--> Abstract: Seismic Anomalies of Karst Formations (Permian) and Relationship With Distribution of Gas Reservoirs in Southwest Sichuan Basin China, by Y. Y. Li and K. Zhao; #90987 (1993).

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LI, YUAN YUAN, and KAI ZHAO, University of South Carolina, Columbia, SC

ABSTRACT: Seismic Anomalies of Karst Formations (Permian) and Relationship With Distribution of Gas Reservoirs in Southwest Sichuan Basin China

The limestone of Yanxin Series (Lower Permian) is a significant gas reservoir in the Sichuan Basin. Generally, the gas pools in Yanxin Series are mostly controlled by fractures related to the local structures. However, results in the Jieshi-Hebao area, Southwestern Sichuan suggest that karst zones, developed in the mid-upper Maokou Formation, Yanxin Series, are related to the gas pools. The distribution of the karst zones may be one of the main factors deciding the distribution of gas pools in some regions.

This paper discusses the features of karsts in relation to the gas pools using geologic data (outcrops and well cores), seismic response of the karst zones by seismic models, and the regional distribution of karsts by general and specially processed seismic data. Also some criteria are suggested for prospecting the region possessing gas pools and potential areas for drilling exploration proposed.

They are: (1) the karst-unfilled face in upper Maocou Formation; (2) low-velocity anomal and weakening-instantaneous-amplitude-envelope zones, in particular, with underlying paleo-intrusions; (3) fault zones of Pre-Yanxin Series and high parts of the paleostructures relative to paleo-intrusions; (4) regions with thin remnant thicknesses of Maocou Formation.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.