Research On Sedimentary Facies And Reservoir Characteristics Of Yaojia-Nenjiang Formations In Changling Sag

There are good prospecting potential in Changling Sag. Research on reservoir of Yaojia-Nenjiang Formations is less at present, and many problems have not yet fully solved. It is necessary to intensify research degree to make for further petroleum exploration in this area. This thesis is on the instruction of sequence statigraphy, reservoir sedimentology and petroleum geology. Using geology, geophysics and analyzed assay data, the thesis carries out the research of sedimentary system and partition of sedimentary facies belts of Yaojia-Nenjiang Formations in Changling Sag, definitizes the sedimentary facies type and its distribution patterns, sets up sedimentary evolution mode, and studies the reservoir characteristics.Applying the theories and methods of different hierarchical base-level cycles, combined with tectonic background and the evolution characteristics of sedimentary facies sequence, Yaojia-Nenjiang Formations are divided into one super long-term base-level cycle, three long-term base-level cycles, seventeen medium-term base-level cycles, and several short-term base-level cycles. Based on the classification of single well base-level cycles,the regional high-resolution sequence stratigraphic frameworks of Yaojia-Nenjiang Formations are established using cycle isochronous correlation technology.On the basis of analysis on the sedimentology and facies marks, the provenance is from the southwest and south of study area in the period of Yaojia Formation, whie from the southwest and northeast in the period of Nenjiang Formation. According to the detailed observation and description of core, the synthesized analysis is progressed by combinbing the well logging, borehole log, areal geology and all kinds of analyzed assay data, and thus the distribution patterns of sedimentary system are confirmed in this area. Shallow delta, firth/river mouth bay, delta and beach bar sedimentation types are identified, and meanwhile, the new sedimentary modes and sedimentary evolution regular are put forward. In the early stage of Yaojia Formation, with the lake basin whole rising, the water body shallowing, and inadequate supply of sediment, the shallow delta mainly develops in the First Member of Yaojia Formation. While in the late stage of Yaojia Formation, the lake basin begins to expand again, and firth/river mouth bay is the major sedimentation type because of inadequate supply of sediment. In the period of Nenjiang Formation, the hemi-deep-deep lake and shore-shallow lake are developed in the First and Second Member of Nenjiang Formation, water reaches the maximum scale and thin bed beach sands distribute fragmentarily. The water body becomes shallow gradually and the lake basin reduces from the Third Member to the Fifth Member of Nenjiang Formation. Normal delta develops from the northeast provenance, and continues to promote the lake basin, while the constant provenance is absent from the southeast area where is almost muddy sediment.The lithological characteritics, pore structure, and reservoir quality of Yaojia-Nenjiang Formations are researched based on the thin slice, the body of casting thin slice, the scan electron microscope, and so on. The result shows that the sandstones are mainly lithic arkose and feldspathic litharenite. The types of pores are intergranular pores, intragranular dissolution pores, mold pores, oversized pores and fissures. The spread range of porosity and permeability of study area is wide, and porosity and permeability have a positive correlation with a high correlation coefficient. Through evaluating a variety of the factors affecting reservoir quality, sedimentation and diagenesis have a greater effect on the reservoir.