Method and device for predicting flowing bottomhole pressure of compact high-water-content gas reservoir gas well

Abstract

The invention belongs to the technical field of oil-gas field development, and particularly relates to a method and device for predicting the flowing bottomhole pressure of a compact high-water-content gas reservoir gas well. In order to solve the problem that the flow bottomhole pressure of an underground throttling gas well cannot be predicted in the prior art due to the fact that the flow bottomhole pressure of the well cannot be predicted in the prior art, the method comprises the following steps of: selecting the actually measured flow bottomhole pressure of the monitored gas well and main control production parameters with higher correlation to the actually measured flow bottomhole pressure from various production parameters; the method comprises the following steps of: firstly, measuring the flowing bottomhole pressure, performing regression fitting on the actually-measured flowing bottomhole pressure, the liquid-gas ratio and the main control production parameters to obtain a flowing bottomhole pressure prediction model, and performing flowing bottomhole pressure prediction on a to-be-measured well through the model, so that the method is not only suitable for flowing bottomhole pressure prediction of an underground throttling gas well of which the flowing bottomhole pressure cannot be monitored, but also suitable for flowing bottomhole pressure prediction of a conventional gas well; the well bottom flowing pressure of the gas well can be accurately predicted, a basis is provided for reasonable development of the gas well, scientific production allocation of the gas well, optimization of a drainage gas production process system and the like, and efficient development of a gas field is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas field development, and particularly relates to a method and device for predicting the bottom-hole flowing pressure of gas wells in tight high-water-cut gas reservoirs. Background Art

[0002] During the development of gas fields, obtaining the bottom-hole flowing pressure of gas wells has always been a top priority in evaluating the potential of gas wells. The existing methods for obtaining the bottom-hole flowing pressure of gas wells mainly rely on on-site bottom-hole flowing pressure tests or inferences using historical measurement data of the well to be measured.

[0003] Chinese Patent Application Publication No. CN114526057A discloses a method and device for determining the bottom-hole flowing pressure of gas wells in tight sandstone gas reservoirs. This method involves predicting the bottom-hole flowing pressure of gas wells. First, it is necessary to construct an equation for the pressure relationship between adjacent zero points in the tubing-casing annulus. Second, it is necessary to determine the relationship between the pressure gradient and pressure based on historical wellbore pressure test data. Finally, iterative calculations are performed according to the pressure relationship equation until the pressure at the bottom-hole position is calculated. When predicting the bottom-hole flowing pressure using this method, on the one hand, a large amount of historical wellbore pressure test data is required, and on the other hand, continuous iterative calculations are required to finally predict the bottom-hole flowing pressure of gas wells. This method requires a lot of data, mostly test data, and the calculation requires continuous iteration and is not simple enough. Since some gas wells in gas fields are under downhole throttling production and bottom-hole flowing pressure tests cannot be carried out, this method cannot predict the bottom-hole flowing pressure of gas wells under downhole throttling production. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for predicting the bottom-hole flowing pressure of gas wells in tight high-water-cut gas reservoirs, so as to solve the problem that existing technologies cannot perform bottom-hole pressure tests on downhole throttling gas wells, resulting in the inability to predict the bottom-hole flowing pressure of such wells.

[0005] To solve the above technical problems, the present invention provides a method for predicting the bottom-hole flowing pressure of gas wells in tight high-water-cut gas reservoirs. The specific steps include:

[0006] 1) Obtain the measured bottom-hole flowing pressure and various production parameters of several monitored wells; analyze the correlation between each production parameter and the measured bottom-hole flowing pressure, and screen out the production parameters with relatively high correlation with the measured bottom-hole flowing pressure from each production parameter, which are called the main control production parameters;

[0007] 2) Establish a regression relationship between the main control production parameters, the liquid-gas ratio, and the bottom-hole flowing pressure, where the main control production parameters and the liquid-gas ratio are independent variables in the regression relationship, and the measured bottom-hole flowing pressure is the dependent variable in the regression relationship; use the parameter data of the monitored wells that have been obtained to determine the regression coefficients corresponding to the main control production parameters and the liquid-gas ratio in the regression relationship, so as to obtain the bottom-hole flowing pressure prediction model;

[0008] 3) Use the bottom-hole flowing pressure prediction model to predict the bottom-hole flowing pressure of the well to be measured.

[0009] The beneficial effects are as follows: To solve the problem that the bottom-hole pressure of downhole throttling gas wells cannot be measured, resulting in the inability of the existing technology to predict the bottom-hole flowing pressure of such wells, the present invention selects the measured bottom-hole flowing pressure of the monitored gas well and the main control production parameters with a relatively high correlation with the measured bottom-hole flowing pressure from various production parameters, and then performs regression fitting on the measured bottom-hole flowing pressure, liquid-gas ratio, and main control production parameters to obtain a bottom-hole flowing pressure prediction model. Through this model, the bottom-hole flowing pressure of the well to be measured can be predicted. The present invention can predict the bottom-hole flowing pressure of the well to be measured without the pressure test data of the well to be measured, and is not only applicable to the bottom-hole flowing pressure prediction of downhole throttling gas wells where the bottom-hole pressure cannot be monitored, but also applicable to the bottom-hole flowing pressure prediction of conventional gas wells. It can accurately predict the bottom-hole flowing pressure of gas wells, providing a basis for the reasonable development of gas wells, scientific gas production allocation, and optimization of the drainage gas production process system, and promoting the efficient development of gas fields.

[0010] Further, the regression relationship fitting is a multiple non-linear regression fitting relationship, and its formula is as follows:

[0011] P f-pred = a 1 I 1 + a 2 I 2 + a 3 I 3 +…+ a n-j ln(I n-j )+…a n-2 ln(I n-2 )+ a n-1 ln(I n-1 )+ a n R w / g

[0012] Among them, P f-pred is the predicted bottom-hole flowing pressure; a 1 , a 2 , a 3 …a n are the coefficients of each main control production parameter obtained during fitting; I 1 , I 2 , I 3 …I n-1 are each main control production parameter; j is a natural number between 1 and n; R w / g is the liquid-gas ratio; n is the total number of main control production parameters and the liquid-gas ratio.

[0013] The beneficial effects are as follows: By performing multiple non-linear regression fitting with this formula, when predicting the well to be measured, the prediction efficiency can be improved while reducing the amount of calculation, and the bottom-hole flowing pressure of the well to be measured can be predicted through simple calculations.

[0014] Furthermore, the correlation between the measured bottom-hole flowing pressure and each production parameter is analyzed through a sensitive factor cross-plot.

[0015] The beneficial effects are as follows: By using this method, the high or low correlation between the measured bottom-hole flowing pressure and each production parameter can be quickly and intuitively obtained from the image, and the production parameters with low correlation can be excluded, which is beneficial to reducing the amount of calculation during prediction, improving the calculation efficiency during prediction, and improving the prediction accuracy.

[0016] Furthermore, each production parameter includes tubing head pressure, casing pressure, daily gas production, and daily liquid production.

[0017] The beneficial effects are as follows: Generally, there is a relatively high correlation between the above-mentioned various production parameters and the measured bottom-hole flowing pressure. Therefore, the above-mentioned types of production parameters are selected for correlation screening to improve the efficiency of screening out production parameters with high correlation.

[0018] Furthermore, when the coincidence rate of the bottom-hole flowing pressure prediction model is higher than the set coincidence threshold, it is considered that the prediction accuracy meets the requirements. The coincidence rate is calculated by the following means: Substitute the main control production parameters and liquid-gas ratio in several monitored wells obtained into the bottom-hole flowing pressure prediction model to obtain the predicted bottom-hole flowing pressure, compare the predicted bottom-hole flowing pressure with the measured bottom-hole flowing pressure, and calculate the ratio of the number of monitored wells with an error value less than or equal to the set error threshold to the total number of monitored wells, that is, the coincidence rate.

[0019] The beneficial effects are as follows: Verifying the obtained bottom-hole flowing pressure prediction model is beneficial to obtaining a more accurate bottom-hole flowing pressure prediction model, preventing inaccurate prediction, and is beneficial to the development and production allocation of gas wells.

[0020] Furthermore, when the following conditions are met, the bottom-hole flowing pressure prediction step is re-executed to correct the current bottom-hole flowing pressure prediction model: If after obtaining the main control production parameters, liquid-gas ratio, and measured bottom-hole flowing pressure of a new monitored well and substituting them into the current bottom-hole flowing pressure prediction model, the proportion of the number of monitored wells with an error value less than or equal to the set error threshold is less than the set coincidence threshold.

[0021] The beneficial effects are as follows: When the number of monitored wells increases and the parameters become more abundant, and it is found that the current prediction model does not meet the requirements, this method is used for further processing to obtain a prediction model with higher prediction accuracy, further improving the accuracy of the bottom-hole flowing pressure prediction of gas wells, and being beneficial to the reasonable and efficient development of gas wells.

[0022] To solve the above technical problems, the present invention also provides a device for predicting the bottom-hole flowing pressure of a gas well in a tight high-water-content gas reservoir, which includes a memory and a processor. The processor is used to execute computer program instructions stored in the memory to implement the method introduced above.

[0023] Its beneficial effect is that this device ensures the effective and reliable execution of a method for predicting the bottom-hole flowing pressure of a gas well in a tight high-water-content gas reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flowchart of the method for predicting the bottom-hole flowing pressure of a gas well of the present invention;

[0025] Figure 2-1 is a schematic diagram of the intersection of the measured bottom-hole flowing pressure and the tubing head pressure of a gas well in an embodiment of the present invention;

[0026] Figure 2-2 is a schematic diagram of the intersection of the measured bottom-hole flowing pressure and the casing pressure of a gas well in an embodiment of the present invention;

[0027] Figure 2-3 is a schematic diagram of the intersection of the measured bottom-hole flowing pressure and the daily gas production of a gas well in an embodiment of the present invention;

[0028] Figure 2-4 is a schematic diagram of the intersection of the measured bottom-hole flowing pressure and the daily liquid production of a gas well in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The basic concept of the present invention is as follows: The present invention obtains the measured bottom-hole flowing pressure, liquid-gas ratio, and production parameters of the monitored gas well, selects the main control production parameters that have a greater impact on the bottom-hole flowing pressure from the production parameters, performs regression fitting on the measured bottom-hole flowing pressure, liquid-gas ratio, and main control production parameters to obtain a prediction model for the bottom-hole flowing pressure of the gas well, and predicts the bottom-hole flowing pressure of the well to be measured through this model. The principle of the present invention is: After obtaining the measured bottom-hole flowing pressure and production parameters of the monitored gas well, perform a cross-plot analysis of sensitive factors to find the main control production parameters whose correlation coefficient with the measured bottom-hole flowing pressure is greater than or equal to the set threshold, and then perform multiple regression fitting in combination with the measured bottom-hole flowing pressure, liquid-gas ratio, and main control production parameters to obtain a prediction model for the bottom-hole flowing pressure. Substitute the obtained liquid-gas ratio and main control production parameters into this prediction model to obtain the predicted bottom-hole flowing pressure, and compare it with the measured bottom-hole flowing pressure. If the coincidence rate meets the set threshold, substitute the liquid-gas ratio and main control production parameters corresponding to the well to be measured into the prediction model to calculate the predicted bottom-hole flowing pressure of this well to be measured. Based on this concept, a method for predicting the bottom-hole flowing pressure of a gas well in a tight high-water-content gas reservoir and a device for predicting the bottom-hole flowing pressure of a gas well in a tight high-water-content gas reservoir of the present invention can be realized.

[0030] The present invention will be described in detail below in conjunction with the drawings and method embodiments.

[0031] Method Embodiment:

[0032] A method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir according to the present invention has a flow chart as shown in Figure 1 Taking a certain Gas Field A as an example, its specific steps include:

[0033] Step 1: Select 83 gas wells in the gas field with measured bottom-hole flowing pressures, and obtain the measured bottom-hole flowing pressure data, liquid-gas ratio, and corresponding production parameters of these 83 gas wells. Among them, the liquid-gas ratio of the gas field refers to the ratio of natural gas to water in the gas field. During the gas field exploitation process, the liquid-gas ratio is a very important parameter, which directly affects the exploitation efficiency and economic benefits of the gas field. The lower the liquid-gas ratio, the higher the natural gas content in the gas field; the higher the liquid-gas ratio, the higher the water content in the gas field. Especially for tight high-water-content reservoirs, the liquid-gas ratio is an indispensable research index.

[0034] The production parameters of these 83 gas wells include tubing head pressure (P y ), casing pressure (P t ), daily gas production (Q -g ), and daily liquid production (Q -w ). The specific parameters are shown in Table 1 below:

[0035] Table 1

[0036]

[0037]

[0038]

[0039] Step 2: Determine the main controlling production parameters affecting the bottom-hole flowing pressure.

[0040] Respectively plot the tubing head pressure (P y ), casing pressure (P t ), daily gas production (Q -g ), and daily liquid production (Q -w ) of each well against the measured bottom-hole flowing pressure (P f-s ) of its respective well through a cross-plot for sensitivity analysis, and analyze the correlation between each production parameter and the measured bottom-hole flowing pressure. Take the production parameters with high correlation as the main controlling production parameters affecting the bottom-hole flowing pressure. In this embodiment, the correlation coefficient is used to represent the correlation between each production parameter and the measured bottom-hole flowing pressure. Among them, as shown in Figure 2-1 is the cross-plot schematic diagram of the measured bottom-hole flowing pressure (P f-s ) of a gas well and the tubing head pressure (P y ) of the gas well, with the relevant parameter R = 0.8394. Figure 2-2 is the measured bottom-hole flowing pressure (P f-s ) of a gas well in the present invention and the casing pressure (Pt ) intersection schematic diagram, with relevant parameter R = 0.9237, Figure 2-3 is the measured bottom-hole flowing pressure (P f-s ) of the gas well in the present invention and the daily gas production (Q -g ) intersection schematic diagram, with relevant parameter R = 0.4893, Figure 2-4 is the measured bottom-hole flowing pressure (P f-s ) of the gas well in the present invention and the daily liquid production (Q -w ) intersection schematic diagram, with relevant parameter R = 0.6352. In this embodiment, the set relevant parameter threshold is 0.8. Therefore, the selected wellhead oil pressure (P y ) and casing pressure (P t ) are two main production parameters affecting the measured bottom-hole flowing pressure of the gas well.

[0041] Step three, establish a prediction model for the bottom-hole flowing pressure of the gas well according to the main production parameters, bottom-hole flowing pressure and liquid-gas ratio.

[0042] Take the selected main production parameters and the liquid-gas ratio obtained in step one as independent variables, and the measured bottom-hole flowing pressure obtained in step one as the dependent variable to jointly perform multivariate non-linear fitting to establish a prediction model for the bottom-hole flowing pressure of the gas well. Then, substitute the main production parameters and liquid-gas ratio obtained in step one into the prediction model for the bottom-hole flowing pressure to obtain the predicted bottom-hole flowing pressure of each well's data. Compare the predicted bottom-hole flowing pressure with the measured bottom-hole flowing pressure. If the proportion of wells with an error value less than or equal to the set error threshold meets the requirements (i.e., the compliance rate is greater than or equal to the set compliance threshold), then the prediction model can be used for prediction;

[0043] The multivariate non-linear fitting formula is as follows:

[0044] P f-pred = a 1 I 1 + a 2 I 2 + a 3 I 3 +…+ a n-j ln(I n-j )+…a n-2 ln(I n-2 )+ a n-1 ln(I n-1 )+ a n R w / g

[0045] P f-pred is the predicted bottom-hole flowing pressure; a 1 、a 2 、a 3 …a n are the constants of each production parameter obtained during fitting; I 1, I 2 , I 3 …I n-1 wherein, each of the production parameters; j is a natural number between 1 and n;

[0046] The expression of the model obtained by substituting the data in Table 1 into the above formula is as follows:

[0047] P f-pred = 3.0934×ln(P y ) + 4.6683×ln(P t ) + 0.1204×R w / g - 3.2681

[0048] wherein, the calculation formula of the liquid-gas ratio (R w / g ) is:

[0049] R w / g = Q -w / Q -g

[0050] Substitute the wellhead flowing pressure (P y ), casing pressure (P t ) and liquid-gas ratio (R w / g ) of the 83 wells in Table 1 into the above prediction model to predict the bottom-hole flowing pressure of each gas well. The prediction results are shown in Table 2 below:

[0051] Table 2

[0052]

[0053]

[0054]

[0055] wherein, if the error value between the measured bottom-hole flowing pressure (P f-s ) and the predicted bottom-hole flowing pressure (P f-pred ) is within 20%, it is considered to be in line, otherwise it is not in line. As can be seen from Table 2, except for the prediction results of Well J2, Well J30, Well J43 and Well J78 which do not conform, the prediction results of the remaining wells conform, and the conformity rate is 95.18% which is greater than 75%; therefore, the prediction result of this model is accurate and this model can be used for prediction.

[0056] Step 4: Input the production data of the well to be measured into the prediction model obtained in Step 3 for prediction to obtain the bottom-hole flowing pressure of the well to be measured. Moreover, during the later gas field development, more measured data of the bottom-hole flowing pressure of gas wells can be obtained. Compare the measured bottom-hole flowing pressure data with the predicted bottom-hole flowing pressure data. If the error of the prediction result exceeds the acceptable range, add the relevant sensitive main control production parameters, liquid-gas ratio, and measured bottom-hole flowing pressure of this well to the sample database, and re-execute Step 3 to obtain a revised prediction model for the bottom-hole flowing pressure of gas wells in a tight high-water-cut gas reservoir. After more predictions, inspections, and corrections of the bottom-hole flowing pressure of gas wells, the prediction accuracy of the prediction model for the bottom-hole flowing pressure of gas wells in a tight high-water-cut gas reservoir will be continuously improved.

[0057] The present invention is applicable not only to the prediction of the bottom-hole flowing pressure of conventional gas wells, but also to the prediction of the bottom-hole flowing pressure of downhole throttling gas wells where the bottom-hole flowing pressure cannot be monitored. Therefore, it can accurately predict the bottom-hole flowing pressure of gas wells, providing a basis for the rational development of gas wells, scientific gas production allocation, and optimization of the drainage gas production process system, etc., and promoting the efficient development of gas fields.

[0058] Device embodiment:

[0059] A device for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-cut gas reservoir according to the present invention includes a memory and a processor. The processor is used to execute computer program instructions stored in the memory to implement a method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-cut gas reservoir introduced in the method embodiment of the present invention. Among them, the processor can be a processing device such as a programmable logic device FPGA. The memory can be various memories that store information by means of electric energy, such as RAM, ROM, etc., and can also be memories in other ways.

Claims

1. A method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir, characterized in that, the specific steps include: 1) Obtain the measured bottom-hole flowing pressure and various production parameters of several monitored wells; analyze the correlation between each production parameter and the measured bottom-hole flowing pressure, and screen out the production parameters with a relatively high correlation with the measured bottom-hole flowing pressure from each production parameter, which are called the main control production parameters; 2) Establish a regression relationship among the main control production parameters, the liquid-gas ratio, and the bottom-hole flowing pressure, where the main control production parameters and the liquid-gas ratio are independent variables in the regression relationship, and the measured bottom-hole flowing pressure is the dependent variable in the regression relationship; use the parameter data of the monitored wells that have been obtained to determine the regression coefficients corresponding to the main control production parameters and the liquid-gas ratio in the regression relationship, so as to obtain the bottom-hole flowing pressure prediction model; 3) Use the bottom-hole flowing pressure prediction model to predict the bottom-hole flowing pressure of the well to be measured.

2. The method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir according to claim 1, characterized in that, the regression relationship is fitted into a multiple non-linear regression fitting relationship, and its formula is as follows: P f-pred = a 1 I 1 + a 2 I 2 + a 3 I 3 +…+ a n-j ln(I n-j )+…a n-2 ln(I n-2 )+ a n-1 ln(I n-1 )+ a n R w / g Among them, P f-pred is the predicted bottom-hole flowing pressure; a 1 , a 2 , a 3 …a n are the coefficients of each main control production parameter obtained during fitting; I 1 , I 2 , I 3 …I n-1 are each main control production parameter; j is a natural number between 1 and n; R w / g is the liquid-gas ratio; n is the total number of main control production parameters and the liquid-gas ratio.

3. The method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir according to claim 1, characterized in that, analyze the correlation between the measured bottom-hole flowing pressure and each production parameter through a sensitive factor intersection chart.

4. The method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir according to claim 1, characterized in that, each production parameter includes the oil pressure, the casing pressure, the daily gas production, and the daily liquid production.

5. The method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir according to any one of claims 1-4, characterized in that, when the coincidence rate of the bottom-hole flowing pressure prediction model is higher than the set coincidence threshold, it is considered that the accuracy of its prediction meets the requirements, and the coincidence rate is calculated by the following means: substitute the main control production parameters and the liquid-gas ratio in the obtained several monitored wells into the bottom-hole flowing pressure prediction model to obtain the predicted bottom-hole flowing pressure, compare the predicted bottom-hole flowing pressure with the measured bottom-hole flowing pressure, and calculate the ratio of the number of monitored wells with an error value less than or equal to the set error threshold to the total number of monitored wells, that is, the coincidence rate.

6. The method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir according to any one of claims 1-4, characterized in that, when the following conditions are met, re-execute the bottom-hole flowing pressure prediction step to correct the current bottom-hole flowing pressure prediction model: if, after obtaining the main control production parameters, the liquid-gas ratio, and the measured bottom-hole flowing pressure of a new monitored well, the proportion of the number of monitored wells with an error value less than or equal to the set error threshold obtained by substituting them into the current bottom-hole flowing pressure prediction model is less than the set coincidence threshold.

7. A device for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir, characterized in that, it includes a memory and a processor, and the processor is used to execute the computer program instructions stored in the memory to implement the method for predicting the bottom-hole flowing pressure of gas wells in a tight high-water-content gas reservoir according to any one of claims 1-6.

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