A downhole pulse discharge parameter optimization method for various completion methods

Abstract

The present invention discloses a method for optimizing downhole pulse discharge parameters for various completion methods, including calculating the static Young's modulus and static Poisson's ratio of the target transformation section; calculating the fracture pressure of the target transformation section; calculating the electric pulse shock wave energy required at each section; performing an indoor electric pulse striking experiment simulating formation conditions on the reservoir core of the target transformation section; drawing a scatter plot with the wave velocity of the reservoir core as the vertical axis and the number of strikes as the horizontal axis, and fitting a relationship curve between the wave velocity and the number of strikes and the equation of the relationship curve; calculating the degree of damage of the reservoir core every 10 strikes; calculating the optimal sound velocity after striking at each section of the target transformation section; and calculating the optimal number of strikes at each section of the target transformation section. The present invention uses field logging data combined with rock mechanics and electric pulse indoor experiments to obtain the optimal downhole pulse discharge parameters; wherein the field logging data is used for calculation, so that the data obtained by this method is more accurate.

Description

Technical Field

[0001] The invention relates to a method for optimizing downhole pulse discharge parameters for various well completion modes, belonging to the technical field of oil and gas development. Background Art

[0002] The shock waves generated by pulse discharge in oil and gas wells can remove blockages and scale, transform reservoirs, and achieve the effect of increasing production and injection, so it has been widely used. In the process of pulse discharge, most of the existing construction parameters are set using laboratory + field experience, especially the setting of the number of pulse discharges. Due to the complex underground reservoir conditions and the strong heterogeneity of reservoir rocks, there is little research on optimization, resulting in a lack of basis for construction parameters.

[0003] At present, there is no public optimization of electric pulse construction parameters in China, most of which are based on point "replacing" the surface, and there is a lack of systematic optimization methods. This patent mainly uses field logging data combined with rock mechanics and electric pulse indoor experiments to propose a method for optimizing electric pulse discharge parameters for the entire target well section for completed oil and gas wells. Summary of the invention

[0004] In order to overcome the problems in the prior art, the present invention provides a method for optimizing downhole pulse discharge parameters for various completion modes.

[0005] The technical solution provided by the present invention to solve the above technical problems is: a method for optimizing downhole pulse discharge parameters for various completion methods, comprising the following steps:

[0006] Step S1, using the logging data to calculate the dynamic Young's modulus and dynamic Poisson's ratio at each location of the target transformation well section;

[0007] Step S2, performing triaxial mechanical tests on the reservoir core of the target reformed well section to obtain the compressive strength, static Young's modulus, and static Poisson's ratio of the reservoir core;

[0008] Step S3, obtaining a dynamic-static rock mechanics conversion relationship according to the static Young's modulus, dynamic Young's modulus, static Poisson's ratio, and dynamic Poisson's ratio in steps S1 and S2, and calculating the static Young's modulus and static Poisson's ratio at each location of the target reformed well section according to the dynamic-static rock mechanics conversion relationship;

[0009] Step S4, performing stress analysis at each location of the target transformation well section to clearly identify stress forms of horizontal and vertical cracks;

[0010] Step S5, according to the stress analysis performed in step S4, the fracture pressure at each location of the target transformation well section is calculated using the logging data, the static Young's modulus and the static Poisson's ratio at each location of the target transformation well section;

[0011] Step S6, calculating the electric pulse shock wave energy required at each location of the target transformation well section according to the fracture pressure at each location of the target transformation well section;

[0012] Step S7, using the electric pulse shock wave energy calculated in step S6, to conduct an indoor electric pulse striking experiment simulating formation conditions on the reservoir core of the target reformed well section, thereby obtaining experimental data;

[0013] Step S8, drawing a scatter plot with the reservoir core wave velocity as the vertical axis and the number of hits as the horizontal axis according to the experimental data, and fitting a relationship curve between the wave velocity and the number of hits and an equation for the relationship curve;

[0014] Step S9, calculating the damage degree of the reservoir core every 10 hits according to the experimental data in step S7;

[0015] Step S10, draw a scatter plot with the damage degree as the vertical axis and the number of hits as the horizontal axis; and fit a relationship curve between the damage degree and the number of hits and an equation for the relationship curve;

[0016] Step S11, taking the average slope of the relationship curve fitted in step S10 as the optimal slope, and determining the damage degree corresponding to the slope as the optimal damage degree;

[0017] Step S12, calculating the optimal post-strike sound velocity at each location of the target transformed well section according to the optimal damage degree obtained in step S11 and the well logging data of the target transformed well section;

[0018] Step S13, substituting the optimal sound velocity after striking calculated in step S12 into the curve equation of the relationship between the wave velocity and the striking number obtained in step S8, and calculating the optimal striking number at each location of the target transformation well section.

[0019] A further technical solution is that the calculation formula in step S1 is:

[0020]

[0021]

[0022] Where: ρ is the volume density of rock, g / cm 3 ; β is the conversion coefficient, dimensionless; Δt s 2 is the formation shear wave time difference, μs / ft; E is the formation P-wave time difference, μs / ft; d Dynamic Young's modulus; μ d is the dynamic Poisson's ratio.

[0023] A further technical solution is to perform triaxial mechanical experiments on multiple reservoir cores of target reformed well sections in step S2.

[0024] A further technical solution is that the calculation formula of the bursting pressure in step S5 is:

[0025] When the well is completed as an open hole completion, the fracture pressure of the vertical fracture is:

[0026]

[0027] The rupture pressure of a horizontal crack is:

[0028]

[0029] When the completion is perforated, the fracture pressure of the vertical fracture is:

[0030]

[0031] The rupture pressure of a horizontal crack is:

[0032]

[0033] Where: P P is the formation pore pressure, MPa; μ is the static Poisson's ratio, dimensionless; k is the tectonic stress coefficient, dimensionless; S is the overburden stress, MPa; S t is the tensile strength of rock, MPa; σ1 is the maximum horizontal principal stress, MPa; σ2 is the minimum horizontal principal stress, MPa; φ C is the contact porosity, %.

[0034] A further technical solution is that the calculation formula in step S6 is:

[0035]

[0036] P2=P1-P0

[0037] Where: P2 is the impact pressure, MPa; P0 is the hydrostatic pressure, MPa; d is the upper and lower distances of the high-voltage electrodes, m; γ is the shock wave attenuation coefficient, dimensionless; r d is the distance between the measuring point and the electrode, m; V is the propagation speed of the shock wave in the liquid, m / s; ε, α and E are the state parameters of the electrode spacing, dimensionless; E B It is the energy of electric pulse shock wave.

[0038] A further technical solution is that the indoor electric pulse striking experiment in step S7 is specifically as follows: before the experiment, an acoustic wave characteristic test is performed on the reservoir core to obtain an initial wave velocity, and after each 10 strikes on the reservoir core, an acoustic wave characteristic test is performed on the reservoir core to obtain a changing wave velocity after the strike, with a total of 100 to 200 strikes.

[0039] A further technical solution is that the calculation formula in step S9 is:

[0040]

[0041] Where: v0 is the acoustic wave velocity of the rock before discharge; v is the acoustic wave velocity of the rock after discharge; D is the degree of damage.

[0042] The present invention has the following beneficial effects: the present invention utilizes field logging data combined with rock mechanics and electric pulse indoor experiments to obtain the optimal downhole pulse discharge parameters; wherein the field logging data is used for calculation, so the data obtained by this method is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flowchart of the present invention;

[0044] Figure 2 It is a diagram showing the relationship between wave speed and number of hits;

[0045] Figure 3 This is a diagram showing the relationship between the degree of damage and the number of hits. DETAILED DESCRIPTION

[0046] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. 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.

[0047] like Figure 1 As shown, a method for optimizing downhole pulse discharge parameters for various completion methods of the present invention comprises the following steps:

[0048] Step 1: Use the depth and transverse and longitudinal wave time difference data in the well logging data to calculate the dynamic Young's modulus and dynamic Poisson's ratio at each location of the target transformation well section. The calculation formula is as follows:

[0049]

[0050]

[0051] Where: ρ is the volume density of rock, g / cm 3 ; β is the conversion coefficient, dimensionless; is the formation shear wave time difference, μs / ft; E is the formation P-wave time difference, μs / ft; d Dynamic Young's modulus; μ d is the dynamic Poisson’s ratio;

[0052] Step 2: Conduct triaxial mechanical tests on the reservoir core of the target reformed well section to obtain the compressive strength, static Young's modulus, and static Poisson's ratio of the reservoir core;

[0053] Step 3: Calculate the dynamic-static rock mechanics conversion relationship according to the static Young's modulus and static Poisson's ratio in step 2 and the dynamic Young's modulus and dynamic Poisson's ratio of the reservoir core at the location in step 1, and calculate the static Young's modulus and static Poisson's ratio at each location of the target reformed well section according to the dynamic-static rock mechanics conversion relationship;

[0054] Step 4: Conduct stress analysis at each location of the target transformation well section to identify the stress patterns of horizontal and vertical cracks;

[0055] Step 5: According to the stress analysis done in step 4, the six data of depth, porosity, shale content, density and transverse and longitudinal wave time difference in the well logging data are combined with the static Young's modulus and static Poisson's ratio of each location in the target transformation well section obtained in step 3 to calculate the fracture pressure at each location in the target transformation well section. The calculation formula is as follows:

[0056] When the well is completed as an open hole completion, the fracture pressure of the vertical fracture is:

[0057]

[0058] The rupture pressure of a horizontal crack is:

[0059]

[0060] When the completion is perforated, the fracture pressure of the vertical fracture is:

[0061]

[0062] The rupture pressure of a horizontal crack is:

[0063]

[0064] Where: P P is the formation pore pressure, MPa; μ is the static Poisson's ratio, dimensionless; k is the tectonic stress coefficient, dimensionless; S is the overburden stress, MPa; S t is the tensile strength of rock, MPa; σ1 is the maximum horizontal principal stress, MPa; σ2 is the minimum horizontal principal stress, MPa; φ C is the contact porosity, %;

[0065] Step 6: Using the fracture pressure at each location of the target transformation well section obtained in step 5, calculate the electric pulse shock wave energy required at each location of the target transformation well section. The calculation formula is as follows:

[0066]

[0067] P2=P1-P0

[0068] Where: P2 is the impact pressure, MPa; P0 is the hydrostatic pressure, MPa; d is the upper and lower distances of the high-voltage electrodes, m; γ is the shock wave attenuation coefficient, dimensionless; r d is the distance between the measuring point and the electrode, m; V is the propagation speed of the shock wave in the liquid, m / s; ε, α and E are the state parameters of the electrode spacing, dimensionless; E B It is the energy of electric pulse shock wave;

[0069] Step 7: Using the electric pulse shock wave energy optimized in step 6, an indoor electric pulse striking experiment simulating formation conditions is performed on the reservoir core of the target reformed well section;

[0070] Before the experiment, the reservoir core was tested for acoustic wave characteristics to obtain the initial wave velocity, and the reservoir core was tested for acoustic wave characteristics to obtain the changing wave velocity after each 10 hits, with a total of 100 to 200 hits.

[0071] Step 8: Draw a scatter plot with the core wave velocity recorded in step 7 as the vertical axis and the number of hits as the horizontal axis, and fit the relationship curve between the wave velocity and the number of hits and the relationship curve equation;

[0072] Step 9: Based on the wave velocity data before and after the reservoir core is hit obtained in step 7, calculate the damage degree of the reservoir core every 10 hits. The calculation formula is as follows:

[0073]

[0074] Where: v0 is the acoustic wave velocity of the reservoir core before discharge; v is the acoustic wave velocity of the reservoir core after discharge; D is the degree of damage;

[0075] Step 10: Draw a scatter plot with the damage degree calculated for each reservoir core in step 9 as the vertical axis and the number of hits as the horizontal axis; and fit a relationship curve between the damage degree and the number of hits and the relationship curve equation;

[0076] Step 11: Taking the average slope of the relationship curve fitted in step 10 as the optimal slope, and setting the damage degree corresponding to the slope as the optimal damage degree;

[0077] Step 12: Calculate the optimal post-strike sound velocity at each location of the target transformation well section based on the optimal damage degree obtained in step 11 and the well logging data of the target transformation well section;

[0078] Step 13: Substitute the optimal sound velocity after striking calculated in step 12 into the curve equation of the relationship between wave velocity and striking number obtained in step 8 to calculate the optimal striking number at each location of the target transformation well section.

[0079] Example

[0080] Take the oil well L76 in Block X of a certain oil field as an example. The well is completed by casing perforation. The designed target layer for transformation is buried at a depth of 2983.0-3003.0m and the transformation thickness is 20m.

[0081] (1) Based on the L76 logging data, the dynamic Young's modulus at the target reformed well section 117 is calculated to be 12.52-15.39 GPa, and the dynamic Poisson's ratio is 0.31-0.33;

[0082] (2) Through triaxial rock mechanics parameter measurement experiments, it was found that the overall range of compressive strength of the four rock samples in Well L76 was 59-67.4 MPa; the overall range of static Young's modulus was 7.0951-8.8604 GPa; and the overall range of static Poisson's ratio was 0.08-0.1;

[0083] (3) The dynamic Young's modulus and Poisson's ratio data corresponding to the rock sample depth are selected from the well logging calculation data, and the dynamic and static Young's modulus and Poisson's ratio are fitted with the experimental data to obtain the dynamic and static rock mechanics conversion equations:

[0084] Static Young's modulus: E s =-1.8982E d +32.493

[0085] Static Poisson's ratio: μ s =-2μ d +0.76

[0086] After transformation, the static Young's modulus of the L76 well in the transformed section ranged from 3.27 to 8.72 GPa, and the static Poisson's ratio ranged from 0.1 to 0.14.

[0087] (4) Based on the data collected and analyzed in the early stage, it is determined that horizontal fractures occur in Well L76. According to the formula, the overall range of the fracture pressure of the reformed well section is 66.0 to 68.17 MPa;

[0088] (5) The capacitance C of the energy storage capacitor of the electric pulse device used in the test is 100 μF. According to the previous indoor test results, the propagation speed V of the shock wave in the liquid is 1500 m / s, the upper and lower spacing d of the high-voltage electrode is 0.005 m, the distance r between the measuring point and the electrode is 0.015 m, the shock wave attenuation coefficient γ is 2089, the state parameter k of the electrode spacing is 9 / d, α is 0.35, and E is 1;

[0089] Through calculation, it is found that the overall range of the shock pressure required at each location of the L76 well reconstruction section is 36.78-38.86MPa; therefore, the overall range of the electric pulse shock wave energy required at each location after optimization is 1.93-2.26KJ;

[0090] (6) Based on the electric pulse shock wave energy obtained in the previous step, an indoor electric pulse striking experiment simulating the formation conditions is designed; the core wave velocity is statistically correlated with the striking number data, and a scatter plot is drawn, and then the relationship curve equation is obtained by fitting:

[0091] y=3729.4e -0.023x

[0092] (7) The wave velocity calculated in the previous step is calculated as the damage degree through the formula, and a scatter plot of the damage degree and the number of hits is redrawn, and the relationship curve is fitted to find the optimal damage degree is 0.82;

[0093] (8) Substituting the optimal damage degree value into the acoustic logging data in the logging data, the acoustic velocity after transformation at each location of the transformed well section can be calculated, and combined with the relationship curve equation obtained in step (6), the optimal number of strikes at each location of the transformed well section is calculated to be in the overall range of 29 to 38;

[0094] (9) Based on the above calculation data and the logging data and the range of action of the electric pulse equipment, the electric pulse discharge construction parameters of Well L76 are further designed as shown in the following table:

[0095] Table 1 L76 Well Electric Pulse Discharge Construction Parameters

[0096]

[0097]

[0098] The above description is not intended to impose any form of limitation on the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing downhole pulse discharge parameters for various completion methods, characterized in that: The steps include: Step S1, using the logging data to calculate the dynamic Young's modulus and dynamic Poisson's ratio at each location of the target transformation well section; Step S2, performing triaxial mechanical tests on the reservoir core of the target reformed well section to obtain the compressive strength, static Young's modulus, and static Poisson's ratio of the reservoir core; Step S3, obtaining a dynamic-static rock mechanics conversion relationship according to the static Young's modulus, dynamic Young's modulus, static Poisson's ratio, and dynamic Poisson's ratio in steps S1 and S2, and calculating the static Young's modulus and static Poisson's ratio at each location of the target reformed well section according to the dynamic-static rock mechanics conversion relationship; Step S4, performing stress analysis at each location of the target transformation well section to clearly identify stress forms of horizontal and vertical cracks; Step S5, according to the stress analysis performed in step S4, the fracture pressure at each location of the target transformation well section is calculated using the logging data, the static Young's modulus and the static Poisson's ratio at each location of the target transformation well section; Step S6, calculating the electric pulse shock wave energy required at each location of the target transformation well section according to the fracture pressure at each location of the target transformation well section; Step S7, using the electric pulse shock wave energy calculated in step S6, to conduct an indoor electric pulse striking experiment simulating formation conditions on the reservoir core of the target reformed well section, thereby obtaining experimental data; Step S8, drawing a scatter plot with the reservoir core wave velocity as the vertical axis and the number of hits as the horizontal axis according to the experimental data, and fitting a relationship curve between the wave velocity and the number of hits and an equation for the relationship curve; Step S9, calculating the damage degree of the reservoir core every 10 hits according to the experimental data in step S7; Step S10, drawing a scatter plot with the damage degree as the vertical axis and the number of hits as the horizontal axis; And fit the relationship curve between the damage degree and the number of hits and the relationship curve equation; Step S11, taking the average slope of the relationship curve fitted in step S10 as the optimal slope, and determining the damage degree corresponding to the slope as the optimal damage degree; Step S12, calculating the optimal post-strike sound velocity at each location of the target transformed well section according to the optimal damage degree obtained in step S11 and the well logging data of the target transformed well section; Step S13, substituting the optimal sound velocity after striking calculated in step S12 into the curve equation of the relationship between the wave velocity and the striking number obtained in step S8, and calculating the optimal striking number at each location of the target transformation well section.

2. The downhole pulse discharge parameter optimization method for multiple completion modes according to claim 1, characterized in that: The calculation formula in step S1 is: Where: ρ is the volume density of rock, g / cm 3 ; β is the conversion coefficient, dimensionless; is the formation shear wave time difference, μs / ft; E is the formation P-wave time difference, μs / ft; d Dynamic Young's modulus; μ d is the dynamic Poisson's ratio.

3. The downhole pulse discharge parameter optimization method for multiple completion modes according to claim 1, characterized in that: In the step S2, triaxial mechanical experiments are performed on the reservoir cores of multiple target reformed well sections.

4. The downhole pulse discharge parameter optimization method for multiple completion modes according to claim 1, characterized in that: The calculation formula of the bursting pressure in step S5 is: When the well is completed as an open hole completion, the fracture pressure of the vertical fracture is: The rupture pressure of a horizontal crack is: When the completion is perforated, the fracture pressure of the vertical fracture is: The rupture pressure of a horizontal crack is: Where: P P is the formation pore pressure, MPa; μ is the static Poisson's ratio, dimensionless; σ1 is the maximum horizontal principal stress, MPa; σ2 is the minimum horizontal principal stress, MPa; φ C is the contact porosity, %.

5. The method for optimizing downhole pulse discharge parameters for various completion methods according to claim 1, characterized in that: The calculation formula in step S6 is: P2=P1-P0 Where: P2 is the impact pressure, MPa; P0 is the hydrostatic pressure, MPa; d is the upper and lower distances of the high-voltage electrodes, m; γ is the shock wave attenuation coefficient, dimensionless; r d is the distance between the measuring point and the electrode, m; V is the propagation speed of the shock wave in the liquid, m / s; ε, α and E are state parameters of the electrode spacing, dimensionless; E B is the electric pulse shock wave energy; P1 is the rupture pressure, MPa.

6. The downhole pulse discharge parameter optimization method for multiple completion modes according to claim 1, characterized in that: The indoor electric pulse striking experiment in step S7 is specifically as follows: before the experiment, the reservoir core is subjected to an acoustic wave characteristic test to obtain an initial wave velocity, and after each 10 strikings, the reservoir core is subjected to an acoustic wave characteristic test to obtain a variable wave velocity after the striking, with a total of 100 to 200 strikings.

7. The downhole pulse discharge parameter optimization method for multiple completion modes according to claim 6, characterized in that: The calculation formula in step S9 is: Where: v0 is the acoustic wave velocity of the rock before discharge; v is the acoustic wave velocity of the rock after discharge; D is the degree of damage.

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