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

Abstract

The invention discloses a method for predicting pore pressure of a regional high-pressure saltwater layer by utilizing a curvature of face of geologic structure. The method comprises the following steps of: determining a regional distribution regularity of salt and gypsum layers by utilizing seismic data and actual drilling logging data and constructing a contour map, constructing a regional height equation on the contour map by a harmonic trend surface method and determining the main curvature of any point constructing the region, calculating the main stress of any point, establishing a pore pressure prediction model of any point, and determining the pore pressure of the high-pressure saltwater layer. By the method, the scientific evidence for determining the safe density of drilling liquid is provided in field construction of drilling design so as to effectively prevent collapse of the well walls and avoid underground accidents.

Description

A kind of method of utilizing geological structure face curvature estimation range high pressured slatwater layer pore pressure

Technical field

The present invention relates to a kind of method of utilizing geological structure face curvature estimation range high pressured slatwater layer pore pressure.

Background technology

Construct under salt in the most of oil gas resource set of China, the rock salt strata drilling is the key technology difficult problem of restriction China's oil probing.Constructed the effect of crimp due to stratum, form the abnormal pressure brine layer, area distribution is irregular, frequent and high pressured slatwater layer generation contact battle in drilling process, when the density of drilling fluid can not equilibrium strata pressure, and salt solution can occur will enter pit shaft, pollute drilling fluid, produce drilling failure and complex situations, bring in various degree loss for the human and material resources of drillng operation.For this reason how before drilling well prior forecast high pressured slatwater layer pore pressure be very important, if can predict the high pressured slatwater layer pore pressure before drilling well, in the time of just can determining site operation for Drilling Design, safe drilling fluid density provides the foundation of science, effectively stoping borehole well instability, prevent the generation of down hole problem.

Creator in the present invention relies on it to be engaged in for many years experience and the practice of relevant industries for this reason, and, through concentrating on studies and developing, finally creates a kind of method of utilizing geological structure face curvature estimation range high pressured slatwater layer pore pressure

Summary of the invention

The object of the present invention is to provide a kind of method of utilizing geological structure face curvature estimation range high pressured slatwater layer pore pressure, utilize the method can predict structure realm high pressured slatwater layer pore pressure before drilling well, so that when Drilling Design is determined site operation for determining that safe drilling fluid density provides scientific basis, effectively stoping borehole well instability, prevent the generation of down hole problem.

Utilize the method for geological structure face curvature estimation range high pressured slatwater layer pore pressure in the present invention, include the following step:

1) according to earthquake reflection section and the real salt deposit interval that bores, find out circle, top and the Di Jie of regional salt deposit, obtain area distribution;

2) utilize the trend surface method to calculate the curvature of structural plane bottom, obtain the curvature of each spatial point, calculate principal curvatures (ρ ₁, ρ ₂);

3) return statistics overburden pressure σ according to well-log information _v

4) calculate modulus of elasticity and the poisson's ratio of sand streak between salt according to well-log information;

5) utilize principal curvatures, modulus of elasticity and the poisson's ratio of known salt deposit structural plane bottom, determine the main stress bar on stratum, place, set up the pore pressure prediction model;

6) calculate pore pressure,, according to the pore pressure of each spatial point, make pressure contour, obtain pressure law.

Described step 2) method in is by the geographical coordinate (x on the salt deposit structural contour map _i, y _i) and the altitude data w of respective point _iUtilize mediation trend surface method to set up the elevation equation of the constructional drawing of w=w (x, y), by equation w=w (x, y), calculate any point (x on constructional drawing _i, y _i) principal curvatures (ρ _1i, ρ _2i).

Described step 5) method in is the principal curvatures (ρ by the rock salt structure bottom any point that calculates _1i, ρ _2i) calculate the main stress bar (σ of this point in conjunction with modulus of elasticity, the poisson's ratio on corresponding stratum _1i, σ _2i), i.e. the three-dimensional main stress bar sequence (σ of acquisition prediction stratum any point _1i, σ _2i, σ _vi), utilize arbitrfary point rock volume distortion Δ v in the rock structure deformation process _iBe approximately blowhole distortion Δ v _ki, draw any point pore pressure model p on the rock salt constructing curve _i=f (ρ _1i, ρ _2i, h).

utilizing geological structure face curvature estimation range high pressured slatwater layer pore pressure in the present invention is to determine Regional Distributing Regularity and the structural contour map of saline bed by seismic data and the real log data that bores, the regional elevation equation that utilizes mediation trend surface method to set up on the geological structure isogram is also determined the principal curvatures of structure realm arbitrfary point, calculate the main stress bar of arbitrfary point, set up the pore pressure prediction model of arbitrfary point, determine the pore pressure of high pressured slatwater layer, in order to provide scientific basis for definite safe drilling fluid density when Drilling Design is determined site operation, effectively to stop cave-in, prevent the generation of down hole problem.

Description of drawings

Fig. 1 is estimation range geological structure figure;

Fig. 2 is estimation range high pressured slatwater layer pore pressure distribution map.

The specific embodiment

Below in conjunction with accompanying drawing, the specific embodiment in the present invention is described in further detail.

In very long geological epoch, because the folding movement of the earth's crust bends salt deposit, or because heave of base makes the salt deposit arch, the brine layer that seals between salt is constructed the moulding mobile effect of extruding, lifting and rock salt and is formed abnormal pressure, and the degree of structural deformation and brine layer abnormal pressure have certain contacting.In general, structural deformation Shaoxing opera is strong, and abnormal pressure brine layer pore pressure is larger, and the degree of structural deformation can be described with arbitrfary point curvature on structural plane, and this structure of mechanics of curvature and rock distortion has inner link.Basic Structural Relations of Rocks is to disclose the stressed quantitative description with being out of shape of rock, is wherein comprising as factors such as stratum elastic parameter, formation component, density, buried depth, geological epoch, porosity, tectonic movements.Geological structure curvature can reflect the degree of the suffered external influence in stratum to some extent, therefore utilizes the geological structure face curvature can carry out prediction before drilling zone high pressured slatwater layer pore pressure.

Utilize geological structure face curvature estimation range high pressured slatwater layer pore pressure to comprise the following steps: in the present invention

1. the regional salt deposit regularity of distribution determines

Bore the log data definite area salt deposit regularity of distribution and structrual contour distribution map in estimation range according to earthquake reflection section and reality.

The i.e. degree of depth at the bottom of definite area earthquake reflection section Shang Yanding and salt at first, bore Yan Ding that log data obtains and the degree of depth at the bottom of salt is demarcated according to real simultaneously, sets up the salt deposit regularity of distribution in zone.

2. determine salt deposit geological structure principal curvature of a surface

, according to the regularity of distribution of the salt layer region of delimiting and salt deposit structrual contour Fig. 1 of acquisition, obtain the geographical coordinate (x of the arbitrfary point on the stratigraphic structure isogram _i, y _i) and the altitude data w of respective point _i, utilize mediation trend surface method to set up the elevation equation w=w (x, y) of constructional drawing, calculate arbitrfary point (x on constructional drawing by equation w=w (x, y) _i, y _i) principal curvatures (ρ _1i, ρ _2i), concrete grammar is as follows:

For the convenience on calculating, to establish constructional drawing elevation equation and meet single order fourier series trend surface equation, concrete form is as follows:

w＝a ₀₀+a ₁₀A ₁C ₀+a ₀₁A ₀C ₁+a ₁₁A ₁C ₁+b ₁₀B ₁C ₀ (2.1)

+b ₁₁B ₁C ₁+c ₀₁A ₀D ₁+c ₁₁A ₁D ₁+d ₁₁B ₁D ₁

In single order fourier series trend surface equation, 9 particular factor are arranged; a ₀₀, a ₁₀, a ₀₁, a ₁₁, b ₁₀, b ₁₁, c ₀₁, c ₁₁, d ₁₁In formula:

$A_t=\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">cos</figure-callout>}\frac{2\mathrm{t\&pi;x}}{L},$ $B_t=\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">sin</figure-callout>}\frac{2\mathrm{t\&pi;x}}{L},(t=\mathrm{0,1})$

$C_k=\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">cos</figure-callout>}\frac{2\mathrm{k\&pi;y}}{H},$ $D_k=\sin \frac{2\mathrm{k\&pi;y}}{H},(k=\mathrm{0,1})$

, for obtaining the undetermined coefficient in equation, can, by principle of least square method, be the sum of squares of deviations of each undetermined coefficient to observation and Trend value

$Q=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{(z_i-{\hat{z}}_i)}^2=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}(z_i-a_{00}-a_{10}{A}_1{C}_0-a_{01}{A}_0{C}_1-a_{11}{A}_1{C}_1$

${-b_{10}{B}_1{C}_0-b_{11}{B}_1{C}_1-c_{01}{A}_0{D}_1-c_{11}{A}_1{D}_1-d_{11}{B}_1{D}_1)}^2---\left(2.2\right)$

Partial derivative equal 0, namely

Above-mentioned 9 equations, through arranging the normal equation group that can obtain single order fourier series trend surface, can be write as following matrix form

$\left[\begin{array}{ccccc}\mathrm{\&Sigma;}1& \mathrm{\&Sigma;}{A}_1{C}_0& \mathrm{\&Sigma;}{A}_0{C}_1& \&CenterDot;\&CenterDot;\&CenterDot;& \mathrm{\&Sigma;}{B}_1{D}_1\\ \mathrm{\&Sigma;}{A}_1{C}_0& \mathrm{\&Sigma;}{\left(A_1{C}_0\right)}^2& \mathrm{\&Sigma;}{A}_1{C}_0{A}_0{C}_1& \&CenterDot;\&CenterDot;\&CenterDot;& \mathrm{\&Sigma;}{A}_1{C}_0{B}_1{D}_1\\ \mathrm{\&Sigma;}{A}_0{C}_1& \mathrm{\&Sigma;}{A}_0{C}_1{A}_1{C}_0& \mathrm{\&Sigma;}{\left(A_0{C}_1\right)}^2& \&CenterDot;\&CenterDot;\&CenterDot;& \mathrm{\&Sigma;}{A}_0{C}_1{B}_1{D}_1\\ \mathrm{\&Sigma;}{A}_1{C}_1& \mathrm{\&Sigma;}{A}_1{C}_1{A}_1{C}_0& \mathrm{\&Sigma;}{A}_1{C}_1{A}_0{C}_1& \&CenterDot;\&CenterDot;\&CenterDot;& \mathrm{\&Sigma;}{A}_1{C}_1{B}_1{D}_1\\ \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;\\ \mathrm{\&Sigma;}{B}_1{D}_1& \mathrm{\&Sigma;}{B}_1{D}_1{A}_1{C}_0& \mathrm{\&Sigma;}{B}_1{D}_1{A}_0{C}_1& \&CenterDot;\&CenterDot;\&CenterDot;& \mathrm{\&Sigma;}{\left(B_1{D}_1\right)}^2\end{array}\right]\left[\begin{array}{c}{a}_{00}\\ a_{10}\\ a_{01}\\ a_{11}\\ \\ d_{11}\end{array}\right]=\left[\begin{array}{c}\mathrm{\&Sigma;}\\ \mathrm{\&Sigma;z}{A}_1{C}_0\\ \mathrm{\&Sigma;z}{A}_0{C}_1\\ \mathrm{\&Sigma;z}{A}_1{C}_1\\ \&CenterDot;\&CenterDot;\&CenterDot;\\ \mathrm{\&Sigma;z}{B}_1{D}_1\end{array}\right]---\left(2.4\right)$

Can solve undetermined coefficient in formula (2.1) by formula (2.1).

According to each point coordinates (x on constructional drawing _i, y _i) and altitude data w _i, can set up and just return equation

$\left[\begin{array}{ccccccc}N& \mathrm{\&Sigma;x}& \mathrm{\&Sigma;y}& \mathrm{\&Sigma;}{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">x</figure-callout>}}^2& \mathrm{\&Sigma;xy}& \mathrm{\&Sigma;}{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">y</figure-callout>}}^2& \&CenterDot;\&CenterDot;\&CenterDot;\\ \mathrm{\&Sigma;x}& \mathrm{\&Sigma;}{x}^2& \mathrm{\&Sigma;xy}& \mathrm{\&Sigma;}{x}^3& \mathrm{\&Sigma;}{x}^{2}y& \mathrm{\&Sigma;}{\mathrm{<figure-callout\; id="2"\; label="xy"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">xy</figure-callout>}}^2& \&CenterDot;\&CenterDot;\&CenterDot;\\ \mathrm{\&Sigma;y}& \mathrm{\&Sigma;xy}& \mathrm{\&Sigma;}{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">y</figure-callout>}}^2& \mathrm{\&Sigma;}{x}^{2}y& \mathrm{\&Sigma;}{\mathrm{<figure-callout\; id="2"\; label="xy"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">xy</figure-callout>}}^2& \mathrm{\&Sigma;}{y}^3& \&CenterDot;\&CenterDot;\&CenterDot;\\ \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \\ \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;\\ \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \&CenterDot;& \end{array}\right]\left[\begin{array}{c}{c}_{00}\\ c_{10}\\ c_{01}\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\end{array}\right]=\left[\begin{array}{c}\mathrm{\&Sigma;w}\\ \mathrm{\&Sigma;xw}\\ \mathrm{\&Sigma;yw}\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\end{array}\right]---\left(2.5\right)$

In formula, N is for always counting, and w is absolute elevation, solves c ₀₀, c ₁₀, c ₀₁, c ₂₀, c ₁₁, Deng coefficient, obtain the approximate expression of w (x, y).

Theoretical according to the thin plate minor deflection bending, because w is small, in thin plate, face is being expressed as that the curvature of x and y direction and the rate of turning round can be similar to:

$\frac{1}{r_x}=-z\frac{{\&PartialD;}^{2}w}{{\&PartialD;x}^2},$ $\frac{1}{r_y}=-z\frac{{\&PartialD;}^{2}w}{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">y</figure-callout>}}^2},$ $\frac{1}{r_{\mathrm{xy}}}=-z\frac{{\&PartialD;}^{2}w}{\&PartialD;x\&PartialD;y}---\left(2.6\right)$

(2.1) formula of utilization is obtained three second-order partial differential coefficients of arbitrfary point on constructional drawing

With

Can calculate the curvature of arbitrfary point on constructing curve

Calculate accordingly principal curvatures and the principal direction of arbitrfary point on structural plane.Principal direction can be by formula:

$\tan \left(2{\mathrm{\&alpha;}}_i\right)=\frac{-1/r_{\mathrm{xyi}}}{0.5(1/r_{\mathrm{xi}}-1{/r}_{\mathrm{yi}})}---\left(2.7\right)$

Determine.Wherein, α _iAngle for principal direction and x axle.On constructing curve, the design formulas of arbitrfary point principal curvatures is

$\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">r</figure-callout>}}_{\mathrm{1,2}}}=\frac{1}{2}(\frac{1}{r_{\mathrm{xi}}}+\frac{1}{r_{\mathrm{yi}}})\&PlusMinus;\sqrt{\frac{1}{4}{(\frac{1}{r_{\mathrm{xi}}}-\frac{1}{r_{\mathrm{yi}}})}^2+{\left(\frac{1}{r_{\mathrm{xyi}}}\right)}^2}---\left(2.8\right)$

Namely ${\mathrm{\&rho;}}_{1i}=\frac{1}{r_1},$ ${\mathrm{\&rho;}}_{2i}=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}.$

3. return statistics overburden pressure σ according to well-log information _v

Density log and acoustic logging can reflect the formation compaction rule intuitively, and can obtain the rock volume density value.Easily be subject to size and the impact of instrument detection level of hole diameter due to the density log data, before utilizing the density log data, should filter out non-True Data in conjunction with the calliper log data, to obtain reliable density, and utilize the loose point of these density data, utilize formula (3.1) to calculate the overburden pressure gradient:

$G_z^i=\frac{{\mathrm{\&rho;}}_w{H}_w+{\mathrm{\&rho;}}_0{H}_0+\underset{i}{\mathrm{\&Sigma;}}{\mathrm{\&rho;}}_i{\mathrm{dh}}_i}{H_w+H_w+\underset{i}{\mathrm{\&Sigma;}}{\mathrm{dh}}_i}---\left(3.1\right)$

In formula

For the overburden pressure gradient of arbitrfary point i, g/cm ³ρ _w, H _wBe respectively density and the depth of water of formation water, g/cm ³, m; ρ ₀, H ₀Be respectively averag density and the well depth of top without the density log data segment, g/cm ³, m; ρ _i, dh _iFor density log data and the well logging interval thickness corresponding with it, g/cm ³, m.

After the loose point of the density that is calculated by log data is obtained the overburden pressure gradient data,, by data regression, can obtain the statistical law of overburden pressure.Consider power law and the lower defect of binomial regression model precision, the cubic polynomial of employing formula (3.2) form returns:

G _z＝a ₀+a ₁h+a ₂h ²+a ₃h ³ (3.2)

G in formula _zFor overburden pressure gradient, g/cm ³H is for investigating the degree of depth of point, m; a ₀, a ₁, a ₂, a ₃For regression coefficient undetermined.The overburden pressure that is arbitrfary point on constructing curve is:

σ _vi＝G _Zh _i (3.3)

4. calculate modulus of elasticity and the poisson's ratio on prediction stratum according to well-log information

Modulus of elasticity and the poisson's ratio on stratum are obtained by logging data interpretation, and concrete steps are as follows:

(1) calculate the dynamic modulus of elasticity

And dynamic Poisson's ratio

$E_d^i=\frac{{\mathrm{\&rho;}}^i{v}_s^{i^2}(3v_p^{i^2}-4v_s^{i^2})}{v_p^{i^2}-2v_s^{i^2}}---\left(4.1\right)$

${\mathrm{\&mu;}}_d^i=\frac{v_p^{i^2}-2v_s^{{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">i</figure-callout>}}^2}}{2(v_p^{i^2}-v_s^{i^2})}$

In formula:

$v_s^i=\sqrt{11.44v_p^i+18.03}-5.866$

$v_p^i=0.001v_{\mathrm{ac}}^i$

(2) determine static modulus of elasticity With static poisson's ratio

$E_s^i=a_1+b_1{E}_d^i---\left(4.2\right)$

${\mathrm{\&mu;}}_s^i=a_2+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">b</figure-callout>}}_2{\mathrm{\&mu;}}_d^i$

In formula: a ₁, b ₁, a ₂And b ₂For coefficient, depending on concrete regional value.

5. set up high pressured slatwater layer pore pressure prediction model

Principal curvatures (ρ by the rock salt structure bottom any point that calculates _1i, ρ _2i) calculate the main stress bar (σ of this point in conjunction with modulus of elasticity, the poisson's ratio on corresponding rock salt stratum _1i, σ _2i), namely obtain the three-dimensional main stress bar sequence (σ of salt deposit any point _1i, σ _2i, σ _vi), utilize arbitrfary point rock volume distortion Δ v in the rock structure deformation process _iBe approximately blowhole distortion Δ v _ki, draw any point pore pressure model p on the rock salt constructing curve _i=f (ρ _1i, ρ _2i, h).

Concrete steps are as follows:

(1) on rock salt geological structure curved surface, arbitrfary point three-dimensional main stress bar calculates

Theoretical according to the thin plate minor deflection bending, in plate, the strain of any is:

${\mathrm{\&epsiv;}}_x=-z\frac{{\&PartialD;}^{2}w}{{\&PartialD;x}^2},$ ${\mathrm{\&epsiv;}}_y=-z\frac{{\&PartialD;}^{2}w}{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HSA00000235273100011.png"\; state="\{\{state\}\}">y</figure-callout>}}^2},$ ${\mathrm{\&epsiv;}}_{\mathrm{xy}}=-z\frac{{\&PartialD;}^{2}w}{\&PartialD;x\&PartialD;y}---\left(5.1\right)$

In formula: w=w (x, y) is the amount of deflection of thin plate.

Because formula (2.3) and (5.1) can obtain

${\mathrm{\&epsiv;}}_x=z\frac{1}{r_x},$ ${\mathrm{\&epsiv;}}_y=z\frac{1}{r_y},$ ${\mathrm{\&epsiv;}}_{\mathrm{xy}}=z\frac{1}{r_{\mathrm{xy}}}---\left(5.2\right)$

The stress components of arbitrfary point are

${\mathrm{\&sigma;}}_x=\frac{E}{1-{\mathrm{\&mu;}}^2}({\mathrm{\&epsiv;}}_x+{\mathrm{\&mu;\&epsiv;}}_y)=\frac{\mathrm{Ez}}{1-{\mathrm{\&mu;}}^2}(\frac{1}{r_x}+\mathrm{\&mu;}\frac{1}{r_y})$

${\mathrm{\&sigma;}}_y=\frac{E}{1-{\mathrm{\&mu;}}^2}({\mathrm{\&epsiv;}}_y+{\mathrm{\&mu;\&epsiv;}}_x)=\frac{\mathrm{Ez}}{1-{\mathrm{\&mu;}}^2}(\frac{1}{r_y}+\mathrm{\&mu;}\frac{1}{r_x})---\left(5.3\right)$

${\mathrm{\&tau;}}_{\mathrm{xy}}=\frac{E}{2(1+\mathrm{\&mu;})}{r}_{\mathrm{xy}}=\frac{\mathrm{Ez}}{1+\mathrm{\&mu;}}\frac{1}{r_{\mathrm{xy}}}$

In formula, E, μ are respectively modulus of elasticity and poisson's ratio.

By the 3rd formula in (5.3), if x and y are any two principal directions, τ _xy=0, thereby , so x and y are also two principals direction of curvature of this point, illustrate that on the thin plate elastic surface, principal direction of stress and the principal direction of curvature of any is consistent.

For arbitrary cross section of twisted plate, the normal stress maximum value appears on the plate face of protuberance one side Thereby on the plate face, the main stress bar of any is

${\mathrm{\&sigma;}}_{1i}=\frac{{\mathrm{Eh}}_i}{2(1-{\mathrm{\&mu;}}^2)}(\frac{1}{r_{1i}}+\mathrm{\&mu;}\frac{1}{r_{2i}})---\left(5.4\right)$

${\mathrm{\&sigma;}}_{2i}=\frac{{\mathrm{Eh}}_i}{2(1-{\mathrm{\&mu;}}^2)}(\frac{1}{r_{2i}}+\mathrm{\&mu;}\frac{1}{r_{1i}})$

(2) foundation of high pressured slatwater layer pore pressure prediction model

After rock was subjected to effect of stress, a part was born (being pore pressure) by the fluid in blowhole, and a part is born (being effective stress) by the skeleton of rock.To be subject to mean stress be σ if rock is sealing not under drainage situation arbitrfary point _iThe three-dimensional stress effect, its mean effective stress σ _0iWith pore pressure P _piPass be:

${\mathrm{\&sigma;}}_{0i}=\mathrm{\&sigma;}-P_{\mathrm{pi}}=\frac{1}{3}({\mathrm{\&sigma;}}_{i1}+{\mathrm{\&sigma;}}_{2i}+{\mathrm{\&sigma;}}_{\mathrm{vi}})-P_{\mathrm{pi}}---\left(5.5\right)$

According to elastic theory, the volumetric change of arbitrfary point rock is under effect of stress:

$\mathrm{\&Delta;}{V}_i=\frac{V({\mathrm{\&sigma;}}_{0i}-P_{\mathrm{Pi}})}{K_i}---\left(5.6\right)$

The volumetric change that Fluid in Pore occurs is:

$\mathrm{\&Delta;}{V}_{\mathrm{Vi}}=\frac{n_i{P}_{\mathrm{Pi}}V}{K_{\mathrm{vi}}}---\left(5.7\right)$

In formula, n _iFor rock porosity, K _viCoefficient of cubical compressibility for hole.

Because the rock matrix volume compression that diagenesis is later is very little, the volumetric change of rock is approximately equal to the volumetric change of hole, Δ V _i=Δ V _ViSo:

$\frac{P_{\mathrm{Pi}}}{{\mathrm{\&sigma;}}_{0i}}=\frac{1}{1+\frac{n_i{K}_i}{K_{\mathrm{Vi}}}}=B_i---\left(5.8\right)$

In formula, B _iFor pore pressure coefficient.

Simultaneous formula (3.3), (5.6), (5.7) and (5.8) obtain high pressured slatwater layer pore pressure prediction model:

$p_{\mathrm{pi}}=\frac{B_i{E}_i{h}_i}{6(1-{\mathrm{\&mu;}}_i)}[\frac{1}{r_i}+\frac{2(1-{\mathrm{\&mu;}}_i)}{E_i{h}_i}{\mathrm{\&sigma;}}_{\mathrm{vi}}]---\left(5.9\right)$

Define in formula For equivalent curvature.

6. calculate the high pressured slatwater layer pore pressure

Bring the curvature of the arbitrfary point on the geological structure face in zone to be predicted into step 5) in forecast model, construct curvature 0.0208 as certain and 4464.72m, level is maximum, minimum and overlying rock geostatic stress are respectively 116.06,83.48 and 112.94MPa, calculate the pore pressure 1.86MPa/100m of this place, survey this point pressure numerical pressure numerical value 1.92MPa/100m, meet requirement of engineering.According to the pore pressure of each spatial point, make pressure contour, obtain pressure law.

Claims (1)

1. a method of utilizing geological structure face curvature estimation range high pressured slatwater layer pore pressure, comprise the following steps:

1) according to earthquake reflection section and the real salt deposit interval that bores, find out circle, top and the Di Jie of regional salt deposit, obtain area distribution;

2) utilize the trend surface method to calculate the curvature of structural plane bottom, obtain the curvature of each spatial point, calculate principal curvatures (ρ ₁, ρ ₂), be specially by the geographical coordinate (x on the salt deposit structural contour map _i, y _i) and the altitude data w of respective point _iUtilize mediation trend surface method to set up the elevation equation of the constructional drawing of w=w (x, y), described w=w (x, y) is the amount of deflection of thin plate, by equation w=w (x, y), calculates any point (x on constructional drawing _i, y _i) principal curvatures (ρ _1i, ρ _2i);

3) return statistics overburden pressure σ according to well-log information _v

4) calculate modulus of elasticity and the poisson's ratio of sand streak between salt according to well-log information;

5) utilize principal curvatures, modulus of elasticity and the poisson's ratio of known salt deposit structural plane bottom, determine the main stress bar on stratum, place, set up the pore pressure prediction model, be specially the principal curvatures (ρ by the rock salt structure bottom any point that calculates _1i, ρ _2i) calculate the main stress bar (σ of this point in conjunction with modulus of elasticity, the poisson's ratio on corresponding stratum _1i, σ _2i), i.e. the three-dimensional main stress bar sequence (σ of acquisition prediction stratum any point _1i, σ _2i, σ _vi), utilize arbitrfary point rock volume distortion Δ v in the rock structure deformation process _iBe approximately blowhole distortion Δ v _ki, draw any point pore pressure model p on the rock salt constructing curve _i=f (ρ _1i, ρ _2i, h), described h is for investigating the degree of depth of point;

6) calculate pore pressure,, according to the pore pressure of each spatial point, make pressure contour, obtain pressure law.

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