The Value of Underbalanced Coiled Tubing Drilling UBCTD in Unconventional Mature Fields: Decision Analytic Approach

Under-balanced Coiled Tubing Drilling (UBCTD) is a promising method for the redevelopment of unconventional mature reservoirs through re-entries. Yet, such projects have unique technical, geological and economic challenges. Thus, the commercial value is not fully realized. In this paper, we discuss an appraisal method that consider the best number of re-entries subject to technical, geological and economic uncertainties. The methodology involves three main components: 1. Reviewing key papers to assess the primary benefits of underbalanced drilling, and identifying uncertainties related to its applications. 2. Evaluating the appropriateness of coiled tubing drilling for underbalanced applications, including the associated costs. 3. Developing a decision-analytic framework to facilitate sound decision-making regarding the optimal number of re-entries. Our valuation method is based on describing uncertain factors, both technical and economical, and using them in a consistent valuation framework to support analysis and decision-making. The valuation framework also reveals the economic threshold for drilling wells, generating general managerial decision insights. Through this method, we show that technical and market factors influence the decision to use this technology in the development of unconventional mature fields. In this context, determining the number of re-entries is contingent upon the economic threshold, which, in turn, is influenced by market uncertainties. This necessitates employing consistent models to estimate the level of confidence for future oil prices. The proposed workflow provides consistent modeling of the key uncertain factors in a straightforward decision-making framework.