Fracturing fluid string friction calculation method

Abstract

The invention relates to the technical field of oil-gas exploration, in particular to a fracturing fluid string friction calculation method. The method comprises the following steps: carrying out small test fracturing by adopting an alcohol-based fracturing fluid, and obtaining ground construction pressure and post-pressure instantaneous pump stop pressure under each displacement of a stepped displacement reduction test; a comparable well is selected, the ground construction pressure under the highest construction displacement during fracturing, the post-pressing instantaneous pump stopping pressure and the tubular column on-way friction resistance of known fracturing fluid are tested, and the hole friction resistance of the comparable well is calculated; calculating the hole friction resistance of the construction well; calculating the pipe column friction resistance and the pipe column friction resistance coefficient of the alcohol-based fracturing fluid under the construction displacement of the construction well; and establishing a tubular column friction plate of the alcohol-based fracturing fluid under different displacements. According to the method provided by the invention, the friction resistance of the fracturing fluid tubular column can be quickly and accurately calculated, and the accuracy of analyzing parameters such as net pressure in a fracturing crack and ground or bottom hole pressure in a fracturing construction process is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration, in particular to a fracturing fluid pipe string friction calculation method. BACKGROUND

[0002] The rock of the Sazero group in the old area of the Changyuan has strong water sensitivity. The effect of the conventional fracturing fluid is not ideal, and the reservoir reconstruction demand cannot be met. Therefore, field tests of two kinds of fracturing fluid systems, such as anti-swelling guar gum fracturing fluid and alcohol-based fracturing fluid, are carried out. In order to accurately analyze the net pressure in the fracturing fracture, calculate the friction of the fracturing hole of the limited flow method and the opening rate, and predict the ground or bottom hole pressure during the fracturing operation, it is often necessary to determine the pipe string friction of the fracturing fluid. Since the alcohol-based fracturing fluid is first applied in Daqing Oilfield, no downhole electronic pressure gauge is used in the wellbore during fracturing operation, and no indoor fracturing fluid friction tester is used, so the pipe string friction of the alcohol-based fracturing fluid cannot be determined. During the test fracturing analysis, the pipe string friction of the alcohol-based fracturing fluid is often estimated by using the empirical graph of the guar gum fracturing fluid. The ground construction pressure of the alcohol-based fracturing fluid is slightly lower than that of the guar gum fracturing fluid under the same displacement during the field operation, which shows that there is a significant difference in the pipe string friction of the two kinds of fracturing fluid systems. This method cannot meet the construction demand.

[0003] At present, the pipe string friction of the fracturing fluid is generally obtained by the downhole pressure gauge test method, the fracturing fluid friction tester test method, the water reduction resistance ratio experience method, and the friction empirical calculation method. Various test methods have high operation cost and long cycle. The empirical calculation method is affected by the colloid viscosity during the field operation, which leads to a large error between the calculation result and the actual value. SUMMARY

[0004] (I) Technical problem to be solved

[0005] The present application provides a fracturing fluid pipe string friction calculation method to overcome the problem that the pipe string friction parameters of the alcohol-based fracturing fluid are not accurate during the field operation, and the fracturing operation analysis demand cannot be met.

[0006] (II) Technical scheme

[0007] In order to solve the above problems, the present application provides a fracturing fluid pipe string friction calculation method, which comprises:

[0008] Step S1: a small-scale test fracturing is carried out by using the alcohol-based fracturing fluid, and the ground construction pressure and the post-pressure instantaneous pump pressure under each displacement are obtained by using the step-down displacement test;

[0009] Step S2: a comparable well is selected, and the hole friction of the comparable well is calculated according to the ground construction pressure, the post-pressure instantaneous pump pressure under the highest construction displacement during the test fracturing of the comparable well, and the pipe string friction of the known fracturing fluid;

[0010] Step S3: Calculate the hole friction of the construction well according to the hole friction empirical formula;

[0011] Step S4: Calculate the pipe string friction and pipe string friction coefficient of the alcohol-based fracturing fluid of the construction well under the highest construction discharge capacity of the construction well according to the ground construction pressure under the highest construction discharge capacity of the construction well, the instantaneous pump shutdown pressure after pressure, and the hole friction of the construction well;

[0012] Step S5: Establish a pipe string friction chart of the alcohol-based fracturing fluid under different discharge capacities.

[0013] Further, step S1 specifically comprises: testing the ground construction pressure under 3-5 discharge capacities by step-down discharge capacity, and the step-down discharge capacity can be set according to the highest construction discharge capacity. The step-down discharge capacity is generally 0.2-0.5 m 3 / min, and the minimum discharge capacity is not less than 1.0 m 3 / min. The testing time of each discharge capacity is 10-30 s. The ground construction pressure P i and the instantaneous pump shutdown pressure ISIP surf after pressure under each test discharge capacity Q surf are recorded.

[0014] Wherein, Q i : each test discharge capacity, m 3 / min; P surf : the ground construction pressure corresponding to the test discharge capacity, MPa; ISIP surf : the instantaneous pump shutdown pressure after pressure, MPa.

[0015] Further, step S2 specifically comprises: selecting the compared well to be a well with the same block, the same layer, the same lithology, and the same physical property conditions, and the well is adjacent and close. The fracturing construction adopts the same fracturing string and tool, the perforation method and process are the same, and the perforation thickness and the number of perforation holes are consistent. The tested fracturing construction parameters are equivalent to those of the construction well, and the highest discharge capacity and the step-down discharge capacity are the same or similar.

[0016] System friction P f = ground construction pressure P surf - instantaneous pump shutdown pressure ISIP surf after pressure;

[0017] Friction along the way ΔP hf = pipe string friction coefficient ΔP f × pipe string length L;

[0018] Friction of hole seam ΔP entry = hole friction ΔP perf + fracture friction ΔP nwbf

[0019] Therefore, hole friction ΔP perf = ground construction pressure Psurf - Instantaneous shut-in pressure after pumping, ISIP surf - Frictional pressure drop, ΔP hf

[0020] where, P f : system friction, MPa; ΔP hf : frictional pressure drop, MPa; ΔP f : pipe string friction coefficient, MPa / m; L: pipe string length, m; ΔP entry : perforation friction, MPa; ΔP perf : perforation friction, MPa; ΔP nwbf : fracture friction, MPa;

[0021] Since the reservoirs in the Sa zero group have shallow burial depth and weak rock cementation strength, the fracture morphology is single, and the fracture friction is negligible.

[0022] Further, step S3 specifically comprises: according to the perforation friction empirical calculation formula ΔP perf = 2.2326 x 10 -4 Q 2 ρ / n 2 d 4 C 2 It can be seen that, since the highest construction discharge of the comparative well is the same, except for the fracturing fluid density, other parameters can be considered the same, therefore, the perforation friction is positively correlated with the fracturing fluid density;

[0023] It can be obtained that: the perforation friction ΔP perf of the construction well = the perforation friction ΔP perf of the comparative well x ρ 施工井 ÷ ρ 对比井 ;

[0024] where, ρ: fracturing fluid density, kg / cm 3 ; n: number of perforations; d: perforation diameter, mm; C: perforation flow coefficient, indicating the influence of the shape of the perforation inlet on the pressure drop;

[0025] Since the test fracturing perforation flow rate is small, the perforation flow coefficient is the same.

[0026] Further, step S4 specifically comprises: according to the friction calculation formula in step S2, it can be obtained that

[0027] Frictional pressure drop ΔP hf = surface construction pressure P surf - Instantaneous shut-in pressure after pumping, ISIP surf - Perforation friction ΔP perf

[0028] Pipe string friction coefficient ΔP f = frictional pressure drop ΔP​hf Pipe column length L.

[0029] Further, the step S5 specifically comprises that the method in the steps S3 and S4 respectively calculates the hole friction under different construction discharge capacities, and the alcohol-based fracturing fluid pipe column friction and the pipe column friction coefficient under different discharge capacities are obtained, and the pipe column friction chart of the alcohol-based fracturing fluid under different discharge capacities is established.

[0030] (III) Beneficial effects

[0031] The present application provides a kind of fracturing fluid pipe column friction calculation method, which utilizes the actual data obtained from fracturing construction, quickly and accurately calculates the fracturing fluid pipe column friction, effectively solves the problem that the inaccurate fracturing fluid pipe column friction parameters affect the analysis of fracturing construction during field construction, and improves the accuracy of parameters analysis such as fracturing fracture net pressure, surface or bottom hole pressure during fracturing construction. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the small test fracturing construction curve of well B2 in the embodiment;

[0033] Figure 2 is the fracturing pipe column friction relationship chart of gu gel fracturing fluid system;

[0034] Figure 3 is the pipe column friction relationship chart of alcohol-based fracturing fluid under different discharge capacities;

[0035] Figure 4 is the flow chart of the fracturing fluid pipe column friction calculation method of the embodiment of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the 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 protection scope of the present application.

[0037] As shown in the drawings, Figures 1-4 The present application provides a kind of fracturing fluid pipe column friction calculation method, specifically comprising the following steps:

[0038] Step S1: small test fracturing is carried out by using alcohol-based fracturing fluid, and the surface construction pressure and the instantaneous pump pressure after pressure under each discharge capacity of step-down discharge capacity test are obtained.

[0039] Specifically, it comprises: the surface construction pressure under 3-5 discharge capacities of step-down discharge capacity test, the discharge capacity step can be set according to the highest construction discharge capacity, and the step-down discharge capacity is generally 0.2-0.5 m 3 / min, the minimum displacement is not less than 1.0 m 3 / min, the minimum displacement is not less than 1.0 m i / min, the minimum displacement is not less than 1.0 m surf / min, the minimum displacement is not less than 1.0 m surf / min, the minimum displacement is not less than 1.0 m

[0040] / min, the minimum displacement is not less than 1.0 m i : each test displacement, m 3 / min; P surf : the ground construction pressure corresponding to the test displacement, MPa; ISIP surf : the post-pressure instantaneous pump pressure, MPa.

[0041] Step S2: selecting a comparable well, and calculating the hole friction of the comparable well according to the ground construction pressure under the highest construction displacement during the test fracturing of the comparable well, the post-pressure instantaneous pump pressure, and the known pipe string friction along the way.

[0042] , and the adjacent well is relatively close; the fracturing construction uses the same fracturing pipe string and tool, the perforation method and process are the same, and the perforation thickness and the number of holes are consistent; the test fracturing construction parameters are equivalent to the construction well, the highest displacement and the step-down displacement are the same or similar;

[0043] System friction P f = ground construction pressure P surf - post-pressure instantaneous pump pressure ISIP surf ;

[0044] Friction along the way ΔP hf = pipe string friction coefficient ΔP f × pipe string length L;;

[0045] Friction of hole ΔP entry = hole friction ΔP perf + fracture friction ΔP nwbf

[0046] Therefore, the hole friction ΔP perf = ground construction pressure P surf - post-pressure instantaneous pump pressure ISIP surf - friction along the way ΔP hf ;

[0047] , P f : system friction, MPa; ΔP hf : friction along the way, MPa; ΔP f : pipe string friction coefficient, MPa / m; L: pipe string length, m; ΔP entry: Friction of perforation, MPa; ΔP perf : Friction of perforation, MPa; ΔP nwbf : Friction of fracture, MPa;

[0048] Because the reservoirs of Sa zero group have shallow burial depth, weak rock cementation strength, single fracture morphology and negligible fracture friction.

[0049] Step S3: calculating the friction of perforation of the construction well according to the empirical calculation formula of the friction of perforation.

[0050] Specifically, the step S3 comprises: calculating the friction of perforation of the construction well according to the empirical calculation formula of the friction of perforation. perf = 2.2326 x 10- 4 Q 2 ρ / n 2 d 4 C 2 It can be known that, because the maximum construction discharge of the comparative well is the same, except the fracturing fluid density, other parameters can be considered as the same, therefore, the friction of perforation is positively correlated with the fracturing fluid density.

[0051] It can be obtained that: the friction of perforation of the construction well ΔP perf = the friction of perforation of the comparative well ΔP perf x ρ 施工井 ÷ ρ 对比井 ;

[0052] Wherein, ρ: fracturing fluid density, kg / cm 3 ; n: number of perforation; d: diameter of perforation, mm; C: flow coefficient of perforation, indicating the influence of the shape of perforation entrance on pressure drop.

[0053] Because the liquid passing amount of the test fracturing perforation is small, the flow coefficient of perforation is the same.

[0054] Step S4: calculating the pipe string friction and pipe string friction coefficient of the alcohol-based fracturing fluid of the construction well under the construction discharge according to the ground construction pressure under the maximum construction discharge of the construction well, the instantaneous pump shutdown pressure after fracturing and the friction of perforation of the construction well.

[0055] Specifically, the step S4 comprises: according to the friction calculation formula in the step S2, it can be obtained that

[0056] Friction of pipe string ΔP hf = ground construction pressure P surf - instantaneous pump shutdown pressure ISIP after fracturing surf - friction of perforation ΔP perf

[0057] Pipe string friction coefficient ΔP f = friction of pipe string ΔP hf ÷ pipe string length L.

[0058] Step S5: Establish tubing friction diagrams for alcohol-based fracturing fluids at different displacement rates.

[0059] Specifically, this includes: calculating the orifice friction under different construction flow rates using the methods in steps S3 and S4, obtaining the friction of the alcohol-based fracturing fluid tubing and the tubing friction coefficient under different flow rates, and establishing a tubing friction chart for alcohol-based fracturing fluid under different flow rates.

[0060] The following specific examples illustrate the detailed steps of this fracturing fluid tubing friction calculation method:

[0061] Well B2 is a fracturing test well in the Sa0 Formation of the Daqing Changyuan old area. It uses an alcohol-based fracturing fluid system and a 62mm inner diameter tubing fracturing string. The interpretation interval of the Sa0 Formation No. 7 layer is 987.5-988.6m, with a sandstone thickness of 1.1m and an air permeability of 6.76mD. The perforated interval is 988.0-987.5m, with a perforation thickness of 0.5m and 8 perforations. Well B3 is a comparable well. It uses a guar gum fracturing fluid system and a 62mm inner diameter tubing fracturing string. The interpretation interval of the Sa0 Formation No. 7 layer is 1080.0-1078.7m, with a sandstone thickness of 1.3m and an air permeability of 12.8mD. The perforated interval is 1079.90-1079.4m, with a perforation thickness of 0.5m and 8 perforations.

[0062] Step 1: Small-scale test fracturing was performed on well B2 using alcohol-based fracturing fluid, such as... Figure 1 As shown, the maximum construction discharge is 4m³. 3 / min, emission reduction 3.5m 3 / min, 3.0m 3 / min, 2.5m 3 / min, 2.0m 3 / min, corresponding to ground construction pressures of 34.5MPa, 28.6MPa, 23.7MPa, 20.0MPa, and 17.1MPa, respectively, with an instantaneous pump stop pressure of 10.8MPa after pressure.

[0063] Step 2: A small-scale test fracturing operation can be conducted on well B3 using emulsified guar gum fracturing fluid, with a maximum flow rate of 4m³. 3 / min, ground construction pressure 35.8MPa, instantaneous pump stop pressure after pumping 10.46MPa, refer to the known friction chart of guar gum fracturing fluid tubing, such as Figure 2 As shown, the calculated perforation friction of the comparable well is 15.6 MPa;

[0064] Step 3: Calculate P based on the empirical formula for hole friction resistance. pf =2.2326×10 -4 Q 2 ρ / n 2 d 4 C2 Since the construction parameters of the comparison wells were the same, all parameters except for the fracturing fluid density can be considered identical. Therefore, porosity friction is positively correlated with fracturing fluid density. The density of alcohol-based fracturing fluid is 1.12 g / cm³. 2 The density of the emulsified guar gum fracturing fluid is 1.05 g / cm³. 2 The borehole friction of the construction well was calculated to be 16.6 MPa.

[0065] Step 4: Based on the surface operating pressure of 34.5 MPa, the instantaneous pump stop pressure after pumping of 10.8 MPa, and the orifice friction of 16.6 MPa under the maximum operating flow rate of the operating well, calculate the tubing friction of the alcohol-based fracturing fluid under this operating flow rate as 7.1 MPa, and the tubing friction coefficient as 7.2 MPa / 1000 m;

[0066] Step 5: Corresponding to the emission reduction stage 3.5m 3 / min, 3.0m 3 / min, 2.5m 3 / min, 2.0m 3 The perforation friction of the alcohol-based fracturing fluid was determined to be 12.7 MPa, 9.3 MPa, 6.5 MPa, and 4.2 MPa at different discharge rates. Based on the surface operating pressure, the instantaneous pump stop pressure after pumping, and the perforation friction of the corresponding single-hole discharge rate at each discharge rate, the tubing friction and tubing friction coefficient of the alcohol-based fracturing fluid at different discharge rates were calculated, and a tubing friction chart for alcohol-based fracturing fluid at different discharge rates was established, as shown below. Figure 3 As shown, this provides a basis for the analysis of alcohol-based hydraulic fracturing operations.

[0067] The fracturing fluid tubing friction calculation method provided by this invention overcomes the shortcomings of various fracturing fluid friction testing methods, such as high operating costs and long cycles, and the large errors between the calculation results and actual values ​​of empirical calculation methods. This method utilizes actual data obtained during fracturing operations to quickly and accurately calculate the fracturing fluid tubing friction, effectively solving the problem of inaccurate fracturing fluid tubing friction parameters affecting fracturing operation analysis during field operations. It also improves the accuracy of analyzing parameters such as net pressure within the fracturing cavity and surface or bottomhole pressure during fracturing operations.

[0068] The above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A method of calculating the friction of a fracturing fluid pipe string, characterized in that, The method comprises the following steps: Step S1: small-scale test fracturing is carried out by using alcohol-based fracturing fluid, and ground construction pressure and instantaneous pump stop pressure after pressure under each displacement in the step-down displacement test are obtained; Step S2: a comparable well is selected, and the hole friction of the comparable well is calculated according to the ground construction pressure under the highest construction displacement in the test fracturing, the instantaneous pump stop pressure after pressure and the known pipe string friction resistance of the fracturing fluid; Step S3: the hole friction of the construction well is calculated according to the empirical calculation formula of the hole friction; Step S4: the pipe string friction resistance and the pipe string friction resistance coefficient of the alcohol-based fracturing fluid under the construction displacement of the construction well are calculated according to the ground construction pressure under the highest construction displacement, the instantaneous pump stop pressure after pressure and the hole friction of the construction well; Step S5: a pipe string friction resistance chart of the alcohol-based fracturing fluid under different displacements is established.

2. The method of calculating the friction of a fracturing fluid pipe string of claim 1, wherein, Step S1 specifically comprises: testing the ground construction pressure at 3-5 displacement steps, the displacement steps can be set according to the highest construction displacement, the displacement step is 0.2-0.5 m 3 / min, the minimum displacement is not less than 1.0 m 3 / min, the test time of each displacement is 10-30 s; the ground construction pressure P i and the instantaneous shut-in pressure ISIP surf after pressure at each test displacement Q surf are recorded. where Q i : individual test rate, m 3 / min; P surf : surface treating pressure corresponding to the test rate, MPa; ISIP surf : post-frac instantaneous shut-in pressure, MPa.

3. The method of calculating the friction of a fracturing fluid pipe string of claim 1, wherein, Step S2 specifically comprises: the comparable well is selected from the wells in the same block, the same layer, similar lithology and physical property conditions and the wells close to the well; the fracturing construction adopts the same fracturing pipe string and tool, the perforation mode and process are the same, and the perforation thickness and the number of perforation holes are consistent; the construction parameters of the test fracturing are equivalent to those of the construction well, the highest displacement and the step-down displacement are the same or similar; System Friction P f = Surface Construction Pressure P surf - Instantaneous Shut-in Pressure after Pressure ISIP surf ; frictional pressure drop ΔP hf = column friction coefficient ΔP f x column length L; hole friction ΔP entry = orifice friction ΔP perf + slot friction ΔP nwbf ; Thus, hole friction ΔP perf = surface construction pressure P surf - instantaneous shut-in pressure after pressure ISIP surf - frictional pressure drop ΔP hf ; where P f : system friction, MPa; ΔP hf : friction along the path, MPa; ΔP f : pipe column friction coefficient, MPa / m; L: pipe column length, m; ΔP entry : hole gap friction, MPa; ΔP perf : eyelet friction, MPa; ΔP nwbf : fracture friction, MPa; Because the reservoirs in the Sa zero group have a shallow burial depth, weak rock cementation strength, single fracturing fracture morphology and negligible fracture friction.

4. The method of calculating the friction of a fracturing fluid pipe string of claim 1, wherein, Step S3 specifically comprises: calculating the hole frictional resistance ΔP according to the hole frictional resistance empirical formula perf = 2.2326 x 10 -4 Q 2 ρ / n 2 d 4 C 2 It can be seen that, since the highest operating discharge of the contrast well is the same, except for the fracturing fluid density, other parameters can be considered the same, therefore, the hole frictional resistance is positively correlated with the fracturing fluid density; Available: ΔP of hole friction of the construction well perf = ΔP of hole friction of the offset well perf x p 施工井 ÷ p 对比井 ; wherein, p: fracturing fluid density, kg / cm 3 ; n: number of perforations; d: perforation diameter, mm; C: perforation flow coefficient, indicating the effect of the perforation entrance shape on the pressure drop; Because the test fracturing has a small amount of liquid passing through the hole, the flow coefficient of the hole is the same.

5. The method of calculating the friction of a fracturing fluid pipe string of claim 3 wherein, Step S4 specifically comprises: according to the friction calculation formula in step S2, the following formula can be obtained Frictional pressure drop ΔP hf = surface construction pressure P surf - instantaneous shut-in pressure after pumping ISIP surf - hole friction ΔP perf Pipe column friction coefficient ΔP f = frictional resistance ΔP hf ÷ pipe column length L.

6. The method of calculating the friction of a fracturing fluid pipe string of claim 1 wherein, Step S5 specifically comprises: the hole friction under different construction displacements is calculated by the methods in steps S3 and S4 respectively, the pipe string friction resistance and the pipe string friction resistance coefficient of the alcohol-based fracturing fluid under different displacements are obtained, and the pipe string friction resistance chart of the alcohol-based fracturing fluid under different displacements is established.

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