Reservoir Characteristics And Comprehensive Evaluation Of K₁ba₄ In A'nan Sag

After more than 30 years of exploration and development,the water content in the old area of oil field in the Anan sag has been constantly increasing,and the production decline has been serious.The exploration of oil and gas in the new area is becoming increasingly difficult.Under this situation,it is essential to strengthen the research upon the charateristics of reservior,classify and evaluate the reservoirs and predict favorable areas,thus providing favorable basis for further exploration and development.The K₁ba₄ is the main target segment of this study area,and it is located at the top of the A'ershan Formation.After the investigation of the study area's regional geological condition,under the guidance of related knowledge of sequence stratigraphy,sedimentology and reservoir geology,this paper conducts the research of sedimentary facies,diagenesis,reservoir micro structure and physical characteristics,establishes the classification evaluation criteria to evaluate the reservoir of K₁ba₄,andpredict the favorable zone.With the researches above,this paper obtains following results:?1?Based on a great deal of seismic,logging and core data,the K₁ba₄ reservoir is divided into three sand groups.Combining with the research of source,seismic facies and logging facies,this paper identifies the main sedimentary facies as neritic subaqueous fan,turbidite fan and the lake facies?2?According to the data of casting thin-section,mercury pressure curve and core observation,this paper analyzes the structure and physical characteristics of the reservoir.The main pore type of K₁ba₄ is intergranular dissolving hole,and the main laryngeal tract is flake throat and micro throat.K₁ba₄,belongs to medium-porosity,low-middle permeability reservoir on the whole.?3?The control factors of reservoir include sedimentation,diagenesis and tectonics function.Sedimentation mainly controls the reservoir in the form of dominant facies belt.On the one hand,diagenesis can damage original pore to reduce the reserving space;on the other hand,it can generate secondarypore to enhance reservoir property.?4?On the basis of grey system theory and actual condition of study area,this paper utilizes the K-means cluster analysis method and selects five parameters including porosity,permeability,sandstone,sand formation ratio and sedimentary microfacies to conduct reservoir evaluation,divides the K₁ba₄ into I,II,III,IV four types.Combining with the factors including oil source,reserviour type and tectonics,this paper predicts the potential zone of K₁ba₄ reservoir.The mian sedimentary facies are the braided channel and the braid channel side margin in neriticsubaqueous fan.Reservoir are mainly I and II reservoir andfew III reservoir,and the trap type is fault-lithologic trap.