Method for calculating flowback rate of each layer of two-layer combined test oil and gas well

Abstract

The invention belongs to the technical field of oil and gas testing in the petroleum and natural gas industry, and particularly relates to a method for calculating the flowback rate of each layer of a two-layer combined testing oil and gas well. According to the method, a stratum water sample is obtained before fracturing, fracturing fluid A and fracturing fluid B are adopted in an upper layer and a lower layer respectively, the average chlorine content # imgabs0 #, # imgabs1 # and # imgabs2 # of the stratum water sample, the fracturing fluid A and the fracturing fluid B are tested and obtained, the fracturing fluid dosage # imgabs3 # and # imgabs4 # of each layer during pressure division of the two layers are recorded, the flow-back fluid amount # imgabs5 # in n days of flow-back in the flow-back stage is recorded, the chlorine content # imgabs6 # is tested, n is equal to 1, 2 and 3, and the fracturing fluid dosage # imgabs3 # and the fracturing fluid dosage # imgabs4 # are calculated. ..., calculating two layers of flow-back fluid amounts # imgabs7 # and # imgabs8 # in flow-back fluid every day, calculating flow-back rates eta A and eta B of the upper layer and the lower layer and the total flow-back rate eta when flow-back is carried out to the nth day, stopping calculation until the nth day meets a calculation termination condition, taking the eta A and the eta B as the final flow-back rates of the upper layer and the lower layer of test oil and gas, and taking the final flow-back rates as energy and filtration characteristic evaluation parameters of related reservoirs. And a basis is provided for later-stage modification measure adjustment. According to the method, various additional tracers are avoided, and the fracturing transformation cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas testing in the petroleum and natural gas industry, and particularly relates to a method for calculating the flowback rate of each layer in a two-layer combined testing oil and gas well. Background Art

[0002] At present, for exploration wells and evaluation wells, it is usually started from the deepest oil and gas layer to be evaluated, and a work mode of segmented oil and gas testing and layer-by-layer return is adopted to evaluate the oil and gas content of each layer and provide a basis for the next production construction.

[0003] A basin has two sets of gas-bearing strata, the Upper Paleozoic and the Lower Paleozoic. The exploitable strata of the Upper Paleozoic are mainly He 8 and Shan 1, while the exploitable strata of the Lower Paleozoic are the upper combination of Majiagou. The distance between the upper and lower strata is relatively close, which provides the conditions for mechanical stratified fracturing. In order to improve the evaluation and production efficiency and reduce the transformation cost, the upper and lower strata are often combined to obtain the test gas production.

[0004] At present, the most widely used method for testing the flowback rate of each stage of fracturing is tracer monitoring technology. By using different types of tracers in each stage of fracturing, and testing various tracer concentrations in the flowback stage, the flowback rate of each stage of fracturing fluid can be determined. However, this method often requires the use of multiple types of tracers, and tracers need to be added during the entire fracturing process. They are generally deployed in key monitoring wells, which adds additional costs to conventional test oil and gas wells, and lacks a calculation method for the flowback rate of each layer of test oil and gas production. Summary of the invention

[0005] The present invention provides a method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well. The purpose is to provide a method for calculating the flowback rate of fracturing fluid in each layer for a large number of upper and lower strata combined test oil and gas. The method is mainly suitable for two sets of Paleozoic strata or two sets of strata with large differences in pressure separation and calculation, and the flowback rate of each layer is calculated, so as to evaluate the fracturing effect of each layer and provide a basis for adjusting the parameters of the measures in the later stage.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A method for calculating the flowback rate of each layer of a two-layer combined test oil and gas well comprises the following steps: Step 1: Obtain formation water samples before fracturing; Step 2: The upper and lower layers are respectively treated with fracturing fluid A and fracturing fluid B. The average chloride content of formation water samples, fracturing fluid A and fracturing fluid B is obtained by testing. , and If the difference in chloride content between any two liquids is more than 50%, proceed to step 3; Step 3: Record the amount of fracturing fluid used in each layer when the two layers are divided into two layers , ; Step 4: Record the daily return flow volume during the return flow period and test chloride content , n=1,2,3,…; Step 5: Calculate the volume of two layers of return fluid in the return fluid every day according to step 4 , ; Step 6: Calculate the return rate η of the upper and lower layers on the nth day A、 η B and the overall flowback rate η; Step 7: Until the nth day, the calculation termination condition is met, then stop the calculation, then η A and η B Test the final oil and gas flowback rate for the upper and lower layers; Step 8: The final return flow rate of the upper and lower test oil and gas layers obtained in step 6 is used as the formation energy of the relevant reservoir, and the filtration loss situation is evaluated to provide a basis for subsequent adjustment and transformation measures.

[0007] The amount of fracturing fluid used in each stage of step 3 refers to the amount of fluid entering the formation during each stage of fracturing, including pre-fluid, sand-carrying fluid and displacement fluid. The displacement fluid must be deducted from the portion retained in the wellbore.

[0008] The backflow stage in step 4, the backflow day n, refers to the number of days from the start of the blowdown; the backflow liquid volume The chloride content of the return fluid is the sum of the return fluid volume on that day. The chloride content of the return fluid is measured at least 5 times a day, and the average value is taken as the chloride content of the return fluid on that day. ; in, The unit is m 3 ; The unit is mg / L.

[0009] The amount of two layers of return fluid in the return fluid per day in step 5 is calculated , ; Use the following method, Combine the daily return flow volume and chloride content to form the following equation: Calculate the daily return fluid , The actual value of Including: Daily return fluid volume and average chloride , which is a mixture of two fracturing fluids A and B, where the actual amount of A and B is marked as , , unit: m 3 .

[0010] The return rate η of the upper and lower layers in step 6 A、 η B Calculate using the following formula ; Where: η A , η B , η are the individual and total flowback rates of the two layers of liquid respectively; unit: dimensionless.

[0011] The overall return rate in step 6 is calculated using the following formula: .

[0012] There are two calculation termination conditions in step 7; one is the chloride content ( - ) / Less than or equal to the preset value; secondly, the daily return fluid is difficult to measure.

[0013] The - ) / The default value is 0.2.

[0014] In step eight, the fluid loss situation is evaluated by adopting a graded evaluation method, and a fluid loss degree classification standard is given according to the formation energy level and the backflow situation, which is as follows: Obtain the formation pressure coefficient. When the formation pressure coefficient is 0.8-1.0, if the flowback rate is less than 30%, the filtration loss level is severe; if the flowback rate is between 30-50%, the filtration loss level is moderate; if the flowback rate is greater than 50%, the filtration loss level is normal; when the formation pressure coefficient is 1.0-1.2, if the flowback rate is less than 40%, the filtration loss level is severe; if the flowback rate is between 40-60%, the filtration loss level is moderate; if the flowback rate is greater than 60%, the filtration loss level is normal.

[0015] Beneficial effects: ① The present invention aims at two sets of reservoirs with greatly different properties, utilizes the difference in transformation technology and liquid properties, establishes a group of equations based on chloride ion content, and determines a method for simply calculating the return rate of each layer of the test oil and gas well by partial pressure.

[0016] ② The present invention avoids the use of various additional tracers and can be applied in a large number of evaluation and production wells, thereby reducing the cost of fracturing transformation.

[0017] ③ The present invention is a simple analysis of the post-compression flowback rate, which can evaluate the subsequent formation energy, reservoir fracture characteristics, etc., and verify it with static data to provide a basis for subsequent production construction.

[0018] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a flow chart of the present invention.

[0021] Figure 2 This is a graph showing the change in the return rate of Mawu 2 in a specific implementation manner of the present invention.

[0022] Figure 3 It is a graph showing the change of the return rate of Ma Wu 4 in a specific implementation manner of the present invention.

[0023] Figure 4 It is a graph showing the change in the total return flow rate and the return flow proportion of each section in a specific implementation manner of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1: according to Figure 1 A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well is shown, comprising the following steps: Step 1: Obtain formation water samples before fracturing; Step 2: The upper and lower layers are respectively treated with fracturing fluid A and fracturing fluid B. Calculate the average chloride content of formation water samples, fracturing fluid A and fracturing fluid B , and If the difference in chloride content between any two liquids is more than 50%, proceed to step 3; Step 3: Record the amount of fracturing fluid used in each layer when the two layers are divided into two layers , ; Step 4: Record the daily return flow volume during the return flow period and test chloride content , n=1,2,3,…; Step 5: Calculate the volume of two layers of return fluid in the return fluid every day according to step 4 , ; Step 6: Calculate the return rate η of the upper and lower layers on the nth day A、 η B and the overall flowback rate η; Step 7: Until the nth day, the calculation termination condition is met, then stop the calculation, then η A and η B Test the final oil and gas flowback rate for the upper and lower layers; Step 8: The final return flow rate of the upper and lower test oil and gas layers obtained in step 6 is used as the formation energy of the relevant reservoir, and the filtration loss situation is evaluated to provide a basis for subsequent adjustment and transformation measures.

[0026] In specific applications, formation water samples, upper and lower fracturing fluids A and B, average chloride content of the liquid , and There must be a significant difference, and the difference in chloride content between any two liquids is more than 50%. For example, the upper and lower fracturing fluids are conventional fracturing fluid and acid respectively. The chloride content values ​​of conventional fracturing fluid, acid, and formation water are quite different, meeting the requirement that the difference in chloride content between any two liquids is more than 50%.

[0027] The amount of fracturing fluid used in each stage of step 3 refers to the amount of fluid entering the formation during each stage of fracturing, generally including pre-fluid, sand-carrying fluid and displacement fluid, and the displacement fluid must be deducted from the portion retained in the wellbore.

[0028] The backflow stage in step 4, the backflow day n, refers to the number of days from the start of the blowdown; the backflow liquid volume The chloride content of the return fluid is the sum of the return fluid volume on that day. The chloride content of the return fluid is measured at least 5 times a day, and the average value is taken as the chloride content of the return fluid on that day. ; in, The unit is m 3 ; The unit is mg / L.

[0029] The amount of two layers of return fluid in the return fluid per day in step 5 is calculated , ; Use the following method, Combine the daily return flow volume and chloride content to form the following equation: Calculate the daily return fluid , The actual value of Including: Daily return fluid volume and average chloride , which is a mixture of two fracturing fluids A and B, where the actual amount of A and B is marked as , , unit: m 3 .

[0030] The return rate η of the upper and lower layers in step 6 A、 η B Calculate using the following formula ; Where: η A , η B , η are the individual and total flowback rates of the two layers of liquid respectively; unit: dimensionless.

[0031] The overall return rate in step 6 is calculated using the following formula: .

[0032] There are two calculation termination conditions in step 7; one is the chloride content ( - ) / Less than or equal to the preset value means that the chloride content of the return fluid is close to that of the original formation water, and the return rate should be a higher value at this time; secondly, on the nth day, the return fluid is very little and difficult to measure, which means that after various drainage aids such as natural blowing, gas lift, and suction, the return fluid is still very little. When there are no more effective drainage aids in the future, the return is deemed to be over.

[0033] The - ) / The default value is 0.2.

[0034] In step eight, the filtration loss situation is evaluated by adopting a graded evaluation method, and a filtration loss degree classification standard is given according to the formation energy level and the backflow situation, as shown in the table below.

[0035] Aiming at two sets of reservoirs with greatly different properties, the present invention utilizes the difference in transformation technology and liquid properties, establishes an equation group based on chloride ion content, and determines a method for simply calculating the return rate of each layer of the test oil and gas well by partial pressure.

[0036] The present invention avoids the use of various additional tracers, can be applied in a large number of evaluation and production wells, and reduces the cost of fracturing transformation.

[0037] The present invention is a simple analysis of the post-compression flowback rate, which can evaluate the subsequent formation energy, reservoir fracture characteristics, etc., and verify with static data to provide a basis for subsequent production construction.

[0038] Embodiment 2: The present invention is applied to a well to be evaluated.

[0039] Well R4 is an appraisal well with a depth of 3257.00m. The drilling layer is the Ma3rd section of the Majiagou Formation of the Ordovician System of the Lower Paleozoic. The logging data of the Ma54+Ma52 sub-sections of the well are interpreted as gas layers and gas-bearing layers. In order to evaluate the gas reservoir resources of the Ma54 layer and explore the gas-bearing properties of the Ma52 sub-layer, combined pressure testing was carried out on the two layers. The Ma54 and Ma52 sub-sections were designed to use guar gum plus sand fracturing and quick-dissolving thickening acid fracturing respectively.

[0040] 330m of guar fracturing fluid injected into the ground at the 4th section of Mawu, R4 well 3 , Mawu 2nd stage quick-dissolving thickening acid into the ground liquid volume 200m 3 According to the previous test analysis, the chloride contents of formation water, guar fracturing fluid, and instant thickening acid are 2000mg / L, 500mg / L, and 200000mg / L, respectively, satisfying that the difference between any two exceeds 50%.

[0041] The statistical flowback data of R402 well is shown in Table 1. Taking the data on December 19 as an example, there is the following equation: Obtain =31.4, =3.5, from which we can know that the return flow volume of Mawu 4 section on December 19 was 3.5m 3 The flowback volume of Mawu 2 is 31.4m 3 .

[0042] Continue to calculate the return flow data of each stage, and obtain the return flow rate data of Mawu 4 and Mawu 2 as follows Figure 2-Figure 4 As shown. The formation pressure coefficient of this block is about 0.82. Figure 2-Figure 4 It is obvious that during the two-layer combined pressure process, the filtration loss of Mawu 4 is large and the flowback rate is low; the filtration loss level is severe, which is consistent with the reservoir characteristics of the layer with developed dissolved pores, dissolved fractures, and layered dolomite. Mawu 2 has almost no filtration loss and a high flowback rate, which is also consistent with the characteristics of the block dolomite, dense reservoir, and no developed dissolved pores. When similar reservoirs are developed in the future, targeted transformation plans can be adjusted.

[0043] Table 1 R402 flowback data In the absence of conflicts, technicians in this field can combine the relevant technical features in the above examples according to actual conditions to achieve corresponding technical effects. The specific combinations are not described here one by one.

[0044] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0045] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0046] The above are only preferred embodiments of the present invention. The present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein. Any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well, characterized by: The following steps are included: Step 1: Obtain formation water samples before fracturing; Step 2: The upper and lower layers are respectively treated with fracturing fluid A and fracturing fluid B. The average chloride content of formation water samples, fracturing fluid A and fracturing fluid B is obtained by testing. , and If the difference in chloride content between any two liquids is more than 50%, proceed to step 3; Step 3: Record the amount of fracturing fluid used in each layer when the two layers are divided into two layers , ; Step 4: Record the daily return flow volume during the return flow period and test chloride content , n=1,2,3,…; Step 5: Calculate the volume of two layers of return fluid in the return fluid every day according to step 4 , ; Step 6: Calculate the return rate η of the upper and lower layers on the nth day A、 η B and the overall flowback rate η; Step 7: Until the nth day, the calculation termination condition is met, then stop the calculation, then η A and η B Test the final oil and gas flowback rate for the upper and lower layers; Step 8: The final return flow rate of the upper and lower test oil and gas layers obtained in step 6 is used as the formation energy of the relevant reservoir, and the filtration loss situation is evaluated to provide a basis for subsequent adjustment and transformation measures.

2. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 1, characterized in that: The amount of fracturing fluid used in each stage of step 3 refers to the amount of fluid entering the formation during each stage of fracturing, including pre-fluid, sand-carrying fluid and displacement fluid. The displacement fluid must be deducted from the portion retained in the wellbore.

3. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 1, characterized in that: The backflow stage in step 4, the backflow day n, refers to the number of days from the start of the blowdown; the backflow liquid volume The chloride content of the return fluid is the sum of the return fluid volume on that day. The chloride content of the return fluid is measured at least 5 times a day, and the average value is taken as the chloride content of the return fluid on that day. ; in, The unit is m 3 ; The unit is mg / L.

4. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 1, characterized in that: The amount of two layers of return fluid in the return fluid per day in step 5 is calculated , ; Use the following method, Combine the daily return flow volume and chloride content to form the following equation: Calculate the daily return fluid , The actual value of Including: Daily return fluid volume and average chloride , which is a mixture of two fracturing fluids A and B, where the actual amount of A and B is marked as , , unit: m 3 .

5. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 1, characterized in that: The return rate η of the upper and lower layers in step 6 A、 η B Calculate using the following formula ； Where: η A , η B , η are the return rates of the two layers of liquid respectively and the total; unit: dimensionless.

6. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 1, characterized in that: The overall return rate in step 6 is calculated using the following formula: 。 7. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 1, characterized in that: There are two calculation termination conditions in step 7; one is the chloride content ( - ) / Less than or equal to the preset value; secondly, the daily return fluid is difficult to measure.

8. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 7, characterized in that: The - ) / The default value is 0.

2.

9. A method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well as claimed in claim 1, characterized in that: In step eight, the fluid loss situation is evaluated by adopting a graded evaluation method, and a fluid loss degree classification standard is given according to the formation energy level and the backflow situation, which is as follows: Obtain the formation pressure coefficient. When the formation pressure coefficient is 0.8-1.0, if the flowback rate is less than 30%, the filtration loss level is severe; if the flowback rate is between 30-50%, the filtration loss level is moderate; if the flowback rate is greater than 50%, the filtration loss level is normal; when the formation pressure coefficient is 1.0-1.2, if the flowback rate is less than 40%, the filtration loss level is severe; if the flowback rate is between 40-60%, the filtration loss level is moderate; if the flowback rate is greater than 60%, the filtration loss level is normal.

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