关键词: 水下分流河道, 高能河道砂体, 泥质含量, 孔隙度, 须家河组, 川东北

Abstract: The geological conditions for hydrocarbon accumulation in the continental strata of northeastern Sichuan Basin are
favorable, particularly within the fourth member of the Upper Triassic Xujiahe Formation, which exhibits significant potential for natural gas exploration. In the eastern Yuanba area, the fourth member is characterized by underwater distributary channel microfacies within the delta front sedimentary subfacies, forming extensive sandstone reservoirs. Based on large-scale hydrocarbon accumulation, the development of high-quality reservoirs is a critical factor for controlling natural gas enrichment. The variations in sedimentary microfacies directly influence the properties of sandstone and control the distribution of high-quality reservoirs. Among the underwater distributary channel sedimentary microfacies, the main channel microfacies exhibit stable and strongdynamic water flow, which forms high-energy channel sandstone that represents the most favorable reservoir. Consequently, identifying high-energy channel sandstone is crucial for locating high-quality tight sandstone gas reservoir. Based on sedimentological theory, this study conducted the detailed analysis of well logging facies and data, corroborated by core analysis results, to establish the quantitative classification criteria for high-energy channel sandstone based on porosity and shaliness. Two identification methods for high-energy channel sandstone are proposed: (1) the joint well log facies identification method, and (2) the shaliness and porosity intersection analysis method. The effectiveness and accuracy of these methods are further validated through core analysis results and geophysical prediction results. These methods are widely applicable to the identification of highquality channel sandstone reservoirs in the Xujiahe Formation in northeastern Sichuan, thereby supporting tight gas sandstone exploration.

Key words: underwater distributary channel, high-energy channel sandstone, shaliness, porosity, Xujiahe Formation;
Northeastern Sichuan Basin