Abstract
Predicting liquids recovery in liquids-rich gas and light oil unconventional plays is impeded by production-related fractionation processes. We present preliminary results of a practical approach aiming at minimizing this uncertainty by (1) mapping hydrocarbon distribution and quantifying theoretical in-situ GOR using geochemical proxies, (2) evaluating the extent of the initial production fractionation based on flow test data and (3) quantifying the saturation pressure of in-situ fluid systems using an Equation of State (EOS) derived from available PVT lab data. Our results suggest that most of the 120 wells of our dataset have under-saturated to near-saturation single-phase fluid systems before production. However, near wellbore depletion can potentially result in large production fractionation, compromising optimal liquids recovery, especially in reservoirs with near-saturation fluids. Our mapping reveals an extensive over-pressured light oil play in northeastern British Columbia that is still largely under-explored. Our approach can help understand the distribution and geological controls of in-situ fluids and reservoir pressure, to better predict risks associated with production fractionation and identify areas with higher potential for liquids recovery.
Liquids recovery from unconventional wells is strongly impacted by production-related fractionation processes. Variations of liquids recovery between wells can result from differences of in-situ fluid composition, reservoir pressure and temperature, reservoir rock properties, well/stimulation design, near wellbore depletion, or any combination of the above. Consequently, production GOR often does not reflect in-situ fluid composition and understanding the causes and the extent of this fractionation is a difficult task given the large number of controlling factors involved. Minimizing the number of unknown parameters is thus key to better evaluate the liquid-recovery potential from multistage fractured horizontal wells. In this work, we propose a practical approach to tackle this challenge and map liquid hydrocarbon recovery potential, by integrating geological, geochemical and fluid PVT information in the liquids-rich gas and light oil Play of the Montney Formation in northeastern British Columbia (Canada).
