Patent Description:
Most wells behave characteristically different over time due to geophysical, physical, and chemical changes in the subterranean reservoir that feeds the well. For example, the phase composition of a production fluid can change during the production life cycle, meaning liquid production can increase or decrease relative to gas production. Such liquids can include water or condensate. As production parameters of the well change, additional equipment can be added to maintain production. For example, a downhole pump or compressor is sometimes used to extend the life of the well.

<CIT> describes systems and methods for reducing or removing condensate blockage in a natural gas wellbore and a near-wellbore formation.

This specification describes technologies relating to lifting condensate from wellbores.

The invention is defined in the claims. An example implementation of the subject matter described within this disclosure is a method with the following features. A vacuum chamber is evacuated by a vacuum pump. The vacuum chamber is positioned within a wellbore. A wellbore is fluidically exposed to an interior of the vacuum chamber after the vacuum chamber has been evacuated. At least a portion of condensate within the wellbore is flashed responsive to fluidically exposing a wellbore to an interior of the vacuum chamber.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The vacuum chamber is received into the wellbore.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. Receiving the vacuum chamber into the wellbore includes receiving the vacuum chamber such that the vacuum chamber is at a depth roughly adjacent to a pay zone of a wellbore.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. Exposing the wellbore to the interior of the vacuum chamber includes reducing a pressure within the wellbore by <NUM> pounds per square inch or <NUM> MPa.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. Substantially free gas is flowed out of the wellbore.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The vacuum chamber is removed from the wellbore after flashing the condensate.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. Fluidically exposing the wellbore to an interior of the vacuum chamber includes uncovering openings defined by an outer wall of the vacuum chamber.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. Microwaves are emitted within the wellbore by a microwave emitter positioned within the wellbore. At least a portion of condensate within the wellbore is flashed responsive to emitting the microwaves.

An example implementation of the subject matter described within this disclosure is a well intervention tool with the following features. A vacuum chamber is fluidically connected to a vacuum pump. The vacuum chamber includes an outer surface defining a chamber fluidically coupled to the vacuum pump. The outer surface defines an actuable orifice that is actuable between and open state and a closed state. The orifice fluidically connects the chamber and a downhole environment in the open state. The orifice fluidically isolates the chamber from the downhole environment in a closed state.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The vacuum pump is located within the downhole environment.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The actuable orifice includes a sleeve defining a profile that mates with the outer surface of the vacuum chamber. The sleeve is rotatable in a circumferential direction along the surface of the vacuum chamber.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. A motor is coupled to the sleeve. The motor is arranged to change the sleeve between the open state and the closed state.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The vacuum pump includes a positive displacement pump.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The orifice is a first orifice. The well intervention tool includes a multiple orifices. The orifices have a total flow area sufficient to allow fluid communication. Each of the orifices has a flow area small enough to filter sand out of a fluid flow.

An example implementation of the subject matter described within this disclosure is a well system with the following features. A vacuum chamber is fluidically connected to a vacuum pump. The vacuum chamber includes an outer surface defining a chamber fluidically coupled to the vacuum pump. The outer surface defines an actuable orifice that is actuable between and open state and a closed state. The orifice fluidically connects the chamber and a downhole environment in the open state. The orifice fluidically isolates the chamber from the downhole environment in a closed state. A length of coiled tubing fluidically connects the vacuum chamber to a topside facility.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The vacuum pump is located at the topside facility. The vacuum pump is fluidically connected to the vacuum chamber by the length of coiled tubing.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. A controller is configured to receive a signal indicative of a wellbore pressure. The controller is configured to determine, based on the signal, a presence of a condensate bank. The controller is configured to evacuate a vacuum chamber, by a vacuum pump, in response to determining the presence of a condensate bank. The controller is configured to fluidically expose the evacuated vacuum chamber to a wellbore environment.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. The vacuum chamber and length of coiled tubing are permanently installed within the downhole environment.

Aspects of the example implementation, which can be combined with the example implementation alone or in combination, include the following. Sand separation facilities are at the topside facility.

Particular implementations of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. The systems and methods described herein can be implemented on short notice without mobilizing a drill rig. The systems and methods described herein can increase the productive lifespan of a production well with minimal downtime. The system described herein can be permanently or temporarily installed within a production wellbore.

The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and description.

In hydrocarbon production, condensate caps can occur, particularly in retrograde condensate production wells. The formation of such caps can reduce or cease gas production within a wellbore. When this happens, submersible pumps are sometimes deployed to produce the condensate liquid. Such interventions require extensive downtime and large pieces of equipment to be installed during a workover. In some instances, production wells can be abandoned entirely in response to the formation of such caps. In some instances, injecting dry gas into the reservoir can help maintain the reservoir pressure above the dew point pressure as well as displace the valuable condensate in the reservoir and re-vaporizes the condensate if a blockage is performed. Adding gas injection facilities require extensive downtime and large facilities to be installed. In some instances, capillary pressure, which causes condensate to be trapped in the reservoir, can be reduced by decreasing the interfacial tension. Solvents like alcohol can be used to reduce the interfacial tension or wettability and remove condensate through a multi-contact miscible displacement. Large quantities of such solvents are required for such a solution and require the construction of chemical injection facilities.

This disclosure describes removing a condensate blockage or cap using a vacuum source within the wellbore. A blockage is detected based on a wellbore pressure. When a blockage occurs, the vacuum source is activated to decrease the pressure within the wellbore. The decreased pressure changes the condensate from a mixed-phase gas condensate to a gas phase. This will free the near wellbore region from an excess of condensate and allow gas from the reservoir to more freely flow into the wellbore. The gas phase is then produced.

<FIG> illustrates a side cross-sectional diagram of an example well system 100a. The well system 100a includes a vacuum pump <NUM>. A vacuum chamber <NUM> is fluidically connected to the vacuum pump <NUM>. The vacuum chamber <NUM> is positioned within the wellbore <NUM> such that it is substantially laterally adjacent to the production zone <NUM>, and can extend substantially one-half to an entire length of the production zone <NUM>. For example, for a production zone extending fifty feet or <NUM> meters, the vacuum chamber <NUM> length would be between twenty-five feet and fifty feet or between <NUM> meters and <NUM> meters within standard manufacturing tolerances. As illustrated, a condensate cap <NUM> is present and can inhibit production.

A tubular <NUM> fluidically connects the vacuum chamber <NUM> to a topside facility <NUM>. Such a tubular <NUM> can include coiled tubing, production tubing, drill pipe, or any other tubular that is rated for vacuum within a wellbore environment. In some implementations, sand separation facilities can be included at the topside facility <NUM>. An isolation packer <NUM> fluidically isolates a production zone <NUM> from a remainder of a wellbore <NUM>.

In some implementations, the vacuum pump <NUM> can be a positive displacement pump such as a diaphragm or plunger pump. In some implementations, other pump styles can be used as vacuum pumps, such as a centrifugal pump. In some implementations, multiple pumps can be used to achieve the desired vacuum. While illustrated as a vertical wellbore for simplicity, the concepts described herein are applicable to horizontal and deviated wellbores as well.

<FIG> is a side cross-sectional view of an example vacuum chamber <NUM>. The vacuum chamber <NUM> includes an outer surface <NUM> defining the vacuum chamber <NUM>. The outer surface <NUM> defines an actuable orifice <NUM> that is actuable between an open state <NUM> and a closed state <NUM>. The orifice <NUM> fluidically connects the vacuum chamber <NUM> and a downhole environment, such as the wellbore <NUM>, when in the open state <NUM>. The orifice <NUM> fluidically isolates the vacuum chamber <NUM> from the downhole environment, such as the wellbore <NUM>, when in a closed state <NUM>. In some implementations, the actuable orifice <NUM> of the vacuum chamber <NUM> includes a sleeve <NUM> defining a profile that mates with the surface <NUM> of the vacuum chamber <NUM>. The sleeve <NUM> is rotatable in a circumferential direction along the surface of the vacuum chamber <NUM>. The sleeve <NUM> can be arranged such that it rotates along either an inner surface or an outer surface of the vacuum chamber <NUM>. In some implementations, multiple sleeves can be used. A motor or actuator <NUM> is coupled to the sleeve <NUM>. The actuator <NUM> is arranged to change the sleeve <NUM> between the open state <NUM> and the closed state <NUM>. For example, the actuator <NUM> can rotate the sleeve to remove a restriction from the orifice <NUM> and allow fluid contact between the vacuum chamber <NUM> and the wellbore <NUM>. Such an arrangement allows for a near-instant pressure drop (within a few seconds), allowing the condensate to at least partially flash from a liquid state to a gaseous stated. The pressure drop is not at the reservoir level at this stage, rather it provides a suction effect which flashes condensate from the production zone <NUM>. The amount of condensate removal depends of the total volume of the vacuum chamber. In some instances, the system can be cycled multiple times to achieve a target pressure drop. While illustrated as being cylindrical in shape, the vacuum chamber <NUM> can be constructed in a variety of shapes without departing from this disclosure so long as the interior volume is sufficient to create the desired pressure drop within the wellbore <NUM> during operation. Similarly, other actuation mechanisms and arrangements can be used without departing from this disclosure.

In some implementations, a microwave emitter <NUM> can be attached to the vacuum chamber <NUM>. The microwave emitter <NUM> can be used to add heat to a production fluid and at least partially change a portion of the liquid phase into a gas phase. In some implementations, the microwave emitter <NUM> can be sized to achieve the desired heating affects. For example, a <NUM>-Watt microwave emitter can be used.

A pressure sensor <NUM> is attached to or in proximity to the vacuum chamber <NUM>. The pressure sensor <NUM> creates a digital or analog pressure stream that can be interpreted by a controller. Such a controller is described later within this disclosure.

In some implementations, the orifice <NUM> is a first orifice <NUM>. The well vacuum chamber <NUM> can include multiple orifices <NUM>. In general, the orifices <NUM> have a total flow area sufficient to allow fluid communication with the wellbore <NUM>, while each of the individual orifices <NUM> can have a flow area small enough to filter sand out of a fluid flow. In some implementations, separate sand screens in the wellbore or separate sand screens encircling the vacuum chamber <NUM> can be used. The well system <NUM> described herein can be installed temporarily to relieve a condensate cap <NUM>, or it can be permanently installed, such as when a condensate cap <NUM> is expected to be a regular occurrence during the production life of the wellbore <NUM>.

In some implementations, such as the one illustrated in <FIG>, the vacuum pump <NUM> is located at the topside facility <NUM>. In such an implementation, the vacuum pump <NUM> is fluidically connected to the vacuum chamber <NUM> by the tubular <NUM>. The well system 100b illustrated in <FIG> is substantially similar to the implementation illustrated in <FIG> with the exception of any differences described herein. In some implementations, such as the one illustrated in <FIG>, the vacuum pump <NUM> is located within the wellbore <NUM>. While illustrated as being installed uphole of the packer <NUM>, the vacuum pump <NUM> can be located downhole of the packer <NUM> as well. In implementations where the vacuum pump <NUM> is located within the wellbore, power can be provided from the topside facility to power the vacuum pump <NUM>. Regardless of the vacuum pump <NUM> location, the vacuum chamber <NUM> is fluidically connected to the topside facility <NUM> by the tubular <NUM> so that wellbore fluids can be lifted from the wellbore <NUM> through the tubular <NUM>.

<FIG> is an example phase diagram <NUM> illustrating the potential phases that can be found in a downhole environment, such as within wellbore <NUM>. In operation, the well system <NUM> begins with the phase of produced fluid being point B<NUM> <NUM>. Point B<NUM> <NUM> includes a temperature and pressure where sufficient condensate (liquid) is present to hinder gas flow through the wellbore <NUM>. Once the vacuum chamber <NUM> is evacuated and fluidically exposed to the wellbore <NUM>, the pressure brings the phase from point B<NUM> <NUM> to point B<NUM> <NUM>. Point B<NUM> <NUM> includes a temperature and pressure where sufficient condensate (liquid) has been flashed off (liquid has been phase-changed to gas) to allow gas to more freely flow through the wellbore <NUM>. In general, the aim is to bring the production point from B<NUM> <NUM> to B<NUM> <NUM> at constant temperature (which is the formation temperature). Such a pressure shift can decrease the amount of condensate liquid and therefore free the near production zone <NUM> from excessive liquid to increase gas production. In some implementations, the additional microwave emitter <NUM> can be used to heat the production fluid, moving the phase of the production fluid from point B<NUM> <NUM> to point Ai <NUM>. Ai <NUM> is a point where the wellbore <NUM> produces single-phase gas. The pressure change from fluidically exposing the wellbore to the evacuated vacuum chamber <NUM> can be as high as <NUM> pounds per square inch or <NUM> MPa. While described as beginning at point B<NUM> <NUM>, the phase changes described herein are applicable to any point where an amount of condensate is sufficient to reduce production flow.

As shown in <FIG>, the well system includes a controller <NUM> to, among other things, monitor pressures of the wellbore <NUM> and send signals to actuate the sleeve <NUM> or vacuum pump <NUM>. As shown in <FIG>, the controller <NUM> can include a processor <NUM> (implemented as one or more local or distributed processors) and non-transitory storage media (for example, memory <NUM> - implemented as one or more local or distributed memories) containing instructions that cause the processor <NUM> to perform the methods described herein. The processor <NUM> is coupled to an input/output (I/O) interface <NUM> for sending and receiving communications with other equipment of the well system <NUM> (<FIG>) via communication links. In certain instances, the controller <NUM> can communicate status with and send actuation and control signals to one or more of the motor <NUM>, the vacuum pump <NUM>, the microwave emitter <NUM>, and other components, such as topside valves, as well as various sensors (such as, pressure sensor <NUM>, temperature sensors, and other types of sensors) at the well site. In certain instances, the controller <NUM> can communicate status and send actuation and control signals to one or more of the systems on at the topside facility <NUM>, such as pumps, compressors, separators, and other equipment on the topside facility <NUM>. The communications can be hard-wired, wireless, or a combination of wired and wireless. In some implementations, the controller <NUM> can be located remote from the well system <NUM>, such as in a data van, at the topside facility <NUM>, downhole within the wellbore <NUM>, or even remote from the well system <NUM> (such as, at a central monitoring facility for monitoring and controlling multiple well sites). In some implementations, the controller <NUM> can be a distributed controller with different portions located about the well system <NUM> or off site. For example, in certain instances, a portion of the controller <NUM> can be distributed among individual well system <NUM> components, while another portion of the controller <NUM> can be located within a data van or control room.

The controller <NUM> can operate in monitoring, controlling, and using the well system <NUM> for reducing or eliminating a condensate cap within the wellbore <NUM>. To monitor and control the well system <NUM>, the controller <NUM> is used in conjunction with sensors to measure the pressure of fluid within the wellbore <NUM>. Input and output signals, including the data from the sensors and actuators, controlled and monitored by the controller <NUM>, can be logged continuously by the controller <NUM>.

For example, an operator, via the controller <NUM>, can orchestrate vacuum pump operations. According to the present invention, the memory <NUM> includes instructions for the processor to receive a signal indicative of a wellbore pressure, determine, based on the signal, a presence of a condensate bank or plug, evacuate a vacuum chamber, by a vacuum pump, in response to determining the presence of a condensate bank, and fluidically expose the evacuated vacuum chamber to a wellbore environment.

In some implementations, a human operator can operate the controller <NUM>, and thus the resulting physical steps, at a safe distance from the high pressure lines, far enough that if there were a leak or failure, the operator would not be injured. The operation can be effectuated via a terminal or other control interface associated with the controller <NUM>. In certain instances, the operator, via controller <NUM>, actuates a fully automated sequence run by the controller <NUM> to perform the steps described herein (that is, the operator just presses start, or similar, and the controller <NUM> performs autonomously). Alternatively, the operator, via controller <NUM>, commands one or more of the individual, later described steps. In either instance, the terminal can present menu items to the operator that present the operator's options in commanding the controller <NUM>.

<FIG> is a flowchart of an example method <NUM> that can be used with aspects of this disclosure. The vacuum chamber <NUM> is received by the wellbore <NUM>. In some implementations, receiving the vacuum chamber <NUM> into the wellbore <NUM> includes receiving the vacuum chamber <NUM> such that the vacuum chamber <NUM> is at a depth substantially adjacent to the production zone <NUM> of the wellbore <NUM> (within typical field placement error).

At <NUM>, the vacuum chamber <NUM> is evacuated by the vacuum pump <NUM>. At <NUM>, the wellbore is fluidically exposed to an interior of the vacuum chamber <NUM> after the vacuum chamber <NUM> has been evacuated. In some implantations, exposing the wellbore <NUM> to the interior of the vacuum chamber <NUM> reduces a pressure within the wellbore by <NUM> pounds per square inch (PSI) or <NUM> MPa. In general, the pressure drop generated can vary between <NUM> PSI and <NUM> PSI or between <NUM> MPa and <NUM> MPa. For example, illustrated in <FIG>, reducing the pressure from point B<NUM> <NUM> to point B<NUM> <NUM> results in a pressure decrease of about <NUM> PSI or <NUM> MPa. Fluidically exposing the wellbore <NUM> to an interior of the vacuum chamber <NUM> includes uncovering openings defined by an outer wall of the vacuum chamber <NUM>, such as the orifice <NUM>.

At <NUM>, at least a portion of condensate within the wellbore <NUM> is flashed responsive to fluidically exposing a wellbore <NUM> to an interior of the evacuated vacuum chamber <NUM>. In some implementations, microwaves can be emitted within the wellbore <NUM> by a microwave emitter <NUM> positioned within the wellbore. In such an implementation, at least a portion of condensate within the wellbore <NUM> is flashed responsive to the emitted microwaves.

After the condensate has flashed into free gas, the free gas can be flowed out of the wellbore in sufficient quantity to reduce the likelihood of a condensate cap reforming. In some implementations, multiple cycles of evacuation and exposure may be necessary to fully eliminate the condensation cap.

Claim 1:
A method (<NUM>) comprising:
evacuating (<NUM>) a vacuum chamber (<NUM>) by a vacuum pump (<NUM>), the vacuum chamber being positioned within a wellbore;
fluidically exposing (<NUM>) the wellbore to an interior of the vacuum chamber after the vacuum chamber has been evacuated; characterized by
flashing (<NUM>) at least a portion of condensate within the wellbore responsive to fluidically exposing the wellbore to the interior of the vacuum chamber.