Analysis of the dynamics of saturation and pressure close to the wellbore for condensate reservoirs as a tool to optimize liquid production

Abstract

Gas condensate reservoirs often exhibit a rapid decline in production with depletion. During early production, liquid dropout accumulates in the near wellbore area and this liquid dropout reduces the effective permeability to gas and thereby the well and field productivity. Our primary goal in this research is to understand the dynamics of condensate banking in the near well region of retrograde gases. We propose a relationship that can be used in determining gas oil ratios and near the wellbore saturation. The tasks accomplished in this study of gas condensate reservoir behavior include: Development of a generalized relationship, that allows us to estimate the gas-oil- ratio (GOR) and the effect condensate banking close to production wells. This simple relationship allows us to estimate GOR and condensate banking at any time by using basic data such as saturation pressure, field pressure, gas injection rates, and gas production rates. We recognize and acknowledge that further work is required in testing and improving this relation. We suggest the addition of molecular weights (or specific gravity) of the reservoir fluid to improve the correlative relationship. Comparison of field performance under a variety of production scenarios including natural depletion, gas cycling, water injection, and, the injection of different gases (methane, nitrogen and carbon dioxide). We provide a discussion of the effects of different production schemes upon saturation profiles and saturation histories, as well as the influence of various production-injection schemes on well and field productivity. We also include an analysis of the compositional changes driven by injection and the influence of these changes on reservoir performance.