Gas wells chemical stimulation - experimental design and field optimization

Retrograde condensation in gas reservoirs leads to long-term loss of condensate and short-term liquid blocking, both of which cause a reduction in well productivity. The problem of loss of condensate was recognized long ago, while that of liquid blocking was not rigorously investigated until recently. Recent efforts have led to a better understanding of the liquid-blocking problem, and numerous approaches, with varying degrees of success, have been proposed to mitigate its effects. Based on the results of a large number of experimental measurements and a few reported field trials, near-wellbore chemical stimulation seems a viable solution to the liquid-blocking problem, though more successful field examples need to be reported for this technology to become a well-established and reliable practice for industry. The main characteristic of the treatment is its effectiveness in bonding to the rock surface and permanently altering its wettability toward non-wetting. Many difficulties arise when evaluating the possible chemicals available for this purpose, especially when the final objective is to design a field trial. A considerable number of papers have been published on the topic, but a publication that combines all the details is lacking. It is extremely important to know the physics behind this treatment approach and have a clear understanding of the key parameters profoundly affecting the outcome of evaluation and decision-making. Development of this knowledge will produce a better assessment of results and a thoughtful decision that reduces the risk of failure for field trials. This paper provides a stepwise procedure for correct evaluation and design of chemical treatment, starting with lab measurement designs and followed by simulation and economic optimization, all of which will help save time, effort, and money. Additionally, this paper highlights the necessary details that should be considered at each stage. (C) 2013 Elsevier B.V. All rights reserved.