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

Abstract

The method for constructing the shear wave transit time curve based on the physical volume model of coal and rock industry components includes the following steps: Step 1, the environmental impact correction of logging data; Step 2, calculating the volume of each component of fixed carbon, moisture, ash and volatile matter; 3. Using the existing rock wave velocity space average model, namely the Voight-Ruess-Hill model, calculate the ash content of the coal-rock skeleton, the equivalent bulk modulus K _ma of fixed carbon, the shear modulus μ _ma , the volatile content of the fluid, the water content, etc. Effective bulk modulus K _f : Step 4, taking the P-wave time difference as the constraint condition, using the bulk modulus and shear modulus of the coal-rock industrial components and the calculated volume fitting of each industrial component to obtain the coal-rock formation Shear wave time difference curve; Step 5, constructing the shear wave time difference curve Δt _sc of coal rock obtained from the above calculation, the present invention provides more accurate and reliable shear wave time difference information for coal rock mechanical parameter calculation and fracturing height logging prediction.

Description

Construction method of shear wave transit time curve based on physical volume model of coal and rock industrial components

technical field

The invention relates to the technical field of coalbed methane exploration and development, in particular to a method for constructing a shear wave time-difference curve based on a physical volume model of coal-rock industrial components.

Background technique

The Hancheng mining area of the Eastern Hubei Gas Field is an important coalbed methane development area in my country, but the shear wave time difference logging curves have not been measured in most of the wells, which has brought great difficulties to the calculation of rock mechanics parameters in drilling engineering design and the prediction of fracturing height in fracturing construction design. A lot of inconvenience.

Shear waves are also called shear waves, and the direction of particle vibration is perpendicular to the direction of propagation. In the past, long source distance acoustic waves were used to obtain acoustic waves in hard formation logging, but dipole (multipole) shear wave logging is required in soft formations such as coal seams, such as the MAC of the 5700 logging series. Dipole shear wave logging is a logging method specially designed for soft formations to obtain shear wave information. It is a new acoustic imaging logging in the 1990s and has been widely used. In my country's coalbed methane wells, most of the wells have not recorded multi-pole array acoustic logging, so the shear wave transit time logging data cannot be obtained, which brings inconvenience to the calculation of rock mechanical parameters and the prediction of fracturing height. Judging from the existing shear wave transit time estimation methods, they mainly focus on conventional sand-shale formations, and there is no shear wave transit time construction method for coal reservoirs. Because the geological conditions and acoustic characteristics of coal reservoirs are completely different from those of conventional sandstone and mudstone formations, the existing shear wave time difference construction methods cannot be transplanted to coalbed methane reservoirs.

At present, the simplified petrophysical volume model is usually used in China to fit the shear wave moveout curve based on methods such as vertical and horizontal moveout and density logging. The simplified petrophysical volume model method only divides the formation into two parts: rock skeleton and pores for shear wave synthesis, and the values of the shear wave logging responses of these two parts have a lot to do with the operator's experience, which is likely to cause errors. Based on the fitting method of vertical and horizontal moveout and density logging, the accuracy of reconstructed shear moveout is relatively poor.

Chinese patent application 201110124614.7 discloses a "synthetic method of shear wave logging curves under formation conditions", which uses conventional logging curves, adopts a fine multi-mineral model, and is based on shear wave logging of different minerals, pores, fluids and other components Response, to fit a shear wave curve reflecting formation characteristics, with high accuracy and precision. This method is the first in China to propose the concept of multi-mineral model fitting shear wave transit time curve, but it is only for conventional formations such as sandy mudstone and carbonate, and does not consider complex lithological formations such as coal rocks.

Contents of the invention

In order to overcome the lack of shear wave transit time logging curves in coal rock formations, the purpose of the present invention is to provide a coal rock shear wave transit time curve construction method, combined with the coal rock industrial component volume physical property model, construct shear wave transit time curves, reduce coal rock While it is difficult to synthesize shear-wave time difference, the accuracy of coal-rock mechanical parameter calculation and fracturing height prediction can be improved. It can not only fully excavate the shear-wave time-difference information contained in the existing conventional logging data, but also organically integrate the coal-rock industrial components and elastic modulus parameters. Combined, log analysts can synthesize shear wave time difference curves more freely, thus providing more accurate and reliable shear wave time difference information for coal rock mechanical parameter calculation and fracturing height logging prediction.

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

The construction method of the shear wave transit time curve based on the physical volume model of coal and rock industry components includes the following steps:

Step 1. Environmental impact correction of logging data: Due to the shallow burial of coalbed methane reservoirs, the development of micropores and fractures, they are easily affected by mud intrusion; the mechanical strength of coal seams is low, and they are easy to collapse during drilling, and the impact of diameter expansion is particularly prominent Therefore, it is necessary to analyze the factors affecting coalbed methane reservoirs affected by the logging environment in detail, and to define the primary and secondary points, and to use the environmental impact correction provided by the logging instrument factory according to the sequence of wellbore→surrounding rock→mud invasion correction The chart is used to correct the environmental impact of the logging data;

Step 2. Calculation of the volume of coal and rock industrial components: input the P-wave time difference, density and neutron logging parameters of fixed carbon, ash, volatile matter and water according to the physical volume model of coal and rock industrial components, and use complex lithology stratum components to calculate method to calculate the volume of each component of fixed carbon, moisture, ash and volatile matter;

Step 3. Calculation of elastic modulus of coal and rock industry components: use the existing rock wave velocity spatially averaged model, namely the Voight-Ruess-Hill model, to calculate the ash content of the coal and rock skeleton, the equivalent bulk modulus K _ma of fixed carbon, and the shear modulus The amount μ _ma , the equivalent bulk modulus K _f of fluid volatile matter and water:

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; )</span>$

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In formula (3), K _Rc , K _Ra , μ _Rc , μ _Ra are bulk modulus and shear modulus of fixed carbon and ash respectively; K _Vc , K _Va , μ _Vc , μ _Va are fixed carbon, ash The bulk modulus and shear modulus; K _v , K _w are the bulk modulus of volatile matter and moisture;

Step 4. Synthesis of the shear wave transit time curve: take the longitudinal wave transit time as the constraint condition, use the bulk modulus and shear modulus of the coal rock industrial components and the calculated volume of each industrial component to obtain the shear wave of the coal rock formation time difference curve,

Using the longitudinal wave time difference Δt _p as a constraint to estimate the β coefficient; according to the Biot-Gassmann theory, it can be deduced that

$\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

β can be calculated by transforming formula (4) into a quadratic equation of one variable or omitting the quadratic term;

For isotropic uniform linear elastic media, according to Hook's law and Newton's law, combined with Biot-Gassmann theory, the relationship between the shear wave time difference of coal rock and the shear modulus of coal rock skeleton, β coefficient and bulk density of coal rock can be obtained. The following relationship exists:

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; sc</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In formula (5), Δt _sc is the shear wave time difference of coal rock, and p _b is the bulk density of coal rock;

Step 5. Using β, μ _ma and ρ _b, the shear wave time difference curve Δt _sc of coal can be constructed according to formula (5).

Based on the physical volume model of coal and rock engineering components, the present invention organically combines the elastic modulus parameters of coal and rock industry components with conventional logging information, and the constructed shear wave time difference curve basically overlaps with the measured shear wave logging curve, and its accuracy is greatly improved .

Description of drawings

Fig. 1 is a flow chart of the construction method of the shear wave time difference curve of the physical volume model of the coal and rock industrial components of the present invention.

Fig. 2 is a schematic diagram of the physical volume model of coal and rock industrial components.

Fig. 3 is a schematic diagram of comparison between the shear wave time difference constructed in the present invention and the measured shear wave time difference.

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings.

A method for constructing a shear wave transit time curve based on a physical volume model of coal and rock industry components, comprising the following steps:

Step 1. Environmental impact correction of logging data: due to the shallow burial of coalbed methane reservoirs, the development of micropores and fractures, they are easily affected by mud intrusion; the mechanical strength of coal seams is low, and they are easy to collapse during drilling, and the impact of diameter expansion is particularly prominent Therefore, it is necessary to analyze the factors affecting coalbed methane reservoirs by the logging environment in detail, and define the primary and secondary points, and use the environmental impact correction provided by the logging instrument factory according to the sequence of wellbore→surrounding rock→mud invasion correction The chart is used to correct the environmental impact of the logging data;

Step 2. Calculation of the volume of coal and rock industrial components: Input the P-wave time difference, density and neutron logging parameters of fixed carbon, ash, volatile matter and water according to the physical volume model of coal and rock industrial components, and use complex lithology stratum components to calculate method to calculate the volume of each component of fixed carbon, moisture, ash and volatile matter;

The actual formation in the physical volume model of coal and rock industry components is a mixture of various minerals and fluids. The coal seam is regarded as a medium model of a saturated fluid (water) composed of fixed carbon (with adsorbed gas), ash, and volatile matter, and the solid skeleton is an elastic solid, and the fluid is compressible and non-viscous. The formation model is shown in Figure 2 shown. Among them, the solid skeleton includes fixed carbon and ash, and the fluid is volatile matter, water in pores and cleats, so the volume model of the coal seam is

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In formula (1), V _c , V _a , V _w , and V _v are volume percentages of carbon, ash, volatile matter, and water, respectively.

According to the basic idea of the logging volume model, the response equations of acoustic transit time, density and compensated neutron logging of the coal seam can be obtained as follows:

Δt=V _a Δt _a +V _c Δt _c +V _w Δt _w +V _v Δt _v

ρ=V _a ρ _a +V _c ρ _c +V _w ρ _w +V _v ρ _v

φ_a、φ_v、φ_w分别是碳分、灰分、挥发份、水分的补偿中子值。In formula (2), V _c , V _a , V _v , and V _w are the volumes of carbon, ash, volatile matter, and water, respectively; ρ _c , ρ _a , ρ _v , and ρ _w are the volumes of carbon, ash, volatile Δt _c , Δt _a , Δt _v , Δt _w are the sonic time differences of carbon, ash, volatile, and moisture, respectively;

φ _a , φ _v , and φ _w are the compensated neutron values of carbon, ash, volatile matter, and moisture, respectively.

According to the physical volume model of coal and rock industry components in Fig. 2, the steps to calculate the component volume of coal and rock by using logging data are as follows:

① Input P-wave time difference, density and neutron logging data. Through crossplot analysis, the fixed carbon and ash parameters of the coal seam and the log curve correction amount for mineral crossover analysis are determined.

② According to Fig. 2, input the P-wave time difference, density and neutron logging parameters of fixed carbon, ash, volatile matter and water.

③ According to formula (2), the volume of fixed carbon, moisture, ash and volatile matter is calculated by using the calculation method of complex lithologic formation components.

Step 3. Calculation of elastic modulus of coal and rock industrial components: use the Voight-Ruess-Hill model to calculate the ash content of coal and rock skeleton, the equivalent bulk modulus K _ma of fixed carbon, the shear modulus μ _ma , fluid volatile matter, moisture The equivalent bulk modulus K _f of:

Based on the spatial average model of rock wave velocity (Voight-Ruess-Hill model), combined with the physical volume model of coal and rock industry components, the equivalent bulk modulus _Kma and equivalent shear modulus _μma of the coal-rock skeleton can be deduced, and the fluid The equivalent bulk modulus K _f is

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; )</span>$

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In formula (3), K _Rc , K _Ra , μ _Rc , μ _Ra are bulk modulus and shear modulus of fixed carbon and ash respectively; K _Vc , K _Va , μ _Vc , μ _Va are fixed carbon, ash The bulk modulus and shear modulus; K _v , K _w are the bulk modulus of volatile matter and moisture.

Step 4. Construction of the shear wave transit time curve: taking the longitudinal wave transit time as the constraint condition, the coal rock formation can be obtained by fitting using the bulk modulus, shear modulus and the calculated volume of each industrial component of the coal rock The shear wave time difference curve of :

The β coefficient is estimated using the P-wave time difference Δt _p as a constraint. According to the Biot-Gassmann theory it can be deduced that

$\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

β can be calculated by transforming formula (4) into a quadratic equation or omitting the quadratic term.

For isotropic uniform linear elastic media, according to Hook's law and Newton's law, combined with Biot-Gassmann theory, the relationship between the shear wave time difference of coal rock and the shear modulus of coal rock skeleton, β coefficient and bulk density of coal rock can be obtained. The following relationship exists:

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; sc</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In formula (5), Δt _sc is the shear wave time difference of coal rock, and ρ _b is the bulk density of coal rock;

Step 5. Using β, μ _ma and ρ _b, the shear wave time difference curve Δt _sc of coal can be constructed according to formula (5).

Referring to the comparison of FIG. 3 , FIG. 3 is a schematic diagram of a comparison between the shear wave time difference constructed in this embodiment and the measured shear wave time difference.

The construction method of shear wave transit time curve based on the industrial components of coal and rock has been tried in the actual evaluation of coalbed methane reservoirs. In the coalbed methane reservoir application of Well X, the shear wave time difference Δt _sc constructed in the 700.1-702.2 and 713.7-717.1 m coal seam sections is basically consistent with the actual measured shear wave time difference Δt _s , and the relative error of the shear wave time difference calculated by this method is between 0.07% to 5.39%, with an average relative error of 1.26%. Therefore, this method not only improves the construction accuracy of coal-rock shear wave time difference, but also reduces the error of coal-rock mechanical parameter calculation and fracturing height logging prediction, which has a certain application value.

Those skilled in the art should understand that, because the diameter expansion of the coal rock section is generally serious, in order to ensure the effectiveness and feasibility of this method, it is necessary to ensure that the density and compressional wave time difference are affected by the diameter expansion correction, and the calculation of the coal rock elastic modulus parameters has Higher precision.

Claims (1)

1. The method for constructing the shear wave transit time curve based on the physical volume model of coal and rock industry components, is characterized in that, comprising the following steps: Step 1. Environmental impact correction of logging data: due to the shallow burial of coalbed methane reservoirs, the development of micropores and fractures, they are easily affected by mud intrusion; the mechanical strength of coal seams is low, and they are easy to collapse during drilling, and the impact of diameter expansion is particularly prominent Therefore, it is necessary to analyze the factors affecting coalbed methane reservoirs by the logging environment in detail, and define the primary and secondary points, and use the environmental impact correction provided by the logging instrument factory according to the sequence of wellbore→surrounding rock→mud invasion correction The chart is used to correct the environmental impact of the logging data; Step 2. Calculation of the volume of coal and rock industrial components: Input the P-wave time difference, density and neutron logging parameters of fixed carbon, ash, volatile matter and water according to the physical volume model of coal and rock industrial components, and use complex lithology stratum components to calculate method to calculate the volume of each component of fixed carbon, moisture, ash and volatile matter; Step 3. Calculation of elastic modulus of coal and rock industry components: use the existing rock wave velocity spatially averaged model, namely the Voight-Ruess-Hill model, to calculate the ash content of the coal and rock skeleton, the equivalent bulk modulus K _ma of fixed carbon, and the shear modulus The amount μ _ma , the equivalent bulk modulus K _f of fluid volatile matter and water: ${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}{<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}{<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; )</span>$ ${\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}{<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Ra</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Rc</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}{<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Vc</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; Va</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$ In formula (3), K _Rc , K _Ra , μ _Rc , μ _Ra are bulk modulus and shear modulus of fixed carbon and ash respectively; K _Vc , K _Va , μ _Vc , μ _Va are fixed carbon, ash The bulk modulus and shear modulus; K _v , K _w are the bulk modulus of volatile matter and moisture; Step 4. Synthesis of the shear wave transit time curve: take the longitudinal wave transit time as the constraint condition, use the bulk modulus and shear modulus of the coal rock industrial components and the calculated volume of each industrial component to obtain the shear wave of the coal rock formation time difference curve, Using the longitudinal wave time difference Δt _p as a constraint to estimate the β coefficient; according to the Biot-Gassmann theory, it can be deduced that $\frac{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$ β can be calculated by transforming formula (4) into a quadratic equation of one variable or omitting the quadratic term; For isotropic uniform linear elastic media, according to Hook's law and Newton's law, combined with Biot-Gassmann theory, the relationship between the shear wave time difference of coal rock and the shear modulus of coal rock skeleton, β coefficient and bulk density of coal rock can be obtained. The following relationship exists: ${\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}_{\mathrm{<span\; class="notranslate">\; sc</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; ma</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$ In formula (5), Δt _sc is the shear wave time difference of coal rock, and ρ _b is the bulk density of coal rock; Step 5: Using β, μ _ma and μ _b according to formula (5), the shear wave time difference curve Δt _sc of coal rock can be constructed.

Images