Analysis of Braided River Deltaic Depositional System in the Eastern Sag of Liaohe Basin

摘要

According to the analysis of drilling cores, well logs, seismic and slice identification and analysis, the study region has in sequence developed alluvial fan, braided river, braided river delta, lacustrine facies, as well as the littoral and shallow beaches dam and semi-deep lake turbidite fan. The braided river delta often extends over tens to thousands of square kilometers, and glutenite in subaqueous distributary channel and hydracarbon source rocks frequently deposited with alternative, which constitutes a good source-reserve-seal association in the vertical direction with preferable oil and gas reservoir properties on account of its better rock sorting and the crossrange continuance and connectedness of glutenite. Braided river delta in this region is composed of braided river delta plain subfacies, braided river delta front subfacies and pre-braided river delta subfacies. The plain subfacies is composed of braided channel characterized by various colors, rough granules, poorly graded and erode and stuffed structure existing at the bottom as well as the flood plain formed by migration and flap of the braided channel. What's more, front subfacies chiefly developed all kinds of microfacies, such as distributary channel, mouth bar, distal bar, sand sheet and subaqueous inter-distributary channel.