TECHNICAL FIELD

The present invention relates to the technical field of oil and gas drilling and production, particularly to a method for controlling a toe-end sliding sleeve of a horizontal well based on efficient decoding communication.

BACKGROUND ART

As an important means of increasing production, the fracturing technology is widely used in the exploitation of petroleum and natural gas. To produce more effective fracturing networks and form more effective circulation channels for oil and natural gas, the staged fracturing technology came into being. After the cementing is completed, a wellbore must undergo a pressure test for testing the wellbore sealing performance and cementing quality. However, the traditional sliding sleeve must be opened in advance for subsequent fracturing needs, so full-wellbore pressure testing operations cannot be performed.

In the existing patented technical solutions, the Chinese patent (Application No: 201220389849.9) discloses a tool that enables a fracturing ball to pass through by deforming a special material; the Chinese patent (Application No. 201820152248.3) discloses that a rupture disk is used to perform a wellbore pressure test and open a sliding sleeve; the Chinese patents (Application No. 201811289313.8 and Application No. 201821782468.0) disclose that a delayed start method is used to control a sliding sleeve; and the Chinese patent (Application No. 201921238429.9) adopts a diversion groove method. The above-mentioned patent schemes have cumbersome structures, complicated operations and low reliability.

On the other hand, at present, a pressure wave decoding method for pressure pulse communication regardless in drilling engineering or oil production engineering refers to a judgment method for performing sampling judgment of fixed thresholds or calculating an average value. The method has the advantages of simple algorithm and less amount of calculation, but has the disadvantage of being easily affected by noise. To reduce a bit error rate, it is necessary to increase the redundancy of a pressure value, which leads to an excessively long element transmission time. Therefore, how to reduce the cumbersomeness and complexity of a system for wellbore pressure test and sliding sleeve joint operation, and at the same time reduce a bit error rate of pressure pulse communication, is an urgent technical problem to be solved.

The foregoing content is only used to assist in understanding the technical solution of the present invention, and does not mean that the foregoing content is recognized as the prior art.

SUMMARY OF THE INVENTION

A main object of the present invention is to provide an intelligent pressure transmitter calibration system, which aims to solve the technical problems of complicated system of wellbore pressure test and sliding sleeve joint operation, high operation complexity, high bit error rate of pressure pulse communication, and long element transmission time in the existing solutions in the prior art.

To achieve the above object, the present invention provides a method for controlling a toe-end sliding sleeve of a horizontal well based on efficient decoding communication, comprising the following steps:

adjusting and controlling a pressure value in a wellbore according to a first preset encoding manner to form a pressure wave signal;

collecting a pressure value change signal in the wellbore, determining a reference time by using an STA/LTA method, and performing pressure value prediction to acquire a predicted pressure value signal curve;

identifying a toe-end sliding sleeve control command in the acquired pressure wave signal by using a first preset decoding manner based on the fitness between the collected pressure value signal curve and the acquired predicted pressure value signal curve; and

driving the toe-end sliding sleeve to perform actions according to the toe-end sliding sleeve control command.

Preferably, the step of adjusting and controlling the pressure value in the wellbore according to the preset encoding manner to form the pressure wave signal comprises:

controlling a valve of ground pressurizing equipment to be opened or closed based on the first preset encoding manner; and

converting toe-end sliding sleeve control command information into a pressure wave signal in a form of liquid pressure fluctuations by using liquid in the wellbore as a pressure transmission medium.

Preferably, the step of controlling the valve of the ground pressurizing equipment to be opened or closed based on the first preset encoding manner comprises:

building a communication control link between a control terminal and the ground pressurizing equipment;

editing/importing the toe-end sliding sleeve control command from the control terminal, and converting the toe-end sliding sleeve control command into a valve group control signal of the ground pressurizing equipment by using the first preset encoding manner; and

receiving, by the ground pressurizing equipment, the valve group control signal of the control terminal to drive valve control equipment, and controlling the ground pressurizing equipment to pressurize the wellbore.

Preferably, prior to receiving, by the ground pressurizing equipment, the valve group control signal of the control terminal to drive the valve control equipment, and controlling the ground pressurizing equipment to pressurize the wellbore, further comprising the follow steps that can be implemented independently or in combination:

sending, by the control terminal, a first control signal for driving the valve control equipment to the ground pressurizing equipment to control the valve of the ground pressurizing equipment to be opened;

sending, by the control terminal, a second control signal for driving the valve control equipment to the ground pressurizing equipment to control the valve of the ground pressurizing equipment to be closed;

sending, by the control terminal, a third control signal for driving the valve control equipment to the ground pressurizing equipment to control the opening of the valve of the ground pressurizing equipment to be increased;

sending, by the control terminal, a fourth control signal for driving the valve control equipment to the ground pressurizing equipment to control the opening of the valve of the ground pressurizing equipment to be reduced.

Preferably, the step of collecting the pressure value change signal in the wellbore, determining the reference time by using the STA/LTA method, and performing pressure value prediction to acquire the predicted pressure value signal curve comprises:

monitoring a pressure value change state by the STA/LTA method; and

setting a time at which a trigger threshold is monitored as the reference time, and acquiring a predicted pressure value according to a formula that a pressure value exponentially changes with the actions of the valve.

Preferably, a formula expression for monitoring the pressure value change state by the STA/LTA method is:

S⁢T⁢AL⁢T⁢A=≥γ;

in which, STA=Σi=1ns|P(i)|; LTA=Σi=1nl|P(i)|; P(i) is a pressure value, MPa; nsis a short time window length, 1; nlis a long time window length, 1 and; γ is a threshold, 1.

Preferably, the step of setting the time at which the trigger threshold is monitored as the reference time, and acquiring the predicted pressure value according to the formula that the pressure value exponentially changes with the actions of the valve comprises:

waking up a downhole toe-end sliding sleeve by continuously pumping a high pressure;

delimiting a waiting time range, a code element length range and a sending time range at the end of pumping the high pressure, and acquiring a stabilized high pressure value and a stabilized low pressure value through regular sampling; and

sampling data during the waiting period, acquiring a time constant of pressure drop based on a fitting formula, agreeing a first code element to be 1, and acquiring a time constant of pressure rise based on the fitting formula according to the code element length, the stabilized high pressure value and the stabilized low pressure value; and calculating whether the pressure rises or drops through the acquired time constant and the current pressure value.

Preferably, the step of acquiring the predicted pressure value according to the formula that the pressure value exponentially changes with the actions of the valve comprises:
pc=pf+(pi−pf)e−t/τ0;

in which, pcis a predicted pressure value; pfis a stabilized pressure value; piis an initial pressure value; t is a change time; and τ0is a system coefficient obtained by fitting with a computer.

Preferably, the step of adjusting and controlling the pressure value in the wellbore according to the preset encoding manner to form the pressure wave signal comprises:

performing encoding by adopting a relative encoding technology, i.e., adopting a method of closing the value or reducing the opening of the value when a code 0 is sent, and adopting a method of opening the value or increasing the opening of the value when a code 1 is sent, or adopting an opposite way, to further generate a pressure wave signal containing the toe-end sliding sleeve control command.

Preferably, the step of acquiring the toe-end sliding sleeve control command in the pressure wave signal by using the first preset decoding manner comprises:

determining code elements sent in the pressure wave signal based on the fitness between recorded pressure value signal data and predicted pressure value signal data;

identifying information in the pressure wave signal according to a parity discrimination method; acquiring a decoded value as “1” by decoding if the calculated pressure change state is a rising state; and acquiring a decoded value as “0” by decoding if the calculated pressure change state is a drop state; and

identifying the toe-end sliding sleeve control command in the acquired pressure wave signal by using the first preset decoding manner based on the acquired decoded values.

The present invention has the beneficial effects: 1, in the process of pressure relief after a wellbore pressure test ends, a ground valve is controlled to convert information into a form of liquid pressure fluctuations and transfer the converted information to a downhole sliding sleeve by taking fracturing fluid or other liquid as a medium according to a preset encoding method, thereby avoiding using cables, pipelines, or a pitching manner for information transmission, and reducing the complexity of the preliminary work of fracturing operations; 2, the sliding sleeve disclosed by the present invention comprises a pressure detection unit, a decoding unit and an execution unit, wherein the pressure detection unit is configured to detect pressure fluctuations in a wellbore, and the decoding unit is configured to decode address information and action information contained in a pressure wave signal, match an address in the pressure wave with a local address and send an instruction of the operation information in the pressure wave to the action execution unit after the match is successful, such that the operation information contained in the pressure wave is analyzed and reflected in the sliding sleeve; 3, the action execution unit in the sliding sleeve of the present invention includes a built-in hydraulic or mechanical motion system (including but not limited to: being pushed by a hydraulic pressure or a screw rod) and an independent power supply, such that the movement of the sliding sleeve is easier to operate, and it is also convenient for construction personnel to independently control a plurality of sliding sleeves; 4, the change in opening of a control valve is automatically controlled according to the preset encoding method to generate a pressure wave sequence, and the address information and the operation information including in the information carried by the pressure wave are then transmitted to the downhole sliding sleeve, so that the construction personnel can accurately control the movement and status of each sliding sleeve remotely; and 5, the present invention proposes an efficient decoding method in a noisy environment, which is different from traditional fixed threshold sampling judgment or average value judgment, and can reduce the influence of noise on pressure communication of the downhole sliding sleeve in either drilling engineering or oil production engineering. The method aims to solve the technical problems of complicated system of wellbore pressure test and sliding sleeve joint operation, high operation complexity, high error rate of pressure pulse communication, and long element transmission time in the existing solutions in the prior art.

