Formation Mechanism And Well Logging Evaluation Of Low Oil Saturation Reserviors In Dongying Formation Of Nanpu Sag

The low oil saturation reservoirs,as a special reservoirs with strong concealment,has great exploration potential.Recently,the research on low oil saturation reservoirs is still in the exploration stage all over the world.There is no consensus on the definition,formation mechanism and development pattern of low oil saturation reservoirs,and no systematic and effective methods have been established for identification and evaluation.Dongying Formation of low oil saturation reservoirs in Nanpu Sag.on the basis of the research literature around the world,the concept of low oil saturation reservoirs is identified.using analysis assay data and logging data,the reservoir in Dongying Formation from the aspects of sedimentation,diagenesis and pore structure using the method of multi?factor overlay is divided into four types.With the test data the clear reservoir types can control the low oil saturation of reservoirs.The second and third types of reservoirs develop the low oil saturation.The main reasons for the high irreducible water saturation are mainly fine lithology,high percent of shale,shale like,Iraq/get high percent of clay mineral,and complicated pore structures.Meanwhile the parameters of irreducible water saturation and comprehensive evaluation coefficient were established.The logging identification and evaluation of low oil saturation reservoirs are realized with conventional logging and nuclear magnetic logging.The establishment of the method system not only guides the development and production of Nanpu Sag,but also facilitates the increase of oil and gas reserves and production.