CN114753829B - A new method for calculating water holdup of horizontal wells based on array holdup meter - Google Patents

Abstract

The invention relates to a novel method for calculating the water holdup of a horizontal well based on an array holdup meter, which is an accurate and effective means for evaluating the water holdup of a shaft of the horizontal well for unconventional oil and gas reservoir development. The water retention rate value of each array probe position is calculated by acquiring response values of the array probes in full oil, full water and full gas environments and combining actual array water retention logging data and adopting a scale method, and then the water retention rate of the horizontal shaft is calculated by combining the method. The invention considers the instrument structure, instrument rotation in the logging process, contribution difference of different probes and fluid property influence, can conveniently and accurately calculate the water holdup of the horizontal shaft, and lays a foundation for grasping production dynamics of various producing layers of unconventional oil and gas reservoirs and optimizing and adjusting development schemes in the next stage.

Description

A new method for calculating water holdup of horizontal wells based on array holdup meter

Technical Field

The present invention relates to a method for calculating the water holdup of a horizontal well, and in particular to a method for quantitatively calculating the water holdup during the multiphase flow of oil, gas and water in a wellbore during the development of horizontal wells in unconventional oil and gas reservoirs, based on monitoring data of a horizontal well array holdup logging instrument. The method is an accurate and feasible method for evaluating the water holdup of a horizontal well.

Background technique

With the increasing global demand for oil and gas resources and the increasing depletion of conventional oil and gas reservoirs, unconventional oil and gas resources represented by tight oil and gas, shale oil and gas, etc. have gradually become a hot spot for exploration and development. Different from conventional oil and gas reservoirs, the permeability of the overburden matrix of tight oil and gas reservoirs, shale oil and gas reservoirs, etc. is generally less than or equal to 0.1mD, and the reservoir properties are extremely poor. Horizontal well technology is currently the most preferred method for exploiting such oil and gas reservoirs. In the process of horizontal well development, accurately obtaining the oil, gas, and water production of each production layer is the key basis for understanding the production dynamics of oil and gas reservoirs and guiding the optimization and adjustment of the next stage development plan, and water holdup is an important parameter for evaluating the production dynamics of each phase of the horizontal well production layer.

Due to the special wellbore structure of horizontal wells, the differences in the properties of the oil, gas and water multiphase fluids in the wellbore and the gravity differentiation effect, the distribution of multiphase fluid media in the horizontal wellbore is stratified. The single-probe center water holdup meter used in conventional vertical wells cannot be used to monitor the distribution information of multiphase fluid media in horizontal wells. At present, the most representative water holdup monitoring of horizontal wells is the array capacitance water holdup meter CAT, array resistance water holdup meter RAT of Sondex and array resistance water holdup meter AFR of Hunter. The corresponding water holdup meter is 12 array distribution probes opened in the well in an umbrella shape. The probes surround the cross section of the well. The check adjusts the opening radius according to the extension and contraction of the spring arm. This instrument structure can more accurately monitor the fluid distribution information in the horizontal wellbore, and the quantitative calculation of the water holdup of horizontal wells based on the corresponding monitoring signal has become the key basis for the subsequent dynamic evaluation of oil and gas well production. According to the literature (Richard M. Bateman. Cased-Hole Log Analysis and Reservoir Performance Monitoring (Second Edition). Springer, 1942, 133-140.), the water holdup of a horizontal well is defined as the ratio of the water phase fluid area on the horizontal wellbore cross section to the wellbore cross-sectional area. The volume ratio can be expressed at a certain depth microelement as follows:

Where, Y _w — horizontal well water holdup, decimal;

A _w —the area of water phase fluid in the wellbore cross section, square meters (m ² );

A—total cross-sectional area of the wellbore, square meters (m ² );

d _h — horizontal well depth, meter (m).

For the array holdup monitor, the array probe monitoring signal is the capacitance or point resistivity response value of the local position of the probe. Combined with the response value of the probe in pure water, pure oil and pure gas, the water holdup value in the local area of any probe position can be calculated by the calibration method, which is expressed as:

Where, _Yw,i —water holdup at array probe i (i=1, 2, …, 12) in the horizontal wellbore, decimal;

CPS _i — measured response value of probe i in the horizontal wellbore, count rate per second (CPS);

CPS _w,i — the response value of probe i in full water conditions, count rate per second (CPS);

CPS _h,i —The response of probe i in oil or full gas conditions, counts per second (CPS).

The water holdup of a horizontal well is expressed as a function of the local water holdup of each probe. The method for calculating the water holdup of a horizontal well based on each array probe is usually expressed as:

Wherein, α _i is the weight coefficient of array probe i (i=1, 2, ..., 12) in the horizontal wellbore, a decimal.

At present, the main methods for calculating the water holdup of wellbore based on the water holdup data of array probes in horizontal wells are the average weight method, grid interpolation method and equal height area weight coefficient method. The average weight method uses the weighted average method to obtain the average value of 12 probes, and it is assumed that the contribution of the array probe response to the total water holdup is equal; the selection of the interpolation method in the grid interpolation method is significantly affected by the flow pattern, and the actual calculation results are greatly affected by the selection of the interpolation method; the equal height area weight coefficient method divides the wellbore section into five equal parts according to the longitudinal height, and the proportion of each part to the total area is the weight coefficient of the probe distributed in the area. In the actual horizontal well logging process, the gravity differentiation of the fluid in the wellbore section causes the contribution of each probe to the overall water holdup to be different, and the rotation of the instrument itself during the logging process will cause the relative position of the probes at different depths to change, and the weight of the probe response value to the water holdup will also change accordingly. Therefore, in order to accurately obtain the water holdup of the horizontal wellbore, it is necessary to establish an accurate quantitative calculation method for the water holdup of the horizontal well based on the analysis of the structural characteristics of the array instrument.

Summary of the invention

The present invention aims to provide a new method for calculating the water holdup of a horizontal well based on an array holdup meter. The calculation results, understandings and conclusions obtained thereby enrich the technology and method for calculating the water holdup of a horizontal wellbore based on the monitoring data of the array holdup meter. The water holdup Y _w of the horizontal wellbore calculated by the present invention has the highest consistency with the actual fluid distribution in the wellbore, thereby improving the accuracy of dynamic evaluation of oil, gas and water production in each production layer of horizontal well development in unconventional oil and gas reservoirs.

In order to achieve the above technical objectives, the present invention provides the following technical solutions.

(1) Combined with the array holding rate instrument structure, the 12 probes distributed in the array are projected along the radial direction of the wellbore to the central vertical line. Since the expansion degree of the probe can be adjusted, the distance between the probe and the center of the wellbore is expressed as:

r＝k·R (4)

Where, k is the opening degree of the array probe, decimal;

r—the distance between the array probe and the center point of the wellbore section, meter (m);

R—Horizontal wellbore cross-sectional radius, meter (m).

(2) When the array hold-up logging instrument does not rotate, probe No. 1 is at the top position. After projection, probe No. 2 and probe No. 12, probe No. 3 and probe No. 11, probe No. 4 and probe No. 10, probe No. 5 and probe No. 9, and probe No. 6 and probe No. 8 coincide with each other. Probe No. 6 is at the bottom position. From top to bottom, the probes projected vertically to the center are divided into two equal parts according to the vertical distance. At this time, the circular cross-section of the wellbore is divided into 7 areas. The corresponding area of each area is expressed as,

A ₄ =πR ² -2(A ₃ -A ₂ -A ₁ ) (8)

The water holdup of a horizontal well is expressed as:

Wherein, A ₁ ~ A ₇ —areas represented by the seven regions from top to bottom after the wellbore cross section is cut, in square meters (m ² );

Y _w,1 ~Y _w,12 —Water holdup value at the corresponding position of the array probe, decimal.

(3) When the array hold-up logging instrument rotates and a probe is at the top of the wellbore section, the overall contribution weight of the probe at the top is equal to the weight of probe No. 1 when no rotation occurs. The remaining probes correspond to the intervals when no rotation occurs according to the rotation angle. The specific rotation degree is expressed as,

Where, θ is the rotation angle of the array rate meter probe No. 1, in radians;

[]—integer operator;

N—The number of sectors that the array rate meter probe No. 1 rotates across, an integer.

(3) When the array hold-up logging instrument rotates and no probe rotates to the top of the wellbore section, the projection positions of the array probes in the vertical direction of the wellbore center do not overlap at all. From top to bottom, the probes projected vertically to the center are divided into two equal parts according to the vertical distance. The circular cross section of the wellbore is divided into 12 areas. The corresponding area of each area from top to bottom is expressed as,

A ₆ ＝A ₇ ＝0.5πR ² -A ₅ -A ₄ -A ₃ -A ₂ -A ₁ (16)

The water holdup of a horizontal well is expressed as:

Wherein, A ₁ ~ A ₁₂ —areas represented by the 12 regions from top to bottom after the wellbore cross section is cut, in square meters (m ² ).

Compared with the prior art, the present invention has the following significant advantages: (1) high precision and accurate quantification. By considering the distribution of array probes and the rotation of the instrument during the logging process, high-precision subdivision of the weights of different probe detection areas is achieved. At the same time, the opening degree of the instrument during the logging process is considered, so that the evaluation results are more in line with the actual logging environment; (2) strong operability and wide application range. The established method is suitable for calculating the water holdup under different conditions of the horizontal well array holdup meter, and has a wider range of applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the probe distribution position and radial area division when the array rate meter does not rotate.

FIG2 is a schematic diagram showing the probe distribution positions and radial area division when the array rate meter undergoes arbitrary rotation.

Figure 3 is a diagram showing the effect of array holdup logging data processing in the example.

Detailed ways

Figure 1 is a schematic diagram of the probe distribution position and radial area division when the array rate meter does not rotate. Probe No. 1 is at the top depth of the wellbore section, and probe No. 7 is at the lowest depth of the wellbore section. A1 to A7 are the areas of each region divided from top to bottom of the wellbore.

Figure 2 is a schematic diagram of the probe distribution position and radial area division when the array rate meter rotates arbitrarily. θ is the rotation angle of the array instrument. During the rotation of the instrument, no probe is at the top of the wellbore section. A1 to A12 are the areas of different regions of the wellbore section from top to bottom.

Figure 3 is a diagram showing the effect of array holdup logging data processing in the example.

Applications:

It is known that Well A is a horizontal well in an oil field in western China. The well was drilled to a depth of meters and was put into production on August 18, 2017. The current daily liquid production ^{is 7.96m3} /d, the daily oil production is 1.89t/d, and the water content is 72.1%. On the day of logging, the dynamic liquid level depth in the wellbore was monitored to be 626m. The test was not pumped. The 57mm array holdup logging instrument was used to measure the holdup response curves of each probe in the horizontal section of the well. During the logging process, the array probe opening was 1. Formula (2) was used to calculate the water holdup value of each array probe. The response values of each array probe in full oil, full water and full gas are as follows:

Full oil environment:

CPS _o,1 ＝9693，CPS _o,2 ＝10117，CPS _o,3 ＝9777，CPS _o,4 ＝9852，CPS _o,5 ＝10190，CPS _o,6 ＝10066，CPS _o,7 ＝9994，CPS _o,8 ＝9824，CPS _o,9 ＝9740，CPS _o,10 ＝9856，CPS _o,11 ＝9939，CPS _o,12 ＝9824。

Full water environment:

CPS _w,1 ＝20382，CPS _w,2 ＝19227，CPS _w,3 ＝21247，CPS _w,4 ＝21267，CPS _w,5 ＝19042，CPS _w,6 ＝18270，CPS _w,7 ＝19433，CPS _w,8 ＝21446，CPS _w,9 ＝22593，CPS _w,10 ＝21983，CPS _w,11 ＝19987，CPS _w,12 ＝21227。

Full air environment:

₈ ＝7924，CPS _g,9 ＝7840，CPS _{g ,10} ＝7956 _， CPS _{g,11 ＝ 8039 ，CPS g,12 ＝ 7924 。}

The water holdup of the full flow layer 1775-1780m calculated by the new method is distributed in the range of 68.10-68.81%, with an average of 68.54%; the water holdup of 2025-2031m is distributed in the range of 71.60-71.7%, with an average of 71.63%, which is the highest overall consistency with the actual production water content at the wellhead.

Claims (1)

1. A new method for calculating the water holdup of a horizontal well based on an array holdup meter, characterized in that the specific calculation steps of the new method are as follows: (1) Combined with the array holding rate instrument structure, the 12 probes distributed in the array are projected along the radial direction of the wellbore to the central vertical line. Since the opening degree of the probe can be adjusted, the distance between the probe and the wellbore center is related to the spatial position of the probe; (2) When the array rate meter does not rotate, probe No. 1 is at the top position. After projection, probe No. 2 and probe No. 12, probe No. 3 and probe No. 11, probe No. 4 and probe No. 10, probe No. 5 and probe No. 9, probe No. 6 and probe No. 8 coincide with each other. Probe No. 7 is at the bottom position. From top to bottom, the probes projected vertically to the center are divided into two equal parts according to the vertical distance. At this time, the circular cross-section of the wellbore is divided into 7 areas. The corresponding area of each area is expressed as: A ₄ =πR ² -2(A ₃ -A ₂ -A ₁ ) The water holdup of a horizontal well is expressed as: (3) When the array rate meter rotates and a probe is at the top of the wellbore section, the contribution weight of the probe at the top is equal to the weight of probe No. 1 when no rotation occurs. The remaining probes are determined to be in a one-to-one correspondence with the interval when no rotation occurs according to the rotation angle. The specific rotation degree is expressed as: (4) When the array rate meter rotates and no probe rotates to the top of the wellbore section, the projection positions of the array probes in the vertical direction of the wellbore center do not overlap at all. From top to bottom, the probes projected vertically to the center are divided into two equal parts according to the vertical distance. The circular cross section of the wellbore is divided into 12 areas. The corresponding area of each area from top to bottom is expressed as: A ₆ =A ₇ =0.5πR ² -A ₅ -A ₄ -A ₃ -A ₂ -A _1Then the water holdup of the horizontal well is expressed as: Where, A ₁ ~ A ₁₂ —areas represented by the 12 regions from top to bottom after the wellbore cross section is cut, square meters; Y _w,1 ～Y _w,12 —water holdup value at the corresponding position of the array probe, decimal; Y _w —average water holdup of horizontal wells, decimal; A—total cross-sectional area of the wellbore, square meters; k—array probe opening, the ratio of the array probe position to the center of the wellbore section to the radius of the horizontal wellbore section, decimal; r—the distance between the array probe and the center of the wellbore section, meters; R—horizontal wellbore cross-sectional radius, m; θ—rotation angle of probe No. 1 of array rate meter, radians; []—integer operator; N—number of sectors that the array rate meter No. 1 probe rotates across, integer; i—Array rate meter probe serial number.