Inhibited Gas Stimulation To Mitigate Condensate Banking and Maximize Recovery in Cupiagua Field

Abstract

Condensate banking has been identified as one of the most potentially damaging mechanisms affecting well productivity in Cupiagua Field. This gas-condensate giant field has reached an average recovery factor of 42%, with recovery values of approximately 60% in some layers of field. The mitigation of condensate banking phenomena, among the other important damaging mechanisms currently interacting along the entire productivity zones, has been one of the most relevant stimulation practices in the development strategy.The mitigation of condensate banking led to optimization of common stimulation practices to recover the productivity of gascondensate wells. Massive hydraulic fracturing and matrix stimulation with inhibited diesel and alcohol have been the most common practices implemented and optimized to mitigate condensate banking in Cupiagua field.Because the field is being operated by Ecopetrol (as of June 2010), the mitigation of condensate banking was recognized as one of the most important stimulation challenges to be worked by the stimulation team. The effective mitigation of condensate banking is key to reaching and even exceeding the short-and long-term production targets set by Ecopetrol.This paper describes all the engineering work carried out to implement a new stimulation technique based on the injection of inhibited dry gas. The performed laboratory job, the simulation runs, the engineering design, and the field results are clearly described in the paper, the preliminary results showing that a successful stimulation technique exists to remove and mitigate condensate banking. At the moment, this stimulation strategy has been focused on removing liquid saturation (condensate and water) and organic solids (especially asphaltenes) by incorporating alcohol and surfactants inside the gas stream. Future engineering work will address the incorporation of a chemical blend that can improve the gas-treatment life, thus reducing critical liquid saturation or/and reducing the size of no-mobile condensate rings. OverviewAmong several important sources of damage, condensate banking has become the most important factor in reducing the well potential of the majority of Cupiagua gas-condensate producer wells. The accumulated amount of condensate near the wellbore dramatically reduces the effective permeability to gas and subsequently decreases the well's productivity. When reservoir water is also produced, the problem becomes pronounced, as the combination introduces a third phase to the reservoir, inducing an additional reduction of the effective permeability to the gas phase.Currently, condensate banking is expected to be found anywhere in the reservoir because the current reservoir pressure is below the dewpoint pressure. Water is also being produced in the majority of Cupiagua's gas-condensate producer wells.The use of inhibited diesel (DI) was the first stimulation attempt carried out to mitigate the problem of condensate bank-ing. A nonionic surfactant and a mutual solvent were added to the diesel to generate the s...

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