Analytical method for gas storage capacity of matrix pores in tight bedrock

Abstract

The invention provides an analysis method of natural gas storage and collection capability of matrix pores in a dense bedrock. The analysis method comprises the following steps: measuring the gas porosity of a rock sample to be detected by using a helium method; calculating a total pore volume of the rock sample to be detected according to the volume and gas porosity of the rock sample to be detected; injecting a non-wet-phase liquid into the rock sample to be detected and gradually increasing injection pressure until the saturation degree of the non-wet-phase liquid is not increased along with the increasing of a pressure value, wherein the saturation degree is calculated by the total pore volume; carrying out data setting point drawing according to the pressure value and the corresponding saturation degree of the non-wet-phase liquid to obtain a capillary pressure curve of the rock sample to be detected; and reading a maximum value of the saturation degree of the non-wet-phase liquid on the capillary pressure curve and obtaining the percent of the volume of the matrix pores in the total pore volume of the rock sample to be detected according to the maximum value. With the adoption of the analysis method provided by the invention, the volume percent of the matrix pores in the whole block-shaped rock sample can be accurately calculated, so that the natural gas storage and collection capability of matrix pores is determined.

Description

technical field [0001] The invention relates to the field of reservoir evaluation in natural gas geological exploration technology, in particular to an analysis method for the ability to store natural gas in matrix pores in tight bedrock. Background technique [0002] Reservoir evaluation technology is one of the most important technologies in the field of petroleum geological exploration. The storage capacity of rocks in oil and gas layers directly determines the scale and productivity of oil and gas reservoirs. Among them, physical property evaluation and pore structure research are important in oil and gas reservoir evaluation. Content 1 (National Energy Administration, SY / T 6285-2011 Oil and Gas Reservoir Evaluation Method, p.1-15, 2011; Luo Zhitan and Wang Yuncheng, Pore Structure of Oil and Gas Reservoirs, Beijing, Science Press, 1986) . [0003] In recent years, explorers have discovered a large-scale natural gas reservoir in the tight bedrock in the Dongping area of...

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Problems solved by technology

[0004] The methods commonly used by geologists to determine the porosity of rocks include: Archimedes mercury immersion method, mercury displacement method, vernier caliper measurement method, Boyle's law double-chamber method, fluid saturation method, etc. (People's Republic of China General Administration of Quality Supervision, Inspection and Quarantine of the Republic of China, Standardization Management Committee of China, GB / T 29172-2012 Core Analysis Method, p.78-102, 2012), the porosity data measured by these methods or in combination or alone have the total pore volume However, it is impossible to distinguish the respective percentages of different pore types (such as matrix pores, dissolution pores, fractures, etc.), especially the determination of matrix pore volume is particularly important, and its content percentage directly determines whether natural gas can be sustained and stable or production decline Rate

For the identification of matrix pores in tight bedrock and the measurement of pore size, geologists usually use field emission scanning electron microscopy (State Bureau of Quality and Technical Supervision, GB / T 18295-2001 Oil and Gas Reservoir Sandstone Sample Scanning Electron Microscopy Analysis Method, p.1-8, 2001), the pore size of a single matrix pore is magnified by the scanning electron microscope and can be seen at a glance on the scale of the instrument system, but the scanning electron microscope method cannot calculate the volume of these matrix pores in the entire rock sample block Percentage, that is, the storage capacity of matrix pores is difficult to quantify

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