Study On Hydrocarbon Accumulation Law And Target Preference Of Putaohua Oil Reservoir In Talaha Syncline

Based on the theory of high-resolution sequence stratigraphy and its technique and seismic sedimentology,this paper uses the data of core,logging and 3D earthquake in the exploration area to identify different levels of base-level cyclic interface.In the Talaha region,putaohua oil reservoir is divided into a long-term half base level cycle,three medium-term base level cycles and eight short-term base-level cycles and several ultra short-term base-level cycles.The high-resolution sequence stratigraphic framework is established uniformly and well and stratigraphic ladder thinning mode of the syncline controlled by the inherited paleo-uplift is proposed.Based on the understanding of sedimentary system,provenance,sedimentary characteristics,this paper divides it into 8 short-term cycles.the distribution of sand bodies is summarized.Sedimentary model of the inner delta front subfacies zone of large,medium and small underwater distributary channel and river sheet sand,outer delta front subfacies zone of medium,small and minimum underwater distributary channel(end)and the wave control peripheral sheet sand is established.On the basis of understanding the structural characteristics and tectonic evolution of the region,the fault evolution process is analyzed and the fracture system is divided to determine the oil source fault.The fault is divided into three categories according to the size of the slip in putaohua oil reservoir by fine seismic interpretation The maximum vertical fault length less than 5m,the maximum vertical fault distance between 5m and 10 m,the fault with maximum vertical fault greater than 10 m.The fault development and distribution characteristics in this area are studied.Based on the comprehensive view of the modern oil and gas geology and the comprehensive analysis of regional reservoir formation,based on the distribution of oil and water production in different tectonic zones and a fine typical reservoir profile covering the whole area,the paper carries out research on the distribution of oil and water in the talaha area,summarizes the gradual transition from syncline center,slope,single lithologic reservoir in structural high part,fault-lithologic reservoir,to structure-reservoir.The connectivity model of the sandstone reservoir in the study area is quantitatively evaluated by sandbody connectivity probability model.Combined with the sand body connection range and different breakage fracture,oil source fault configuration relationship and its control of oil and water distribution,the paper concludes that halahai slope dip angle is small,sand ratio is between0.25~0.65,the ratio of sandbody connection is between 0.3~0.6,sandstone with strong transport capability,the most vertical faults are more than 10 m with oil source,the oil and gasare moving west along the upward inclination of the halahai nose structure,with more water and less oil.The dip angle of longhupao slope is large,sand ratio is between 0.05~0.25,the ratio of sandbody connection is between 0.1~0.15,sandstone connectivity is poor,the vertical fault distance is between 5m to 10 m,the oil source fault which vertical distance more than10 m are more,sandstone and fracture are well configured,pure oil reservoir,oil and water reservoir are more,and fault lithologic reservoirs are easy to form.In the talaha syncline lower center sand ratio is between 0.1~0.65,ratio of sandbody connection is between 0.1~0.3,sandstone connectivity is strong,the oil source fault which vertical distance more than 10 m are more,a single lithologic reservoir and fault lithologic reservoirs are relatively developed as reservoir and dry layer exist mutually.The paper concludes that ratio of sandbody connection is between 0.1~0.3,fracture distance of oil source is more than 10 m,which has important reference value for guiding oil and gas exploration.Comprehensive fracture,sand,structural configuration and control of oil and water distribution,the paper proposes four types of hydrocarbon accumulation in talala area : hydrocarbon accumulation pattern of forming oil in longhupao nose structure;hydrocarbon accumulation pattern of sandstone connectivity in halahai slope;hydrocarbon accumulation pattern of reverse fault occlusion in longhupao slope;hydrocarbon accumulation pattern of low-porosity,low-permeability lithology in talaha syncline center.According to the above-mentioned reservoir-forming rule,the prediction of the delta front thin-layer sand body is carried out with the seismic waveform inversion technique,The accuracy of single sand body prediction has been greatly improved with 68.7%,43 lithologic traps are predicted.4 drilling targets are proposed in the tahala center,1 wells get high yield,achieving the gratifying economic value.