Sedimentary-diagenetic characteristics and heterogeneity models of sandstone reservoirs: An example of Silurian Kalpintage Formation, Northwestern Tarim Basin, China

Abstract

Tarim Basin contains long and continuous records of marine and terrestrial paleogeographic evolution in the northern hemisphere. The Silurian Kalpintage Formation provides a window through which siliciclastic coasts can be reconstructed and examined. Seventeen measured sections of superbly-exposed Sishichang area in northwest Tarim Basin, are studied to interpret depositional system, establish sequence stratigraphic framework, reconstruct paleogeographic evolution, and discuss heterogeneity of variable systems. Ten sedimentary facies have been identified within the stratigraphic framework, comprising shoreface-, shelf-, tidal bar-, and tidal complex-dominated depositional systems. Different depositional systems show considerable variability in sedimentary and diagenetic features. Shoreface- and tidal bar-dominated sandstones tend to have high ductile lithic content, which induces severe mechanical compaction and formation of pseudomatrix. Tidal complex-dominated sandstones tend to have high quartz content, contributing to intensive quartz overgrowth. Sedimentary facies determine the fundamental differences of sandstone reservoirs in composition, sedimentary texture and structure, and diagenesis intensifies the differences of sandstone reservoirs in their quality and heterogeneity. The results provide understandings for the development, evolution, and heterogeneity of depositional systems at northwestern Tarim Basin, and serve as a foundation for future hydrocarbon exploration of Silurian Kalpintage Formation and other coastal marine reservoirs in the world.