Evaluation Of Unconformity Structure With Logging Data In Eogene In Jiyang Depression

With the exploratory development of non-anticlinal pool at home and abroad, and the exploration maturity of petroliferous basin escalates, unconformity pool indicates the importance increasingly and has been the main object that will increase storage at present and in the future. It possesses all-important geological meanings to study the unconformity vertical structure and learn about its evolution degree and physical property characteristic. The study could lay foundations of research of the hydrocarbon migration and forming reservoir law, and supply technology instrument to master the distribution of unconformable vertical structure underground.The precise depth of unconformity could not be determined with low resolution of seismic data and the limitation of coring data. However, the unconformity could represent exception characteristic on logging traces with the higher axial resolution of logging data and the stratigraphic break formed by itself. So the vertical abnormal variation on logs could be utilized to ascertain the precise depth of the unconformity. The study of logging traces of unconformity under the macro control of seismic data and coupling with the optimum partition method could realize the automatic ascertainment of unconformity.The perfect unconformability is divided into three-layer structures in vertical formation which are rocks upon the unconformity, weathered clay and semi-weathered rocks under the conformity. Based on the response characters of unconformable vertical structure on logging traces, mathematical statistics methods, such as normalization, principal component analysis and so on, are applied to extract the comprehensive parameters which can synthesize the stratigraphic information of logging traces and be used to identify the unconformable vertical structure. And based on the cross plot technique which can be utilized to compartmentalize the unconformable vertical structure, the distributing rule is summarized and the logging evaluation criteria are founded.Applying the methods and the newly developed software, logging data of 123 wells in the depression have been processed and the results are satisfactory. The unconformable depth and vertical structure depth interval computed according to logging data agreed well with those ascertained in geology. The results identified by logging data provide references to master the distribution of unconformable vertical structure underground.