Innovation and Practice of Geological Modeling Techniques in Complex Clastic Reservoir of Bohai Bay Offshore Oilfield

Abstract

Bohai oilfield located at Bohai Bay of China mainly consists of complex clastic reservoirs. Reservoir prediction is difficult especially in the deep depth oilfields because of low seismic resolution. In addition, how to quantitatively characterize the risk of new oilfield development and how to build a more elaborate model in the late period of oilfield development are particularly challenging. This paper developed an innovative workflow for complex clastic reservoir characterization of offshore oilfield. A modeling method based on sedimentary evolution simulation, which can provide modeling constraints, is proposed for deep depth oilfields. Through sedimentary evolution modeling and other information, reservoir and structure uncertainty are analyzed, then reserves scale and reservoir connectivity are evaluated through experimental design, geological modeling and streamline simulation; 3p models are selected lastly. A new method is proposed for building an elaborate model of old oilfield with less grid amounts. The fluid seepage effect caused by some small scale configuration units is characterized by a parameter similar to fault transmissibility multiplier data in numerical simulation model, for there is no actual modeling of the configuration units, so the operation efficiency is greatly improved. BZ3 oilfield is a deep depth delta oilfield. A geological model was established for exploration evaluation well placement, reserves evaluation and development plan research based on sedimentary evolution simulation and quantitative uncertainty evaluation, the reservoir prediction accuracy is greatly improved that is confirmed by new drilled wells. Through quantitative uncertainty evaluation, reliable geological basis was provided for engineering investment, which can avoid the investment waste caused by geological uncertainty. Q32 oilfield is a fluvial oilfield that has come into high watercut (86.7%). How to characterize the lateral accretion interlayer (often less than 1 meter) in model for fine remaining oil distribution prediction is difficult, thus the method mentioned above for old oilfield was used. Firstly, a conventional geological model was established, then the lateral accretion interlayer was extracted as interface from it based on configuration results, then the interface was used to extract the parameter named transmissibility multiplier data in the numerical simulation model; a software has been compiled to perform the whole process. Based on the method, more than 100 adjusting wells were disposed and better production results were obtained. These geological modeling techniques have been widely applied in Bohai Bay offshore oilfields in different periods of oilfield development, including BZ2, JZ2, KL10, CFD6, SZ3, and JZ9. This ensures that these oilfield developed with high quality and efficiency.