Gas-Oil Ratio GOR Characterization of Unconventional Wells in Eagle Ford

Abstract

With the increased exploration and development of unconventional reservoirs, the complicated production mechanisms of unconventional wells have gradually become a hot topic among the oil and gas industry. Due to the ultra-low permeability and porosity, the fluid phase behavior in shale reservoirs significantly differs from the conventional fluid phase behavior, increasing the production forecasting complexity. A substantial effort to better understand the mechanisms is the ability to characterize the unconventional well gas-oil ratio (GOR) behavior. The GOR always plays a critical indicator to help predict long-term oil/gas production trends and develop appropriate production strategies. In this paper, GOR behavior was discussed based on an unconventional parent-child horizontal well set in the Eagle Ford shale formation. Subsequently, fracture hit intensity can be determined through the producing GOR characterization. Afterward, the historical production data were well matched. The long-term GOR trends (20 years) were then predicted with the calibrated reservoir model. Based on the simulation results, an interpretation of the fracture hit impact on GOR behavior, and the well productivity was established. This study provides some key insights into GOR behaviors, especially for the parent-child well GOR trends with considering the impact of fracture hits. The Eagle Ford GOR is strongly influenced by the flowing bottomhole pressure. Meanwhile, the GOR trends of both parent and child wells are extremely sensitive to fracture hits, strong correlations between GOR and fracture hits are observed. Compared to the parent well, the flat GOR period of the child well is much shorter due to pressure depletion. The existence of a child well also reduces the rising speed of the parent well with a lower plateau. In addition, the long-term production prediction shows that fracture hits negatively influenced both well performances, where the child well has a more severe production loss than the parent well. Through the findings presented in this work, a better understanding of the unconventional well GOR behaviors can be obtained. The analysis approaches proposed in this paper provide valuable insights into GOR characterization and contribute to the production forecasting from unconventional plays. The results can help to improve the efficiency of reservoir management, field development, and economic valuation in future projects.