CN105549088A - Method and device for identifying gas layer in fractured compact sandstone - Google Patents
Method and device for identifying gas layer in fractured compact sandstone Download PDFInfo
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Abstract
The invention provides a method and a device for identifying a gas layer in fractured tight sandstone, wherein the method comprises the following steps: according to the conventional and full-waverow acoustic logging processing of the fractured compact sandstone in the area to be evaluated, obtaining a longitudinal and transverse wave time difference curve, calculating and obtaining the porosity and the argillaceous content of the fractured compact sandstone by adopting a porosity model and a argillaceous model, and obtaining the elastic modulus of the fractured compact sandstone by combining the pre-obtained density data; calculating and obtaining a fluid compression coefficient according to the porosity, the shale content, the elastic modulus and the component content of the fractured compact sandstone obtained in advance; the fluid properties of the fractured tight sandstone are judged according to the fluid compression coefficient of the fractured tight sandstone and the pre-acquired water compression coefficient, and the precision of evaluating the gas layer in the fractured tight sandstone is effectively improved by adopting a new method for correcting the fluid compression coefficient and identifying the gas layer by adopting acoustic full-wavetrain logging information.
Description
Technical Field
The invention relates to the petroleum exploration technology, in particular to a method and a device for identifying a gas layer in fractured compact sandstone.
Background
In the field of oil exploration, accurate evaluation of rock strata is particularly important, and the low porosity and low permeability of the rock strata distort the reflection of part of logging information on the rock strata, so that the difficulty of logging evaluation is increased, and therefore, the rock strata need to be accurately evaluated at the initial stage of oil field exploration and development.
At present, a response characteristic method, a three-porosity overlap/difference/ratio method, a porosity and resistivity intersection method, a irreducible water saturation method, a visual formation water resistivity method and the like are mostly adopted for identifying and evaluating a gas formation by applying conventional logging data. The lithology and granularity of the tight fractured sandstone are changed greatly, and are influenced by the dip angle of the stratum structure, the reservoir fluid property is difficult to be accurately identified by using the electrical logging and porosity logging information, the gas reservoir is judged by using the acoustic full wave train logging information in the conventional common mode, and the fluid property of the reservoir is evaluated by using the drop of the longitudinal-transverse wave velocity ratio in oil field application.
However, the acoustic properties of oil, gas and water in the formation pores are different, the densities are different, and the compression coefficients of the oil, the gas and the water are also different, so that the method has a good application effect in the formation with good reservoir characteristics, but in the compact fractured sandstone formation, due to the existence of fractures in the sandstone formation, the storage space of the reservoir is increased, the pore structure characteristics are changed, the sensitivity of the sound wave propagation speed to the gas layer is reduced, and the precision of evaluating the gas layer in the compact fractured sandstone is low.
Disclosure of Invention
The invention provides a method and a device for identifying a gas layer in fractured tight sandstone, which are used for solving the problems that in the prior art, due to the existence of fractures in a sandstone stratum, the storage space of a reservoir is increased, the pore structure characteristics are changed, the sensitivity of the sound wave propagation speed to the gas layer is reduced, and the evaluation precision of the gas layer in the fractured tight sandstone is low.
The invention provides a method for identifying a gas layer in fractured tight sandstone, which comprises the following steps:
according to the conventional and full-waverow acoustic logging processing of the fractured compact sandstone in the area to be evaluated, obtaining a longitudinal and transverse wave time difference curve, calculating and obtaining the porosity and the argillaceous content of the fractured compact sandstone by adopting a porosity model and a argillaceous model, and obtaining the elastic modulus of the fractured compact sandstone by combining the pre-obtained density data;
calculating and obtaining a fluid compression coefficient according to the porosity, the shale content, the elastic modulus and the component content of the fractured compact sandstone obtained in advance;
and judging the fluid property of the fractured tight sandstone according to the fluid compression coefficient of the fractured tight sandstone and the pre-acquired compression coefficient of water.
Optionally, the determining the fluid property of the fractured tight sandstone according to the fluid compressibility of the fractured tight sandstone and the compressibility of water obtained in advance includes:
if the difference value between the fluid compression coefficient and the compression coefficient of the water is greater than 0, the fractured compact sandstone is a gas layer;
and if the difference value between the fluid compressibility and the compressibility of the water is less than or equal to 0, the fractured compact sandstone is a water layer.
Optionally, the obtaining a fluid compressibility according to the porosity, the shale content, the elastic modulus and the pre-obtained fracture tight sandstone component content includes:
determining the elastic modulus of rock particles of the fractured tight sandstone according to the component content of the fractured tight sandstone obtained in advance;
calculating and obtaining the elastic modulus of the dry rock of the fractured compact sandstone according to the porosity, the shale content and the elastic modulus of the rock particles;
according to the void fraction, the rockThe modulus of elasticity of the particles and the modulus of elasticity of the dry rock, usingCalculating and acquiring the fluid compression coefficient;
wherein, CfRepresenting the coefficient of compression, K, of the fluidfThe bulk modulus of elasticity of a fluid is expressed,denotes the porosity, c denotes a fracture shape coefficient, a denotes a fracture aspect ratio, and a is less than or equal to 1, GmaExpressing rock particle shear modulus of elasticity, KmaExpressing the elastic modulus of the rock particles, A expressing the unit transformation coefficient, usingIs obtained by calculation, KdDenotes the dry rock modulus of elasticity and K denotes the saturated rock modulus of elasticity.
Optionally, the obtaining of the dry rock elastic modulus of the fractured tight sandstone according to the porosity, the shale content and the rock particle elastic modulus by calculation includes:
calculating according to the longitudinal wave velocity, the transverse wave velocity and the density skeleton of the fractured compact sandstone to obtain the elastic modulus of the dry rock skeleton and the bulk elastic modulus of the argillaceous mass;
calculating according to the elastic modulus of the dry rock framework and the bulk elastic modulus of the argillaceous mass to obtain the elastic modulus of the dry rock; or,
and calculating to obtain the elastic modulus of the dry rock by adopting a calculation model obtained by experiments according to the porosity or the elastic modulus of the dry rock framework.
Optionally, the compressibility of water is 444 MPa; the elastic modulus of the fractured tight sandstone comprises rock compressibility, shear modulus and Poisson ratio.
Another aspect of the present invention provides an apparatus for identifying a gas layer in fractured tight sandstone, comprising:
the first processing module is used for calculating and acquiring the porosity and the shale content of the fractured compact sandstone by adopting a porosity model and a shale model according to a longitudinal and transverse wave time difference curve obtained by conventional and full-waverow acoustic logging processing of the fractured compact sandstone in the area to be evaluated, and acquiring the elastic modulus of the fractured compact sandstone by combining the pre-acquired density data;
the second processing module is used for calculating and obtaining a fluid compression coefficient according to the porosity, the argillaceous content, the elastic modulus and the component content of the fractured compact sandstone obtained in advance;
and the third processing module is used for judging the fluid property of the fractured tight sandstone according to the fluid compression coefficient of the fractured tight sandstone and the pre-acquired compression coefficient of the water.
Optionally, the third processing module is specifically configured to:
if the difference value between the fluid compression coefficient and the compression coefficient of the water is greater than 0, the fractured compact sandstone is a gas layer;
and if the difference value between the fluid compressibility and the compressibility of the water is less than or equal to 0, the fractured compact sandstone is a water layer.
Optionally, the second processing module is specifically configured to:
determining the elastic modulus of rock particles of the fractured tight sandstone according to the component content of the fractured tight sandstone obtained in advance;
calculating and obtaining the elastic modulus of the dry rock of the fractured compact sandstone according to the porosity, the shale content and the elastic modulus of the rock particles;
according to the porosity, the elastic modulus of the rock particles and the dry rockModulus of elasticity of stone, usingCalculating and acquiring the fluid compression coefficient;
wherein, CfRepresenting the coefficient of compression, K, of the fluidfThe bulk modulus of elasticity of a fluid is expressed,denotes the porosity, c denotes a fracture shape coefficient, a denotes a fracture aspect ratio, and a is less than or equal to 1, GmaExpressing rock particle shear modulus of elasticity, KmaExpressing the elastic modulus of the rock particles, A expressing the unit transformation coefficient, usingIs obtained by calculation, KdDenotes the dry rock modulus of elasticity and K denotes the saturated rock modulus of elasticity.
Optionally, the second processing module is further configured to:
calculating according to the longitudinal wave velocity, the transverse wave velocity and the density skeleton of the fractured compact sandstone to obtain the elastic modulus of the dry rock skeleton and the bulk elastic modulus of the argillaceous mass;
calculating according to the elastic modulus of the dry rock framework and the bulk elastic modulus of the argillaceous mass to obtain the elastic modulus of the dry rock; or,
and calculating to obtain the elastic modulus of the dry rock by adopting a calculation model obtained by experiments according to the porosity or the elastic modulus of the dry rock framework.
The invention provides a method and a device for identifying a gas layer in fractured tight sandstone, which are a novel method for identifying the gas layer by adopting a fluid compression coefficient to compare the fluid compression coefficient of the fractured tight sandstone with the fluid compression coefficient of water to judge the fluid property of the fractured tight sandstone by adopting acoustic wave array logging information and correcting the fluid compression coefficient according to a longitudinal wave time difference curve obtained by conventional and full wave array acoustic logging processing of the fractured tight sandstone in an area to be evaluated, calculating and obtaining the porosity and the shale content of the fractured tight sandstone by adopting a porosity model and a shale model, obtaining the elastic modulus of the fractured tight sandstone by combining pre-obtained density information, calculating and obtaining the fluid compression coefficient by combining the porosity, the shale content, the elastic modulus and the pre-obtained component content of the fractured tight sandstone, the precision of evaluating the gas layer in the tight fractured sandstone is effectively improved.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a flow chart of a first embodiment of the method for identifying a gas layer in fractured tight sandstone according to the invention;
FIG. 2 is a flow chart of a second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the invention;
fig. 3a is a schematic diagram showing a relationship between bulk modulus and porosity when air is saturated in a coin-like fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention;
fig. 3b is a schematic diagram showing a relationship between a bulk modulus of elasticity and a fracture minor-major axis when air is saturated in a coin-shaped fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention;
fig. 4a is a schematic diagram showing a relationship between bulk modulus and porosity when water is saturated in a coin-shaped fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention;
fig. 4b is a schematic diagram showing a relationship between bulk modulus of elasticity and fracture minor and major axes when water is saturated in a coin-shaped fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention;
fig. 5 is a schematic structural diagram of a first embodiment of the identification device for gas layers in fractured tight sandstone.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to effectively identify the fluid characteristics of the tight fractured sandstone reservoir, a modified saturated fractured rock compression coefficient formula is provided by combining a Walsh (1965) formula that the dry rock compression coefficient is influenced by fractures, and the fluid compression coefficient is calculated by using the formula for identifying the fluid properties.
Fig. 1 is a flowchart of a first embodiment of the identification method for a gas layer in fractured tight sandstone, as shown in fig. 1, the identification method for a gas layer in fractured tight sandstone provided by the invention has the following specific implementation steps:
s101: according to the conventional and full-wave-train acoustic logging treatment of the fractured compact sandstone in the area to be evaluated, the obtained longitudinal and transverse wave time difference curves are calculated by adopting a porosity model and a argillaceous model, so that the porosity and the argillaceous content of the fractured compact sandstone are obtained, and the elastic modulus of the fractured compact sandstone is obtained by combining the pre-obtained density data.
In this embodiment, the acoustic full-wave logging can utilize not only the velocity and amplitude information of the longitudinal wave and the transverse wave, but also other subsequent wave components, such as pseudo-rayleigh wave and stoneley wave, that is, the acoustic full-wave-train logging can provide more information for oil exploration and development. By utilizing the information, the lithology, the porosity, the permeability, the fluid saturation and other information of the stratum can be directly or indirectly obtained. Stratum shear waves carry more stratum information, and the method has important significance in determining parameters such as stratum porosity, fluid saturation, cracks and the like.
The porosity and the shale content can be respectively obtained by loading the longitudinal and transverse wave time difference curves of conventional and full-wave-train acoustic logging processing in FORWARD software and adopting a porosity model and a shale model in the prior art.
S102: and calculating and obtaining the fluid compression coefficient according to the porosity, the shale content, the elastic modulus and the component content of the fractured compact sandstone obtained in advance.
In this embodiment, the fluid (including liquid and gas) generally has a compressibility that is expressed by a fluid compressibility, because the fluid density and specific volume change due to a change in pressure.
That is, as long as the porosity, the saturated rock elastic modulus and the rock particle elastic modulus are known through the rock reservoir to be evaluated, the compressibility of the fluid in the fracture in the rock reservoir can be obtained for evaluating the characteristics of the fluid.
S103: and judging the fluid property of the fractured tight sandstone according to the fluid compression coefficient of the fractured tight sandstone and the pre-acquired compression coefficient of water.
In the present embodiment, the obtained compression factor of the fluid is compared with the compression factor of water having stable properties to confirm the properties of the fluid to be evaluated.
Specifically, in S103, the fluid property of the fractured tight sandstone is determined according to the fluid compression coefficient of the fractured tight sandstone and the pre-obtained compression coefficient of water, and the specific implementation manner is as follows:
and if the difference value between the fluid compressibility and the compressibility of the water is greater than 0, the fractured compact sandstone is a gas layer.
And if the difference value between the fluid compressibility and the compressibility of the water is less than or equal to 0, the fractured compact sandstone is a water layer.
In this example, theoretically, the fluid compressibility of the pure water layer is 4.44(1/10GPa), the pure oil layer is 8.37(1/10GPa), and the pure gas layer is 180.51(1/10GPa), and the water layer and the oil layer are close to each other in terms of compressibility, and therefore, the fluid compressibility of the gas layer is much larger than that of the pure gas layer, and therefore, the gas layer is considered to be a gas layer because the gas layer is easily identified by the compressibility of the water layer, that is, the fluid compressibility, and is generally larger than the fluid compressibility 4(1/10GPa) or more.
In the method for identifying a gas layer in fractured tight sandstone provided by this embodiment, according to a longitudinal and transverse wave time difference curve obtained by conventional and full wavetrain acoustic logging processing of fractured tight sandstone in an area to be evaluated, a porosity model and a shale model are used to calculate and obtain porosity and shale content of the fractured tight sandstone, an elastic modulus of the fractured tight sandstone is obtained by combining with a pre-obtained density data, a fluid compression coefficient is obtained by combining the porosity, the shale content, the elastic modulus and a pre-obtained component content of the fractured tight sandstone, the fluid compression coefficient of the fractured tight sandstone and a fluid compression coefficient of water are compared to judge a fluid property of the fractured tight sandstone, and the gas layer is identified by correcting the fluid compression coefficient by using acoustic full wavetrain logging data, the precision of evaluating the gas layer in the tight fractured sandstone is effectively improved.
Fig. 2 is a flowchart of an embodiment two of the method for identifying a gas layer in fractured tight sandstone according to the present invention, and as shown in fig. 2, based on the above embodiment, the specific implementation steps in S102 for calculating and obtaining the fluid compressibility according to the porosity, the shale content, the elastic modulus, and the pre-obtained component content of the fractured tight sandstone are as follows:
s201: and determining the elastic modulus of the rock particles of the fractured tight sandstone according to the component content of the fractured tight sandstone obtained in advance.
S202: and calculating and obtaining the elastic modulus of the dry rock of the fractured compact sandstone according to the porosity, the argillaceous content and the elastic modulus of the rock particles.
In the present embodiment, specific implementations at least include the following two,
in a first implementation mode, the elastic modulus of a dry rock framework and the bulk elastic modulus of argillaceous materials are calculated according to the longitudinal wave velocity, the transverse wave velocity and the density framework of the fractured compact sandstone;
and calculating according to the elastic modulus of the dry rock framework and the bulk elastic modulus of the argillaceous mass to obtain the elastic modulus of the dry rock.
And in the second implementation mode, the elastic modulus of the dry rock is calculated and obtained by adopting a calculation model obtained by experiments according to the porosity or the elastic modulus of the dry rock framework.
S203: according to the porosity, the elastic modulus of the rock particles and the elastic modulus of the dry rock, adoptingAnd calculating to obtain the fluid compression coefficient.
In the present embodiment, the compressibility of water is 444 MPa; the elastic modulus of the fractured tight sandstone comprises rock compressibility, shear modulus and Poisson ratio.
Wherein, CfWhich is indicative of the coefficient of compression of the fluid,Kfthe bulk modulus of elasticity of a fluid is expressed,denotes the porosity, c denotes a fracture shape coefficient, a denotes a fracture aspect ratio, and a is less than or equal to 1, GmaExpressing rock particle shear modulus of elasticity, KmaExpressing the elastic modulus of the rock particles, A expressing the unit transformation coefficient, usingIs obtained by calculation, KdDenotes the dry rock modulus of elasticity and K denotes the saturated rock modulus of elasticity.
The following examples illustrate the calculation of the elastic modulus of rock particles, the elastic modulus of dry rock and the compression coefficient of fluid in this embodiment.
For spherical pore microporosity, the rock compressibility (compressibility is the inverse of bulk modulus) is related to porosity as follows:
in the formula: kdFor drying the elastic modulus, K, of the rockmaIs the rock particle elastic modulus (in GPa); phi is the rock porosity and v is the poisson ratio (in percent).
For a fractured rock, the relationship between the compressibility and porosity of the rock can be written as
Where c is a coefficient related to the shape of the fracture, and α is the fracture aspect length ratio (and α < < 1).
Here, taking j.b.walsh (1965) gives three cases: a coin-like crack, an elliptical crack under the action of plane strain, and an elliptical crack under the action of plane stress.
The compression coefficient of saturated rock is determined in the following specific manner: considering the influence of fluid properties on the elastic modulus of the rock, for equation (2)It can be rewritten as:
in the formula: kfIs the bulk modulus of elasticity (in GPa) of the fluid; gmaShear modulus of elasticity, G, for rock particlesfIs the fluid shear modulus of elasticity (in GPa).
Considering the fluid shear modulus of elasticity to be 0, the saturated rock shear modulus G should be equal to the dry rock shear modulus GdThus the rock particle shear modulus of elasticity may be taken as:
Gma＝G/(1-φ)(5)
make the bulk elastic modulus of pore fluid zero (K)f0), the effective bulk modulus of the dry rock can be found from equation (4) as:
from all the parameters obtained above, the calculation for the fluid compressibility is as follows:
in order to determine the fluid compressibility, considering that the crack holes are filled with fluid and not filled with fluid (namely dry rock), the bulk modulus of elasticity of the dry rock is taken as a background value to eliminate the influence of lithology and pore structure on the calculation of the fluid compressibility, and a ratio (K/K) of saturated modulus of elasticity to dry modulus of elasticity is adoptedd) The fluid compression coefficient C can be obtained by the ratio of the formula (4) to the formula (6)fSpecifically, the method comprises the following steps:
wherein, CfRepresenting the coefficient of compression, K, of the fluidfThe bulk modulus of elasticity of a fluid is expressed,denotes the porosity, c denotes a fracture shape coefficient, a denotes a fracture aspect ratio, and a is less than or equal to 1, GmaExpressing rock particle shear modulus of elasticity, KmaExpressing the elastic modulus of the rock particles, A expressing the unit transformation coefficient, usingIs obtained by calculation, KdDenotes the dry rock modulus of elasticity and K denotes the saturated rock modulus of elasticity.
From the formula (6), knowing the formation porosity phi, the saturation rock elastic modulus and the rock particle elastic modulus, the fluid compressibility can be calculated and used for evaluating the fluid characteristics.
Fig. 3a is a schematic diagram showing a relationship between bulk modulus and porosity when air is saturated in a coin-like fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention; fig. 3b is a schematic diagram showing a relationship between a bulk modulus of elasticity and a fracture minor-major axis when air is saturated in a coin-shaped fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention; fig. 4a is a schematic diagram showing a relationship between bulk modulus and porosity when water is saturated in a coin-shaped fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention; fig. 4b is a schematic diagram of a relationship between bulk modulus of elasticity and fracture minor and major axes when water is saturated in a coin-shaped fracture model in the second embodiment of the method for identifying a gas layer in fractured tight sandstone according to the present invention. In combination with equation (4), it can be seen that the compressibility of the fluid, in addition to the lithology and porosity size, is related to the shape of the porosity and the presence of fractures, as shown in fig. 3a, 3b, 4a and 4 b. In a tight sandstone stratum, intergranular pores or corrosion pores can be approximately regarded as spherical pores, which mainly play a role in a reservoir space, the influence of the porosity change on the fluid compressibility is not large, and the existence of fractures (narrow microcracks) plays a role in communication and has a certain influence on the fluid compressibility, so that the influence of the fractures needs to be properly considered when calculating the compressibility. Because the corresponding logging value is reflected macroscopically by the rock microcosmic, the ratio a of the fracture short-long axis can be about 0.1 by comprehensive consideration, and the following conclusion can be obtained:
1) in near circular holes, the rock bulk modulus of elasticity (or the inverse of the rock compressibility) decreases with increasing porosity, changing more when saturated with water than when saturated with gas.
2) In a fissured pore rock, the rock bulk modulus of elasticity (or the inverse of the rock compression coefficient) varies much more with porosity than in a round pore. Rock saturation water reduces the change of rock bulk modulus of elasticity (or inverse rock compressibility) with porosity, and the change is small when a < 0.01.
3) The pores (or cracks) are filled with water or gas, and the bulk modulus of elasticity (or the compression coefficient) of the rock is greatly different.
Optionally, in the process of calculating the compression coefficient of the fluid, there are the following determination methods for the modulus of elasticity of the dry rock:
the first determination mode is determined by the formulas (1) and (6), but when the argillaceous substances exist, correction is needed, and the obtained dry rock elastic modulus can be corrected by adopting a parallel mode or a serial mode. Wherein,
series mode: kd'＝(1-φ-VSH)Kd+VSHKSHd
Parallel mode: k'd＝(1-φ-VSH)/Kd+VSH/KSHd(8)
In the formula: vSHAs the argillaceous content (in percent); kdModulus of elasticity, K, of dry rock skeletonSHdThe modulus of elasticity in clay form (in PA). The two parameters can also be calculated by longitudinal wave velocity, transverse wave velocity and density skeleton value, and the longitudinal wave velocity of the mudstone can be 100us/ftThe velocity ratio of the longitudinal wave to the transverse wave may be 1.95.
Through popularization, application and statistics, the identification method of the gas layer in the fractured compact sandstone has a coincidence rate of more than 90% in the identification application of the gas layer of 20 wells in the fractured compact sandstone stratum.
The method for identifying the gas layer in the fractured compact sandstone realizes the content of the invention in the FORWARD environment of the oil exploration data center of the oil and gas university of the exploration bureau of China general oil and gas companies, and develops a corresponding program module. The implementation steps in the FORWARD environment specifically include:
loading the time difference (reciprocal of velocity) curves of longitudinal and transverse waves of conventional and full wave train acoustic logging processing in FORWARD software;
calculating the porosity POR (dep) and the shale content VSH (dep) of the conventional logging data by using a porosity model and a shale model;
and calculating the elastic modulus from longitudinal and transverse waves and density data: the rock compression coefficient CB (dep) (or bulk modulus K), the shear modulus G (dep), and the Poisson ratio PR (dep) are calculated according to the following formula:
in the formula: vPIs longitudinal wave velocity (us/ft), VsIs the shear wave velocity (us/ft); DTR is the velocity ratio or the time difference ratio of longitudinal waves and transverse waves; rho is rock bulk density (g/cm)3) And A is a unit conversion coefficient A of 9290.
And determining the elastic modulus of rock particles according to the content of each component of the rock, selecting a proper model to calculate the elastic modulus of the dry rock, and acquiring the fluid compression coefficient according to all the obtained parameters.
Fig. 5 is a schematic structural view of a first embodiment of the identification apparatus for a gas layer in fractured tight sandstone according to the present invention, and as shown in fig. 5, the identification apparatus 10 for a gas layer in fractured tight sandstone includes: a first processing module 11, a second processing module 12 and a third processing module 13. In particular, the method comprises the following steps of,
the first processing module 11 is configured to calculate and obtain porosity and shale content of the fractured compact sandstone by using a porosity model and a shale model according to a longitudinal and transverse wave time difference curve obtained by conventional and full-waverow acoustic logging processing of the fractured compact sandstone in the region to be evaluated, and obtain an elastic modulus of the fractured compact sandstone by combining with pre-obtained density data;
the second processing module 12 is configured to calculate and obtain a fluid compressibility according to the porosity, the shale content, the elastic modulus, and a component content of the fractured tight sandstone, which is obtained in advance;
and the third processing module 13 is configured to judge the fluid property of the fractured tight sandstone according to the fluid compression coefficient of the fractured tight sandstone and the pre-acquired compression coefficient of water.
According to the identification device for the gas layer in the fractured tight sandstone, provided by the embodiment, a first processing module is used for calculating and obtaining a longitudinal wave time difference curve according to the conventional and full wavetrain acoustic logging processing of the fractured tight sandstone in an area to be evaluated, a second processing module is used for calculating and obtaining the porosity and the shale content of the fractured tight sandstone according to a porosity model and a shale model, and obtaining the elastic modulus of the fractured tight sandstone according to the pre-obtained density data, and calculating and obtaining the fluid compression coefficient according to the porosity, the shale content, the elastic modulus and the pre-obtained component content of the fractured tight sandstone, a third processing module is used for comparing the fluid compression coefficient of the fractured tight sandstone with the compression coefficient of water to judge the fluid property of the fractured tight sandstone, and by using the acoustic full wavetrain logging data, the novel method for identifying the gas layer by correcting the fluid compression coefficient effectively improves the precision of evaluating the gas layer in the tight fractured sandstone.
In an embodiment of the apparatus for identifying a gas layer in fractured tight sandstone, in addition to the above embodiment, the third processing module 13 is specifically configured to:
if the difference value between the fluid compression coefficient and the compression coefficient of the water is greater than 0, the fractured compact sandstone is a gas layer;
and if the difference value between the fluid compressibility and the compressibility of the water is less than or equal to 0, the fractured compact sandstone is a water layer.
Optionally, the second processing module 12 is specifically configured to:
determining the elastic modulus of rock particles of the fractured tight sandstone according to the component content of the fractured tight sandstone obtained in advance;
calculating and obtaining the elastic modulus of the dry rock of the fractured compact sandstone according to the porosity, the shale content and the elastic modulus of the rock particles;
according to the porosity, the elastic modulus of the rock particles and the elastic modulus of the dry rock, adoptingCalculating and acquiring the fluid compression coefficient;
wherein, CfRepresenting the coefficient of compression, K, of the fluidfThe bulk modulus of elasticity of a fluid is expressed,denotes the porosity, c denotes a fracture shape coefficient, a denotes a fracture aspect ratio, and a is less than or equal to 1, GmaExpressing rock particle shear modulus of elasticity, KmaExpressing the elastic modulus of the rock particles, A expressing the unit transformation coefficient, usingIs obtained by calculation, KdDenotes the dry rock modulus of elasticity and K denotes the saturated rock modulus of elasticity.
Optionally, the second processing module 12 is further configured to:
calculating according to the longitudinal wave velocity, the transverse wave velocity and the density skeleton of the fractured compact sandstone to obtain the elastic modulus of the dry rock skeleton and the bulk elastic modulus of the argillaceous mass;
calculating according to the elastic modulus of the dry rock framework and the bulk elastic modulus of the argillaceous mass to obtain the elastic modulus of the dry rock; or,
and calculating to obtain the elastic modulus of the dry rock by adopting a calculation model obtained by experiments according to the porosity or the elastic modulus of the dry rock framework.
The device for identifying a gas layer in fractured tight sandstone, provided by this embodiment, is used for executing the technical scheme of any one of the method embodiments shown in fig. 1 to fig. 4b, and the implementation manner and the technical effect are similar, and are not described herein again.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for identifying a gas layer in fractured tight sandstone is characterized by comprising the following steps:
according to the conventional and full-waverow acoustic logging processing of the fractured compact sandstone in the area to be evaluated, obtaining a longitudinal and transverse wave time difference curve, calculating and obtaining the porosity and the argillaceous content of the fractured compact sandstone by adopting a porosity model and a argillaceous model, and obtaining the elastic modulus of the fractured compact sandstone by combining the pre-obtained density data;
calculating and obtaining a fluid compression coefficient according to the porosity, the shale content, the elastic modulus and the component content of the fractured compact sandstone obtained in advance;
and judging the fluid property of the fractured tight sandstone according to the fluid compression coefficient of the fractured tight sandstone and the pre-acquired compression coefficient of water.
2. The method of claim 1, wherein the determining the fluid properties of the fractured tight sandstone from the fluid compressibility of the fractured tight sandstone and the pre-obtained compressibility of water comprises:
if the difference value between the fluid compression coefficient and the compression coefficient of the water is greater than 0, the fractured compact sandstone is a gas layer;
and if the difference value between the fluid compressibility and the compressibility of the water is less than or equal to 0, the fractured compact sandstone is a water layer.
3. The method of claim 2, wherein the obtaining a fluid compressibility based on the porosity, the shale content, the modulus of elasticity, and the pre-obtained fracture tight sandstone component content comprises:
determining the elastic modulus of rock particles of the fractured tight sandstone according to the component content of the fractured tight sandstone obtained in advance;
calculating and obtaining the elastic modulus of the dry rock of the fractured compact sandstone according to the porosity, the shale content and the elastic modulus of the rock particles;
according to the porosity, the elastic modulus of the rock particles and the elastic modulus of the dry rock, adoptingCalculating and acquiring the fluid compression coefficient;
wherein, CfRepresenting the coefficient of compression, K, of the fluidfThe bulk modulus of elasticity of a fluid is expressed,denotes the porosity, c denotes a fracture shape coefficient, a denotes a fracture aspect ratio, and a is less than or equal to 1, GmaExpressing rock particle shear modulus of elasticity, KmaExpressing the elastic modulus of the rock particles, A expressing the unit transformation coefficient, usingIs obtained by calculation, KdDenotes the dry rock modulus of elasticity and K denotes the saturated rock modulus of elasticity.
4. The method of claim 3, wherein the obtaining the dry rock elastic modulus of the fractured tight sandstone from the porosity, the shale content, and the rock particle elastic modulus comprises:
calculating according to the longitudinal wave velocity, the transverse wave velocity and the density skeleton of the fractured compact sandstone to obtain the elastic modulus of the dry rock skeleton and the bulk elastic modulus of the argillaceous mass;
calculating according to the elastic modulus of the dry rock framework and the bulk elastic modulus of the argillaceous mass to obtain the elastic modulus of the dry rock; or,
and calculating to obtain the elastic modulus of the dry rock by adopting a calculation model obtained by experiments according to the porosity or the elastic modulus of the dry rock framework.
5. The method according to any one of claims 1 to 4, wherein the water has a compressibility of 444 MPa; the elastic modulus of the fractured tight sandstone comprises rock compressibility, shear modulus and Poisson ratio.
6. An identification device of gas reservoir in fractured tight sandstone is characterized by comprising:
the first processing module is used for calculating and acquiring the porosity and the shale content of the fractured compact sandstone by adopting a porosity model and a shale model according to a longitudinal and transverse wave time difference curve obtained by conventional and full-waverow acoustic logging processing of the fractured compact sandstone in the area to be evaluated, and acquiring the elastic modulus of the fractured compact sandstone by combining the pre-acquired density data;
the second processing module is used for calculating and obtaining a fluid compression coefficient according to the porosity, the argillaceous content, the elastic modulus and the component content of the fractured compact sandstone obtained in advance;
and the third processing module is used for judging the fluid property of the fractured tight sandstone according to the fluid compression coefficient of the fractured tight sandstone and the pre-acquired compression coefficient of the water.
7. The apparatus according to claim 6, wherein the third processing module is specifically configured to:
if the difference value between the fluid compression coefficient and the compression coefficient of the water is greater than 0, the fractured compact sandstone is a gas layer;
and if the difference value between the fluid compressibility and the compressibility of the water is less than or equal to 0, the fractured compact sandstone is a water layer.
8. The apparatus of claim 7, wherein the second processing module is specifically configured to:
determining the elastic modulus of rock particles of the fractured tight sandstone according to the component content of the fractured tight sandstone obtained in advance;
calculating and obtaining the elastic modulus of the dry rock of the fractured compact sandstone according to the porosity, the shale content and the elastic modulus of the rock particles;
according to the porosity, the elastic modulus of the rock particles and the elastic modulus of the dry rock, adoptingCalculating and acquiring the fluid compression coefficient;
wherein, CfRepresenting the coefficient of compression, K, of the fluidfThe bulk modulus of elasticity of a fluid is expressed,denotes the porosity, c denotes a fracture shape coefficient, a denotes a fracture aspect ratio, and a is less than or equal to 1, GmaExpressing rock particle shear modulus of elasticity, KmaExpressing the elastic modulus of the rock particles, A expressing the unit transformation coefficient, usingIs obtained by calculation, KdDenotes the dry rock modulus of elasticity and K denotes the saturated rock modulus of elasticity.
9. The apparatus of claim 8, wherein the second processing module is further configured to:
calculating according to the longitudinal wave velocity, the transverse wave velocity and the density skeleton of the fractured compact sandstone to obtain the elastic modulus of the dry rock skeleton and the bulk elastic modulus of the argillaceous mass;
calculating according to the elastic modulus of the dry rock framework and the bulk elastic modulus of the argillaceous mass to obtain the elastic modulus of the dry rock; or,
and calculating to obtain the elastic modulus of the dry rock by adopting a calculation model obtained by experiments according to the porosity or the elastic modulus of the dry rock framework.
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