There are several sets of formation pressure systems in Y structure of block X in Bohai Sea. Shahejie Formation and its upper strata are sedimentary undercompacted layers. dc index method is adopted to monitor formation pressure. The Mesozoic buried-hills are widely distributed in medium acid volcanic rocks, which are non-sedimentary underpressure layers. The formation pressure monitoring method of Sigma index is used to monitor the formation pressure. The real drilling shows that the formation pressure monitoring method of dc index has good applicability in the formation profile pressure monitoring dominated by sand and mudstone. The formation pressure monitoring method of Sigma index has a good application effect in the non-sand mudstone formation profile pressure monitoring, and the combined application of the two provides effective technical support for the smooth drilling. The application of Sigma index formation pressure monitoring method in deep and ultra?deep layers effectively improves the accuracy of the deep and ultra?deep layer pressure monitoring technology while drilling. The practical application shows that the results of formation pressure monitoring while drilling are in good conformity with the measured formation pressure results, and the formation pressure monitoring method of Sigma index has the value of popularization and application in deep and ultra-deep formation.

The Enping formation of Y structure in block X in the east of the South China Sea develops a lake bottom fan deposit formed by the collapse of large sand rich braided river delta front sand body, which is vertically superimposed in multiple stages and has good superposition. The fluid properties in the block are complex and diverse, and there is a common phenomenon of gas production from oil reservoir and oil production from gas reservoir. The oil and gas layers have similar characteristics in logging data, which greatly increases the difficulty of fluid phase identification in the block, thereby providing certain difficulties to the comprehensive interpretation of logging. In view of the complexity of fluid properties in the study area and the difficulty of accurately identifying oil and gas reservoirs by using conventional gas logging anomaly multiple method, gas ratio method, three?dimensional and geochemical logging data, through the optimization of hydrocarbon component interpretation method based on gas logging, this paper came to the conclusion that Bar chart method and star chart method can quickly and effectively identify oil and gas reservoirs in this block. At the same time, the field application shows that the Bar chart and star chart fluid interpretation and evaluation method based on the difference of hydrocarbon component characteristics in gas measurement can quickly and accurately interpret and evaluate the complex fluid in block X reservoir. The results of interpretation and evaluation while drilling using this method are consistent with the results of testing, and the coincidence rate is more than 87%, which provides a reliable basis for the later reserve evaluation of the oilfield.