This paper studies the main factors influencing reserve growth

of the Mobei oil/gas reservoir. Many oil/gas layers were not identified during the early exploration period due to several reasons. The first is that no effective measures were applied to protect the oil/gas layers with low permeability and porosity and strong sensitivity. The second is that the low permeability and porosity and high clay content lowered the accuracy of log interpretation. After eliminating the impacts of lithology

physical properties and other factors on logging evaluation of oil/gas reservoirs

we established board charts to evaluate the reservoir properly. Based on this

we found 36 new oil/gas layers being neglected before in well 26. The Yanshan arc fault acts as the lateral seal for the interbeded sandstone and shale reservoirs in the 2

nd

member of the Lower Jurassic Sangonghe Formation. As the large-bin seismic data acquired before cannot meet the requirements of identification and fine description of small faults

the new high resolution 3D seismic data were used to delineate the sandbodies and arc fault through prestack depth migration

reservoir prediction and variable velocity mapping under an isochronous sequence framework. The coupling of favorable sedimentary microfacies with the arc fault in the directions of hydrocarbon migration and accumulation can result in the formation of favorable plays. Therefore

reserve growth can be realized through reperforming formation test in old wells and drilling new wells. The reserves of Mobei oil/gas reservoir grow by near 3 fold after this method was applied. It also can be used in similar oil/gas fields. 