Gas effective porosity inversion method for shale gas reservoir
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A technology for effective porosity and shale gas reservoirs, which is applied in the development of unconventional oil and gas reservoirs in the petroleum industry, and can solve problems such as errors
Active Publication Date: 2017-07-07
CHINA UNIV OF PETROLEUM (BEIJING)
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The stable, safe and easily available nitrogen gas (N 2 ) or helium (He), while in the process of shale gas depletion and CO 2 During the displacement process, the actual flowing fluid is CH 4 and CO 2 , due to N 2 and He with CH 4 , CO 2 There are large differences in the adsorption properties and high-pressure physical properties of shale surfaces, which lead to the direct application of the porosity values measured in experiments to measure CH 4 , CO 2 A larger error occurs in the effective porosity process
Based on the above reasons, the commonly used porosity gas measurement methods cannot accurately reflect the CH in actual shale gas reservoirs. 4 , CO 2 effective porosity value, so it is necessary to use indoor N 2 or the experimental data measured by He to obtain the CH under actual gas reservoir conditions 4 , CO 2 The effective porosity value of the shale gas reservoir, so this application proposes a shale gas reservoir effective porosity inversion method
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Embodiment 1
[0160] This example provides a method for inversion of gas effective porosity in shale gas reservoirs, the flow chart of which is shown in figure 2 shown, from figure 2 It can be seen that the inversion method includes the following steps:
[0161] Aiming at the problem of inaccurate determination of porosity with helium (He), this example uses the inversion formula of the present invention to calculate the porosity measured by helium gas measurement method, CH 4 Effective porosity and CO under monolayer adsorption 2 The effective porosity under multi-layer adsorption, and the calculation results of the present invention are compared with the laboratory experiment results.
[0162] Among them, the calculation process includes the following steps:
[0163] 1) Determination of shale absolute porosity φ by helium gas detection method ab，He , wherein, the specific operation steps of helium gas detection method are known in the art;
[0164] In this example, the measured φ ...
Embodiment 2
[0185] This example provides a method for inversion of gas effective porosity in shale gas reservoirs, the flow chart of which is shown in figure 2 shown, from figure 2 It can be seen that the inversion method includes the following steps:
[0186] Shale porosity, CH 4 Effective porosity and CO under monolayer adsorption 2 For the effective porosity under multi-layer adsorption, the inversion formula of the present invention is used to calculate the porosity in three cases, and the experimental results are compared with the calculated results.
[0187] Among them, the calculation process includes the following steps:
[0188] 1) Measure the effective porosity φ of shale by nitrogen gas measurement method a，N2 , wherein, the specific operation steps of nitrogen gas measuring method are well known in the art;
[0189] In this example, the measured φ a，N2 =0.06;
[0190] 2), using the balance method to measure the density data ρ of shale r , wherein, the specific operat...
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Abstract
The invention provides a gas effective porosity inversion method for a shale gas reservoir. The gas effective porosity inversion method comprises the following steps: (1) establishing a shale effective porosity inversion formula, which considers adsorbed gas and free gas, according to a mass conservation law; (2) determining absolute porosity of the shale gas reservoir by adopting helium gas, so as to obtain helium gas determined absolute porosity; carrying out inversion on the basis of the helium gas determined absolute porosity to obtain effective porosity on methane and carbon dioxide of a shale respectively; or determining the effective porosity on nitrogen gas of the shale gas reservoir by adopting the nitrogen gas to obtain nitrogen gas determined effective porosity; carrying out the inversion on the basis of the nitrogen gas determined effective porosity to obtain shale absolute porosity and carrying out the inversion on the shale absolute porosity to obtain the actual effective porosity on the methane and the carbon dioxide of shale respectively.
Description
technical field [0001] The invention relates to a method for inversion of effective porosity of gas in shale gas reservoirs, in particular to a method for inversion of effective porosity under the influence of actual formation fluid adsorption in shale gas reservoirs, and belongs to the development technology of unconventional oil and gas reservoirs in the petroleum industry field. Background technique [0002] Shale gas is mainly unconventional natural gas that occurs in dark mud shale in a free or adsorbed state. The pore characteristics of shale are the key factors that determine the gas-bearing properties of shale reservoirs. Shale porosity is an important parameter for evaluating the physical properties of shale reservoirs and calculating gas reserves. How to effectively analyze shale porosity is a technical problem that must be solved in shale gas exploration and development. [0003] At present, the methods for measuring shale porosity mainly include mercury intrusio...
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