CN111798328A - Method for calculating five-point well pattern instantaneous yield of low-permeability oil reservoir - Google Patents
Method for calculating five-point well pattern instantaneous yield of low-permeability oil reservoir Download PDFInfo
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Abstract
The invention provides a method for calculating the instantaneous yield of a low-permeability oil reservoir five-point well pattern, which comprises the following steps of: collecting fracture parameters and initial saturation of a target block fracturing well section, selecting a five-point well pattern, and establishing an injection-production unit physical model of the five-point well pattern; dividing the injection-production unit into a plurality of subunits, and determining the instantaneous yield of each subunit at the starting moment; adding the yields of all the subunits to obtain the five-point well pattern instantaneous yield at the starting moment; and sequentially calculating the instantaneous yield of the five-point well pattern at the nth moment by adopting an iteration method according to the instantaneous yield of the five-point well pattern at the starting moment and the initial saturation to obtain the instantaneous yield of the five-point well pattern at N moments in the whole time period of the five-point well pattern, wherein N is a positive integer larger than 1, and N is a positive integer smaller than or equal to N. The method has the advantage that the instantaneous yield of the five-point well pattern can be quickly and effectively obtained.
Description
Technical Field
The invention relates to the field of oil and gas exploration, in particular to a method for calculating the instantaneous yield of a low-permeability reservoir five-point well pattern.
Background
Water-drive oil recovery is an effective way to maintain reservoir pressure and has been widely used to increase oil recovery. At present, most of water-flooding oil reservoirs in China are still in a high water-cut period. Due to the heterogeneity of the reservoir, the water flooding coverage of different areas is different, which results in uneven distribution of the remaining oil during high water content periods. Therefore, when the five-point well pattern instantaneous production of the low permeability reservoir in the high water period is obtained, the heterogeneity of the residual oil must be considered.
The method for solving the area well pattern is mainly focused on a pull-type inversion method, a conformal transformation method, an equivalent seepage resistance method, a flow tube integration method, a numerical simulation method and a split flow field method through research and research of patent at home and abroad and literature. Although the methods for solving the area well pattern are more and the established model is more complex, certain defects still exist, and the method mainly comprises the following aspects: 1. the seepage model is over-ideal, only single-phase flow is considered, and the distribution condition of residual oil in a reservoir and the effect of water flooding are not completely considered; 2. the calculation unit is usually centralized in an injection-production unit, and has a certain difference with an actual low-permeability reservoir development well pattern; 3. the model building process has a plurality of assumed conditions, the derivation process is complex, and the calculation is inconvenient. Therefore, it is highly desirable to establish a new and fast method for calculating the production of an area well pattern.
In the text of the low permeability reservoir area well pattern yield calculation method published in the university of haar Binshi at 21 st period 1 by Liuhailong and Wushuhong in 2016, a numerical model for calculating the five-point well pattern yield is established by adopting a streamline integral method, an analytical model of an area well pattern is not obtained due to divergence of an equation, and an iterative solution is needed.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a method for calculating the instantaneous yield of a low-permeability reservoir five-point well pattern, which comprises the following steps:
s1, collecting fracture parameters and initial saturation of a target block fracturing well section, selecting a five-point well pattern, and establishing an injection-production unit physical model of the five-point well pattern;
s2, dividing the injection-production unit into a plurality of subunits, and determining the instantaneous yield of each subunit at the starting moment according to the fracture parameters, the oilfield related parameters and the initial saturation;
s3, adding the yields of all the subunits to obtain the five-point well pattern instantaneous yield at the starting moment;
and S4, sequentially calculating the five-point well pattern instantaneous yield of the nth moment by adopting an iteration method according to the five-point well pattern instantaneous yield and the initial saturation of the starting moment to obtain the five-point well pattern instantaneous yields of the five-point well pattern at N moments in the whole time period, wherein N is a positive integer larger than 1, and N is a positive integer smaller than or equal to N.
In one embodiment, the fracture parameters in step S1 include: the fracture length of the injection well, the fracture length of the production well, the row spacing of the production well and the injection well and the spacing between two adjacent injection wells.
In one embodiment, the voidage replacement cells in step S2 are divided into 4 rectangular cells, each rectangular cell divided into three sub-cells, the sub-cells including triangular cells and quadrilateral cells.
In one embodiment, in step S2, the instantaneous yield of the triangle cells is determined according to the following equation:
wherein γ represents a unit conversion factor, Q01Represents the yield of said triangular units in sm3/d， koDenotes permeability, swDenotes the average saturation, μoDenotes crude oil viscosity, h denotes effective reservoir thickness, G denotes onset pressure gradient, PinIndicating the bottom hole flow pressure of the injection well, PproIndicating the bottom hole flow pressure, L, of the production well1Representing the length of the flow tube of a five-point well pattern unit, L2Denotes the spacing of adjacent injection wells, LfwRepresents the half-length of the fracture of the injection well in m; r iswRepresents the radius of the well in m; w is afDenotes the width of the crack, in m; alpha is alpha1The included angle of the injection and production wells in the triangular unit is expressed in unit degrees; alpha is alpha11The included angle of the flow tube in the injection-production unit is expressed in unit degrees; ratio1 denotes the ratio of the length of the producing well to the length of the injection well, BoRepresenting the crude oil volume coefficient.
In one embodiment, in step S2, the yield of the quad sub-cells is determined according to the following equation,
when L is1≠L2Then, the following equation is used to calculate:
when L is1＝L2Then, the following equation is used to calculate:
wherein L isfoDenotes the half-length of the fracture, Δ q, of the producing wello2The yield of any flow tube in a quadrilateral unit is expressed in sm3D; gamma is a unit conversion factor, Qo2、Qo2' is the yield of the corresponding quadrilateral injection-production unit, and the unit is sm3/d，koDenotes permeability, swDenotes the degree of saturation, μoDenotes the viscosity of the crude oil, h denotes the reservoirEffective thickness, G denotes the starting pressure gradient, PinIndicating the bottom hole flow pressure of the injection well, PproIndicating the bottom hole flow pressure, L, of the production well1Representing the length of the flow tube in quadrilateral units, L2Denotes the spacing of adjacent injection wells, LfwRepresents the half-length of the fracture of the injection well in m; r iswRepresents the radius of the well in m; w is afDenotes the width of the crack, in m; ratio2 denotes L1And L2Ratio of (A) to (B)oRepresenting the crude oil volume coefficient.
In one embodiment, the startup pressure gradient G is determined by the following equation:
wherein the parameters and n represent regression coefficients, and the values of the parameters and n are 1.2427 and 0.9753, swnDenotes the normalized saturation, k denotes the permeability, μoDenotes the crude oil viscosity, μwIndicating the viscosity of the water.
In one embodiment, the permeability k is:
k＝krw+kro
wherein k represents permeability, krwDenotes the relative permeability of the aqueous phase, kroRepresenting the relative permeability of the oil phase.
In one embodiment, the relative permeability k of the aqueous phaserwDetermined by calculation with the Parker-Lenhard model:
relative permeability k of oil phaseroDetermined by calculation through a Brooks-Corey-Burdine model:
wherein k isrwDenotes the relative permeability of the aqueous phase, kroRepresenting the relative permeability of the oil phase; soIs expressed as containingOil saturation; m represents a fitting parameter.
In one embodiment, in step S4, the relationship between the average saturation at the n +1 th time and the average saturation at the n-th time is calculated as follows:
and tn+1Average saturation of lower; vφjRepresenting the pore volume of the injection-production unit; qosjIndicating injection and production unit at time tnYield in sm3/d。
Compared with the prior art, the method has the advantages that the method can dynamically adjust the yield of the injection-production well pattern in real time according to the oil saturation of the injection-production well, the calculated five-point well pattern yield has timeliness, an effective and novel calculation method is provided for improving the calculation precision and speed of the instantaneous yield of the low-permeability oil reservoir, and meanwhile, a certain technical support is provided for the design of the well pattern and the establishment of a later development scheme. Secondly, the method is wide in application range, can be suitable for five-point well patterns with any shapes in the high water-cut period of low-permeability oil reservoirs, can be suitable for direct injection or reverse injection, and can be suitable for both vertical wells and horizontal wells or combination of the vertical wells and the horizontal wells, and compared with other methods, the method is higher in calculation accuracy and efficiency.
Drawings
Preferred embodiments of the present invention will be described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 shows a flow chart of a method of calculating the instantaneous production of a five-point well pattern in an embodiment of the invention.
FIG. 2 shows a physical model diagram of the instantaneous production of a five-point well pattern in an embodiment of the invention.
FIG. 3 shows a schematic diagram of a five-point pattern transient resolution unit in an embodiment of the invention.
FIG. 4 shows a schematic representation of the five point pattern triangle subunit production in an embodiment of the present invention.
FIG. 5 shows a schematic representation of the production of a five-point well pattern quadrilateral subunit of an embodiment of the present invention.
FIG. 6 is a schematic illustration of another quadrilateral subunit production of a five-point well pattern in accordance with an embodiment of the present invention.
FIG. 7 shows a facies plot of instantaneous production from a five-point well pattern in an embodiment of the present invention.
FIG. 8 shows a plot of calculated five-point well pattern instantaneous production versus actual production in an embodiment of the present invention.
In the drawings, like parts are designated with like reference numerals, and the drawings are not drawn to scale.
Detailed Description
The invention will be further explained with reference to the drawings.
In order to achieve the aim, the invention discloses a method for calculating the instantaneous yield of a low-permeability reservoir five-point well pattern, which comprises the following steps of:
firstly, collecting the fracture basic parameters of the fractured well section of the injection and production unit of the target block, including the length of the fractures in the well pattern. And (3) arranging the fracture parameters of at least one five-point injection-production unit well pattern, and then establishing an injection-production unit physical model of the five-point well pattern according to the shape and the oil reservoir characteristics of the injection-production five-point unit.
Then, according to the oil reservoir development dynamic and production dynamic data of the target block, dividing the five-point injection-production unit well pattern into four subunits, then according to the angles and orientations of the side wells and the corner wells, the well spacing of injection-production and the distribution condition of streamlines in the production process, subdividing the four subunits into 12 subunits again, wherein the subdivided 12 subunits are not regular in shape due to different distribution of the side wells and the corner wells and uneven distribution of the streamlines, and mainly comprise triangular subunits and quadrilateral subunits. And sequentially acquiring the residual oil distribution conditions of the 12 subunits according to the injection-production corresponding relation, the streamline flow direction and the residual oil distribution conditions, and sequentially acquiring the oil saturation at different time steps under the given initial oil saturation condition by taking time as an iteration step length and according to the change condition of the residual oil.
According to the relation between the permeability and the oil saturation (a Parker-Lenhard model and a Brooks-Corey-Burdine model), the average permeability of 12 subunits is sequentially obtained, and then according to the relation between the starting pressure gradient and the permeability and the normalized saturation, the starting pressure gradient under different time step lengths is obtained.
And then, adopting a flow tube integration method to sequentially obtain the yields of the subunits with different shapes (a triangular subunit and a quadrangular subunit). The method is characterized in that a targeted model is established according to the actual fracture length pressing condition of the injection and production well, whether the fracture lengths of the injection and production wells are equal or not has great influence on flow calculation of an injection and production unit, and the model is selected according to the actual condition. And finally, calculating the five-point well pattern instantaneous yield of the target block at different time steps by time step superposition, and unifying the whole time steps to obtain the five-point well pattern instantaneous yield of the target block at any development time.
By taking the instantaneous yield of the five-point well pattern as a target function, the yield under different injection-production well distances can be obtained, so that the injection-production well distance is optimized, and theoretical support is provided for optimization of the injection-production well distance of the five-point well pattern.
The above calculation steps are explained in detail as follows:
step (1): conceptual model building
Because the reservoir seepage resistance of the low-permeability reservoir is large, hydraulic fracturing is needed, and the reservoir needs to be jetted and opened to a certain extent no matter a production well or an injection well, a physical model of an injection and production unit of a five-point well pattern is shown in figure 2. Setting the half-length of the fracture of the injection well to LfwThe half-length of the fracture of the production well is Lfo. The row distance between the production well and the injection well is L1The distance between two corner wells (injection wells) is L2。
Step (2): subdivision unit
Through element analysis, the injection-production unit of the five-point well pattern is divided into four Subunits (SU), and each subunit is divided into three subunits according to streamline distribution characteristics. Thus, one injection-production unit of a five-point well pattern is divided into 12 subunits, as shown in fig. 3.
As can be seen from fig. 3, in the subdivided units, there are triangular injection and production subunits (e.g., CU1, CU3) and quadrangular injection and production subunits (e.g., CU2, CU5) because the injection and production wells have different hydraulic fracture scales in fracture design and construction, and therefore, for the quadrangular injection and production units, it is also necessary to consider whether the fracture lengths of the injection and production wells are equal, because the difference in fracture lengths will directly affect the flow conditions of the injection and production units.
And (3): oil saturation acquisition
Generally, during periods of high water content, the process of two-phase flow is instantaneously variable. However, from the successive steady state method: transient flow processes are a superposition of many steady flow processes. Therefore, the key to the successive steady state approach is how to connect each steady flow process at each discrete time. From the law of conservation of mass:
in the formula: j represents the number of the injection-production unit;
and
respectively representing the injection-production unit at time tnAnd tn+1Average saturation of lower; vφjRepresenting the pore volume of the injection-production unit; qosjIndicating injection and production unit at time tnYield in sm3/d。
And (4): key parameter acquisition
Obtaining average permeability of 12 subunits in sequence according to the relation between permeability and oil saturation (a Parker-Lenhard model and a Brooks-Corey-Burdine model), and then obtaining starting pressure gradients under different time step lengths by utilizing the relation between the starting pressure gradient and the permeability and the normalized saturation;
the Parker-Lenhard model calculates the relative permeability of the water phase as shown in formula (2):
calculating the relative permeability of the oil phase by using a Brooks-Corey-Burdine model, wherein the formula is (3):
in the formula: k is a radical ofrwDenotes the relative permeability of the aqueous phase, kroRepresenting the relative permeability of the oil phase; soRepresents the oil saturation; m represents a fitting parameter.
Starting the calculation of the pressure gradient, using equation (4):
in the formula:
the parameter and n are regression coefficients，The values of the parameters and n are 1.2427 and 0.9753。SwnFor normalized saturation, k denotes permeability, μoDenotes the crude oil viscosity, μwIndicating the viscosity of the water.
And (5): well pattern production calculation
Obtaining the yield of triangular subunit
Calculating the flow of each triangular subunit, and calculating the yield of the triangular injection and production subunits by using a flow tube integration method and taking the calculation of any triangular subunit as an example as shown in fig. 4.
The triangular injection-production subunit adopts a formula (5):
in the formula:
Lfodenotes the half-length of the fracture of the producing well, gamma denotes the unit conversion factor, Δ q02The yield of any flow tube in a quadrilateral unit is expressed in sm3/d；Q02、Q02' is the yield of the corresponding quadrilateral injection-production unit, and the unit is sm3/d，koDenotes permeability, swDenotes the degree of saturation, μoDenotes crude oil viscosity, h denotes effective reservoir thickness, G denotes onset pressure gradient, PinIndicating the bottom hole flow pressure of the injection well, PproIndicating the bottom hole flow pressure, L, of the production well1Representing the length of the flow tube in quadrilateral units, L2Denotes the spacing of adjacent injection wells, LfwRepresents the half-length of the fracture of the injection well in m; r iswRepresents the radius of the well in m; w is afDenotes the width of the crack, in m; ratio2 denotes L1And L2Ratio of (A) to (B)oRepresenting the crude oil volume coefficient.
Acquisition of quadrilateral yield
Similar to the calculation of the yield of the triangular injection-production unit, the same method is adopted to calculate the yield of each quadrilateral subunit, one quadrilateral injection-production unit is arbitrarily selected, and the calculation of the yield of the quadrilateral injection-production unit is carried out as shown in fig. 5 and 6.
The quadrilateral yields for FIG. 5 are calculated as:
the quadrilateral yield corresponding to FIG. 6 is calculated as:
in the formula: l isfoDenotes the half-length of the fracture, Δ q, of the producing wello2The yield of any flow tube in a quadrilateral unit is expressed in sm3D; gamma is a unit conversion factor, Qo2、Qo2' is the yield of the corresponding quadrilateral injection-production unit, and the unit is sm3/d，koDenotes permeability, swDenotes the degree of saturation, μoDenotes crude oil viscosity, h denotes effective reservoir thickness, G denotes onset pressure gradient, PinIndicating the bottom hole flow pressure of the injection well, PproRepresenting production well bottom streamPressure, L1Representing the length of the flow tube in quadrilateral units, L2Denotes the spacing of adjacent injection wells, LfwRepresents the half-length of the fracture of the injection well in m; r iswRepresents the radius of the well in m; w is afDenotes the width of the crack, in m; ratio2 denotes L1And L2Ratio of (A) to (B)oRepresenting the crude oil volume coefficient.
③ five-point well pattern instantaneous yield acquisition
And the formula (8) is a low-permeability reservoir five-point well pattern instantaneous yield calculation model in the high water-cut period under the unsteady state.
The calculation steps for solving the unsteady state production of the five-point well pattern are as follows: acquiring basic parameters and initial saturation of a reservoir of each injection and production subunit SU from oil field data; the yield per CU at the start time is calculated using equation (5), (6) or (7). Calculating the instantaneous yield of the five-point well pattern at the starting moment by using a formula (8); substituting the yield into formula (1) to calculate the saturation of each subunit at the next moment; and (4) calculating the saturation of each subunit at the next moment in the step (I), repeating the steps to obtain the yield of the five-point well pattern corresponding to the next moment, and finally obtaining the instantaneous yield of the five-point well pattern in the whole time period.
Example one
The calculation method of the embodiment selects a certain injection-production well group of Daqingte 45 block to perform instantaneous capacity calculation description, and comprises the following steps:
(1) the fracturing parameters of the injection and production wells, such as the length of the fractures, are obtained through fracturing construction design reports and fracture monitoring data, and it is noted that the half-length of the fractures of the injection wells is 125m, while the half-length of the fractures of the production wells is 114m, which are not equal, so that the later quadrilateral subunit productivity calculation needs to select a model corresponding to the non-equidistant fractures.
(2) And collecting a basic information table of the oil reservoirs of the injection-production well group of the block, wherein specific parameters are shown in table 1.
Table 1 block oil reservoir basic information table for injection-production well group
(3) From the actual production dynamics, the target block is produced from 2012 at 10.10 and then stopped at 2015 at 2.11, and the production time period is selected: the study is carried out from 10.10 to 2.10 in 2012 to 2015, the production is 40 months, the time step is set to one month, and 40 times of iterative calculation are needed. By substituting the known parameters into equation (1), the saturation distribution of the previous time step and the next time step can be obtained, that is:
(4) and (3) sequentially normalizing the saturation obtained in the step (3), and substituting the normalized saturation into a formula (4) to obtain the starting pressure gradient under different time steps, namely:
meanwhile, the initial oil saturation and the binding formulae (2) and (3) were used to obtain a phase permeation curve, as shown in FIG. 7.
(5) Through 12 subdivided units which are divided, capacity calculation formulas under a triangular injection-production unit and a quadrilateral injection-production unit (with unequal cracks) can be obtained in sequence:
and (3) substituting the saturation obtained in the step (a) and the subunit average permeability reversely deduced by combining the phase permeation curve into the corresponding subunit productivity models in sequence, and calculating the instantaneous productivity at different time in sequence by a multi-iteration method in the step (5), wherein the calculation result is shown in fig. 8. Comparison with the actual production dynamic data for this block shows that: the relative error of the two yield calculations is controlled within 5 percent, and the method belongs to the error allowable range, which shows that the method is reasonable and scientific, and can realize the quick and accurate calculation of the instantaneous yield of the five-point well pattern.
Example two
This example provides an example of the method of the present invention to optimize the well spacing in an injection-production well pattern by calculating the individual well productivity of the well at different well spacings. Selecting a certain low-permeability production well of a long 813 reservoir of a red river oil field, setting the injection-production pressure difference to be 15MPa, and setting the radius of a shaft to be 0.1 m. The following detailed description of the well spacing optimization method is performed in combination with the steps of the present invention, which are as follows:
(1) and collecting related parameters of the injection and production well fractures, such as the length of the pressed fractures of the injection well, the length of the production well fractures and the like through fracture monitoring data.
(2) And collecting basic information of the oil reservoir, and specific parameters, as shown in the table 2.
TABLE 2 basic information Table for oil reservoirs
(3) By utilizing the steps, the productivity of the oil well at a certain well spacing is calculated, and when the injection-production differential pressure is 15MPa, the productivity calculation results of the oil wells at different well spacings are shown in Table 3. As can be seen from Table 3: when the well spacing of the injection and production well pattern is 250m, the productivity of the oil well is 15.61t/d, and when the well spacing of the injection and production well pattern is 200m, the productivity of the oil well is 15.68t/d. The yield difference between the well spacing 200m and 250m is small, but the excavation cost of the small well spacing is high, and the optimal well spacing of the selected well pattern is set to be 250m under the condition of comprehensively considering economic and technical feasibility.
TABLE 3 results of the calculation of the productivity of the single well of the oil well at different well intervals
| Well spacing (m) | Five-point well pattern single wellYield (m)3/d) |
| 100 | 15.71 |
| 150 | 15.68 |
| 200 | 15.64 |
| 250 | 15.61 |
| 300 | 13.88 |
| 325 | 12.92 |
| 350 | 12.07 |
| 375 | 11.04 |
| 400 | 10.12 |
The above is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily make changes or variations within the technical scope of the present invention disclosed, and such changes or variations should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (9)
1. A method for calculating the five-point well pattern instantaneous yield of a low permeability reservoir is characterized by comprising the following steps:
s1, collecting fracture parameters and initial saturation of a target block fracturing well section, selecting a five-point well pattern, and establishing an injection-production unit physical model of the five-point well pattern;
s2, dividing the injection-production unit into a plurality of subunits, and determining the instantaneous yield of each subunit at the starting moment according to the fracture parameters, the oilfield related parameters and the initial saturation;
s3, adding the yields of all the subunits to obtain the five-point well pattern instantaneous yield at the starting moment;
and S4, sequentially calculating the five-point well pattern instantaneous yield of the nth moment by adopting an iteration method according to the five-point well pattern instantaneous yield and the initial saturation of the starting moment to obtain the five-point well pattern instantaneous yields of the five-point well pattern at N moments in the whole time period, wherein N is a positive integer larger than 1, and N is a positive integer smaller than or equal to N.
2. The method for calculating the five-point well pattern instantaneous production of low permeability reservoirs of claim 1, wherein the fracture parameters in step S1 comprise: the fracture length of the injection well, the fracture length of the production well, the row spacing of the production well and the injection well and the spacing between two adjacent injection wells.
3. The method for calculating the instantaneous production of the low permeability reservoir five-point well pattern of claim 1, wherein the injection-production unit in step S2 is divided into 4 rectangular units, each rectangular unit is divided into three sub-units, and the sub-units comprise triangular units and quadrilateral units.
4. The method for calculating the instantaneous production of a low permeability reservoir five-point well pattern of claim 3, wherein in step S2, the instantaneous production of the triangular cells is determined according to the following equation:
wherein γ represents a unit conversion factor, Q01Represents the yield of said triangular units in sm3/d，koDenotes permeability, swDenotes the average saturation, μoDenotes crude oil viscosity, h denotes effective reservoir thickness, G denotes onset pressure gradient, PinIndicating the bottom hole flow pressure of the injection well, PproIndicating the bottom hole flow pressure, L, of the production well1Representing the length of the flow tube of a five-point well pattern unit, L2Denotes the spacing of adjacent injection wells, LfwRepresents the half-length of the fracture of the injection well in m; r iswRepresents the radius of the well in m; w is afDenotes the width of the crack, in m; alpha is alpha1The included angle of the injection and production wells in the triangular unit is expressed in unit degrees; alpha is alpha11The included angle of the flow tube in the injection-production unit is expressed in unit degrees; ratio1 denotes the ratio of the length of the producing well to the length of the injection well, BoRepresenting the crude oil volume coefficient.
5. The method for low permeability reservoir five-point well pattern transient production according to claim 3, wherein in step S2, the production of the quadrilateral sub-cells is determined according to the following equation,
when L is1≠L2Then, the following equation is used to calculate:
when L is1＝L2Then, the following equation is used to calculate:
wherein L isfoDenotes the half-length of the fracture, Δ q, of the producing wello2The yield of any flow tube in a quadrilateral unit is expressed in sm3D; gamma is a unit conversion factor, Qo2、Qo2' is the yield of the corresponding quadrilateral injection-production unit, and the unit is sm3/d，koDenotes permeability, swDenotes the degree of saturation, μoDenotes crude oil viscosity, h denotes effective reservoir thickness, G denotes onset pressure gradient, PinIndicating the bottom hole flow pressure of the injection well, PproIndicating the bottom hole flow pressure, L, of the production well1Representing the length of the flow tube in quadrilateral units, L2Denotes the spacing of adjacent injection wells, LfwRepresents the half-length of the fracture of the injection well in m; r iswRepresents the radius of the well in m; w is afDenotes the width of the crack, in m; ratio2 denotes L1And L2Ratio of (A) to (B)oRepresenting the crude oil volume coefficient.
6. The method of low permeability reservoir five-point well pattern transient production according to claim 4 or 5, wherein the onset pressure gradient G is determined by the following equation:
wherein the parameters and n represent regression coefficients, and the values of the parameters and n are 1.2427 and 0.9753, swnDenotes the normalized saturation, k denotes the permeability, μoDenotes the crude oil viscosity, μwIndicating the viscosity of the water.
7. The method of low permeability reservoir five-point well pattern transient production of claim 6, wherein the permeability k is:
k＝krw+kro
wherein k represents permeability, krwDenotes the relative permeability of the aqueous phase, kroRepresenting the relative permeability of the oil phase.
8. The low permeability reservoir five-point well pattern transient production method of claim 7,
relative permeability k of the aqueous phaserwDetermined by calculation with the Parker-Lenhard model:
relative permeability k of oil phaseroDetermined by calculation through a Brooks-Corey-Burdine model:
wherein k isrwDenotes the relative permeability of the aqueous phase, kroRepresenting the relative permeability of the oil phase; soRepresents the oil saturation; m represents a fitting parameter.
9. The method of low permeability reservoir five-point well pattern instantaneous production of claim 3, wherein in step S4, the relationship between the average saturation at time n +1 and the average saturation at time n is calculated as follows:
wherein j represents the number of the injection-production unit;
and
respectively representing the injection-production unit at time tnAnd tn+1Average saturation of lower; vφjRepresenting the pore volume of the injection-production unit; qosjIndicating injection and production unit at time tnYield in sm3/d。
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