Method for operating a drilling system

Abstract

A method for operating a drilling system includes a mud pump disposed on the surface and a drill string having a bottom hole assembly (BHA) in a wellbore. The method includes turning the mud pump on and off according to a predetermined sequence to cause the mud flow in the wellbore to fluctuate between a high flow rate and a low flow rate. A mud pulse generator in the BHA detects the fluctuations in the mud flow and generates a binary signal accordingly. The mud pulse generator then transmits the binary signal to a measurement while drilling (MWD) tool in the BHA. The binary signal executes one or more firmware in the MWD tool.

Description

[0001] This application is a divisional application of Chinese patent application No. 201910369564.5, entitled “System and method for downhole signal transmission,” filed on May 6, 2019. Technical Field

[0002] The present disclosure relates generally to communication systems in drilling operations, and more particularly to systems and methods for generating and transmitting data signals between the surface and downhole in oil and gas exploration. Background Art

[0003] Drilling operations in oil and gas exploration involve driving a drill bit into the ground to form a wellbore (i.e., a wellbore) from which oil and / or natural gas is extracted. The drill bit is mounted at the distal end of a drill string, which extends from a derrick on the surface into the wellbore. The drill string is formed by connecting a series of drill pipes together. A bottomhole assembly (BHA) is mounted above the drill bit in the drill string.

[0004] The BHA contains instrumentation that collects and / or transmits information about the drilling tool, wellbore conditions, and formations to the surface. This information is used to determine drilling conditions, such as the drill bit's wander, inclination, and azimuth, which in turn is used to calculate the wellbore trajectory. Real-time data is crucial for monitoring and controlling drilling operations, either automatically or through operator intervention.

[0005] Technologies used to transmit information within the wellbore, known as telemetry, are used to transmit information from the BHA to the surface for further analysis. One known telemetry method is mud pulse telemetry, which uses drilling mud to transmit information from downhole to the surface. Drilling mud, also known as drilling fluid, is pumped from the surface through a conduit within the drill string and returned to the surface through the annulus between the drill string and the wellbore.

[0006] The flow of drilling mud through the drill string can be modulated (i.e., encoded) by a mud pulse generator to induce changes in pressure and / or flow rate. The changes in pressure or flow rate are captured by corresponding sensors at or near the surface and decoded using decoding software to recover the downhole information. In systems using mud pulse telemetry, the mud pulse generator can be part of the BHA.

[0007] The specific design of a mud pulse generator can vary, but the basic principle is that it generates pressure pulses by restricting the flow path of the mud stream in the wellbore. The mud stream is compressed or released in the drill string at a specific time sequence, encoding data in the modulated pressure pulses into the mud stream. The modulated pressure pulses propagate through the mud stream to the surface, where they are detected and decoded, recovering the original data.

[0008] The mud pumps that power the mud flow are large positive displacement pumps that move pistons back and forth within cylinders, simultaneously opening and closing intake and exhaust valves. A typical mud pump has three pistons connected to a common drive shaft. These pistons are offset 120 degrees from each other to minimize pressure variations. Dampers are used to reduce pulsations in the mud flow.

[0009] In addition to mud pulse telemetry, wired drill pipe telemetry is also frequently used in drilling operations. In wired drill pipe telemetry, the drill pipe in the drill string has a communication cable embedded in the wall of the drill pipe. When the drill pipe is connected together, the sections of communication cable form a continuous communication cable along the drill string from the BHA to the surface. The advantage of wired telemetry is that data transmission through the cable is bidirectional and much faster than mud pulse telemetry. However, connecting the two sections of communication cable at the joint between the two drill pipes requires a complex and expensive coupling device. When drilling deep wells, many such joints are required. A break in the communication cable at any joint will render the telemetry ineffective, requiring expensive repairs. For this and other reasons, mud pulse telemetry technology is still widely used in drilling operations.

[0010] Unlike two-way wired telemetry, mud pulse telemetry typically telemeters data from downhole to the surface.A method and system are needed that can telemeter signals from the surface downhole to a tool in the wellbore. Summary of the Invention

[0011] The present disclosure provides a method for operating a drilling system, the drilling system comprising a mud pump disposed on the ground and a drill string having a bottom hole assembly (BHA) in a wellbore. In one embodiment, the method comprises turning the mud pump on or off according to a predetermined sequence so that the mud flow in the wellbore fluctuates in response to the predetermined sequence. The mud flow in the wellbore fluctuates between a high flow rate and a low flow rate (including a flow rate of substantially zero). A mud pulse generator in the bottom hole assembly detects the fluctuations in the mud flow and generates a binary signal accordingly. The mud pulse generator then sends the binary signal to a measurement while drilling (MWD) tool in the bottom hole assembly. The binary signal is used to execute one or more firmware in the measurement while drilling tool.

[0012] In some embodiments of the present disclosure, the binary signal is encoded with an instruction, and the MWD tool detects and decodes the binary signal to obtain the instruction, which identifies one of the one or more firmware files for execution.

[0013] In some other embodiments, the MWD tool includes one or more memories, a microprocessor, and an input / output communication port for interfacing with the mud pulse generator. The one or more firmware are stored in the one or more memories and executed by the microprocessor. The memory may be a non-volatile memory.

[0014] The one or more firmware disclosed herein include a front-end firmware and one or more task firmwares. The front-end firmware selects one of the one or more task firmwares to execute at a certain moment, and each task firmware operates multiple sensors in the MWD tool under a different set of conditions.

[0015] In other embodiments, the mission firmware controls parameters in the MWD tool, which may include the number of sensors, data sampling frequency, data logging frequency, the amount of data sent to the surface, the amount of data stored locally on the MWD tool, and the like.

[0016] The mud pulse generator disclosed herein includes one or more flow sensors that sense mud flow, determine the state of the mud flow as on or off, and output a binary signal to the MWD tool.

[0017] The present disclosure also provides a method for controlling an MWD tool in a bottom hole assembly in a wellbore. In this method, multiple firmware programs are installed in the MWD tool. The firmware programs are preprogrammed to perform multiple tasks. A mud pump on the surface is turned on or off according to a predetermined sequence. Mud flow in the wellbore fluctuates in response to the mud pump, and this is determined to be on or off, generating a binary signal. This binary signal is then transmitted to the MWD tool.

[0018] The on or off state of the mud flow is determined by a mud flow sensor in the mud pulse generator, and a mud flow sensor driving circuit outputs the binary signal to the MWD tool.

[0019] The present disclosure also provides a high-temperature drilling method. The method includes installing multiple firmware in an MWD tool in a bottom hole assembly in a drill string. The temperature in the wellbore increases with increasing depth of the wellbore. The maximum temperature of the bottom hole assembly in the wellbore can be in the range of 100°C to 200°C or higher. One of the firmware is executed when the temperature is equal to or below a first threshold (e.g., 120°C or 150°C). A different firmware is executed when the temperature of the bottom hole assembly exceeds a second threshold (e.g., 180°C or 200°C). Optionally, one or more firmware are executed at a temperature between the first threshold and the second threshold.

[0020] The switch from executing one firmware to executing another is accomplished by turning the mud pump on or off according to a pre-programmed sequence. In doing so, the mud flow can be encoded with one or more command signals, known as flow commands. The MWD tool receives the flow commands and performs the corresponding tasks according to the flow commands. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more complete understanding of the embodiments of the present disclosure, reference may be made to the following detailed description in conjunction with the accompanying drawings, in which:

[0022] Figure 1 is a schematic illustration of a drill stand of the present disclosure.

[0023] Figure 2 is an exemplary coded waveform diagram of a mud flow.

[0024] Figure 3 is a schematic diagram showing the functional blocks and data structures of firmware embedded on the MWD tool; and

[0025] Figure 4 is a schematic flow chart showing the operation of the firmware in the MWD tool. DETAILED DESCRIPTION

[0026] Reference will now be made in detail to several embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. It should be noted that, where applicable, similar or like reference numerals have been used in the drawings and may indicate similar or like functionality. The drawings depict embodiments of the present disclosure for illustrative purposes only. Those skilled in the art will readily appreciate from the following description that alternative embodiments of the structures and methods shown herein may be employed without departing from the principles of the present disclosure as described herein.

[0027] Figure 1 The diagram schematically illustrates a drilling operation. A drill string 2 extends from a derrick 1 on the surface into a wellbore 3. A drill bit 4 is mounted at the distal end of the drill string 2. A BHA 5 is mounted above the drill bit 4. A mud pump 6 pumps mud from a mud tank 7 downhole through the drill string 1. The mud is then circulated through the annulus between the drill string 1 and the wellbore 3 and returned to the mud tank 7.

[0028] The BHA 5 includes a mud pulse generator 10, a mud motor (not shown), a measurement while drilling (MWD) instrument (not shown), and a logging while drilling (LWD) instrument (not shown). In this disclosure, the MWD instrument and the LWD instrument are collectively referred to as the MWD tool. The MWD tool is powered by a mud motor, a battery, or both a mud motor and a battery (not shown). The MWD tool has one or more internal memories, a microprocessor, software and / or firmware with pre-programmed instructions installed on the memory, and input / output communication ports for communicating with other tools in the BHA (e.g., the mud pulse generator). The firmware controls the operation of the MWD tool, such as the operation of the sensors.

[0029] The mud pulse generator 10 communicates with an MWD digital signal processor (DSP) 11. The MWD DSP 11 is connected to a number of measurement sensors 12 that measure formation and / or directional information, including gamma ray detectors that measure naturally occurring gamma rays in the formation, directional sensors that monitor inclination and azimuth, and more. The MWD DSP 11 sends coded instructions to the mud pulse generator 10, which in turn generates pressure pulses that propagate uphole. A pressure sensor 8 is installed in the mud flow path and detects the pressure pulses. It transmits the mud pulse signals to a surface data acquisition system 9, which decodes the pressure pulse signals to obtain downhole information.

[0030] exist Figure 1 In one embodiment, the mud pulse generator 10 includes a pulse generator driver (not shown) that controls a mechanism for restricting or opening a mud flow path, such as a solenoid valve or a swing shear valve (not shown). The pulse generator may also include a flow sensor (not shown) for detecting mud flow. In one embodiment, the flow sensor includes one or more vibration-sensitive devices, such as accelerometers. The flow sensor determines whether drilling mud is flowing based on the acceleration force on the accelerometer and outputs a binary signal. As a result, the modulated mud flow carries the binary signal, which in turn carries the command from the surface to the wellbore.

[0031] The flow sensor circuitry (not shown) may include memory, a microprocessor, and input / output communication ports to interface with the MWD DSP firmware and / or with other tools in the BHA. Figure 1 In the embodiment described herein, MWD DSP firmware controls the mud pulse generator 10 and is stored in onboard memory and executed by the microprocessor. The flow sensor circuitry can be located on the same printed circuit board as the pulser driver circuitry. Independent of the control signal from the MWD tool to the mud pulse generator 10, the flow sensor circuitry determines whether mud flow is on or off and sends a binary signal to the MWD DSP accordingly.

[0032] Figure 2 An exemplary mud flow binary signal output from a flow sensor is shown. It defines an initial OFF time t1, followed by three ON periods within a time period t2, followed by another OFF period t3. This combination of binary signals serves as a command signal for the MWD tool and executes the firmware installed in the memory of the MWD tool. Various combinations of such ON and OFF periods during a specific time interval constitute different flow commands. For example, Figure 2 The instruction signal may be a flow instruction that initiates switching between different tasks, ie, an instruction to execute certain firmware installed in the MWD tool. More details are provided later in this disclosure.

[0033] Figure 3 and 4 FIG1 shows the firmware and the execution of the firmware in the MWD system. Figure 3 As shown, front-end firmware and multiple task firmware (Task Firmware 1 through Task Firmware N) are stored in non-volatile memory, such as ROM, EPRROM, or flash memory, within the MWD system. The firmware can be stored in different portions of the same memory within the microprocessor, or in different interconnected memories throughout the MWD tool. The front-end firmware and task firmware can receive and / or decode command signals, or stream commands, from the mud pulse generator. When the task firmware executes a specific task (e.g., for low-temperature operation versus high-temperature operation), the front-end firmware determines which specific task the stream command is directed to.

[0034] Figure 3 Also shown is a data structure in memory, including an index table containing IDs and addresses for the front-end firmware and task firmware, as well as pointers to the memory portion where the corresponding firmware is stored. The index table can be part of the front-end firmware, which determines the task to be executed (i.e., the active task) and its active task ID. The active task ID identifies the address (firmware address) of that particular task among tasks 1 to N and points to the portion of memory (firmware area) where the code for the corresponding task is stored and executes that code.

[0035] The current task can be the current task currently running, or the current task before the system is powered off or reset. In one embodiment, the current task ID is stored in a memory. When the stream instruction does not command a task change, the front-end firmware reads the current task ID and selects the corresponding task firmware from task firmware 1 to N. Then, the front-end firmware enters a sleep mode. When the stream instruction requests a change in the current task, for example, from task 1 to task 2, the front-end firmware starts the process of completing the switch.

[0036] In one embodiment, the front-end firmware assigns tasks to various task firmwares. While the task firmware is running, the front-end firmware can be in sleep mode. When a stream instruction requests a switch, the currently running task firmware initiates a reset to restart the front-end firmware, so that the front-end firmware can assign tasks to different task firmwares.

[0037] refer to Figure 4 Further details of the operation can be provided. Figure 4 FIG. 1 is a simplified flow chart showing an embodiment of a method for executing front-end firmware and task firmware. Figure 4 As shown, in step 401, start the front-end firmware, and in step 402, run the front-end task, and read the current task ID (step 403) that currently writes in the current task ID memory. In step 404, the front-end firmware determines whether the current task ID is valid. If valid, then the front-end firmware finds the address of the corresponding task firmware, and from there finds the corresponding task firmware area to execute task firmware (step 405). If the current ID is invalid, then the front-end firmware reads the stream instruction (step 406). If the stream instruction is valid (the stream instruction that matches with the preset signal sequence), then the front-end firmware decodes the stream instruction, and determines the content of the stream instruction (step 407). Once the stream instruction is decoded, the front-end firmware just distributes the corresponding task and executes the corresponding task firmware (step 408). If the stream instruction is invalid, then the front-end firmware enters the "self-test / debug" mode (step 409), and returns to read the stream instruction.

[0038] During normal operation, one of the task firmware is being executed. When a different task is required, the flow instruction (e.g. Figure 2 ) is sent to the front-end firmware and task firmware to notify the task firmware that a switch is waiting. Then, a second stream instruction is sent to the MWD tool to notify which new task is about to be switched to. In this process, the task firmware detects the stream instruction (step 501) and determines whether the stream instruction is valid (step 502). If the stream instruction is invalid, the task firmware continues to run the current task and monitors the stream instruction until it receives a valid stream instruction (step 503). Once it is determined that the stream instruction is valid, the task firmware decodes the stream instruction (step 504) to obtain the ID of the task being switched to, writes the new task ID into the memory as the current ID (step 505), and then restarts the microprocessor to terminate the current task and transfers control to the front-end firmware (step 506).

[0039] In some embodiments of the present disclosure, exemplary tasks run by the task firmware are related to downhole conditions, such as temperature and pressure in the wellbore. For example, Task 1 is specified to run multiple sensors at a temperature equal to or below a specific temperature (e.g., 120°C or 150°C). These sensors can be for temperature, pressure, flow rate, azimuth, inclination, total H field, total G field, magnetic inclination, and so on. Task 1 defines conditions such as which sensor is running, sampling frequency, data logging frequency, data transmitted to the surface in real time, data stored in internal memory, etc. When the downhole temperature reaches a threshold (e.g., 180°C), Task 2 is activated. Task 2 can change the type, number and / or location of sensors from Task 1, as well as other conditions of the sensors. When the downhole temperature exceeds 200°C, Task 2 switches to Task 3 and executes another set of conditions.

[0040] The change in mission can be initiated by an operator monitoring downhole temperatures. When the temperature reaches a threshold level, the operator turns the mud pumps on or off according to a sequence that encodes the mud flow with the appropriate flow command, which switches the active mission from Mission 1 to Mission 2 or vice versa.

[0041] In other embodiments, the system can be used to test different versions of mission firmware. In one such example, two different versions of firmware written for Mission 3, designed to operate at or above 200°C, can be installed in an MWD tool. During drilling operations, operators can switch the mud pump from one version of firmware to the other while the BHA remains downhole, avoiding a costly trip.

[0042] Other scenarios where switching tasks is necessary include the battery pack state (e.g., fully charged vs. depleted) and the formation state (relatively uniform formation vs. rapidly changing formation). The former requires adjusting sensor conditions (e.g., number of sensors, sampling frequency) to reduce power consumption, while the latter may require increasing the sampling frequency.

[0043] Although the present disclosure has been described in relation to certain preferred embodiments of the present disclosure in the foregoing description, and many details have been set forth for illustrative purposes, it is obvious to those skilled in the art that the present disclosure is susceptible to change and that other details described herein may be significantly varied without departing from the basic principles of the present disclosure. In addition, it should be understood that the structural features or method steps shown or described in any one embodiment herein may also be used in other embodiments.

Claims

1. A method for operating a drilling system, wherein the drilling system includes a mud pump disposed on the surface and a drill string having a bottom hole assembly disposed in a wellbore, the method comprising: turning mud pumps on and off according to a predetermined sequence so that mud flow in the wellbore fluctuates in response to the predetermined sequence; detecting mud flow in the wellbore using a mud pulse generator in the bottom hole assembly to generate a binary signal; and The binary signal is sent to a measurement while drilling tool in the bottom hole assembly, wherein the binary signal executes one or more firmware in the measurement while drilling tool, wherein, The one or more firmwares include front-end firmware and one or more task firmwares, wherein each of the one or more task firmwares operates a plurality of sensors in the measurement while drilling tool under a unique set of conditions, and the front-end firmware selects one of the one or more task firmwares for execution, The unique set of conditions includes one or more parameters selected from the group consisting of the number of sensors in operation, data sampling frequency, data logging frequency, data sent to the surface, or data stored locally on the measurement while drilling tool, The tasks executed by the task firmware are related to downhole conditions, such as the temperature and pressure in the wellbore. Tasks are switched by switching between different versions of the task firmware executed in different temperature ranges.

2. The method according to claim 1, characterized in that Instructions are encoded in the binary signal, and the measurement while drilling tool detects and decodes the binary signal to obtain the instructions.

3. The method according to claim 2, characterized in that The measurement while drilling tool includes one or more memories, a microprocessor, and an interface with the mud pulse generator, wherein the one or more firmware are stored in the one or more memories and executed by the microprocessor.

4. The method according to claim 1, wherein The plurality of sensors monitor one or more drilling conditions selected from the group consisting of temperature, pressure, flow rate, azimuth, inclination, total H-field, total G-field, or magnetic inclination.

5. The method according to claim 1, characterized in that The mud pulse generator includes one or more flow sensors, which sense mud flow, determine whether the mud flow is on or off, and output the binary signal to the measurement while drilling tool.

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