well and creates open zones along the wellbore. In the case where insufficient pressure is used, there is a high possibility of a blowout in the well, which will require the well to be killed through the rig manifold and result in a well shut-in for several hours. Shutting down a well can result in a loss of up to $10,000 an hour in revenue. Equipment failure or software failure for a few seconds can lead to an increase in pressure, which ultimately leads to this undesirable fracturing situation.

US Pat. No. 3,552,502A discloses a method and apparatus for controlling oil and gas wells that does not rely on shutting down a circulation pump and shutting down the well. This is said to be done by means of monitoring the drillstring pressure, the volume of the drilling fluid and the weight of the drilling fluid pumped into the well, and controlling the adjustable choke with these data. The system calculates the required mass of drilling fluid to kill the well and controls the adjustable choke during the entire pumping period required to kill the well and to ensure that continuous circulation of the drilling fluid is maintained while calculating the stop pressure of the drill string and calculating the mass of the drilling fluid. CA 2477242 and CA 2516277 describe a closed loop positive differential pressure drilling system configured to vary the positive differential pressure. It is stated that data on the wellbore, drilling rig and drilling fluid are used to predict the pressure in the well. The predicted bottom hole pressure is then compared to the desired bottom hole pressure and the pressure difference is used to control the back pressure system. It is also claimed that the use of backpressure to increase pressure in the annulus is more sensitive to sudden changes in formation pore pressure.

CA 2667199 describes a method of maintaining pressure in a wellbore during drilling. The method is said to include the steps of pumping fluid from the formation through the drill string, circulating fluid from the drill string into the annulus between the drill string and the wellbore, isolating the pressure in the annulus, measuring the pressure in the annulus, calculating a predetermined backpressure, supplying backpressure to annulus based on a predetermined backpressure, diverting fluid from the annulus to a controllable choke, controlled removal of pressurized fluid from the annulus, separating solids from the fluid, and directing the fluid back into the formation.

Despite the current state of the art, there is still a need for a stable and reliable system for controlling bottomhole pressure in a wellbore that does not rely on a back pressure pump and mud injection during the addition or removal of a stand on the drill string.

DISCLOSURE OF THE INVENTION

In accordance with an aspect of the present invention, a compressible gas is injected to control downhole pressure during operations involving the removal or addition of a stand to the drill string.

Nitrogen is an inert gas used for various functions in the oil and gas industry. For both onshore and offshore applications, nitrogen applications include stimulation, well injection and pressure testing, enhanced oil recovery (EOR), reservoir pressure maintenance, nitrogen injection, and inert gas lift. In addition, nitrogen can be used to prevent the ignition of combustible gases and to protect pipes from corrosion in the well. Used to support drilling operations, nitrogen finds a variety of uses, including the supply of inert gas to flare gas, and the cleaning and testing of pressurized systems. Nitrogen can also be supplied for engine starters, controls, dry bulk handling systems and lifting systems. By providing a dry air supply, nitrogen can help extend the life of some systems as well as prevent them from breaking down. During workover and well completion operations, nitrogen allows well fluids to be displaced to initiate flow and clean wells due to its low density and high pressure. In addition, nitrogen has been found to be useful for maintaining pressure in formations that are either free of hydrocarbons or naturally depressurized. Because nitrogen is immiscible with oil and water, a nitrogen injection or nitrogen injection program can be used to move hydrocarbon cavities from an injection well to a production well.

In accordance with an aspect of the present invention, there is provided a method of providing back pressure in a wellbore during a stand-in operation, the method comprising injecting a compressible gas into the wellbore to control near-constant bottom hole pressure while the stand is added. Preferably the gas is selected from the group consisting of: carbon dioxide, air and nitrogen. Preferably the gas is nitrogen. When the rig is ready to connect, the engineer calculates a ramp-schedule (SCH) prior to connection. The ramp chart includes all parameters required by the operator to control bottom hole pressure close to a constant level during the MPD connection process.

According to a preferred embodiment of the present invention, the method includes the steps of:

- reducing the speed and adjusting the MPD nozzle in accordance with the linear change schedule;

- slowing down the pumps and adjusting the MPD nozzle according to the ramp schedule;

- simultaneously turning on the gas compressor to inject nitrogen from the reservoir into the wellbore and performing a ramping schedule to control the pressure in the well close to a constant level.

The downhole pressure build up/down is a coordinated action between the rig pumps, the MPD choke, the surface RPM and the gas compressor. At this point, the surface back pressure (SBP) is set and the rig is ready to break the connection and add a new candle. After connecting a new candle, the steps of the ramp graph are performed in reverse order. This means increasing the load of the drilling rig pumps, the speed, while adjusting the MPD nozzle and bleeding the pressure of the gas compressor device in a coordinated mode.

In accordance with an aspect of the present invention, there is provided a method for controlling the pressure of a wellbore fluid in a wellbore during a MPD operation, the method comprising:

- the stage of interrupting the injection of drilling fluid into the specified well;

- the step of injecting a compressible fluid into the upper part of said well, downstream of a choke located on the manifold of the MPD system;

- the step of monitoring the volume of injected compressible fluid to control pressure in said well;

wherein the compressible gas is injected between the reservoir and the wellbore.

In accordance with an aspect of the present invention, there is provided a method for buffering wellbore fluid pressure in a wellbore during a managed pressure drilling operation, said method comprising:

- the stage of interrupting the injection of drilling fluid into the specified well;

- the step of injecting a compressible fluid into the upper part of said well, downstream of a choke located on the manifold of the MPD system;

- the step of monitoring the volume of injected compressible fluid to control pressure in said well;

wherein the compressible gas is injected between the reservoir and the wellbore. Preferably the gas is selected from the group consisting of: carbon dioxide, air, nitrogen, and combinations thereof. More preferably, the compressed gas is nitrogen.

Preferably, the method further includes a ramp chart comprising a number of parameters obtained from the pressure monitoring system, said parameters being required by the operator to maintain the bottomhole pressure close to a constant level during the MPD connection process. Preferably, the parameters include at least one of the following: mud weight, main pump pressures, mud flow rates, ROP, drill string RPM, backpressure applied to the surface, and sensor data transmitted by said bottomhole equipment. . The method also preferably includes the steps of: depressurizing a pump that injects drilling fluid into the wellbore and adjusting the MPD choke according to the ramping schedule; and simultaneously injecting said gas and performing said ramp schedule.

In accordance with an aspect of the present invention, there is provided a system for use in drilling oil or gas wells in conjunction with a mud injection device, wherein said mud injection device is configured to maintain fluid pressure control in the wellbore while the drill string is operating therein, wherein system contains:

- a gas reservoir containing a gas suitable for injection, to control the pressure in the well;

a compression system in fluid communication with the gas reservoir and the well;

- a pressure control system operatively associated with the gas reservoir and the well, and configured to measure the pressure in the annulus, in which when the drilling operation is stopped to add a new stand to the drill string and the mud injection device is stopped, gas is injected into the upper part of the wellbore wells to maintain the pressure in the well in the annulus of the wellbore at a level close to constant. Preferably, the system further comprises a gas injection well in fluid communication with the gas reservoir and the well.

According to an aspect of the present invention, there is provided a system for use in drilling oil or gas wells, configured to clean lines while the drilling rig is operating with a drill string, the system comprising:

- a gas reservoir containing a gas suitable for injection to clean the bypass lines from the gas released from the well in which the drill string is installed;

a compression system in fluid communication with the gas reservoir, flow lines and well;

- a pressure control system operatively associated with the gas reservoir and the well and configured to measure pressure in the annulus of the well;

moreover, at any given time during the drilling operation, it is possible to inject said gas suitable for injection through the lines for cleaning the latter from gases released in the formation.

In accordance with another aspect of the present invention, there is provided a method for controlling fluid pressure in a wellbore during an operation involving adding or removing a stand to a drill string, said method comprising injecting compressible gas to maintain bottomhole pressure close to a constant level during the operation. Preferably the compressed gas is selected from the group consisting of: carbon dioxide, air and nitrogen. More preferably, the compressed gas is nitrogen.

According to a preferred embodiment of the present invention, the method further includes a ramp chart containing a number of parameters obtained from the pressure monitoring system, these parameters being required by the operator to maintain the bottom hole pressure close to a constant level during the MPD connection process. Preferably, the parameters include at least one of the following: mud weight, main pump pressures, mud flow rates, ROP, drill string RPM, backpressure applied to the surface, and sensor data transmitted by said bottom hole equipment. columns.

Preferably, the method may also include the following steps:

a) depressurizing the mud pump down the wellbore and operating the MPD choke in accordance with the ramping schedule, and

b) simultaneously, injection of said gas into said well;

c) wellbore pressure monitoring, and

d) following the specified ramp schedule.

In accordance with another aspect of the present invention, there is provided a system for use in drilling oil or gas wells in conjunction with a drilling fluid injection device, said drilling fluid injection device being configured to maintain fluid pressure control in the wellbore while the drill string is operating in it, when This system contains:

a gas reservoir containing a gas suitable for injection to control the pressure in the well;

a compression system in fluid communication with the gas reservoir and the well; a pressure control system operatively associated with the gas reservoir and the well, and configured to measure pressure in the annulus, wherein gas is injected to maintain pressure in the well when the drilling operation is stopped to add a new stand to the drill string and the mud injection device is stopped in the annulus of the wellbore at a level close to constant.

Preferably, the system further comprises a gas injection well in fluid communication with the gas reservoir and the well.

According to another aspect of the present invention, there is provided a system for use in drilling oil or gas wells, configured to purge lines while the drilling rig is operating with a drill string, the system comprising: a gas reservoir containing gas suitable for injection to purge gas from the lines released from the well in which the drill string is installed;

a compression system in fluid communication with the gas reservoir, lines, and well;

a pressure control system functionally associated with the gas reservoir and the well, and configured to measure the pressure in the annular space, while at any given time during the drilling operation, it is possible to inject gas through the lines to clean the latter from gases released from the formation.

BRIEF DESCRIPTION OF GRAPHICS

The present invention may be more fully understood by considering the following description of various embodiments of the invention in connection with the accompanying figure, in which:

In FIG. 1 schematically shows a drilling rig comprising a device in accordance with a preferred embodiment of the present invention;

In FIG. 2 is a graph representing process-time estimates for an apparatus and method based on classical thermodynamics;

In FIG. 3 schematically shows a drilling rig incorporating a device in accordance with a preferred embodiment of the present invention;

In FIG. 4 schematically shows a drilling rig incorporating a device in accordance with a preferred embodiment of the present invention.

IMPLEMENTATION OF THE INVENTION

In accordance with a preferred embodiment of the present invention, FIG. 1 depicts a system for use in drilling oil or gas wells in conjunction with a mud injection device, said mud injection device being configured to maintain fluid pressure control in the wellbore while the drill string is operating in it, the system comprising: a compression system connected in fluid medium with the gas reservoir and the well; a gas reservoir containing a gas suitable for injection to control the pressure in the well; a pressure control system operatively associated with the gas reservoir and the well, and configured to measure pressure in the annulus and transmit the measurement data to a computer; wherein, when the drilling operation is stopped to add a new stand to the drill string and the mud injection device is stopped, gas is injected to maintain the wellbore pressure in the wellbore annulus at a nearly constant level.

According to a preferred embodiment of the present invention, an apparatus is provided which comprises the following elements:

a) a nitrogen tank equipped with a compression system. Commercially available devices having the technical means to carry out the requirements of the method according to the preferred embodiment of the present invention are readily available;

b) remote controlled pressure control system. In a preferred embodiment, it may be a simple combination of electrical actuators and pressure regulators; and

c) a drilling fluid reservoir rated for the same operating pressure as the main return line. Said reservoir serves as a reservoir to prevent the addition of nitrogen injected into the working fluid system.

According to a preferred embodiment of the present invention, the system previously described and shown schematically in FIG. 1 is configured to:

1. work in the time range suitable for connection while drilling;

2. Safe operation in zone 1 environment. This applies to all components of said device: nitrogen and compression tanks, sensors/transducers, PLC (programmable logic controller) or data computer, electrical cables, hydraulic actuators and fittings; and

3. automation of the pressure control process in the main branch line by: collecting surface data; signal processing; operator data entry; pressure regulators; and remote controlled drives.

In FIG. 1 shows a drilling rig incorporating a device in accordance with 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 a connection (32). The user can control the computer through the interface (16) man-machine. The computer (14) monitors the pressure inside the wellbore using a pressure sensor (24) connected to the computer by a wire (30) and controls the volume of gas injected into the wellbore. There is a reservoir (12) for drilling fluid connected by means of a line (13) for drilling fluid with a fitting (18) and a valve (V2) (20) connecting the drilling fluid to the main outlet line (22). The tank (12) additionally contains a line (15) leading to the fitting. The line (15) is provided with a valve (17) to remove air from the line. This operation is determined and implemented by the computer through activation via line (28). Line (26) brings fluid to a separator (not shown). When the drill string is stopped to add a stand, mud pumping is stopped and the gas compressor (10) is turned on to keep the pressure in the wellbore within an acceptable range. The compressibility of the gas used provides "shock" absorption and blowout prevention without the need to operate within a very narrow pressure range compared to the conventional systems described above. The second advantage of the illustrated system is that it prevents undesirable formation of cracks in the formations, also due to the compressibility of the gas used. This has significant advantages over conventional systems while providing a valuable safety element when adding/removing a spark plug. In FIG. 2 is a graphical representation of process-time estimates for the apparatus of the present invention, as well as a method of using said apparatus based on classical thermodynamics. The figure shows the relationship between the injection rate of the gas used (nitrogen) and the time (in seconds) to pressurize. Fig. 3 illustrates an alternative preferred embodiment in which the gas compressor (10) is fluidly connected to the drilling fluid reservoir (12) and nitrogen can be pumped directly into the bleed line upstream (40) from the MPD manifold (34) and/ or inside the reservoir (12) for drilling fluid. The pressure sensor is located on the main outlet line (22) behind the drilling fluid injection point (42). Behind the pressure sensor is a controlled pressure drilling rig (34) (MPD manifold) containing various valves and fittings (including fitting 1 (44) and fitting 2 (46)). Both nozzles 1 and 2 (44 and 46) are in fluid communication with the gas compressor (10) and the main outlet line (22). To the left of the manifold (34) MPD is a bypass line (26) leading to a separator (36). Preferably, a flow meter (38) is located along the line to provide the user with information on the flow rate of the fluid entering the separator. To provide operational flexibility to maintain and/or optimize the pressures and flows of various fluids, multiple valves are located throughout the plant, both within the MPD and along the various lines.

Fig. 4 illustrates another alternative preferred embodiment in which the mud tank is removed and nitrogen is pumped directly from the gas compressor (10) into a bleed line (48) upstream of the throttle manifold, or into a line (50) leading directly to main branch line (22), before the last connection to the MPD manifold. There is a pressure sensor (25) located on the main outlet line (22) behind the compressed gas injection point (52). Behind the pressure sensor is a controlled pressure drilling rig (34) (MPD manifold) containing various valves and fittings (including fitting 1 (44) and fitting 2 (46)). Both nozzles 1 and 2 (44 and 46) are in fluid communication with the gas compressor (10) and the main outlet line (22). To the left of the manifold (34) MPD is a bypass line (26) leading to a separator (36). Preferably, a flow meter (38) is located along the line to provide the user with information on the flow rate of the fluid entering the separator. In this embodiment, the gas compressor is connected directly to the main return line, with no mud tank present.

In accordance with another embodiment of the present invention, a downhole bladder can be inserted into a wellbore and pumped with pressurized gas to maintain/regulate downhole pressure. Preferably, the downhole bladder contains an internal volume configured to be pumped with pressurized injectable fluid. Also preferably, the bladder includes a device for holding it in place at the insertion site to prevent a downhole pressurized blowout.

The embodiments described herein are to be understood as exemplary, and numerous variations and variations of the present invention are possible in light of the foregoing. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Claims (26)

1. A method for controlling the pressure of a well fluid in a wellbore during a controlled pressure drilling operation, comprising: - the stage of interrupting the injection of drilling fluid into the specified well; - the step of injecting a compressible fluid into the upper part of said well, downstream of a choke located on the manifold of the MPD system; - the step of monitoring the volume of injected compressible fluid to control pressure in said well; wherein the compressible gas is injected between the reservoir and the wellbore. 2. A method for buffering downhole fluid pressure in a wellbore during a managed pressure drilling operation, comprising: - the stage of interrupting the injection of drilling fluid into the specified well; - the step of injecting a compressible fluid into the upper part of said well downstream of a choke located on the manifold of the MPD system; - the step of monitoring the volume of injected compressible fluid to control pressure in said well; wherein the compressible gas is injected between the reservoir and the wellbore. 3. The method of claim. 1, in which the compressible gas is selected from the group consisting of: carbon dioxide, air, nitrogen, and combinations thereof. 4. The method according to any one of paragraphs. 1-3, in which the compressible gas is nitrogen. 5. The method according to any one of paragraphs. 1-4, further including a ramp chart containing a number of parameters obtained from the pressure monitoring system, these parameters being required by the operator to keep the bottomhole pressure close to a constant level during the MPD connection process. 6. The method of claim 5, wherein the parameters include at least one of: mud mass, main pump pressures, mud flow rates, drill string ROP, drill string RPM, backpressure applied to the surface, and sensor data. transmitted by specified bottomhole equipment. 7. The method according to p. 6, including the steps: lowering the pressure in the pump that injects the drilling fluid into the wellbore, and adjusting the nozzle for drilling with controlled pressure in accordance with the schedule of linear changes; and simultaneously injecting said gas and performing said ramp schedule. 8. A system for use in drilling oil or gas wells in conjunction with a mud injection device, wherein said mud injection device is configured to maintain fluid pressure control in the wellbore while the drill string is operating in it, the system comprising: - a gas reservoir containing a gas suitable for injection, to control the pressure in the well; a compression system in fluid communication with the gas reservoir and the well; - a pressure control system operatively associated with the gas reservoir and the well and configured to measure the pressure in the annulus, in which, when the drilling operation is stopped to add a new stand to the drill string and the mud injection device is stopped, gas is injected into the upper part wellbore to maintain the pressure in the well in the annulus of the wellbore at a level close to constant. 9. The system of claim 8, further comprising a gas injection well in fluid communication with the gas reservoir and the well. 10. A system for use in drilling oil or gas wells, configured to clean lines when the drilling rig is operating with a drill string, comprising: - a gas reservoir containing a gas suitable for injection to clean the bypass lines from the gas released from the well in which the drill string is installed; a compression system in fluid communication with the gas reservoir, flow lines and well; - a pressure control system operatively associated with the gas reservoir and the well and configured to measure pressure in the annulus of the well; moreover, at any given time during the drilling operation, it is possible to inject said gas suitable for injection through the lines for cleaning the latter from gases released in the formation.

Images