Abstract:

Targeting on the Middle-Triassic Lower Karamay Formation in Hong 29 district of  3D seismic exploration of the Hongshanzui oil field in the Junggar basin, combining with the drilling data and logging date, it can identified a long scale cycle and 3 middle scale cycles (MSC1, MSC2, MSC3) by high resolution sequence stratigraphy. During the course of long scale cycle, the river channel bending index apparently presented characteristics as low-high-low, meanwhile the continuity of channel sand also displayed an evaluation as good-bad-good. By analyzing the characteristics of reservoirs and hydrocarbon of Lower Karamay Formation, it found that the oil and gas were mainly assembled in the MSC2 , while the river channel bending index during this cycle was relatively high, and the channel sand bodies had a bad continuity. Connecting with the rule of the lithologic reservoir accumulation, it put forward an exploration method that “finding the poor sand in the rich sand”, which presented that the “poor” sand at the highest location of long baselevel was also the advantaged zone for exploration and fault-lithology composite trap was the favorable  explorationary target.

Key words: fluvial facies, middle scale cycle, hydrocarbon accumulation, the Junggar basin, Middle-Triassic, sandstone