Application of horizontal development wells in reserves evaluation and development of offshore oilfields

In the early stage of offshore oilfield development, due to the lack of drilling, limited data admission, and lack of dynamic data, there is great uncertainty in the understanding of oilfield reserves. With increased degree of development, production is usually inconsistent with reserves, and reserve re-evaluation is an important way to resolve this problem. In order to improve the development efficiency and reduce costs, offshore oilfields are dominated by horizontal wells, resulted in limited data acquisition. Therefore, new horizontal well data has become the key to obtainnew geological reservoir parameters and improve the accuracy of reserve estimation. In order to further obtain reliable reserve evaluation results and resolve the dynamic and static contradictions of the oilfield, based on analyzing the main controlling parameters of reserve change in the Pearl River Mouth Basin, this study fully excavates the role of horizontal development wells in improving the accuracy of primary controlling parameters.Our results show that the oil-bearing area and effective thickness are the most uncertain in the reserve assessment, and cause the change of reserves. Horizontal development well is critical in improving the production capacity of the oilfield, determining the lower limit of effective thickness, investigating microstructure, and identifying lithological boundary and fluid interface, etc. In the case of limited data access, the utilizationof horizontal development wells can effectively improve the accuracy of major controlling parameters to obtain relatively reasonable geological reserves, and solve the dynamic contradictions of oilfield production. It also points out the direction for late exploration and development of oilfields. Application examples from multiple oil fields in the eastern South China Sea also confirm this understanding.