The Geological Characteristics Of Heidimiao Reservoir In The West Slope Region Of Punan Oifield And The Relationship With Hydrocarbon Accumulation

Heidimiao Reservoir belongs to the upper petroleum combination of Songliao Basin, which lies on Nen-3 member and Nen-4 member. The west slope region of Daqing Placanticline is most favorable zone for exploration and development of in the present situation of research. According to study the structure and sedimentary characteristics of Heidimiao Reservoir in the block Pu-55 which located in the west slope of Punan Oilfield, find out the control action for Heidimiao Reservoir. This research is not only helpful to petroleum exploration and development in the zone of interest, but also have a profound significance for exploration and development in South of Daqing Placanticline.Through summarizing the previous research and utilizing the data of geology, 3D seismic, drilling, logging, cores et al, this paper takes the theory of structural geology, sedimentology, petroleum geology and other multi-disciplinary theory to analysis the structure characteristics and evolutionary history of block Pu-55 first, and study the control action to petroleum migration and accumulation. Secondly, on the basis of strata division and correlation, sand body division, study the microfacies and sand body distribution characteristics of every sublayer by the data of logging, seismic and geology. We can use the characteristics to analysis the connectivity of sand body, and further evaluate the reservoir property of Heidimiao Reservoir in the West Slope Region of Punan Oilfield. Finally, study the rule of hydrocarbon accumulation.Through analysis above, some new achievements have been acquired.(1) The main structure of block Pu-55 is a nose structure which located in the west wing of Putaohua structure and trend to Gulong sag. The characteristics becomes more and more distinct from deep to shallow strata, which suggest Puxi nose structure was the product of reverse deformation in the end of Mingshui period. The structure whose styles are fault-block and fault-nose is not obvious in the shallow of study region, associated with the faulting.(2) The fault can be divided into inherited fault and non-inherited fault by the vertical activity, and further classify the fault as seven types by the activity period: formed in the end of Qingshankou period, formed in the end of Yaojia period, formed in the end of Qingshankou period and active again in the end of Yaojia period, formed in the end of Nenjiang period, formed in the end of Qingshankou period and active again in the end of Nenjiang period, formed in the end of Mingshui period, formed in the end of Qingshankou period and active again in the end of Mingshui period.(3) It has an immense influence on structure feature that structure reverse occurred in the end of Mingshui period. A few uplifts and sags alternative distribution was placed in Punan region before the reverse period, and study region was always located in a culmination, pointing to the dominant region of hydrocarbon accumulation. The present structure map shows that the main structure of block Pu-55 is a nose structure which located in the west wing of Putaohua structure and trend to Gulong sag after the reverse period.(4) Heidimiao Reservoir in Pu-55 block deposited in delta front subfacies and pre-delta, whose lithology has reverse grain size with sand and mudstone interbed under the lake basin shrinking circumstance. Overall, study region located in deep lacustrine environment when HII2, HII3, HII4 deposited, and the microfacies is a great sheet of deep lacustrine mudstone. While the HII1 deposited, the environment transfer from deep to semi-deep lacustrine facies, even shallow lacustrine facies. A large area of sand sheet had been deposited at the same time. During HI6-HI5 had been deposited, the lake retreat steady. Meanwhile extensive underwater distributary channel had developed in study region, and formed a large area of mouth bar microfacies. The shallow water delta model can be explained the sedimental characteristics of heidimiao Reservoir in study region by sedimentary environmental analysis.(5) The main distribution range of single sand body thickness in study region is 1 to 3 meters, about 64 percent. Less than 5 meters ones accounted for 81%, which can be accounted for that the distributary channels in study region were well-developed, and migrated frequently. The distribution of every sublayer sand body is well, the sand body whose thickness is over 10 meters is widely distribution. The section shows that HI4-HI1 are the favorable reservoirs of conventional reservoir, and HI5-HII1 are the beneficial bed of lithological hydrocarbon reservoir.(6) The achievements of analysis of hydrocarbon accumulation condition shows: The activities of fault had been an passage of petrol migration and accumulation. The framework of structure in ancient and modern had controlled the formation and the transformation of reservoir. The lacustrine cycle had formed the mud and sandstone interbedded, and mudstone was blocked the sandstone off. The characteristics of sand body distribution had controlled the formation of conventional reservoir and subtle reservoir.