Controlling effect of Late Paleozoic tectonic and sedimentary differentiation on multi-type gas reservoirs in Permian, Sichuan Basin

Abstract

Based on the analysis of the Late Paleozoic global tectonic background and the tectonic environment of the Upper Yangtze area, the basin prototype and the Permian lithofacies paleogeography of the Sichuan Basin, combined with the understanding of the Permian gas reservoir characteristics and accumulation conditions, the controlling effect of the Late Paleozoic tectonic and sedimentary differentiation on the Permian multi-type gas reservoirs in the Sichuan Basin is discussed. Results showed that the tectonic differential uplift or subsidence under the extensional background formed the palaeogeomorphology of alternating uplift and depression, which led to the evolution of the sedimentary pattern from the Middle Permian to the Late Permian: platform alternating with platform and depression in the early stage, and platform alternating with rift trough (shelf) in the late stage. Multiple sets and types of source rocks formed in the platform sag, tidal plane-lagoon, slope, shelf-basin and other facies, sub-facies or micro-facies, and multiple sets and types of reservoirs controlled by beaches, platform edge sand and later diagenesis transformation constituted a variety of source-reservoir combinations such as lower generation and upper storage, side generation and side storage, self-generation and self-storage etc. These source-reservoir combinations constitute the basic conditions for hydrocarbon accumulations in Permian. Multiple sets and types of reservoirs are the fundamental reasons for the wide distribution of Permian gas-bearing strata and various gas reservoir types. The Permian strata has favorable conditions for comprehensive and three-dimensional exploration owing to multi-domain, multi-type and multi-layer.

Keywords

• source-reservoir combinations
• gas reservoir type
• tectonic and sedimentary differentiation
• late paleozoic
• permian
• sichuan basin