CN111353218B - Logging quantitative evaluation method for coal bed gas-dense gas reservoir compaction property - Google Patents

Logging quantitative evaluation method for coal bed gas-dense gas reservoir compaction property Download PDF

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CN111353218B
CN111353218B CN202010106873.6A CN202010106873A CN111353218B CN 111353218 B CN111353218 B CN 111353218B CN 202010106873 A CN202010106873 A CN 202010106873A CN 111353218 B CN111353218 B CN 111353218B
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刘之的
刘洪壮
梁文杰
陈秀娟
曹晋璐
袁思乔
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Xian Shiyou University
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Abstract

A logging quantitative evaluation method for coalbed methane-dense gas reservoir compaction property comprises the following steps: calculating the brittleness index difference between the sand layer and the coal bed; step two: calculating the minimum horizontal ground stress difference between the sand layer and the coal bed; step three: calculating the tensile strength difference between the sandstone and the coal rock; step four: calculating the Young modulus difference of the sandstone and the coal rock; and finally, evaluating the compressibility of the coal bed gas-dense gas reservoir by using the four evaluation indexes according to the brittleness index difference between the sand layer and the coal bed, the minimum horizontal main stress difference between the sandstone and the coal rock, the tensile strength difference between the sandstone and the coal rock and the Young modulus difference between the sand layer and the coal bed, so that the logging technical support is preferably provided for the fracturing layer of the coal bed gas-dense gas reservoir while the quantitative evaluation precision of the compressibility logging of the coal bed gas-dense gas reservoir is improved, and the method has the characteristics of simplicity and practicability.

Description

一种煤层气-致密气储层合压性的测井定量评价方法A well logging quantitative evaluation method for the compressibility of coalbed methane-tight gas reservoirs

技术领域Technical Field

本发明涉及测井评价技术领域,特别涉及一种煤层气-致密气储层合压性的测井定量评价方法。The invention relates to the technical field of well logging evaluation, and in particular to a well logging quantitative evaluation method for the combined pressure of coalbed methane-tight gas reservoirs.

背景技术Background Art

煤层气-致密气联合开发过程中常采用压裂等增产措施,煤层气-致密气储层合压性评价成为制定压裂方案的一项重要工作。地球物理测井资料隐含着煤层气-致密气储层力学、地应力、压力等诸多信息,据此,可利用测井资料来评价煤层气-致密气储层的合压性。In the process of joint development of coalbed methane and tight gas, fracturing and other production-increasing measures are often used. The evaluation of the compressibility of coalbed methane and tight gas reservoirs has become an important task in formulating fracturing plans. Geophysical logging data contains a lot of information such as coalbed methane and tight gas reservoir mechanics, ground stress, pressure, etc. Based on this, logging data can be used to evaluate the compressibility of coalbed methane and tight gas reservoirs.

现有储层可压性的测井评价方法,多用脆性指数、破裂压力数值大小来划分可压性。然而,煤层气-致密气储层和致密气储层的脆性指数、杨氏模量及抗拉强度等差异较大,煤层气-致密气储层间的地应力对压裂也会产生较大的影响。其次,如何将煤层气-致密气储层作为一个系统来评价可压性,目前尚无研究报道。从现有可压性评价方法来看,尚且没有利用测井资料来定量评价煤层气-致密气储层可压性的方法,这给煤层气-致密气联合开发过程中压裂层位优选带来不便。The existing logging evaluation methods for reservoir compressibility mostly use brittleness index and fracture pressure values to classify compressibility. However, there are large differences in brittleness index, Young's modulus and tensile strength between coalbed methane-tight gas reservoirs and tight gas reservoirs, and the ground stress between coalbed methane-tight gas reservoirs will also have a great impact on fracturing. Secondly, how to evaluate the compressibility of coalbed methane-tight gas reservoirs as a system has not been reported yet. From the perspective of existing compressibility evaluation methods, there is no method to quantitatively evaluate the compressibility of coalbed methane-tight gas reservoirs using logging data, which brings inconvenience to the optimization of fracturing layers during the joint development of coalbed methane-tight gas.

发明内容Summary of the invention

为了克服上述现有技术的缺点,本发明的目的在于提供一种煤层气-致密气储层合压性的测井定量评价方法,利用测井资料确定砂岩与煤岩的脆性指数差、砂岩与煤岩的最小水平主应力差、砂岩与煤岩的抗拉强度差、砂层与煤层杨氏模量差,并以此四个评价指标来对煤层气-致密气储层的可压性进行评价,在提高煤层气-致密气储层可压性测井定量评价精度的同时,将为煤层气-致密气储层压裂层位优选提供测井技术支持,具有方法简单、实用的特点。In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a logging quantitative evaluation method for the compressibility of coalbed methane-tight gas reservoirs, which uses logging data to determine the brittleness index difference between sandstone and coal rock, the minimum horizontal principal stress difference between sandstone and coal rock, the tensile strength difference between sandstone and coal rock, and the Young's modulus difference between sand layer and coal layer, and uses these four evaluation indicators to evaluate the compressibility of coalbed methane-tight gas reservoirs. While improving the accuracy of quantitative logging evaluation of the compressibility of coalbed methane-tight gas reservoirs, it will provide logging technology support for the optimization of fracturing positions for coalbed methane-tight gas reservoirs, and has the characteristics of simple method and practicality.

为了达到上述目的,本发明采取的技术方案为:In order to achieve the above object, the technical solution adopted by the present invention is:

一种煤层气-致密气储层合压性的测井定量评价方法,步骤如下:A well logging quantitative evaluation method for the compressibility of coalbed methane-tight gas reservoirs, the steps are as follows:

步骤一:计算砂层与煤层的脆性指数差Step 1: Calculate the brittleness index difference between sand layer and coal layer

采用式(1)确定砂层与煤层的脆性指数差The brittleness index difference between sand layer and coal layer is determined by formula (1):

ΔIB=IBS-IBC (I)ΔI B =I BS -I BC (I)

式中:ΔIB为砂层与煤层的脆性指数差值,%;IBS、IBC分别为砂层、煤层的脆性指数,%;Where: ΔI B is the difference in brittleness index between sand layer and coal layer, %; I BS and I BC are the brittleness index of sand layer and coal layer respectively, %;

其中:in:

Figure BDA0002388272960000021
Figure BDA0002388272960000021

Figure BDA0002388272960000022
Figure BDA0002388272960000022

Figure BDA0002388272960000023
Figure BDA0002388272960000023

Figure BDA0002388272960000024
Figure BDA0002388272960000024

Figure BDA0002388272960000025
Figure BDA0002388272960000025

式中:IBE、I分别为杨氏模量和泊松比法计算的脆性指数,%;IB为煤层的脆性指数,%;E、Emax、Emin分别为煤层的杨氏模量、最大杨氏模量和最小杨氏模量比,104MPa;μ、μmax、μmin分别为煤层的泊松比、最大泊松比和最小泊松比,无量纲;ρb为体积密度,g/cm3;Δt、Δts分别为煤层的纵、横波时差,μs/ft;Where: I BE and I are the brittleness index calculated by Young's modulus and Poisson's ratio method, %; I B is the brittleness index of the coal seam, %; E, E max and E min are the Young's modulus, the maximum Young's modulus and the minimum Young's modulus ratio of the coal seam, 10 4 MPa; μ, μ max and μ min are the Poisson's ratio, the maximum Poisson's ratio and the minimum Poisson's ratio of the coal seam, dimensionless; ρ b is the bulk density, g/cm 3 ; Δt and Δt s are the longitudinal and transverse wave time differences of the coal seam, μs/ft;

步骤二:计算砂层与煤层的最小水平地应力差Step 2: Calculate the minimum horizontal stress difference between the sand layer and the coal seam

利用测井资料,在确定煤层及砂岩地应力的基础上,采用式(2)确定煤层及其顶底板间的最小水平主应力差:Based on the determination of the in-situ stress of the coal seam and sandstone using the logging data, the minimum horizontal principal stress difference between the coal seam and its roof and floor is determined using formula (2):

Δσ=σsc (2)Δσ=σ sc (2)

式中:Δσ为砂层与煤层的最小水平主应力差,MPa;σs为煤层顶底板的最小水平主应力,MPa;σc为煤层的最小水平主应力,MPa;Where: Δσ is the minimum horizontal principal stress difference between the sand layer and the coal seam, MPa; σs is the minimum horizontal principal stress of the top and bottom plates of the coal seam, MPa; σc is the minimum horizontal principal stress of the coal seam, MPa;

其中in

σs

Figure BDA0002388272960000031
σ s or
Figure BDA0002388272960000031

Figure BDA0002388272960000032
Figure BDA0002388272960000032

Figure BDA0002388272960000033
Figure BDA0002388272960000033

式中:σv为垂向地应力,MPa;α为Biot系数,无量纲;Pp为地层孔隙压力,MPa;β1为最小水平地应力方向的构造应力系数,无量纲;ρo为没有测井密度深度段的地层平均密度值,g/cm3;Ho为密度测井的起始深度,m;H为计算点的深度,m;Δtma为煤岩骨架的声波时差,μs/ft;A、B为地区系数,无量纲;其他参数物理意义同上;Where: σ v is vertical geostress, MPa; α is Biot coefficient, dimensionless; P p is formation pore pressure, MPa; β 1 is tectonic stress coefficient in the direction of minimum horizontal geostress, dimensionless; ρ o is the average density value of the formation without logging density depth section, g/cm 3 ; H o is the starting depth of density logging, m; H is the depth of the calculation point, m; Δt ma is the acoustic time difference of the coal rock skeleton, μs/ft; A and B are regional coefficients, dimensionless; the physical meanings of other parameters are the same as above;

步骤三:计算砂岩与煤岩的抗拉强度差Step 3: Calculate the difference in tensile strength between sandstone and coal rock

利用测井资料泥质含量和杨氏模量的基础上,计算砂层与煤层的抗拉强度,进而确定砂层与煤层的抗拉强度差:Based on the shale content and Young's modulus of the logging data, the tensile strength of the sand layer and the coal layer is calculated, and then the tensile strength difference between the sand layer and the coal layer is determined:

ΔC=Cs-Cc (3)ΔC= Cs - Cc (3)

ΔC为砂层与煤层的抗拉强度差,MPa;Cs、Cc分别为砂层、煤层的抗拉强度,MPa;ΔC is the difference in tensile strength between the sand layer and the coal layer, MPa; Cs and Cc are the tensile strengths of the sand layer and the coal layer, MPa respectively;

其中:in:

Cs或Cc=0.0045E(1-Vsh)+0.008E·Vsh Cs or Cc = 0.0045E(1- Vsh ) + 0.008E· Vsh

式中:E为地层的杨氏模量,104MPa;Vsh为地层的泥质含量,%;Where: E is the Young's modulus of the formation, 10 4 MPa; Vsh is the shale content of the formation, %;

步骤四:计算砂岩与煤岩的杨氏模量差Step 4: Calculate the difference in Young's modulus between sandstone and coal rock

利用测井资料计算砂层与煤层的杨氏模量,进而确定砂层与煤层的杨氏模量差:The Young's modulus of the sand layer and the coal layer is calculated using the logging data, and then the Young's modulus difference between the sand layer and the coal layer is determined:

ΔE=Es-Ec (4)ΔE=E s -E c (4)

式中:ΔE为砂层与煤层的杨氏模量差,104MPa;Es、Ec分别为砂层、煤层的杨氏模量,104Mpa;Where: ΔE is the difference in Young's modulus between the sand layer and the coal layer, 10 4 MPa; Es and Ec are the Young's modulus of the sand layer and the coal layer, 10 4 MPa respectively;

步骤五:砂岩与煤岩合压性评价Step 5: Evaluation of the compressibility of sandstone and coal rock

依据以上步骤的结果,得出了表1所示的煤层气-致密气储层合压性评价等级划分标准:Based on the results of the above steps, the classification standard for the evaluation of the compressibility of coalbed methane-tight gas reservoirs is obtained as shown in Table 1:

表1煤层气-致密气储层合压性评价等级划分表Table 1 Classification of evaluation levels of coalbed methane-tight gas reservoir compressibility

Figure BDA0002388272960000041
Figure BDA0002388272960000041

由表1可知,将煤层气-致密气储层的合压性评价划分为三类:Ⅰ类表示合压性评价好、合压性强;Ⅱ类表示合压性评价中等、具备一定的合压性;Ⅲ类表示合压性评价差、难以成功压裂。As can be seen from Table 1, the pressure compressibility evaluation of coalbed methane-tight gas reservoirs is divided into three categories: Category I indicates good pressure compressibility evaluation and strong pressure compressibility; Category II indicates medium pressure compressibility evaluation and certain pressure compressibility; Category III indicates poor pressure compressibility evaluation and difficulty in successful fracturing.

与现有技术相比,本发明的有益效果为:本发明煤层气-致密气储层合压性测井定量评价方法,能够有效地利用测井资料进行煤层气-致密气储层合压性评价,将砂岩与煤岩的脆性指数差、砂岩与煤岩的最小水平主应力差、砂岩与煤岩的抗拉强度差、砂层与煤层杨氏模量差等四个评价指标有机结合在一起,在提高煤层气-致密气储层合压性测井定量评价精度的同时,也为压裂层位优选提供了强有力的测井技术支持,开辟了利用测井资料评价煤层气-致密气储层合压性的新途径,具有方法简单、实用的特点,具有良好的推广应用价值。Compared with the prior art, the beneficial effects of the present invention are as follows: the coalbed methane-tight gas reservoir pressure compressibility quantitative evaluation method of the present invention can effectively use logging data to evaluate the coalbed methane-tight gas reservoir pressure compressibility, and organically combines four evaluation indicators, namely, the brittleness index difference between sandstone and coal rock, the minimum horizontal principal stress difference between sandstone and coal rock, the tensile strength difference between sandstone and coal rock, and the Young's modulus difference between sand layer and coal layer. While improving the accuracy of the coalbed methane-tight gas reservoir pressure compressibility quantitative evaluation logging, it also provides strong logging technology support for the optimization of fracturing layers, opens up a new way to evaluate the coalbed methane-tight gas reservoir pressure compressibility using logging data, has the characteristics of simple method and practicality, and has good promotion and application value.

附图说明BRIEF DESCRIPTION OF THE DRAWINGS

图1为本发明中的煤层气-致密气储层合压性的测井定量评价方法流程图。FIG1 is a flow chart of the well logging quantitative evaluation method for the combined pressure of coalbed methane and tight gas reservoirs in the present invention.

图2为本发明的煤层气-致密气储层合压性测井定量评价成果图。FIG. 2 is a diagram showing the quantitative evaluation results of the combined pressure logging of the coalbed methane-tight gas reservoir according to the present invention.

具体实施方式DETAILED DESCRIPTION

下面结合实施例对本发明做进一步详细说明。The present invention is further described in detail below with reference to the embodiments.

参照图1,一种煤层气-致密气储层合压性的测井定量评价方法,包括以下步骤:1, a well logging quantitative evaluation method for the compressibility of coalbed methane-tight gas reservoirs includes the following steps:

一种煤层气-致密气储层合压性的测井定量评价方法,步骤如下:A well logging quantitative evaluation method for the compressibility of coalbed methane-tight gas reservoirs, the steps are as follows:

步骤一:计算砂层与煤层的脆性指数差Step 1: Calculate the brittleness index difference between sand layer and coal layer

砂层与煤层具有不同的脆性,一般情况下砂层的脆性较大;若脆性指数差异较大,砂层能够成功压裂,而煤层难以形成压裂缝;Sand layers and coal layers have different brittleness. Generally, sand layers are more brittle. If the brittleness index is different, the sand layer can be successfully fractured, but it is difficult to form fractures in the coal layer.

采用式(1)确定砂层与煤层的脆性指数差:The brittleness index difference between sand layer and coal layer is determined by formula (1):

ΔIB=IBS-IBC (I)ΔI B =I BS -I BC (I)

式中:ΔIB为砂层与煤层的脆性指数差值,%;IBS、IBC分别为砂层、煤层的脆性指数,%;Where: ΔI B is the difference in brittleness index between sand layer and coal layer, %; I BS and I BC are the brittleness index of sand layer and coal layer respectively, %;

其中in

Figure BDA0002388272960000061
Figure BDA0002388272960000061

Figure BDA0002388272960000062
Figure BDA0002388272960000062

Figure BDA0002388272960000063
Figure BDA0002388272960000063

Figure BDA0002388272960000064
Figure BDA0002388272960000064

Figure BDA0002388272960000065
Figure BDA0002388272960000065

式中:IBE、I分别为杨氏模量和泊松比法计算的脆性指数,%;IB为煤层的脆性指数,%;E、Emax、Emin分别为煤层的杨氏模量、最大杨氏模量和最小杨氏模量比,104MPa;μ、μmax、μmin分别为煤层的泊松比、最大泊松比和最小泊松比,无量纲;ρb为体积密度,g/cm3;Δt、Δts分别为煤层的纵、横波时差,μs/ft。In the formula: I BE and I are the brittleness index calculated by Young's modulus and Poisson's ratio method, respectively, %; I B is the brittleness index of the coal seam, %; E, E max and E min are the Young's modulus, maximum Young's modulus and minimum Young's modulus ratio of the coal seam, respectively, 10 4 MPa; μ, μ max and μ min are the Poisson's ratio, maximum Poisson's ratio and minimum Poisson's ratio of the coal seam, respectively, dimensionless; ρ b is the bulk density, g/cm 3 ; Δt and Δt s are the longitudinal and shear wave time differences of the coal seam, respectively, μs/ft.

步骤二:计算砂层与煤层的最小水平地应力差Step 2: Calculate the minimum horizontal stress difference between the sand layer and the coal seam

砂层的水平向主应力一般大于煤层,由于构造作用产生的水平主应力在砂岩层中更大,致使砂层与煤层的最小水平地应力差较大;当砂层与煤层的最小水平地应力差增大时,缝高逐渐减小,裂缝被完全限制在煤层中,煤层中的缝长在稳步增长,高砂层地应力会阻碍裂缝向砂层扩展。The horizontal principal stress of the sand layer is generally greater than that of the coal seam. The horizontal principal stress generated by tectonic action is greater in the sandstone layer, resulting in a larger difference in the minimum horizontal geostress between the sand layer and the coal seam. When the difference in the minimum horizontal geostress between the sand layer and the coal seam increases, the fracture height gradually decreases, the fracture is completely confined in the coal seam, the fracture length in the coal seam increases steadily, and the high geostress of the sand layer will hinder the extension of the fracture into the sand layer.

利用测井资料,在确定煤层及砂岩地应力的基础上,采用式(2)确定煤层及其顶底板间的最小水平主应力差:Based on the determination of the in-situ stress of the coal seam and sandstone using the logging data, the minimum horizontal principal stress difference between the coal seam and its roof and floor is determined using formula (2):

Δσ=σ5c (2)Δσ=σ 5c (2)

式中:Δσ为砂层与煤层的最小水平主应力差,MPa;σs为煤层顶底板的最小水平主应力,MPa;σc为煤层的最小水平主应力,MPa;Where: Δσ is the minimum horizontal principal stress difference between the sand layer and the coal seam, MPa; σs is the minimum horizontal principal stress of the top and bottom plates of the coal seam, MPa; σc is the minimum horizontal principal stress of the coal seam, MPa;

其中in

σs

Figure BDA0002388272960000071
σ s or
Figure BDA0002388272960000071

Figure BDA0002388272960000072
Figure BDA0002388272960000072

Figure BDA0002388272960000073
Figure BDA0002388272960000073

式中:σv为垂向地应力,MPa;α为Biot系数,无量纲;Pp为地层孔隙压力,MPa;β1为最小水平地应力方向的构造应力系数,无量纲;ρo为没有测井密度深度段的地层平均密度值,g/cm3;Ho为密度测井的起始深度,m;H为计算点的深度,m;Δtma为煤岩骨架的声波时差,μs/ft;A、B为地区系数,无量纲;其他参数物理意义同上。Wherein: σ v is vertical geostress, MPa; α is Biot coefficient, dimensionless; P p is formation pore pressure, MPa; β 1 is tectonic stress coefficient in the direction of minimum horizontal geostress, dimensionless; ρ o is the average density value of the formation without logging density depth section, g/cm 3 ; H o is the starting depth of density logging, m; H is the depth of the calculation point, m; Δt ma is the acoustic time difference of the coal rock skeleton, μs/ft; A and B are regional coefficients, dimensionless; the physical meanings of other parameters are the same as above.

步骤三:计算砂岩与煤岩的抗拉强度差Step 3: Calculate the difference in tensile strength between sandstone and coal rock

随着砂层抗拉强度的增加,缝高减小,缝长和缝宽逐渐增加;低抗拉强度的砂层会使裂缝在缝高方向迅速扩展;抗拉强度越大,缝长方向上的扩展阻力就更大,缝内压力易积聚,从而在缝高方向上发生穿层现象。As the tensile strength of the sand layer increases, the fracture height decreases, and the fracture length and width gradually increase; the sand layer with low tensile strength will cause the crack to expand rapidly in the fracture height direction; the greater the tensile strength, the greater the expansion resistance in the fracture length direction, and the pressure in the fracture is easy to accumulate, resulting in the occurrence of layer penetration in the fracture height direction.

利用测井资料泥质含量和杨氏模量的基础上,计算砂层与煤层的抗拉强度,进而确定砂层与煤层的抗拉强度差:Based on the shale content and Young's modulus of the logging data, the tensile strength of the sand layer and the coal layer is calculated, and then the tensile strength difference between the sand layer and the coal layer is determined:

ΔC=Cs-Cc (3)ΔC= Cs - Cc (3)

其中:in:

Cs或Cc=0.0045E(1-Vsh)+0.008E·Vsh Cs or Cc = 0.0045E(1- Vsh ) + 0.008E· Vsh

式中:ΔC为砂层与煤层的抗拉强度差,MPa;Cs、Cc分别为砂层、煤层的抗拉强度,MPa;E为地层的杨氏模量,104MPa;Vsh为地层的泥质含量,%。Where: ΔC is the difference in tensile strength between the sand layer and the coal layer, MPa; Cs and Cc are the tensile strengths of the sand layer and the coal layer, MPa; E is the Young's modulus of the formation, 10 4 MPa; Vsh is the mud content of the formation, %.

步骤四:计算砂岩与煤岩的杨氏模量差Step 4: Calculate the difference in Young's modulus between sandstone and coal rock

随着砂层弹性模量的增大,裂缝缝高方向的剖面变得愈加“瘦高”,缝宽逐渐减小,缝高增大,缝长方向有很明显的减小趋势;弹性模量大的砂岩层限制了缝宽的增长,在缝长方向的裂缝尖端压力越小,越难在缝长方向上扩展。As the elastic modulus of the sand layer increases, the profile of the fracture in the direction of fracture height becomes more "thin and tall", the fracture width gradually decreases, the fracture height increases, and there is a very obvious decreasing trend in the fracture length direction; the sandstone layer with a large elastic modulus limits the growth of the fracture width, and the smaller the pressure at the fracture tip in the fracture length direction, the more difficult it is to expand in the fracture length direction.

利用测井资料计算砂层与煤层的杨氏模量,进而确定砂层与煤层的杨氏模量差:The Young's modulus of the sand layer and the coal layer is calculated using the logging data, and then the Young's modulus difference between the sand layer and the coal layer is determined:

ΔE=Es-EC (4)ΔE=E s -EC (4)

式中:ΔE为砂层与煤层的杨氏模量差,104MPa;Es、Ec分别为砂层、煤层的杨氏模量,104MPa。Where: ΔE is the difference in Young's modulus between the sand layer and the coal layer, 10 4 MPa; Es and Ec are the Young's modulus of the sand layer and the coal layer, 10 4 MPa respectively.

步骤五:砂岩与煤岩合压性评价Step 5: Evaluation of the compressibility of sandstone and coal rock

依据以上步骤的结果,在实际生产验证的基础上,得出了表1所示的煤层气-致密气储层合压性评价等级划分标准:According to the results of the above steps and on the basis of actual production verification, the classification standard of coalbed methane-tight gas reservoir compressibility evaluation is obtained as shown in Table 1:

表1煤层气-致密气储层合压性评价等级划分表Table 1 Classification of evaluation levels of coalbed methane-tight gas reservoir compressibility

Figure BDA0002388272960000091
Figure BDA0002388272960000091

由表1可知,将煤层气-致密气储层的合压性评价划分为三类:Ⅰ类表示合压性评价好、合压性强;Ⅱ类表示合压性评价中等、具备一定的合压性;Ⅲ类表示合压性评价差、难以成功压裂。As can be seen from Table 1, the pressure compressibility evaluation of coalbed methane-tight gas reservoirs is divided into three categories: Category I indicates good pressure compressibility evaluation and strong pressure compressibility; Category II indicates medium pressure compressibility evaluation and certain pressure compressibility; Category III indicates poor pressure compressibility evaluation and difficulty in successful fracturing.

基于上述煤层气-致密气储层合压性评价各个评价指标测井计算模型,在编制处理解释程序的基础上,对研究区各井主力煤层气-致密气储层的合压性进行了测井处理解释。Based on the above-mentioned logging calculation model for evaluating the compressibility of coalbed methane-tight gas reservoirs, and on the basis of compiling processing and interpretation procedures, logging processing and interpretation were carried out on the compressibility of the main coalbed methane-tight gas reservoirs in each well in the study area.

图2是X井煤层气-致密气储层合压性测井定量评价成果图。该井致密气储层段1073.5-1079m,厚度为5.5m;煤层气储层段1082.2-1085.3,厚度为3.1m。该煤层气-致密气储层脆性指数差为28,最小水平主应力差0.5MPa、砂抗拉强度差3.4MPa、杨氏模量差5.2GPa,煤层气-致密气储层合压性评价综合评价为Ⅰ类,表明合压性强。该煤层气-致密气储层进行合压,压裂后微地震监测结果表明,该煤层气-致密气储层均形成了径向长、纵向宽的复杂压裂缝,压裂施工后日产气1.3万方。这充分说明本研究评价的合压性评价与实际压裂监测、排采均较为吻合,同时也进一步表明合压性测井定量评价的精准与否对煤层气压裂层段的优选起到关键作用。该方法充分挖掘了测井资料中所蕴藏的煤层气-致密气储层合压性信息,评价能够满足煤层气-致密气储层压裂层位优选的要求。Figure 2 is a quantitative evaluation result of the well logging of the combined pressure of the coalbed methane-tight gas reservoir in Well X. The well has a tight gas reservoir section of 1073.5-1079m with a thickness of 5.5m; the coalbed methane reservoir section is 1082.2-1085.3 with a thickness of 3.1m. The brittleness index difference of the coalbed methane-tight gas reservoir is 28, the minimum horizontal principal stress difference is 0.5MPa, the sand tensile strength difference is 3.4MPa, and the Young's modulus difference is 5.2GPa. The comprehensive evaluation of the combined pressure of the coalbed methane-tight gas reservoir is Class I, indicating that the combined pressure is strong. The coalbed methane-tight gas reservoir was combined pressured, and the microseismic monitoring results after fracturing showed that the coalbed methane-tight gas reservoir had formed complex fractures with long radial length and wide vertical length, and the daily gas production after fracturing was 13,000 cubic meters. This fully demonstrates that the compressibility evaluation of this study is consistent with the actual fracturing monitoring and drainage, and further shows that the accuracy of the quantitative evaluation of compressibility logging plays a key role in the optimization of coalbed methane fracturing layers. This method fully exploits the compressibility information of coalbed methane-tight gas reservoirs contained in the logging data, and the evaluation can meet the requirements of coalbed methane-tight gas reservoir fracturing layer optimization.

本领域的技术人员应当理解,由于煤层气测井受环境因素的影响较为严重,为了保证该方法的有效可行性,必须保障测井资料的环境影响校正效果较好,砂岩与煤岩的脆性指数差、砂岩与煤岩的最小水平主应力差、砂岩与煤岩的抗拉强度差、砂层与煤层杨氏模量差等四个评价指标计算较为准确,煤层气-致密气储层合压性测井定量评价结果才具有较高的精度。Those skilled in the art should understand that since coalbed methane logging is seriously affected by environmental factors, in order to ensure the effectiveness and feasibility of the method, it is necessary to ensure that the environmental impact correction effect of the logging data is good, and the four evaluation indicators, namely the brittleness index difference between sandstone and coal rock, the minimum horizontal principal stress difference between sandstone and coal rock, the tensile strength difference between sandstone and coal rock, and the Young's modulus difference between sand layer and coal layer, are calculated more accurately, so that the quantitative evaluation results of coalbed methane-tight gas reservoir combined pressure logging will have higher accuracy.

Claims (4)

1.一种煤层气-致密气储层合压性的测井定量评价方法,其特征在于,步骤如下:1. A well logging quantitative evaluation method for the compressibility of coalbed methane-tight gas reservoirs, characterized in that the steps are as follows: 步骤一:计算砂层与煤层的脆性指数差Step 1: Calculate the brittleness index difference between sand layer and coal layer 采用式(1)确定砂层与煤层的脆性指数差:The brittleness index difference between sand layer and coal layer is determined by formula (1): ΔIB=IBS-IBC (1)ΔI B =I BS -I BC (1) 式中:ΔIB为砂层与煤层的脆性指数差值,%;IBS、IBC分别为砂层、煤层的脆性指数,%;Where: ΔI B is the difference in brittleness index between sand layer and coal layer, %; I BS and I BC are the brittleness index of sand layer and coal layer respectively, %; 步骤二:计算砂层与煤层的最小水平地应力差Step 2: Calculate the minimum horizontal stress difference between the sand layer and the coal seam 利用测井资料,在确定煤层及砂岩地应力的基础上,采用式(2)确定煤层及其顶底板间的最小水平主应力差:Based on the determination of the in-situ stress of the coal seam and sandstone using the logging data, the minimum horizontal principal stress difference between the coal seam and its roof and floor is determined using formula (2): Δσ=σsc (2)Δσ=σ sc (2) 式中:Δσ为砂层与煤层的最小水平主应力差,MPa;σs为煤层顶底板的最小水平主应力,MPa;σc为煤层的最小水平主应力,MPa;Where: Δσ is the minimum horizontal principal stress difference between the sand layer and the coal seam, MPa; σs is the minimum horizontal principal stress of the top and bottom plates of the coal seam, MPa; σc is the minimum horizontal principal stress of the coal seam, MPa; 步骤三:计算砂岩与煤岩的抗拉强度差Step 3: Calculate the difference in tensile strength between sandstone and coal rock 利用测井资料泥质含量和杨氏模量的基础上,计算砂层与煤层的抗拉强度,进而确定砂层与煤层的抗拉强度差:Based on the shale content and Young's modulus of the logging data, the tensile strength of the sand layer and the coal layer is calculated, and then the tensile strength difference between the sand layer and the coal layer is determined: ΔC=Cs-Cc (3)ΔC= Cs - Cc (3) 式中:ΔC为砂层与煤层的抗拉强度差,MPa;Cs、Cc分别为砂层、煤层的抗拉强度,MPa;Where: ΔC is the difference in tensile strength between the sand layer and the coal layer, MPa; Cs and Cc are the tensile strengths of the sand layer and the coal layer, MPa respectively; 步骤四:计算砂岩与煤岩的杨氏模量差Step 4: Calculate the difference in Young's modulus between sandstone and coal rock 利用测井资料计算砂层与煤层的杨氏模量,进而确定砂层与煤层的杨氏模量差:The Young's modulus of the sand layer and the coal layer is calculated using the logging data, and then the Young's modulus difference between the sand layer and the coal layer is determined: ΔE=Es-Ec (4)ΔE=E s -E c (4) 式中:ΔE为砂层与煤层的杨氏模量差,104MPa;Es、Ec分别为砂层、煤层的杨氏模量,104MPa;Where: ΔE is the difference in Young's modulus between the sand layer and the coal layer, 10 4 MPa; Es and Ec are the Young's modulus of the sand layer and the coal layer, 10 4 MPa respectively; 步骤五:砂岩与煤岩合压性评价Step 5: Evaluation of the compressibility of sandstone and coal rock 依据以上步骤的结果,得出了表1所示的煤层气-致密气储层合压性评价等级划分标准:Based on the results of the above steps, the classification standard for the evaluation of the compressibility of coalbed methane-tight gas reservoirs is obtained as shown in Table 1: 表1 煤层气-致密气储层合压性评价等级划分表Table 1 Classification of evaluation levels of coalbed methane-tight gas reservoir compressibility
Figure FDA0002388272950000021
Figure FDA0002388272950000021
由表1可知,将煤层气-致密气储层的合压性评价划分为三类:I类表示合压性评价好、合压性强;II类表示合压性评价中等、具备一定的合压性;IⅡ类表示合压性评价差、难以成功压裂。As can be seen from Table 1, the compressibility evaluation of coalbed methane-tight gas reservoirs is divided into three categories: Category I indicates good compressibility evaluation and strong compressibility; Category II indicates medium compressibility evaluation and certain compressibility; Category IⅡ indicates poor compressibility evaluation and difficulty in successful fracturing.
2.根据权利要求1所述的一种煤层气-致密气储层合压性的测井定量评价方法,其特征在于,2. The well logging quantitative evaluation method for the compressibility of coalbed methane-tight gas reservoirs according to claim 1 is characterized in that: 步骤一中,In step one,
Figure FDA0002388272950000022
Figure FDA0002388272950000022
Figure FDA0002388272950000031
Figure FDA0002388272950000031
Figure FDA0002388272950000032
Figure FDA0002388272950000032
Figure FDA0002388272950000033
Figure FDA0002388272950000033
Figure FDA0002388272950000034
Figure FDA0002388272950000034
式中:IBE、I分别为杨氏模量和泊松比法计算的脆性指数,%;IB为煤层的脆性指数,%;E、Emax、Emin分别为煤层的杨氏模量、最大杨氏模量和最小杨氏模量比,104MPa;μ、μmax、μmin分别为煤层的泊松比、最大泊松比和最小泊松比,无量纲;ρb为体积密度,g/cm3;Δt、Δts分别为煤层的纵、横波时差,μs/ft。In the formula: I BE and I are the brittleness index calculated by Young's modulus and Poisson's ratio method, respectively, %; I B is the brittleness index of the coal seam, %; E, E max and E min are the Young's modulus, maximum Young's modulus and minimum Young's modulus ratio of the coal seam, respectively, 10 4 MPa; μ, μ max and μ min are the Poisson's ratio, maximum Poisson's ratio and minimum Poisson's ratio of the coal seam, respectively, dimensionless; ρ b is the bulk density, g/cm 3 ; Δt and Δt s are the longitudinal and shear wave time differences of the coal seam, respectively, μs/ft.
3.根据权利要求1所述的一种煤层气-致密气储层合压性的测井定量评价方法,其特征在于,3. The method for quantitative evaluation of the compressibility of coalbed methane-tight gas reservoirs by logging according to claim 1, characterized in that: 步骤二中,In step 2, σs
Figure FDA0002388272950000035
σ s or
Figure FDA0002388272950000035
Figure FDA0002388272950000036
Figure FDA0002388272950000036
Figure FDA0002388272950000037
Figure FDA0002388272950000037
式中:σv为垂向地应力,MPa;μ、为煤层的泊松比;α为Biot系数,无量纲;Pp为地层孔隙压力,MPa;β1为最小水平地应力方向的构造应力系数,无量纲;ρo为没有测井密度深度段的地层平均密度值,g/cm3;Ho为密度测井的起始深度,m;H为计算点的深度,m;Δtma为煤岩骨架的声波时差,μs/ft;A、B为地区系数,无量纲。In the formula: σ v is the vertical geostress, MPa; μ and μ are the Poisson's ratio of the coal seam; α is the Biot coefficient, dimensionless; P p is the formation pore pressure, MPa; β 1 is the tectonic stress coefficient in the direction of minimum horizontal geostress, dimensionless; ρ o is the average density value of the formation without logging density depth section, g/cm 3 ; H o is the starting depth of density logging, m; H is the depth of the calculation point, m; Δt ma is the acoustic time difference of the coal rock skeleton, μs/ft; A and B are regional coefficients, dimensionless.
4.根据权利要求1所述的一种煤层气-致密气储层合压性的测井定量评价方法,其特征在于,4. The method for quantitative evaluation of the compressibility of coalbed methane-tight gas reservoirs by logging according to claim 1, characterized in that: 步骤三中,In step three, Cs或Cc=0.0045E(1-Vsh)+0.008E·Vsh Cs or Cc = 0.0045E(1- Vsh ) + 0.008E· Vsh E为地层的杨氏模量,104MPa;Vsh为地层的泥质含量,%。E is the Young's modulus of the formation, 10 4 MPa; Vsh is the shale content of the formation, %.
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