Identification and illustration of relationships between produced gas and water in marcellus under different spatial and temporal domains through data-driven analytics - Nonparametric model

Understanding the relationship between produced gas and flowback/produced water is important for both shale gas well operation optimization and well performance enhancement; however, it is not fully understood due to complex flow mechanisms and interactions/feedback among various geoscience and engineering controls. Data-driven analysis, as an alternative way, could inversely provide valuable insights on the relationship between produced gas and water, to adjust future development plans for well/regional optimal economic production. An auto-updated nonlinear data analytics method was applied to evaluate the relationship between water and gas in different spatial and temporal domains, to inversely correlate the micro-scale flow mechanisms from macro-scale data. In this study, the cases were covered with both wet and dry shale gas regions, as well as short and long shale gas production periods. Fracture-fluid flowback is defined as water production within one month, following a fracture treatment (exclusive of well shut-in time), and the produced water is 1-3 years cumulative water production. 114 wells from the Marcellus Formation, in wet and dry gas regions of northwestern West Virginia, were selected to investigate the relationship between fracture-fluid flowback and corresponding one-month gas production. 67 Marcellus wells in Pennsylvania were selected to study the relationship between produced water and corresponding 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. The discussion of water flow format was done by comparing the water gas ratio at reservoir conditions and at the surface condition. WGR (water gas ratio) is high ( > 9 bbl/mmcf) during the 1st-year and then leveled off at 3 bbl/mmcf after the 1st-year, indicating water initially be produced through displacement, and then be produced through evaporation.