CN101942992B

CN101942992B - Method for predicting pore pressure of regional high-pressure saltwater layer by utilizing curvature of face of geologic structure

Info

Publication number: CN101942992B
Application number: CN201010257163XA
Authority: CN
Inventors: 金衍; 陈勉; 卢运虎; 侯冰; 梁红军; 李宁; 张辉
Original assignee: China University of Petroleum Beijing
Current assignee: China University of Petroleum Beijing
Priority date: 2010-08-19
Filing date: 2010-08-19
Publication date: 2013-11-20
Anticipated expiration: 2030-08-19
Also published as: CN101942992A

Abstract

The invention discloses a method for predicting the pore pressure of the regional high-pressure saline layer by using the curvature of the geological structure surface. The method utilizes the curvature of the geological structure surface to predict the pore pressure of the regional high-pressure saline layer. The salt-gypsum layer is determined by seismic data and actual drilling logging data Regional distribution law and structural contour map, use the harmonic trend surface method to establish the regional elevation equation on the geological structure contour map and determine the principal curvature of any point in the structural region, calculate the principal stress at any point, and establish the pore pressure at any point The prediction model determines the pore pressure of the high-pressure brine layer, so as to provide a scientific basis for determining the safe drilling fluid density when the drilling design determines the site construction, so as to effectively prevent the collapse of the well wall and prevent the occurrence of downhole complex situations.

Description

A Method for Predicting the Pore Pressure of Regional High Pressure Salt Water Layer Using the Curvature of Geological Tectonic Surface

技术领域 technical field

本发明涉及一种利用地质构造面曲率预测区域高压盐水层孔隙压力的方法。The invention relates to a method for predicting the pore pressure of a regional high-pressure saline layer by using the curvature of a geological structure surface.

背景技术 Background technique

我国大部分油气资源集中在盐下构造，盐岩地层钻井是制约我国石油钻探的关键技术难题。由于地层受构造挤压变形的作用，形成异常高压盐水层，区域分布无规律，钻井过程中经常与高压盐水层发生遭遇战，当钻井液的密度不能平衡地层压力时，并会发生盐水将进入井筒，污染钻井液，产生钻井事故和复杂情况，给钻井作业的人力、物力带来不同程度的损失。为此如何在钻井前事先预测高压盐水层孔隙压力是非常必要的，若在钻井前能预测到高压盐水层孔隙压力，就可以为钻井设计确定现场施工时安全钻井液密度提供科学的依据，以有效阻止井壁失稳、防止井下复杂情况的发生。Most of my country's oil and gas resources are concentrated in pre-salt structures, and drilling in salt rock formations is a key technical problem restricting my country's oil drilling. Because the formation is squeezed and deformed by the structure, an abnormally high-pressure brine layer is formed, and the regional distribution is irregular. During the drilling process, encounters with high-pressure brine layers often occur. When the density of the drilling fluid cannot balance the formation pressure, brine will enter The wellbore will pollute the drilling fluid, cause drilling accidents and complex situations, and bring different degrees of loss to the manpower and material resources of drilling operations. Therefore, how to predict the pore pressure of the high-pressure saline layer before drilling is very necessary. If the pore pressure of the high-pressure saline layer can be predicted before drilling, it can provide a scientific basis for the drilling design to determine the safe drilling fluid density during on-site construction. Effectively prevent the instability of the well wall and prevent the occurrence of downhole complex situations.

为此本发明中的创作人凭借其多年从事相关行业的经验与实践，并经潜心研究与开发，终于创造出一种利用地质构造面曲率预测区域高压盐水层孔隙压力的方法For this reason, the creators of this invention rely on their many years of experience and practice in related industries, and through painstaking research and development, finally created a method for predicting the pore pressure of regional high-pressure saline layer by using the curvature of the geological structure surface

发明内容 Contents of the invention

本发明的目的在于提供一种利用地质构造面曲率预测区域高压盐水层孔隙压力的方法，利用该方法可以在钻井前预测到构造区域高压盐水层孔隙压力，以便在钻井设计确定现场施工时为确定安全钻井液密度提供科学依据，以有效阻止井壁失稳、防止井下复杂情况的发生。The purpose of the present invention is to provide a method for predicting the pore pressure of the high-pressure saline layer in the region by using the curvature of the geological structure surface. This method can be used to predict the pore pressure of the high-pressure saline layer in the structural region before drilling, so as to determine the pore pressure when the drilling design is determined and the site is constructed. Safe drilling fluid density provides a scientific basis to effectively prevent wellbore instability and prevent downhole complex situations from occurring.

本发明中利用地质构造面曲率预测区域高压盐水层孔隙压力的方法，包括有下列步骤：In the present invention, the method for predicting the pore pressure of the regional high-pressure saline layer by using the curvature of the geological structure surface includes the following steps:

1)根据地震反射剖面和实钻盐层层段，找出区域盐层的顶界和底界，获得区域分布；1) Find out the top boundary and bottom boundary of the regional salt layer according to the seismic reflection profile and the actual drilled salt layer section, and obtain the regional distribution;

2)利用趋势面法计算构造面底部的曲率，获得每一空间点的曲率，计算主曲率(ρ₁，ρ₂)；2) Use the trend surface method to calculate the curvature at the bottom of the structural surface, obtain the curvature of each spatial point, and calculate the principal curvature (ρ ₁ , ρ ₂ );

3)根据测井资料回归统计上覆岩层压力σ_v；3) Regression statistics of the overburden pressure _σv according to the logging data;

4)根据测井资料计算盐间砂岩夹层的弹性模量和泊松比；4) Calculate the elastic modulus and Poisson's ratio of the inter-salt sandstone interlayer according to the logging data;

5)利用已知盐层构造面底部的主曲率、弹性模量和泊松比，确定所在地层的主应力，建立孔隙压力预测模型；5) Using the principal curvature, elastic modulus and Poisson's ratio at the bottom of the known salt formation plane, determine the principal stress of the formation and establish a pore pressure prediction model;

6)计算孔隙压力，根据每一空间点的孔隙压力，作压力等值线，获得压力分布规律。6) Calculate the pore pressure, draw the pressure contour according to the pore pressure of each space point, and obtain the pressure distribution rule.

所述步骤2)中的方法是由盐层构造等值线图上的地理坐标(x_i，y_i)及相应点的高程数据w_i利用调和趋势面法建立w＝w(x，y)的构造图的高程方程，由方程w＝w(x，y)计算构造图上任意一点(x_i，y_i)的主曲率(ρ_1i，ρ_2i)。The method in said step 2) is to use the harmonic trend surface method to establish w=w(x, y) by the geographic coordinates ( _xi , y _i ) on the contour map of the salt layer structure and the elevation data w _i of the corresponding points The elevation equation of the structural map, the principal curvature ( _{ρ 1i} _, ρ _2i ) of any point (xi, y _i ) on the structural map is calculated by the equation w=w(x, y).

所述步骤5)中的方法是由计算的盐岩构造底部任一点的主曲率(ρ_1i，ρ_2i)结合相应地层的弹性模量、泊松比计算该点的主应力(σ_1i，σ_2i)，即获得预测地层任意一点的三向主应力序列(σ_1i，σ_2i，σ_vi)，利用岩石构造变形过程中任意点岩石体积变形Δv_i近似为岩石孔隙变形Δv_ki，得出盐岩构造曲面上任意一点孔隙压力模型p_i＝f(ρ_1i，ρ_2i，h)。 _{The method in step 5) is to calculate the principal stress (σ 1i} _, _σ _2i ), that is, to obtain the three-dimensional principal stress sequence (σ _1i , σ _2i , σ _vi ) at any point in the predicted formation, and use the rock volume deformation Δv _i at any point in the rock structure deformation process to approximate the rock pore deformation Δv _ki , and obtain the salt The pore pressure model p _i = f(ρ _1i , ρ _2i , h) at any point on the rock structure surface.

本发明中利用地质构造面曲率预测区域高压盐水层孔隙压力是通过地震资料和实钻录井资料确定盐膏层的区域分布规律和构造等值线图，利用调和趋势面法建立地质构造等值线图上的区域高程方程并确定构造区域任意点的主曲率，计算任意点的主应力，建立任意点的孔隙压力预测模型，确定高压盐水层的孔隙压力，以便在钻井设计确定现场施工时为确定安全钻井液密度提供科学依据，以有效阻止井壁坍塌、防止井下复杂情况的发生。In the present invention, using the curvature of the geological structure surface to predict the pore pressure of the regional high-pressure brine layer is to determine the regional distribution law and structural contour map of the salt-gypsum layer through seismic data and actual drilling logging data, and use the harmonic trend surface method to establish the geological structure equivalent The regional elevation equation on the line map and determine the principal curvature of any point in the structural area, calculate the principal stress at any point, establish a pore pressure prediction model at any point, and determine the pore pressure of the high-pressure saline layer, so that when the drilling design determines the site construction Determining the safe drilling fluid density provides a scientific basis to effectively prevent borehole wall collapse and prevent downhole complex situations from occurring.

附图说明 Description of drawings

图1是预测区域地质构造图；Figure 1 is a map of the predicted regional geological structure;

图2是预测区域高压盐水层孔隙压力分布图。Fig. 2 is the pore pressure distribution map of the high-pressure saline layer in the predicted area.

具体实施方式 Detailed ways

下面将结合附图对本发明中的具体实施例作进一步详细说明。The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

在漫长的地质年代里，由于地壳的褶皱运动使盐层发生弯曲，或由于基底隆起使盐层上拱，盐间封闭的盐水层受构造挤压、抬升和盐岩塑形流动的作用形成异常高压，构造变形的程度与盐水层异常压力具有一定的联系。一般来说，构造变形越剧烈，异常高压盐水层孔隙压力越大，构造变形的程度可以用构造面上任意点曲率来描述，而曲率与岩石的力学本构变形有着内在联系。岩石本构关系是揭示岩石受力与变形的定量化描述，其中包含着如地层弹性参数、地层成分、密度、埋藏深度、地质年代、孔隙率、构造运动等因素。地质构造曲率能不同程度地反映地层所受外界作用的程度，因此利用地质构造面曲率可以进行钻前预测区域高压盐水层孔隙压力。In the long geological time, due to the folding movement of the earth's crust, the salt layer is bent, or the salt layer is arched due to the uplift of the basement, and the closed salt water layer between salts is anomalously formed due to structural compression, uplift and plastic flow of salt rock. The degree of high pressure and structural deformation is related to the abnormal pressure of the saline layer. Generally speaking, the more severe the structural deformation, the greater the pore pressure of the abnormally high-pressure brine layer. The degree of structural deformation can be described by the curvature of any point on the structural surface, and the curvature is inherently related to the mechanical constitutive deformation of rocks. The constitutive relationship of rock is a quantitative description that reveals the force and deformation of rock, which includes factors such as formation elastic parameters, formation composition, density, burial depth, geological age, porosity, and tectonic movement. The curvature of the geological structure can reflect the degree of external action on the formation to varying degrees, so the curvature of the geological structure surface can be used to predict the pore pressure of the regional high-pressure saline layer before drilling.

本发明中利用地质构造面曲率预测区域高压盐水层孔隙压力包括下列步骤：In the present invention, using the curvature of the geological structure surface to predict the pore pressure of the regional high-pressure saline layer includes the following steps:

1.区域盐层分布规律的确定1. Determination of the distribution law of regional salt layers

在预测区域根据地震反射剖面和实钻录井资料确定区域盐层分布规律和构造等值线分布图。In the predicted area, according to the seismic reflection section and the actual drilling logging data, the distribution law of the regional salt layer and the distribution map of the structural contour are determined.

即首先确定区域地震反射剖面上盐顶和盐底的深度，同时根据实钻录井资料获得的盐顶和盐底的深度进行标定，建立区域的盐层分布规律。That is, first determine the depth of the salt top and salt bottom on the regional seismic reflection profile, and at the same time calibrate the depth of the salt top and salt bottom obtained from the actual drilling and logging data to establish the distribution law of the regional salt layer.

2.确定盐层地质构造面的主曲率2. Determine the principal curvature of the geological structure plane of the salt layer

根据划定的盐层区域的分布规律和获得的盐层构造等值线图1，获取地层构造等值线图上的任意点的地理坐标(x_i，y_i)及相应点的高程数据w_i，利用调和趋势面法建立构造图的高程方程w＝w(x，y)，由方程w＝w(x，y)计算构造图上任意点(x_i，y_i)的主曲率(ρ_1i，ρ_2i)，具体方法如下：According to the distribution law of the delineated salt layer area and the obtained salt layer structure contour map 1, the geographic coordinates (xi _, y _i ) of any point on the stratum structure contour map and the elevation data w of the corresponding point are obtained _i , use the harmonic trend _surface method to establish the elevation equation w=w(x, y) of the structural map, and calculate _the principal curvature (ρ _1i , ρ _2i ), the specific method is as follows:

为了计算上的方便，设构造图高程方程满足一阶傅立叶级数趋势面方程，具体形式如下：For the convenience of calculation, the elevation equation of the structural map is assumed to satisfy the first-order Fourier series trend surface equation, and the specific form is as follows:

w＝a₀₀+a₁₀A₁C₀+a₀₁A₀C₁+a₁₁A₁C₁+b₁₀B₁C₀ (2.1)w=a ₀₀ +a ₁₀ A ₁ C ₀ +a ₀₁ A ₀ C ₁ +a ₁₁ A ₁ C ₁ +b ₁₀ B ₁ C ₀ (2.1)

+b₁₁B₁C₁+c₀₁A₀D₁+c₁₁A₁D₁+d₁₁B₁D₁ ₊ b ₁₁ B ₁ C ₁ +c ₀₁ A ₀ D ₁ +c ₁₁ A 1 D ₁ +d ₁₁ B ₁ D ₁

一阶傅立叶级数趋势面方程中有9个特定系数；a₀₀，a₁₀，a₀₁，a₁₁，b₁₀，b₁₁，c₀₁，c₁₁，d₁₁。式中：There are 9 specific coefficients in the first-order Fourier series trend surface equation; a ₀₀ , a ₁₀ , a ₀₁ , a ₁₁ , b ₁₀ , b ₁₁ , c ₀₁ , c ₁₁ , d ₁₁ . In the formula:

${A A}_{t t} = = cos cos \frac{22 tπx tπx}{L L},,$ ${B B}_{t t} = = sin sin \frac{22 tπx tπx}{L L},, ((t t = = 0,1 0,1))$

${C C}_{k k} = = cos cos \frac{22 kπy kπy}{H h},,$ ${D D.}_{k k} = = sin sin \frac{22 kπy kπy}{H h},, ((k k = = 0,1 0,1))$

为求出方程中的待定系数，可按最小二乘法原理，是每个待定系数对观测值与趋势值的离差平方和In order to find the undetermined coefficient in the equation, according to the principle of the least square method, it is the sum of the squares of the deviation of each undetermined coefficient to the observed value and the trend value

$Q Q = = {Σ Σ}_{i i = = 11}^{n no} {(({z z}_{i i} - - {\overset{^^}{z z}}_{i i}))}^{22} = = {Σ Σ}_{i i = = 11}^{n no} (({z z}_{i i} - - {a a}_{0000} - - {a a}_{1010} {A A}_{11} {C C}_{00} - - {a a}_{0101} {A A}_{00} {C C}_{11} - - {a a}_{1111} {A A}_{11} {C C}_{11}$

${- - {b b}_{1010} {B B}_{11} {C C}_{00} - - {b b}_{1111} {B B}_{11} {C C}_{11} - - {c c}_{0101} {A A}_{00} {D D.}_{11} - - {c c}_{1111} {A A}_{11} {D D.}_{11} - - {d d}_{1111} {B B}_{11} {D D.}_{11}))}^{22} - - - - - - ((2.2 2.2))$

的偏导数等于0，即The partial derivative of is equal to 0, that is

上述9个方程式经整理可得到一阶傅立叶级数趋势面的正规方程组，可写成如下矩阵形式The above nine equations can be arranged to obtain the normal equations of the first-order Fourier series trend surface, which can be written in the following matrix form

$[\begin{matrix} Σ Σ 11 & Σ Σ {A A}_{11} {C C}_{00} & Σ Σ {A A}_{00} {C C}_{11} & \cdot &Center Dot; \cdot &Center Dot; \cdot &Center Dot; & Σ Σ {B B}_{11} {D D.}_{11} \\ Σ Σ {A A}_{11} {C C}_{00} & Σ Σ {(({A A}_{11} {C C}_{00}))}^{22} & Σ Σ {A A}_{11} {C C}_{00} {A A}_{00} {C C}_{11} & \cdot &Center Dot; \cdot &Center Dot; \cdot &Center Dot; & Σ Σ {A A}_{11} {C C}_{00} {B B}_{11} {D D.}_{11} \\ Σ Σ {A A}_{00} {C C}_{11} & Σ Σ {A A}_{00} {C C}_{11} {A A}_{11} {C C}_{00} & Σ Σ {(({A A}_{00} {C C}_{11}))}^{22} & \cdot &Center Dot; \cdot &Center Dot; \cdot &Center Dot; & Σ Σ {A A}_{00} {C C}_{11} {B B}_{11} {D D.}_{11} \\ Σ Σ {A A}_{11} {C C}_{11} & Σ Σ {A A}_{11} {C C}_{11} {A A}_{11} {C C}_{00} & Σ Σ {A A}_{11} {C C}_{11} {A A}_{00} {C C}_{11} & \cdot \cdot \cdot \cdot \cdot &Center Dot; & Σ Σ {A A}_{11} {C C}_{11} {B B}_{11} {D D.}_{11} \\ \cdot &Center Dot; \cdot \cdot \cdot &Center Dot; & \cdot &Center Dot; \cdot &Center Dot; \cdot &Center Dot; & \cdot &Center Dot; \cdot &Center Dot; \cdot &Center Dot; & \cdot &Center Dot; \cdot &Center Dot; \cdot &Center Dot; & \cdot &Center Dot; \cdot &Center Dot; \cdot &Center Dot; \\ Σ Σ {B B}_{11} {D D.}_{11} & Σ Σ {B B}_{11} {D D.}_{11} {A A}_{11} {C C}_{00} & Σ Σ {B B}_{11} {D D.}_{11} {A A}_{00} {C C}_{11} & \cdot &Center Dot; \cdot \cdot \cdot &Center Dot; & Σ Σ {(({B B}_{11} {D D.}_{11}))}^{22} \end{matrix}] [\begin{matrix} {a a}_{0000} \\ {a a}_{1010} \\ {a a}_{0101} \\ {a a}_{1111} \\ {d d}_{1111} \end{matrix}] = = [\begin{matrix} Σ Σ \\ Σz Σz {A A}_{11} {C C}_{00} \\ Σz Σz {A A}_{00} {C C}_{11} \\ Σz Σz {A A}_{11} {C C}_{11} \\ \cdot \cdot \cdot &Center Dot; \cdot \cdot \\ Σz Σz {B B}_{11} {D D.}_{11} \end{matrix}] - - - - - - ((2.4 2.4))$

由式(2.1)可解出式(2.1)中的待定系数。The undetermined coefficients in formula (2.1) can be solved from formula (2.1).

根据构造图上的各点坐标(x_i，y_i)及高程数据w_i，可建立正归方程According to the coordinates (x _i , y _i ) of each point on the structural map and the elevation data w _i , the positive regression equation can be established

$[\begin{matrix} N N & Σx Σx & Σy Σy & Σ Σ {x x}^{22} & Σxy Σxy & Σ Σ {y the y}^{22} & \cdot &Center Dot; \cdot \cdot \cdot \cdot \\ Σx Σx & Σ Σ {x x}^{22} & Σxy Σxy & Σ Σ {x x}^{33} & Σ Σ {x x}^{22} y the y & Σ Σ {xy xy}^{22} & \cdot &Center Dot; \cdot &Center Dot; \cdot \cdot \\ Σy Σy & Σxy Σxy & Σ Σ {y the y}^{22} & Σ Σ {x x}^{22} y the y & Σ Σ {xy xy}^{22} & Σ Σ {y the y}^{33} & \cdot \cdot \cdot &Center Dot; \cdot \cdot \\ \cdot &Center Dot; & \cdot &Center Dot; & \cdot \cdot & \cdot &Center Dot; & \cdot \cdot & \cdot &Center Dot; \\ \cdot &Center Dot; & \cdot \cdot & \cdot \cdot & \cdot &Center Dot; & \cdot \cdot & \cdot &Center Dot; & \cdot &Center Dot; \cdot \cdot \cdot &Center Dot; \\ \cdot &Center Dot; & \cdot &Center Dot; & \cdot &Center Dot; & \cdot \cdot & \cdot &Center Dot; & \cdot &Center Dot; \end{matrix}] [\begin{matrix} {c c}_{0000} \\ {c c}_{1010} \\ {c c}_{0101} \\ \cdot &Center Dot; \\ \cdot &Center Dot; \\ \cdot &Center Dot; \end{matrix}] = = [\begin{matrix} Σw Σw \\ Σxw Σxw \\ Σyw Σyw \\ \cdot &Center Dot; \\ \cdot &Center Dot; \\ \cdot &Center Dot; \end{matrix}] - - - - - - ((2.5 2.5))$

式中N为总点数，w为海拔高程，解出c₀₀，c₁₀，c₀₁，c₂₀，c₁₁…等系数，即得w(x，y)的近似表达式。In the formula, N is the total number of points, w is the altitude, and the coefficients such as c ₀₀ , c ₁₀ , c ₀₁ , c ₂₀ , c ₁₁ , etc. are solved to obtain the approximate expression of w(x, y).

根据薄板小挠度弯曲理论，由于w是微小的，薄板中面在x和y方向的曲率及扭率可近似的表示为：According to the small deflection bending theory of the thin plate, since w is small, the curvature and torsion of the middle surface of the thin plate in the x and y directions can be approximately expressed as:

$\frac{11}{{r r}_{x x}} = = - - z z \frac{{&PartialD; &PartialD;}^{22} w w}{{&PartialD; &PartialD; x x}^{22}},,$ $\frac{11}{{r r}_{y the y}} = = - - z z \frac{{&PartialD; &PartialD;}^{22} w w}{{&PartialD; &PartialD; y the y}^{22}},,$ $\frac{11}{{r r}_{xy xy}} = = - - z z \frac{{&PartialD; &PartialD;}^{22} w w}{&PartialD; &PartialD; x x &PartialD; &PartialD; y the y} - - - - - - ((2.6 2.6))$

利用(2.1)式求出构造图上任意点的三个二阶偏导数

和

即可计算出构造曲面上任意点的曲率

据此计算构造面上任意点的主曲率及主方向。主方向可由式：Use formula (2.1) to find the three second-order partial derivatives of any point on the structure map

and

The curvature of any point on the construction surface can be calculated

Based on this, the principal curvature and principal direction of any point on the structural surface are calculated. The principal direction can be given by:

$tan the tan ((22 {α α}_{i i})) = = \frac{- - 11 / / {r r}_{xyi xyi}}{0.5 0.5 ((11 / / {r r}_{xi xi} - - 11 {/ / r r}_{yi yi}))} - - - - - - ((2.7 2.7))$

确定。其中，α_i为主方向和x轴的夹角。构造曲面上任意点主曲率的计算公式为Sure. Among them, α _i is the angle between the main direction and the x-axis. The formula for calculating the principal curvature of any point on the construction surface is

$\frac{11}{{r r}_{1,2 1,2}} = = \frac{11}{22} ((\frac{11}{{r r}_{xi xi}} + + \frac{11}{{r r}_{yi yi}})) &PlusMinus; &PlusMinus; \sqrt{\frac{11}{44} {((\frac{11}{{r r}_{xi xi}} - - \frac{11}{{r r}_{yi yi}}))}^{22} + + {((\frac{11}{{r r}_{xyi xyi}}))}^{22}} - - - - - - ((2.8 2.8))$

即 $ρ_{1 i} = \frac{1}{r_{1}},$ $ρ_{2 i} = \frac{1}{r_{2}} .$ Right now $ρ_{1 i} = \frac{1}{r_{1}},$ $ρ_{2 i} = \frac{1}{r_{2}} .$

3.根据测井资料回归统计上覆岩层压力σ_v 3. Regression and statistics of overburden pressure _σv based on well logging data

密度测井和声波测井可以直观地反映地层压实规律，并能获得岩石体积密度值。由于密度测井资料容易受到井径的大小及仪器检测程度影响，在利用密度测井数据之前，应结合井径测井资料过滤掉非真实数据，以获得比较可靠的密度，并利用这些密度散点数据，利用式(3.1)计算上覆岩层压力梯度：Density logging and acoustic logging can intuitively reflect formation compaction laws and obtain rock volume density values. Since the density logging data is easily affected by the size of the borehole diameter and the detection degree of the instrument, before using the density logging data, it should be combined with the borehole logging data to filter out the untrue data to obtain a more reliable density, and use these density Point data, using the formula (3.1) to calculate the pressure gradient of the overlying strata:

${G G}_{z z}^{i i} = = \frac{{ρ ρ}_{w w} {H h}_{w w} + + {ρ ρ}_{00} {H h}_{00} + + \underset{i i}{Σ Σ} {ρ ρ}_{i i} {dh d h}_{i i}}{{H h}_{w w} + + {H h}_{w w} + + \underset{i i}{Σ Σ} {dh d h}_{i i}} - - - - - - ((3.1 3.1))$

式中

为任意点i的上覆岩层压力梯度，g/cm³；ρ_w，H_w分别为地层水的密度及水深，g/cm³，m；ρ₀，H₀分别为上部无密度测井数据段的平均密度及井深，g/cm³，m；ρ_i，dh_i为密度测井数据及与其对应的测井层段厚度，g/cm³，m。In the formula

is the pressure gradient of the overlying strata at any point i, g/cm ³ ; ρ _w , H _w are the density and water depth of the formation water, g/cm ³ , m; ρ ₀ , H ₀ are the upper density-free logging data The average density and well depth of the section, g/cm ³ , m; ρ _i , dh _i are the density logging data and the corresponding logging interval thickness, g/cm ³ , m.

由测井数据计算得到的密度散点求出上覆岩层压力梯度数据以后，通过数据回归，即可获得上覆岩层压力的统计规律。考虑到幂律和二项式回归模型精度较低的缺陷，采用式(3.2)形式的三次多项式进行回归：After obtaining the pressure gradient data of the overlying strata from the density scatter points calculated from the logging data, the statistical law of the overlying strata pressure can be obtained through data regression. Considering the defect of low precision of power law and binomial regression model, the cubic polynomial in the form of formula (3.2) is used for regression:

G_z＝a₀+a₁h+a₂h²+a₃h³ (3.2)G _z =a ₀ +a ₁ h+a ₂ h ² +a ₃ h ³ (3.2)

式中G_z为上覆岩层压力梯度，g/cm³；h为考察点的深度，m；a₀，a₁，a₂，a₃为待定回归系数。即构造曲面上任意点的上覆岩层压力为：In the formula, G _z is the pressure gradient of the overlying strata, g/cm ³ ; h is the depth of the investigation point, m; a ₀ , a ₁ , a ₂ , and a ₃ are undetermined regression coefficients. That is, the overburden pressure at any point on the structural surface is:

σ_vi＝G_Zh_i (3.3)σ _vi =G _Z h _i (3.3)

4.根据测井资料计算预测地层的弹性模量和泊松比4. Calculate and predict the elastic modulus and Poisson's ratio of the formation according to the logging data

地层的弹性模量和泊松比由测井数据解释获得，具体步骤如下：The elastic modulus and Poisson's ratio of the formation are obtained by interpreting the logging data, and the specific steps are as follows:

(1)计算动态弹性模量

和动态泊松比

(1) Calculate the dynamic elastic modulus

and dynamic Poisson's ratio

${E E.}_{d d}^{i i} = = \frac{{ρ ρ}^{i i} {v v}_{s the s}^{{i i}^{22}} ((33 {v v}_{p p}^{{i i}^{22}} - - 44 {v v}_{s the s}^{{i i}^{22}}))}{{v v}_{p p}^{{i i}^{22}} - - 22 {v v}_{s the s}^{{i i}^{22}}} - - - - - - ((4.1 4.1))$

${μ μ}_{d d}^{i i} = = \frac{{v v}_{p p}^{{i i}^{22}} - - 22 {v v}_{s the s}^{{i i}^{22}}}{22 (({v v}_{p p}^{{i i}^{22}} - - {v v}_{s the s}^{{i i}^{22}}))}$

式中：In the formula:

${v v}_{s the s}^{i i} = = \sqrt{11.44 11.44 {v v}_{p p}^{i i} + + 18.03 18.03} - - 5.866 5.866$

${v v}_{p p}^{i i} = = 0.001 0.001 {v v}_{ac ac}^{i i}$

(2)确定静态弹性模量和静态泊松比 (2) Determine the static elastic modulus and static Poisson's ratio

${E E.}_{s the s}^{i i} = = {a a}_{11} + + {b b}_{11} {E E.}_{d d}^{i i} - - - - - - ((4.2 4.2))$

${μ μ}_{s the s}^{i i} = = {a a}_{22} + + {b b}_{22} {μ μ}_{d d}^{i i}$

式中：a₁、b₁、a₂和b₂为系数，视具体区域取值。In the formula: a ₁ , b ₁ , a ₂ and b ₂ are coefficients, and the value depends on the specific area.

5.建立高压盐水层孔隙压力预测模型5. Establishment of pore pressure prediction model for high-pressure saline layer

由计算的盐岩构造底部任一点的主曲率(ρ_1i，ρ_2i)结合相应盐岩地层的弹性模量、泊松比计算该点的主应力(σ_1i，σ_2i)，即获得盐层任意一点的三向主应力序列(σ_1i，σ_2i，σ_vi)，利用岩石构造变形过程中任意点岩石体积变形Δv_i近似为岩石孔隙变形Δv_ki，得出盐岩构造曲面上任意一点孔隙压力模型p_i＝f(ρ_1i，ρ_2i，h)。From the calculated principal curvature (ρ _1i , ρ _2i ) of any point at the bottom of the salt rock structure combined with the elastic modulus and Poisson’s ratio of the corresponding salt rock formation, the principal stress (σ _1i , σ _2i ) of the point is calculated, that is, the salt layer The three-dimensional principal stress sequence (σ _1i , σ _2i , σ _vi ) at any point, using the rock volume deformation Δv _i at any point during the rock structure deformation process, is approximated as the rock pore deformation Δv _ki , and the pore at any point on the salt rock structure surface is obtained Pressure model p _i =f(ρ _1i ,ρ _2i ,h).

具体步骤如下：Specific steps are as follows:

(1)盐岩地质构造曲面上任意点三向主应力计算(1) Calculation of the three-dimensional principal stress at any point on the surface of the salt rock geological structure

根据薄板小挠度弯曲理论，板内一点的应变为：According to the thin plate small deflection bending theory, the strain at a point inside the plate is:

${ϵ ϵ}_{x x} = = - - z z \frac{{&PartialD; &PartialD;}^{22} w w}{{&PartialD; &PartialD; x x}^{22}},,$ ${ϵ ϵ}_{y the y} = = - - z z \frac{{&PartialD; &PartialD;}^{22} w w}{{&PartialD; &PartialD; y the y}^{22}},,$ ${ϵ ϵ}_{xy xy} = = - - z z \frac{{&PartialD; &PartialD;}^{22} w w}{&PartialD; &PartialD; x x &PartialD; &PartialD; y the y} - - - - - - ((5.1 5.1))$

式中：w＝w(x，y)为薄板的挠度。In the formula: w=w(x, y) is the deflection of the thin plate.

由于式(2.3)和(5.1)可得Due to formulas (2.3) and (5.1), we can get

${ϵ ϵ}_{x x} = = z z \frac{11}{{r r}_{x x}},,$ ${ϵ ϵ}_{y the y} = = z z \frac{11}{{r r}_{y the y}},,$ ${ϵ ϵ}_{xy xy} = = z z \frac{11}{{r r}_{xy xy}} - - - - - - ((5.2 5.2))$

则任意点的应力分量为Then the stress component at any point is

${σ σ}_{x x} = = \frac{E E.}{11 - - {μ μ}^{22}} (({ϵ ϵ}_{x x} + + {μϵ μϵ}_{y the y})) = = \frac{Ez Ez}{11 - - {μ μ}^{22}} ((\frac{11}{{r r}_{x x}} + + μ μ \frac{11}{{r r}_{y the y}}))$

${σ σ}_{y the y} = = \frac{E E.}{11 - - {μ μ}^{22}} (({ϵ ϵ}_{y the y} + + {μϵ μϵ}_{x x})) = = \frac{Ez Ez}{11 - - {μ μ}^{22}} ((\frac{11}{{r r}_{y the y}} + + μ μ \frac{11}{{r r}_{x x}})) - - - - - - ((5.3 5.3))$

${τ τ}_{xy xy} = = \frac{E E.}{22 ((11 + + μ μ))} {r r}_{xy xy} = = \frac{Ez Ez}{11 + + μ μ} \frac{11}{{r r}_{xy xy}}$

式中，E、μ分别是弹性模量和泊松比。In the formula, E and μ are elastic modulus and Poisson's ratio, respectively.

由(5.3)中第三式，如果x和y是一点的两个主方向，则τ_xy＝0，从而所以x和y也是该点的两个主曲率方向，说明薄板弹性曲面上一点的主应力方向和主曲率方向相一致。According to the third formula in (5.3), if x and y are the two main directions of a point, then τ _xy =0, thus Therefore, x and y are also the two principal curvature directions of the point, indicating that the principal stress direction of a point on the elastic surface of the thin plate is consistent with the principal curvature direction.

对于弯曲板的任一横截面，正应力最大值出现在隆起一侧的板面上因而板面上一点的主应力为For any cross-section of a curved plate, the maximum normal stress occurs on the plate surface on the side of the bulge Therefore, the principal stress at a point on the plate is

${σ σ}_{11 i i} = = \frac{{Eh Eh}_{i i}}{22 ((11 - - {μ μ}^{22}))} ((\frac{11}{{r r}_{11 i i}} + + μ μ \frac{11}{{r r}_{22 i i}})) - - - - - - ((5.4 5.4))$

${σ σ}_{22 i i} = = \frac{{Eh Eh}_{i i}}{22 ((11 - - {μ μ}^{22}))} ((\frac{11}{{r r}_{22 i i}} + + μ μ \frac{11}{{r r}_{11 i i}}))$

(2)高压盐水层孔隙压力预测模型的建立(2) Establishment of pore pressure prediction model for high-pressure saline layer

岩石受应力作用后，一部分由岩石孔隙中的流体承受(即孔隙压力)，一部分由岩石的骨架承受(即有效应力)。若岩石在封闭不排水情况下任意点受到平均应力为σ_i的三向应力作用，其平均有效应力σ_0i与孔隙压力P_pi的关系为：After the rock is stressed, part of it is borne by the fluid in the rock pores (ie, pore pressure), and part of it is borne by the rock skeleton (ie, effective stress). If the rock is subjected to a three-dimensional stress with an average stress of _σi at any point in the closed and undrained condition, the relationship between the average effective stress σ _0i and the pore pressure P _pi is:

${σ σ}_{00 i i} = = σ σ - - {P P}_{pi p} = = \frac{11}{33} (({σ σ}_{i i 11} + + {σ σ}_{22 i i} + + {σ σ}_{vi vi})) - - {P P}_{pi p} - - - - - - ((5.5 5.5))$

根据弹性理论，在应力作用下任意点岩石的体积变化为：According to the theory of elasticity, the volume change of rock at any point under stress is:

$Δ Δ {V V}_{i i} = = \frac{V V (({σ σ}_{00 i i} - - {P P}_{Pi Pi}))}{{K K}_{i i}} - - - - - - ((5.6 5.6))$

孔隙中流体发生的体积变化为：The volume change of the fluid in the pores is:

$Δ Δ {V V}_{Vi Vi} = = \frac{{n no}_{i i} {P P}_{Pi Pi} V V}{{K K}_{vi vi}} - - - - - - ((5.7 5.7))$

式中，n_i为岩石孔隙率，K_vi为孔隙的体积压缩系数。In the formula, _ni is the porosity of the rock, and K _vi is the volume compressibility coefficient of the pores.

由于成岩以后的岩石骨架体积压缩很小，岩石的体积变化近似等于孔隙的体积变化，则ΔV_i＝ΔV_Vi，于是：Since the volume of the rock skeleton after diagenesis is very small, the volume change of the rock is approximately equal to the volume change of the pores, then ΔV _i = ΔV _Vi , then:

$\frac{{P P}_{Pi Pi}}{{σ σ}_{00 i i}} = = \frac{11}{11 + + \frac{{n no}_{i i} {K K}_{i i}}{{K K}_{Vi Vi}}} = = {B B}_{i i} - - - - - - ((5.8 5.8))$

式中，B_i为孔隙压力系数。In the formula, B _i is the pore pressure coefficient.

联立式(3.3)、(5.6)、(5.7)和(5.8)得高压盐水层孔隙压力预测模型：Combine (3.3), (5.6), (5.7) and (5.8) to get the pore pressure prediction model of high-pressure saline layer:

${p p}_{pi p} = = \frac{{B B}_{i i} {E E.}_{i i} {h h}_{i i}}{66 ((11 - - {μ μ}_{i i}))} [[\frac{11}{{r r}_{i i}} + + \frac{22 ((11 - - {μ μ}_{i i}))}{{E E.}_{i i} {h h}_{i i}} {σ σ}_{vi vi}]] - - - - - - ((5.9 5.9))$

式中定义为等效曲率。defined in the formula is the equivalent curvature.

6.计算高压盐水层孔隙压力6. Calculation of pore pressure in high-pressure saline layer

将待预测区域的地质构造面上的任意点的曲率带入步骤5)中的预测模型，如某并4464.72m构造曲率0.0208，水平最大、最小和上覆岩层地应力分别为116.06、83.48和112.94MPa，计算出该处孔隙压力1.86MPa/100m，实测该点压力数值压力数值1.92MPa/100m，满足工程需要。根据每一空间点的孔隙压力，作压力等值线，获得压力分布规律。Bring the curvature of any point on the geological structure surface of the area to be predicted into the prediction model in step 5), for example, a certain 4464.72m has a structural curvature of 0.0208, and the horizontal maximum, minimum and overlying strata stresses are 116.06, 83.48 and 112.94 respectively MPa, the calculated pore pressure at this point is 1.86MPa/100m, and the actual measured pressure value at this point is 1.92MPa/100m, which meets the needs of the project. According to the pore pressure of each space point, the pressure contour is drawn to obtain the pressure distribution law.

Claims

1. A method for predicting regional high-pressure saline layer pore pressure using curvature of geological structure surface, comprising the following steps:

1) Find out the top boundary and bottom boundary of the regional salt layer according to the seismic reflection profile and the actual drilled salt layer section, and obtain the regional distribution;

2) Use the trend surface method to calculate the curvature at the bottom of the structural surface, obtain the curvature of each spatial point, and calculate the principal curvature (ρ ₁ , ρ ₂ ), specifically the geographical coordinates ( _xi , y _i ) and the elevation data w _i of the corresponding points use the harmonic trend surface method to establish the elevation equation of the structural map of w=w(x, y), the w=w(x, y) is the deflection of the thin plate, and the equation w _{=w(x, y) Calculate the principal curvature (ρ 1i} _, ρ _2i ) of any point (xi, y _i ) on the structural diagram;

3) Regression statistics of the overburden pressure _σv according to the logging data;

4) Calculate the elastic modulus and Poisson's ratio of the inter-salt sandstone interlayer according to the logging data;

5) Using the principal curvature, elastic modulus and Poisson's ratio at the bottom of the known salt formation plane, determine the principal stress of the formation and establish a pore pressure prediction model, specifically the principal curvature (ρ _1i , ρ _2i ) combined with the elastic modulus and Poisson's ratio of the corresponding formation to calculate the principal stress (σ _1i , σ _2i ) at this point, that is, to obtain the three-dimensional principal stress sequence (σ _1i , σ _2i , σ _vi ), using the rock volume deformation Δv _i at any point during the rock structure deformation process to approximate the rock pore deformation Δv _ki , the pore pressure model p _i = f(ρ _1i , ρ _2i , h) at any point on the salt rock structure surface is obtained, Described h is the depth of investigation point;

6) Calculate the pore pressure, draw the pressure contour according to the pore pressure of each space point, and obtain the pressure distribution law.