(599e) Production Performance of US Oil Shale Plays Related to Their Depth Profile and Initial Gas Oil Ratio (GOR)

Compared to the conventional oil plays, the shale revolution is relatively a recent development and our understanding of production sweetspots related to petroleum system characterization is a new frontier for research. The objective of this study is to assess the production performances of eight major shale plays in the US basins related to payzone depth and initial gas oil ratio (GOR). We collected well information and production data for 35,909 horizontal wells with at least 24-month production history for the following plays: Eagle Ford (10,782 wells), Austin Chalk (1014), Permian Wolfcamp (3,543), Permian Bone Spring (1726), Woodford (712), Barnet (733), Denver Niobrara (4056), and Bakken (13,343). For consistency in comparison, we calculated normalized production (STB per foot per month) and plotted them against payzone depths. We also investigated the relationship between the initial GOR and the normalized production. These parameters were selected to understand the production performance of the plays in relation to geologic and reservoir conditions. Our data analytics offers significant insights into the performance behavior of the shale plays. Although each shale play has its own characteristics, some general trends are observed. Overall, production per depth follows a bell-shaped profile that can be divided into three zones. The Upper tail at depths of 400-6000 ft. are too shallow for oil generation, and we interpret oil accumulations at these shallow payzones as intra-formation migrated oil from deeper levels. The bulges of the bell curve, which contains the majority of oil wells, are located at depths of 6000-12000 ft; they exhibit the best performance with maximum production per unit of STB/ft//month. These wells and payzone are situated in the present-day oil generation window (60-120 °C). The lower tail of the bell curve at depth of >12,000 feet zone enters the gas window and is thus less productive of oil. The maximum production is partly influenced by fluid properties like initial GOR. Our analysis for all eight plays finds an inverse relationship between normalized oil production and increasing values of initial GORs. A frontier was drawn to obtain the maximum limit of production for a given initial GOR. The novel aspect of our study is reverse engineering of production data to petroleum systems and geological characterization of the shale plays as self-sourced reservoirs. We note that (1) there is intraformational migration of oil to shallower levels; (2) the best producing payzones are situated within the present-day oil windows: and (3) payzones with initially lower GORs have better production performance through the lifespan of each well.