Method for measuring shale adsorption gas quantity and free gas quantity

Abstract

The invention discloses a method for measuring adsorption gas quantity and free gas quantity of shale. The method comprises the following steps: 1), selecting a shale core sample, and measuring basicphysical property parameters; 2), carrying out a depletion development experiment, and drawing a relation curve of production time and total experiment gas yield; 3), setting an initial numerical value of a correction coefficient according to the corrected free gas amount calculation formula and the corrected Langmuir adsorption formula, and drawing a relation curve of the production time and thecalculated total gas production amount; 4), judging whether the relation curves obtained in the step (2) and the step (3) meet preset conditions or not, if not, adjusting the correction coefficient, repeating the step (3) until the preset conditions are met, and entering the step (5); and 5), drawing a relation curve between the calculated total gas production rate, the calculated free gas production rate and the production time, and calculating the adsorption gas amount and the production time to obtain the real-time adsorption gas amount, the real-time free gas amount and the real-time totalgas production rate. According to the invention, the amounts of adsorbed gas and free gas in the production time can be calculated in real time.

Description

technical field [0001] The invention relates to the technical field of shale gas exploration and development. More specifically, it relates to a method for measuring the amount of shale adsorbed gas and free gas. Background technique [0002] As an unconventional gas reservoir with great development potential, the occurrence mode of shale gas is different from that of conventional gas reservoirs. Shale gas is mainly in free and adsorbed states, and free gas mainly occurs in fractures and matrix pores of shale reservoirs. Or in organic nanopores, the adsorbed gas mainly exists in kerogen, clay particles and pore surfaces. The ratio of adsorbed gas in different shale gas fields at home and abroad is generally between 20% and 80%. Adsorbed gas is of great significance to the output and efficient development of shale gas. Due to the extremely low porosity and permeability of shale reservoirs and the complex occurrence and transport states, the mechanism of shale gas flow is ve...

AI Technical Summary

Problems solved by technology

At present, there is no suitable quantitative method to effectively distinguish the amount of free gas and adsorbed gas in the gas production at different production stages, and it cannot reasonably explain the large difference in single-well production of shale wells and the unclear decline law, which restricts shale production to a certain extent. Efficient development of gas

[0004] Therefore, aiming at the current situation that it is impossible to distinguish between adsorbed gas and free gas in shale reservoir gas production, the present invention provides a method for measuring shale adsorbed gas and free gas, which provides a basis for production system optimization and development plan formulation

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