阅读说明：本技术 一种定量评价页岩气甜点的方法 (Method for quantitatively evaluating shale gas dessert ) 是由 胡东风 王明飞 蒲勇 刘若冰 缪志伟 张新 孙均 苏建龙 于 2018-08-06 设计创作，主要内容包括：公开了一种页岩气甜点的方法。该方法包括：根据基础地质数据、测井数据及地震资料确定地质敏感甜点参数和工程甜点参数；基于确认的地质敏感甜点参数和工程甜点参数,开展地球物理预测,获得预测成果；建立页岩气甜点定量评价模型Q；确定页岩气甜点定量评价因子Q<Sub>sweet</Sub>；根据评价因子Q<Sub>sweet</Sub>的数值范围判定页岩气有利勘探区。本发明通过建立甜点定量评价模型,可完成构造复杂区页岩气甜点综合评价,优选富集高产带,助力高效勘探开发。(A method of shale gas dessert is disclosed. The method comprises the following steps: determining geology sensitive dessert parameters and engineering dessert parameters according to the basic geological data, the logging data and the seismic data; carrying out geophysical prediction based on the confirmed geological sensitive dessert parameters and the engineering dessert parameters to obtain a prediction result; establishing a shale gas dessert quantitative evaluation model Q; determination of quantitative evaluation factor Q of shale gas dessert sweet (ii) a According to the evaluation factor Q sweet The value range of (2) determines that the shale gas is beneficial to exploration areas. According to the invention, by establishing the dessert quantitative evaluation model, the shale gas dessert comprehensive evaluation in the complex-structure area can be completed, the enriched high-yield zone is preferably selected, and the efficient exploration and development are assisted.)

1. A method for quantitatively evaluating shale gas desserts, comprising:

1) determining geology sensitive dessert parameters and engineering dessert parameters according to the basic geological data, the logging data and the seismic data;

2) carrying out geophysical prediction based on the geology sensitive dessert parameters and the engineering dessert parameters confirmed in the step 1) to obtain a prediction result;

3) establishing a shale gas dessert quantitative evaluation model Q based on the prediction result obtained in the step 2);

4) determining a quantitative evaluation factor Q of the shale gas dessert based on the quantitative evaluation model Q in the step 3)_sweet；

5) According to the evaluation factor Q_sweetThe value range of (2) determines that the shale gas is beneficial to exploration areas.

2. The method for quantitatively evaluating shale gas desserts according to claim 1, wherein in step 2) the geophysical prediction comprises:

2-1) TOC seismic prediction based on high-precision prestack density inversion;

2-2) post-stack seismic porosity prediction based on good correlation of post-stack wave impedance and porosity;

2-3) brittle index prestack seismic predictions based on multiparameters λ ρ, μ ρ, E, σ, where λ is the lame coefficient, μ is the shear modulus, ρ is the formation density, σ is the poisson ratio, and E is the young's modulus;

2-4) post-stack seismic fracture prediction based on high precision body curvature.

3. The method for quantitatively evaluating the shale gas sweet spot according to claim 1, wherein in the step 3), a shale gas sweet spot quantitative evaluation model Q is established by the following formula:

Q＝G(x₁,x₂,x₃…x_n)/B(a₁,a₂,a₃…a_n) (1)

wherein, G (x)₁,x₂,x₃…x_n) Dessert parameter x for positive preservation of shale gas enrichment₁,x₂,x₃…x_nProduct of (a), B (a)₁,a₂,a₃…a_n) Is a shaleGas enrichment preservation of disruptive dessert parameters a₁,a₂,a₃…a_nThe product of (a).

4. The method for quantitatively evaluating shale gas dessert according to claim 1, wherein in step 4), the shale gas dessert quantitative evaluation factor Q is determined by the following formula_sweet：

Q_sweet＝Normalize(Q) (2) 。

5. The method for quantitatively evaluating shale gas dessert of claim 1, wherein in step 1), the geologically sensitive dessert parameters include: total organic carbon content TOC, porosity phi, pressure coefficient PC, total gas content Cz and roof crack density Frc.

6. The method for quantitatively evaluating shale gas dessert of claim 1, wherein in step 1), the engineered dessert parameters include friability index, BRT, and horizontal ground stress difference.

7. The method for quantitatively evaluating shale gas desserts according to claim 4, wherein the parameters that positively contribute to shale gas enrichment preservation comprise: total organic carbon content TOC, brittleness index BRT, pressure coefficient PC and porosity Φ.

8. The method for quantitatively evaluating shale gas desserts according to claim 4, wherein the parameters that disrupt shale gas enrichment preservation comprise: top plate crack density Frc.

9. The method for quantitatively evaluating shale gas desserts according to claim 3, wherein in step 1-1), the TOC prediction model is established by the following formula:

TOC＝aρ+b (3)

wherein a and b are regional empirical constants, and rho is the formation density.

10. The method for quantitatively evaluating shale gas sweet spots as claimed in claim 1, wherein in step 5), the evaluation factor Q of favorable exploration areas of shale gas is determined_sweetThe numerical ranges of (A) are: q_sweet∈(0，0.3]Three types of dessert regions, Q_sweet∈(0.3，0.6]Being a type II dessert region, Q_sweet∈(0.6，1]Is a dessert area, wherein one dessert area and the second dessert area are favorable exploration areas of shale gas.

Technical Field

The invention relates to the technical field of oil and gas exploration, in particular to a method for quantitatively evaluating shale gas desserts.

Background

Shale gas belongs to unconventional natural gas, is mainly in adsorption and free states and exists in stratums such as shale and shale with hydrocarbon generation capacity, and has the characteristics of self-generation and self-storage, adsorption and formation, hidden aggregation, low porosity, low permeability and the like. The shale is greatly different from a conventional reservoir in mineral composition, rock physical properties and seepage characteristics, so that the traditional reservoir evaluation method is not completely applicable to a shale gas layer, and evaluation contents are different to a certain extent. Exploration practice proves that the shale gas reservoir shows strong heterogeneity in the longitudinal direction and the transverse direction, and a local high-yield enrichment area exists. At present, the most main factors for predicting and evaluating the shale gas dessert at home and abroad comprise 6 aspects such as total organic carbon content (TOC), vitrinite reflectivity, porosity, brittleness index, permeability, free gas, adsorbed gas, pore pressure and the like. Treadgold and Treadgold are used for shale TOC prediction by using seismic data

The TOC prediction is realized based on the inversion result of the longitudinal wave impedance by respectively utilizing the nonlinear negative correlation relationship between the longitudinal wave impedance and the TOC, and the Chen Zuiqing proposes a method for directly predicting the TOC by utilizing prestack simultaneous inversion to predict the density body, so that the error accumulation caused by the fact that the TOC is predicted by utilizing attributes for multiple times of calculation is avoided, and a good application effect is obtained; in the process of predicting and researching the pressure coefficient of the marine shale gas formation in the south-east-Chuanlong area, the Dryobo et al finds that the traditional pressure prediction methods such as the Filloptone formula, the equivalent depth method, the Eaton and the effective stress method are not suitable for the area, and the suitable pressure coefficient formula is summarized by improving the Filloptone formula, so that a good prediction effect is obtained; the chember, the mu rho, the E and the sigma are comprehensively used by Chenzuqing and the like to determine the brittleness of the rock,a new compressibility prediction model is established, prediction of a high-quality shale fracturing quality area is achieved, a multivariate calculation model between mineral composition brittleness index and elastic parameters (lambda rho, mu rho, E and sigma) is established through optimization of rock brittleness elastic parameters, a brittleness index calculation method for predicting by using seismic elastic parameters is provided, and high calculation accuracy is obtained. An SPE article in 2014 of Ahmed oiles proposes a Shale Capacity (SC) concept, and the TOC, the porosity, the brittleness index and the fracture density of the Shale gas reservoir are multiplied to establish an SC evaluation model for evaluating the Shale gas reservoir, so that a good effect is achieved. In general, the following two problems mainly exist in related research at home and abroad:

(1) for shale gas dessert parameter evaluation, geophysical prediction is taken as a main part, the research is deeper, geological dessert prediction technology comprises TOC, pressure coefficient, gas content prediction and the like, engineering dessert prediction technology comprises brittleness index prediction and the like, and a dessert evaluation system combining geology and engineering is not complete;

(2) compared with the North America shale gas field, the enrichment and preservation of the sea-phase shale gas in south China are controlled by preservation conditions, so that in the process of carrying out comprehensive evaluation on the shale gas dessert, the pressure coefficient representing the preservation conditions and the shale gas layer top plate crack development density are not introduced into the existing shale gas dessert quantitative evaluation model according to the quantitative standard. Therefore, there is a need to develop a method for quantitatively evaluating shale gas desserts.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

The invention provides a method for quantitatively evaluating shale gas sweet spots, which introduces the influence of the development density of a top plate crack on the storage condition of shale gas and the enrichment high yield on the basis of controlling the optimization of key sweet spot parameters for shale gas enrichment storage and on the basis of geophysical prediction results of geological sweet spots (TOC, pressure coefficient, porosity and the like) and engineering sweet spots (brittleness index and the like), develops an enrichment high-yield zone evaluation method and quantitative evaluation model research, establishes a shale gas geology and engineering double 'sweet spot' quantitative evaluation model, preferably a shale gas enrichment high-yield zone, and assists in efficient exploration and development.

The invention provides a method for quantitatively evaluating a shale gas dessert, which comprises the following steps:

1) determining geology sensitive dessert parameters and engineering dessert parameters according to the basic geological data, the logging data and the seismic data;

2) carrying out geophysical prediction based on the geology sensitive dessert parameters and the engineering dessert parameters confirmed in the step 1) to obtain a prediction result;

3) establishing a shale gas dessert quantitative evaluation model Q based on the prediction result obtained in the step 2);

4) determining a quantitative evaluation factor Q of the shale gas dessert based on the quantitative evaluation model Q in the step 3)_sweet；

5) According to the evaluation factor Q_sweetThe value range of (2) determines that the shale gas is beneficial to exploration areas.

Preferably, in step 2), the geophysical prediction comprises:

2-1) TOC seismic prediction based on high-precision prestack density inversion;

2-2) post-stack seismic porosity prediction based on good correlation of post-stack wave impedance and porosity;

2-3) brittle index prestack seismic predictions based on multiparameters λ ρ, μ ρ, E, σ, where λ is the lame coefficient, μ is the shear modulus, ρ is the formation density, σ is the poisson ratio, and E is the young's modulus;

2-4) post-stack seismic fracture prediction based on high precision body curvature.

Preferably, in step 3), a shale gas sweet spot quantitative evaluation model Q is established by the following formula:

Q＝G(x₁,x₂,x₃…x_n)/B(a₁,a₂,a₃…a_n) (1)

wherein, G (x)₁,x₂,x₃…x_n) Dessert parameter x for positive preservation of shale gas enrichment₁,x₂,x₃…x_nProduct of (a), B (a)₁,a₂,a₃…a_n) Dessert parameter a for destroying shale gas enrichment and preservation₁,a₂,a₃…a_nThe product of (a).

Preferably, in step 4), the shale gas sweet spot quantitative evaluation factor Q is determined by the following formula_sweet：

Q_sweet＝Normalize(Q) (2)

Preferably, in step 1), the geologically sensitive sweet spot parameters include: total organic carbon content TOC, porosity phi, pressure coefficient PC, total gas content Cz and roof crack density Frc.

Preferably, in step 1), the engineered dessert parameters include a friability index, BRT, and a horizontal ground stress difference.

Preferably, the parameters that play a positive role in shale gas enrichment preservation include: total organic carbon content TOC, brittleness index BRT, pressure coefficient PC and porosity Φ.

Preferably, the parameters that have a destructive effect on shale gas enrichment preservation include: top plate crack density Frc.

Preferably, in step 1-1), the TOC prediction model is established by the following formula:

TOC＝aρ+b (3)

wherein a and b are regional empirical constants, and rho is the formation density.

Preferably, in step 5), the evaluation factor Q of the shale gas favorable exploration area is determined_sweetThe numerical ranges of (A) are: q_sweet∈(0，0.3]Three types of dessert regions, Q_sweet∈(0.3，0.6]Being a type II dessert region, Q_sweet∈(0.6，1]Is a dessert area, wherein one dessert area and the second dessert area are favorable exploration areas of shale gas.

The present invention has other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts.

FIG. 1 illustrates a step diagram of a method for quantitatively evaluating shale gas desserts in accordance with the present invention;

FIG. 2 is a TOC prediction plan view of a first section of high quality shale from Wufeng in Dingshan area to Longmaxi;

FIG. 3 is a plan view of a prediction of porosity of a section of high quality shale from Wufeng-Longmaxi group in Dingshan region;

FIG. 4 is a plan view of a pressure coefficient prediction plan for a section of high quality shale in mountain region Wufeng-Longmaxi;

FIG. 5 is a plan view of the prediction of brittleness index of a section of high-quality shale in Wufeng-Longmaxi group in the mountain area Ding;

FIG. 6 is a plan view of crack density prediction of a top plate of high-quality shale in Wufeng-Longmaxi section of the mountain area Ding;

FIG. 7 is an evaluation chart of a first segment of high quality shale dual dessert in Wufeng-Longmaxi group in Ding mountain area.

Detailed Description

The invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Fig. 1 shows a step diagram of a method for quantitatively evaluating shale gas desserts according to the present invention.

In this embodiment, the method for quantitatively evaluating a shale gas dessert according to the present invention may include:

and step S1, determining the geology sensitive dessert parameter and the engineering dessert parameter according to the basic geological data, the logging data and the seismic data.

In one example, the geological data includes: logging, layering, crack interpretation, gas testing, shale core test data and the like; the logging data includes: longitudinal wave time difference, transverse wave time difference, density logging, TOC, gas content interpretation curve and the like; the seismic data includes: conventional post-stack or pre-stack migration processed result data, velocity spectrum data, structure interpretation horizon and fault data, and the like.

In particular, in the Dingshan area of southeast of Chuandong, the enrichment and storage of shale gas are controlled by high-quality shale and storage conditions, and the fracturing effect of a horizontal well is controlled by good fracturability, so that the yield of a shale gas exploration well is influenced; the higher the porosity phi is, the more beneficial to shale gas enrichment is; the key sweet-spot parameters for representing the shale gas storage conditions are a pressure coefficient PC and a top plate fracture density Frc, and the higher the pressure coefficient PC of the shale gas layer is, the lower the top plate fracture density Frc is, and the better the storage conditions are. In the aspect of engineering desserts, the brittleness index BRT and the horizontal ground stress difference are parameters for characterizing the shale gas engineering desserts capable of being fractured, the higher the brittleness index is, the relatively small horizontal ground stress difference (experience shows that the horizontal ground stress difference is 5-10MPa), the better the fracturing performance is, and the more easily the shale gas layer is fractured. And step S2, developing geophysical prediction based on the geology sensitive dessert parameters and the engineering dessert parameters confirmed in the step S1, and obtaining a prediction result.

In one example, the geophysical prediction comprises:

2-1) TOC seismic prediction based on high-precision prestack density inversion;

2-2) post-stack seismic porosity prediction based on good correlation of post-stack wave impedance and porosity;

2-3) brittle index prestack seismic predictions based on multiparameters λ ρ, μ ρ, E, σ, where λ is the lame coefficient, μ is the shear modulus, ρ is the formation density, σ is the poisson ratio, and E is the young's modulus;

and 2-4) predicting the post-stack earthquake crack based on high-precision body curvature, and obtaining the prediction results of the total organic carbon content TOC, the porosity phi, the brittleness index BRT, the pressure coefficient PC and the shale gas top plate crack density Frc of the high-quality shale gas layer based on the prediction.

Specifically, the TOC prediction model is established by the following formula:

TOC＝aρ+b (3)

wherein a and b are regional empirical constants, and rho is the formation density.

And step S3, establishing a shale gas sweet spot quantitative evaluation model Q based on the prediction result obtained in the step S2.

In one example, a shale gas sweet spot quantitative evaluation model Q is established by the following formula:

Q＝G(x₁,x₂,x₃…x_n)/B(a₁,a₂,a₃…a_n) (1)

wherein, G (x)₁,x₂,x₃…x_n) Dessert parameter x for positive preservation of shale gas enrichment₁,x₂,x₃…x_nProduct of (a), B (a)₁,a₂,a₃…a_n) Dessert parameter a for destroying shale gas enrichment and preservation₁,a₂,a₃…a_nThe product of (a).

Specifically, the parameters that play a positive role in shale gas enrichment preservation include: TOC, brittleness index BRT, pressure coefficient PC and porosity phi; parameters that may be disruptive to shale gas enrichment preservation include: top plate crack density Frc.

Step S4, determining a quantitative evaluation factor Q of the shale gas dessert based on the quantitative evaluation model Q in the step S3_sweet。

In one example, the shale gas sweet spot quantitative evaluation factor Q is determined by the following equation_sweet：

Q_sweet＝Normalize(Q) (2)

Step S5, based on the evaluation factor Q_sweetThe value range of (2) determines that the shale gas is beneficial to exploration areas.

In one example, Q_sweet∈(0，0.3]Three types of dessert regions, Q_sweet∈(0.3，0.6]Being a type II dessert region, Q_sweet∈(0.6，1]Is a dessert area, wherein one dessert area and the second dessert area are favorable exploration areas of shale gas.

According to the invention, by establishing the dessert quantitative evaluation model, the shale gas dessert comprehensive evaluation in the complex-structure area can be completed, the enriched high-yield zone is preferably selected, and the efficient exploration and development are assisted.

Application example

To facilitate understanding of the solution of the embodiments of the present invention and the effects thereof, a specific application example is given below. It will be understood by those skilled in the art that this example is merely for the purpose of facilitating an understanding of the present invention and that any specific details thereof are not intended to limit the invention in any way.

Taking the evaluation of the ocean shale gas dessert of the Ordovician quincunx group-the Xianmaxi group of the Xishan area in the south of the east Chuan as an example, on the basis of controlling the optimization of key dessert parameters for shale gas enrichment and preservation, the invention introduces the influence of the development density of the top plate crack on the storage condition of the shale gas and the enrichment high yield based on the geophysical prediction results of geological dessert (TOC, pressure coefficient, porosity and the like) and engineering dessert (brittleness index and the like), develops an enrichment high yield zone evaluation method and quantitative evaluation model research, establishes a shale gas geology and engineering double 'dessert' quantitative evaluation model, optimizes the shale gas high yield enrichment zone, and assists in efficient exploration and development.

Firstly, preparing geological data including logging, layering, crack interpretation, gas testing and shale core test data; logging data including longitudinal wave time difference, transverse wave time difference, density logging, TOC, gas content interpretation curve and the like; including production data for conventional post-stack or pre-stack migration processing, velocity spectrum data, seismic data for structure-interpreted horizons and fault data.

Then, dessert parameters that play a positive role in shale gas enrichment preservation are preferred: TOC, porosity, brittleness index, pressure coefficient and dessert parameters which have destructive effect on shale gas enrichment and preservation: shale gas layer roof fracture density as a key sensitive sweet spot parameter is the most basic data of sweet spot evaluation.

Secondly, carrying out geophysical prediction of key sensitive geological desserts and engineering desserts parameters, wherein the step of establishing a TOC prediction model based on good correlation between density and TOC is as follows: the TOC is a rho + b, a and b are regional empirical constants, rho is rock stratum density, the TOC can be obtained through prestack seismic inversion, TOC seismic prediction based on high-precision prestack density inversion is carried out, as shown in FIG. 2, a high-quality shale TOC prediction result graph based on high-precision prestack density inversion is carried out for a section of mountain area Wufeng-Longmaxi group based on good correlation between density and TOC; predicting the post-stack seismic porosity based on good correlation between post-stack wave impedance and porosity, and developing a post-stack seismic porosity prediction result diagram based on good correlation between post-stack wave impedance and porosity in a Wufeng-Longmaxi group section of high-quality shale section in the mountain area of Dingshan as shown in FIG. 3; as shown in fig. 4, the result of prediction of a high-quality shale section in mountain area wufeng-rampart based on the improved phillips formula pressure coefficient prediction is shown in a graph; fig. 5 is a shale brittleness index prediction method based on multiple regression, which is a prediction achievement diagram of a high-quality shale section of a mountain area quincunx-dragon rivulx group obtained by performing brittleness index prestack earthquake prediction and a poststack earthquake crack prediction based on high-precision body curvature, and as shown in fig. 6, is a poststack earthquake crack prediction achievement diagram based on high-precision body curvature among layers of the mountain area quincunx-dragon rivulx group two-three sections (shale gas layer top plates); and obtaining the prediction results of the TOC, the porosity, the brittleness index, the pressure coefficient and the shale gas top plate fracture density of the high-quality shale gas layer.

Thirdly, based on the analysis of key sensitive dessert parameters for controlling shale gas enrichment and preservation, a shale gas dessert quantitative evaluation model Q and a dessert evaluation factor Q are established_sweet。

Specifically, Q ═ G (x)₁,x₂,x₃…x_n)/B(a₁,a₂,a₃…a_n) (1)

Then carrying out normalization processing on the Q to obtain the Q_sweet：Q_sweet＝Normalize(Q) (2)

Wherein: g (x)₁,x₂,x₃…x_n) Dessert parameter x for positive preservation of shale gas enrichment₁,x₂,x₃…x_nProduct of G (x) in the mountain region₁,x₂,x₃…x_n)＝TOC×BRT×PC×Φ(3)；B(a₁,a₂,a₃…a_n) Dessert parameter a for destroying shale gas enrichment and preservation₁,a₂,a₃…a_nIn the mountain region, B (a)₁,a₂,a₃…a_n)＝Frc(4)。

And finally, in the area of the tongtong south of the Chuan province, taking the top plate crack density as an adverse factor influencing the shale gas dessert as a denominator, multiplying the TOC, the brittleness index, the pressure coefficient and the porosity as favorable terms for shale gas enrichment storage as a molecule, and carrying out comprehensive quantitative evaluation on the shale gas dessert by utilizing the geophysical prediction results of the TOC, the BRT, the PC, the phi and the Frc based on a dessert evaluation model, and preferably selecting a shale gas exploration high-yield enrichment zone. As shown in fig. 7, a double-dessert evaluation chart for comprehensively and quantitatively evaluating shale gas desserts is developed for a first high-quality shale section of a mountain region Wufeng-Longmaxi group based on dessert evaluation factors and by utilizing geophysical prediction results, and the evaluation shows that the mountain region Wufeng-Longmaxi group is mainly a first-type dessert region and a second-type dessert region, and the shale gas quality of the drilled wells in the first-type dessert region and the second-type dessert region is good, the pressure coefficient is high, and the yield is high, and the geological rule and the drilling knowledge are met.

It will be appreciated by persons skilled in the art that the above description of embodiments of the invention is intended only to illustrate the benefits of embodiments of the invention and is not intended to limit embodiments of the invention to any examples given.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.