CN116026740A - Volcanic overburden permeability calculation method based on inter-grain Kong Bai percentage - Google Patents
Volcanic overburden permeability calculation method based on inter-grain Kong Bai percentage Download PDFInfo
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Abstract
The invention belongs to the field of evaluation and research of tight gas reservoirs and discloses a volcanic overburden permeability calculation method based on an inter-grain Kong Bai percentage. The method comprises the steps of testing the overburden pressure permeability values of core columns under different confining pressure conditions, obtaining Kong Bai percentages among core columns by using a fractal theory, establishing a overburden pressure permeability calculation model based on Kong Bai percentages among the core columns, calculating the overburden pressure permeability values by using the overburden pressure permeability calculation model, introducing pore types and confining pressure into the permeability calculation model for the first time, and establishing a brand-new overburden pressure permeability calculation model, which has important scientific guidance significance for evaluating a tight gas reservoir.
Description
Technical Field
The invention belongs to the field of evaluation and research of tight gas reservoirs, and particularly relates to a volcanic overburden permeability calculation method based on an inter-grain Kong Bai percentage.
Background
The permeability is a key parameter for reservoir evaluation, and accurate determination of the permeability is important for improving the recovery ratio of the oil and gas field, and plays a role in exploration and development of the oil and gas field.
Based on high pressure mercury and nuclear magnetic resonance micro-pore structure parameters, many permeability calculation models have been proposed, including the coatings model, the SDR (sR Bei Xiedao mol laboratory) model, and the pittman model. These models can be represented by the following formula:
Log(K)＝A+B Log(φ)+C Log(f)
where K represents permeability, φ represents porosity, f is a variable, f in the coatings model, SDR model and pittman model is FFI/BVI (ratio of free water of nuclear magnetism to saturation of irreducible water), nuclear magnetism T, respectively 2 Spectrum geometric mean and r i (pore throat radius for mercury saturation i%). A. B, C are parameters to fit to the multiple linear regression equation.
However, the above method has three disadvantages. First, conventional methods have poor application in tight reservoirs. Because the pore structure of a tight reservoir is quite complex, the flow of fluid in the reservoir is nonlinear, and the traditional permeability calculation model is only applicable to a conventional reservoir.
Second, conventional methods do not introduce pore types into the permeability calculation model. The tight reservoir undergoes various diagenetic effects during geological history, so that the pore types are various, and the pore sizes and connectivity of different pore types are different, so that the pore types have great influence on the permeability of the tight reservoir.
Third, the conventional approach does not introduce confining pressure into the permeability calculation model. In a tight sandstone reservoir, due to the existence of a slip effect, the air permeability measured by the conventional method is different from the actual permeability to a certain extent, and the Kerr permeability obtained by using the core-covered pore permeability test method can more accurately reflect the seepage characteristics of the tight reservoir.
In order to overcome the defect of the traditional method in the calculation of the permeability of the tight reservoir, improvement is very necessary for the traditional method, confining pressure is introduced into the calculation of the permeability, a new overburden permeability calculation model is deduced, and the requirement of fine characterization of the permeability of the tight reservoir is met.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a volcanic rock overburden permeability calculation method based on an inter-grain Kong Bai percentage, which introduces pore types and confining pressures into a permeability calculation model for the first time, so that the problem that the existing method does not consider the influence of pore classification and confining pressures on the permeability, and the calculation precision is insufficient is solved.
The above object of the present invention is achieved by the following technical solutions:
a volcanic overburden permeability calculation method based on an inter-grain Kong Bai percentage comprises the following steps:
1. cutting a volcanic rock sample into standard core columns, and carrying out pretreatment before experiments;
2. testing the overburden permeability value of the core column under different confining pressure conditions;
3. performing a high-pressure mercury injection experiment on the core column, and obtaining Kong Bai percent among the core columns by utilizing a fractal theory;
4. analyzing the relation between the overburden permeability and the Kong Bai percent between grains, and establishing a overburden permeability calculation model based on Kong Bai percent between grains;
5. for a known inter-grain Kong Bai percent core column, the overburden permeability value is calculated by using a overburden permeability calculation model.
Wherein, the diameter of the standard core column in the step 1 is 2.5cm, and the length is 2-3cm.
The pretreatment step in the step 1 is as follows: firstly, placing a core column into a high-temperature high-pressure oil washing instrument, and washing off residual oil and slurry in the core by adopting an organic solvent; then placing the core column after oil washing into a crucible, repeatedly adding distilled water for boiling, and washing out residual salt in the core column; and finally, placing the rock core column after salt washing into an oven, heating to 100 ℃, and removing water in the rock core column.
The confining pressure in the step 2 is one of 5, 10, 15, 20 and 25 MPa.
In the step 3, the model of the high-pressure mercury-pressing experimental instrument is AutoPore III 9505, and the experiment is executed according to the flow prescribed by the standard of the determination of rock capillary pressure curve GB/T29171-2012.
In the step 3, the step of obtaining the inter-grain Kong Bai percentage is as follows:
a. drawing into mercury saturation S Hg With capillary pressure P c Is a double logarithmic scatter plot of S Hg And P c The relationship of (2) is shown in formula (1):
Log(1-S Hg )＝(D-3)Log(P c ) (1)
wherein: s is S Hg The unit is mercury saturation; p (P) c Capillary pressure in MPa; d is the fractal dimension of the pore, and is dimensionless;
b.Log(1-S Hg )-Log(P c ) The curve is divided into two sections, which shows that the volcanic rock sample has two fractal dimensions, corresponding to two pores, namely inter-grain pores and intra-grain pores. The mercury inlet percentage corresponding to the inflection point of the curve is Kong Bai percent among grains.
The step 4 is based on the overburden permeability calculation model of Kong Bai percent among grains as formula (2)
Wherein: the unit is mD, which is the overpressure permeability when the pressure is equal to P; vi is the inter-particle Kong Bai percent in units; A. b is a coefficient, and is dimensionless.
Compared with the prior art, the invention has the beneficial effects that: the pore type and confining pressure are introduced into the osmotic calculation model for the first time, and a brand new overburden pressure permeability calculation model is established. The inter-particle pore proportion influences the reservoir seepage capability and thus the permeability, and the method can effectively improve the volcanic reservoir permeability calculation accuracy based on the inter-particle Kong Bai-percent permeability calculation model, and has important scientific guidance significance for the evaluation of the tight gas reservoir.
Drawings
The invention will be further described with reference to the drawings and the detailed description;
FIG. 1 is a flow chart of a volcanic overburden permeability calculation method based on an inter-grain Kong Bai percentage provided by the invention;
fig. 2 is a fractal dimension calculation schematic diagram of a volcanic overburden permeability calculation method based on an inter-grain Kong Bai percentage provided by the invention;
FIG. 3 is a graph showing the comparison of calculated permeability and measured permeability under different confining pressure conditions according to the method for calculating the permeability of the volcanic rock overburden based on the Kong Bai percent between grains.
Detailed Description
The present invention is described in detail below by way of specific examples, but the scope of the present invention is not limited thereto. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and all experimental equipment, materials, reagents, etc. used can be obtained from commercial sources.
Example 1
The total of 10 volcanic samples used in the experiment were taken from the Songliao basin southern flint group tuff reservoir.
Referring to fig. 1, a method for calculating the overburden permeability of volcanic based on the Kong Bai percent of inter-grains comprises the following steps:
1) Drilling volcanic rock samples of the tuff reservoir of the southern flint group of the Songliao basin by using a deep hole drilling machine;
2) Cutting the volcanic rock sample into core columns with diameters of 2.5cm and lengths of 2-3 cm;
3) Cutting a flat section by using a core cutter;
4) Placing the core column into a high-temperature high-pressure oil washing instrument, and washing away residual oil and slurry in the core by adopting an organic solvent;
5) Placing the core column after oil washing into a crucible, repeatedly adding distilled water for boiling, and washing residual salt in the core column;
6) Placing the rock core column after salt washing into an oven, heating to 100 ℃, and removing water in the rock core column;
7) The method comprises the steps of testing the overburden permeability values of a core column under different confining pressure conditions, wherein the overburden permeability experimental instrument model is a KSY-overburden pore permeability tester, and the experiment is executed according to a flow prescribed by SY/T6385-2016 'overburden rock pore and permeability testing method';
8) Performing a high-pressure mercury injection experiment on the core column, and obtaining Kong Bai percent among the core columns by utilizing a fractal theory;
9) Analyzing the relation between the overburden permeability and the Kong Bai percent between grains, and establishing a overburden permeability calculation model based on Kong Bai percent between grains;
10 For a core column of known inter-grain Kong Bai percent, the overburden permeability value is calculated by using a overburden permeability calculation model.
The calculated 10 core column overburden permeability values are shown in table 1
TABLE 1 core column overburden permeability and inter-granular pore ratio
The model of the high-pressure mercury-pressing experimental instrument is AutoPore III 9505, and the experiment is carried out according to the flow prescribed by the standard of GB/T29271-2012 determination of rock capillary pressure curve.
The step 8) of obtaining Kong Bai percent among the core columns specifically comprises the following steps:
drawing into mercury saturation S Hg With capillary pressure P c Is a double logarithmic scatter plot of S Hg And P c The relationship of (2) is shown in formula (1):
Log(1-S Hg )＝(D-3)Log(P c ) (1)
wherein: s is S Hg The unit is mercury saturation; p (P) c Capillary pressure in MPa; d is the fractal dimension of the pore and has no dimension.
FIG. 2 is a 10 core column Log (1-S Hg )-Log(P c ) Graph diagram.
The step 9) is based on the overburden permeability calculation model of Kong Bai percent among grains as formula (2)
Wherein: the unit is mD, which is the overpressure permeability when the pressure is equal to P; vi is the inter-particle Kong Bai percent in units; A. b is a coefficient, dimensionless;
p is equal to 5, 10, 15, 20 or 25MPa;
the overburden permeability calculation model coefficients a and B are shown in table 2:
TABLE 2
As shown in fig. 3, the overburden permeability calculated by equation (2) is very close to the measured value, thus demonstrating that the volcanic overburden permeability calculation method based on the inter-grain Kong Bai percentage is feasible and reliable.
The above-described embodiments are only preferred embodiments of the invention, and not all embodiments of the invention are possible. Any obvious modifications thereof, which would be apparent to those skilled in the art without departing from the principles and spirit of the present invention, should be considered to be included within the scope of the appended claims.
Claims (8)
1. The volcanic overburden permeability calculation method based on the inter-grain Kong Bai percentage is characterized by comprising the following steps of:
(1) Cutting a volcanic rock sample into standard core columns, and carrying out pretreatment before experiments;
(2) Testing the overburden permeability value of the core column under different confining pressure conditions;
(3) Performing a high-pressure mercury injection experiment on the core column, and obtaining Kong Bai percent among the core columns by utilizing a fractal theory;
(4) Analyzing the relation between the overburden permeability and the Kong Bai percent between grains, and establishing a overburden permeability calculation model based on Kong Bai percent between grains;
(5) For a known inter-grain Kong Bai percent core column, the overburden permeability value is calculated by using a overburden permeability calculation model.
2. The method for calculating the overburden permeability of volcanic based on the inter-grain Kong Bai percentage according to claim 1, wherein the standard core column in the step (1) has a diameter of 2.5cm and a length of 2-3cm.
3. The method for calculating the permeability of the volcanic rock based on the percentage Kong Bai among grains according to claim 1, wherein the preprocessing step in the step (1) is as follows: firstly, placing a core column into a high-temperature high-pressure oil washing instrument, and washing off residual oil and slurry in the core by adopting an organic solvent; then placing the core column after oil washing into a crucible, repeatedly adding distilled water for boiling, and washing out residual salt in the core column; and finally, placing the rock core column after salt washing into an oven to remove water in the rock core column.
4. The method of claim 3, wherein the temperature of the oven in which the core column after salt washing in step (1) is placed is 100 ℃.
5. The method of claim 1, wherein the confining pressure in step (2) is one of 5, 10, 15, 20 and 25 MPa.
6. The method for calculating the volcanic overburden permeability based on the inter-grain Kong Bai percentage according to claim 1, wherein in the step (3), the model of the high-pressure mercury injection experimental apparatus is AutoPore iii 9505, and the experiment is performed according to a procedure prescribed in the standard of determination of rock capillary pressure curve GB/T29171-2012.
7. The method for calculating the permeability of volcanic cover based on the percentage Kong Bai among grains according to claim 1, wherein in the step (3), the step of obtaining the percentage Kong Bai among grains is:
a. drawing into mercury saturation S Hg With capillary pressure P c Is a double logarithmic scatter plot of S Hg And P c The relationship of (2) is shown in formula (1):
Log(1-S Hg )＝(D-3)Log(P c ) (1)
wherein: s is S Hg The unit is mercury saturation; p (P) c Capillary pressure in MPa; d is the fractal dimension of the pore, and is dimensionless;
b.Log(1-S Hg )-Log(P c ) The curve is divided into two sections, the volcanic rock sample has two fractal dimensions, corresponding to two pores, namely inter-grain pores and intra-grain pores, and the mercury inlet percentage corresponding to the inflection point of the curve is Kong Bai percent between grains.
8. The method of claim 1, wherein the step (4) is based on a model of the inter-grain Kong Bai percent of the overburden permeability calculated by the inter-grain Kong Bai percent of the overburden permeability calculated by the formula (2)
Wherein: the unit is mD, which is the overpressure permeability when the pressure is equal to P; vi is the inter-particle Kong Bai percent in units; A. b is a coefficient, dimensionless, e is a natural constant, and dimensionless.
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