Combined measurement method for organic matter-rich compact rock core gas permeability and diffusion coefficient

Abstract

The invention discloses a combined measurement method for organic matter-rich compact rock core gas permeability and diffusion coefficient. The method utilizes a gas pressure attenuation device to accomplish. The device is composed of a rock core holder, a gas storage chamber, a vacuum pump, a confining pressure pump, and a computer. The rock core holder is connected to the vacuum pump and the confining pressure pump respectively, the inlet end of the rock core is connected to the gas storage chamber and a gas source, the outlet end of the rock core is in a closed state, and the device is located in a water-bath heating system. By monitoring the process of the gas in the gas storage chamber flowing to the rock core till balance, a gas pressure attenuation curve can be obtained, then according to a real gas state equation, material balance and the occurrence and flow mechanism of gas in rock, the attenuation curve is divided into a seepage stage and a diffusion stage, thus acquiring the gas permeability and diffusion coefficient. The method provided by the invention simplifies the testing procedure, improves the experimental analysis efficiency, and can provide data support for experimental evaluation of gas mass-transfer ability in shale, coal rock and other unconventional reservoir rocks, gas well productivity prediction and the like.

Description

technical field [0001] The invention relates to an experimental method for simulating the multi-scale mass transfer process of gas in organic-rich tight reservoir rocks (shale, coal rock) in the experimental test of gas mass transfer capacity of tight oil and gas reservoirs, and performing joint measurement of rock permeability and diffusion coefficient. Background technique [0002] In order to meet the increasing energy demand of the world economy, the field of oil and gas exploration and development is gradually moving towards tight oil and gas resources. In recent years, major breakthroughs have been made in the commercial development of shale gas and coalbed methane. Compared with conventional natural gas reservoirs, shale gas and coalbed methane reservoirs contain a large amount of adsorbed gas, and the lithology is tight and nano-scale pores are developed. The gas output often undergoes a multi-scale mass transfer of desorption, diffusion and seepage. process. Among...

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Problems solved by technology

However, there is no uniform test method for diffusion coefficient at present. The common test method for diffusion coefficient uses powdery samples, which is difficult to simulate in-situ stress conditions.

Moreover, the existing gas diffusion coefficient and permeability tests in rocks usually use independent methods and instruments, which are inconsistent with the actual gas flow process under formation conditions, which is not conducive to establishing the relationship between the two, and also consumes a lot of time. time and material costs

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