| The west slope of the SongLiao basin is an eastwards slope as a whole, and the dip of which is less than 2°. The slope can be further divided into three 2~nd order tectonic units:the west overlap zone, Taikang uplift zone, and FuYu structural belt.The Gaotaizi and Saertu oil reservoirs are the major reservoirs in the study area, and in the long-term heavy oil resource’s exploration and development process, it reveals many contradictions such as unclear understanding of reservoir geological characteristics and poor use of the geological reserves. To reverse this state of affairs, this dissertation carried out high-resolution sequence stratigraphy, sedimentary facies and detailed study of forecasting favorable traps in the Saertu and Gaotaizi reservoirs in the west slope. During the research, by combining the theories of high-resolution sequence stratigraphy, sedimentary petrology, structural geology and reservoir geology, the dissertation conducts comprehensive research of sedimentary facies, structural interpretation, reservoir characterization. It also suggests a set of ideas and methods for comprehensive studying the characteristics of the oil-gas accumulation in the gentle slope of a depression basin, and it provides important geological scientific basis for the target of selection and the well design, which has important theoretical and practical significance.With the theory guidance of high-resolution sequence stratigraphy, this dissertation combines two method of stratigraphic correlations,which are high-resolution sequence stratigraphic correlation method and the principles of cyclic deposition. Through the comprehensive analysis of the coring, well-logging, seismic and geological data, the main formations, from the bottom boundary of No.1 member of Qingshankou formation to the top of No.1 member of Nenjiang formation, have been divided into two long-term cycles, nine intermediate-term cycles and sixteen short-term base level cycles. As a result, the high resolution isochronous stratigraphic frameworks have been established. Furthermore, the corresponding relationship between the base-level cycles and sand group has been clarified, as well as the sedimentary filling patterns under the control of the base-level cycles. It has been clearly stated that the west slope is mainly affected by the Northwest Qiqihar source, southwest Yingtai source and northern source. Within the sequence framworks, the dissertation has eatablished sedimentary facies identification signs, and identified as well as divided the microfacies types upon the analysis of the coring, well-longging and particle size data. The dissertation further determines the microfacies distribution and evolution in the west slope. During the period of the GI sand group of the Gaotaizi reservoir and the SⅡ+Ⅲsand group of the Saertu reservoir, the principal sedimentary facies in the area are the delta front facies and shore-shallow lake facies; in the SI-SO period, they are shore-shallow lake facies and semi deep lake facies in the area, and the delta front facies is locally developed in the east of the area. On the basis of sequence stratigraphy and sedimentary research, combined with the 2D high-precision structural interpretation, the main trap types and the hydrocarbon passage system have been analyzed. The structural traps and structural lithologic traps are the main trap types in the Taikang uplift zone. The lithologic traps, stratigraphic-lithologic traps and structural lithologic traps are the main trap types in the west overlap zone. The hydrocarbon transporting system is controlled by the sand and faults. Meanwhile, The reservoir type in the west slope is divided into two catrgories:the structure-lithologic reservoir and the lithologic reservoir. Finally, considering the application of the tectonic and depositional analsis and the law of reservoir sand distribution and hydrocarbon accumulation, the favourable trap and target area of potential benifit can be predicted. |
PDF Full Text Request