DOWNHOLE NON-THERMAL RADIOISOTOPE POWER SOURCE FOR OPERATION IN A WELLBORE

Some implementations include a downhole power source to be positioned in a wellbore to supply electrical power to an electrical device in the wellbore, the downhole power source comprising a radioisotope source to be positioned downhole in the wellbore to emit radiation. One or more semiconductor layers to be positioned downhole in the wellbore may be configured to capture the emitted radiation from the radioisotope source and to may be configured to generate the electrical power based on the captured radiation.

BACKGROUND

Providing downhole electric power to tools and equipment is typically accomplished by running cables from the surface into a well, using a downhole turbine for power generation, or by using batteries in a tool with a finite life and charge. Conventional approaches may be expensive. These conventional approaches may also limit an operating window of a completion, particularly in the case of batteries and turbine generators that require constant production flow to generate power.

DESCRIPTION

The description that follows includes example systems, methods, techniques, and program flows that embody aspects of the disclosure. However, it is understood that this disclosure may be practiced without these specific details. In other instances, well- known instruction instances, protocols, structures, and techniques have not been shown in detail in order not to obfuscate the description.

Example embodiments may include a non-thermal radio-voltaic power source positioned downhole in a wellbore to generate power independent of thermal conditions in the wellbore. Non-thermal radio-voltaic power sources may be capable of generating power for many years and even decades in downhole conditions due to the solid-state nature of their construction. In contrast, a traditional battery in such conditions may have a life measured in weeks or months. Additionally, non-thermal radio-voltaic power sources may provide power to any type of device downhole (such as sensors and other downhole tools) without external cables or other moving parts. Accordingly, example embodiments may provide power to downhole devices to allow such devices to continue to operate even after a well is shut in and/or long after a traditional battery positioned downhole has been depleted. Issues stemming from battery degradation in high-temperature applications may also be avoided.

Example Downhole Non-thermal Radio-Voltaic Power Source

An example downhole non-thermal radio-voltaic power source is now described.FIG.1depicts an example non-thermal radio-voltaic downhole power source and an electrical device to be powered by the non-thermal radio-voltaic downhole power source, according to some embodiments. InFIG.1, a non-thermal radio-voltaic downhole power source100is electrically coupled to an electrical device106. The non-thermal radio-voltaic downhole power source100may comprise a radioisotope source102and one or more semiconductor layers104.

In some embodiments, the radioisotope source102may comprise tritium, but a number of different radioisotopes may be used as the radioisotope source102. The radioisotope source102may be in the form of a solid section of foil, although other configurations are possible. The radioisotope source102may emit alpha, beta, and/or gamma particles as radiation. The radioisotope source102and the semiconductor layers104may be configured to be placed within close proximity of one another. The semiconductor layers104may be configured to capture the particles emitted as radiation from the radioisotope source102. The non-thermal radio-voltaic downhole power source100may produce electrical energy by converting the alpha, beta and/or gamma radiation emitted from the radioisotope source102and captured by the semiconductor layers104. In some embodiments, the semiconductor layers104may be part of a multilayer solid-state semiconductor structure comprising one or more P-N junctions and electric fields between layers. The semiconductor layers104may comprise a P-type semiconductor, an N-type semiconductor, or a combination of one or more layered P-type and N-type semiconductors. In some embodiments, the semiconductor layers104may comprise various thicknesses to capture the different types of particles emitted by the radioisotope source102. In some implementations, the semiconductor layers104may comprise one or more thin layers of silicon, diamond, or other materials that have a high energy conversion efficiency and that may withstand the radiation emitted by the radioisotope source102.

Rather than using a thermal differential across the semiconductor layers104to generate electricity, the non-thermal radio-voltaic downhole power source100utilizes the radiated particles from the radioisotope source102. Some of the particles emitted by the radioisotope source102(for example, the beta particles) may be captured by the semiconductor layers104. Kinetic energy from the particles may be converted into electrical energy by the semiconductor layers104at a p-n junction diode separated by a depletion region. When a radiated particle enters the semiconductor layers104, it may deposit its energy and create electron-hole pairs separated by an electric field. The electrons and holes then flow in opposite directions, creating a current that may be used to power an external circuit. The holes may collect on a positive side108of the semiconductor layers104while the electrons travel to a negative side110due to built-in potential at the p-n junction between the P-type and N-type layers. The electrons may travel through a circuit coupled with an electrical device106to rejoin their respective holes, thus providing power to the electrical device106. The non-thermal radio-voltaic downhole power source100may be utilized for low power applications at, for example, a milliwatt or microwatt scale. In some embodiments, multiple non-thermal radio-voltaic downhole power sources100may be combined in series to provide a larger power output.

The electrical device206may be any type of downhole device using electrical power. For example, the electrical device106may be one or more micro-controllers, sensors, or motors depending on their power requirements. In other embodiments, the electrical device106may be a power storage device (e.g., a battery, a capacitor, a solenoid, etc.). In some implementations, the radioisotope source102may be configured to power other components for use in downhole tools as well as charge capacitors, batteries, or other downhole power storage devices. In some implementations, the downhole power storage system may be used in conjunction with the non-thermal radio-voltaic downhole power source100to power an electronic component such as a sensor for a limited amount of time. In some embodiments, the radioisotope source102and semiconductor layers104may be installed within the electrical device106.

Example System

Example downhole non-thermal radio-voltaic power sources may be used in any downhole system/application (e.g., production, completion, drilling, etc.). An example well completion system utilizing the non-thermal radio-voltaic downhole power source fromFIG.1is now described.FIG.2depicts an example well completion system, according to some embodiments. A well completion system200may comprise a wellbore212which intersects a subsurface formation220. The wellbore212may include a vertical section214(which is at least partially cemented with a casing string216) and a horizontal section218. The horizontal section218may be an open-hole section of the wellbore212. Other wellbore configurations may also be suitable.

Positioned within the wellbore212and extending from the surface is a tubing string222which provides a conduit for formation fluids to travel from the subsurface formation220to the surface and for stimulation fluids to travel from the surface to the subsurface formation220. The tubing string222may include a production section224between one or more packers226. The production section224may include a mandrel235. In some implementations, the mandrel235may include the non-thermal radio-voltaic downhole power source100fromFIG.1.

The non-thermal radio-voltaic downhole power source100positioned in the mandrel235may be configured to supply power to one or more downhole devices similar to the electrical device106ofFIG.1. The downhole devices may be one or more of sensors, micro-controllers, motors, power storage devices, etc. While described as being positioned in the mandrel235, the downhole devices being powered by a non-thermal radio-voltaic downhole power source may be positioned at any location in the wellbore212.

The production section224may comprise multiple sections of pipe, including, for example, a sand screen section. The one or more packers226may provide a fluid seal between the tubing string222and the wellbore212, thereby defining one or more production intervals230. The production section224may comprise one or more valves232(e.g., interval control valves) configured to control fluid inflow and outflow to and from the production section224. In some embodiments, the tubing string222may include a power generation source240comprising a power generation source of a larger power output than the non-thermal radio-voltaic downhole power source100to provide power to various downhole electronic components, including but not limited to pumps, sensors, actuators, valves, sleeves, baffles, etc.

For example, the power generation source240may include a processor and a turbine generator configured to convert flow fluid through the turbine into electrical power. The power generation source240may also include a downhole power storage device (e.g., a battery) with a suitable capacity to supply power to various downhole electronic components during initial completion and stimulation operations when there is insufficient fluid flow to generate enough power from the turbine generator. The downhole power storage device may also supply power to the downhole electronic components in conjunction with the turbine generator. AlthoughFIG.2depicts the power generation source240as positioned in a zone that is not being produced, it should be understood that the power generation source240may be positioned anywhere along the wellbore212, including proximate the production section224.

In some embodiments, the power generation source240may include a telemetry device252that may receive data provided by various sensors located in the wellbore212and may transmit the data to a surface control unit228. Data may also be provided by the surface control unit228, received by the telemetry device252via a wired connection from the surface, via acoustic signals, or via other communication mediums. The telemetry device252may additionally transmit signals to the various electronic devices located in the wellbore112to perform functions, such as actuating one or more valves. The surface control unit228may include a computer system for processing and storing the measurements gathered by one or more sensors located in the wellbore212. Among other things, the computer system may include a non-transitory computer-readable medium (e.g., a hard-disk drive and/or memory) capable of executing instructions to perform such tasks. In addition to collecting and processing measurements, the computer system may be capable of controlling completion, stimulation, and production operations including but not limited to as installation of the packers226, acidizing, gravel packing, or hydraulic fracturing.

A more detailed description of an example of the mandrel235fromFIG.2is now described.FIG.3depicts an example cross-section of a mandrel housing the non-thermal radio-voltaic downhole power source, according to some embodiments. A mandrel303may be disposed along a tubing301. The tubing301is positioned in a wellbore350that is formed in a subsurface formation320. While depicted as a compartment closed off from the tubing301, in some embodiments the mandrel303may be open to an interior of the tubing301. Other positions and configurations may be possible. The mandrel303may be similar to the mandrel235fromFIG.2, and the mandrel303may comprise a power source housing327within. The power source housing327may house a radioisotope source302and one or more semiconductor layers304. In some embodiments, the radioisotope source302and semiconductor layers304may be similar to the radioisotope source102and semiconductor layers104described in the description ofFIG.1. The power source housing327may be a pressurized chamber set to the atmospheric pressure at the surface and isolated from a formation fluid319flowing from the subsurface formation320. In some embodiments, the power source housing327may be comprised of metal or ceramic to prevent the escape of some radioactive particles, but other configurations may be possible.

Similar to the non-thermal radio-voltaic downhole power source100ofFIG.1, the radioisotope source302and semiconductor layers304may be configured to generate constant, low-output power. The power generated within the power source housing327may be routed via an electrical circuit329to a sensor309. In some embodiments, a transformer (not depicted) may be disposed along the electrical circuit329. The sensor309may be similar to the electrical device106described in the description ofFIG.1, although other devices may be used. The sensor309may be coupled to a controller313which may comprise a processor. In some embodiments, the controller313may also be intermittently powered via the radioisotope source302and semiconductor layers304.

The sensor309may make measurements of the formation fluid319. The controller313may be configured to receive these measurements of the formation fluid319from the sensor309at certain time intervals. In some embodiments, the controller313may control downhole operations based on these measurements, communicate these measurements to other devices (either downhole or at the surface), etc.

For example, the controller313may be configured to initiate operation of other power sources downhole based on the measurements by the sensor309. For instance, the controller313may initiate activation of a power source that generates more power (as compared to the radioisotope source302and semiconductor layers304) to supply power to devices that may require more power than may be provided by the radioisotope source302and semiconductor layers304. For example, the larger power source may be a turbine generator, a limited duration battery, etc. to provide power to equipment in the well completion system200such as different types of flow control devices (e.g., a valve317).

For example, the sensor309may detect a change in fluid properties of the formation fluid319—thus inducing an action at the valve317. In an example scenario, a zone of the subsurface formation220may be shut-in due to a suspected high water cut. During a wake phase, the sensor309may detect that the formation fluid319comprises a higher concentration of hydrocarbons than prior measurements. The hydrocarbon concentration may exceed a property threshold identified by the controller313. Based on the measurement, the valve317may be actuated into an open position to allow fluid flow to the surface based on the measurement obtained during the wake phase of the sensor309. In other embodiments, the valve317may be configured to open once a threshold value in one or more of the properties of the formation fluid319has been met.

The larger capacity power generation source may be powered on intermittently via a separate downhole power storage device or via a motor to induce an initial fluid flow through the device (for example, through a turbine generator which may use fluid flow to generate power). Once the larger capacity power generation source has been temporarily activated to supply power to a broader completions or production system in the wellbore212, the valve317may be opened to allow the formation fluid319to enter the tubing301.

In some embodiments, if a formation property or other parameter detected by the sensor309during a wake phase changes beyond a set property threshold, the controller313may be configured to autonomously transmit data. For example, the controller313transmits a signal to the surface indicating that a property threshold of a property of the formation fluid319has been met. Alternatively, the controller313may initiate a command during a wake phase to a larger capacity power generation source located within the wellbore212, which may be similar to the power generation source240ofFIG.2. In some embodiments, the controller313may be electronically coupled to the larger capacity power generation source. The power generation source240may comprise components to generate a much larger power output than the radioisotope source302, and the command sent by the controller313may instruct the power generation source240to activate.

In other embodiments, power may be routed to a downhole power storage device (not depicted) such as a capacitor. The radioisotope source302and semiconductor layers304may output power to the downhole storage device. The downhole power storage device may be coupled to the controller313, and the controller313may be configured to store the electrical power in the downhole power storage device. The controller313may additionally be configured to control the power storage device such that the power storage device is to supply electrical power to the electrical device in response to a level of the electrical power stored in the downhole power storage device exceeding a threshold of power to enable operation of the sensor309.

In some embodiments, the downhole storage device may supply power to the sensor309at set intervals or upon user command received via the controller313. Such a configuration may enable the sensor309to sense environmental changes for a limited time before becoming dormant once again. This may be referred to as a wake/sleep cycle. During the wake phase, the sensor309may obtain measurements of the formation fluid319. In other embodiments, the sensor309may also be configured to detect pressure changes, acoustic signals, etc. The duration of the wake/sleep cycle of the sensor309(or other downhole device) may be programmed prior to conveying the sensor309into the wellbore212. This wake/sleep cycle may be set to a duration of days or weeks (i.e., until the sensor awakens again to obtain a measurement), although other durations are possible. The wake phase may last less than a second or multiple seconds depending on the task to be performed.

Example Operations

Example operations for powering downhole electrical devices using a non-thermal radio-voltaic power source are now described.FIG.4depicts a flowchart of example operations for powering downhole electrical devices, according to some embodiments. A method400describes the example operations for supplying electrical power to an electrical device in a wellbore. Operations of the method400begin at block401.

At block401, the method400comprises positioning, in a wellbore a downhole power source that comprises a radioisotope source to emit radiation and one or more semiconductor layers to capture the emitted radiation from the radioisotope source and to generate the electrical power based on the captured radiation. For example, with reference toFIGS.1-2, a downhole power source comprising the radioisotope source102and the one or more semiconductor layers104may be positioned in the wellbore212. The radioisotope source102may emit radiation such as beta particles which may induce an electrical current to generate electrical power upon capture by the one or more semiconductor layers104. Flow progresses to block403.

At block403, the method400further comprises powering the electrical device using the electrical power generated based on the captured radiation. For example, with reference toFIG.3, the captured radiation emitted from the radioisotope source302may induce a current used to provide power to the electrical circuit329. The electrical circuit329may be coupled to a downhole device and may provide power to one or more of the downhole devices such as the sensor309. Flow of the method400ceases.

While the aspects of the disclosure are described with reference to various implementations and exploitations, it will be understood that these aspects are illustrative and that the scope of the claims is not limited to them. In general, techniques for downhole power generation as described herein may be implemented with facilities consistent with any hardware system or hardware systems. Many variations, modifications, additions, and improvements are possible.

Example Embodiments

Embodiment #1: A downhole power source to be positioned in a wellbore to supply electrical power to an electrical device in the wellbore, the downhole power source comprising: a radioisotope source to be positioned downhole in the wellbore to emit radiation; and one or more semiconductor layers to be positioned downhole in the wellbore to capture the emitted radiation from the radioisotope source and to generate the electrical power based on the captured radiation.

Embodiment #2: The downhole power source of Embodiment 1, wherein the one or more semiconductor layers are to generate the electrical power independent of thermal emission from the radioisotope source.

Embodiment #3: The downhole power source of any one of Embodiments 1-2, wherein the one or more semiconductor layers are to be electrically coupled to the electrical device to be positioned in the wellbore to supply the electrical power from the one or more semiconductor layers to the electrical device.

Embodiment #4: The downhole power source of Embodiment 3, wherein the one or more semiconductor layers are to be electrically coupled to a power storage device to be positioned in the wellbore.

Embodiment #5: The downhole power source of Embodiment 4, wherein the power storage device comprises at least one of a capacitor, a battery, and a solenoid.

Embodiment #6: The downhole power source of any one of Embodiments 4-5, wherein the one or more semiconductor layers are electrically coupled to a power controller, wherein the power controller is configured to store the electrical power in the power storage device, and wherein the power controller is configured to control the power storage device such that the power storage device is to supply electrical power to the electrical device in response to a level of the electrical power stored in the power storage device exceeding a threshold of power to enable operation of the electrical device.

Embodiment #7: The downhole power source of any one of Embodiments 3-6, wherein the one or more semiconductor layers are electrically coupled to a power controller, wherein the power controller is electrically coupled to a different downhole power source that is to generate different electrical power that is greater than the electrical power generated based on the captured radiation, wherein the electrical device comprises a sensor to measure a property of a subsurface formation in which the wellbore is formed, and wherein the power controller is to control the different downhole power source to cause the different downhole power source to initiate generation of the different electrical power in response to the sensor measuring a value of the property of the subsurface formation that exceeds a property threshold.

Embodiment #8: A downhole system for use in a wellbore, the downhole system comprising: a radioisotope source to be positioned in the wellbore to emit radiation; and one or more semiconductor layers to be positioned in the wellbore to capture the emitted radiation from the radioisotope source and to generate electrical power based on the captured radiation; and an electrical device configured to be electrically coupled to the one or more semiconductor layers.

Embodiment #9: The downhole system of Embodiment 8, wherein the one or more semiconductor layers are to generate the electrical power independent of thermal emission from the radioisotope source.

Embodiment #10: The downhole system of any one of Embodiments 8-9, further comprising: a power storage device that is to be electrically coupled to the one or more semiconductor layers.

Embodiment #11: The downhole system of Embodiment 10, wherein the power storage device comprises at least one of a capacitor, a battery, and a solenoid.

Embodiment #12: The downhole system of any one of Embodiments 10-11, further comprising: a power controller configured to store the electrical power in the power storage device, and wherein the power controller is configured to control the power storage device such that the power storage device is to supply electrical power to the electrical device in response to a level of the electrical power stored in the power storage device exceeding a threshold of power to enable operation of the electrical device.

Embodiment #13: The downhole system of any one of Embodiments 8-12, wherein the electrical device comprises a sensor to measure a property of a subsurface formation in which the wellbore is formed, the downhole system further comprising: a different downhole power source that is to generate different electrical power that is greater than the electrical power generated based on the captured radiation; and a power controller to control the different downhole power source to cause the different downhole power source to initiate generation of the different electrical power in response to the sensor measuring a value of the property of the subsurface formation that exceeds a property threshold.

Embodiment #14: A method for supplying electrical power to an electrical device in a wellbore, the method comprising: positioning, in the wellbore, a downhole power source that comprises a radioisotope source to emit radiation and one or more semiconductor layers to capture the emitted radiation from the radioisotope source and to generate the electrical power based on the captured radiation; and powering the electrical device using the electrical power generated based on the captured radiation.

Embodiment #15: The method of Embodiment 14, wherein the one or more semiconductor layers are to generate the electrical power independent of thermal emission from the radioisotope source.

Embodiment #16: The method of any one of Embodiments 14-15, further comprising: storing the electrical power in a power storage device positioned in the wellbore.

Embodiment #17: The method of Embodiment 16, further comprising: determining a level of the electrical power stored in the power storage device, wherein powering the electrical device comprises, outputting the electrical power stored in the power storage device to the electrical device, in response to the level of the electrical power stored in the power storage device exceeding a threshold of power to enable operation of the electrical device.

Embodiment #18: The method of any one of Embodiments 16-17, wherein the electrical device comprises a sensor to measure a property of a subsurface formation in which the wellbore is formed.

Embodiment #19: The method of Embodiment 18, further comprising: measuring, using the sensor, a value of the property of the subsurface formation; and initiating generation of different electrical power from a different downhole power source in response to the value of the property exceeding a property threshold.

Embodiment #20: The method of Embodiment 19, wherein the different electrical power that is greater than the electrical power generated based on the captured radiation.