Poor understanding of the main factors controlling hydrocarbon accumulation is the major constraint of petroleum exploration in Yubei area of Tarim Basin at present.The characteristics of hydrocarbon accumulation in Yubei 1 fault belt were studied.Oil reservoirs in the Ordovician Yingshan Formation in Yubei-1 wellblock are of karst-fractured vuggy type controlled by unconformity and related with paleo-karst of carbonate rocks.The reservoir spaces of the Yingshan Formation carbonates consist of pores

vugs and fractures

and the reservoirs can be divided into 3 types

namely fractured-vuggy type

fractured type and vuggy type

of which the fractured-vuggy type is the most significant in this area.The reservoir distribution is mainly controlled by the karst of carbonate rocks.The reservoirs are characterized by strong heterogeneity

vertical superimposition and lateral connection in large area

as well as uneven oil-bearing property.The Yingshan Formation reservoirs experienced multiple phases of hydrocarbon accumulation

of which the Late Hercynian was the major one.Hydrocarbon accumulation in the study area was jointly controlled by oil sources

reservoir

carrier system and cap rock.The oil sources were the foundation of hydrocarbon accumulation.The three-dimensional carrier network consisting of faults and unconformities provided high quality pathway for hydrocarbon migration.The reservoir distribution controlled the formation of the pools and their scales.Mudstone intervals in the Lower and Middle Bachu Formation provided regional seals for the preservation of oil and gas.Based on the analysis of reservoir characteristics and controlling factors of hydrocarbon accumulation

we established a hydrocarbon accumulation pattern for the Yingshan Formation reservoirs in Yubei area.