Reservoir Characteristics of Reef-Shoal Facies, Changxing Formation, Yuanba Gasfield, Sichuan Basin

Abstract

Based on the successful practice of Puguang gas field, in 2006, Well Yuanba 1 was drilled in northeastern Sichuan by SINOPEC, obtaining the gas flow of 503,000 m3 per day in reef-shoal reservoirs in Changxing Formation. This announced the discovery of Yuanba Gasfield. Yuanba Fasfield is a lithologic gas pool with characteristics of: high H2S content while normal pressure, weak tectonic deformation, deep burial, etc. Yuanba Gasfield is the deepest marine gas fields in Sichuan Basin, the middle of the gas pool reaches the average burial depth of 6,600 m. Reservoirs mainly developed in the Changxing reef-shoal facies with the large scale and good reservoir quality. The reservoir formation was controlled mainly by early meteoric dissolution and dolomitization, while deep dissolution and tectonics contributes a little.