Junlei Wang has received his BS and MS degrees in Petroleum Geology from China University of Geosciences and PhD degree in Petroleum Engineering from Research Institute of Petroleum Exploration & Development, China. His research work focuses on transient-pressure analysis of horizontal well and fractured well, complex fracture network, reservoir characterization and simulation. He has published over 20 papers in the oil and gas development fields.
For the purpose of enhancing recovery and economics of shale resource, it is a critical task for petroleum engineers to determine the optimal well spacing in the industry development of shale play. By using various approaches including analogs, numerical simulation and economic assessment, this paper integrated interference response simulation based on multi-well pattern with history data matching to establish a comprehensive workflow for identifying production interference and optimizing well spacing. The workflow is threefold: first, a general semi-analytical model for the distance of pressure investigation was presented to calculate the interference time through fracture and rock matrix; next, a method of interference measurement was introduced to quantify production interference by searching for changes in buildup trends while wells are staggered on/ production and finally, a numerical model of coupling geological and fracture geometry information was proposed to optimize well spacing in multiple-well pattern with purpose of maximizing the objective function of net present value. Based on typical geological and fracturing properties of Zhaotong Shale, design of experiment method (DoE) was utilized to perform sensitivity study to quantify the rank of important parameters including fracture height, conductivity, length, spacing and distance between neighboring wells, reservoir permeability and porosity with reasonable range. Subsequently, Response Surface Methodology (RSM) was employed to fit a response surface of NPV as the objective function, which provided the optimization results of well placement and fracturing treatment design. The results show that: (1) fracture conductivity is more important in short-term production period, while fracture half-length becomes more significant at long-term production period. And the interaction of fracture length and conductivity is more important than other interaction parameters, (2) there is a potential of decreasing well spacing from current 400~500 m to future 300~400 m, with the increasing the number of production wells by 30% and enhancing recovery of reservoirs by 10% and (3) the value of NPV would increase with the production period elongating, but the optimal well spacing kept constant regardless of the duration of production period. This framework provided guidance for engineers to modify the design of fracturing treatment and to determine the optimal number of horizontal wells for a specified play. In addition, this paper provided further research targets such as the impact of fracture interference, alternative fracturing pattern and drawdown management on the optimization of well spacing.