Study and Application of Fluid Inclusion in Petroleum Exploration in Weizhou Formation in Weixinan Depression of Beibuwan Basin

Weixinan depression is a complex faulted depression with rich hydrocarbon, and a series of fault-zones have been developed in this depression. Weizhou formation is mainly small faulted oil reservoirs, and the structure is very complex. Therefore, it is very difficult to confirm petroleum entrapment. In Well WZ11-7N-3, no oil and gas shows were found in Weizhou formation. In sidewell WZ11-7N-3Sa, 68 m oil spots and 62.1 m oil layer were found. It has been confirmed through analysis on fluid inclusion of cuttings from well WZ11-7N-3 that in sand sets corresponding to the oil layers in WZ11-7N-3Sa, the content of hydrocarbon fluid inclusion is much higher than that in oil layers, over 30%. In sand sets corresponding to the water layers in WZ11-7N-3Sa, water layers and salty fluid inclusion is much higher in water layers than oil layers, over 80%. It has been proved through exploration practice that oil reservoirs formed at the structural high place. Reexamining old wells by analyzing fluid inclusion can ascertain analogous faulted traps and find if hydrocarbon accumulation at the structural high place. In addition, the reserves can be increased, and the success rate of exploration can be improved. The study results can be used to guide exploration evaluation, and the study thinking is worth promoting.