Prediction of reservoir depletion degree and production GOR using logging-while-drilling data

Data of logging-while-drilling (LWD) log, formation pressure from MDT (modular formation dynamics tester) measurement, and production performance are used to study the relationship between depletion degree (formation pressure), initial production GOR (gas oil ratio) of single well and LWD response of depletion development in reservoirs. The results indicate that the overlap between density and neutron porosity curves from LWD data are related to reservoir depletion degree and production GOR when the formation pressure is less than the bubble point pressure. Larger overlap between the two curves corresponds to lower formation pressure and higher GOR. The relationship between the formation pressure, production GOR and porosity difference between density and neutron porosities can be derived from multi-analysis and regression. Through the analysis of the actual data from Block II of DLL Oilfield, empirical formulas have been established to predict formation pressure and production GOR from the porosity difference between density and neutron porosities. The predicted results correspond with MDT measurements and production GOR data, which proves the high reliability of the methods. Key words: Depletion degree, production GOR, LWD, density porosity, neutron porosity, carbonate reservoi