CN106874544B - A kind of geology characterizing method of shale reservoir transformation volume - Google Patents
A kind of geology characterizing method of shale reservoir transformation volume Download PDFInfo
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Abstract
The present invention discloses a kind of geology characterizing method of shale reservoir transformation volume, comprises the following steps：Obtain every reservoir physical parameter, every rock mechanics parameters；Calculate Vital Factors B corresponding to each logging pointrit, new Vital Factors Bn, reservoir fracture toughness index Kn, intrinsic fracture open difficulty or ease indices Pn, crack pass through evaluation number Cn；Establish new evaluation points E corresponding to each log data pointn, and judge；Last Tonghua crack extension involves length Lo, involve height HoWith involve width WoObtain reservoir reconstruction volume.The beneficial effects of the present invention are：By static creation data, estimating for reservoir reconstruction volume is carried out using dynamic geological data such as well loggings, formulation and selection to well pattern arrangement and the favourable section of pressure break before pressing crack construction is realized, there is stronger practicality.
Description
Technical Field
The invention relates to a geological characterization method for a shale reservoir reconstruction volume, and belongs to the technical field of oil field development.
Background
The shale reservoir reconstruction volume (SRV) is an evaluation index for obtaining high yield of a single well, and has important significance for prediction and characterization of the reservoir reconstruction volume (SRV). Characterization and calculation methods for reservoir reconstruction volumes have been developed from qualitative to quantitative, and currently mainly include a yield fitting method, a semi-empirical formula method, a discrete network model method, a microseism monitoring method and a semi-analytical method. The yield fitting method adopts a mean model without considering the anisotropy caused by the development of natural fractures of shale reservoirsAnd single-stage capacity data cannot be obtained in a shale reservoir staged fracturing mode, so that the spread range of the single-stage fracturing SRV cannot be effectively determined. Semi-empirical formula method using tensile fracture T x 、T y Shear fracture S x 、S y And the experience constants are equal, and the differences of each horizontal well and each section of the horizontal well cannot be reflected. The discrete network model method simulates the extending process of a fracture network in a single hydraulic fracturing process by considering engineering influence factors such as fracturing fluid, proppant performance, construction pumping and injecting procedures and the like so as to determine the three-dimensional form of the SRV, but cannot consider the mutual interference effect in a multi-stage or synchronous fracturing process and cannot predict and characterize the SRV before reservoir recognition and fracturing construction. The microseism monitoring method has reliable results, but has high cost, and cannot monitor each single well in a work area. The semi-analytical method is also based on empirical constants such as anisotropic permeability k and effective porosity phi, and is lack of variability, and the diffusion coefficient needs to be calibrated by microseismic data.
The fracture network fracturing technology is used as an important means for shale reservoir transformation, and the effective shale reservoir transformation effect is achieved mainly by utilizing natural fractures in a reservoir and other rocks Dan Ruomian to open and communicate to form a complex network. The work on the aspects of reservoir fracturing performance, fracturing scale prediction and the like is focused on analysis of shale reservoir geology and mechanical characteristics of a fracturing process, and existing research at present has more aspects of lateral fracturing construction conditions, processes and the like, so that the construction process consumes a large amount of financial and material resources and possibly damages the shale reservoir due to neglect of reservoir geological analysis. And the compressibility evaluation of shale reservoirs only through geological and mechanical characteristics cannot quantitatively describe the approximate extension scale of a complex fracture network. Therefore, in order to obtain a better reconstruction effect in the fracturing construction, the complex fracture network extension scale must be predicted on the basis of reservoir compressibility evaluation, namely, the reservoir reconstruction volume is quantitatively represented through geological parameters.
The shale compressibility evaluation is mainly based on core analysis and well logging interpretation results, and comprehensive evaluation of reservoir characteristics and mechanical properties is carried out by selecting a plurality of key parameters, so that the shale compressibility evaluation is suitable for field operation, is simple and effective, and can also be combined with dynamic and static conversion of indoor experimental analysis results; and embedding continuous and reliable geological data into a rock fracture mechanics theory, eliminating the dependence of the method on a high-cost microseism monitoring method, and finally performing geological characterization on the reservoir reconstruction volume (SRV).
Disclosure of Invention
The invention aims to solve the technical problem of providing a geological characterization method of the shale reservoir reconstruction volume, which overcomes the uncertainty of a semi-analytical method empirical constant and the dependence on a microseism, enables the reconstruction degree of each single well in a research area to be quantitatively known before fracturing construction, effectively predicts the spatial distribution of the reconstruction volume and provides a reliable basis for the follow-up construction as an early-stage guidance or construction verification
The technical scheme adopted by the invention for solving the technical problems is a geological characterization method of the shale reservoir reconstruction volume, which comprises the following steps:
s100, obtaining physical property parameters of each reservoir and mechanical parameters of each rock by using the counted results of indoor experimental analysis and single-well logging interpretation of the rock core;
s200, calculating brittleness factors B corresponding to the logging data points according to the parameters obtained in the step S100 rit Novel friability factor B n ；
S300, calculating the fracture toughness index K of the reservoir corresponding to each logging data point n Natural fracture opening difficulty index P n Fracture penetration evaluation index C n ；
S400, establishing a novel evaluation factor E corresponding to each logging data point through the following formula n (ii) a When E is n &When the data point is 0.5, the logging data point is judged to be a valid data point, the next step is carried out, otherwise, the logging data point is judged to be an invalid data point;
in the formula: e n Is a novel evaluation factor;
s500, calculating the sweep length L of the crack extension of the effective data points in the step S400 o Swept height H o Sum width W o Finally, obtaining the reservoir reconstruction volume through the following formula;
in the formula: v SRV For reservoir reconstruction volume, in m 3 ；L o Is the swept length, m, H o Is the swept height in m, W o Is the sweep width, which is expressed in m, and n is the number of fracturing stages;
the specific process of step S100 is:
s101, processing the indoor experimental analysis result of the rock core to obtain the vertical depth h, the porosity phi, the density and the siliceous mineral component content V of the single well of the main power gas producing zone Si Content V of mineral component of carbonate rock Carb Rock Poisson ratio v, young' S modulus E, bulk modulus K, shear modulus G, tensile strength S t Pore pressure P p Vertical stress sigma z Horizontal maximum principal stress σ H And horizontal minimum principal stress σ h 5363 and interpreting the Shan Jingce well to obtain the uranium-free gamma, the sound wave time difference, the neutron CNL and the density rho, wherein the sound wave time difference is the transverse wave delta t s Longitudinal wave Δ t p ；
S102, obtaining porosity phi and shale content V through the following formula multivariate fitting sh ；
ρ＝a 1 +b 1 ρ log
φ log ＝a 2 +b 2 γ+c 2 Δt p +d 2 CNL+e 2 ρ log
φ＝a 3 +b 3 φ log
In the formula: rho is the static density value in g/cm 3 ，a 1 、b 1 For the density fitting parameter, p log Is a dynamic density value in g/cm 3 ，φ log Is a dynamic porosity value in units of decimal fraction, a 2 、b 2 、c 2 、d 2 、e 2 、a 3 、b 3 For porosity fitting parameters, γ is the uranium free gamma value in API, CNL is the neutron value in%, Δ t s 、Δt p The unit of the time difference is s/m of transverse wave and longitudinal wave, phi is the static porosity value, and the unit is decimal; i is Sh Normalized uranium-free gamma, gamma in API, gamma min 、γ max The minimum value and the maximum value of uranium-free gamma are measured in a whole region or a single well, the unit of the minimum value and the maximum value is API, GCUR is a formation age experience coefficient, the new formation is 3.7, and the old formation is 2;
s103, obtaining rock mechanical parameters through the following multivariate fitting;
in the formula: c ma Is the volume compressibility of the skeleton in MPa -1 ，Δt sma 、Δt pma The time difference of transverse wave and longitudinal wave of the rock skeleton can be obtained by rock core experiment, and the unit is s, rho ma Is the density of a rock skeleton and can be obtained by core experiments, and the unit of the density is kg/m 3 ，C b Is the volume compressibility, i.e. the inverse of the bulk modulus K, in MPa -1 Alpha is the effective stress coefficient, v is the Poisson's ratio, delta t s 、Δt p Is the time difference of transverse wave and longitudinal wave, and has the unit of s/m, rho is the static density value and has the unit of g/cm 3 E is Young's modulus in MPa, K is bulk modulus in MPa, and G is the second shear modulus in MPa;
P p ＝αp×gh
S t as tensile strength, it has units of MPa, V sh Is the mud content, the unit of which is percent, K is a constant and takes 12.26 as a value p Is the pore pressure in MPa, α p is the area pressure coefficient, g is the acceleration of gravity, m/s 2 H is the vertical depth in m, σ z Is the vertical principal stress in MPa, sigma H 、σ h In units of MPa, alpha is the effective stress coefficient, beta 1 、β 2 The structural stress coefficient in the direction of the horizontal maximum and minimum principal stress can be obtained by a core mechanics experiment.
Further, the specific process of step S200 is as follows: extracting data of brittle mineral components based on conventional well logging interpretation achievement, and obtaining brittle factors B corresponding to all well logging data points through the following formula rit Novel friability factor B n ；
B rit ＝E/ν
In the formula: v rit Is mineral component brittleness index, with units of% j Is the content of the j-th brittle minerals in%, B rit Is a brittleness factor, dimensionless, V min 、V max The brittleness index of the minimum and maximum mineral compositions of the whole area or single well is expressed in percent V RIT To normalize the brittle mineral content, dimensionless, B min 、B max Is the minimum and maximum brittleness factor of the whole area or single well, and is dimensionless, B RIT To normalize the brittleness factor, dimensionless, B n Is a novel brittleness factor and has no dimension.
Further, the specific process of step S300 is as follows:
s301, obtaining a fracture toughness index K of a reservoir layer through the following formula n ；
K IC ＝0.217σ n +0.0059S t 3 +0.0923S t 2 +0.517S t -0.3322
K IIC ＝0.0956σ h +0.1383S t -0.082
K RIT ＝K IC K IIC
In the formula: s t As tensile strength, it has units of MPa, K IC 、K IIC Is type I, type II fracture toughness, K RIT Is a fracture toughness factor, dimensionless, σ h Is minimum principal stress, MPa, K RITmax 、K RITmin Is a type I maximum and minimum fracture toughness factor of a whole zone or a single well, and has no dimension, K n Is fracture toughness index;
s302, acquiring natural fracture opening difficulty index P corresponding to each logging data point through the following formula n ；
In the formula: sigma n The normal stress of the wall surface of the natural crack is expressed in units of MPa, sigma z Is the vertical principal stress in MPa, sigma H 、σ h In MPa for the horizontal maximum and minimum principal stresses, psi for the natural fracture and the horizontal maximum principal stressThe included angle is measured in degrees, P is the pressure in the critical opening seam of the natural fracture, and is measured in MPa,is a unit normal vector, P, of the wall surface of the natural crack in a three-dimensional space n Is a normalized natural fracture critical opening difficulty index with the unit of MPa and P max 、P min The maximum and minimum pressure in the area or single well natural fracture Zhang Kaifeng is expressed in MPa;
s303, acquiring a crack penetration evaluation index C corresponding to each logging data point through the following formula n ；
In the formula: omega is the natural crack inclination angle, and the unit is DEG, sigma H 、σ h In units of MPa, σ, horizontal maximum and minimum principal stress n The normal stress of the wall surface of the natural crack is expressed in units of MPa and K 0 In order for the natural fracture to cross the conditioning factors,with a magnitude of τ and a direction vector ofThe shear stress vector of (a) is,size σ τ The direction vector isShear stress vector of (S) o The cohesive force of the natural fracture is expressed in MPa, u is the friction coefficient of the wall surface of the natural fracture, the coefficient is 0-1, delta is the approach angle theta between the hydraulic fracture and the natural fracture, tau is the shearing stress of the wall surface of the natural fracture, expressed in MPa, and sigma is the wall surface of the natural fracture τ The shear stress of the natural fracture wall surface under the action of the stress of the hydraulic fracture tip is expressed in MPa and C n Index is evaluated for natural fracture penetration.
Further, the specific process of step S500 is as follows:
s501, designing total liquid quantity Q and discharge quantity Q of single-section pumping construction and bottom hole pressure P according to geological characteristics of reservoir stratum of each single well i Designing the viscosity mu of the fracturing fluid, the construction time t and the fluid loss coefficient;
s502, calculating the maximum seam width w of an elliptical section in a section vertical to the seam length according to the following formula;
in the formula: w is the maximum seam width of the elliptic section, the unit is mm, p (x) is the pressure in the seam, the unit is MPa, f is the ratio of the effective thickness of the reservoir to the iterative swept height, and delta sigma is the horizontal main stress difference, the unit is MPa;
s503, establishing a pressure flow equation in the crack and the swept height H of the crack o The characterization model is as follows:
in the formula: q (x) is the flow variable in the slot, which is expressed in m 3 Mu is the viscosity of the fracturing fluid and the unit of the viscosity is mPa & s; h p Is the effective thickness of the reservoir, in m;
s504, establishing the length L of the wave sum o The fluid continuity equation of (a) is as follows:
in the formula: λ (x, t) is the fracturing fluid loss in m 3 ，t p (x) The time of fluid loss from point x is given in units of s, C x Is the fluid loss coefficient, which is expressed in m/min 0.5 A (x, t) is the fracture cross-sectional area in m 2 ；
S505, establishing a two-dimensional fracture induced stress field in the y-z direction as follows:
in the formula: sigma 1 、σ 2 、σ 3 Induced stresses in the directions of maximum, intermediate and minimum stress, in units of MPa, Δ σ o Is the horizontal induced stress difference in MPa, r is the distance from the center of the crack to the induction point A in m, r 1 The distance from the crack bottom to the induction point A is given in m, r 2 Is the distance from the crack tip to the induction point A, and has the unit of m, theta o Is the angle of the induction point A from the center of the crack, and has the unit of DEG theta 1 To induceThe angle of point A from the bottom of the crack is given in degrees θ 2 Is the angle of the induction point a from the top of the crack, in degrees;
s506, calculating the steering radius in the non-principal stress direction through an induced stress steering formula, and obtaining the sweep length L corresponding to each logging data point in the same production mode o Swept height H o Wave width W o ；
S507, obtaining the reservoir reconstruction volume through the following formula;
in the formula: v SRV For reservoir reconstruction volume, in m 3 ；L o Is the sweep length in m, H o Is the swept height in m, W o The sweep width is expressed in m, and n is the number of fracturing stages.
Compared with the prior art, the invention has the beneficial effects that: firstly, the influence of heterogeneity of stratum longitudinal and transverse continuity changes is fully considered, and data points of different geological features are verified one by one; secondly, the application of an electric measurement method with experiment or high economic consumption can be eliminated as far as possible, and the physical property and the rock mechanics basic characteristics are calculated by utilizing the conventional logging data, so that the method has wider practicability; furthermore, the feasibility of each mass point in the fracturing process is fully considered, and the defect that the compressibility of a single section in different regions cannot be considered in the conventional method is overcome; finally, by means of static production data and dynamic geological data such as well logging and the like, the reservoir transformation volume is estimated, well pattern arrangement and favorable fracturing sections are formulated and selected before fracturing construction, and the method has high practicability.
Drawings
FIG. 1 is a schematic diagram of reservoir fracturing reformation rules;
FIG. 2 is a plan view of microseismic fracture monitoring after fracturing of an example;
FIG. 3 is a three-dimensional distribution diagram of the cracks calculated in the example.
Detailed Description
The following examples are provided to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.
Taking a single-well shale reservoir from an Olympic Tao Tong Wufeng group to a certain block of a Log of the lower-mingLog of the Szechwan basin as an example;
(1) The conventional well logging interpretation results are obtained and are shown in table 1;
TABLE 1 horizontal segment segmented logging raw data
| Segmentation | Longitudinal wave time difference | Density of | Gamma without uranium | Vertical depth |
| Segment of | t p (s) | ρ(g/cm 3 ) | KTH | h(m) |
| 17 | 214.539 | 2.606 | 100.063 | 2648.597 |
| 16 | 212.987 | 2.587 | 97.299 | 2650.384 |
| 15 | 206.21 | 2.614 | 93.593 | 2649.778 |
| 14 | 208.822 | 2.586 | 87.315 | 2648.785 |
| 13 | 211.713 | 2.572 | 83.181 | 2648.656 |
| 12 | 213.806 | 2.547 | 80.07 | 2648.17 |
| 11 | 213.211 | 2.533 | 70.757 | 2647.431 |
| 10 | 215.992 | 2.515 | 69.452 | 2645.769 |
| 9 | 216.328 | 2.507 | 66.172 | 2645.216 |
| 8 | 218.421 | 2.511 | 54.8 | 2645.519 |
| 7 | 215.883 | 2.491 | 54.811 | 2643.677 |
| 6 | 212.19 | 2.521 | 57.676 | 2640.056 |
| 5 | 216.595 | 2.492 | 58.488 | 2636.624 |
| 4 | 216.487 | 2.5 | 61.063 | 2632.626 |
| 3 | 208.635 | 2.527 | 53.622 | 2628.203 |
| 2 | 216.358 | 2.5 | 70.585 | 2623.694 |
| 1 | 212.302 | 2.525 | 68.624 | 2619.715 |
(2) And (3) calculating basic physical property parameters of the reservoir, and obtaining the porosity and the content of the brittle minerals through multivariate fitting by adopting the data in the table 1 and applying the following formula. Wherein the analysis result of the core indoor experiment is processed to obtain the vertical depth h and the porosity of the single well of the main power gas production layerDensity, siliceous mineral, carbonate mineral component content V Si ，V Carb (ii) a And establishing a multivariate fitting relation by comparing with the logging data, and staticizing the dynamic data, wherein the result is shown in a table 2.
The formula is as follows: ρ = a 1 +b 1 ρ log
φ log ＝a 2 +b 2 γ+c 2 Δt p +d 2 CNL+e 2 ρ log
φ＝a 3 +b 3 φ log
In the formula: rho is the static density value in g/cm 3 ，a 1 、b 1 For the density fitting parameter, p log Is a dynamic density value in g/cm 3 ，φ log Is a dynamic porosity value in units of decimal fraction, a 2 、b 2 、c 2 、d 2 、e 2 、a 3 、b 3 For porosity fitting parameters, γ is the uranium free gamma value in API, CNL is the neutron value in%, Δ t s 、Δt p The unit of the time difference is s/m of transverse wave and longitudinal wave, phi is the static porosity value, and the unit is decimal; i is Sh Normalized uranium-free gamma, gamma in API, gamma min 、γ max The method is a total area or single well logging uranium-free gamma minimum value and maximum value, the unit of the total area or single well logging uranium-free gamma minimum value and maximum value is API, GCUR is a formation chronological empirical coefficient, 3.7 is taken for a new formation, and 2,C is taken for an old formation ma Is the volume compressibility of the skeleton in MPa -1 ，Δt sma 、Δt pma The transverse wave time difference and longitudinal wave time difference of the rock skeleton can be formed by rocksObtained by cardiac experiments and has the unit of s, rho ma Is the density of a rock skeleton and can be obtained by core experiments, and the unit of the density is kg/m 3 ，C b The volume compressibility corresponding to the ith logging data point, namely the reciprocal of the volume modulus K, and the unit of the volume compressibility is MPa -1 。
TABLE 2 horizontal section segmented logging physical property data
(3) Calculating the rock mechanical parameters, and calculating each rock mechanical parameter by using the following formula through the data in the table 1, as shown in the table 3; the method is characterized in that the acquisition cost of the transverse wave data is high, an empirical formula can be established through longitudinal wave time difference and volume density, and then the transverse wave data is matched and compared with a result of dipole acoustic logging interpretation. Processing the analysis result of the rock core indoor experiment to obtain the Poisson 'S ratio v, young' S modulus E, volume modulus K, shear modulus G and tensile strength S of the rock of the main force gas producing layer t Pore pressure P p Vertical stress sigma z Horizontal maximum principal stress σ H And horizontal minimum principal stress σ h (ii) a Using single well logging to explain the acoustic time difference and density data, and calculating rock mechanical parameters;
the formula is as follows:
in the formula: c ma Is the volume compressibility of the skeleton, MPa -1 ，Δt sma 、Δt pma The time difference of transverse wave and longitudinal wave of the rock skeleton can be obtained by rock core experiment, and the unit is s, rho ma Is the density of a rock skeleton and can be obtained by core experiments, and the unit of the density is kg/m 3 ，C b Is the volume compressibility, i.e. the inverse of the bulk modulus K, in MPa -1 Alpha is the effective stress coefficient, v is the Poisson's ratio, delta t s 、Δt p Is the time difference of transverse wave and longitudinal wave, and has the unit of s/m, rho is the static density value and has the unit of g/cm 3 E is Young's modulus in units of MPa, K is bulk modulus in units of MPa, G is shear modulus in units of MPa;
P p ＝αp×gh
in the formula: s t Is tensile strength in units ofMPa，V sh Is the mud content, the unit of which is percent, K is a constant and takes 12.26 as a value p Is the pore pressure in MPa, α p is the area pressure coefficient, g is the acceleration of gravity in m/s 2 H is the vertical depth in m, σ z Is the vertical principal stress in MPa, sigma H 、σ h In units of MPa, alpha is the effective stress coefficient, beta 1 、β 2 The structural stress coefficient in the direction of the horizontal maximum and minimum principal stress can be obtained by a core mechanics experiment.
TABLE 3 horizontal segment sectional well logging rock mechanics interpretation data
(4) Based on conventional well logging interpretation results, data of brittle mineral components are extracted, and brittleness factors B corresponding to the well logging data points are obtained through the following formula rit Novel friability factor B n ；
B rit ＝E/ν
In the formula: v rit Is mineral component brittleness index, with units of% j Is the content of the j brittle minerals in percent B rit Is a brittleness factor, dimensionless, V min 、V max The brittleness index of the minimum and maximum mineral compositions of the whole area or single well is expressed in percent V RIT To normalize the brittle mineral content, dimensionless, B min 、B max Is the minimum and maximum brittleness factor of the whole area or single well, and is dimensionless, B RIT To normalize the brittleness factor, dimensionless, B n Is a novel brittleness factor and is dimensionless.
(5) Obtaining a reservoir fracture toughness index K by n ；
K IC ＝0.217σ n +0.0059S t 3 +0.0923S t 2 +0.517S t -0.3322
K IIC ＝0.0956σ h +0.1383S t -0.082
K RIT ＝K IC K IIC
In the formula: s t As tensile strength, it has units of MPa, K IC 、K IIC Is type I, type II fracture toughness, K RIT A corresponding fracture toughness factor, dimensionless, sigma, for the ith logging data point h Is minimum principal stress, MPa, K RITmax 、K RITmin Is a type I maximum and minimum fracture toughness factor of a whole zone or a single well, and has no dimension, K n Is fracture toughness index;
(6) Acquiring natural crack opening difficulty index corresponding to each logging data point through the following formulaP n ；
In the formula: sigma n The normal stress of the wall surface of the natural crack is expressed in units of MPa, sigma z Is the vertical principal stress in MPa, sigma H 、σ h In units of MPa for the horizontal maximum and minimum principal stresses, psi for the angle between the natural fracture and the horizontal maximum principal stress in degrees, P for the internal pressure of the critical open fracture of the natural fracture in units of MPa,is a unit normal vector, P, of the wall surface of the natural crack in a three-dimensional space n Is a normalized natural fracture critical opening difficulty index with the unit of MPa and P max 、P min The maximum and minimum pressure in the area or single well natural fracture Zhang Kaifeng is expressed in MPa;
(7) Obtaining a crack penetration evaluation index C corresponding to each logging data point through the following formula n ；
In the formula: omega is the natural fracture dip angle, and the unit is DEG, sigma H 、σ h In units of MPa, σ, horizontal maximum and minimum principal stresses n The normal stress of the wall surface of the natural crack is expressed in units of MPa and K 0 In order for the natural fracture to cross the conditioning factors,with a magnitude of τ and a direction vector ofThe shear stress vector of (a) is,size σ τ The direction vector isShear stress vector of (S) o The cohesive force of the natural fracture is expressed in MPa, u is the friction coefficient of the wall surface of the natural fracture, the coefficient is 0-1, delta is the approach angle theta between the hydraulic fracture and the natural fracture, tau is the shearing stress of the wall surface of the natural fracture, expressed in MPa, and sigma is the wall surface of the natural fracture τ The shear stress of the natural fracture wall surface under the action of the stress of the hydraulic fracture tip is expressed in MPa and C n Index is evaluated for natural fracture penetration.
(8) Establishing a novel evaluation factor E corresponding to each logging data point by the following formula n (ii) a When E is n &When the data point is 0.5, judging the logging data point to be a valid data point, namely, judging that the data point has remodelability, and carrying out the next step, otherwise, judging the data point to be an invalid data point; the results are shown in Table 4:
in the formula: e n A new evaluation factor corresponding to the ith logging data point;
TABLE 4 horizontal segment sectional logging evaluation factor interpretation data
The results show that the fracturing section has better compressibility in terms of the dimension of the fracturing section.
(9) Designing total liquid quantity Q and discharge quantity Q of single-section pumping construction and bottom hole pressure P according to geological characteristics of reservoir stratum of each single well i Setting construction parameters: the fluid viscosity mu is 8 mPas, the construction time t is set to 3h, and the fluid loss coefficient is 0.00071m/min 0.5 ；
(10) Calculating the maximum seam width w of the elliptical section in the section vertical to the seam length by the following formula;
in the formula: w is the maximum seam width of the elliptical section, the unit is mm, p (x) is the pressure in the seam, the unit is MPa, f is the ratio of the effective thickness of the reservoir stratum to the iterative sum height, and delta sigma is the horizontal main stress difference, the unit is MPa;
(11) Establishing a fracture internal pressure flow equation and a fracture swept height H o The characterization model is as follows:
in the formula: q (x) is the flow variable in the slot, which is expressed in m 3 Mu is the viscosity of the fracturing fluid, and the unit is mPa & s; h p Is the effective thickness of the reservoir, in m;
(12) Establishing a sweep length L o The fluid continuity equation for (i.e., x) is as follows:
in the formula: λ (x, t) is the fracturing fluid loss in m 3 ，t p (x) The time of fluid loss from point x is given in units of s, C x Is the fluid loss coefficient, which is expressed in m/min 0.5 A (x, t) is the fracture cross-sectional area in m 2 ；
(13) Establishing a two-dimensional fracture induced stress field in the y-z direction as follows:
in the formula: sigma 1 、σ 2 、σ 3 Induced stresses in the directions of maximum, intermediate and minimum stress, in units of MPa, Δ σ o Is the horizontal induced stress difference in MPa, r is the distance from the center of the crack to the induction point A in m, r 1 The distance from the crack bottom to the induction point A is given in m, r 2 Is the distance from the crack tip to the induction point A, and has the unit of m, theta o To induce a corner of the point A which deviates from the centre of the crackDegree in degrees, θ 1 Is the angle of the induction point A from the bottom of the crack, in degrees theta 2 The angle at which the induction point a is offset from the top of the fracture is given in degrees.
(14) Calculating the steering radius in the non-principal stress direction by an induced stress steering formula so as to obtain the sweep length L corresponding to each logging data point in the same production mode o Swept height H o Wave width W o ；
(15) Finally, obtaining the reservoir reconstruction volume through the following formula; the results are shown in Table 5:
in the formula: v SRV For reservoir reconstruction volume, in m 3 ；L o Is the sweep length in m, H o Is the swept height in m, W o The sweep width is expressed in m, and n is the number of fracturing stages.
TABLE 5 geological characterization SRV calculation Table
Compared with the prior art, the invention has the beneficial effects that: firstly, the influence of heterogeneity of stratum longitudinal and transverse continuity changes is fully considered, and data points of different geological features are verified one by one; secondly, the application of an electric measurement method with experiment or high economic consumption can be eliminated as far as possible, and the physical property and the rock mechanics basic characteristics are calculated by utilizing the conventional logging data, so that the method has wider practicability; furthermore, the feasibility of each mass point in the fracturing process is fully considered, and the defect that the compressibility of a single section of different regions cannot be considered in the conventional method is overcome; finally, by means of static production data and dynamic geological data such as well logging and the like, the reservoir transformation volume is estimated, well pattern arrangement and favorable fracturing sections are formulated and selected before fracturing construction, and the method has high practicability.
Claims (4)
1. A method for geologic characterization of a shale reservoir reconstruction volume, the method comprising the steps of:
s100, obtaining physical property parameters of each reservoir and mechanical parameters of each rock by using the counted results of indoor experimental analysis and single-well logging interpretation of the rock core;
s200, calculating brittleness factors B corresponding to the logging data points according to the parameters obtained in the step S100 rit Novel friability factor B n ；
S300, calculating the fracture toughness index K of the reservoir corresponding to each logging data point n Natural fracture opening difficulty index P n Fracture penetration evaluation index C n ；
S400, establishing a novel evaluation factor E corresponding to each logging data point according to the following formula n (ii) a When E is n &When the data point is 0.5, the logging data point is judged to be a valid data point, the next step is carried out, otherwise, the logging data point is judged to be an invalid data point;
in the formula: e n Is a novel evaluation factor;
s500, calculating the swept length L of the crack propagation of the effective data points in the step S400 o Swept height H o Sum width W o Finally, obtaining the reservoir reconstruction volume through the following formula;
in the formula: v SRV For reservoir reconstruction volume, in m 3 ；L o Is the sweep length in m, H o Is the swept height in m, W o Is the sweep width, which is expressed in m, and n is the number of fracturing stages;
the specific process of step S100 is:
s101, processing the indoor experimental analysis result of the rock core to obtain the vertical depth h, the porosity phi, the density rho and the siliceous mineral component content V of the single well of the main power gas producing zone Si Content V of mineral component of carbonate rock Carb Rock Poisson ratio v, young' S modulus E, bulk modulus K, shear modulus G, tensile strength S t Pore pressure P p Vertical stress sigma z Horizontal maximum principal stress σ H And the horizontal minimum principal stress σ h 5363 and interpreting the Shan Jingce well to obtain the uranium-free gamma, the sound wave time difference, the neutron CNL and the density rho, wherein the sound wave time difference is the transverse wave delta t s Longitudinal wave Δ t p ；
S102, obtaining porosity phi and shale content V through the following formula multivariate fitting sh ；
ρ＝a 1 +b 1 ρ log
φ log ＝a 2 +b 2 γ+c 2 Δt p +d 2 CNL+e 2 ρ log
φ＝a 3 +b 3 φ log
In the formula: rho is the static density value in g/cm 3 ，a 1 、b 1 As a density fitting parameter, p log Is a dynamic density value in g/cm 3 ，φ log Is a dynamic porosity value in units of decimal fraction, a 2 、b 2 、c 2 、d 2 、e 2 、a 3 、b 3 For porosity fitting parameters, γ is the uranium free gamma value in API, CNL is the neutron value in%, Δ t s 、Δt p Is the time difference of transverse wave and longitudinal wave, and the unit is sM, phi is the static porosity value in decimals; i is Sh To normalize the uranium-free gamma value, gamma min 、γ max The minimum value and the maximum value of uranium-free gamma in whole-zone or single-well logging are determined, the unit is API, GCUR is the age experience coefficient of the stratum, the new stratum is 3.7, and the old stratum is 2;
s103, obtaining rock mechanical parameters through the following multivariate fitting;
in the formula: c ma Is the volume compressibility of the skeleton in MPa -1 ，Δt sma 、Δt pma The time difference of transverse wave and longitudinal wave of the rock skeleton can be obtained by rock core experiment, and the unit is s, rho ma Is the density of a rock skeleton and can be obtained by core experiments, and the unit of the density is kg/m 3 ，C b Is the volume compressibility, i.e. the inverse of the bulk modulus K, in MPa -1 Alpha is the effective stress coefficient, v is the Poisson's ratio, delta t s 、Δt p Is the time difference of transverse wave and longitudinal wave, and has the unit of s/m, rho is the static density value and has the unit of g/cm 3 E is Young's modulus in MPa, K is bulk modulus in MPa, G is shear modulus in MPa;
P p ＝αp×gh
in the formula: s t As tensile strength, it has units of MPa, V sh Is the mud content, the unit of which is percent, K is a constant and takes 12.26 as a value p Is the pore pressure in MPa, α p is the area pressure coefficient, g is the acceleration of gravity in m/s 2 H is the vertical depth in m, σ z Is the vertical principal stress in MPa, sigma H 、σ h In units of MPa, alpha is the effective stress coefficient, beta 1 、β 2 The structural stress coefficient in the direction of the horizontal maximum and minimum principal stress can be obtained by a core mechanics experiment.
2. The method for geologic characterization of a shale reservoir reconstruction volume of claim 1, wherein the specific process of step S200 is: extracting data of brittle mineral components based on conventional well logging interpretation achievement, and obtaining brittle factors B corresponding to all well logging data points through the following formula rit Novel friability factor B n ；
B rit ＝E/ν
In the formula: v rit Is mineral component brittleness index, with units of% j Is the content of the j-th brittle minerals in%, B rit Is a brittleness factor, dimensionless, V min 、V max The brittleness index of the minimum and maximum mineral compositions of the whole area or single well is expressed in percent V RIT To normalize the brittle mineral content, dimensionless, B min 、B max Is the minimum and maximum brittleness factor of the whole area or single well, and is dimensionless, B RIT To normalize the brittleness factor, dimensionless, B n Is a novel brittleness factor and has no dimension.
3. The method for geologic characterization of a shale reservoir reconstruction volume of claim 2, wherein the specific process of step S300 is:
s301, obtaining a fracture toughness index K of a reservoir layer through the following formula n ；
K IC ＝0.217σ n +0.0059S t 3 +0.0923S t 2 +0.517S t -0.3322
K IIC ＝0.0956σ h +0.1383S t -0.082
K RIT ＝K IC K IIC
In the formula: s. the t As tensile strength, it has units of MPa, K IC 、K IIC Is type I, type II fracture toughness, K RIT Is a fracture toughness factor, dimensionless, σ h Is minimum principal stress, MPa, K RITmax 、K RITmin Is a type I maximum and minimum fracture toughness factor of a whole area or a single well, and has no dimension, K n Is fracture toughness index;
s302, acquiring natural crack opening difficulty index P corresponding to each logging data point through the following formula n ；
In the formula: sigma n The normal stress of the wall surface of the natural crack is expressed in units of MPa, sigma z Is the vertical principal stress in MPa, sigma H 、σ h In units of MPa for the horizontal maximum and minimum principal stresses, psi for the angle between the natural fracture and the horizontal maximum principal stress in units of degrees, P for the internal pressure of the critical open fracture of the natural fracture in units of MPa,is a unit normal vector, P, of the wall surface of the natural crack in a three-dimensional space n Is the index of the natural fracture critical opening difficulty and easiness, and the unit of the index is MPa and P max 、P min Is the maximum and minimum pressure in the area or single well natural fracture Zhang Kaifeng, and the unit is MPa;
s303, obtaining each test through the following formulaEvaluation index C for fracture penetration corresponding to well data points n ；
In the formula: omega is the natural fracture dip angle, and the unit is DEG, sigma H 、σ h In units of MPa, σ, horizontal maximum and minimum principal stresses n The normal stress of the wall surface of the natural crack is expressed in units of MPa and K 0 In order for the natural fracture to cross the conditioning factors,with a magnitude of τ and a direction vector ofThe shear stress vector of (a) is,size σ τ The direction vector isShear stress vector of S o The cohesive force of the natural fracture is expressed in MPa, u is the wall friction coefficient of the natural fracture, the value range is 0-1, delta is the approach angle theta between the hydraulic fracture and the natural fracture, tau is the wall shear stress of the natural fracture and expressed in MPa，σ τ The shear stress of the natural fracture wall surface under the action of the stress of the hydraulic fracture tip is expressed in MPa and C n Index is evaluated for natural fracture penetration.
4. The method for geologic characterization of a shale reservoir reconstruction volume of claim 3, wherein the specific process of step S500 is:
s501, designing total liquid quantity Q and discharge quantity Q of single-section pumping construction and bottom hole pressure P according to geological characteristics of each single-well reservoir i Designing the viscosity mu of the fracturing fluid, the construction time t and the fluid loss coefficient;
s502, calculating the maximum seam width w of an elliptical section in a section vertical to the seam length according to the following formula;
in the formula: w is the maximum seam width of the elliptic section, the unit is mm, p (x) is the pressure in the seam, the unit is MPa, f is the ratio of the effective thickness of the reservoir to the iterative sweep height, and delta sigma is the horizontal main stress difference, the unit is MPa;
s503, establishing a fracture internal pressure flow equation and a fracture swept height H o The characterization model is as follows:
in the formula: q (x) is the flow variable in the slot, which is expressed in m 3 Mu is the viscosity of the fracturing fluid and the unit of the viscosity is mPa & s; h p Is the effective thickness of the reservoir, in m;
s504, establishing a sweep length L o The fluid continuity equation of (a) is as follows:
in the formula: λ (x, t) is the fracturing fluid loss in m 3 ，t p (x) The time of fluid loss from point x is given in units of s, C x Is the fluid loss coefficient, which is expressed in m/min 0.5 A (x, t) is the fracture cross-sectional area in m 2 ；
S505, establishing a two-dimensional fracture induced stress field in the y-z direction as follows:
in the formula: sigma 1 、σ 2 、σ 3 Induced stresses in the directions of maximum, intermediate and minimum stress, in units of MPa, Δ σ o Is the horizontal induced stress difference in MPa, r is the distance from the center of the crack to the induction point A in m, r 1 The distance from the crack bottom to the induction point A is given in m, r 2 The distance from the crack top to the induction point A is expressed in m, theta o Is the angle of the induction point A from the center of the crack, and has the unit of DEG theta 1 Is the angle of the induction point A from the bottom of the crack, in degrees theta 2 Is the angle of the induction point a from the top of the crack, in degrees;
s506, calculating the steering radius in the non-principal stress direction through an induced stress steering formula, and obtaining the sweep length L corresponding to each logging data point in the same production mode o Swept height H o Wave width W o ；
S507, obtaining the reservoir reconstruction volume through the following formula;
in the formula: v SRV For reservoir reconstruction volume, in m 3 ；L o Is the swept length in m, H o Is the swept height in m, W o The sweep width is expressed in m, and n is the number of fracturing stages.
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