Characteristics of oil-gas accumulation in northern sector of the West Slope, Songliao Basin
Sun Guoxin1,2, Feng Zhiqiang3, Sun Xiaodong2
1. Guangzhou Institute of Ceochemistry, Chinese Academy of Sciences, Guangzhou 510640;
2. Exploration and Development Research Institute of Daqing Oilfield Company Gtd., Daqing, Heilongjiang 163712;
3. Daqing Oilfteld Company Ltd., Daqing, Heilongjiang 163453
The oil and gas in northern sector of the West Slope, Songliao Basin, sourced from Qingshankou Formation in the Qijia-Gulong Sag, Central Depression, which laterally migrated west-wards along 3 narrow pathways, and accumulated by the low-amplitude structures, barrier of faults and stratigraphic pinch outs.In the West Slope, the oil and gas were not favored to enrich in large scale, since the structures' amplitude being usually lower, the scale of the faults being smaller and the stretching distance of the faults being short.The stratigraphic overlap belt along the basin margin might be a favorable area to find large-scale stratigraphic pinch out accumulations and oil sand mines.The atmospheric water eluviation was pervasive in the West Slope, where the crude oils were generally degradated by the aerobic bacteria and the degree of the densification became lower along the direction of the atmospheric water descending, namely, the seriously degradated heavy oil and oil sand developed in the stratigraphic overlap belt along the basin margin, moderately degradated heavy oil developed in the fault barriered oil accumulation belt,while the lightly degradated heavy oil and normal oil occurred in structural-lithologic oil accumulation belt.The oil sand mines in Tumuji and Well Lai D6 showed more prospects to the exploration in the West Slope.