CN105930932B - Acquisition Method of Standardized Open Flow of Shale Gas Reservoir Based on Gas Content Index - Google Patents

Abstract

The invention relates to a method for obtaining the standardized unobstructed flow rate of shale gas layers based on the gas content index, obtaining the parameters of the shale gas layer in the horizontal section of the shale gas horizontal well that has been tested in the work area, and obtaining the shale gas layer in the horizontal section of the tested shale gas horizontal well Fracturing parameters, obtain the unimpeded flow rate of the shale gas layer in the horizontal section of the tested shale gas horizontal well through the test productivity data; calculate the fracturing index and standardization of the shale gas layer in the horizontal section of the tested shale gas horizontal well through the obtained parameters For open flow rate and gas index, determine the model coefficients a and b of model I _AOF = a×e ^b×Ig by the least square method; obtain the shale gas layer parameters in the horizontal section of the well to be predicted in the work area, and calculate the shale gas in the horizontal section to be predicted gas-bearing index; use the model I _AOF 1=a×e ^b×Ig1 to calculate the normalized open flow of the shale gas layer in the horizontal section to be predicted; draw the vertical profile of the normalized open flow of the shale gas layer of the well to be predicted, and output the calculation of the open flow result. Average error ≤ 20%.

Description

Acquisition Method of Standardized Open Flow of Shale Gas Reservoir Based on Gas Content Index

technical field

The exploration and development of shale gas has become the focus of the world, and the United States and Canada have carried out commercial exploitation of shale gas in many basins. Similarly, my country's major basins and regions are rich in shale gas resources. Studies have shown that the amount of shale gas resources in the Sichuan Basin alone is equivalent to more than 1.5 times the amount of conventional natural gas resources in my country's basins. Therefore, my country is rich in shale gas resources and has broad prospects for exploration and development.

Shale gas exploration and development is a world-class technical problem. At present, great progress has been made in China in terms of shale gas accumulation mechanism, resource potential, and reservoir evaluation, but the research on productivity analysis of shale gas horizontal wells is still in its infancy, especially the open flow rate of shale gas horizontal wells. Most of the acquisition aspects remain in the theoretical research stage. The traditional gas well open flow acquisition methods are mainly aimed at sandy mudstone and carbonate rocks, and the results of these methods in shale are not ideal.

Background technique

Unimpeded flow prediction is a very important link in natural gas exploration and development. It is a comprehensive evaluation index for reservoir quality, oil-bearing properties of reservoir fluid and its oil production capacity, and it is also one of the most important indexes.

Shale gas refers to the accumulation of natural gas mainly located in dark mud shale or high-carbon mud shale, mainly in the state of adsorption or free. Shale gas reservoirs are characterized by ultra-low porosity and permeability; and part of the gas is adsorbed on the surface of reservoir rock particles and exists in the reservoir in an adsorbed state, which brings difficulties to the interpretation and evaluation of shale gas. Shale gas wells require large-scale fracturing before they are put into production, which leads to more special and complex factors affecting the productivity of shale gas reservoirs than conventional gas reservoirs.

The traditional absolute open flow acquisition methods are mainly one-point method and pseudo-pressure method, which are realized by means of well testing. These are to establish the open flow equation under the determination of the original gas reservoir pressure. For shale gas reservoirs, due to the complex seepage mechanism, it is difficult to establish an applicable open flow model by these methods.

Contents of the invention

The purpose of the present invention is to aim at the above-mentioned technical status, aiming to provide a simple and convenient method, which can improve the prediction accuracy of shale gas well open flow, and can meet the needs of on-site logging and interpretation of shale gas layer standardized open flow based on gas content index method of obtaining .

The way to achieve the object of the present invention is, based on the method for obtaining the standardized unimpeded flow rate of shale gas formations with gas index, the specific steps are:

1) Obtain parameters of shale gas layers in the horizontal section of shale gas horizontal wells tested in the work area through logging data. The specific parameters are gas layer thickness H, horizontal well section length L, pressure coefficient Kf, porosity POR, and gas saturation Sg and organic carbon content TOC;

2) Obtain the fracturing parameters of the shale gas layer in the horizontal section of the tested shale gas horizontal well, the specific parameters are the volume of fracturing fluid Vf and the volume of fracturing support agent Vs;

3) Obtain the open flow AOFg of the shale gas layer in the horizontal section of the tested shale gas horizontal well through the test productivity data;

4) Use the parameters obtained in step 1), step 2) and step 3) to calculate the fracturing index IFR, standardized open flow rate I _AOF , and gas index Ig of the shale gas layer in the horizontal section of the tested shale gas horizontal well in sequence. The formula is as follows:

IFR=(Vf+Vs)/10000,

I _AOF = AOFg/L/IFR,

Ig=H×Kf×POR×Sg×TOC;

In the formula: the fracturing fluid volume Vf dimension is m ³ ,

The volume of fracturing support agent Vs dimension is m ³ ,

The fracturing index IFR dimension is 10 ⁴ m ³ or 10km ³ ,

The dimension of horizontal well section length L is hm or 100m,

The dimension of thickness H is m,

The dimension of open flow AOFg is 10 ⁴ m ³ /d,

The dimension of standardized open flow I _AOF is 10 ⁴ m ³ /d/hm/10 ⁴ m ³ ,

The dimension of thickness H is m,

The pressure coefficient Kf is dimensionless,

The dimensions of porosity POR and gas saturation Sg are decimals,

The dimension of organic carbon content TOC is %;

5) Determine the model coefficients a and b of the model I _AOF = a×e ^b×Ig by using the least square method to determine the calculated standardized open flow rate I _AOF and the gas index Ig calculated for the corresponding well test;

6) Obtain the parameters of the shale gas layer in the horizontal section of the horizontal well to be predicted in the work area through the logging data. The specific parameters are gas layer thickness H 1, pressure coefficient Kf 1, porosity POR 1, gas saturation Sg 1 and organic carbon content TOC 1;

7) Using the parameters obtained in step 6) to calculate the gas content index Ig1 of the shale gas layer in the horizontal section of the horizontal well to be predicted;

8) Using the model I _0OF 1=a×e ^b×Ig1 to calculate the standardized open flow rate I _AOF 1 of the shale gas layer in the horizontal section of the horizontal well to be predicted;

9) Draw the normalized open flow vertical profile of the shale gas layer of the well to be predicted, and output the calculation results of the open flow rate of the shale gas layer in the horizontal section of the horizontal well to be predicted.

The invention solves the problem of low accuracy and poor reliability of the traditional open flow acquisition method in predicting the open flow of the shale gas layer of the horizontal well, and is simpler, lower in cost and more practical on site than the traditional open flow acquisition method .

The present invention has been applied to 25 wells in a certain shale gas field. The standardized open flow of the shale gas layer calculated by the present invention is close to the normalized open flow obtained by on-site fracturing gas testing, and the average error is not more than 20%. To meet the needs of predicting on-site standardized unobstructed flow.

Description of drawings

Fig. 1 is the workflow block diagram of the present invention,

Fig. 2 is the cross diagram of standardized unobstructed flow rate and gas index of 10 wells in F shale gas field of the present invention,

Fig. 3 is a vertical section view of the normalized unimpeded flow rate of shale gas formations in Well S3HF.

Fig. 4 is a vertical section view of the normalized open flow in the shale gas formation of Well S8HF.

Detailed ways

With reference to Fig. 1, concrete steps of the present invention are:

1) Obtain the shale gas layer parameters of the tested shale gas horizontal wells in the work area through logging data. The specific parameters are gas layer thickness H, horizontal well section length L, pressure coefficient Kf, porosity POR, and gas saturation Sg and organic carbon content TOC;

2) Obtain the fracturing parameters of the shale gas layer in the horizontal section of the tested shale gas horizontal well, the specific parameters are the volume of fracturing fluid Vf and the volume of fracturing support agent Vs;

3) Obtain the open flow AOFg of the horizontal section of the tested shale gas horizontal well through the test productivity data;

4) Using the parameters obtained in step 1) and step 2), the shale gas layer fracturing index IFR, standardized open flow rate I _AOF and gas index Ig of the horizontal section of the tested shale gas horizontal well are sequentially calculated;

5) Calculate the normalized open flow rate I _AOF of the shale gas layer in the horizontal section of the tested shale gas horizontal well and the gas index Ig calculated by the corresponding tested well to determine the model I _AOF = a×e ^b×Ig by the least square method The model coefficients a, b of

6) Obtain the parameters of the shale gas layer in the horizontal section of the shale gas horizontal well to be predicted in the work area through logging data. The specific parameters are gas layer thickness H1, pressure coefficient Kf1, porosity POR1, gas saturation Sg1 and organic carbon Content TOC 1;

7) Using the parameters obtained in step 6) to calculate the gas-bearing index Ig1 of the shale gas layer in the horizontal section of the shale gas horizontal well to be predicted;

8) Using the model I _AOF 1=a×e ^b×Ig1 to calculate the standardized open flow I _AOF 1 of the shale gas layer in the horizontal section of the horizontal well to be predicted;

9) Draw the normalized open flow vertical profile of the shale gas layer of the well to be predicted, and output the calculation results of the standardized open flow of the well to be predicted.

The present invention is described in detail below with specific examples.

Example 1: Well S3HF in F shale gas field, verifying the calculation results of standardized open flow.

1) Obtain 10 tested horizontal wells in F shale gas field (S1H well, S1-2H well, S1-3HF well, S6-2HF well, S7-2HF well, S8-2HF well, S9-2HF well Well, Well S10-2HF, Well S11-2HF, Well S12-3HF) the gas layer thickness H, the length of the horizontal well section L, the pressure coefficient Kf, the porosity POR, the gas saturation Sg and the organic Carbon content TOC;

2) Obtain the fracturing fluid volume Vf and fracturing support agent volume Vs used for fracturing shale gas reservoirs in the horizontal section of 10 tested shale gas horizontal wells;

3) Obtain the open flow AOFg of the shale gas layer in the horizontal section of 10 tested shale gas horizontal wells through the test productivity data;

4) According to the parameters obtained in step 1), step 2) and step 3), the gas layer fracturing stimulation index IFR, standardized open flow rate I _AOF and gas index Ig of 10 wells that have been tested are calculated in sequence;

5) Determine the model coefficients a=0.348 and b=0.2496 of the model I _AOF =a×e ^b×Ig by the least squares method using the standardized open flow I _AOF calculated in step 4) and the calculated gas index Ig (see Figure 2 );

6) The parameters of the shale gas layer in the horizontal section of the horizontal well S3HF were obtained through logging data. The average thickness H1 of the gas layer in the S3HF well was 40m, the average pressure coefficient Kf1 was 1.45, the average porosity POR1 was 0.055, and the average gas saturation Sg1 is 0.552, and the average organic carbon content TOC1 is 2.36%;

7) Calculate the gas content index Ig1 of the gas layer in the horizontal section of the well S3HF well to be predicted by the parameters obtained in step 6) to be 4.16;

8) Using model I _AOF 1=a×e ^{b×Ig1 to} calculate the standardized open flow rate of the shale gas layer in the horizontal section of the S3HF well;

9) Output the calculation results and draw the normalized open flow vertical profile of the shale gas formation in Well S3HF (see Fig. 3). The average normalized open flow I _AOF 1 calculated by Well S3HF is 0.982×10 ⁴ m ³ /d/hm/10 ⁴ m ³ . Well S3HF well completion fracturing gas test obtained a shale gas layer open flow rate of 40.01×10 ⁴ m ³ /d, the horizontal well section was 13.98hm (1398m), and the total volume of fracturing fluid and support agent used was 2.96×10 ⁴ m ^3. The standardized unobstructed flow rate converted into shale gas formations is 0.967×10 ⁴ m ³ /d/hm/10 ⁴ m ³ , with an error of 1.6%, which is less than 20%. Traffic forecasting needs.

Example 2: Well S8HF in F shale gas field, verifying the calculation error of shale gas horizontal well open flow prediction using the standardized open flow of shale gas reservoirs.

1) Well S8HF is a shale gas exploration well in F shale gas field, and the coefficients a=0.348 and b=0.2496 of model I _AOF =a×e ^b×I in Example 1 can be used;

2) The parameters of the shale gas layer in Well S8HF were obtained by logging data. The thickness H of the shale gas layer in the 2781-2825m section of Well S8HF is 44m, the pressure coefficient Kf is 1.45, and the porosity POR, containing The gas saturation Sg and the organic carbon content TOC are used to calculate the gas index Ig, and then the normalized open flow rate I _AOF of the shale gas layer is calculated based on the gas index Ig, and a continuous vertical profile of the normalized open flow rate of the shale gas layer is drawn (see Fig. 4) ;

3) Calculate the average normalized open flow rate of shale gas formations in the 2781-2825m section of Well S8HF to be 0.71×10 ⁴ m ³ /d/hm/10 ⁴ m ³ .

4) Output calculation results, the average normalized open flow rate of the 2781-2825m gas zone in Well S8HF is 0.71×10 ⁴ m ³ /d/hm/10 ⁴ m ³ ), the total volume of fracturing fluid and support agent used in the fracturing operation is 4.0×10 ⁴ m ³ , and the normalized open flow rate of the shale gas layer in the horizontal section of the sidetracked horizontal well is predicted to be 0.71×15.07× 4.0＝42.8(10 ⁴ m ³ /d), the gas layer sidetracking horizontal well horizontal section test obtained 48.5×10 ⁴ m ³ /d open flow rate, the prediction error is 11.8%, less than 20.0%, in line with the field test The unimpeded flow prediction of shale gas reservoirs is required for mud logging interpretation work.

Claims (1)

1. The method for obtaining the standardized unobstructed flow rate of shale gas formations based on the gas content index is characterized in that: the specific steps are: 1) Obtain parameters of shale gas layers in the horizontal section of shale gas horizontal wells tested in the work area through logging data. The specific parameters are gas layer thickness H, horizontal well section length L, pressure coefficient Kf, porosity POR, and gas saturation Sg and organic carbon content TOC; 2) Obtain the fracturing parameters of the shale gas layer in the horizontal section of the tested shale gas horizontal well, the specific parameters are the volume of fracturing fluid Vf and the volume of fracturing support agent Vs; 3) Obtain the open flow AOFg of the shale gas layer in the horizontal section of the tested shale gas horizontal well through the test productivity data; 4) Using the parameters obtained in step 1), step 2) and step 3), calculate the shale gas layer fracturing index IFR, standardized open flow rate I _AOF , and gas index Ig in the horizontal section of the tested shale gas horizontal well in sequence, The specific formula is as follows: IFR=(Vf+Vs)/10000, I _AOF = AOFg/L/IFR, Ig=H×Kf×POR×Sg×TOC; In the formula: the fracturing fluid volume Vf dimension is m ³ , The volume of fracturing support agent Vs dimension is m ³ , The fracturing index IFR dimension is 10 ⁴ m ³ or 10km ³ , The dimension of horizontal well section length L is hm or 100m, The dimension of thickness H is m, The dimension of open flow AOFg is 10 ⁴ m ³ /d, The dimension of standardized open flow I _AOF is 10 ⁴ m ³ /d/hm/10 ⁴ m ³ , The dimension of thickness H is m, The pressure coefficient Kf is dimensionless, The dimensions of porosity POR and gas saturation Sg are decimals, The dimension of organic carbon content TOC is %; 5) Determine the model coefficients a and b of the model I _AOF = a×e ^b×Ig by using the least square method to determine the calculated standardized open flow rate I _AOF and the gas index Ig calculated for the corresponding well test; 6) Obtain the parameters of the shale gas layer in the horizontal section of the horizontal well to be predicted in the work area through logging data, the specific parameters are gas layer thickness H1, pressure coefficient Kf1, porosity POR1, gas saturation Sg1 and organic carbon content TOC1; 7) Using the parameters obtained in step 6) to calculate the gas content index Ig1 of the shale gas layer in the horizontal section of the horizontal well to be predicted; 8) Using model I _AOF 1=a×e ^b×Ig1 to calculate the standardized open flow rate of the shale gas layer in the horizontal section of the horizontal well to be predicted; 9) Draw the vertical profile of the standardized open flow of the well to be predicted, and output the calculation results of the standardized open flow of the shale gas layer in the horizontal section of the horizontal well to be predicted.