CN110530777B - A method for obtaining the permeability of granular samples - Google Patents
A method for obtaining the permeability of granular samples Download PDFInfo
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- 230000035699 permeability Effects 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 title claims abstract description 24
- 239000002245 particle Substances 0.000 claims abstract description 29
- 239000007789 gas Substances 0.000 claims description 42
- 238000012360 testing method Methods 0.000 claims description 18
- 239000001307 helium Substances 0.000 claims description 14
- 229910052734 helium Inorganic materials 0.000 claims description 14
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 14
- 239000011148 porous material Substances 0.000 claims description 12
- 238000004422 calculation algorithm Methods 0.000 claims description 9
- 238000005259 measurement Methods 0.000 claims description 2
- 238000004364 calculation method Methods 0.000 abstract description 8
- 238000004458 analytical method Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
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Abstract
The embodiment of the invention relates to a method for acquiring the permeability of a particle sample, which can ensure that the square sum of the deviation between a pressure attenuation curve obtained by forward calculation of the determined permeability and an actually measured curve is minimum, and has wider applicability and reliability.
Description
Technical Field
The embodiment of the invention relates to the technical field of petroleum engineering, in particular to a method for acquiring the permeability of a particle sample.
Background
At present, the amount of the mined resources of the shale gas in China is rich, and the shale gas is one of the most strategic alternative energy sources. Shale reservoir evaluation is an important link of shale gas exploration and development, and permeability is one of important indexes of shale reservoir evaluation.
It can be seen from the scanning electron microscope image that organic matter pores, inter-particle (solution) pores, authigenic mineral intercrystalline pores and bedding seams, joint seams, erosion seams and the like are distributed in the shale, the scale of the shale spans six to seven orders of magnitude, and the difference of the seepage capability of pores (seams) with different scales is obvious. For the convenience of analysis, the void space in shale is generally divided into two stages, namely a matrix and a fracture, the matrix permeability is low, and the fracture permeability is high.
In the related technology, a method for determining permeability by adopting pressure decay curve fitting is adopted, permeability underestimation exists in partial samples during low-pressure testing, permeability underestimation exists in partial samples during high-pressure testing, and permeability underestimation exists in partial samples during low-pressure and high-pressure testing. The uncertainty of the result obtained by the existing method for determining the permeability by fitting the pressure attenuation curve is large, and troubles are brought to the understanding of the real seepage characteristics of the sample.
Disclosure of Invention
In view of this, in order to solve the problems in the prior art, embodiments of the present invention provide a method for obtaining a permeability of a particle sample.
In a first aspect, an embodiment of the present invention provides a method for obtaining permeability of a particle sample, where the method includes:
obtaining a curve P (t) of the pressure over time, the reference chamber volume VbVolume V of the sample chamber before the sample is placed thereinsTotal volume of sample VsbAverage particle radius RaTest temperature T and gas density rho of reference cavity before opening of test valve1And the gas density ρ of the sample chamber0;
Based on helium state equation, pressure decay curve P (t) final stable value P2And temperature T, calculating corresponding gas density ρ2And calculating the pore volume V of the samplePPorosity phi, volume ratio K of outer space to inner space of particle samplecAnd the average gas density ρ of the space outside the particles when the test valve is not openc0;
Determining the pressure P corresponding to the beginning of gas entry into the sample3Determining the pressure P from the curve P (t) of the pressure over time3Corresponding time t3;
Selecting all of the time points t greater than the time point3Based on the helium state equation, calculating the gas density rho (t) and the mass fraction FR(t) for ln (F)R(t)) all of which are greater than the time t3Linear fitting is carried out on the measured point and the time t to obtain a slope s1Obtaining a slope s from said1Calculation of the Permeability k0;
Determine permeability K', set K1 to K0And K' is the minimum value, K3 is K0And K', wherein K2 ═ (K1+ K3)/2;
respectively inputting K1, K2 and K3 into a preset mass fraction calculation algorithm, calculating pressure values FR1(T), FR2(T) and FR3(T) of all measuring points at the moment greater than T3, and respectively calculating FR1(T), FR2(T) and FR3(T) and the measured FRThe sum of the squares of the differences (t), denoted as D1, D2, and D3;
if D2 is the minimum of D1, D2 and D3 and the maximum two-by-two relative deviation of D1, D2 and D3 is less than the set value, the permeability is determined to be K2.
In one possible embodiment, the final stable value P is based on the helium state equation, the pressure decay curve P (t), using the following formula2And temperature T, calculating corresponding gas density ρ2Sample pore volume VPPorosity phi, volume ratio K of outer space to inner space of particle samplecAnd the mean gas density ρ of the space outside the particles (containing the reference chamber) when the test valve is not openc0:
In one possible embodiment, the pressure P corresponding to the beginning of the gas entering the sample is determined3The method comprises the following steps:
Based on helium state equation, from rho3And temperature Tcalculated P3。
In one possible embodiment, the mass fraction FR(t) comprising:
in one possible embodiment, the slope s is obtained from the equation1Calculation of the Permeability k0:
Wherein R isaIs the radius of the particle sample; μ is the viscosity coefficient of the gas, cgIs the gas compression factor; alpha is alpha1Is a transcendental equation1 root of (1).
In one possible embodiment, the permeability k' is determined using the following equation, including:
in one possible embodiment, the preset quality score calculating algorithm includes:
According to the technical scheme provided by the embodiment of the invention, the curve P (t) of the pressure changing along with the time and the reference cavity volume V are obtainedbVolume V of the sample chamber before the sample is placed thereinsTotal volume of sample VsbAverage particle radius RaTest temperature T and gas density rho of reference cavity before opening of test valve1And the gas density ρ of the sample chamber0(ii) a Based on helium state equation, pressure decay curve P (t) final stable value P2And temperature T, calculating corresponding gas density ρ2And calculating the pore volume V of the samplePPorosity phi, volume ratio K of outer space to inner space of particle samplecAnd the average gas density ρ of the space outside the particles when the test valve is not openc0(ii) a Determining the pressure P corresponding to the beginning of gas entry into the sample3Determining the pressure P from the curve P (t) of the pressure over time3Corresponding time t3(ii) a Selecting all of the time points t greater than the time point3Based on the helium state equation, calculating the gas density rho (t) and the mass fraction FR(t) for ln (F)R(t)) all ofGreater than said time t3Linear fitting is carried out on the measured point and the time t to obtain a slope s1Obtaining a slope s from said1Calculation of the Permeability k0(ii) a Determine permeability K', set K1 to K0And K' is the minimum value, K3 is K0And K', wherein K2 ═ (K1+ K3)/2; respectively inputting K1, K2 and K3 into a preset mass fraction calculation algorithm, calculating pressure values FR1(T), FR2(T) and FR3(T) of all measuring points at the moment greater than T3, and respectively calculating FR1(T), FR2(T) and FR3(T) and the measured FRThe sum of the squares of the differences (t), denoted as D1, D2, and D3; if D2 is the minimum of D1, D2 and D3 and the maximum two-by-two relative deviation of D1, D2 and D3 is less than the set value, the permeability is determined to be K2. The method can ensure that the square sum of the deviation of the pressure attenuation curve obtained by the determined permeability forward calculation and the actually measured curve is minimum, and has wider applicability and reliability.
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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 used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the embodiments of the present invention, and it is also possible for a person skilled in the art to obtain other drawings based on the drawings.
Fig. 1 is a schematic flow chart of an implementation of a method for obtaining permeability of a particle sample according to an embodiment of the present invention.
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.
For the convenience of understanding of the embodiments of the present invention, the following description will be further explained with reference to specific embodiments, which are not to be construed as limiting the embodiments of the present invention.
As shown in fig. 1, an implementation flow diagram of a method for obtaining a permeability of a particle sample according to an embodiment of the present invention is shown, and the method specifically includes the following steps:
step 1, obtaining a curve P (t) of pressure changing along with time and a reference cavity volume VbVolume V of the sample chamber before the sample is placed thereinsTotal volume of sample VsbAverage particle radius RaTest temperature T and gas density rho of reference cavity before opening of test valve1And the gas density ρ of the sample chamber0;
step 3, determining the corresponding pressure P of the gas entering the sample3Wherein is determined by a formulaEquation of state based on helium consisting of rho3And temperature Tcalculated P3。
Determining the pressure P from the curve P (t) of the pressure over time3Corresponding time t3All measured point time values are expressed as t3For zero point recalculation, take time greater than t3The first measurement point of (1), the time of which is denoted as t4The corresponding pressure is denoted as P4。
Step 4, all the time points greater than the time t are selected3Is measured (i.e. all time is selected to be greater than or equal to t)4Measure point) of the helium gas, calculating the gas density ρ (t) and the mass fraction F based on the helium gas state equationR(t) for ln (F)R(t)) all of which are greater than the time t3Measure point (i.e., all times greater than or equal to t)4Measured point) and time t to obtain slope s1Obtaining a slope s from said1Calculation of the Permeability k0Wherein the permeability k is calculated according to the formula0;
Wherein R isaIs the radius of the particle sample; μ is the viscosity coefficient of the gas, cgIs the gas compression factor; alpha is alpha1Is a transcendental equation1 root of (1).
Step 5, determining the permeability k', and solving the following equation:
step 6, setting K1 as K0And K' is the minimum value, K3 is K0And K', wherein K2 ═ (K1+ K3)/2;
step 7, inputting K1, K2 and K3 into a preset mass fraction calculation algorithm, calculating pressure values FR1(T), FR2(T) and FR3(T) of all measuring points at the moment of being greater than T3 by taking T3 as a starting point, and calculating FR1(T), FR2(T) and FR3(T) and an actually measured FR(t) the sum of the squares of the differences, denoted as D1, D2, and D3, wherein the predetermined mass fraction calculation algorithm comprises:
Step 8, if D2 is the minimum value of D1, D2 and D3 and the maximum pairwise relative deviation of D1, D2 and D3 is less than the set value (relative deviation is defined as the ratio of the absolute value of the difference between the two variables to the mean value of the two variables), determining the permeability as K2
Step 9, if D2 is the minimum value among D1, D2 and D3, but the maximum pairwise relative deviation of the three is greater than a set value, setting K1 to (K1+ K2)/2 and K3 to (K3+ K2)/2, and continuing to execute step 7;
step 10, if D1 is the minimum value among D1, D2 and D3, setting K3 to K2, K2 to K1, and K1 to 2 to K2 to K3, and continuing to execute step 7;
and 11, if the D3 is the minimum value of the D1, the D2 and the D3, setting K1 to K2, setting K2 to K3, setting K3 to 2 to K2 to K1, and continuing to execute the step 7.
In the embodiment of the invention, aiming at the problem that the permeability is underestimated when the existing method for determining the permeability by fitting the pressure attenuation curve in the permeability test of the particle sample is applied to a part of samples under a certain pressure condition, the invention provides a new analysis method, which can ensure that the square sum of the deviation between the pressure attenuation curve obtained by forward calculation of the determined permeability and an actually measured curve is minimum, and has wider applicability and reliability.
Those of skill would further appreciate that the various illustrative components and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied in hardware, a software module executed by a processor, or a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
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| IT1255750B (en) * | 1992-08-27 | 1995-11-15 | Agip Spa | PROCEDURE FOR EXPERIMENTALLY RECOVERING THE CAPILLARY PRESSURE CURVE IN A POROUS MEDIUM |
| US7171843B2 (en) * | 2004-10-01 | 2007-02-06 | Lasswell Patrick M | Electronic humidity chamber for vapor desorption to determine high capillary pressures |
| CN103226089B (en) * | 2013-03-26 | 2015-07-08 | 中国石油天然气股份有限公司 | Shale gas permeability determination method |
| CN204302156U (en) * | 2014-12-27 | 2015-04-29 | 重庆地质矿产研究院 | Experimental device for measure low permeability rock specimen permeability and porosity |
| CN105910971B (en) * | 2016-04-14 | 2018-05-18 | 西南石油大学 | The simultaneous measuring method of rich organic matter compact rock core gas permeability and diffusion coefficient |
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