Exploitation of gas/condensate reservoirs presents considerable challenge from day-to-day reservoir-management''s perspective. Initially, uncertainty and variability of liquid content, and volume of reserves in each reservoir pose difficulty in designing surface facilities. Of course, contractual obligations dictate that the required gas volumes are delivered daily, with spare capacity in hand. Management issues of this type occur in the backdrop of potential loss of well deliverability, owing to condensate banking in the well vicinity or from pure depletion standpoint when the well penetrates a small-fault block. Distinguishing the reason for premature rate decline has a profound bearing on project economics and asset management.
This talk attempts to address various issues, starting with well productivity and considering various completion options to modeling the coupled reservoir/wellbore/surface network system. In particular, we explore how uncertainties in volumetrics and capital and operating expenses may influence designing the total system to meet delivery targets. Some of the main findings of our studies show that while condensate banking is inevitable in any system, its impact on well deliverability and reserves depend largely on reservoir permeability, liquid content, completion interval, and mechanical skin. Several useful phenomenological correlations shed light on understanding various issues surrounding management of gas/condensate systems. We also show that a simple screening tool may be used to check whether cycling of lean gas is feasible to improve recovery of condensates, which often constitutes a large component of the revenue stream.