A New Method for Identifying Oil-Water Contact in Complex Fault-Block Reservoir Based on Well Logging and Reservoir Simulation and Its Application

Abstract Complex fault-block reservoirs always have intricate oil-water system, which bring challenges on oil-water contact (OWC) identifying. The traditional used methods for identifying OWC mainly based on well logging data, pressure data(MDT/RFT), and well test data. However, in certain fault blocks, pressure and well test data are limited, and it is difficult to identify OWC correctly only use well logging interpretation result. Therefore, a new method based on seismic data, well logging and reservoir simulation is proposed to solve the challenge of OWC identifying. This method mainly contains 4 steps: 1) Updating faults model based on intelligent fault seismic interpretation to build a more accurate structural model and precisely delineate fault blocks. 2) Based on well logging interpretation results and structural models to identify oil down to (ODT), water up to (WUT), and spill point (SP) within each fault block. 3) Using J function to build the water saturation model. By inputting different OWC to build different water saturation models, which are then matched to the well log of water saturation to preliminarily identify the possible oil-water contact (POWC). 4) Using reservoir simulation to identify the OWC. By comparing the history matching results with the production data of water production time and water production rate, the water saturation model is modified to determine the final OWC. M oilfield is located on the strike-slip fault belt, it is a fault-block reservoir which has complex faults and oil-water system. Limited of pressure data and well test data makes it difficult to identify OWC correctly. After the intelligent fault seismic interpretation, the quantity of fault blocks increased 30%, and most fault blocks can’t identify OWC directly. Through the application of this method, OWC was identified. The water saturation model based on OWC matched good with well logging, and the history matching result of reservoir simulation matched good with production data also. New potential zones were discovered by reserve assessment after OWC identification, make a foundation for the development plan design of reservoir. This method integrated seismic data, well logging data and production dynamic data, improved the accuracy of OWC identify by dual matching of well logging and reservoir simulation results, beneficial to the efficient development of complex fault block reservoir. This method not only suit for complex fault-block reservoir, but also suit for other reservoirs.