Horizontal well transformation section spacing determination method based on tight gas drainage range

Abstract

The invention provides a horizontal well transformation section spacing determination method based on a tight gas drainage range. The horizontal well transformation section spacing determination method comprises the following steps: step 100, determining drainage radiuses of different types of reservoirs of a tight gas horizontal well; 200, the recovery efficiency of different types of reservoirs of the tight gas horizontal well is predicted; step 300, calculating the gas production rate corresponding to the recovery ratio; and step 400, in combination with the transformation cost, evaluating the reasonable section spacing by sections, namely considering the single-section cost, and when the benefit generated by the gas production rate of each section of a certain type of reservoir stratum can support the transformation cost and reach a certain yield, determining that the section spacing of the type of reservoir stratum is the reasonable section spacing. According to the method, differentiation design is carried out on the horizontal well transformation section distance by combining the single-section transformation cost of the horizontal well, the horizontal well section distance is optimized by predicting the drainage radius, the horizontal section seam distribution density is reasonably arranged, and compared with an existing moderate osculating volume fracturing design, the high-quality reservoir fracturing investment can be effectively reduced, the sub-difference reservoir recovery rate can be effectively increased, and the method is suitable for large-scale production. And the yield of the horizontal well can be greatly increased.

Description

Technical Field

[0001] The present invention belongs to the field of horizontal well reconstruction, and specifically relates to a method for determining the interval distance of horizontal well reconstruction sections based on the drainage range of tight gas. Background Art

[0002] China is rich in unconventional oil and gas resources, which are one of the important replacement resources. However, due to the tightness of its reservoirs, industrial production oil and gas flows are mainly obtained through large-scale volume fracturing, and horizontal wells are the main means to expand the drainage range of tight oil and gas and increase the production of single wells.

[0003] In recent years, through the large-scale application of the concept of moderately dense cutting design, the number of fracturing stages per year has been increasing. The number of fracturing stages per single well has increased from 6.7 stages to 10.8 stages, and the interval distance has been shortened from 153 m to less than 100 m. Due to the heterogeneity of the reservoir, the recovery rates of different reservoir sections vary greatly, and a reasonable layout of fracturing sections is of great significance for improving the recovery rate of gas reservoirs.

[0004] Chinese Patent CN202110919793 discloses a method and device for determining the fracture spacing density of horizontal wells in tight sandstone gas reservoirs. By using the in-situ stress data, basic rock mechanics parameters, and core permeability parameters of the target fracturing well section, the fracture spacing and fracture density are calculated, with a focus on engineering data such as in-situ stress, fracture pressure, and minimum horizontal principal stress. However, it does not consider the matrix seepage capacity and drainage range of the reservoir where the horizontal well is located, nor does it evaluate the economy and efficiency of staged fracturing.

[0005] Chinese Patent CN202210111563 discloses a method for differential reconstruction of volume fracturing of horizontal wells, including sorting out the data of horizontal wells in the target block; calculating the weight ratio of each parameter in the data to the initial production capacity of the horizontal well; establishing an evaluation model for fracturing sweet spots of horizontal wells; calculating the average sweet spot degree of the fracturing sections of horizontal wells; plotting a scatter diagram of the average sweet spot degree of the fracturing sections of horizontal wells and the initial production capacity, and fitting the relationship curve; establishing a classification standard for sweet spots and the value range of logging parameters corresponding to various sweet spots in the classification standard; establishing a design template for differential reconstruction of volume fracturing of the horizontal section of a horizontal well; obtaining the distribution of sweet spot degrees of various sweet spots along the horizontal section; and obtaining the differential reconstruction plan for the horizontal well. This invention combines geological sweet spots and initial production capacity to form a differential reconstruction plan, considering the economic efficiency of horizontal well development. However, the parameters for evaluating geological sweet spots are shale content, porosity, and permeability, and it also does not consider the matrix seepage capacity and drainage range of the reservoir where the horizontal well is located. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for determining the interval distance of horizontal well reconstruction sections based on the drainage range of tight gas to overcome the above technical defects.

[0007] To solve the above technical problems, the present invention provides a method for determining the interval distance of the horizontal well reconstruction section based on the gas drainage range of tight gas, including:

[0008] Step 100, determining the drainage radius of different types of reservoirs in the tight gas horizontal well;

[0009] Step 200, predicting the recovery factor of different types of reservoirs in the tight gas horizontal well;

[0010] Step 300, calculating the gas production corresponding to the recovery factor;

[0011] Step 400, combining the reconstruction cost and evaluating the reasonable interval distance by section.

[0012] Determining the drainage radius of different types of reservoirs in the tight gas horizontal well includes:

[0013] Step 101, obtaining the reservoir classification and evaluation criteria established for the block where the target tight gas horizontal well is located;

[0014] Step 102, dividing and determining different types of reservoirs of the target tight gas horizontal well according to the reservoir classification and evaluation criteria;

[0015] Step 103, selecting the cores of different types of reservoirs of the target tight gas horizontal well as experimental cores, and conducting long-core multi-point pressure measurement physical simulation experiments on each experimental core;

[0016] Step 104, drawing a relationship chart of pressure drop and drainage radius of different types of reservoirs of the target tight gas horizontal well according to the experimental results of the long-core multi-point pressure measurement physical simulation experiment;

[0017] Step 105, searching and determining the drainage radius of different types of reservoirs of the target tight gas horizontal well in the chart.

[0018] The prediction of the recovery factor of different types of reservoirs in Step 200 includes:

[0019] Dividing the reservoirs of the same type in the target tight gas horizontal well into i sections, taking the drainage radius r i of the i sections as the x-axis and the original formation pressure P e of the reservoir as the y-axis, drawing a pressure drop funnel distribution map, calculating the unused reservoir energy of the reservoirs of the same type, and obtaining the recovery factor of the i-th section according to the unused reservoir energy of the reservoirs of the same type.

[0020] The calculation formula for calculating the unused reservoir energy of the reservoirs of the same type is as follows:

[0021]

[0022] In the formula, A tIt represents the unused reservoir energy. a and b represent the constants in the relationship formula between pressure drop and drainage radius, and the relationship formula between pressure drop and drainage radius is obtained from the curve of the relationship between pressure drop and drainage radius of different types of reservoirs in the target tight gas horizontal well.

[0023] The recovery factor of the i-th section is obtained according to the unused reservoir energy of the same type of reservoir. The formula is as follows:

[0024]

[0025] E R represents the recovery factor of the i-th section;

[0026] P e represents the original formation pressure of the reservoir.

[0027] The gas production corresponding to the calculated recovery factor in step 300. The calculation formula is as follows:

[0028]

[0029] Q i represents the gas production of the i-th section;

[0030] G i represents the gas storage volume of the i-th section.

[0031] The gas storage volume G of the i-th section i The calculation formula is as follows:

[0032]

[0033] represents the porosity;

[0034] S g represents the gas saturation;

[0035] V r represents the drainage volume.

[0036] Combining the transformation cost in step 400, evaluating the reasonable section spacing by section, including: obtaining the transformation cost Pi of different types of reservoirs of the tight gas horizontal well i改造 , if P i改造 ≤Q i ×P g单价 , then the reasonable section spacing R 合理 = 2r i where P g单价 represents the unit price of natural gas.

[0037] The present invention optimizes the horizontal well section spacing by predicting the drainage radius and rationally arranges the fracture density in the horizontal section. Compared with the existing moderately intensive volume fracturing design, it can effectively reduce the fracturing investment in high-quality reservoirs and improve the recovery rate of sub-quality reservoirs. It is an innovative achievement of the integration of geology and engineering and has great room for improving the production of horizontal wells.

[0038] To make the above content of the present invention more obvious and understandable, the following specifically gives preferred embodiments and, in conjunction with the accompanying drawings, makes a detailed description as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a chart showing the relationship between the pressure drop and the drainage radius of different types of reservoirs in tight gas horizontal wells.

[0040] Figure 2 It is a distribution diagram of the pressure drop funnel.

[0041] Figure 3 It is a schematic diagram of the reservoir encountered by a certain horizontal well.

[0042] Figure 4 It is a schematic diagram of the reservoir fracturing of a certain horizontal well. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0044] It should be noted that in the present invention, the up, down, left, and right in the figure are regarded as the up, down, left, and right in the method for determining the spacing of the horizontal well reconstruction section based on the drainage range of tight gas in this specification.

[0045] Now refer to the accompanying drawings to introduce the exemplary embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary embodiments shown in the accompanying drawings are not limitations on the present invention. In the drawings, the same units / components use the same reference numerals.

[0046] Unless otherwise specified, the terms (including scientific and technical terms) used herein have the ordinary meaning understood by those skilled in the art. In addition, it can be understood that the terms defined in the commonly used dictionary should be understood to have a meaning consistent with the context of their related fields and should not be understood as idealized or overly formal meanings.

[0047] This embodiment relates to a method for determining the spacing of the horizontal well reconstruction section based on the drainage range of tight gas, including:

[0048] Step 100, determine the drainage radius of different types of reservoirs in tight gas horizontal wells;

[0049] Step 200, predict the recovery factor of different types of reservoirs in tight gas horizontal wells;

[0050] Step 300, calculate the gas production corresponding to the recovery factor;

[0051] Step 400, combined with the transformation cost, evaluate the reasonable section spacing by section.

[0052] Regarding determining the drainage radius of different types of reservoirs in tight gas horizontal wells in Step 100, the specific steps are as follows:

[0053] Step 101, obtain the reservoir classification and evaluation criteria established for the block where the target tight gas horizontal well is located.

[0054] The reservoir classification and evaluation criteria are known criteria that have been established for the block where the target tight gas horizontal well is located, so only need to obtain them.

[0055] Step 102, divide and determine different types of reservoirs of the target tight gas horizontal well according to the reservoir classification and evaluation criteria.

[0056] The target tight gas horizontal well here and elsewhere is the well to be tested, that is, the horizontal well for which the reasonable section spacing needs to be determined.

[0057] After obtaining the relevant parameters of the target tight gas horizontal well, it can be divided according to the reservoir classification and evaluation criteria. The relevant parameters here can be effective thickness, permeability, gas saturation, etc., specifically referring to the division parameters of the reservoir classification and evaluation criteria.

[0058] Step 103, select the cores of different types of reservoirs of the target tight gas horizontal well as experimental cores, and conduct long-core multi-point pressure measurement physical simulation experiments on each experimental core.

[0059] Step 104, draw the relationship chart of pressure drop and drainage radius of different types of reservoirs of the target tight gas horizontal well according to the experimental results of the long-core multi-point pressure measurement physical simulation experiment. Please refer to Figure 1 , Figure 1 as an example and not limited to what is shown in the figure.

[0060] Step 105, find and determine the drainage radius of different types of reservoirs of the target tight gas horizontal well in the chart.

[0061] Take Figure 1For example, the target tight gas horizontal wells are divided into four types: I, II, III, and IV. The first three reservoirs with development value are further subdivided into two grades: a and b. When it is known that the original formation pressure of the IIb reservoir is 25 MPa and the bottom-hole flowing pressure is 10 MPa, then the production pressure difference (pressure drop) of the IIb reservoir is 15 MPa. At this time, Figure 1 find the abscissa corresponding to the ordinate of 15 MPa of the IIb reservoir in it, which is 150. Then the drainage radius of the IIb reservoir is 150 m.

[0062] According to the above method, select a certain horizontal well as the target tight gas horizontal well. The horizontal section of this horizontal well is 2,650 m long. Please refer to Figure 3 , drill through 1,800 m of the IIb reservoir and 500 m of the IIIa reservoir; through Figure 1 the chart plate, identify the drainage radius of the IIb reservoir as 150 m and the drainage radius of the IIIa reservoir as 60 m.

[0063] Step 200 predicts the recovery factor of different types of reservoirs in tight gas horizontal wells, including:

[0064] Divide the reservoirs of the same type in the target tight gas horizontal well into i segments. Take the drainage radius r i of the i segments as the x-axis and the original formation pressure P e of the reservoir as the y-axis to draw the pressure drop funnel distribution diagram (refer to Figure 2 ), calculate the energy of the undeveloped reservoir in the same type of reservoir, and obtain the recovery factor of the i-th segment according to the energy of the undeveloped reservoir in the same type of reservoir.

[0065] Before predicting the recovery factor of different types of reservoirs in tight gas horizontal wells, all reservoirs in the tight gas horizontal well need to be regarded as homogeneous reservoirs, that is, assume that the reservoir is relatively homogeneous, and then deploy the fracturing sections according to the reasonable drainage radius based on historical data or experience. The specific embodiments are as follows:

[0066] Please refer to Figure 4 , for the 1,800 m of the IIb reservoir, take i = 6, that is, deploy 6 fracturing sections; for the 500 m of the IIIa reservoir, take i = 4, that is, deploy 4 fracturing sections.

[0067] It should be specifically noted here that Figure 2 the pressure drop funnel distribution diagram shown is only for illustration and does not correspond to Figure 4 the fracturing schematic diagram shown, and Figure 2 the shown is the drainage radius of two adjacent different types of reservoirs.

[0068] Specifically, the calculation formula for calculating the energy of the undeveloped reservoir in the same type of reservoir is as follows:

[0069]

[0070] In the formula, A t represents the unused reservoir energy, and a and b represent the constants of the relationship formula between the pressure drop and the drainage radius, which is obtained from the relationship curve of the pressure drop and the drainage radius of different types of reservoirs in the target tight gas horizontal well.

[0071] Regarding the values of a and b in the above formula, taking Figure 3 and Figure 4 as examples, for the type IIb reservoir, the drainage radius r is 150 m, the original formation pressure is 25 MPa, the bottom-hole flowing pressure is 10 MPa, and the production pressure difference (pressure drop) is 15 MPa. The values of a and b are obtained from the Figure 1 drainage radius fitting formula. Here, a = 5.27 and b = 0.30; for the type IIIa reservoir, the drainage radius r is 60 m. Similarly, the values of a and b are obtained from the Figure 1 drainage radius fitting formula. Here, a = 6.98 and b = 0.32.

[0072] The recovery factor of the i-th section is obtained according to the unused reservoir energy of the same type of reservoir. The formula is as follows:

[0073]

[0074] E R represents the recovery factor of the i-th section;

[0075] P e represents the original formation pressure of the reservoir.

[0076] Since the same type of reservoir is equally divided into i sections, the recovery factor of each section of the same type of reservoir is the same. For example, when a = 5.27 and b = 0.30, E R represents that the recovery factors of the first to sixth sections of the type IIb reservoir are all 39.2%; when a = 6.98 and b = 0.32, E R represents that the recovery factors of the seventh to tenth sections of the type IIIa reservoir are all 12.3%.

[0077] In step 300, calculate the gas production corresponding to the recovery factor. Specifically, it is the prediction of the gas production of each section of the horizontal well. The calculation formula is as follows:

[0078]

[0079] Q i represents the gas production of the i-th section;

[0080] G i represents the gas storage volume of the i-th section.

[0081] Combined with the single-section reservoir parameters of porosity, gas saturation and drainage volume, the calculation formula of the gas storage volume G i of the i-th section is as follows:

[0082]

[0083] represents porosity;

[0084] S g represents gas saturation;

[0085] V r represents the drainage volume.

[0086] For the same type of reservoir, the gas storage volume G of each section i is equal. Therefore Figure 4 in the first to sixth sections, the gas production volume is Q = 39.2% × 7.2 million cubic meters = 2.82 million cubic meters, and in the seventh to tenth sections, the production volume is Q = 12.3% × 0.86 million cubic meters = 0.11 million cubic meters.

[0087] Step 400 combines the transformation cost and evaluates the reasonable section spacing by section, including: obtaining the transformation cost Pi of the i-th section of different types of reservoirs in horizontal wells for tight gas i改造 , if P i改造 ≤Q i ×P g单价 , then the reasonable section spacing R 合理 =2r i , where P g单价 represents the unit price of natural gas.

[0088] For the same type of reservoir, the transformation cost of each section is also the same, and the value of the transformation cost can be obtained according to historical data. Therefore, still taking Figure 4 as an example, if P i改造 is between 0.11 million and 2.82 million, for example, P i改造 is 0.6 million, then obviously, the average production volume of the first to sixth sections can cover the single-section construction cost, while the average production volume of the seventh to tenth sections cannot cover the single-section construction cost. Therefore, it is recommended that the number of fracturing sections for type IIb reservoirs is 6, and the reasonable section spacing R 合理 =2r i =2×150 = 300m.

[0089] Based on the drainage range of tight gas, combined with the single-section transformation cost of horizontal wells, the present invention conducts differential design on the transformation section spacing of horizontal wells, optimizes the section spacing of horizontal wells by predicting the drainage radius, and reasonably arranges the seam density of horizontal sections. Compared with the existing moderately intensive cutting volume fracturing design, it can effectively reduce the fracturing investment in high-quality reservoirs and improve the recovery rate of sub-quality reservoirs. It is an innovative result of the integration of geology and engineering, and has a large room for improving the production volume of horizontal wells.

[0090] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. Method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas, Characterized in that, Comprising: Step 100, determining drainage radius of different types of reservoirs of tight gas horizontal well; Step 200, predicting recovery rate of different types of reservoirs of the tight gas horizontal well; Step 300, calculating gas production corresponding to the recovery rate; Step 400, combining reconstruction cost and evaluating reasonable interval distance by section.

2. The method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas according to claim 1, Characterized in that, Determining drainage radius of different types of reservoirs of tight gas horizontal well includes: Step 101, obtaining reservoir classification and evaluation criteria established for the block where the target tight gas horizontal well is located; Step 102, dividing and determining different types of reservoirs of the target tight gas horizontal well according to the reservoir classification and evaluation criteria; Step 103, selecting cores of different types of reservoirs of the target tight gas horizontal well as experimental cores, and conducting long core multi-point pressure measurement physical simulation experiments on each experimental core; Step 104, drawing a relationship chart of pressure drop and drainage radius of different types of reservoirs of the target tight gas horizontal well according to the experimental results of the long core multi-point pressure measurement physical simulation experiment; Step 105, searching and determining the drainage radius of different types of reservoirs of the target tight gas horizontal well in the chart.

3. The method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas according to claim 2, Characterized in that, Step 200 for predicting the recovery rate of different types of reservoirs of the tight gas horizontal well includes: Divide the same type of reservoir of the target tight gas horizontal well into i segments equally, and use the drainage radius r of the i segments i as the x-axis, and use the original formation pressure P of the reservoir e as the y-axis to plot the pressure drop funnel distribution map, calculate the energy of the untapped reservoir in the same type of reservoir, and obtain the recovery rate of the i-th segment according to the energy of the untapped reservoir in the same type of reservoir.

4. The method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas according to claim 3, Characterized in that, The calculation formula for the unused reservoir energy of the same type of reservoir is as follows: Wherein, A t represents the unused reservoir energy, a and b represent the constants of the pressure drop and drainage radius relationship formula, and the pressure drop and drainage radius relationship formula is obtained from the pressure drop and drainage radius relationship chart curves of different types of reservoirs of the target tight gas horizontal well.

5. The method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas according to claim 4, Characterized in that, Obtaining the recovery rate of the i-th section according to the unused reservoir energy of the same type of reservoir, the formula is as follows: E R represents the recovery rate of the i-th stage; P e Indicates the original formation pressure of the reservoir.

6. The method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas according to claim 1, Characterized in that, Step 300 for calculating the gas production corresponding to the recovery rate, the calculation formula is as follows: Q i represents the gas production of the i-th stage; G i Indicates the gas storage volume of the i-th section.

7. The method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas according to claim 6, Characterized in that, Gas storage capacity Gi of the i-th section i The calculation formula is as follows: denotes the porosity; S g denotes the gas saturation; V r represents the discharge volume.

8. The method for determining interval distance of horizontal well reconstruction section based on drainage range of tight gas according to claim 6 or 7, Characterized in that, Combined with the transformation cost in step 400, evaluate the reasonable section spacing by section, including: obtaining the transformation cost Pi of the ith section of different types of reservoirs of the tight gas horizontal well i改造 , if P i改造 ≤Q i ×P g单价 , then the reasonable section spacing R 合理 = 2r i , where P g单价 represents the unit price of natural gas.

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