RU2297532C1 - Method for determining level of liquid in annular space of oil product wells - Google Patents

Abstract

FIELD: well research, possible use for determining and controlling static and dynamic oil level in product wells.

SUBSTANCE: in accordance to method, signal s₀(t) is generated in form of a sum of rectangular impulses, changing time of n-th impulse and its duration depending on n. Generated signal s₀(t) is sent to generator of acoustic signal for generation thereof. Acoustic signal s₁(t) reflected from liquid is transformed to electric signal and subjected to analog-digital transformation. Signal s₀(t) is subjected to folding operation with digitized reflected signal s₁(t), and then temporary position of signal reflected from liquid is determined relatively to moment of generation of acoustic signal in inter-tubular space, using which, level of liquid is determined.

EFFECT: possible control over level of liquid in wells with high value of signal/noise ratio, resulting in decreased probability of error during computation of level.

5 dwg, 3 tbl

Description

The invention relates to the control of the liquid level in oil producing wells by echo metering and can be used to determine the static and dynamic oil levels in producing wells.

A known method of determining the level of fluid in the well [RF Patent No. 2095564, IPC 6 ЕВВ 47/04, G01F 23/00, publ. November 10, 1997], selected as a prototype, including: generating an acoustic pulse at the wellhead, converting the reflected acoustic signals into electric ones, amplifying them, filtering them, determining the square root of the signal amplitude, followed by recording on a self-cleaning device, determining the liquid level by the product of time the passage of sound from the wellhead to the fluid level, measured according to the graph of the acoustic signal, to the speed of sound taken from the tabular data depending on the pressure and properties of the gas in the annulus space, and dividing this product by two.

The method does not provide a high value of the signal-to-noise ratio, which leads to errors in determining the liquid level in the wells, since a single acoustic pulse is used as a probing signal, with insufficient energy provided that the resolution is acceptable.

The task of the invention is to increase the signal-to-noise ratio of the signal reflected from the liquid.

To solve this problem, the method of determining the liquid level in the annulus of oil producing wells, as well as in the prototype, includes generating an acoustic signal s ₀ (t) at the wellhead in the annulus, converting the acoustic signal reflected from the liquid into an electric signal s ₁ (t) , determining the propagation time of sound from the wellhead to the fluid level, determining the fluid level by the product of the propagation time of sound from the wellhead to the fluid level by the known sound velocity in oil gas well and dividing this product into two.

According to the invention, an acoustic signal is generated.

where a is the amplitude of the pulses in the series,

t is the time

N is the number of pulses in the series,

T is the pulse duration,

u (t, Т) is a rectangular impulse defined by the expression:

moreover, the difference tt _n sets the beginning of the nth pulse in the series, and with T _{n the} duration of the nth pulse in the series, changing t _n and T _n according to the expressions:

where T ₀ - the duration of the first pulse in the series,

μ is a parameter that determines changes in the duration and position of pulses in a series,

and applying a signal s ₀ (t) to the shaper of the acoustic signal to generate it. After converting the acoustic signal reflected from the liquid into an electric signal, it is subjected to analog-to-digital conversion. The signal s ₀ (t) is subjected to a convolution operation with the digitized reflected signal s ₁ (t). Then determine the temporary position of the signal reflected from the liquid relative to the moment of formation of the acoustic signal in the annulus, using which determine the liquid level in the annulus.

The determination of the liquid level in oil wells is achieved by forming an acoustic signal at the wellhead in the form of a series of pulses, the duration and period of which are changed according to expressions (1) and (2). The use of such a signal can significantly increase the signal-to-noise ratio of the signal reflected from the liquid. This is due to the fact that the energy of such a signal is distributed over a relatively extended time period. Through the convolution operation, this energy can be concentrated on a shorter time interval, due to which the signal power increases significantly.

So, the method adopted as a prototype is characterized by a potentially achievable signal-to-noise ratio, which is determined by the expression [Cook C., Bernfeld M. Radar signals. - M .: Soviet Radio, 1971. - P.18]:

where Δp is the pressure drop in the annulus during the formation

acoustic signal

Q ₀ - spectral power density of acoustic noise in the annulus

space

Δf is the effective passband of the acoustic transducer and the analog-to-digital transducer.

The acoustic noise in the annulus of the well is assumed to be white Gaussian noise. The effective passband of the acoustic transducer and the analog-to-digital transducer coincides with the effective frequency band of the reflected signal. In addition, the reflected signal used in the prototype is a simple signal (that is, a signal without intra-pulse modulation), and the effective band of such a signal is inversely proportional to its duration T [S. Baskakov Radio engineering circuits and signals, 1983. - S. 56]. Given the above provisions, formula (3) takes the form:

In the inventive method, the duration of the generated acoustic signal is determined by the expression:

Suppose that the duration of the generated signal of the prototype is equal to T ₀ . The ratio of expressions (4) for the proposed method and for the prototype describes an increase in the signal-to-noise ratio for the proposed method:

In the trivial case, when N = 1, the ratio (5) is equal to unity, and the signal-to-noise ratio does not increase. However, as N increases, the signal-to-noise ratio increases according to the quadratic law. The graphs in Fig. 1 represent a function (5), which depends on the number of pulses in the N series and on the parameter μ. The value of this function is a value that shows how many times the signal-to-noise ratio of the proposed method is greater than the signal-to-noise ratio of the prototype.

Figure 1 shows graphs of increasing signal to noise ratio.

Figure 2 presents a diagram of a device for determining the level of liquid in the annulus of oil production wells.

Figure 3 shows plot 1 - a series of rectangular pulses.

Figure 4 shows plot 2 - the signal received by the acoustic transducer in the well.

Figure 5 presents plot 3 - the result of the convolution of the received signal and a series of rectangular pulses.

Table 1 presents the samples of signals s ₀ (t) coming from the output of the control module.

Table 2 shows the samples of signals s ₁ (t) received by the acoustic transducer.

Table 3 shows the samples of signals s ₂ (t), which are the result of the convolution of signals s ₀ (t) and s ₁ (t).

The method for determining the liquid level in the annular space of oil producing wells is implemented using the device shown in Fig. 2, which contains a series-connected acoustic transducer 1 (AD), analog-to-digital transducer 2 (ADC), matrix cascaded correlator 3 (MKK), microprocessor controller 4 (MK), control and indication device 5 (CID). Control module 6 (MU) is connected to a controlled acoustic signal conditioner 7 (UVAS) with an electromagnetic valve and to a cascaded matrix correlator 3 (MCC).

Acoustic transducer 1 (AP) of an acoustic signal into an electric signal can be performed based on, for example, a piezoceramic element.

Analog-to-digital converter 2 (ADC) can be implemented on the MAX189AEPP chip.

Matrix cascaded correlator 3 (MCC) can be implemented on the chip 1846PF1T.

Microprocessor controller 4 (MK) can be performed on microprocessor 1821VM85.

The control and indication device 5 (CID) is based on the IV-28 indicator and the KMD-1 button.

The control module 6 (MU) can be implemented on the microprocessor 1821VM85.

As a controlled driver of the acoustic signal 7 with an electromagnetic valve, an automatic generation and reception device manufactured by SIAM LLC [Automatic generation and reception device UGP machine 2 can be used. Passport. Technical description. ISM 5.173.021 PS, 2004].

To illustrate the implementation of the method, the data obtained during the inspection of well 717 (well 9) of the Sovetskoye field (Strezhevoy) on February 17, 2005 are presented. The pressure in the well at the time of the survey was 15.1 atm, the speed of sound in the annulus gas was 350 m / s. The data sampling period is 2 ms, the examination time is 16.382 s. All signals in this examination contained 8,191 counts. In tables 1, 2, 3 only 30 first samples of signals are presented. On the diagrams 1, 2, 3 (Figs. 3, 4, 5), as many samples are presented as necessary to illustrate signal sections that carry information useful from the point of view of the proposed method.

Control module 6 (MU) generates an electrical signal s ₀ (t) (Table 1), defined by expressions (1) and (2) with parameters: N = 15, T ₀ = 24 counts, μ = 50. The graph of this signal is shown in diagram 1 (figure 3). This signal is fed to a controlled acoustic signal driver 7 (FAS) (Fig. 2). Under the action of the signal, the electromagnetic valve of the controlled acoustic signal conditioner 7 (UVAS) is activated, and an acoustic signal is generated in the annular space of the well, which propagates through the annular space of the well, is reflected from the liquid, and returns back to the wellhead, where it is received by acoustic transducer 1 (AP) and converted to an electrical signal s ₁ (t).

The signal received by the acoustic transducer 1 (AP) is shown in diagram 2 (figure 4). The converted signal s ₁ (t) enters the analog-to-digital Converter 2 (ADC) (figure 2), where it is sampled and digitally encoded.

Simultaneously with the supply of the signal from the control module 6 (MU) to the controlled acoustic signal former 7 (UVAS), the signal (Fig. 3) is also supplied to the cascaded matrix correlator 3 (MCC). At the same time, a signal from the output of the analog-to-digital converter 2 (ADC) is supplied to the other input of the cascaded matrix correlator 3 (MCC). Correlator 3 (MKK) calculates the convolution of these two signals according to the formula [Cook C., Bernfeld M. Radar signals. - M .: Soviet Radio, 1971. - S. 32-33]:

where t is the time

τ is the time by which the signal s ₁ (t) is delayed relative to s ₀ (t) during the convolution operation.

The result of this convolution s ₂ (t) is shown in table 3 and in diagram 3 (Fig. 5). This diagram shows that the ratio of the power of the reflected signal to the noise power has increased significantly compared to the unprocessed signal (plot 2 in figure 4).

From the matrix cascaded correlator 3 (MKK), the signal enters the microprocessor controller 4 (MK), which determines the temporary position of this pulse relative to the moment of formation of the acoustic signal in the annulus. The algorithm of this calculation is based on the search for the maximum value of the reflected signal. In table 3, in the region of the reflected signal, the reference number N _m is selected, which corresponds to the largest modulus of the signal value. In the presented example, this number is 4303. The temporary position of the reflected pulse, taking into account the specified sampling period ΔT, is calculated as follows:

Then the microprocessor controller 4 (MK) calculates the liquid level H by multiplying the temporal position of the reflected pulse T _m and the known sound velocity in the oil gas of the well ν and dividing this product by 2:

The calculated value of the liquid level is displayed by the control and indication device 5 (CID).

Thus, the proposed method for determining the liquid level in the annular space of oil producing wells allows you to control the liquid level in oil wells with a high signal-to-noise ratio, which reduces the likelihood of error in determining the level, and, therefore, increases labor productivity in service enterprises engaged in determining the level fluid in the wells.

The method for determining the liquid level in the annulus of oil production wells

Table 1 table 2 Table 3 Reference Number N Signal value, s ₀ (t) rel. Reference Number N Signal value, s ₁ (t) rel. Reference Number N Signal value, s ₂ (t) rel. one 2000 one 0 one -277.64 2 2000 2 -7 2 -257.62 3 2000 3 -fifteen 3 -249.52 four 2000 four -2 four -298.8 5 2000 5 28 5 -362.41 6 2000 6 twenty 6 -433.61 7 2000 7 21 7 -401.47 8 2000 8 fifteen 8 -416.38 9 2000 9 62 9 -447.64 10 2000 10 44 10 -460.43 eleven 2000 eleven 32 eleven -445.72 12 2000 12 2 12 -485.34 13 2000 13 fourteen 13 -504.86 fourteen 2000 fourteen 24 fourteen -601.78 fifteen 2000 fifteen 43 fifteen -628.95 16 2000 16 56 16 -676.64 17 2000 17 48 17 -694.57 eighteen 2000 eighteen -twenty eighteen -723.58 19 2000 19 -eleven 19 -719.23 twenty 2000 twenty 68 twenty -735.47 21 2000 21 -39 21 -732.76 22 2000 22 -28 22 -590.99 23 2000 23 22 23 -527.7 24 2000 24 57 24 -560.23 25 2000 25 -fourteen 25 -634.77 26 0 26 -3 26 -573.21 27 0 27 -17 27 -461.68 28 0 28 88 28 -277.64 29th 0 29th 83 29th -257.62 thirty 0 thirty 85 thirty -249.52

Claims (1)

A method for determining a fluid level in an annulus of oil producing wells, including generating an acoustic signal at a wellhead in an annulus, converting an acoustic signal reflected from a fluid into an electric signal, determining a sound propagation time from a wellhead to a fluid level, determining a fluid level by a product of a sound propagation time from wellhead to a liquid level at a known sound velocity in the oil gas of a well and dividing this product by two, I distinguish which forms a signal

where a is the amplitude of the pulses in the series; t is the time; N is the number of pulses in the series; T is the pulse duration; u (t, Т) is a rectangular momentum defined by the expression

moreover, the difference t - t _n sets the beginning of the nth pulse in the series, and with T _{n the} duration of the nth pulse in the series, changing t _n and T _n according to the expressions t _n = 2T ₀ n + μn ² ; T _n = T ₀ + μn, where T ₀ is the duration of the first pulse in the series; μ - parameter determining changes in duration and position pulses in a series, and the signal s ₀ (t) is supplied to the acoustic signal shaper to generate it, after converting the acoustic signal reflected from the liquid into electric, it is subjected to analog-to-digital conversion, the signal s ₀ (t) is subjected to a convolution operation with the digitized reflected signal s ₁ (t) , then determine the temporary position of the signal reflected from the liquid relative to the moment of formation of the acoustic signal in the annulus, using which determine the liquid level.

Images