Identification And Evaluation Method Of Jurassic Complex Oil Layers And Water Layers In Western Margin Of Ordos Basin

Relying on the project “Fine Logging Identification Technology of Mesozoic Low Contrast Oil Layer in the South Section of Tianhuan Depression”,this thesis takes the Jurassic Yan ’an Formation reservoir in Huanxi and Pengyang area of Ordos Basin as the research object.The reservoirs of Jurassic Yan ’an Formation are complex,with unclear electrical regularity and formation mechanism,poor adaptability of identification methods and charts of oil and water layers,and low coincidence rate of logging interpretation.In order to clarify the formation mechanism and improve the coincidence rate of logging interpretation,this paper analyzes the reservoir logging characteristics of92 wells in the study area,combined with core analysis data,oil test conclusion,rock electricity experiment,formation water analysis data,etc.,and considers that there are two causes that make it difficult to identify the oil-water layer of Jurassic Yan ’an Formation in Pengyang area around the west of China.First,due to the development of fault system in the study area,the salinity of formation water varies greatly and its distribution has no obvious regularity.Second,it experiences secondary reservoir formation due to the influence of tectonic movement,and some of them.This thesis is based on the formation mechanism of two low contrast oil layers,which are complex salinity of formation water and wettability.By analyzing the logging response characteristics of oil-wet reservoirs,the identification methods of oil-wet reservoirs are summarized,and the wettability identification chart is established,so that the reservoirs can be divided into oil-wet reservoirs and water-wet reservoirs.Based on the analysis data of formation water,the resistivity of formation water is accurately calculated by using spontaneous potential curve.A set of calculation methods of reservoir parameters are formed according to the formation mechanism.According to wettability,two identification charts of oil layers and water layers are established combined with the resistivity of formation water.The coincidence rate of logging interpretation is greatly improved.