Abstract:

The Central Canyon gas field， with reserves exceeding 100 billion cubic meters， has been discovered on the southern slope of the Lingshui Sag in the Qiongdongnan Basin， confirming the hydrocarbon-rich nature of this sag. Despite local breakthroughs， lithological reservoir exploration in block LS13-2 on the northern slope of the Lingshui Sag has yielded merely gas shows rather than substantial reserves， indicating unsatisfactory exploration outcomes. This study aims to determine the hydrocarbon accumulation patterns and play fairways in the block. By analyzing petroliferous basins and critical factors controlling hydrocarbon accumulation， we propose a novel philosophy of hydrocarbon exploration and identify paly fairways for hydrocarbon accumulation. The results indicate that block LS13-2 exhibits generally favorable conditions for hydrocarbon accumulation， which lay the foundations for the formation of large- to medium-sized oil and gas fields characterized by sufficient hydrocarbon sources， large-scale reservoirs， efficient carrier systems， and generally excellent preservation conditions. Nevertheless， the exploration of the Miocene lithologic traps faces challenges due to unfavorable factors such as the main hydrocarbon expulsion stage of source rocks occurring earlier than trap formation and the low vertical hydrocarbon transport capability of faults. Accordingly， we develop a three-dimension exploration assessment methodology consisting of early hydrocarbon accumulation， lithologic traps， and fault-sand body conduit system. The assessment results indicate that the submarine fan zone of the western ramp features favorable hydrocarbon accumulation conditions encompassing primary hydrocarbon reservoirs， large-scale lithologic traps， and efficient fault-sand body carrier systems， establishing this zone as an optimal play fairway.

Key words: enrichment pattern, accumulation condition, play fairway, Meishan Formation, Lingshui Sag, Qiongdongnan Basin