CN103278850A - Transverse wave time difference curve construction method based on coal rock industrial component physical volume model - Google Patents

Abstract

The invention discloses a transverse wave time difference curve construction method based on a coal rock industrial component physical volume model. The transverse wave time difference curve construction method based on the coal rock industrial component physical volume model comprises the following steps: I, performing logging information environment effect correction; II, calculating volumes of all components including fixed carbon, moisture, ash and volatile matter; III, calculating equivalent volume moduli Kma and shear moduli Muma of the ash and the fixed carbon of a coal rock skeleton and equivalent volume moduli Kf of the volatile matter and the moisture of fluid by utilizing an existing rock wave speed space averaging model, i.e., a Voight-Ruess-Hill model; IV, fitting by utilizing the volume moduli, the shear moduli of the industrial components of coal rock and the worked out volumes of all the industrial components by taking transverse wave time difference as a constraint condition to obtain a transverse wave time difference curve of a coal rock stratum; and V, constructing the transverse wave time difference curve Deltatsc of the coal rock by utilizing the calculated results. According to the transverse wave time difference curve construction method based on the coal rock industrial component physical volume model disclosed by the invention, comparative accurate and reliable transverse wave time difference information is provided for mechanical parameter calculation of the coal rock and fracturing height logging prediction.

Description

Shear wave slowness curve construction method based on coal petrography industry component physical size model

Technical field

The present invention relates to cbm exploration development technique field, particularly based on the shear wave slowness curve construction method of coal petrography industry component physical size model.

Background technology

Mining area, Hancheng, E Dong gas field is China favourable development area of important coal-seam gas, but exhausted big number well is not surveyed the shear wave slowness logging trace, brings inconvenience to pressure break height prediction in rock mechanics calculation of parameter, the pressing crack construction design in the drilling engineering design.

Shear wave also claims shearing wave, and the direction of its particle vibration is vertical with the direction of propagation.In the hard formation well logging, obtained sound wave with the long space sound wave in the past, but need carry out dipole (multipole) SWAL at the soft formation as the coal seam, as the MAC of 5700 logging suites.The dipole SWAL is a kind of logging method that obtains shear wave information that designs at soft formation specially, is a kind of new acoustic imaging well logging nineties in 20th century, and has obtained using widely.In China's coal bed gas well, even most of well is not enrolled MAC, thereby can't obtain the shear wave slowness well-log information, this makes troubles for rock mechanics calculation of parameter and the prediction of pressure break height.From existing shear wave slowness evaluation method, mainly concentrate on the conventional sand shale stratum, even less than the shear wave slowness construction method at coal seam reservoirs.Because coal seam reservoirs geologic condition, acoustic characteristic and conventional sand shale stratum are completely different, existing shear wave slowness construction method can not be transplanted on the coalbed methane reservoir.

At present, the rock physics volume-based model simplified of domestic common employing, come match shear wave slowness curve based on method such as the time difference and density logging in length and breadth.The rock physics volume-based model method of simplifying just is divided into the stratum rock skeleton and hole two parts, and to carry out shear wave synthetic, and the value of the SWAL of these two parts response and operating personnel's experience have much relations, cause error easily.Based on the approximating method of the time difference and density logging in length and breadth, the shear wave slowness ratio of precision of its reconstruct is relatively poor.

Chinese patent application 201110124614.7 discloses a kind of " synthetic method of SWAL curve under the formation condition ", this method is utilized the conventional logging curve, adopt meticulous multimineral model, SWAL response according to components such as different minerals, hole, fluids, simulate the shear wave curve of a reflection stratum characteristic, accuracy and precision are all very high.This method has proposed for the first time the concept of multimineral model match shear wave slowness curve at home, but just at conventional stratum such as sand shale, carbonate, and does not consider complex lithology formation such as coal petrography.

Summary of the invention

In order to overcome the deficiency that the coal petrography stratum lacks the shear wave slowness logging trace, the object of the present invention is to provide a kind of coal petrography shear wave slowness curve construction method, in conjunction with coal petrography industry group partial volume rerum natura model, the shear wave slowness curve is made up, reduce and improve the calculating of coal petrography mechanics parameter when the coal petrography shear wave slowness synthesizes difficulty, pressure break height accuracy of predicting, can not only fully excavate the shear wave slowness information that existing conventional logging data is contained, and with coal petrography industry component and the combination of elastic modulus parameter, make the log analyst can synthesize the shear wave slowness curve more freely, thereby calculate and the well logging of pressure break height is provided by the shear wave slowness information comparatively accurately and reliably that provides for the coal petrography mechanics parameter.

In order to achieve the above object, technical scheme of the present invention is:

Shear wave slowness curve construction method based on coal petrography industry component physical size model may further comprise the steps:

Step 1, well-log information environmental impact are proofreaied and correct: because that coalbed methane reservoir buries is shallow, and microporosity and fracture development, the influence that invaded by mud; The physical strength in coal seam is low, cave in easily in the drilling process, the hole enlargement influence is particularly outstanding, therefore the factor that needs the tested well environment influence of full and accurate analysis coalbed methane reservoir, and define the branch of primary and secondary, and the sequencing of proofreading and correct according to well → country rock → mud intrusion effect, the environmental impact correcting plate that adopts logging instrumentation factory to provide carries out the well-log information environmental impact and proofreaies and correct;

Step 2, coal petrography industry group partial volume calculate: according to compressional wave time difference, density and the neutron well logging parameter of coal petrography industry component physical size model input fixed carbon, ash content, fugitive constituent and moisture, adopt complex lithology formation component computing method, calculate the volume of fixed carbon, moisture, ash content and each component of fugitive constituent;

Step 3, coal petrography industry component elastic modulus calculate: utilizing existing rock velocity of wave space average model is the Voight-Ruess-Hill model, calculates the equivalent volume modulus K of coal petrography skeleton ash content, fixed carbon _Ma, modulus of shearing μ _Ma, the equivalent volume modulus K of volatilize fluid part, moisture _f:

$K_{\mathrm{ma}}=\frac{1}{2}(\frac{K_{\mathrm{Rc}}\·K_{\mathrm{Ra}}}{K_{\mathrm{Rc}}\·V_{\mathrm{Ra}}+K_{\mathrm{Ra}}\·V_{\mathrm{Rc}}}+K_{\mathrm{Vc}}\·V_{\mathrm{Vc}}+K_{\mathrm{Va}}\·V_{\mathrm{Va}})$

${\mathrm{\μ}}_{\mathrm{ma}}=\frac{1}{2}(\frac{{\mathrm{\μ}}_{\mathrm{Rc}}\·{\mathrm{\μ}}_{\mathrm{Ra}}}{{\mathrm{\μ}}_{\mathrm{Rc}}\·V_{\mathrm{Ra}}+{\mathrm{\μ}}_{\mathrm{Ra}}\·V_{\mathrm{Rc}}}+{\mathrm{\μ}}_{\mathrm{Vc}}\·V_{\mathrm{Vc}}+{\mathrm{\μ}}_{\mathrm{Va}}\·V_{\mathrm{Va}})$

$\frac{1}{K_f}=\frac{V_v}{K_v}+\frac{V_w}{K_w}---\left(3\right)$

In the formula (3), K _Rc, K _Ra, μ _Rc, μ _RaBe respectively bulk modulus and the modulus of shearing of fixed carbon, ash content; K _Vc, K _Va, μ _Vc, μ _VaBe respectively bulk modulus and the modulus of shearing of fixed carbon, ash content; K _v, K _wBulk modulus for fugitive constituent and moisture;

Step 4, shear wave slowness curve synthetic: be constraint condition with the compressional wave time difference, utilize bulk modulus, the modulus of shearing of coal petrography industry component and the volume match of each industrial component of having calculated obtains the shear wave slowness curve on coal petrography stratum,

Utilize compressional wave time difference Δ t _pAs constraint estimation beta coefficient; Can derive according to the Biot-Gassmann theory

$\frac{{\mathrm{\ρ}}_b}{\mathrm{\Δ}{t}_p^2}=(K_{\mathrm{ma}}+\frac{4}{3}{\mathrm{\μ}}_{\mathrm{ma}})(1-\mathrm{\β})+{\mathrm{\β}}^2\frac{K_{\mathrm{ma}}{K}_w}{K_{\mathrm{ma}}\mathrm{\β}+(K_{\mathrm{ma}}-K_w)V_w}---\left(4\right)$

Formula (4) changed into quadratic equation with one unknown or omit quadratic term can calculate β;

For isotropy uniform line elastic medium, by Hook law and Newton's law, and in conjunction with the Biot-Gassmann theory, just can draw and have following relation between the volume density of the shear wave slowness of coal petrography and coal petrography skeleton modulus of shearing, beta coefficient and coal petrography:

$\mathrm{\Δ}{t}_{\mathrm{sc}}=\frac{1}{\sqrt{\frac{{\mathrm{\μ}}_{\mathrm{ma}(1-\mathrm{\β})}}{{\mathrm{\ρ}}_b}}}---\left(5\right)$

In the formula (5), Δ t _ScBe the shear wave slowness of coal petrography, p _bVolume density for coal petrography;

Step 5, utilize β, μ _Ma, ρ _bJust can make up the shear wave slowness curve Δ t of coal petrography according to formula (5) _Sc

The present invention is based on coal petrography worker component physical size model, with elastic modulus parameter and the combination of conventional logging information of coal petrography industry component, constructed shear wave slowness curve is overlapping substantially with actual measurement SWAL curve, and its precision improves greatly.

Description of drawings

Fig. 1 is the construction method process flow diagram of the shear wave slowness curve of coal petrography industry component physical size model of the present invention.

Fig. 2 is the physical size model synoptic diagram of coal petrography industry component.

The shear wave slowness and actual measurement shear wave slowness contrast synoptic diagram of Fig. 3 for making up among the present invention.

Embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is done and to be described in detail.

A kind of shear wave slowness curve construction method based on coal petrography industry component physical size model may further comprise the steps:

Step 1, well-log information environmental impact are proofreaied and correct: because that coalbed methane reservoir buries is shallow, and microporosity and fracture development, the influence that invaded by mud; The physical strength in coal seam is low, cave in easily in the drilling process, the hole enlargement influence is particularly outstanding, therefore the factor that needs the tested well environment influence of full and accurate analysis coalbed methane reservoir, and define the branch of primary and secondary, and the sequencing of proofreading and correct according to well → country rock → mud intrusion effect, the environmental impact correcting plate that adopts logging instrumentation factory to provide carries out the well-log information environmental impact and proofreaies and correct;

Step 2, coal petrography industry group partial volume calculate: according to compressional wave time difference, density and the neutron well logging parameter of coal petrography industry component physical size model input fixed carbon, ash content, fugitive constituent and moisture, adopt complex lithology formation component computing method, calculate the volume of fixed carbon, moisture, ash content and each component of fugitive constituent;

The potpourri that the actual formation of coal petrography industry component physical size model is made up of multi mineral and fluid.The coal seam is considered as the dielectric model that is full of fluid (water) be made up of fixed carbon (gas that has absorption), ash content, fugitive constituent, and solid skeletal be elastic solid (Hookean body), fluid is compressible and do not have viscosity, then stratigraphic model is as shown in Figure 2.Wherein solid skeletal comprises fixed carbon, ash content, and fluid is the moisture in fugitive constituent, hole and the hugger, so the volume-based model in coal seam is

$V_c+V_a+V_v+V_w=1---\left(1\right)$

In the formula (1), V _c, V _a, V _w, V _vIt is respectively the percent by volume of carbon branch, ash content, fugitive constituent, moisture.

According to the basic thought of well logging volume-based model, the response equation that can obtain interval transit time, density and the compensated neutron log in coal seam is:

Δt=V _aΔt _a+V _cΔt _c+V _wΔt _w+V _vΔt _v

ρ=V _aρ _a+V _cρ _c+V _wρ _w+V _vρ _v

In the formula (2), V _c, V _a, V _v, V _wIt is respectively the volume of carbon branch, ash content, fugitive constituent, moisture; ρ _c, ρ _a, ρ _v, ρ _wIt is respectively the density value of carbon branch, ash content, fugitive constituent, moisture; Δ t _c, Δ t _a, Δ t _v, Δ t _wIt is respectively the interval transit time value of carbon branch, ash content, fugitive constituent, moisture;

φ _a, φ _v, φ _wIt is respectively the compensated neutron value of carbon branch, ash content, fugitive constituent, moisture.

According to coal petrography industry component physical size model among Fig. 2, the step of utilizing well-log information to calculate the component volume of coal petrography is:

1. import compressional wave time difference, density and neutron well logging data.By crossplot analysis and its, determine fixed carbon, the ash content parameter in coal seam and be used for the logging trace correcting value that the mineral intersection is analyzed.

2. import compressional wave time difference, density and the neutron well logging parameter of fixed carbon, ash content, fugitive constituent and moisture according to Fig. 2.

3. according to formula (2), adopt complex lithology formation component computing method, calculate the volume of fixed carbon, moisture, ash content and fugitive constituent.

Step 3, coal petrography industry component elastic modulus calculate: utilize the Voight-Ruess-Hill model to calculate the equivalent volume modulus K of coal petrography skeleton ash content, fixed carbon _Ma, modulus of shearing μ _Ma, the equivalent volume modulus K of volatilize fluid part, moisture _f:

Based on rock velocity of wave space average model (Voight-Ruess-Hill model), in conjunction with coal petrography industry component physical size model, can derive coal petrography skeleton equivalent volume modulus K _Ma, equivalent shear modulus μ _Ma, the equivalent volume modulus K of fluid _fFor

$K_{\mathrm{ma}}=\frac{1}{2}(\frac{K_{\mathrm{Rc}}\·K_{\mathrm{Ra}}}{K_{\mathrm{Rc}}\·V_{\mathrm{Ra}}+K_{\mathrm{Ra}}\·V_{\mathrm{Rc}}}+K_{\mathrm{Vc}}\·V_{\mathrm{Vc}}+K_{\mathrm{Va}}\·V_{\mathrm{Va}})$

${\mathrm{\μ}}_{\mathrm{ma}}=\frac{1}{2}(\frac{{\mathrm{\μ}}_{\mathrm{Rc}}\·{\mathrm{\μ}}_{\mathrm{Ra}}}{{\mathrm{\μ}}_{\mathrm{Rc}}\·V_{\mathrm{Ra}}+{\mathrm{\μ}}_{\mathrm{Ra}}\·V_{\mathrm{Rc}}}+{\mathrm{\μ}}_{\mathrm{Vc}}\·V_{\mathrm{Vc}}+{\mathrm{\μ}}_{\mathrm{Va}}\·V_{\mathrm{Va}})$

$\frac{1}{K_f}=\frac{V_v}{K_v}+\frac{V_w}{K_w}---\left(3\right)$

In the formula (3), K _Rc, K _Ra, μ _Rc, μ _RaBe respectively bulk modulus and the modulus of shearing of fixed carbon, ash content; K _Vc, K _Va, μ _Vc, μ _VaBe respectively bulk modulus and the modulus of shearing of fixed carbon, ash content; K _v, K _wBulk modulus for fugitive constituent and moisture.

The structure of step 4, shear wave slowness curve: be constraint condition with the compressional wave time difference, utilize bulk modulus, the modulus of shearing of coal petrography industry component and the volume of each industrial component of having calculated just can match obtains the shear wave slowness curve on coal petrography stratum:

Utilize compressional wave time difference Δ t _pAs constraint estimation beta coefficient.Can derive according to the Biot-Gassmann theory

$\frac{{\mathrm{\ρ}}_b}{\mathrm{\Δ}{t}_p^2}=(K_{\mathrm{ma}}+\frac{4}{3}{\mathrm{\μ}}_{\mathrm{ma}})(1-\mathrm{\β})+{\mathrm{\β}}^2\frac{K_{\mathrm{ma}}{K}_w}{K_{\mathrm{ma}}\mathrm{\β}+(K_{\mathrm{ma}}-K_w)V_w}---\left(4\right)$

Formula (4) changed into quadratic equation with one unknown or omit quadratic term can calculate β.

For isotropy uniform line elastic medium, by Hook law and Newton's law, and in conjunction with the Biot-Gassmann theory, just can draw and have following relation between the volume density of the shear wave slowness of coal petrography and coal petrography skeleton modulus of shearing, beta coefficient and coal petrography:

$\mathrm{\Δ}{t}_{\mathrm{sc}}=\frac{1}{\sqrt{\frac{{\mathrm{\μ}}_{\mathrm{ma}(1-\mathrm{\β})}}{{\mathrm{\ρ}}_b}}}---\left(5\right)$

In the formula (5), Δ t _ScBe the shear wave slowness of coal petrography, ρ _bVolume density for coal petrography;

Step 5, utilize β, μ _Ma, ρ _bJust can make up the shear wave slowness curve Δ t of coal petrography according to formula (5) _Sc

With reference to the contrast of Fig. 3, the shear wave slowness and actual measurement shear wave slowness contrast synoptic diagram of Fig. 3 for making up in the present embodiment.

Shear wave slowness curve construction method based on coal petrography industry component is tried out in actual coalbed methane reservoir evaluation.In the coalbed methane reservoir of X well is used, 700.1～702.2,713.7～717.1 meters basic Δ t of shear wave slowness that the coal seam section makes up _ScShear wave slowness Δ t with actual measurement _sUnanimity, the shear wave slowness relative error of this method The Fitting Calculation be between 0.07%～5.39%, average relative error 1.26%.When therefore this method improves coal petrography shear wave slowness structure precision, reduce the error of the calculating of coal petrography mechanics parameter and pressure break height well logging prediction, had certain application value.

Those skilled in the art is to be understood that, hole enlargement is comparatively serious generally speaking owing to the coal petrography section, in order to guarantee the effective and feasible property of this method, must ensure that density and compressional wave time difference are subjected to effect correction, coal petrography elastic modulus calculation of parameter such as hole enlargement to have higher precision.

Claims (1)

1. based on the shear wave slowness curve construction method of coal petrography industry component physical size model, it is characterized in that, may further comprise the steps:

Step 1, well-log information environmental impact are proofreaied and correct: because that coalbed methane reservoir buries is shallow, and microporosity and fracture development, the influence that invaded by mud; The physical strength in coal seam is low, cave in easily in the drilling process, the hole enlargement influence is particularly outstanding, therefore the factor that needs the tested well environment influence of full and accurate analysis coalbed methane reservoir, and define the branch of primary and secondary, and the sequencing of proofreading and correct according to well → country rock → mud intrusion effect, the environmental impact correcting plate that adopts logging instrumentation factory to provide carries out the well-log information environmental impact and proofreaies and correct;

Step 2, coal petrography industry group partial volume calculate: according to compressional wave time difference, density and the neutron well logging parameter of coal petrography industry component physical size model input fixed carbon, ash content, fugitive constituent and moisture, adopt complex lithology formation component computing method, calculate the volume of fixed carbon, moisture, ash content and each component of fugitive constituent;

Step 3, coal petrography industry component elastic modulus calculate: utilizing existing rock velocity of wave space average model is the Voight-Ruess-Hill model, calculates the equivalent volume modulus K of coal petrography skeleton ash content, fixed carbon _Ma, modulus of shearing μ _Ma, the equivalent volume modulus K of volatilize fluid part, moisture _f:

$K_{\mathrm{ma}}=\frac{1}{2}(\frac{K_{\mathrm{Rc}}\·K_{\mathrm{Ra}}}{K_{\mathrm{Rc}}{\·V}_{\mathrm{Ra}}+K_{\mathrm{Ra}}\·V_{\mathrm{Rc}}}+K_{\mathrm{Vc}}{\·V}_{\mathrm{Vc}}+K_{\mathrm{Va}}\·V_{\mathrm{Va}})$

${\mathrm{\μ}}_{\mathrm{ma}}=\frac{1}{2}(\frac{{\mathrm{\μ}}_{\mathrm{Rc}}\·{\mathrm{\μ}}_{\mathrm{Ra}}}{{\mathrm{\μ}}_{\mathrm{Rc}}{\·V}_{\mathrm{Ra}}+{\mathrm{\μ}}_{\mathrm{Ra}}\·V_{\mathrm{Rc}}}+{\mathrm{\μ}}_{\mathrm{Vc}}{\·V}_{\mathrm{Vc}}+{\mathrm{\μ}}_{\mathrm{Va}}\·V_{\mathrm{Va}})---\left(3\right)$

In the formula (3), K _Rc, K _Ra, μ _Rc, μ _RaBe respectively bulk modulus and the modulus of shearing of fixed carbon, ash content; K _Vc, K _Va, μ _Vc, μ _VaBe respectively bulk modulus and the modulus of shearing of fixed carbon, ash content; K _v, K _wBulk modulus for fugitive constituent and moisture;

Step 4, shear wave slowness curve synthetic: be constraint condition with the compressional wave time difference, utilize bulk modulus, the modulus of shearing of coal petrography industry component and the volume match of each industrial component of having calculated obtains the shear wave slowness curve on coal petrography stratum,

Utilize compressional wave time difference Δ t _pAs constraint estimation beta coefficient; Can derive according to the Biot-Gassmann theory

$\frac{{\mathrm{\ρ}}_b}{\mathrm{\Δ}{t}_p^2}=(K_{\mathrm{ma}}+\frac{4}{3}{\mathrm{\μ}}_{\mathrm{ma}})(1-\mathrm{\β})+{\mathrm{\β}}^2\frac{K_{\mathrm{ma}}{K}_w}{K_{\mathrm{ma}}\mathrm{\β}+(K_{\mathrm{ma}}-K_w)V_w}---\left(4\right)$

Formula (4) changed into quadratic equation with one unknown or omit quadratic term can calculate β;

For isotropy uniform line elastic medium, by Hook law and Newton's law, and in conjunction with the Biot-Gassmann theory, just can draw and have following relation between the volume density of the shear wave slowness of coal petrography and coal petrography skeleton modulus of shearing, beta coefficient and coal petrography:

${\mathrm{\Δt}}_{\mathrm{sc}}=\frac{1}{\sqrt{\frac{{\mathrm{\μ}}_{\mathrm{ma}}(1-\mathrm{\β})}{{\mathrm{\ρ}}_b}}}---\left(5\right)$

In the formula (5), Δ t _ScBe the shear wave slowness of coal petrography, ρ _bVolume density for coal petrography;

Step 5, utilize β, μ _Ma, μ _bJust can make up the shear wave slowness curve Δ t of coal petrography according to formula (5) _Sc

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