Optimization of a development well pattern based on production performance: A case study of the strongly heterogeneous Sulige tight sandstone gas field, Ordos Basin

As a typical tight sandstone gas field with strong heterogeneity, the Sulige Gas Field in the Ordos Basin faces major challenges in its development because the reservoirs in the gas field are small in effective sand scale, rapid in lithologic change, strong in plane heterogeneity, and poor in connectivity. How to scientifically deploy development wells to improve the recovery is the most important issue for the successful development of this kind of gas fields. Therefore, a well inference analysis was conducted to figure out the impact of well pattern density on the recovery based on the research of many years in gas field development methods and the summary of practical effect. In this paper, we put forward for the first time the concept of inter-well interference probability, and present the relationship between the probability of inter-well interference and well pattern density of the Sulige Gas Field. Then we established a mathematical model for the optimization of development well pattern by combining fine sand anatomy, reservoir engineering, numerical simulation and economic evaluation, and obtained a quantitative relationship between recovery and well pattern density. Furthermore, on the basis of comprehensive analysis, a reasonable development well pattern was designed for the Sulige Gas Field: this well pattern is parallelogram in shape, with a density of 3.1 wells/km2, well spacing of 500 m, and row spacing of 650 m. Development practices have confirmed that this scheme is capable of achieving better economic benefits, producing geological reserves as far as possible and improving the ultimate recovery of such gas fields.