Patent Description:
This disclosure relates to surface to downhole wireless communication.

Downhole communication in a wellbore involves communication between surface equipment disposed at or above a surface of the wellbore and downhole equipment disposed within the wellbore. For example, a signal can be transmitted from surface equipment to downhole equipment. For example, a signal can be transmitted from downhole equipment to surface equipment. The communication can be completed via a wired connection (for example, a wireline) or via a wireless connection. Downhole communication can also involve communication between two different equipment located downhole.

<CIT> describes a downhole system that has a plurality of telemetry systems and a control system configured to obtain information from one or more sensors and transmit that information on one or more of the plurality of telemetry systems. The configuration of a controller may be changed so as to change which information is transmitted on a given telemetry system and how the information is to be transmitted on the given telemetry system.

<CIT> describes a data sampling and collection system in an oil drilling system includes a data acquirer installed in the measurement sub to transmit a sampling collector identification signal to one of a plurality of sampling collectors coupled to the data acquire.

<CIT> describes a method for transmission of data from a downhole sensor array. A continuous unidirectional data stream is sent from the downhole sensor array to two or more different types of data transmitters at the same time.

<CIT> describes a measuring-while-drilling system includes a sensor sub positioned at the lower end of a downhole motor assembly so that the sub is located near the drill bit. The sub houses instrumentalities that measure various downhole parameters such as inclination of the borehole, the natural gamma ray emission of the formations, the electrical resistivity of the formations, and a number of mechanical drilling performance parameters. Sonic or electromagnetic telemetry signals representing these measurements are transmitted uphole.

This disclosure describes technologies relating to downhole wireless communication. Certain aspects of the subject matter described can be implemented as a system as recited in claim <NUM>.

This, and other aspects, can include one or more of the following features.

In some implementations, the dump valve is a first dump valve. In some implementations, the surface valve sub-assembly includes a second dump valve. In some implementations, the first dump valve and the second dump valve are in a parallel flow configuration.

In some implementations, the downhole sub-system and the surface valve sub-assembly are coupled by a coiled tubing that fluidically couples the pump to the turbine-generator.

In some implementations, the surface controller includes a surface processor and a surface computer-readable storage medium coupled to the surface processor. In some implementations, the surface computer-readable storage medium is non-transitory. In some implementations, the surface computer-readable storage medium stores programming instructions for execution by the surface processor. In some implementations, the programming instructions instruct the surface processor to perform operations including adjusting an amount of the first portion of the fluid pumped by the pump by adjusting fluid flow through each of the first dump valve and the second dump valve, such that a sinusoidal signal is hydraulically transmitted to the downhole sub-system via the second portion of the fluid pumped by the pump.

In some implementations, the turbine-generator is configured to receive the sinusoidal signal via the second portion of the fluid pumped by the pump and change the output in response to the receiving the sinusoidal signal, and the downhole controller is configured to process the change in the output.

In some implementations, the surface controller is configured to modulate the sinusoidal signal that is hydraulically transmitted to the downhole sub-system via the second portion of the fluid pumped by the pump, and the downhole controller is configured to de-modulate the sinusoidal signal that is hydraulically transmitted to the downhole sub-system via the second portion of the fluid pumped by the pump.

In some implementations, the downhole controller is configured to process the change in the output of the turbine-generator, such that a power output of the turbine-generator is maintained to be greater than a minimum power output threshold.

Certain aspects of the subject matter can be implemented as a method as recited in claim <NUM>.

In some implementations, flowing the second portion of the fluid from the container to the downhole sub-system includes flowing the second portion of the fluid through a coiled tubing fluidically coupled to the turbine-generator.

In some implementations, the dump valve is a first dump valve. In some implementations, the surface valve sub-assembly includes a second dump valve. In some implementations, the first dump valve and the second dump valve are in a parallel flow configuration. In some implementations, a split of the first portion of the fluid between the first dump valve and the second dump valve is adjusted by the surface controller.

In some implementations, adjusting the split of the first portion of the fluid between the first dump valve and the second dump valve comprises adjusting the fluid flow through each of the first dump valve and the second dump valve, such that a sinusoidal signal is hydraulically transmitted to the downhole sub-system via the second portion of the fluid.

In some implementations, the sinusoidal signal is received by the turbine-generator via the second portion of the pump. In some implementations, the output generated by the turbine-generator is changed in response to receiving the sinusoidal signal.

In some implementations, the downhole sub-system includes a circulation valve downstream of the turbine-generator. In some implementations, the circulation valve is communicatively coupled to the downhole controller. In some implementations, the change in the output is processed by the downhole controller. In some implementations, fluid flow through the circulation valve is adjusted by the downhole controller at least based on the processing of the change in the output.

In some implementations, the sinusoidal signal that is hydraulically transmitted to the downhole sub-system via the second portion of the fluid is modulated by the surface controller. In some implementations, the sinusoidal signal that is hydraulically transmitted to the downhole sub-system via the second portion of the fluid is de-modulated by the downhole controller.

In some implementations, processing the change in the output includes processing the change in the output, such that the power output of the turbine-generator is maintained to be greater than a minimum power output threshold.

Certain aspects of the subject matter described can be implemented as a system as recited in claim <NUM>.

In some implementations, the dump valves are in a parallel flow configuration.

In some implementations, the downhole sub-system and the surface sub-system are coupled by a coiled tubing.

In some implementations, the surface controller includes a surface processor and a surface computer-readable storage medium coupled to the surface processor. In some implementations, the surface computer-readable storage medium is non-transitory. In some implementations, the surface computer-readable storage medium stores surface programming instructions for execution by the surface processor. In some implementations, the surface programming instructions instruct the surface processor to perform surface operations. In some implementations, the downhole controller includes a downhole processor and a downhole computer-readable storage medium coupled to the downhole processor. In some implementations, the downhole computer-readable storage medium is non-transitory. In some implementations, the downhole computer-readable storage medium stores downhole programming instructions for execution by the downhole processor. In some implementations, the downhole programming instructions instruct the downhole processor to perform downhole operations.

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

This disclosure describes downhole wireless communication. Some well operations, such as well intervention, require data (sometimes in the form of command signals) to be communicated downhole to a tool string disposed within a wellbore. Some examples of methods of such downhole communication include the use of a wired connection, pressure or flow fluctuations in a circulation fluid, or pulling and pushing of coiled tubing. Wireless communication can be preferred in some cases, such as acid stimulation in multilateral wells. The systems and methods described in this disclosure include a surface sub-system and a downhole sub-system. Each of the surface and downhole sub-systems include a controller. The surface sub-system includes one or more dump valves that the surface controller controls to adjust flow of fluid downhole into a wellbore as a form of signal transmission for downhole wireless communication. The downhole sub-system disposed within the wellbore includes a turbine-generator that receives the fluid flow. The downhole controller, which is communicatively coupled to the turbine-generator, interprets the signal based on the power generated by the turbine-generator in response to receiving the fluid flow.

The subject matter described in this disclosure can be implemented in particular implementations, so as to realize one or more of the following advantages. The systems and methods described are non-intrusive in the coiled tubing and do not negatively interfere with the pump rate capacity of the coiled tubing, as is typical for conventional electric wires used for wired communication. The systems and methods described can be implemented to perform wireless communication from surface equipment to downhole equipment over long distances, for example, distances of greater than <NUM>,<NUM> feet. The systems and methods described can be implemented to transmit digital data and commands to a downhole toolstring in a stimulation operation in which an electric wire would not be able to be used due to material limitations.

<FIG> depicts an example well <NUM> constructed in accordance with the concepts herein. The well <NUM> extends from the surface <NUM> through the Earth <NUM> to one more subterranean zones of interest <NUM> (one shown). The well <NUM> enables access to the subterranean zones of interest <NUM> to allow recovery (that is, production) of fluids to the surface <NUM> (represented by flow arrows in <FIG>) and, in some implementations, additionally or alternatively allows fluids to be placed in the Earth <NUM>. In some implementations, the subterranean zone <NUM> is a formation within the Earth <NUM> defining a reservoir, but in other instances, the zone <NUM> can be multiple formations or a portion of a formation. The subterranean zone can include, for example, a formation, a portion of a formation, or multiple formations in a hydrocarbon-bearing reservoir from which recovery operations can be practiced to recover trapped hydrocarbons. In some implementations, the subterranean zone includes an underground formation of naturally fractured or porous rock containing hydrocarbons (for example, oil, gas, or both). In some implementations, the well can intersect other types of formations, including reservoirs that are not naturally fractured. For simplicity's sake, the well <NUM> is shown as a vertical well, but in other instances, the well <NUM> can be a deviated well with a wellbore deviated from vertical (for example, horizontal or slanted), the well <NUM> can include multiple bores forming a multilateral well (that is, a well having multiple lateral wells branching off another well or wells), or both.

In some implementations, the well <NUM> is a gas well that is used in producing hydrocarbon gas (such as natural gas) from the subterranean zones of interest <NUM> to the surface <NUM>. While termed a "gas well," the well need not produce only dry gas, and may incidentally or in much smaller quantities, produce liquid including oil, water, or both. In some implementations, the well <NUM> is an oil well that is used in producing hydrocarbon liquid (such as crude oil) from the subterranean zones of interest <NUM> to the surface <NUM>. While termed an "oil well," the well not need produce only hydrocarbon liquid, and may incidentally or in much smaller quantities, produce gas, water, or both. In some implementations, the production from the well <NUM> can be multiphase in any ratio. In some implementations, the production from the well <NUM> can produce mostly or entirely liquid at certain times and mostly or entirely gas at other times. For example, in certain types of wells it is common to produce water for a period of time to gain access to the gas in the subterranean zone. The concepts herein, though, are not limited in applicability to gas wells, oil wells, or even production wells, and could be used in wells for producing other gas or liquid resources or could be used in injection wells, disposal wells, or other types of wells used in placing fluids into the Earth.

As shown in <FIG>, system <NUM> can be implemented to establish downhole wireless communication. The system <NUM> includes a surface sub-system <NUM> and a downhole sub-system <NUM> disposed within the well <NUM>. The system <NUM> is described in more detail later. The wellbore of the well <NUM> is typically, although not necessarily, cylindrical. All or a portion of the wellbore is lined with a tubing, such as casing <NUM>. The casing <NUM> connects with a wellhead at the surface <NUM> and extends downhole into the wellbore. The casing <NUM> operates to isolate the bore of the well <NUM>, defined in the cased portion of the well <NUM> by the inner bore <NUM> of the casing <NUM>, from the surrounding Earth <NUM>. The casing <NUM> can be formed of a single continuous tubing or multiple lengths of tubing joined (for example, threadedly) end-to-end. In <FIG>, the casing <NUM> is perforated in the subterranean zone of interest <NUM> to allow fluid communication between the subterranean zone of interest <NUM> and the bore <NUM> of the casing <NUM>. In some implementations, the casing <NUM> is omitted or ceases in the region of the subterranean zone of interest <NUM>. This portion of the well <NUM> without casing is often referred to as "open hole.

The wellhead defines an attachment point for other equipment to be attached to the well <NUM>. For example, <FIG> shows well <NUM> being produced with a Christmas tree attached to the wellhead. The Christmas tree includes valves used to regulate flow into or out of the well <NUM>. In particular, casing <NUM> is commercially produced in a number of common sizes specified by the American Petroleum Institute (the "API"), including <NUM>-<NUM>/<NUM>, <NUM>, <NUM>-<NUM>/<NUM>, <NUM>, <NUM>-<NUM>/<NUM>, <NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>-<NUM>/<NUM>, <NUM>, <NUM>-<NUM>/<NUM>, and <NUM> inches, and the API specifies internal diameters for each casing size.

<FIG> depicts an example system <NUM> that can be implemented in relation to the well <NUM>. The system <NUM> includes a surface sub-system <NUM> and a downhole sub-system <NUM>. The downhole sub-system <NUM> is coupled to the surface sub-system <NUM>. In some implementations, the surface sub-system <NUM> is coupled to the downhole sub-system <NUM> by a coiled tubing <NUM>. Fluid can be flowed from the surface sub-system <NUM> to the downhole sub-system <NUM> through the coiled tubing <NUM> to establish wireless communication between the sub-systems <NUM>, <NUM>.

<FIG> is a schematic flow diagram of the system <NUM>. The surface sub-system <NUM> includes a pump <NUM> configured to pump a fluid <NUM> from a container <NUM> downhole into a wellbore (for example, downhole into the well <NUM>). In some implementations, the container <NUM> is in the form of a sump, a tank, or barrels. The surface sub-system <NUM> includes a surface valve sub-assembly <NUM> that is fluidically coupled to the pump <NUM>. The surface valve sub-assembly <NUM> is configured to receive a first portion 299a of the fluid <NUM> pumped by the pump <NUM>. The surface valve sub-assembly <NUM> includes a first dump valve 221a. In some implementations, the surface valve sub-assembly <NUM> includes a second dump valve 221b. Including multiple dump valves (221a, 221b) can achieve redundancy of dump valves in operation and also increase the resolution of digital valves to achieve shaping of a signal waveform. For example, an arrangement of two dump valves 221a, 221b can be implemented to shape a sinusoidal waveform. Including additional dump valves (such as three or more dump valves) can improve smoothness (for example, resolution) of the sinusoidal waveform. In some implementations, the waveform can have a shape different from a sinusoidal waveform. In some implementations, the dump valves (221a, 221b and in some cases, dump valve(s) in addition to these) can have flow orifices that vary in shape depending on a target waveform shape. In some implementations, the first and second dump valves 221a, 221b are in a parallel flow configuration. That is, the first portion 299a of the fluid <NUM> pumped by the pump <NUM> is split between the first and second dump valves 221a, 221b, as opposed to a serial flow configuration in which the first portion 299a of the fluid <NUM> would flow through the first dump valve 221a and then through the second dump valve 221b. The surface valve sub-assembly <NUM> includes a surface controller <NUM> that is communicatively coupled to the first dump valve 221a. In some implementations, the surface controller <NUM> is communicatively coupled to the second dump valve 221b. The surface controller <NUM> is configured to adjust fluid flow through the first dump valve 221a. In some implementations, the surface controller <NUM> is configured to adjust fluid flow through the second dump valve 221b. The surface sub-system <NUM> includes a return line <NUM> in fluid communication with the first dump valves 221a. In some implementations, the return line <NUM> is in fluid communication with the second dump valve 221b. The return line <NUM> is configured to flow fluid from the first dump valve 221a, the second dump valve 221b, or both the first and second dump valves 221a, 221b to the container <NUM>.

The downhole sub-system <NUM> is configured to be disposed within the wellbore (for example, within a downhole portion of the well <NUM>). The downhole sub-system <NUM> includes a turbine-generator <NUM> configured to generate an output in response to receiving a second portion 299b of the fluid <NUM> pumped by the pump <NUM>. The output generated by the turbine-generator <NUM> can be, for example, a frequency output, a power output, a current output, or a voltage output. The turbine-generator <NUM> includes a turbine and a generator coupled together. The turbine receives fluid flow and rotates in response to receiving the fluid flow. The generator generates power in response to the rotation of the turbine. In some implementations, the turbine of the turbine-generator <NUM> is substituted by another hydraulic equipment, such as a vane motor. In some implementations, the downhole sub-system <NUM> includes a circulation valve <NUM> downstream of the turbine-generator <NUM>. The downhole sub-system <NUM> includes a downhole controller <NUM> coupled to the turbine-generator <NUM>. In implementations in which the downhole sub-system <NUM> includes the circulation valve <NUM>, the downhole controller <NUM> is communicatively coupled to the circulation valve <NUM>. In some implementation, the downhole controller <NUM> is configured to adjust fluid flow through the circulation valve <NUM> at least based on the output generated by the turbine-generator <NUM>. In some implementations, the downhole sub-system <NUM> is coupled to the surface valve sub-assembly <NUM>. In some implementations, the coiled tubing <NUM> couples the pump <NUM> to the turbine-generator <NUM>.

In some implementations, the surface controller <NUM> includes a surface processor and a surface computer-readable storage medium coupled to the surface processor. The surface computer-readable storage medium stores programming instructions for execution by the surface processor, and the programming instructions instruct the surface processor to perform operations. In some implementations, the downhole controller <NUM> includes a downhole processor and a downhole computer-readable storage medium coupled to the downhole processor. The downhole computer-readable storage medium stores programming instructions for execution by the downhole processor, and the programming instructions instruct the downhole processor to perform operations. An example of the surface controller <NUM> and the downhole controller <NUM> is provided in <FIG> and is described in more detail later.

The split of the fluid <NUM> pumped by the pump <NUM> into the first portion 299a and the second portion 299b can be controlled by the surface controller <NUM>. For example, the surface controller <NUM> is configured to adjust the percent openings of the first and second dump valves 221a, 221b, thereby controlling the flow rate of the first portion 299a. In some implementations, the second portion 299b is a remaining balance of the fluid <NUM> in relation to the first portion 299a. Controlling the flow rate of the first portion 299a indirectly affects the flow rate of the second portion 299b based on hydraulics. For example, the surface controller <NUM> can adjust the percent openings of the first and second dump valves 221a, 221b, such that the flow rate of the first portion 299a increases and the flow rate of the second portion 299b decreases. For example, the surface controller <NUM> can adjust the percent openings of the first and second dump valves 221a, 221b, such that the flow rate of the first portion 299a decreases and the flow rate of the second portion 299b increases. In some implementations, the surface controller <NUM> is configured to adjust a split of the first portion 299a between the first dump valve 221a and the second dump valve 221b.

In some implementations, the surface controller <NUM> is configured to adjust an amount of the first portion 299a by adjusting the fluid flow through each of the first and second dump valves 221a, 221b, such that a sinusoidal signal is hydraulically transmitted to the downhole sub-system <NUM> via the second portion 299b. For example, the surface controller <NUM> can adjust the amount of the first portion 299a by adjusting the fluid flow through each of the first and second dump valves 221a, 221b in such a manner that the flow rate of the second portion 299b alternates between increasing and decreasing in an oscillating behavior similar to a sinusoidal curve. In some implementations, the surface controller <NUM> is configured to modulate the sinusoidal signal that is hydraulically transmitted to the downhole sub-system <NUM> via the second portion 299b. For example, the sinusoidal signal can be modulated with frequency shift-keying (FSK), phase-shift keying (PSK), a pulse position modulation (PPM) scheme, into Morse code, or any other conventional signal modulation scheme. In some implementations, a "data packet" hydraulically transmitted to the downhole sub-system <NUM> via the second portion 299b includes a sync bits component, a payload data component, and a checksum component. The sync bits components can be used to prepare the recipient (for example, the turbine-generator <NUM> communicatively coupled to the downhole controller <NUM>) of an incoming data packet. The payload data component can include a command signal allocated in a predetermined bits string and sequence. The checksum component can include a polynomial division value of the payload data bit pattern, which can in turn be used to control the integrity of the received data packet.

In some implementations, the turbine-generator <NUM> is configured to receive the sinusoidal signal via the second portion 299b and change the output in response to receiving the sinusoidal signal. In some implementations, the downhole controller <NUM> is configured to process the change in the output and adjust fluid flow through the circulation valve <NUM> at least based on processing the change in the output. For example, in cases where the output generated by the turbine-generator <NUM> is a frequency output, the downhole controller <NUM> can be configured to process the change in the frequency output for controlling an alternating electric machine. For example, in cases where the output generated by the turbine-generator <NUM> is a current output, the downhole controller <NUM> can be configured to process the change in the current output for controlling a continuous load of an electric machine. In some implementations, the downhole controller <NUM> is configured to process the change in the output of the turbine-generator <NUM>, such that a power output of the turbine-generator <NUM> is maintained to be greater than a minimum power output threshold. The minimum power output threshold can be defined, for example, as the minimum amount of power necessary for operating the integrated electronic circuitry of a downhole tool string. In some implementations, the minimum power output threshold is in a range of from about <NUM> milliwatt (mW) to about <NUM> watts (W), from about <NUM> mW to about <NUM> W, from about <NUM> mW to about <NUM> W, from about <NUM> mW to about <NUM> W, from about <NUM> mW to about <NUM> W, or from about <NUM> mW to about <NUM> W. In some implementations, the downhole controller <NUM> is configured to de-modulate the sinusoidal signal that is hydraulically transmitted to the downhole sub-system <NUM> via the second portion 299b.

<FIG> is a block diagram of an implementation of the downhole controller <NUM>. In some implementations, the downhole controller <NUM> is a proportional-integral-derivative (PID) controller. The r(t) is the target process value (also referred as set point), and y(t) is the measured process value (also referred as operating point). In some implementations, the downhole controller <NUM> implements a feedback loop and calculates error value e(t) as the difference between the set point (e(t)) and the operating point (y(t)). The downhole controller <NUM> adjusts u(t) to minimize e(t) over time. The proportional component of the PID controller is proportional to the value of e(t). The integral component of the PID controller accounts for past values of e(t) and integrates them over time. The derivative component of the PID controller estimates a future value of e(t) based on a rate of change of e(t). The value for u(t) is calculated based on these three components and adjusted to minimize e(t), so that the operating point is maintained in proximity to the set point. In some implementations, r(t) passes through a lowpass filter. In some implementations, the downhole controller <NUM> adjusts u(t), such that the power output (for example, y(t)) is maintained to be greater than a minimum power output threshold. For example, the downhole controller <NUM> calculates the difference between the target voltage output turbine-generator <NUM> and the actual measured value and adjusts the load to minimize this difference.

The downhole controller <NUM> is configured to maintain steady power production while the low frequency sinusoidal signal causes low frequency fluctuations on the output generated by the turbine-generator <NUM>. For example, low frequency fluctuations can typically range from about <NUM> Hertz (Hz) to about <NUM>. The downhole controller <NUM> is slower than the low frequency sinusoidal signal but fast enough to react to actual changes in operating conditions within a reasonable timeframe (for example, in a range of from about <NUM> minute to <NUM> minutes) to enable steady power supply to other onboard equipment that may be included in the downhole sub-system <NUM>. For example, the response time for the downhole controller <NUM> is longer than the duration of (that is, wavelength) of the low frequency sinusoidal signal, such that the downhole controller <NUM> does not interfere with and compensates for the load of the turbine-generator <NUM>, resulting in a steady voltage output of the turbine-generator <NUM>. The lowpass filtering with a long time constant and a hard limit can be implemented to ensure steady power production. In some implementations, the time constant (τ) is calculated as <MAT>. For example, for a <NUM> filter, the time constant is about <NUM> seconds. In some implementations, the hard limit is an absolute minimum voltage that is set to be greater than the voltage of a battery of the downhole sub-system <NUM> in order to protect the battery and avoid draining/wasting energy while the turbine-generator <NUM> produces power. For example, the hard limit can be <NUM> volts (V) for a <NUM> V battery pack, such as two <NUM> V lithium cells in series.

<FIG> and <FIG> are plots of various voltages against different time scales relating to the turbine-generator <NUM> and the downhole controller <NUM>. <FIG> depicts data associated with a startup sequence, while <FIG> depicts data associated with operation at steady state a time period after startup when the process has stabilized. As seen in both plots, low frequency behavior is exhibited by the voltage output of the turbine-generator <NUM>, and the operating point (controller output) is maintained to ensure steady power production. In both plots, "Controller Input" can be considered e(t), "Controller Output" can be considered y(t), and "Generator Voltage" can be considered u(t). As seen in the plot of <FIG>, the voltage output of the turbine-generator <NUM> exhibits the low frequency sinusoidal signal, while the downhole controller <NUM> is stable and does not affect the load of the turbine-generator <NUM>. This effect shown in <FIG> is a result of the downhole controller <NUM> operating more slowly than the low frequency sinusoidal signal (described previously).

<FIG> is a flow chart of an example method <NUM> for wireless communication from surface equipment to downhole equipment. The method <NUM> can be implemented, for example, by system <NUM>. At step <NUM>, a first portion of a fluid (such as the first portion 299a of the fluid <NUM>) is flowed from a container (such as the container <NUM>) to a surface valve sub-assembly (such as the surface valve sub-assembly <NUM>). As mentioned previously, the surface valve sub-assembly includes the first dump valve 221a, the second dump valve 221b, the surface controller <NUM>, and the return line <NUM>. The surface controller <NUM> is communicatively coupled to the first and second dump valves 221a, 221b. The return line <NUM> is in fluid communication with the first and second dump valves 221a, 221b.

At step <NUM>, fluid flow through each of the first and second dump valves 221a, 221b is adjusted by the surface controller <NUM>. In some implementations, the first and second dump valves 221a, 221b are in a parallel flow configuration. In some implementations, the method <NUM> includes adjusting, by the surface controller <NUM>, a split of the first portion 299a between the first dump valve 221a and the second dump valve 221b. In some implementations, adjusting the fluid flow through each of the first and second dump valves 221a, 221b at step <NUM> includes adjusting the fluid flow through each of the first and second dump valves 221a, 221b, such that a sinusoidal signal is hydraulically transmitted to the downhole sub-system <NUM> via a second portion (such as the second portion 299b) of the fluid <NUM>. In some implementations, the method <NUM> includes modulating, by the surface controller <NUM>, the sinusoidal signal that is hydraulically transmitted to the downhole sub-system <NUM> via the second portion 299b. At step <NUM>, the first portion 299a of the fluid <NUM> is flowed by the return line <NUM> back to the container <NUM>.

At step <NUM>, the second portion 299b of the fluid <NUM> is flowed from the container <NUM> to a downhole sub-system disposed within a wellbore (such as the downhole sub-system <NUM> disposed within the well <NUM>). As mentioned previously, the downhole sub-system <NUM> includes the turbine-generator <NUM> and the downhole controller <NUM>. The downhole controller <NUM> is coupled to the turbine-generator <NUM>. In some implementations, flowing the second portion 299b to the downhole sub-system <NUM> at step <NUM> includes flowing the second portion 299b through a coiled tubing (such as the coiled tubing <NUM>) that is fluidically coupled to the turbine-generator <NUM>. At step <NUM>, the second portion 299b of the fluid <NUM> is received by the turbine-generator <NUM>.

At step <NUM>, an output (for example, a frequency output, a power output, a current output, or a voltage output) is generated by the turbine-generator <NUM> in response to receiving the second portion 299b of the fluid <NUM> at step <NUM>. At step <NUM>, the output (and/or a change in the output) from the turbine-generator <NUM> (generated at step <NUM>) is received by the downhole controller <NUM>. In some implementations, receiving the second portion 299b by the turbine-generator <NUM> at step <NUM> includes receiving the sinusoidal signal via the second portion 299b and changing the output generated by the turbine-generator <NUM> at step <NUM> in response to receiving the sinusoidal signal. In some implementations, the method <NUM> includes de-modulating, by the downhole controller <NUM>, the sinusoidal signal that is hydraulically transmitted to the downhole sub-system <NUM> via the second portion 299b. At step <NUM>, the downhole controller <NUM> transmits a signal to control another component of the downhole sub-system <NUM> (such as the circulation valve <NUM> or another component of the downhole toolstring) in response to receiving the output from the turbine-generator <NUM> at step <NUM>. Power generation by the turbine-generator <NUM> remains steady throughout steps <NUM>, <NUM>, and <NUM>.

In some implementations, the downhole sub-system <NUM> includes a circulation valve (such as the circulation valve <NUM>) downstream of the turbine-generator <NUM> and communicatively coupled to the downhole controller <NUM>. In some implementations, the method <NUM> includes processing, by the downhole controller <NUM>, the change in the output, for example, generated by the turbine-generator <NUM> at step <NUM> in response to receiving the sinusoidal signal. In some implementations, the method <NUM> includes adjusting, by the downhole controller <NUM>, fluid flow through the circulation valve <NUM> at least based on the processing of the change in the output, for example, generated by the turbine-generator <NUM> at step <NUM> in response to receiving the sinusoidal signal. In some implementations, processing, by the downhole controller <NUM>, the change in the output includes processing the change in the output, such that the power output of the turbine-generator <NUM> is maintained to be greater than a minimum power output threshold.

<FIG> is a block diagram of an example controller <NUM> used to provide computational functionalities associated with described algorithms, methods, functions, processes, flows, and procedures, as described in this specification, according to an implementation. For example, each of the surface controller <NUM> and the downhole controller <NUM> can be implementations of the controller <NUM>. The illustrated controller <NUM> is intended to encompass any computing device such as a server, desktop computer, laptop/notebook computer, one or more processors within these devices, or any other processing device, including physical or virtual instances (or both) of the computing device. Additionally, the controller <NUM> can include a computer that includes an input device, such as a keypad, keyboard, touch screen, or other device that can accept user information, and an output device that conveys information associated with the operation of the computer <NUM>, including digital data, visual, audio information, or a combination of information.

The controller <NUM> includes a processor <NUM>. Although illustrated as a single processor <NUM> in <FIG>, two or more processors may be used according to particular needs, desires, or particular implementations of the controller <NUM>. Generally, the processor <NUM> executes instructions and manipulates data to perform the operations of the controller <NUM> and any algorithms, methods, functions, processes, flows, and procedures as described in this specification.

The controller <NUM> can also include a database <NUM> that can hold data for the controller <NUM> or other components (or a combination of both) that can be connected to the network. Although illustrated as a single database <NUM> in <FIG>, two or more databases (of the same or combination of types) can be used according to particular needs, desires, or particular implementations of the controller <NUM> and the described functionality. While database <NUM> is illustrated as an integral component of the controller <NUM>, database <NUM> can be external to the controller <NUM>.

The controller <NUM> includes a memory <NUM> that can hold data for the controller <NUM> or other components (or a combination of both) that can be connected to the network. Although illustrated as a single memory <NUM> in <FIG>, two or more memories <NUM> (of the same or combination of types) can be used according to particular needs, desires, or particular implementations of the controller <NUM> and the described functionality. While memory <NUM> is illustrated as an integral component of the controller <NUM>, memory <NUM> can be external to the controller <NUM>. The memory <NUM> can be a transitory or non-transitory storage medium.

The memory <NUM> stores controller-readable instructions executable by the processor <NUM> that, when executed, cause the processor <NUM> to perform operations, such as adjust fluid flow through each of the first and second dump valves 221a, 221b. The controller <NUM> can also include a power supply <NUM>. The power supply <NUM> can be hard-wired. There may be any number of controllers <NUM> associated with, or external to, a computer system containing controller <NUM>, each controller <NUM> communicating over the network. Further, the term "client," "user," "operator," and other appropriate terminology may be used interchangeably, as appropriate, without departing from this specification. Moreover, this specification contemplates that many users may use one controller <NUM>, or that one user may use multiple controllers <NUM>.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this specification in the context of separate implementations can also be implemented, in combination, in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

As used in this disclosure, the terms "a," "an," or "the" are used to include one or more than one unless the context clearly dictates otherwise. The term "or" is used to refer to a nonexclusive "or" unless otherwise indicated. The statement "at least one of A and B" has the same meaning as "A, B, or A and B. " In addition, it is to be understood that the phraseology or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.

As used in this disclosure, the term "about" or "approximately" can allow for a degree of variability in a value or range, for example, within <NUM>%, within <NUM>%, or within <NUM>% of a stated value or of a stated limit of a range.

As used in this disclosure, the term "substantially" refers to a majority of, or mostly, as in at least about <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or at least about <NUM>% or more.

Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of "<NUM>% to about <NUM>%" or "<NUM>% to <NUM>%" should be interpreted to include about <NUM>% to about <NUM>%, as well as the individual values (for example, <NUM>%, <NUM>%, <NUM>%, and <NUM>%) and the sub-ranges (for example, <NUM>% to <NUM>%, <NUM>% to <NUM>%, <NUM>% to <NUM>%) within the indicated range. The statement "X to Y" has the same meaning as "about X to about Y," unless indicated otherwise. Likewise, the statement "X, Y, or Z" has the same meaning as "about X, about Y, or about Z," unless indicated otherwise.

Moreover, the separation or integration of various system modules and components in the previously described implementations should not be understood as requiring such separation or integration in all implementations, and it should be understood that the described components and systems can generally be integrated together or packaged into multiple products.

Claim 1:
A system (<NUM>) comprising:
i) a surface sub-system (<NUM>) comprising
a pump (<NUM>) configured to pump a fluid from a container (<NUM>), downhole into a wellbore; and
a surface valve sub-assembly (<NUM>) fluidically coupled to the pump and configured to receive a first portion (299a) of fluid (<NUM>) pumped by the pump, the surface valve sub-assembly comprising:
a dump valve (<NUM>),
a surface controller (<NUM>) communicatively coupled to the dump valve, the surface controller configured to adjust fluid flow through the dump valve, and
a return line (<NUM>) in fluid communication with the dump valve, the return line configured to flow fluid from the dump valve to the container; and
ii) a downhole sub-system (<NUM>) coupled to the surface valve sub-assembly and configured to be disposed within the wellbore, the downhole sub-system comprising
a turbine-generator (<NUM>) configured to generate an output in response to receiving a second portion of the fluid pumped by the pump, and
a downhole controller (<NUM>) coupled to the turbine-generator.