CN113919534A - Method and device for predicting development effect of shale gas well - Google Patents
Method and device for predicting development effect of shale gas well Download PDFInfo
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Abstract
The invention discloses a method and a device for predicting the development effect of a shale gas well, wherein the method comprises the following steps: obtaining the mud density and mud circulation temperature of the shale gas core well during full-diameter core coring; collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature; establishing a diffusion model of desorption gas quantity and desorption time to obtain a unified diffusion equation; calculating the seepage rate of free gas along a shale bedding seam Darcy in the full-diameter core coring process of the shale gas coring well based on a unified diffusion equation; based on the mud density and the rate of darcy seepage, a development effect evaluation coefficient is calculated. The method can effectively avoid the necessity of long-term productivity data of shale gas wells, is suitable for shale gas wells in areas with low exploration degree, namely has instantaneity in the application of exploring new areas, can provide reference data of first time, is also suitable for shale gas wells in exploration mature areas, and is a rapid, effective, convenient and wide-applicability prediction method.
Description
Technical Field
The invention belongs to the technical field of oil-gas exploration and development, and particularly relates to a method and a device for predicting the development effect of a shale gas well.
Background
The shale gas well development effect prediction is generally an oil reservoir development engineering experience technology, joint analysis is carried out according to the productivity data of the existing shale gas wells, the future production data of the shale gas wells are calculated, the development effect of the shale gas wells is predicted, and the exploitation reserves of the shale gas wells are finally evaluated.
The methods commonly used at present are the ARPS (descending development) model, SEDM (structural equation) model and Duong (descending yield) model, which employ the yield decay with time. The Ponware et al (2017) construct an attenuation model of a log-log plate by using the measured data of the shale gas well on the basis; and (4) calculating a yield decreasing curve by adopting yield attenuation and methane isotope weight change by using the upward cloud peak (2017). Wang military Lei et al (2014) have established a comprehensive model of a multi-data analysis method taking flow state identification, analytical analysis and empirical analysis as the core for eliminating the uncertainty of a single model. Meanwhile, the method for predicting the shale gas well productivity based on the material balance equation is established by considering the elastic energy influence of the adsorbed gas and the abnormal high-pressure gas reservoir rock in Guo Yandong (2018). Starting from the shale gas reservoir logging evaluation, the Wangzhongdong (2017) introduces reservoir parameters such as total organic carbon content, mineral components, porosity, saturation, gas content and brittleness index and the relation between factors such as well track and fracturing effect and the yield of a horizontal well on the basis of production data, thereby evaluating the development effect of the shale gas well.
The production data adopted based on the research method are shale gas well data which are already explored for 1-2 years, and the application range of the shale gas well data is mainly that development wells last for years. And the method can not be applied to a new area or a peripheral area with low research degree in the early exploration. Therefore, a new method is needed to be explored to be suitable for shale gas wells in areas with low exploration degrees, and a fast, effective and global shale gas development effect prediction method is achieved.
Disclosure of Invention
The invention aims to provide a method and a device for predicting the development effect of a shale gas well, which are suitable for shale gas wells in areas with low exploration degrees.
In view of the above, the invention provides a method and a device for predicting the development effect of a shale gas well, which at least solve the problem that the conventional method for predicting the development effect of the shale gas well cannot be applied to shale gas wells in areas with low exploration degree.
In a first aspect, the invention provides a method for predicting the development effect of a shale gas well, which comprises the following steps: obtaining the mud density and mud circulation temperature of the shale gas core well during full-diameter core coring; collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature; establishing a diffusion model of the desorption gas quantity and the desorption time to obtain a unified diffusion equation; calculating the rate of free gas along shale bedding seam Darcy seepage in the full-diameter core coring process of the shale gas coring well based on the unified diffusion equation; calculating a development effectiveness evaluation coefficient based on the mud density and the Darcy seepage rate.
Optionally, the unified diffusion equation is:
wherein Q istIs the desorption gas quantity, Q, of the shale at the time t∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
Optionally, the rate of free gas seepage along the shale bedding seam darcy in the full-diameter core coring process of the shale gas coring well is a tangent slope of the unified diffusion equation at the initial point of desorption time.
Optionally, the development effect evaluation coefficient is calculated by using the following formula:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the speed of Darcy seepage, namely the tangent slope of a unified diffusion equation at the starting point of desorption time, and d is the slurry density.
Optionally, the sampling time interval of the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature is 30s to 60 s.
In a second aspect, the present invention further provides a device for predicting the development effect of a shale gas well, including: the mud density detection equipment is used for obtaining the mud density of the shale gas coring well during full-diameter core coring; the field desorption instrument is used for collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature; a processor coupled to the in situ desorber, the processor performing the steps of: establishing a diffusion model of the desorption gas quantity and the desorption time to obtain a unified diffusion equation; calculating the rate of free gas along shale bedding seam Darcy seepage in the full-diameter core coring process of the shale gas coring well based on the unified diffusion equation; calculating a development effectiveness evaluation coefficient based on the mud density and the Darcy seepage rate.
Optionally, the unified diffusion equation is:
wherein Q istIs the desorption gas quantity, Q, of the shale at the time t∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
Optionally, the rate of free gas seepage along the shale bedding seam darcy in the full-diameter core coring process of the shale gas coring well is a tangent slope of the unified diffusion equation at the initial point of desorption time.
Optionally, the development effect evaluation coefficient is calculated by using the following formula:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the speed of Darcy seepage, namely the tangent slope of a unified diffusion equation at the starting point of desorption time, and d is the slurry density.
Optionally, the sampling time interval of the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature is 30s to 60 s.
The invention has the beneficial effects that: the shale gas well development effect prediction method establishes a desorption gas volume and desorption time diffusion model to obtain a unified diffusion equation, calculates the Darcy seepage rate of free gas along the shale bedding crack in the shale gas core taking process based on the unified diffusion equation, and obtains a development effect evaluation coefficient according to the mud density and the Darcy seepage rate, thereby effectively avoiding the necessity of long-term productivity data of shale gas wells.
The present invention has other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
FIG. 1 shows a flow chart of a method for predicting the effectiveness of shale gas well development according to an embodiment of the present invention.
Fig. 2 is a schematic diagram illustrating slope calculation based on a desorption gas amount and a desorption time diffusion model of a shale gas well development effect prediction method according to an embodiment of the invention.
Fig. 3 shows a block diagram of a shale gas well development effect prediction apparatus according to an embodiment of the present invention.
102. A mud density detection device; 104. a field desorption instrument; 106. a processor.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
The invention provides a method for predicting the development effect of a shale gas well, which comprises the following steps: obtaining the mud density and mud circulation temperature of the shale gas core well during full-diameter core coring; collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature; establishing a diffusion model of desorption gas quantity and desorption time to obtain a unified diffusion equation; calculating the seepage rate of free gas along a shale bedding seam Darcy in the full-diameter core coring process of the shale gas coring well based on a unified diffusion equation; based on the mud density and the rate of darcy seepage, a development effect evaluation coefficient is calculated.
With the development practice of shale gas in recent years, the development effect of shale gas is closely related to the occurrence ratio of free gas, and the free gas ratio is high, so that an abnormally high pressure coke-rock dam area is a typical area with excellent development effect.
In the coring process of the full-diameter core (from the bottom to the wellhead), free gas mainly takes Darcy seepage along the shale bedding joint; and as the core rises at a constant speed in the coring process, the internal and external pressure balance of the core at the bottom of the well is changed into the internal and external equal pressure difference in the rising process, and the Darcy seepage rate is a fixed value. Meanwhile, the slurry density is high, so that the loss of free gas is less, and the initial desorption amount of the wellhead is high. After the shale core reaches the well mouth, the shale gas is mainly diffused, and the Darcy seepage and the well mouth diffusion desorption in the coring process are in continuous transition because a certain pressure difference is kept between the inside and the outside of the core at the early desorption stage of the well mouth (the shale gas flow in the early stage of the shale core soaking experiment is still in a continuous bead-shaped state and can be proved).
In the field gas content test of shale, the desorption diffusion data of shale gas can be obtained, and based on the continuous transition process, how to obtain the Darcy seepage rate of free gas becomes a key, so that the development effect of the shale gas is predicted.
Specifically, the mud density and the mud circulation temperature of the shale gas core well after the full-diameter core coring are recorded, the desorption gas volume of the full-diameter core of the shale gas core well at the mud circulation temperature is collected, a diffusion model of the desorption gas volume and the desorption time on site is established, a unified diffusion equation is obtained, the rate of free gas reaching west seepage along shale bedding seams in the process of the full-diameter core coring of the shale gas core well is obtained, and the development effect evaluation coefficient is obtained according to the rate of the west seepage along the shale bedding seams and the mud density.
According to an exemplary embodiment, a diffusion model of desorption gas volume and desorption time is established by the shale gas well development effect prediction method, a unified diffusion equation is obtained, the rate of free gas along shale bedding cracks in the shale gas coring process is calculated based on the unified diffusion equation, a development effect evaluation coefficient is obtained according to mud density and the rate of Darcy seepage, the necessity of long-term productivity data of shale gas wells can be effectively avoided, the shale gas well development effect prediction method is suitable for shale gas wells in regions with low exploration degree, namely the shale gas well development effect prediction method is applicable to shale gas wells in regions with low exploration degree, has instantaneity in application to new exploration regions, can provide reference data of first time, is also suitable for shale gas wells in exploration mature regions, and is a rapid, effective, convenient and widely applicable prediction method.
Alternatively, the unified diffusion equation is:
wherein Q istIs the desorption gas quantity, Q, of the shale at the time t∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
Specifically, a diffusion model of the desorption gas amount and the desorption time is established based on the desorption gas amount to obtain a unified diffusion equation, and the unified diffusion equation has global property and is more stable than desorption data, so that the influence of abnormal data points in the initial desorption stage can be eliminated.
Alternatively, the tangent slope of the diffusion equation at the beginning point of desorption time, in which the rate of free gas seepage along the shale bedding seam Darcy is unified in the full-diameter core coring process of the shale gas coring well.
Specifically, the tangential slope of the unified diffusion equation is the rate of free gas along the shale bedding seam darcy seepage during the coring process (full diameter core from bottom to top). The principle is based on continuous transition of Darcy seepage and wellhead diffusion in the coring process.
Alternatively, the development effect evaluation coefficient is calculated using the following formula:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the speed of Darcy seepage, namely the tangent slope of a unified diffusion equation at the starting point of desorption time, and d is the slurry density.
Specifically, the development effect evaluation coefficient is dimensionless, and the influence of the mud density on the rate of free gas Darcy seepage is eliminated to obtain the development effect evaluation coefficient, so that different coring wells can be compared.
Alternatively, the sampling time interval of the desorption gas volume of the full-diameter core of the shale gas core well at the mud circulation temperature is 30s to 60 s.
Specifically, the collection frequency of the desorption gas volume of the full-diameter core of the shale gas core well at the mud circulation temperature is continuous equal interval measurement, and the collection is carried out once every 30-60 s, preferably 30 s.
In a second aspect, the present invention further provides a device for predicting the development effect of a shale gas well, including: the mud density detection equipment is used for obtaining the mud density of the shale gas coring well during full-diameter core coring; the field desorption instrument is used for collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature; the processor is connected with the on-site desorption instrument and executes the following steps: establishing a diffusion model of desorption gas quantity and desorption time to obtain a unified diffusion equation; calculating the seepage rate of free gas along a shale bedding seam Darcy in the full-diameter core coring process of the shale gas coring well based on a unified diffusion equation; based on the mud density and the rate of darcy seepage, a development effect evaluation coefficient is calculated.
With the development practice of shale gas in recent years, the development effect of shale gas is closely related to the occurrence ratio of free gas, and the free gas ratio is high, so that an abnormally high pressure coke-rock dam area is a typical area with excellent development effect.
In the coring process of the full-diameter core (from the bottom to the wellhead), free gas mainly takes Darcy seepage along the shale bedding joint; and as the core rises at a constant speed in the coring process, the internal and external pressure balance of the core at the bottom of the well is changed into the internal and external equal pressure difference in the rising process, and the Darcy seepage rate is a fixed value. Meanwhile, the slurry density is high, so that the loss of free gas is less, and the initial desorption amount of the wellhead is high. After the shale core reaches the well mouth, the shale gas is mainly diffused, and the Darcy seepage and the well mouth diffusion desorption in the coring process are in continuous transition because a certain pressure difference is kept between the inside and the outside of the core at the early desorption stage of the well mouth (the shale gas flow in the early stage of the shale core soaking experiment is still in a continuous bead-shaped state and can be proved).
In the field gas content test of shale, the desorption diffusion data of shale gas can be obtained, and based on the continuous transition process, how to obtain the Darcy seepage rate of free gas becomes a key, so that the development effect of the shale gas is predicted.
Specifically, the mud density of the shale gas core well during full-diameter core coring is obtained through mud density detection equipment, the desorption gas quantity of the full-diameter core of the shale gas core well at the mud circulation temperature is collected through a field desorption instrument, a diffusion model of the field desorption gas quantity and the desorption time of shale is built through a processor, a unified diffusion equation is obtained, the rate of free gas reaching west seepage along shale bedding seams in the full-diameter core coring process of the shale gas core well is obtained, and a development effect evaluation coefficient is obtained according to the rate of the west seepage along the shale bedding seams and the mud density.
According to an exemplary embodiment, the shale gas well development effect prediction device establishes a diffusion model of desorption gas volume and desorption time to obtain a unified diffusion equation, calculates the Darcy seepage rate of free gas along a shale bedding seam in the shale gas coring full-diameter core coring process based on the unified diffusion equation, and obtains a development effect evaluation coefficient according to mud density and the Darcy seepage rate, so that the necessity of long-term productivity data of the shale gas well can be effectively avoided.
Alternatively, the unified diffusion equation is:
wherein Q istIs the desorption gas quantity, Q, of the shale at the time t∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
Specifically, a diffusion model of the desorption gas amount and the desorption time is established based on the desorption gas amount to obtain a unified diffusion equation, and the unified diffusion equation has global property and is more stable than desorption data, so that the influence of abnormal data points in the initial desorption stage can be eliminated.
Alternatively, the tangent slope of the diffusion equation at the beginning point of desorption time, in which the rate of free gas seepage along the shale bedding seam Darcy is unified in the full-diameter core coring process of the shale gas coring well.
Specifically, the tangential slope of the unified diffusion equation is the rate of free gas along the shale bedding seam darcy seepage during the coring process (full diameter core from bottom to top). The principle is based on continuous transition of Darcy seepage and wellhead diffusion in the coring process.
Alternatively, the development effect evaluation coefficient is calculated using the following formula:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the speed of Darcy seepage, namely the tangent slope of a unified diffusion equation at the starting point of desorption time, and d is the slurry density.
Specifically, the development effect evaluation coefficient is dimensionless, and the influence of the mud density on the rate of free gas Darcy seepage is eliminated to obtain the development effect evaluation coefficient, so that different coring wells can be compared.
Alternatively, the sampling time interval of the desorption gas volume of the full-diameter core of the shale gas core well at the mud circulation temperature is 30s to 60 s.
Specifically, the collection frequency of the desorption gas volume of the full-diameter core of the shale gas core well at the mud circulation temperature is continuous equal interval measurement, and the collection is carried out once every 30-60 s, preferably 30 s.
Example one
FIG. 1 shows a flow chart of a method for predicting the effectiveness of shale gas well development according to an embodiment of the present invention. Fig. 2 is a schematic diagram illustrating slope calculation based on a desorption gas amount and a desorption time diffusion model of a shale gas well development effect prediction method according to an embodiment of the invention.
With reference to fig. 1 and fig. 2, the method for predicting the development effect of the shale gas well includes:
step 1: obtaining the mud density and mud circulation temperature of the shale gas core well during full-diameter core coring;
step 2: collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature;
and step 3: establishing a diffusion model of desorption gas quantity and desorption time to obtain a unified diffusion equation;
wherein, the unified diffusion equation is:
wherein Q istIs the desorption gas quantity, Q, of the shale at the time t∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
And 4, step 4: calculating the seepage rate of free gas along a shale bedding seam Darcy in the full-diameter core coring process of the shale gas coring well based on a unified diffusion equation;
the tangential slope of the diffusion equation at the initial point of desorption time is the unified diffusion equation for the free gas seepage rate along the shale bedding crack Darcy in the full-diameter core coring process of the shale gas coring well.
And 5: based on the mud density and the rate of darcy seepage, a development effect evaluation coefficient is calculated.
Wherein, the following formula is adopted to calculate the evaluation coefficient of the development effect:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the speed of Darcy seepage, namely the tangent slope of a unified diffusion equation at the starting point of desorption time, and d is the slurry density.
Wherein the sampling time interval of the desorption gas volume of the full-diameter core of the shale gas core well at the mud circulation temperature is 30s-60 s.
The research aims at a 38m high-quality storage layer section at the lower part of a Wufeng-Longmaxi group. The rock mass area JY41-A well 14 full-diameter cores, the rock mass area JY190-B well 18 full-diameter cores and the Chuantong fold zone YZ-C well 21 full-diameter cores are respectively arranged in the coke dam main body area JY41-A well, the coke dam peripheral flat bridge area JY190-B well 18 full-diameter cores.
The on-site desorption instrument adopting an automatic water drainage and gas collection method developed by a stannless petroleum geological research institute can complete the test of 6 samples in a single batch at the same time; high-density data acquisition, wherein the shortest interval of data is 30 s; the relative error is less than 0.5 percent, and the absolute error is less than 0.25 mL.
By utilizing the on-site desorption instrument, the data acquisition time interval is 30s, and the desorption gas quantity data of the full-diameter rock core is fully automatically recorded until the single-period (30s) desorption quantity is 0.
Recording the density of the slurry: JY41-A well 1.33g/cm3JY190-B well 1.42g/cm3YZ-C well 1.26g/cm3The development effect evaluation coefficient was calculated based on the unified diffusion equation and the slurry density, and the calculation results are shown in tables 1 to 4.
TABLE 1 JY41-A well development effect evaluation coefficient
| Depth of well | Slope of diffusion equation | Density of slurry (g/cm)3) | Coefficient of development effect |
| 2579.19 | 0.36 | 1.33 | 0.27 |
| 2585.40 | 0.60 | 1.33 | 0.45 |
| 2587.17 | 0.67 | 1.33 | 0.51 |
| 2589.27 | 0.52 | 1.33 | 0.39 |
| 2591.12 | 0.39 | 1.33 | 0.29 |
| 2593.02 | 0.35 | 1.33 | 0.26 |
| 2595.12 | 0.42 | 1.33 | 0.32 |
| 2597.30 | 0.50 | 1.33 | 0.37 |
| 2603.30 | 0.61 | 1.33 | 0.46 |
| 2606.20 | 0.66 | 1.33 | 0.50 |
| 2609.18 | 0.73 | 1.33 | 0.55 |
| 2612.20 | 0.63 | 1.33 | 0.47 |
| 2615.29 | 0.75 | 1.33 | 0.56 |
| 2618.16 | 0.81 | 1.33 | 0.61 |
| Lower 38m average | 0.57 | 1.33 | 0.43 |
TABLE 2 JY190-B well development effect evaluation coefficient
| Depth of well | Slope of fit | Density of slurry (g/cm)3) | Coefficient of evaluation of development Effect |
| 4005.88 | 0.19 | 1.42 | 0.13 |
| 4008.26 | 0.13 | 1.42 | 0.10 |
| 4010.89 | 0.25 | 1.42 | 0.18 |
| 4013.49 | 0.21 | 1.42 | 0.15 |
| 4015.56 | 0.37 | 1.42 | 0.26 |
| 4017.14 | 0.38 | 1.42 | 0.27 |
| 4019.74 | 0.42 | 1.42 | 0.30 |
| 4022.67 | 0.37 | 1.42 | 0.26 |
| 4024.96 | 0.52 | 1.42 | 0.37 |
| 4027.14 | 0.56 | 1.42 | 0.39 |
| 4029.05 | 0.44 | 1.42 | 0.31 |
| 4031.94 | 0.32 | 1.42 | 0.22 |
| 4034.04 | 0.47 | 1.42 | 0.33 |
| 4035.69 | 0.62 | 1.42 | 0.44 |
| 4037.68 | 0.68 | 1.42 | 0.48 |
| 4040.09 | 0.96 | 1.42 | 0.68 |
| 4041.37 | 0.49 | 1.42 | 0.34 |
| 4042.32 | 0.47 | 1.42 | 0.33 |
| Lower 38m average | 0.44 | 1.42 | 0.31 |
TABLE 3 YZ-C well development Effect evaluation coefficient
| Depth of well | Slope of fit | Density of slurry (g/cm)3) | Coefficient of development effect |
| 4459.72 | 0.02 | 1.26 | 0.01 |
| 4465.12 | 0.02 | 1.26 | 0.01 |
| 4466.41 | 0.03 | 1.26 | 0.02 |
| 4469.01 | 0.02 | 1.26 | 0.02 |
| 4470.32 | 0.02 | 1.26 | 0.02 |
| 4474.23 | 0.02 | 1.26 | 0.01 |
| 4478.48 | 0.02 | 1.26 | 0.02 |
| 4481.37 | 0.02 | 1.26 | 0.02 |
| 4483.82 | 0.02 | 1.26 | 0.02 |
| 4488.61 | 0.02 | 1.26 | 0.02 |
| 4491.90 | 0.02 | 1.26 | 0.02 |
| 4495.07 | 0.02 | 1.26 | 0.01 |
| 4497.41 | 0.03 | 1.26 | 0.02 |
| 4499.51 | 0.03 | 1.26 | 0.02 |
| 4502.28 | 0.03 | 1.26 | 0.02 |
| 4506.25 | 0.03 | 1.26 | 0.03 |
| 4508.50 | 0.03 | 1.26 | 0.02 |
| 4511.71 | 0.03 | 1.26 | 0.03 |
| 4514.46 | 0.03 | 1.26 | 0.03 |
| 4515.80 | 0.02 | 1.26 | 0.02 |
| 4517.36 | 0.02 | 1.26 | 0.02 |
| Lower 38m average | 0.02 | 1.26 | 0.02 |
TABLE 4 evaluation coefficients of shale gas well development effects in different areas
As can be seen from the actual development data in the table 4, the development effect predicted by the model is very consistent with the actual production, the evaluation coefficient of the development effect of the JY41-A well in the main area of the coke dam with the highest unobstructed flow is also highest, the evaluation coefficient of the development effect of the JY190-B well in the peripheral area of the coke dam is medium, the test productivity is also medium, the YZ-C well in the Skangdong fold zone hardly contains gas, and the evaluation coefficient of the development effect is only 0.02.
Example two
Fig. 3 shows a block diagram of a shale gas well development effect prediction apparatus according to an embodiment of the present invention.
As shown in fig. 3, the shale gas well development effect prediction apparatus includes:
the mud density detection equipment 102 is used for obtaining the mud density of the shale gas core well during full-diameter core coring;
the field desorption instrument 104 is used for collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature;
a processor 106, the processor being connected to the in situ desorber, the processor performing the steps of: establishing a diffusion model of desorption gas quantity and desorption time to obtain a unified diffusion equation; calculating the seepage rate of free gas along a shale bedding seam Darcy in the full-diameter core coring process of the shale gas coring well based on a unified diffusion equation; based on the mud density and the rate of darcy seepage, a development effect evaluation coefficient is calculated.
Wherein, the unified diffusion equation is:
wherein Q istIs the desorption gas quantity, Q, of the shale at the time t∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
The tangential slope of the diffusion equation at the initial point of desorption time is the unified diffusion equation for the free gas seepage rate along the shale bedding crack Darcy in the full-diameter core coring process of the shale gas coring well.
Wherein, the following formula is adopted to calculate the evaluation coefficient of the development effect:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the speed of Darcy seepage, namely the tangent slope of a unified diffusion equation at the starting point of desorption time, and d is the slurry density.
Wherein the sampling time interval of the desorption gas volume of the full-diameter core of the shale gas core well at the mud circulation temperature is 30s-60 s.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. The method for predicting the development effect of the shale gas well is characterized by comprising the following steps:
obtaining the mud density and mud circulation temperature of the shale gas core well during full-diameter core coring;
collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature;
establishing a diffusion model of the desorption gas quantity and the desorption time to obtain a unified diffusion equation;
calculating the rate of free gas along shale bedding seam Darcy seepage in the full-diameter core coring process of the shale gas coring well based on the unified diffusion equation;
calculating a development effectiveness evaluation coefficient based on the mud density and the Darcy seepage rate.
2. The method of predicting the effectiveness of shale gas well development as set forth in claim 1 wherein the unified diffusion equation is:
wherein Q istIs the desorption gas quantity, Q, of the shale at the time t∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
3. The method for predicting the development effect of shale gas wells as claimed in claim 2, wherein the rate of free gas seepage along shale bedding seam darcy during full-diameter core coring of the shale gas coring well is the tangent slope of the unified diffusion equation at the beginning point of desorption time.
4. The method for predicting the development effect of shale gas wells as claimed in claim 3, wherein the development effect evaluation coefficient is calculated using the following formula:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the speed of Darcy seepage, namely the tangent slope of a unified diffusion equation at the starting point of desorption time, and d is the slurry density.
5. The method for predicting the effectiveness of shale gas well development according to claim 1, wherein the sampling time interval of the desorption gas volume of the full-diameter core of the shale gas core at the mud circulation temperature is 30s to 60 s.
6. A prediction device of shale gas well development effect, characterized by includes:
the mud density detection equipment is used for obtaining the mud density of the shale gas coring well during full-diameter core coring;
the field desorption instrument is used for collecting the desorption gas volume of the full-diameter core of the shale gas coring well at the mud circulation temperature;
a processor coupled to the in situ desorber, the processor performing the steps of:
establishing a diffusion model of the desorption gas quantity and the desorption time to obtain a unified diffusion equation;
calculating the rate of free gas along shale bedding seam Darcy seepage in the full-diameter core coring process of the shale gas coring well based on the unified diffusion equation;
calculating a development effectiveness evaluation coefficient based on the mud density and the Darcy seepage rate.
7. The shale gas well development effect prediction device as claimed in claim 6 wherein the unified diffusion equation is:
wherein Q istThe desorption gas volume of the shale at the time t, t is the desorption time, Q∞The total amount of the shale desorption gas at t → ∞, n is the desorption times, D is the diffusion coefficient of the shale gas, rpFull diameter core radius.
8. The shale gas well development effect prediction device as claimed in claim 7 wherein the rate of free gas seepage along shale bedding seam darcy during full diameter core coring of the shale gas coring well is the tangent slope of the unified diffusion equation at the start point of desorption time.
9. The shale gas well development effect prediction device as claimed in claim 8 wherein the development effect evaluation coefficient is calculated using the following formula:
α＝K/d
wherein, a is a development effect evaluation coefficient, K is the tangent slope of the unified diffusion equation at the initial point of desorption time, and d is the slurry density.
10. The shale gas well development effect prediction device as claimed in claim 6 wherein the sampling time interval of the desorption gas volume of the full diameter core of the shale gas core well at the mud circulation temperature is 30s to 60 s.
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