CN106202879A - P-and s-wave velocity dynamic estimation method during carbon dioxide drive - Google Patents

Abstract

The present invention provides a kind of p-and s-wave velocity dynamic estimation method during carbon dioxide drive, including: the existing basic data of utilization and experimental data obtain the total porosity after displacement and pore components；K T equation is utilized to respectively obtain rock matrix bulk modulus and the modulus of shearing of different oil gas water content；The natural impedance amount version of different oily water saturation is set up based on experiment and seismic data；Fluid-mixing bulk modulus during calculating secondary earthquake-capturing and fluid-mixing density；The change formula utilizing pressure influence porosity and pore components obtains matrix density, bulk modulus and modulus of shearing during secondary earthquake-capturing；P-and s-wave velocity when utilizing Xu White model to obtain earthquake-capturing.During this carbon dioxide drive, p-and s-wave velocity dynamic estimation method utilizes porosity and the pore components improved model of change, so as to improving p-and s-wave velocity precision of prediction, it is achieved that p-and s-wave velocity dynamic estimation during carbon dioxide drive.

Description

Dynamic estimation method for longitudinal and transverse wave speeds in carbon dioxide flooding process

Technical Field

The invention relates to the field of exploration geophysics, in particular to a dynamic estimation method for longitudinal and transverse wave speeds in a carbon dioxide flooding process.

Background

The traditional longitudinal and transverse wave prediction method is based on conventional well logging, rock core and test data, through well logging constraint, different rock physical models are used for solving the elastic modulus of a rock skeleton, and the properties and the saturation of pore fluid are combined with a Gassmann equation to estimate the longitudinal and transverse wave speed. The longitudinal and transverse wave speeds estimated by the method are static, and the method is suitable for estimation before displacement and not suitable for estimation of longitudinal and transverse waves after displacement. Therefore, a novel method for dynamically estimating the longitudinal and transverse wave speeds in the carbon dioxide flooding process is invented, and the technical problems are solved.

Disclosure of Invention

The invention aims to provide a dynamic estimation method for longitudinal and transverse wave speeds in a carbon dioxide flooding process, which considers the influence of the change of a rock framework and fluid after the flooding on the longitudinal and transverse wave speeds.

The object of the invention can be achieved by the following technical measures: the dynamic estimation method of the longitudinal and transverse wave speeds in the carbon dioxide flooding process comprises the following steps: step 1, obtaining total porosity and pore aspect ratio after displacement by using existing basic data and experimental data; step 2, respectively obtaining the volume modulus and the shear modulus of the rock skeleton with different oil, gas and water contents by using a K-T equation; step 3, establishing wave impedance quantity versions of different oil-gas-water saturation degrees based on experiments and seismic data; step 4, throwing the wave impedance data at the well point into a wave impedance quantity plate to obtain the oil-gas-water saturation during secondary seismic acquisition, and further calculating the bulk modulus and density of the mixed fluid during secondary seismic acquisition; step 5, obtaining the rock skeleton density, the volume modulus and the shear modulus during secondary seismic acquisition by using a change formula of the pressure influence porosity and the pore aspect ratio; and 6, obtaining longitudinal and transverse wave velocities during seismic acquisition by using the Xu-White model.

The object of the invention can also be achieved by the following technical measures:

in step 1, the total porosity of the rock after carbon dioxide displacement can be calculated by using the existing effective overburden pressure, porosity and pore aspect ratio formulas measured by temperature, pressure, well logging and experimentsAnd pore aspect ratios p, q.

1 in step 2, the results calculated in step 1 are utilized, the rock matrix density rho m, the rock matrix volume modulus Km and the shear modulus mum are measured by combining experiments, the rock framework volume modulus and the shear modulus Kd and μ d with different oil, gas and water contents are respectively obtained by utilizing a K-T equation, and the K-T equation is as follows:

K_d(Φ)＝K_m(1-Φ)^pμ_d(Φ)＝μ_m(1-Φ)^q

$\begin{array}{cc}p=\frac{1}{3}\underset{l=s,c}{\Σ}{v}_{l}Tiijj\left({\mathrm{\α}}_l\right)& q=\frac{1}{5}\underset{l=s,c}{\Σ}{v}_{l}F\left({\mathrm{\α}}_l\right)\end{array}$

wherein,denotes a porosity ofThe bulk modulus of the dry rock, Km is the bulk modulus of the solid minerals that make up the rock,denotes a porosity ofThe shear modulus of dry rock, μm being the shear modulus of the solid minerals that make up the rock,for total rock porosity, p and q are coefficients related to rock porosity flattening and not porosity, vl is the volume percent of sand or mud, Tiijj (α l) and F (α l) are functions related to pore aspect ratio, s is sand, and c is mud.

1 in step 3, calculating the bulk modulus Kf of the mixed fluid by using a Wood-huge-hill formula and a density formula:

$\frac{1}{K_f}=\frac{S_o}{K_o}+\frac{S_g}{K_g}+\frac{S_w}{K_w}$

in the formula: ko, Kg, Kw and Kf are respectively the bulk modulus of oil, gas and water and the bulk modulus of the mixed fluid; so, Sg and Sw are respectively oil-containing, gas-containing and water-containing saturation;

obtaining the density of the mixed fluid and the rock density of the final contained fluid by using a density formula

${\mathrm{\ρ}}_r=S_o{\mathrm{\ρ}}_o+S_g{\mathrm{\ρ}}_g+(1-S_o-S_g){\mathrm{\ρ}}_w$

In the formula: ρ is the density of the rock containing the fluid, ρ_fFor the density of the mixed fluid, rho is the density of the oil, rho_gIs the density of gas, p_wIs the density of water, p_dIs the density of the rock skeleton, So is the saturation, S_gIn order to be at a gas saturation level,is porosity;

obtaining longitudinal wave velocity Vp and longitudinal wave impedance value rho V when different oil, gas and water contents are obtained by utilizing a Gasmann equation and a velocity equation, wherein the formula is as follows:

μ_sat＝μ_d

$\begin{array}{cc}{V}_p=\sqrt{\frac{K_{sat}+\frac{4{\mathrm{\μ}}_{sat}}{3}}{{\mathrm{\ρ}}_{sat}}}& Vs=\sqrt{\frac{{\mathrm{\μ}}_{sat}}{{\mathrm{\ρ}}_{sat}}}\end{array}$

wherein K_satRock bulk modulus, K, for saturated media_dIs the bulk modulus of the rock skeleton, K_fFor mixed fluid bulk modulus, K_mIs a baseMass bulk modulus, μ_satShear modulus of saturated medium, mu_dIs the shear modulus of the rock skeleton, ρ_satThe density of the rock is the saturated medium,is porosity;

and (4) putting the calculated wave impedance result into a wave impedance and oil saturation measurement board established by experiments and seismic data to obtain oil saturation, water saturation and gas saturation.

1 in step 6, the results of step 4 and step 5 are integrated, the Gassmann equation is used again to calculate the volume modulus and shear modulus Ksat and mu sat of the fluid rock, and the velocity formula can be used to obtain the longitudinal wave velocity V during the secondary seismic acquisition_pAnd a transverse wave velocity Vs.

Research shows that the longitudinal and transverse wave speeds are in constraint connection with the matrix properties, the shale content, the porosity and the pore shape, and the porosity and the pore shape are changed in the oil displacement process. Reservoir due to CO injection₂The temperature, pressure, saturation of pore fluid, formation water mineralization, porosity, pore shape and the like of the reservoir are greatly changed. These changes are manifested in the elastic characteristics of the reservoir as changes in longitudinal and transverse wave velocities, density. In the carbon dioxide flooding process, along with the increase of the content of carbon dioxide, the oil saturation, the gas saturation and the water saturation can be correspondingly changed. Under the influence of carbon dioxide injection, the internal pressure of a reservoir changes, the porosity of the reservoir and the shape of pores correspondingly change, and therefore the elastic modulus of dry rock changes. The present invention improves the model based on this principle by using varying porosity and pore aspect ratio to improve the accuracy of the compressional-compressional velocity prediction. The method of the invention realizes dynamic estimation of longitudinal and transverse wave speeds in the carbon dioxide flooding process for the first time.

Drawings

FIG. 1 is a flow chart of an embodiment of a method for dynamically estimating longitudinal and transverse wave velocities during carbon dioxide flooding in accordance with the present invention;

FIG. 2 is a graph of pressure versus porosity in an embodiment of the present invention;

FIG. 3 is a graph of porosity versus pore aspect ratio in an embodiment of the present invention;

FIG. 4 is a diagram of wave impedance magnitude for different oil, gas, and water saturations in an embodiment of the invention;

FIG. 5 is a graph illustrating the velocity of a longitudinal wave and a transverse wave after displacement, in accordance with an embodiment of the present invention.

Detailed Description

And selecting a proper model according to the actual condition of the work area, and estimating and verifying the applicability of the model by utilizing a traditional method for longitudinal and transverse waves before displacement. The Xu-White model comprehensively considers the influence of matrix properties, shale content, porosity size and pore shape in rocks and the property of pore containing fluid on the speed, and has clear physical significance.

As shown in fig. 1, fig. 1 is a flow chart of a method for dynamically estimating longitudinal and transverse wave velocities in a carbon dioxide flooding process according to the present invention.

Step 101, under the influence of carbon dioxide injection, not only the fluid in the reservoir will change, but also the porosity and pore shape of the reservoir will change correspondingly, thereby causing the elastic modulus of the rock to change. The total porosity of the rock after carbon dioxide displacement can be calculated by using the existing effective overburden pressure, porosity and pore aspect ratio formulas measured by temperature, pressure, well logging and experimentsAnd pore aspect ratios p, q.

And step 102, measuring the density rho m of the rock matrix, the volume modulus Km and the shear modulus mum of the rock matrix by using the result calculated in the step 101 and combining experiments, and respectively obtaining the volume modulus Kd and the shear modulus mum of the rock framework with different oil, gas and water contents by using a K-T equation. The calculation of the change of the rock skeleton in different oil displacement stages is completed through the steps 101 and 102. The K-T equation is as follows:

K_d(Φ)＝K_m(1-Φ)^pμ_d(Φ)＝μ_m(1-Φ)^q

$\begin{array}{cc}p=\frac{1}{3}\underset{l=s,c}{\Σ}{v}_{l}Tiijj\left({\mathrm{\α}}_l\right)& q=\frac{1}{5}\underset{l=s,c}{\Σ}{v}_{l}F\left({\mathrm{\α}}_l\right)\end{array}$

wherein,denotes a porosity ofThe bulk modulus of the dry rock, Km is the bulk modulus of the solid minerals that make up the rock,denotes a porosity ofThe shear modulus of dry rock, μm being the shear modulus of the solid minerals that make up the rock,for total rock porosity, p and q are coefficients related to rock porosity flattening and not porosity, vl is the volume percent of sand or mud, Tiijj (α l) and F (α l) are functions related to pore aspect ratio, s is sand, and c is mud.

In step 103, no matter whether the porosity is large or small, the impedance change of the longitudinal wave caused after displacement is obviously larger than the change of the velocity of the longitudinal wave, that is, the impedance value of the longitudinal wave is more sensitive to the change of the property of the fluid in the pores, and the impedance of the transverse wave is less influenced by the change of the fluid. The injected CO can be known by the statistical analysis of the liquid outlet conditions of a plurality of production wells in the research area₂Only underground oil is displaced and not underground water. Therefore, the measurement version of longitudinal wave impedance and oil saturation can be established through experiments, and the measurement version is verified by utilizing the wave impedance and the oil saturation during one-time seismic acquisition, so that the change of fluid in a reservoir in the displacement process is predicted.

Calculating the bulk modulus (Kf) of the mixed fluid by using a Wood-huge-hill formula and a density formula:

$\frac{1}{K_f}=\frac{S_o}{K_o}+\frac{S_g}{K_g}+\frac{S_w}{K_w}$

in the formula: ko, Kg, Kw and Kf are respectively the bulk modulus of oil, gas and water and the bulk modulus of the mixed fluid; so, Sg and Sw are respectively oil, gas and water saturation.

Obtaining the density of the mixed fluid and the rock density of the final contained fluid by using a density formula

${\mathrm{\ρ}}_r=S_o{\mathrm{\ρ}}_o+S_g{\mathrm{\ρ}}_g+(1-S_o-S_g){\mathrm{\ρ}}_w$

In the formula: ρ is the density of the rock containing the fluid, ρ_fFor the density of the mixed fluid, rho is the density of the oil, rho_gIs the density of gas, p_wIs the density of water, p_dIs the density of the rock skeleton, So is the saturation, S_gIn order to be at a gas saturation level,is porosity.

Therefore, the longitudinal wave velocity Vp and the longitudinal wave impedance value rho V of different oil, gas and water contents are obtained by combining the results obtained in the step 101 and the step 102 and utilizing a Gasmann equation and a velocity equation. The formula is as follows:

μ_sat＝μ_d

$\begin{array}{cc}{V}_p=\sqrt{\frac{K_{sat}+\frac{4{\mathrm{\μ}}_{sat}}{3}}{{\mathrm{\ρ}}_{sat}}}& Vs=\sqrt{\frac{{\mathrm{\μ}}_{sat}}{{\mathrm{\ρ}}_{sat}}}\end{array}$

wherein K_satRock bulk modulus, K, for saturated media_dIs the bulk modulus of the rock skeleton, K_fFor mixed fluid bulk modulus, K_mIs the matrix bulk modulus, μ_satShear modulus of saturated medium, mu_dIs the shear modulus of the rock skeleton, ρ_satThe density of the rock is the saturated medium,is porosity. And (4) putting the calculated wave impedance result into a wave impedance and oil saturation measurement board established by experiments and seismic data to obtain oil saturation, water saturation and gas saturation.

104, obtaining a longitudinal wave impedance value rho V at the well point through inversion processing of the wave impedance of the secondary acquisition seismic data, and throwing the longitudinal wave impedance value rho V into the volume plate of which the wave impedance changes along with the oil-containing saturation established in the step 103, thereby obtaining the oil, gas and water saturation S during the secondary acquisition of the seismic data_o、S_g、S_wAnd then the bulk modulus and density K of the mixed fluid during secondary seismic acquisition can be calculated_f、ρ_f。

Step 105, knowing the porosity and the pore aspect ratio after the combination of the overburden effective pressure and the displacement during the secondary seismic acquisition, calculating the density, the bulk modulus and the shear modulus rho of the rock framework during the secondary seismic acquisition according to a density formula and a K-T equation_d、K_d、μ_d。

Step 106, integrating the results of step 104 and step 105, and calculating the bulk modulus and shear modulus K of the rock containing fluid by using Gassmann's equation again_sat、μ_satThe velocity formula can obtain the longitudinal wave velocity V of the secondary seismic acquisition_pTransverse wave velocity V_s。

FIG. 2 is a graph of pressure versus porosity in an embodiment of the present invention; as shown in the figure, the pore compressibility test shows that the effective overburden pressure has good linear correlation with the formation porosity, and the correlation coefficient is very high and is more than 0.9994. Thus, post-displacement porosity can be calculated from the change in effective overburden pressure and pre-displacement porosity.

FIG. 3 is a graph of porosity versus pore aspect ratio in an embodiment of the present invention; figure 3 shows that there is a linear relationship between sandstone pore aspect ratio and porosity, and the use of varying pore aspect ratio is an important improvement over the use of the Xu-White model in argillaceous sandstones.

FIG. 4 is a diagram of wave impedance magnitude for different oil, gas, and water saturations in an embodiment of the invention; whether the porosity is large or small, the impedance change of the longitudinal wave caused after displacement is obviously larger than the change of the velocity of the longitudinal wave, namely the impedance value of the longitudinal wave is more sensitive to the change of the properties of the fluid in the pores, and the impedance of the transverse wave is less influenced by the change of the fluid. According to statistics of the liquid outlet condition of the production well, the injected carbon dioxide only displaces underground oil and does not displace underground water. Therefore, the change of the fluid in the reservoir during the displacement process can be predicted by establishing the quantity version of the longitudinal wave impedance and the oil saturation, and the oil saturation So, the gas saturation Sg and the water saturation Sw are obtained respectively.

FIG. 5 is a graph illustrating the velocity of a longitudinal wave and a transverse wave after displacement, in accordance with an embodiment of the present invention. As shown in the figure, the difference between the prediction result of the longitudinal wave and the transverse wave before displacement and the actually measured result is small, the change of the velocity of the longitudinal wave and the transverse wave of the reservoir section after displacement is obvious, the change of the velocity of the longitudinal wave is larger than that of the transverse wave, and the change of the velocity of the longitudinal wave and the transverse wave of the non-reservoir section co2 before and after displacement is not obvious. The method is also consistent with the gas-oil displacement rule, and the accuracy of the predicted transverse wave speed is reflected.

The invention relates to a dynamic estimation method of longitudinal and transverse wave speeds in the carbon dioxide flooding process, which utilizes pressure data, petrophysical data Kf, rho f, Km, mum and rho m measured by experiments, and total porosity and pore aspect ratio after displacement to calculate rock frameworks Kd and μ d with different oil, gas and water contents under different pressure conditions through a K-T equation. And then, projecting wave impedance data at the well point into the measurement plate to obtain the hydrocarbon water saturation during secondary seismic acquisition, further calculating Kf and rho f during the secondary seismic acquisition, then obtaining Kd, mu d and rho d during the secondary seismic acquisition through a formula of pressure, porosity and pore aspect ratio, and finally obtaining the longitudinal and transverse wave velocity during the seismic acquisition based on the Xu-White equation.

Claims (5)

1. The dynamic estimation method of the longitudinal and transverse wave speeds in the carbon dioxide flooding process is characterized by comprising the following steps:

step 1, obtaining total porosity and pore aspect ratio after displacement by using existing basic data and experimental data;

step 2, respectively obtaining the volume modulus and the shear modulus of the rock skeleton with different oil, gas and water contents by using a K-T equation;

step 3, establishing wave impedance quantity versions of different oil-gas-water saturation degrees based on experiments and seismic data;

step 4, throwing the wave impedance data at the well point into a wave impedance quantity plate to obtain the oil-gas-water saturation during secondary seismic acquisition, and further calculating the bulk modulus and density of the mixed fluid during secondary seismic acquisition;

step 5, obtaining the rock skeleton density, the volume modulus and the shear modulus during secondary seismic acquisition by using a change formula of the pressure influence porosity and the pore aspect ratio;

and 6, obtaining longitudinal and transverse wave velocities during seismic acquisition by using the Xu-White model.

2. The method for dynamically estimating longitudinal and transverse wave velocities in the carbon dioxide flooding process according to claim 1, wherein in the step 1, the total porosity of the rock after carbon dioxide flooding can be calculated by using the existing formulas of effective overburden pressure, porosity and pore aspect ratio measured by temperature, pressure, well logging and experimentsAnd pore aspect ratios p, q.

3. The method for dynamically estimating the longitudinal and transverse wave velocities in the carbon dioxide flooding process according to claim 1, wherein in step 2, the rock matrix density ρ m, the rock matrix bulk modulus Km and the shear modulus μm of data are measured by combining experiments by using the results calculated in step 1, and the rock framework bulk modulus and the shear modulus Kd and μ d with different oil, gas and water contents are respectively obtained by using a K-T equation as follows:

K_d(Φ)＝K_m(1-Φ)^pμ_d(Φ)＝μ_m(1-Φ)^q

$\begin{array}{cc}p=\frac{1}{3}\underset{l=s,c}{\Σ}{v}_{l}Tiijj\left({\mathrm{\α}}_l\right)& q=\frac{1}{5}\underset{l=s,c}{\Σ}{v}_{l}F\left({\mathrm{\α}}_l\right)\end{array}$

wherein,denotes a porosity ofThe bulk modulus of the dry rock, Km is the bulk modulus of the solid minerals that make up the rock,denotes a porosity ofThe shear modulus of dry rock, μm being the shear modulus of the solid minerals that make up the rock,for total rock porosity, p and q are coefficients related to rock porosity flattening and not porosity, vl is the volume percent of sand or mud, Tiijj (α l) and F (α l) are functions related to pore aspect ratio, s is sand, and c is mud.

4. The method for dynamically estimating the velocity of the longitudinal wave and the transverse wave in the carbon dioxide flooding process according to claim 1, wherein in the step 3, the bulk modulus Kf of the mixed fluid is calculated by using a Wood-huge-hill formula and a density formula:

$\frac{1}{K_f}=\frac{S_o}{K_o}+\frac{S_g}{K_g}+\frac{S_w}{K_w}$

in the formula: ko, Kg, Kw and Kf are respectively the bulk modulus of oil, gas and water and the bulk modulus of the mixed fluid; so, Sg and Sw are respectively oil-containing, gas-containing and water-containing saturation;

obtaining the density of the mixed fluid and the rock density of the final contained fluid by using a density formula

ρ_f＝S_oρ_o+S_gρ_g+(1-S_o-S_g)ρ_w

In the formula: ρ is the density of the rock containing the fluid, ρ_fFor mixed fluid density, p_oIs the density of the oil, p_gIs the density of gas, p_wIs the density of water, p_dIs the density of the rock skeleton, S_oTo contain saturation, S_gIn order to be at a gas saturation level,is porosity;

obtaining longitudinal wave velocity Vp and longitudinal wave impedance value rho V when different oil, gas and water contents are obtained by utilizing a Gasmann equation and a velocity equation, wherein the formula is as follows:

μ_sat＝μ_d

$\begin{array}{cc}{V}_p=\sqrt{\frac{K_{sat}+\frac{4{\mathrm{\μ}}_{sat}}{3}}{{\mathrm{\ρ}}_{sat}}}& Vs=\sqrt{\frac{{\mathrm{\μ}}_{sat}}{{\mathrm{\ρ}}_{sat}}}\end{array}$

wherein K_satRock bulk modulus, K, for saturated media_dIs the bulk modulus of the rock skeleton, K_fFor mixed fluid bulk modulus, K_mIs the matrix bulk modulus, μ_satShear modulus of saturated medium, mu_dIs the shear modulus of the rock skeleton, ρ_satThe density of the rock is the saturated medium,is porosity;

and (4) putting the calculated wave impedance result into a wave impedance and oil saturation measurement board established by experiments and seismic data to obtain oil saturation, water saturation and gas saturation.

5. The method of claim 1 for dynamically estimating longitudinal and transverse wave velocity in a carbon dioxide flooding process, wherein the method comprisesCharacterized in that in step 6, the results of step 4 and step 5 are combined, and the bulk modulus and the shear modulus K of the rock containing the fluid are calculated by using Gassmann equation again_sat、μ_satThe velocity formula can obtain the longitudinal wave velocity V of the secondary seismic acquisition_pTransverse wave velocity V_s。