Stress heterogeneity in the Changning shale-gas field, southern Sichuan Basin: Implications for a hydraulic fracturing strategy

Making sense of micro-fractures to the Longmaxi shale reservoir quality in the Jiaoshiba area, Sichuan Basin, China: Implications for the accumulation of shale gas

The dichotomy in noble gas signatures linked to tectonic deformation in Wufeng-Longmaxi Shale, Sichuan Basin

Shale gas exploration potential and reservoir conditions of the Longmaxi Formation in the Changning area, Sichuan Basin, SW China: Evidence from mud gas isotope logging

The presence and content of water will certainly affect the gas adsorption capacity of shale and the evaluation of shale gas content. In order to reasonably evaluate the gas adsorption capacity of shale under actual reservoir conditions, the effect of water on methane adsorption capacity needs to be investigated. Taking the Da’anzhai Member of the Lower Jurassic Ziliujing Formation in the northeastern Sichuan Basin, China as an example, this study attempts to reveal the effect of pre-adsorbed water on methane adsorption capacity in shale-gas systems by conducting methane adsorption experiments in two sequences, firstly at different temperatures under dry condition and secondly at different relative humidity levels under the same temperature. The results show that temperature and relative humidity (i.e., water saturation) are the main factors affecting the methane adsorption capacity of shale for a single sample. The key findings of this study include: (1) Methane adsorption capacity of shale first increases then decreases with depth, reaching a peak at about 1600-2400 m. (2) Lower relative humidity correlates to greater maximum methane adsorption capacity and greater depth to reach the maximum methane adsorption capacity. (3) 20% increase of relative humidity results in roughly 10% reduction of maximum methane adsorption capacity. As a conclusion, methane adsorption capacity of shale is predominately affected by water saturation, pore type and pore size of shale. This study could provide a theoretical basis for the establishment of a reasonable evaluation method for shale adsorbed gas content.

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Effect of Pre-Adsorbed Water on Methane Adsorption Capacity in Shale-Gas Systems

Variation in pore systems with tectonic stress in the overthrust Wufeng-Longmaxi shale of the southern Sichuan Basin, China

The invention discloses a marine shale high-quality reservoir prediction method based on source rock-reservoir-brittleness analysis. The marine shale high-quality reservoir prediction method comprisesthe steps that S1, basic data about source rock, a reservoir and brittleness of a shale interest interval in a research area are collected; S2, according to a grey correlation method, weight coefficients reflecting source rock properties, reservoir properties and brittleness characteristics are calculated respectively; S3, calculation formulas for reflecting the source rock quality, the reservoirquality and the brittleness quality are established respectively; S5, a quantitative formula for evaluating the marine shale high-quality reservoir is established; S6, the Q value of each well is calculated based on a formula 4 according to the data of each well in the research area; S7, according to the calculated Q value of each well, a Q value contour map on the plane of the research area is drawn; and S8, a large-value area is selected according to the Q value contour map to determine the large-value area as a development area of the marine shale high-quality reservoir. The cost of shalegas favorable area prediction can be effectively reduced, the precision of marine shale favorable reservoir prediction is improved, and the progress of shale gas exploration is directly promoted.

Tan Xiucheng

Papers

Variation in pore systems with tectonic stress in the overthrust Wufeng-Longmaxi shale of the southern Sichuan Basin, China

Marine shale high-quality reservoir prediction method based on source rock-reservoir-brittleness analysis