Detection algorithm for pore structure of shale gas reservoir

Abstract

The invention discloses a detection algorithm for the pore structure of a shale gas reservoir. The detection algorithm comprises the step of carrying out specific surface analysis and detection to obtain partial data by adopting a nitrogen absorption method, and also comprises the following steps: (1) in the pressure reducing process after nitrogen is absorbed to maximum pressure, gradually and respectively converting staged desorbing amount of the nitrogen into the percent of the volume of a desorbed wetting phase at stages accounting for the volume of a rock-core pore and the percent of the volume of the desorbed nitrogen accounting for the total volume of the rock core; (2) calculating out the thickness of a wetting film in the process of staged desorption, namely, the throat radius of the process, by adopting a digital model for calculating the thickness of a water film according to the specific surface of nitrogen absorption and the density of the rock core; and (3) according to the relation of the capillary pressure theory, obtaining capillary pressure under the corresponding and relative pressure and a capillary pressure curve in the whole desorption process. The detection algorithm disclosed by the invention has the advantages that the characteristics of the pore structure of the shale gas reservoir and the characteristics of seepage and production of natural gas can be intuitively described, further the value of the shale gas reservoir is evaluated, the practical value is very high and the application prospect is very wide.

Description

Technical field [0001] The invention relates to the study of the pore structure of shale gas reservoirs and the classification and evaluation technology of shale gas reservoirs, in particular to a detection algorithm for the pore structure of shale gas reservoirs. Background technique [0002] As we all know, the value evaluation of shale gas reservoirs has a very important impact on natural gas exploration and development. It determines the accuracy of natural gas exploration, the investment plan for natural gas development, and the utilization value of natural gas fields. In the natural gas field, shale gas reservoirs are mainly composed of mudstone and shale. At present, there are two methods for evaluating the value of shale gas reservoirs: (1) Nitrogen adsorption ratio surface analysis and detection are used to obtain adsorption desorption under corresponding pressures. The amount of attached nitrogen, adsorption and desorption curve, BET and BJH specific surface, pore-pore ...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a detection algorithm for the pore structure of shale gas reservoirs, which solves the problems in the prior art that the size and distribution of core throats in shale gas reservoirs and the connection relationship between pore throats cannot be effectively measured. Provide accurate and effective basis for the value evaluation of shale gas reservoirs

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