| Structural traps are mainly targeted for exploration in Langgu sag.Large scale reserves are more difficult to be found with increasing high degree of exploration.By the fourth resource evaluation,the remaining oil and gas reserves amount to 1.72×108t and 954×108gm3 respectively,which indicate large potential for exploration.Thus for next exploration,it is necessary to conduct further study of oil/gas accumulation laws in structures,establish reasonable accumulation pattern and rank favorable plays.Using previous study data and joint seismic data of the whole sag and referring to petroleum geology,sequence stratigraphy and sedimentology,new and overall understandings were achieved in terms of the structural features,source rock system,reservoir and reservoir-cap combination features,further confirming the basic geological features of the sag.We have verified such oil/gas accumulation law by analysis of typical oil/gas reservoirs and detailed delineation of favorable structural traps:oil/gas accumulation is controlled by source rock distribution,faulting structural features and coupling of sand body and faults and unconformities.In addition,we have identified several oil accumulation patterns including“adjacent generation and lateral storage-remote source hydrocarbon supply-trap controlling"model,“lower generation and upper storage-mixed source hydrocarbon-faulting controlling"model in Da Liuquan fault nose structural belt and platform horst of reverse fault block-central horst belt with two-way source hydrocarbon supply" model in He Xiwu structural belt.Based on this,Da Liuquan and He Xiwu structural belts were selected as favorable plays for next exploration. |
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