CN102900430A - Pumping pressure interference elimination method for drilling fluid continuous pressure wave signals - Google Patents

Abstract

The invention provides a pump pressure interference elimination method for drilling fluid continuous pressure wave signal. Two pressure sensors are installed on a straight pipeline with a certain distance apart. One end of the straight pipeline is connected with the drilling fluid pump, and the other end is connected with the wellhead, reflecting The downhole drilling fluid pressure signal of downhole measurement information while drilling is transmitted from the wellhead to the ground through a straight pipeline and received by a pressure sensor installed on the straight pipeline. The measured signals of the two pressure sensors are subtracted to obtain a delayed differential detection signal. The transmission direction of the pressure interference is opposite to that of the downhole drilling fluid pressure signal, so the pressure interference generated by the drilling fluid pump is eliminated in this process, and there is no pump pressure interference component in the delayed differential detection signal, while the delayed differential detection signal The downhole drilling fluid pressure signal included in the model can be restored by the signal reconstruction method based on time domain difference equation or Fourier transform, so as to eliminate the influence of pump pressure interference in the signal and improve the signal-to-noise ratio.

Description

Pump pressure interference elimination method for continuous pressure wave signal of drilling fluid

Technical field:

The invention relates to a processing method of measurement-while-drilling/logging-while-drilling uploaded signals during oil and gas drilling, and in particular to a method for eliminating pump pressure interference of drilling fluid continuous pressure wave signals for downhole data transmission based on drilling fluid.

Background technique:

Downhole measurement while drilling/logging while drilling (MWD/LWD) is a modern drilling auxiliary technology that measures and transmits downhole information in real time during drilling. During the drilling process, the drilling fluid is pumped downhole from the surface through the drill string, sprayed out from the water hole of the drill bit for the lubrication and cooling of the drill bit, and returns upward to the wellhead through the annular space between the well wall and the drill string. MWD/LWD tools are installed In the drill collar on the drill bit top, see accompanying drawing 1. In MWD/LWD tools, sensors installed in the drill string near the drill bit obtain measurement data and transmit it to the surface through the drilling fluid pressure information telemetry system. Transmission of downhole measurement while drilling/logging while drilling data. Pressure information telemetry usually uses baseband pressure pulses or continuous pressure waves to transmit downhole information. Continuous pressure waves have a much higher downhole information transmission rate than baseband pressure pulses, which is the development direction of pressure information telemetry technology; continuous pressure wave signals mainly include Drilling fluid pressure differential phase shift keying (DPSK) signal and quadrature phase shift keying (QPSK) signal, the signal spectrum is concentrated and has the characteristics of frequency band transmission. During the transmission of drilling fluid pressure signals from the bottom of the well to the surface and the process of surface signal detection, there will be a lot of noise and interference. Among them, the pressure pulsation interference generated by the drilling fluid pump has the greatest impact on the signal. The pressure interference generated by the drilling fluid pump is related to the pump stroke rate, including fundamental waves and higher harmonics. When the pistons of the drilling fluid pumps have sealing problems that cause unbalanced work or the pump is in an abnormal working state, some high-order harmonics The amplitude of harmonics will become very large. Although the drilling fluid pump pipeline is equipped with pressure buffers or dampers, the pressure pulsation generated by the drilling fluid pump can still reach or exceed the downhole drilling fluid pressure detected by the ground riser Signal strength, these high-order harmonics will enter the frequency band of the drilling fluid continuous pressure wave signal and cause great interference, which will seriously reduce the signal-to-noise ratio of the signal, thus affecting the extraction of downhole measurement signals while drilling. The current drilling fluid pressure signal detection mainly uses a pressure sensor installed at the ground riser to measure the drilling fluid pressure, and the signal processing methods used, such as matched filter method, adaptive compensation method, wavelet analysis method, etc. The pressure signal transmitted in the baseband mode; and for the drilling fluid continuous pressure wave signal with a relatively high transmission rate, because the signal has the characteristics of frequency band transmission, the pressure interference generated by the drilling fluid pump can easily enter the signal frequency band, and the above-mentioned downhole drilling fluid pressure signal None of the existing detection and processing methods can effectively eliminate the influence of drilling fluid pump pressure interference that has entered the signal frequency band.

Invention content:

The technical problem to be solved by the present invention is to provide a method for eliminating pump pressure interference in the continuous pressure wave signal of drilling fluid in view of the defects existing in the existing signal processing technology.

The technical problem to be solved by the present invention is realized according to the following technical solutions:

1. Use delay differential detection method to eliminate the influence of pump pressure interference of drilling fluid pump

Install pressure sensor A and pressure sensor B on a section of straight drilling fluid pipeline between the wellhead and the drilling fluid pump, where pressure sensor A is close to the wellhead and pressure sensor B is close to the drilling fluid pump, and the downhole measurement data is converted by modulating the drilling fluid pressure It is the drilling fluid pressure signal, which is transmitted from the bottom of the well through the drill string to the wellhead in a fluctuating manner, and then reaches the pressure sensor A first, and then reaches the pressure sensor B. The pressure signals received by the two sensors include the downhole drilling fluid pressure signal and the drilling fluid pump. According to the signal flow analysis, the transmission direction of the pump pressure interference is opposite to the downhole drilling fluid pressure signal, so the downhole drilling fluid pressure signal received by pressure sensor A will delay reaching pressure sensor B. The transmission time of the hydraulic pressure wave through the distance between the two pressure sensors, and the pump pressure interference received by the pressure sensor B will reach the pressure sensor A after a delay of this period; therefore, the pressure received by the two pressure sensors A and B The signal can be expressed as the following mathematical model

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In formula (1), p _A (t) is the signal received by pressure sensor A; p _B (t) is the signal received by pressure sensor B; s (t) is the downhole drilling fluid pressure signal; n _p (t) is the pump pressure disturbance generated by the drilling fluid pump; h(t) is the unit shock response of the pipeline with pressure sensor A and pressure sensor B installed; the symbol "*" represents the convolution operation.

Convolving p _B (t) in formula (1) with h(t), we have

p _B (t)*h(t)=[h(t)*s(t)]+n _p (t)*h(t) (2)

Subtract p _A (t) in formula (1) from formula (2) to obtain the mathematical model of delayed differential detection signal

Δp(t)=p _A (t)-p _B (t)*h(t)=s(t)-h(t)*h(t)*s(t) (3)

It can be seen from formula (3) that the pump interference term n _p (t) is eliminated through the convolution of p _B (t) and h (t) and the differential operation with p _A (t), and the delay differential detection The signal Δp(t) has no pump pressure interference component.

The propagation path due to the pump disturbance is from pressure sensor B to pressure sensor A. Equation (2) means that the detection signal p _B (t) of pressure sensor B passes through a linear system with a unit shock response of h(t), since h(t) contains the signal through the installation of pressure sensor A and pressure sensor B The delay τ ₀ generated by the section pipeline, its physical meaning is that after delaying the pump pressure interference item in p _B (t) for another τ ₀ time, it will have the same time delay as the pump pressure interference item in p _A (t) , since the signal p _A (t) and the signal p _B (t)*h(t) appear at the same time as the pump pressure disturbance, by subtracting the signal p _A (t) from the signal p _B (t)*h(t) The purpose of eliminating pump pressure interference can be achieved. However, since formula (2) is only a mathematical expression, it is impossible to make p _B (t) pass through a physical system with unit impulse response h(t) in the implementation process, so the acquisition of the delayed differential detection signal must be able to physical realization. According to the same idea of formula (3), if the signal of pressure sensor A is detected after a delay of τ ₀ , the pump pressure interference in the detection signal p′ _A (t) of pressure sensor A is caused by the installation of pressure sensor A and The pump pressure interference transmitted by the pressure sensor B section pipeline through the pressure sensor B can also eliminate the influence of the pump pressure interference by subtracting the signal p′ _A (t) from the signal p _B (t), thus physically realizing the equation (3 ) describes the delayed differential detection signal Δp(t). Therefore, the acquisition of the delayed differential detection signal is realized by delaying τ ₀ time to detect the signal p′ _A (t) of pressure sensor A and subtracting it from the detection signal p _B (t) of pressure sensor B, that is

Δp(t)=p′ _A (t)-p _B (t) (4)

The downhole drilling fluid pressure signal s(t) contained in the delayed differential detection signal Δp(t) can be recovered through mathematical reconstruction.

2. Mathematical reconstruction of downhole drilling fluid pressure signal

The process of recovering the downhole drilling fluid pressure signal from the delayed differential detection signal is called reconstruction. To realize the reconstruction of the downhole signal, the construction of h(t) is a key issue. The present invention is realized in this way: affected by the transmission distance and Due to the limitation of signal transmission rate, the highest frequency of the continuous pressure wave signal spectrum of drilling fluid is usually tens of hertz, so the frequency of the signal is limited; within the limited frequency band, if the pipeline between pressure sensor A and pressure sensor B is installed As a distortion-free transmission system, it constitutes an ideal low-pass filter, and the frequency domain transfer function of the system is

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; aG</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

为单位门函数，ω_b为单位门函数的单边带宽度；

代表复数的虚部算子；ω=2πf为信号角频率，f为信号频率；τ₀=L₀/c₀为压力波在压力传感器A和B之间的传输时间，L₀为压力传感器A和B之间的距离，c₀为压力波传播速度。则安装压力传感器A和压力传感器B段管道的单位冲击响应为In formula (5), a is the signal attenuation coefficient generated by the signal passing through the pipelines of pressure sensor A and pressure sensor B;

is the unit gate function, ω _b is the SSB width of the unit gate function;

Represents the imaginary part operator of a complex number; ω=2πf is the angular frequency of the signal, f is the signal frequency; τ ₀ =L ₀ /c ₀ is the transmission time of the pressure wave between pressure sensors A and B, and L ₀ is the pressure sensor A and the distance between B, c ₀ is the pressure wave propagation speed. Then the unit shock response of the pipeline with pressure sensor A and pressure sensor B installed is

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; a\&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\mathrm{<span\; class="notranslate">\; Sa</span>}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Take the Fourier transform of formula (3) to get

$\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j"\; filenames="HDA00002144428900041.png,HDA00002144428900042.png"\; state="\{\{state\}\}">j</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&omega;</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

The spectral density function of the downhole drilling fluid pressure signal is

$\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j"\; filenames="HDA00002144428900041.png,HDA00002144428900042.png"\; state="\{\{state\}\}">j</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&omega;</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Wherein, ΔP(jω)=F[Δp(t)]=F[ _p'A (t) _-pB (t)] is the Fourier transform of the delayed differential detection signal Δp(t); is the frequency domain transfer function of the downhole drilling fluid pressure signal recovery system, and the reconstruction of the downhole drilling fluid pressure signal can be realized by H(jω).

The reconstruction method of drilling fluid pressure signal can adopt signal reconstruction based on time domain difference equation and signal based on Fourier transform.

According to the digital filter theory, H(jω) is a k (k=2τ ₀ /T _s , T _s is the signal sampling period) order infinite impulse response filter system. Therefore, under the condition that H(jω) constitutes an ideal low-pass transmission, the signal reconstruction process based on the time-domain difference equation is to make the delayed differential detection signal Δp(t) pass through a closed-loop delay feedback system with a recursive structure to recursively calculate The downhole drilling fluid pressure signal contained in the delayed differential detection signal is obtained by using the method, and the expression is

$\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; a\&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; Sa</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; Sa</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

The signal reconstruction based on Fourier transform is to obtain the downhole drilling fluid pressure signal by performing inverse Fourier transform on equation (8), the expression is

$\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&infin;</span>}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; a</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="j"\; filenames="HDA00002144428900041.png,HDA00002144428900042.png"\; state="\{\{state\}\}">j</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&omega;</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j\&omega;t</span>}}\mathrm{<span\; class="notranslate">\; d\&omega;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

3. Determination of reasonable distance between pressure sensors

When the two pressure sensors are close to each other, the transmission loss of the drilling fluid pressure wave passing through the two pressure sensors is very small, and the signal attenuation coefficient is very close to 1 (that is, a=1). Therefore, there is a pole in the transfer function H(jω) of the downhole drilling fluid pressure signal recovery system, and the frequency of the pole is

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="f"\; filenames="HDA00002144428900041.png,HDA00002144428900042.png"\; state="\{\{state\}\}">f</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

When the pole frequency enters the signal frequency band, it will cause great interference to the reconstruction of the signal and cannot be removed. In order to avoid this situation, all pole frequency values should be greater than the passband frequency of the ideal low-pass filter, that is, f ₀ >f _b , thus the constraint condition for determining the distance between the two pressure sensors is

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="L"\; filenames="HDA00002144428900041.png,HDA00002144428900042.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; <</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="c"\; filenames="HDA00002144428900041.png,HDA00002144428900042.png"\; state="\{\{state\}\}">c</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

The distance between two pressure sensors can be determined on the basis of conforming to the constraints of formula (12).

The beneficial effects of the present invention are: two pressure sensors are used for delayed differential detection to eliminate the influence of drilling fluid pump pressure interference, and the downhole drilling fluid pressure signal is recovered from the delayed differential detection signal through mathematical reconstruction to improve the signal signal. Noise ratio, to ensure the correct extraction of downhole measurement while drilling information transmitted by drilling fluid.

Description of drawings:

Fig. 1 is a schematic diagram of a drilling device including measurement-while-drilling/logging-while-drilling tools and drilling fluid pressure signal detection and processing in the prior art.

Fig. 2 is a flow chart of the detection and processing of drilling fluid continuous pressure wave signals in the present invention.

Fig. 3a is a block diagram of computer data acquisition and processing software for signal reconstruction based on time-domain difference equations according to the present invention.

Fig. 3b is a block diagram of computer data acquisition and processing software for signal reconstruction based on Fourier transform according to the present invention.

Fig. 4a is a waveform simulation diagram of the original DPSK signal of drilling fluid pressure with 10 binary symbols in the present invention.

Fig. 4b is a waveform simulation diagram of the original drilling fluid pressure DPSK signal mixed with pump pressure interference in the present invention.

Fig. 4c is a waveform simulation diagram of the delayed differential detection signal in the present invention.

Fig. 4d is a waveform simulation diagram of drilling fluid pressure DPSK signal reconstruction in the present invention.

In the figure: 1-drilling fluid, 2-surface, 3-drill string, 4-drilling fluid pump, 5-drill bit, 6-annular space, 7-formation, 8-drilling parameters and formation parameter measuring device, 9-drilling fluid Continuous pressure wave signal generator, 10-pressure sensor, 11-signal processing device, 12-drill collar, 13-drilling fluid tank, 14-pressure sensor A, 15-pressure sensor B, 16-data acquisition and signal processing system, 17-drilling fluid pressure signal, 18-wellhead, 19-drilling fluid pump pressure interference signal, 20-straight pipeline.

Detailed ways:

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 shows an existing drilling device including measurement-while-drilling/logging-while-drilling tools and drilling fluid pressure signal detection and processing. The drilling fluid 1 in the drilling fluid tank 13 is injected into the drill string 3 drilled into the formation 7 through the drilling fluid pump 4 on the surface 2, reaches the drill bit 5 at the bottom of the drill string 3, and passes through the drill string 3 and the formation 7 after flowing out from the water hole of the drill bit. The annular space 6 between returns to the surface 2, and the arrows indicate the flow path of the drilling fluid.

Instruments are placed in the drill collar 12 close to the drill bit 5 in the drill string 3 , and the upper part of the drill collar is connected to the drill pipe to form a drill string. The entire drill string applies sufficient WOB to the drill bit 5 for drilling into the formation 7 . Instrumentation in the drill collar 12 includes drilling parameter and formation parameter measurement devices 8 for monitoring drilling operations and assessing the physical properties of the formation.

In order to generate pressure fluctuations in the drilling fluid and transmit downhole data through the drilling fluid, the drilling fluid continuous pressure wave signal generator 9 is installed on the upper part of the drill collar 12, and the drilling fluid pressure signal is uploaded to the ground through the drill string and detected by the pressure sensor 10 And sent to the signal processing device 11 for signal processing.

The method for eliminating the pump pressure interference of the drilling fluid continuous pressure wave signal is realized according to the following technical scheme:

1. Elimination of Drilling Fluid Pump Pressure Disturbance by Using Delayed Differential Detection Method

Install pressure sensor A and pressure sensor B in a straight drilling fluid pipeline between the wellhead and the drilling fluid pump, where pressure sensor A is close to the wellhead and pressure sensor B is close to the drilling fluid pump, and the downhole measurement signal is transmitted from the bottom of the well to the drilling fluid pump. After the wellhead, it first encounters pressure sensor A, and the pressure signals received by the two pressure sensors include the downhole drilling fluid pressure signal and the pump pressure interference generated by the drilling fluid pump. According to the signal flow analysis, the transmission direction of the pump pressure disturbance is opposite to the transmission direction of the downhole drilling fluid pressure signal, so the downhole drilling fluid pressure signal received by pressure sensor A will reach pressure sensor B after a period of delay, and this period is The transmission time for the drilling fluid pressure wave to pass through the distance between the two pressure sensors, and the pump pressure disturbance received by pressure sensor B will reach pressure sensor A after a delay of this period. At a certain moment, the pressure sensor B has a certain pressure measurement value, and the output signal of the pressure sensor A is delayed for a period of time to obtain the measurement value, and the measurement value of the pressure sensor A is subtracted from the measurement value of the pressure sensor B to obtain the delay difference The pump pressure interference is eliminated in this process, and there is no pump pressure interference component in the delayed differential detection signal, and the downhole drilling fluid pressure signal contained in the delayed differential detection signal can be obtained through special mathematical reconstruction. recovery, so this method is called the delay differential detection method, the time-domain mathematical model of the pressure sensor A and pressure sensor B signals represented by formula (1) and the mathematical model of the delayed differential detection signal represented by formula (3) can be Describe clearly.

2. Mathematical Reconstruction of Downhole Drilling Fluid Pressure Signal

The process of recovering the downhole drilling fluid pressure signal from the delayed differential detection signal is called reconstruction, and the reconstruction adopts the signal reconstruction method based on time-domain difference equation and the signal reconstruction method based on Fourier transform. The signal reconstruction process based on the time-domain difference equation is to make the delayed differential detection signal pass through a closed-loop delay feedback system with a recursive structure, and obtain the downhole drilling fluid pressure signal contained in the delayed differential detection signal with a recursive algorithm. Signal reconstruction based on Fourier transform The downhole drilling fluid pressure signal is obtained through the inverse Fourier transform represented by equation (10).

3. Determination of Reasonable Space Between Pressure Sensors

When the two pressure sensors are close to each other, the transmission loss of the drilling fluid pressure wave passing through the two pressure sensors is very small, and the modulus of the transfer function is close to 1, so there is a pole in the transfer function of the downhole drilling fluid pressure signal recovery system. The frequency corresponding to the pole enters the signal frequency band, which will cause great interference to the reconstruction of the signal and cannot be removed. In order to avoid this situation, all pole frequency values should be greater than the passband frequency of the ideal low-pass filter, thus the sensor spacing constraints expressed by equation (12) can be obtained: the pressure sensor spacing should be less than the pressure wave velocity divided by 2 times The ideal low-pass filter passband frequency. The distance between the two pressure sensors can be determined on the basis of meeting the above constraints.

Fig. 2 shows the detection and processing flow chart of drilling fluid continuous pressure wave signal. The present invention adopts two pressure sensors separated by a certain distance to measure the drilling fluid pressure in a specific straight pipeline respectively, wherein pressure sensor A needs more pressure than pressure sensor B. Delay for a period of time before measuring the drilling fluid pressure. This period of time is the transmission time for the drilling fluid pressure wave to pass through the distance between the two pressure sensors. The signals of the two pressure sensors are collected and processed by the computer to realize the drilling fluid pump pressure. Elimination of interference and reconstruction of downhole drilling fluid pressure signals. The technical solution is: the straight pipeline 20 is connected between the wellhead 18 and the drilling fluid pump 4, the drilling fluid 1 is injected downhole through the pipeline from the wellhead 18, the pressure sensor A14 is close to the wellhead 18, and the pressure sensor B15 is close to the drilling fluid pump 4 , the drilling fluid pressure signal 17 uploaded downhole propagates from the wellhead 18 to the direction of the drilling fluid pump 4, passing through the pressure sensor A14 and the pressure sensor B15 in turn, and the pump pressure interference signal 19 propagates from the drilling fluid pump 4 to the direction of the wellhead 18, passing through the pressure sensor in turn B15 and pressure sensor A14, the electrical signals of pressure sensor A14 and pressure sensor B15 can be connected with computer data acquisition and signal processing system 16 through wired or wireless means, and the computer processes the signals of pressure sensor A14 and pressure sensor B15 to realize the drilling fluid pump Elimination of pressure interference and reconstruction of downhole drilling fluid pressure signals. The core of the computer signal processing program is the delay differential detection algorithm of the signal and the mathematical reconstruction algorithm of the downhole drilling fluid pressure signal. The hydraulic pressure wave passes through the transmission time of the distance between the two pressure sensors, so that the pressure sensor A is delayed by this period of time relative to the pressure sensor B to measure the drilling fluid pressure, and then the measured value of the pressure sensor A is compared with the measured value of the pressure sensor B The delay differential detection signal is obtained by subtraction, and the mathematical reconstruction algorithm of the downhole drilling fluid pressure signal adopts the signal reconstruction method based on the time domain difference equation of formula (9) or the signal reconstruction method of formula (10) based on Fourier transform.

In Fig. 3a, the delayed differential detection of the pressure signal and the reconstruction of the downhole drilling fluid pressure signal are realized in the time domain through the computer data acquisition and processing system, and the signal reconstruction adopts a recursive algorithm based on the time domain difference equation.

In Fig. 3b, in the computer data acquisition and processing system, the delay differential detection value of the pressure signal is first obtained in the time domain, and then transformed into a frequency domain value by Fourier transform, and then combined with the downhole drilling fluid pressure signal recovery system The frequency domain transfer function is multiplied to obtain the spectral density function of the drilling fluid pressure signal, and the inverse Fourier transform is taken for the spectral density function of the drilling fluid pressure signal to realize the reconstruction of the downhole drilling fluid pressure signal.

In Fig. 4a, the modulation data code of the drilling fluid pressure DPSK original signal is [1 1 1 1 1 1 1 1 1 1], the carrier frequency is 20Hz, and the amplitude is 1Pa.

In Fig. 4b, the fundamental frequency of the pump pressure disturbance is 3.2 Hz, the harmonic order is 2-9, and the amplitude of the fundamental wave and each harmonic is 1 Pa. After the original drilling fluid pressure DPSK signal is mixed into the pump pressure disturbance, the amplitude of the pump pressure disturbance is Much larger than the original signal amplitude of drilling fluid pressure DPSK, the signal-to-noise ratio is 0.11, and the signal has been completely submerged by pump pressure interference.

In Fig. 4c, it can be seen from the delayed differential detection signal that the pump pressure disturbance is completely eliminated.

In Fig. 4d, the DPSK reconstruction signal of drilling fluid pressure is consistent with the original signal in Fig. 4a, and the signal is well restored.

Claims (1)

1. A pump pressure interference elimination method of drilling fluid continuous pressure wave signal is characterized in that it is carried out in the following steps: (1) The delayed differential detection method is used to eliminate the influence of the pump pressure interference of the drilling fluid pump Install pressure sensor A and pressure sensor B on a section of straight drilling fluid pipeline between the wellhead and the drilling fluid pump, where pressure sensor A is close to the wellhead and pressure sensor B is close to the drilling fluid pump, and the downhole measurement data is converted by modulating the drilling fluid pressure It is the drilling fluid pressure signal, which is transmitted from the bottom of the well through the drill string to the wellhead in a fluctuating manner, and then reaches the pressure sensor A first, and then reaches the pressure sensor B. The pressure signals received by the two sensors include the downhole drilling fluid pressure signal and the drilling fluid pump. The generated pump pressure interference; according to the signal flow analysis, the transmission direction of the pump pressure interference is opposite to the downhole drilling fluid pressure signal, so the downhole drilling fluid pressure signal received by pressure sensor A will delay reaching pressure sensor B, and the delayed time is The transmission time of the hydraulic pressure wave through the distance between the two pressure sensors, and the pump pressure interference received by the pressure sensor B will reach the pressure sensor A after a delay of this period; at a certain moment, the pressure sensor B measures the pipeline pressure value , the pressure sensor A measures the pipeline pressure value after a delay of this period of time, and the measured value of the pressure sensor A is subtracted from the measured value of the pressure sensor B to obtain a delayed differential detection signal; the pump pressure interference is eliminated in this process, and the delay difference There is no pump pressure interference component in the dynamic detection signal, and the downhole drilling fluid pressure signal contained in the delayed differential detection signal can be recovered through mathematical reconstruction; (2) Mathematical reconstruction of downhole drilling fluid pressure signal The signal reconstruction method based on the time-domain difference equation and the signal reconstruction method based on Fourier transform are adopted. The signal reconstruction process based on the time-domain difference equation is to make the delayed differential detection signal pass through a closed-loop delay feedback system with a recursive structure. Obtain the downhole drilling fluid pressure signal contained in the delayed differential detection signal with a recursive algorithm, and reconstruct the signal based on Fourier transform by constructing a limited-bandwidth ideal low-pass filter mathematically installed in the pipeline between pressure sensor A and pressure sensor B The model is to establish the frequency domain transfer function of the downhole drilling fluid pressure signal recovery system, and obtain the downhole drilling fluid pressure signal by the Fourier inverse transform of the output function when the delayed differential detection signal passes through the downhole drilling fluid pressure signal recovery system; (3) Determination of pressure sensor spacing The distance between the two pressure sensors should be less than the pressure wave velocity divided by 2 times. The limited bandwidth of the pipe between the two pressure sensors is installed. The ideal low-pass filter passband frequency.

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