Spatial and temporal relationships between produced gas and water in marcellus through data mining analysis

The relationship between produced gas and flowback/produced water is important for evaluating shale gas well performance; however, it is not fully understood yet due to complex flow mechanisms and interactions/feedback among various geoscience and engineering controls. Further investigation would provide valuable insight to adjust development plans to achieve optimal well/regional economic production. In this study, an auto-updated nonlinear model method was applied to evaluate the relationship between water and gas in different spatial and temporal domains and to understand the micro-scale flow mechanisms from macro-scale data. Fracture-fluid flowback data in the dataset are water produced within one month, following a fracture treatment (exclusive of well shut-in time), and the produced water were 1 to 3 years. 114 wells from the Marcellus Formation in northwestern West Virginia were selected to investigate the relationship between fracture-fluid flowback and one month gas production in different spatial domains (wet and dry gas regions). 67 Marcellus wells in Lycoming County, Pennsylvania were selected to study the relationship between produced water and gas production across different time periods ranging from one to three years. The results indicate that the relationship between gas and fracture-fluid flowback in the wet gas region is positive while negative in the dry gas region. WGR (water gas ratio) is high (>9 bbl/mmcf) during the 1st-year which indicated water be carried out through displacement and leveled off at 3 bbl/mmcf after the 1st-year, indicating evaporation is the primary mechanism for water production. This study analyzed the relationship between gas and water production under different geological conditions and time periods and offers new insights on gas and fracture-fluid/produced water flow mechanisms in shale gas reservoirs.