Sequence Chatacterristics And Subtle Reservoir Prediction Of Putaohua Oil Bearing Layer In Qijia-Gulong Area

This research analyses the sequence stratigraphic framework, the sedimentary facies, the reservoir, the oil gas pool distribution rule, the controlling factors and the stratum - lithological trap of Putaohua oil bearing layer in Qiqia - Gulong area in northern Songliao basin, comprehensively based on the newest theory and the method of sequence stratigraphy, sedimentology, seismic stratigraphy and reservoir geology, and using the data from seism, logging, geological log and core.This research divides the Putaohua oil bearing layer into three fourth-order sequences (they are SQ1, SQ2, and SQ3 upwards ) (equal to the lowstand systyms tract and transgressive systems tract of sequence XIV in Songliao basin), using the data from core, seism, logging as well as examination analysis, and divides the fourth-order sequences into three systems tracts (they are lowstand systems tract, transgressive systems tract and high systems tract).During the depositional period of Yaojia group, this area was controlled by Yingtai depositional system, Qiqihaer depositional system and Keshan - Xingshugang depositional system, developing many types of microfacies, such as underwater distributary channels, underwater distributary inter-channel zones, river mouth bars, far sand bars, sheet sands, shore or shallow lake sand bars and shore or shallow lake muds. The fourth-order sequences SQ1 and SQ2 belong to the sedimentary products of lowstand systems tract of sequence â…©â…£, the sedimentary lake level went down relatively, stratum base level went down, there is little accommodation, sediment supply enough, A/S<1, and it was being affected greatly by the sedimentary material sources in the short axis direction. So the sand bodies in this sedimentary period spread widely, and folded to flaky shape in vertical direction, sedimentary facies zone and lake bank didn't transfer obviously, and the sedimentary facies zone is narrow relatively. On the contrary, SQ3 is the sedimentary products of transgressive systems tract in sequence â…©â…£, the lake level went up relatively, minus sediment supply relatively, A/S>1, moreover, there is smaller effect in short axis direction, and delta sedimentary sand body degraded towards the bank, sedimentary facies zone and lake bank transfer obviously, and the sedimentary zone is wide relatively.Putaohua oil bearing reservoir primarily is middle prosperous and low permeable with sand bodies of bad conjunction and high heterogeneity. According to former classification as well as the distribution and rank of core well porosity and permeability in this area, the researched reservoir is divided into three types (type â…  , type â…¡ and type â…¢), evaluating the reservoir comprehensively according to the result of sedimentary facies, the comprehensive analysis of reservoir lithology parameter, physical property parameter and heterogeneity parameter. The evaluation result shows that type â…  reservoir is dominated by branch channel which is developing in lowstand systems tract; type â…¡ reservoir distributes in different microfacies; and type â…¢ reservoir is dominated by far sand bars and sheet sand which is developed in high systems tract.According to the varieties of geological data as well as reservoir seismic inversion technologies, the oil and gas reservoir formation of the researched area is studied in the sequen(?)e layer framework and the factors which control the reservoir formation are analyzed. The analysis shows that the oil reservoirs are primary sand lens oil reservoir, sand wedging reservoir, stratum-lithological character reservoir and fault-lithology reservoir which are controlled by tectonic, fault, paleotopography, sand body distribution, sedimentary facies and sequence interior structure characteristics. And the sequence development process is determined by the development and the position of sand body. The sequence development is also controlled by tectonic and its evolution characteristics. Sand body characteristics are directly controlled by sedimentary facies whose characteristics determine sand body types, sand body distribution and single sand layer thickness , physical property and so on. Therefore, the sequence development process, its interior...