Study And Discussion On The Dominant Factors Determining The Abundant Oil And Gas Accumulation Within The Buried Hills In Damintun Depression

Guided by the new theories and methods in the structural geology, reservoir geology, petroleum geology, metamorphic rock buried hill reservoir forming theory, along with the techniques of the identification of the top of the buried hills, as well as structure type identification, logging based identification of buried hill lithology and net pay evaluation, etc., the paper systematically summarized the geologic conditions of the reservoir formation and the distribution of the oil and gas, fortified the research on the buried hill reservoir forming theory and the net pay evaluation technology, created the new idea on the controlling factors of buried hill reservoir formation, and enriched the theory of buried hill reservoir formation. In the paper, we mainly focused on study on the relationship of the buried hill oil and gas accumulation with the structural evolution, hydrocarbon source rock, varied reservoirs and fracture development conditions, multi-set cap rock sealing systems and regional supply window in the rifting stage,Based on the study, it is believed that the abundant accumulation in buried hill of Daminitun sag is mainly controlled by the structural development in the rifting stage, sedimentary features and the variety of the basement lithology, which is manifested in the following five aspects: a. the structure development in the rifting stage dominates the overall buried hill distribution and scale. b. the ample oil source condition is the solid foundation for the buried hill reservoir forming, especially the two sets of independent faulting systems make the hydrocarbon accumulation much abundant. c. the large scale and versatile reservoirs provide excellent hydrocarbon storage spaces. d. the two sets of regional cap rocks is the main origin of developing the high pour point oil systems, especially, in ES4 (the forth member of Shahejia formation), the cap rocks is not only thick, but also is widely distributed, featuring excellent high pressure sealing capacity, prohibited the upward migration of hydrocarbon, rendering the buried hill of the Damintun Sag self-contained. e. the existence of the regional oil supply window is the important reason for reservoir forming in the low area between the buried hills, and it is also the cause for large scale buried hill reservoir forming.Based on the above, the new insight for the Damintun buried hill reservoirs has been obtained, i.e., overall oil bearing in the sag with locally distributed abundance, and the new breakthrough was achieved for oil and gas reservoir distribution regulation and its controlling factors, which is of great significance in re-evaluation of Damintun Sag exploration potential and guiding the selection of the exploration target in the future...