With the current focus on liquids-rich shale plays in North America and the global importance of gas condensate plays, there is an increased need to develop reservoir engineering methods to analyze production data and to develop optimal methods of producing such reservoirs. Without careful planning a gas condensate reservoir can choke on its own production. Drawdown below the dew point of the reservoir fluid can result in condensate liquid dropout, particularly close to the wellbore, the sand face or the fracture face. The increased liquid saturation leads to reduced permeability to gas and, in some cases, significant choking back of the gas production. The impact on well production is most significant for shale reservoirs where most of the total pressure drop is in the formation. In recent EGI research projects (Shale Gas Production Analysis (SGPA) Phase 1 and Phase 2), we have developed a mathematical model of the gas production process from shales. In Phase 2 of that project we explored the applicability of the ideas developed in Phase 1 to production of saturated oil from shale reservoirs. The model developed provided no more than a first pass at analyzing the complex processes at play in this two-phase production system. Nevertheless the results were sufficiently encouraging that further development is warranted. In this project proposal we suggest that, first, an extension to gas condensate plays should be considered and second, a more detailed and rigorous mathematical analysis is merited.
The overall objective is to develop an analytical or semi-analytical model that captures the most important physics of two-phase production from shales. The expected outcomes of this investigation include: