Sequence Stratigraphy Research And Stratigraphic/Lithologic Reservoirs Prediction On Lower Cretaceous In A'Nan-Abei Sag, Erlian Basin, China

Stratigraphic/lithologic reservoirs play a very important role in reserves and production increase in Chinese onshore exploration. Sequence stratigraphy is one of the key technologies in stratigraphic/lithologic reservoirs exploration.A'nan-Abei Sag, east of Manite Depression, Erlian Basin, Inner Mongolia Province, with most structure traps drilled, is focused on the exploration stage of stratigraphic/lithologic reservoirs prospecting now. Approaches that deal with chronostratigraphic framework, distribution of depositional system and stratigraphic/lithologic traps are strongly needed, with the comprehensive analysis of the seismic ,well logging, well drilling, outcrop and areal geology data , a united chronostratigraphic framework on Lower Cretaceous is established according to sequence stratigraphy theory and sedimentology , and in this framework, sequence characteristic, prediction to stratigraphic/lithologic reservoirs are studied. Major results from the research present that:A united chronostratigraphic framework on Lower Cretaceous is established in A'nan and Abei Sag. It can be divided into four sequences from Aershan Formation to Tenggeer Formation. In this framework, the distribution of depositional system is more transparent, and a comprehensive sequence model is buildup.Three major factors to dominate sequence formation are claimed, including tectonic movement, source area and climate, and episodic tectonic movement is the most important independent one.Two volcanic facies (explosion and effusion facies), five sedimentary facies and fourteen sub-facies and twenty five micro-facies are identified. As to the five sedimentary facies, they are lacustrine facies, delta facies, fan-delta facies, nearshore subaqueous fan facies and turbidite facies.Menggulin conglomerate is derived from andesite of the volcanic platform in Menggulin Uplift, advising the traditional view of north source area. Sediments of the fourth member of Aershan Formation in Jingtewula area is claimed as shallow lacustrine delta front facies, not fluvial facies.Based on integrated analysis on hydrocarbon accumulation in different sequences and system tracts, it is proposed that the most oil-rich reservoir is concentrated around sequence boundary, usually in the sand bodies formed in upper part of highstand system tract, and in lower part of lowstand and transgressive system tract. The advantaged reservoirs are composed of subaqueous distributary's channel sand in middle fan sub-facies, and deep lacustrine turbidite sand.The forming models of stratigraphic/lithologic reservoirs are built, and the advantaged strata and plays are proposed for further exploration of stratigraphic/lithologic reservoir, besides, some special suggestion on work methods is briefly introduced.