A method for calculating the flowback rate of each layer of a two-layer combined oil and gas well

Abstract

The present invention belongs to the field of oil and gas testing technology in the petroleum and natural gas industry, and specifically relates to a method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well. The present invention obtains a formation water sample before fracturing, uses fracturing fluid A and fracturing fluid B in the upper and lower layers respectively, tests and obtains the average chloride content of the formation water sample, fracturing fluid A and fracturing fluid B, records the sum of the fracturing fluid usage of each layer when the two layers are partially pressured, records the flowback fluid volume and the test chloride content every day during the flowback period of n days, where n = 1, 2, 3, ..., calculates the sum of the flowback fluid volume of the two layers in the flowback fluid every day, and calculates the flowback rate η of the upper and lower layers when the flowback reaches the nth day. A ,η B and the overall return rate η, and the calculation stops when the calculation termination condition is met on the nth day, at which time η A and η B The final flowback rate of the oil and gas tested in the upper and lower layers is used as a parameter for evaluating the energy and filtration characteristics of the relevant reservoir, providing a basis for adjusting and reforming measures in the future. This invention avoids the use of various additional tracers and reduces the cost of fracturing reformation.

Description

TECHNICAL FIELD

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

[0002] At present, for exploratory wells and evaluation wells, the working mode of step-by-step oil and gas testing is usually adopted from the deepest layer to be evaluated, and the oil and gas content of each layer is evaluated to provide a basis for the next step of production.

[0003] In a certain basin, two sets of gas-bearing layer systems of the Upper Paleozoic and the Lower Paleozoic are developed, wherein the main exploitation layer of the Upper Paleozoic is He 8 and Shan 1, and the main exploitation layer of the Lower Paleozoic is the upper Majiagou combination. The distance between the upper and lower layers is relatively close, and the mechanical layering and fracturing conditions are met. In order to improve the evaluation and production efficiency and reduce the transformation cost, the two sets of layer systems are often divided and fractured to obtain the gas production.

[0004] At present, the most widely used method for testing the fracturing flowback rate of each layer is tracer monitoring technology. Different types of tracers are used during fracturing of each layer, and the concentrations of various tracers are tested during the flowback stage to determine the fracturing fluid flowback rate of each layer. However, this method often requires the use of multiple types of tracers, and the tracers need to be added during the entire fracturing process, usually deployed in key monitoring wells. For conventional oil and gas testing wells, additional costs are added, and there is a lack of calculation method for the flowback rate of each layer of the divided and combined testing of oil and gas production. SUMMARY

[0005] The application provides a method for calculating the flowback rate of each layer of a two-layer combined oil and gas well, which aims to provide a calculation method for calculating the fracturing fluid flowback rate of each layer for a large number of two-layer combined oil and gas testing, mainly applicable to the divided and combined calculation of two sets of Paleozoic layer systems or two sets of layer systems with large differences, and the flowback rate of each layer is calculated to evaluate the fracturing effect of each layer and provide a basis for adjusting the parameter of the later stage.

[0006] To achieve the above purpose, the technical scheme adopted by the application is:

[0007] A method for calculating the flowback rate of each layer of a two-layer combined oil and gas well, comprising the following steps,

[0008] Step 1: Obtain the formation water sample before fracturing;

[0009] Step 2: The upper and lower layers respectively use fracturing fluid A and fracturing fluid B, and the average chloride content of the formation water sample, fracturing fluid A and fracturing fluid B is obtained by testing , and If the difference value of the chloride content of any two liquids is more than 50%, go to step 3;

[0010] Step three: record the amount of fracturing fluid used in each layer when the two layers are divided , ;

[0011] Step four: record the amount of flowback fluid in each day during the flowback stage and test the chlorine content , n = 1, 2, 3, …;

[0012] Step five: calculate the amount of flowback fluid in each layer in each day according to step four , ;

[0013] Step six: calculate the flowback rate η of the upper and lower layers on the nth day A、 η B and the overall flowback rate η;

[0014] Step seven: until the nth day, meet the calculation termination condition, then stop calculation, then η A and η B are the final flowback rates of oil and gas testing in the upper and lower layers;

[0015] Step eight: use the final flowback rates of oil and gas testing in the upper and lower layers obtained in step six as the relevant reservoir formation energy and filtration loss condition to evaluate and provide basis for later adjustment and modification measures.

[0016] The amount of fracturing fluid in each section in step three refers to the amount of fluid entering the formation during fracturing in each section, including preflush, sand-carrying fluid and displacement fluid. The displacement fluid part must deduct the part remaining in the wellbore.

[0017] The nth day of flowback stage in step four refers to the number of days from the start of blowout; the flowback fluid amount is the sum of the flowback fluid amount on that day, and the average value of chlorine content in the flowback fluid is measured at least 5 times a day ;

[0018] Wherein, the unit is m 3 ; The unit of η is mg / L.

[0019] The amount of flowback fluid in each layer in each day in step five , ; the following method is used,

[0020] The amount of flowback fluid and chlorine content in each day are associated with the equation:

[0021]

[0022]

[0023] Calculate the daily flowback , The actual value of

[0024] Including: Daily return fluid volume and average chloride , is a mixture of two fracturing fluids A and B, where the actual amount of A and B flowback fluids is marked as , , unit: m 3 .

[0025] The return rate η of the upper and lower layers in step 6 A、 η B Calculate using the following formula

[0026]

[0027] ;

[0028] Where: η A ,η B and η are the individual and total flowback rates of the two layers of liquid, respectively; unit: dimensionless.

[0029] The overall flowback rate in step 6 is calculated using the following formula:

[0030] .

[0031] There are two termination conditions for the calculation in step 7; one is the chloride content ( - ) / Less than or equal to the preset value; secondly, it is difficult to measure the return fluid every day.

[0032] The ( - ) / The default value is 0.2.

[0033] In step eight, the fluid loss situation is assessed by adopting a graded assessment method, and a fluid loss degree classification standard is given according to the formation energy level and the backflow situation, as follows:

[0034] 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.

[0035] Beneficial effects:

[0036] ①The present application is directed to two sets of reservoirs with large property differences, and a simple calculation method for determining the backflow rate of each layer of the oil and gas well is established by using the property difference between the reconstruction process and the liquid, and establishing an equation group based on the chloride ion content.

[0037] ②The present application avoids the use of various additional tracers, and can be applied in a large number of evaluation and well construction wells, thereby reducing the cost of fracturing reconstruction.

[0038] ③The present application is a simple analysis of the backflow rate after fracturing, which can evaluate the subsequent formation energy, reservoir fracture characteristics and the like, and is verified by static data, thereby providing a basis for subsequent well construction.

[0039] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, and can be implemented according to the content of the specification, as follows. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments or prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0041] Figure 1 The flowchart of the present application.

[0042] Figure 2 The backflow rate change graph of Ma five 2 in the specific embodiment of the present application.

[0043] Figure 3 The backflow rate change graph of Ma five 4 in the specific embodiment of the present application.

[0044] Figure 4 The total backflow rate and the backflow rate of each section in the specific embodiment of the present application. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0046] Example one:

[0047] According to Figure 1The method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well shown in FIG. includes the following steps:

[0048] Step 1: Obtain formation water samples before fracturing;

[0049] Step 2: The upper and lower layers are respectively treated with fracturing fluid A and fracturing fluid B. Calculate the average chloride content of the formation water sample, fracturing fluid A and fracturing fluid B. , and If the difference in chloride content between any two liquids is greater than 50%, proceed to step 3.

[0050] Step 3: Record the amount of fracturing fluid used in each layer when the two layers are partially pressurized , ;

[0051] Step 4: Record the daily flowback volume during the flowback period and test chloride content , n=1, 2, 3, ...;

[0052] Step 5: Calculate the volume of two layers of flowback fluid in the daily flowback fluid according to step 4 , ;

[0053] 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;

[0054] Step 7: Until the nth day, the calculation termination condition is met, then stop the calculation, then η A and η B The final oil and gas flowback rate for the upper and lower layers;

[0055] Step 8: Use the final return flow rate of the upper and lower test layers obtained in step 6 as the formation energy of the relevant reservoir and the filtration loss situation to evaluate and provide a basis for subsequent adjustment and transformation measures.

[0056] In specific applications, formation water samples, upper and lower fracturing fluids A and B, and average chloride content of the liquid , and There must be a significant difference, with the chloride content difference between any two fluids exceeding 50%. For example, the upper and lower fracturing fluids are conventional fracturing fluid and acid, respectively. The chloride content of conventional fracturing fluid, acid, and formation water varies significantly, meeting the requirement that the chloride content difference between any two fluids must be at least 50%.

[0057] The amount of fracturing fluid in each section in step three refers to the amount of fluid entering the formation during fracturing in each section, which generally includes preflush, sand-carrying fluid and displacement fluid. The displacement fluid part must deduct the part remaining in the wellbore.

[0058] The nth day of flowback in step four refers to the number of days from the start of flowback; the flowback fluid volume is the sum of the flowback fluid volume of each day. The chloride value of flowback fluid is measured at least 5 times a day, and the average value is taken as the chloride content of flowback fluid of that day ;

[0059] Wherein, The unit is m 3 ; The unit is mg / L.

[0060] In step five, the amount of flowback fluid of each layer in each day is calculated 、 ; the following method is used,

[0061] The flowback fluid volume and chloride content of each day are combined with the equation:

[0062]

[0063]

[0064] The actual value of the amount of flowback fluid of each layer in each day is calculated , ;

[0065] Wherein, the flowback fluid volume of each day and the average chloride content of each layer are the mixed products of A and B fracturing fluids, wherein the actual amount of A and B flowback fluids is marked as , , unit: m 3 .

[0066] In step six, the flowback rate η A、 η B of the upper and lower layers is calculated using the following formula

[0067]

[0068] ;

[0069] Wherein: η A , η B , η are the flowback rates of each layer and the total respectively; unit: dimensionless.

[0070] The overall flowback rate in step six is calculated using the following formula

[0071] .

[0072] The step seven calculates the termination condition, which has two; one is the chloride content (Cl-) - ) / The preset value is 0.2.

[0073] The preset value is 0.2. - The preset value is 0.2. The preset value is 0.2.

[0074] The step eight evaluates the filtration loss, adopts a grading evaluation method, and gives a filtration loss grading standard according to the formation energy level and flowback condition, and the specific table is shown below.

[0075]

[0076] The present application is aimed at two sets of reservoirs with large property difference, uses the property difference of the reconstruction process and liquid, establishes an equation group based on chloride content, and determines a simple calculation method for calculating the flowback rate of each layer of the oil and gas test well.

[0077] The present application avoids using various additional tracers, can be applied in a large number of evaluation production wells, and reduces the reconstruction cost.

[0078] The present application is a simple analysis of the post-fracturing flowback rate, can evaluate the subsequent formation energy, reservoir fracture characteristics and the like, and is verified with static data, thereby providing a basis for subsequent production.

[0079] Example two:

[0080] The application of the present application in the well to be evaluated.

[0081] R4 well is an evaluation well with a well depth of 3257.00 m, and the drilled layer position is the Ordovician Majiagou Formation Ma 3 section of the lower Paleozoic. The logging data of the Ma 5 4+Ma 5 2 sub-section is interpreted as a gas layer and a gas-bearing layer. In order to evaluate the Ma 5 4 gas reservoir and explore the gas-bearing property of the Ma 5 2 sub-layer, the two layers are subjected to combined pressure test. The Ma 5 4 and Ma 5 2 sub-sections are respectively designed to adopt guanidium gel plus sand fracturing and quick-dissolving thickened acid acidizing.

[0082] The gu gel fracturing fluid of the Ma 5 4 section of the R4 well enters the ground liquid of 330 m 3 , and the quick-dissolving thickened acid of the Ma 5 2 section enters the ground liquid of 200 m 3According to preliminary test analysis, the chloride contents of formation water, guar gum fracturing fluid, and instant thickening acid are 2000 mg / L, 500 mg / L, and 200,000 mg / L, respectively, and the difference between any two of them exceeds 50%.

[0083] The flowback data of well R402 is shown in Table 1. Taking the data of December 19 as an example, the following equation is used:

[0084]

[0085]

[0086] Obtain =31.4, =3.5, so we can know that the flowback volume of Mawu 4 section on December 19 was 3.5m 3 The flowback volume of Mawu 2 section is 31.4m 3 .

[0087] Continue to calculate the flowback data of each stage and obtain the flowback rate data of Mawu 4 and Mawu 2 as follows Figures 2-4 As shown. The formation pressure coefficient of this block is about 0.82. Figures 2-4 It is clearly seen that during the combined compression of the two layers, Ma54 exhibited significant fluid loss and a low flowback rate; the fluid loss level was classified as severe, consistent with the reservoir characteristics of layered dolostones with developed dissolution pores and dissolution fractures. Ma52 exhibited almost no fluid loss and a high flowback rate, also consistent with the reservoir characteristics of massive dolostones, a tight reservoir, and a lack of dissolution pores. Targeted modification plans could be implemented for subsequent development of similar reservoirs.

[0088] Table 1 R402 flowback data

[0089]

[0090] In the absence of conflicts, those skilled in the art may combine the relevant technical features in the above examples according to actual circumstances to achieve corresponding technical effects. Specific descriptions of various combinations are omitted here.

[0091] 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 various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0092] In addition, the terms "first", "second", and the like, as used in the description, are used for distinguishing like from like and do not imply or imply any importance or any relative meaning. Thus, a "first" feature discussed above could be termed a "second" feature without departing from the scope of the present application.

[0093] The above description is merely that of preferred embodiments of the application, and the application is not limited to the details of the foregoing description. Rather, the present application is intended to cover modifications and variations of this application that come within the scope of the appended claims, along with their equivalents.

Claims

1. A method for calculating the flow rate of each layer of a two-layer combined oil and gas well, characterized in that: It comprises the following steps, Step one: obtaining formation water sample before fracturing; Step two: the upper and lower layers respectively use fracturing fluid A and fracturing fluid B, and the average chloride content of the formation water sample, fracturing fluid A and fracturing fluid B is obtained by testing , and If the difference value of chloride content of any two liquids is more than 50%, go to step three; Step three: record the amount of fracturing fluid used in each layer when the two layers are divided , ; Step four: Record the flowback fluid volume in each day of the flowback n days in the flowback stage and test the chloride content n = 1, 2, 3, … Step five: Calculate the amount of two-layer flowback fluid in each day of flowback fluid according to step four , ; Step six: Calculate the flowback rate η of the upper and lower layers at the nth day A、 η B and the overall flowback rate η; Step seven: until the nth day, meet the calculation termination condition, then stop calculation, then η A and η B are the final flowback rates of the upper and lower layers of the oil and gas test Step eight: taking the final flowback rate of the upper and lower layers obtained in step six as the formation energy of the relevant reservoir and evaluating the filtration loss, thereby providing a basis for later adjustment and modification measures.

2. The method of claim 1, wherein the method is a two-layer combined oil and gas well layer flowback rate calculation method, characterized in that: The liquid amount of each section in step three refers to the amount of liquid entering the formation during fracturing of each section, including preflush, sand-carrying fluid and displacement fluid. The displacement fluid part must deduct the part remaining in the wellbore.

3. The method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well according to claim 1, characterized in that: The fourth step refers to the n-th day of the flowback stage, which refers to the number of days from the start of the blowout; the flowback fluid volume The sum of the flowback fluid volume of the day, the chlorine content of the flowback fluid is measured at least 5 times a day, and the average value is taken as the chlorine content of the flowback fluid of the day ; wherein, in m 3 ; in mg / L.

4. The method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well according to claim 1, characterized in that: The step five calculates the two-layer flow rate of the flowback fluid in each day 、 ; the following method is adopted, The daily flowback fluid volume and chloride content are combined with the equation: The actual values of the produced water in each day are calculated , ​ Wherein: the flowback fluid volume per day and the average chloride is a mixture of two kinds of fracturing fluid flowback fluids A and B, wherein the actual volume of the two flowback fluids A and B is marked as , , unit: m 3 .

5. The method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well according to claim 1, characterized in that: The flowback rate η of the upper and lower layers in step six A、 η B The following formula is used to calculate ； where: η A , η B , η are the individual and total flowback rates for each of the two liquids; unit: dimensionless.

6. The method of claim 1, wherein: The total flowback rate in step six is calculated using the following formula 。 7. The method of claim 1, wherein: The two termination conditions calculated in the seventh step are: one is the chlorine content (Cl-) is less than or equal to a preset value; and the other is that the daily flowback fluid is difficult to measure. - ) / less than or equal to a preset value; and the other is that the daily flowback fluid is difficult to measure.

8. The method of claim 7, wherein: The ( - ) / The default value is 0.

2.

9. The method for calculating the flowback rate of each layer in a two-layer combined test oil and gas well according to claim 1, characterized in that: The filtration loss evaluation in step eight adopts a grading evaluation method. The filtration loss degree grading standard is given according to the formation energy level and flowback condition, and is as follows: Obtain the formation pressure coefficient. When the formation pressure coefficient is 0.8-1.0, if the flowback rate is <30%, the filtration loss level is serious; if the flowback rate is 30-50%, the filtration loss level is moderate; and if the flowback rate is >50%, the filtration loss level is normal. When the formation pressure coefficient is 1.0-1.2, if the flowback rate is <40%, the filtration loss level is serious; if the flowback rate is 40-60%, the filtration loss level is moderate; and if the flowback rate is >60%, the filtration loss level is normal.

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