CN111241665A - Fracturing reconstruction zone permeability model establishing method - Google Patents
Fracturing reconstruction zone permeability model establishing method Download PDFInfo
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Abstract
The invention provides a fracturing reconstruction zone permeability model establishing method, which comprises the following steps: step 1, determining the shape and the range of a fracturing modification area by analyzing and processing an original micro-seismic point diagram; step 2, calculating the distribution density of the micro-seismic points in each fracturing modification area according to the division result of the fracturing modification area; step 3, verifying the rationality of the fracturing modification area division method; and 4, obtaining the permeability of each fracturing reconstruction area through inversion. The method for establishing the permeability model of the fracturing transformation area creatively provides a method for dividing the fracturing transformation area by using the distribution rule of isobars around a horizontal well, scientifically and accurately effectively processes the distribution of micro-seismic points, establishes a corresponding permeability model, and provides a key technical means for researching the seepage rule of the oil reservoir in future.
Description
Technical Field
The invention relates to the technical field of oilfield development, in particular to a method for establishing a permeability model of a fracturing modification area.
Background
The layered conglomerate oil reservoir belongs to a low-porosity and ultra-low-permeability reservoir, has insufficient natural energy, lower natural productivity and quicker decline of productivity, and needs fracturing and production. In the fracturing development process, micro-fractures can be formed in a reservoir, a micro-fracture development area is called a fracturing modification area, and the range and the seepage characteristics of the micro-fractures directly determine the capacity of the oil reservoir. Therefore, the permeability model is established for the fracturing transformation area, and the method has important significance for guiding the development of the oil reservoir.
Microseism monitoring is an important means for understanding reservoir fracturing development effect, and acquired microseism signals can be used for analyzing underground states and predicting the spatial distribution of fractures. Due to the disordered distribution of the micro-seismic points in the reservoir, although a lot of researches have been carried out by the predecessors, the distribution rule of the micro-seismic points is not reasonably explained so far, so that the analysis of the influence of the micro-seismic points on the seepage rule becomes a difficult point.
In the application No.: 201610810941.0, relates to a method and a device for reconstructing a fracturing network based on a microseism, belonging to the technical field of oil exploitation, the method for reconstructing the fracturing network comprises the following steps: carrying out primary processing on data of the micro-seismic monitoring points in the hydraulic fracturing process; respectively taking the starting point of each fracturing segment as a starting point, and carrying out iterative reconstruction to obtain a fracturing network N of each fracturing segment; calculating the permeability k of each fracturing section in the fracturing network N; merging the fracture networks N of all the fracture sections, establishing a discrete fracture grid model, carrying out production numerical simulation, and carrying out production history fitting on the obtained production numerical simulation value and an actual production numerical value; and solving an accumulated distribution function of the pressure values of all the points of the oil reservoir, taking the inflection point of the accumulated distribution function as the boundary pressure of the reservoir modification volume, and drawing a contour map to obtain the shape and the range of the reservoir modification volume generated by the fracturing. Firstly, the premise of realizing the reconstruction of the fracture network in the patent is that parameters such as rock cracking points, cracking time, cracking energy and the like are obtained by utilizing seismic wave data inversion, and the method is not suitable for the condition that microseismic data provided on site are not complete. Secondly, the patent does not give reasonable explanation to the distribution rule of the micro-seismic points around the vertical fracture, and although the shape and the range of the fracturing modification area are determined by establishing a discrete fracture network model for fitting, the division problem of the fracturing modification area is not simplified and solved by effectively utilizing the distribution of the micro-seismic points, so that the division process is very complicated. Finally, the fracturing network in the patent contains a plurality of fracturing sections, trial calculation amount is increased by combining the fracturing sections to carry out permeability iterative correction, and the fracturing network is difficult to represent in numerical simulation software, so that the complexity of permeability correction is increased. In conclusion, the application range of the patent is narrow, the operation process is complex, and the calculation amount is large, so that the patent is not easy to popularize.
In the application No.: 201710006652.X, which is a Chinese patent application, relates to a method for calculating a compact reservoir fracturing modification volume area, which comprises the following steps: establishing a non-planar steering extension model, a stratum stress field change model, a reservoir pressure field change model and a natural fracture failure criterion of a plurality of hydraulic fractures in the fracturing process of a compact reservoir horizontal well, acquiring geological parameters, horizontal well fracturing construction parameters and total fracturing time, assigning initial values of fracture filtration loss, fracture half-length, pressure in a fracture, initial values of initial fracture extension steering angles, initial permeability and initial values of fracturing time, solving each model, and calculating to obtain coordinate data of natural fracture failure points; and respectively calculating the volume of the tensile failure reconstruction area and the volume of the shear failure reconstruction area in the reservoir by using a space numerical integration method, and integrating the spaces of the tensile failure reconstruction area and the shear failure reconstruction area into a total reconstruction volume area. First, the patent can be utilized to calculate a fracture modification volume when natural fractures are present in the reservoir and all of the underlying parameters are known, otherwise the patent will no longer work. Secondly, a plurality of physical change processes during staged fracturing of the horizontal well are considered, the mutual coupling effect among the physical change processes not only increases the complexity of calculation, but also puts higher requirements on the accuracy of basic parameters, and otherwise, the calculation precision of the fracturing modification volume area is influenced. Finally, the patent does not give a reasonable explanation for the distribution rule of the microseismic points around the vertical cracks. Therefore, the application range of the patent is small, the calculation process is complex, and the popularization difficulty is large.
Therefore, a new fracturing reconstruction zone permeability model establishing method is invented, and the technical problems are solved.
Disclosure of Invention
The invention aims to provide a fracturing transformation area permeability model building method which utilizes the distribution rule of isobars around a horizontal well to realize the division of a fracturing transformation area and completes the building of a permeability model according to the distribution density of micro-seismic points in the fracturing transformation area.
The object of the invention can be achieved by the following technical measures: the method for establishing the permeability model of the fracturing modification area comprises the following steps: step 1, determining the shape and the range of a fracturing modification area by analyzing and processing an original micro-seismic point diagram; step 2, calculating the distribution density of the micro-seismic points in each fracturing modification area according to the division result of the fracturing modification area; step 3, verifying the rationality of the fracturing modification area division method; and 4, obtaining the permeability of each fracturing reconstruction area through inversion.
The object of the invention can also be achieved by the following technical measures:
in the step 1, regarding the main crack as a horizontal well, dividing a fracturing transformation area, namely an elliptical ring, by using isobars distributed around the horizontal well, and reasonably wrapping micro-seismic points in the elliptical ring according to the change rule of the distribution density of the micro-seismic points; the shape of each transformation area from inside to outside is gradually changed from an ellipse to a circle; the fracture modification zone seepage capability closer to the main fracture is stronger, and the seepage capability of the fracture modification zone becomes weaker along with the extension to the periphery of the reservoir until the fracture modification zone becomes a pure matrix zone.
In step 2, calculating the distribution density of the micro-seismic points in each fracturing transformation area according to the division result of the fracturing transformation area, wherein the distribution density is in direct proportion to the seepage capacity formed by the micro-cracks in the fracturing transformation area.
In step 2, firstly, the number T of microseismic points in each elliptical ring, namely the fracturing transformation area is calculatedi(ii) a Next, the area S of each elliptical ring is calculatedi(ii) a Finally, the distribution density rho of the microseismic points in each elliptical ring is obtainedi＝Ti/Si。
In step 3, with the fracturing modification area closest to the main fracture, namely 1 area, as a reference, the permeability formed by the microcracks in each fracturing modification area and the multiple of the area of each fracturing modification area increased compared with that of the fracturing modification area 1 are sequentially calculated, namely K is calculatedi’/K1’＝ρi/ρ1And Si/S1；
In the formula: ki' -permeability of microfracture formation in fracture modification i zone, i ═ 1, 2, 3, 4, 5; k1' -permeability of microfracture formation in zone 1 of fracture modification; rhoiThe i area micro-seismic points are transformed by fracturing to distribute density; rho1The distribution density of microseismic points of the area 1 is reconstructed by fracturing; si-fracturing to modify the area of zone i; s1-fracture reforming zone 1 area;
then fitting permeability increase factor K for microcrack formation in fracture transformation zonei’/K1' area increase multiple S along with fracturing reconstruction zonei/S1And the permeability K for forming microcracks in each fracture transformation areai' and K1The relationship between' is represented by the relation
Coming watchShown in the specification;
Ki' -fracture modifying permeability for microfracture formation in zone i;
since the overall permeability of the fracture modification zone is equal to the sum of the permeability of the microcrack formation and the matrix permeability, i.e., Ki＝Ki'+KmAnd then the permeability of each fracture transformation area is as follows:
in the formula: ki-fracturing to modify zone i permeability; k1' -permeability of microfracture formation in zone 1 of fracture modification; si-fracturing to modify the area of zone i; s1-fracture reforming zone 1 area; km-permeability of the matrix.
In step 4, a numerical simulation model is established according to the actual condition of the oil reservoir and the fracturing reconstruction zone division result, and the permeability of each fracturing reconstruction zone is obtained by utilizing the inversion of the oil reservoir historical production data.
According to the method for establishing the permeability model of the fracturing modification area, the fracturing modification area is innovatively divided by using the distribution rule of isobars around the horizontal well according to the horizontal well development simulation characteristic that vertical long cracks are formed by vertical well fracturing, the distribution of microseismic points is scientifically and accurately effectively treated, the corresponding permeability model is established, and a key technical means is provided for researching the seepage rule of the oil reservoir in the future.
The invention provides a set of technical method, which can make up the defects of the prior art and describe the vertical well fracturing transformation area more scientifically and accurately; the range of the fracturing modification area is divided by imitating isobars distributed around a horizontal well, so that the accurate description of the fracturing modification area is realized; the distribution density of the micro-seismic points in each fracturing modification area is calculated, so that the quantitative representation of the seepage capability of the fracturing modification area is realized; aiming at establishing a permeability model of a fracturing reconstruction zone, a simple, specific and operable technical method and implementation steps are provided; the method is not only suitable for the development of the layered conglomerate oil reservoir, but also can provide reference for the research of other low-porosity and low-permeability oil reservoirs.
Drawings
FIG. 1 is a schematic illustration of a fracture reconstruction zone in an embodiment of the present invention;
fig. 2 is a schematic diagram of verification results of a fracturing rebuild zone partitioning method in an embodiment of the present invention;
FIG. 3 is a schematic view of a single well numerical model in accordance with an embodiment of the present invention;
FIG. 4 is a graphical representation of daily fluid fit results in an embodiment of the present invention;
FIG. 5 is a schematic illustration of a cumulative fluid fit result in an embodiment of the present invention;
fig. 6 is a flowchart of a method for establishing a permeability model of a fracture modification zone according to an embodiment of the present invention.
Detailed Description
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
As shown in fig. 6, fig. 6 is a flowchart of a fracture-modified zone permeability model building method according to the present invention.
And determining the shape and the range of the fracture transformation area by analyzing and processing the original micro-seismic point diagram. As shown in the attached figure 1, from the main fracture to the periphery of the reservoir, the distribution of microseismic points (each microseismic point represents a micro fracture) is changed from dense to sparse, namely, the seepage capability is changed from strong to weak. Through observation and test, the main crack is regarded as a horizontal well, the isolines distributed around the horizontal well are used for dividing a fracturing modification area (an elliptical ring), and the micro-seismic points can be reasonably wrapped inside the elliptical ring according to the change rule of the distribution density of the micro-seismic points. The shapes of the transformation areas from inside to outside are gradually changed from an ellipse to a circle. The fracture modification zone seepage capability closer to the main fracture is stronger, and the seepage capability of the fracture modification zone becomes weaker along with the extension to the periphery of the reservoir until the fracture modification zone becomes a pure matrix zone.
And 102, calculating the distribution density of the micro-seismic points in each fracture transformation area.
And calculating the distribution density of the micro-seismic points in each fracturing transformation area according to the division result of the fracturing transformation area, wherein the distribution density is in direct proportion to the seepage capacity formed by the micro-cracks in the fracturing transformation area. Firstly, calculating the number T of microseismic points in each elliptical ring (namely a fracturing transformation area)i(ii) a Next, the area S of each elliptical ring is calculatedi(ii) a Finally, the distribution density rho of the microseismic points in each elliptical ring is obtainedi＝Ti/Si. The specific calculation results are shown in the attached table 1.
TABLE 1 table of calculation results of relevant parameters
And 103, verifying the rationality of the fracturing modification area division method.
As shown in the attached table 1, with the fracturing modification area (1 area) closest to the main crack as a reference, the permeability of the formation of the microcracks in each fracturing modification area and the times of the area of each fracturing modification area increased compared with that of the fracturing modification area 1 are sequentially calculated, namely K is calculatedi’/K1’＝ρi/ρ1And Si/S1. Then fitting permeability increase factor K for microcrack formation in fracture transformation zonei’/K1' area increase multiple S along with fracturing reconstruction zonei/S1Can be seen from the variation trend of (see fig. 3), the error R2Very close to 1, which shows that the method is very reasonable for dividing the fracturing transformation area and the permeability K for forming the microcracks in each fracturing transformation areai' and K1The relationship between' can be represented by a relational expression
To indicate. Since the overall permeability of the fracture modification zone is equal to the sum of the permeability of the microcrack formation and the matrix permeability, i.e., Ki＝Ki'+KmAnd then the permeability of each fracture transformation area is as follows:
and 104, performing inversion to obtain the permeability of each fracture transformation area.
And establishing a numerical simulation model according to the actual condition of the oil reservoir and the partitioning result of the fracturing reconstruction area, and obtaining the permeability of each fracturing reconstruction area by utilizing the inversion of the historical production data of the oil reservoir, wherein the result reflects the seepage characteristic of the real reservoir.
In an embodiment of the present invention, the main fractures and the fracture transformation zones in fig. 1 are taken as examples, the vertical main fracture parameters are shown in table 2, and the fracture transformation zones are divided as shown in fig. 1.
TABLE 2 vertical Main crack parameter Table
A single well numerical model was first constructed along the direction of propagation of the primary fracture using the matrix parameters in the attached table 3, as shown in figure 3.
TABLE 3 matrix parameters Table
And then designing 10 parameter combination schemes related to three factors of the flow conductivity of the main fracture, the permeability of the fracturing modification 1 zone and the compression coefficient of the main fracture, wherein the permeability of the fracturing modification 2 zone-5 zone can be obtained by calculation according to a fitting formula (1), and a scheme design list is shown in an attached table 4.
TABLE 4 scheme design List
Finally, the 10 scheme results are used for fitting the historical production data of the oil reservoir to obtain a daily fluid production fitting result shown in the figure 4 and a cumulative fluid production fitting node shown in the figure 5And (5) fruit. It can be seen that the fitting effect of the scheme 8 is the best, namely the inversion obtains that the flow conductivity of the main crack is 14D-cm, and the compression coefficient of the main crack is 0.001MPa-1And the permeability of the fracturing reconstruction 1 area is K1The permeability of each of the remaining fracture-modified zones can be determined from formula (1) when the value is 1.95 mD.
Claims (6)
1. The method for establishing the permeability model of the fracturing modification area is characterized by comprising the following steps of:
step 1, determining the shape and the range of a fracturing modification area by analyzing and processing an original micro-seismic point diagram;
step 2, calculating the distribution density of the micro-seismic points in each fracturing modification area according to the division result of the fracturing modification area;
step 3, verifying the rationality of the fracturing modification area division method;
and 4, obtaining the permeability of each fracturing reconstruction area through inversion.
2. The method for establishing the permeability model of the fracturing transformation area according to claim 1, wherein in the step 1, a main crack is regarded as a horizontal well, isobars distributed around the horizontal well are used for dividing the fracturing transformation area, namely an elliptical ring, and microseismic points are reasonably wrapped inside the elliptical ring according to the change rule of the distribution density of the microseismic points; the shape of each transformation area from inside to outside is gradually changed from an ellipse to a circle; the fracture modification zone seepage capability closer to the main fracture is stronger, and the seepage capability of the fracture modification zone becomes weaker along with the extension to the periphery of the reservoir until the fracture modification zone becomes a pure matrix zone.
3. The method for establishing the permeability model of the fracturing modification area according to claim 1, wherein in the step 2, the distribution density of the micro-shock points in each fracturing modification area is calculated according to the division result of the fracturing modification area, and the distribution density is in direct proportion to the seepage capability formed by the micro-cracks in the fracturing modification area.
4. The fracture modification zone permeability module of claim 3The method for establishing the fracture is characterized in that in the step 2, firstly, the number T of microseismic points in each elliptical ring, namely a fracture transformation area is calculatedi(ii) a Next, the area S of each elliptical ring is calculatedi(ii) a Finally, the distribution density rho of the microseismic points in each elliptical ring is obtainedi＝Ti/Si。
5. The method for establishing a permeability model of a fracturing modification area according to claim 1, wherein in step 3, based on the fracturing modification area closest to the main fracture, namely 1 area, the permeability of the microcrack formation in each fracturing modification area and the multiple of the area of each fracturing modification area increased compared with that of the fracturing modification area 1 area are sequentially calculated, namely K is calculatedi’/K1’＝ρi/ρ1And Si/S1；
In the formula: ki' -permeability of microfracture formation in fracture modification i zone, i ═ 1, 2, 3, 4, 5; k1' -permeability of microfracture formation in zone 1 of fracture modification; rhoiThe i area micro-seismic points are transformed by fracturing to distribute density; rho1The distribution density of microseismic points of the area 1 is reconstructed by fracturing; si-fracturing to modify the area of zone i; s1-fracture reforming zone 1 area;
then fitting permeability increase factor K for microcrack formation in fracture transformation zonei’/K1' area increase multiple S along with fracturing reconstruction zonei/S1And the permeability K for forming microcracks in each fracture transformation areai' and K1The relationship between' is represented by the relation
To represent;
Ki' -fracture modifying permeability for microfracture formation in zone i;
since the overall permeability of the fracture modification zone is equal to the sum of the permeability of the microcrack formation and the matrix permeability, i.e., Ki＝Ki'+KmAnd then the permeability of each fracture transformation area is as follows:
in the formula: ki-fracturing to modify zone i permeability; k1' -permeability of microfracture formation in zone 1 of fracture modification; si-fracturing to modify the area of zone i; s1-fracture reforming zone 1 area; km-permeability of the matrix.
6. The method for establishing the permeability model of the fracturing reconstruction zone according to claim 1, wherein in step 4, a numerical simulation model is established according to the actual condition of the oil reservoir and the partitioning result of the fracturing reconstruction zone, and the permeability of each fracturing reconstruction zone is obtained by utilizing the inversion of the historical production data of the oil reservoir.
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| CN116629165A (en) * | 2023-07-24 | 2023-08-22 | 中国石油大学(华东) | Reservoir fracturing reconstruction area and non-reconstruction area parameter inversion method, system and equipment |
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| CN116629165A (en) * | 2023-07-24 | 2023-08-22 | 中国石油大学(华东) | Reservoir fracturing reconstruction area and non-reconstruction area parameter inversion method, system and equipment |
| CN116629165B (en) * | 2023-07-24 | 2023-09-22 | 中国石油大学(华东) | Reservoir fracturing reconstruction area and non-reconstruction area parameter inversion method, system and equipment |
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