Progress in petroleum exploration in the Songpan-Aba area,northwestern Sichuan, China, and preliminary evaluation

The Songpan-Aba area located in the central part of the Songpan-Garze tectonic belt on the northeastern Qing- hai-Tibet Plateau is now a frontier area of petroleum exploration for Sinopec. Since 2002, based on systematic petroleum geological investigations, gravity survey, aeromagnetic and electromagnetic survey, seismic telemetric survey and remote sensing and geochemical prospecting, the relatively stable Zoige buried block, manifestations of several localized structures and geochemical anomaly zones have been found. The authors consider that there might exist favorable petroleum geological conditions in this area, i.e. Lower Paleozoic source rocks, Upper Paleozoic reservoir rocks and Triassic seals. The central rise in the Zoige depression and the slope zone where the rise passes northward to a subbasin are the favorable area for recent petroleum exploration, where the Hongcan-1 well was drilled. Various data of exploration indicate that this area should have petroleum prospects. However, it is difficult to carry out petroleum exploration because the Triassic is very thick and has undergone polyphase deformation. Therefore, more efforts should be devoted to follow-up analysis-while-drilling and intensive petrolelum geological research, and geophysical prospecting should be increased in the near future.