Integrated approach for the optimal selection of environmentally friendly drilling systems

Ok-Youn Yu 0 Zenon Medina-Cetina 2 Seth D Guikema 1 Jean-Louis Briaud 2 David Burnett 2 0 Appalachian State University , Boone, NC 28608, USA 1 Johns Hopkins University , Baltimore, MD 21218, USA 2 Texas A&M University, College Station , TX 77843, USA There is a pressing need in the energy industry to develop technologies capable of reducing the environmental impact during oil and gas drilling operations. However, these technologies have not been fully integrated into a decision-making system that can reflect a quantitative effort toward this goal. This paper introduces two quantitative decision methods for the selection of environmentally friendly drilling systems. One is based on a multi-attribute utility approach and the other one is based on the analysis of interventions or causal approach. To illustrate the applicability of the proposed methods and to contract their benefits and limitations, a case study is presented using data collected from Green Lake at McFaddin, TX, USA. - Background One of the current goals of the oil and gas industry is to minimize the environmental impact during drilling operations. This is because an effective management of the environmental impacts during drilling operation has proven to lead to a greater access of reserves in environmentally sensitive areas, particularly those classified as off-limits [1-3]. As a consequence, a significant number of Environmentally Friendly Drilling (EFD) technologies continue to emerge, but these have not been integrated into a decision-making method capable of combining them to define an optimal drilling system for specific conditions on a given site. In practice, the major challenge is to select the best combination of EFD technologies based on a set of competing evaluation criteria. In this paper, a system will be defined as a set of EFD technologies. From an engineering perspective, the civil infrastructure needed to complete a drilling operation may strongly condition its success (e.g., access and maintenance of roads, power supply, water availability and management of residuals, traffic and noise control). This interaction is exacerbated when the drilling operations expand on large areas, and at a rapid pace, threatening the sustainability of the inherent civil infrastructure. A number of studies have introduced decision support systems for the selection of drilling well locations [4-7]. A few studies on the best practices on the use of EFD technologies are also available such as in the case of drilling waste discharge [8] and in the design of cementing [1]. However, to the best knowledge of the authors, there are few precedents on a quantitative decision-making method for the integral selection of standard drilling systems. This work aims at introducing a decision-making evaluation protocol to find the optimal EFD system for a given drilling site and also discusses the sensitivity of the inherent input parameters with respect to the expected outcomes. A search algorithm is proposed as the basis of a multi-attribute utility model combined with an exhaustive enumeration of all available technology combinations. This work hypothesizes that optimal decisionmaking on EFD technology selection can be achieved by an integrated approach, which allows decision-makers to minimize the environmental impact, to maximize the expected profits, to account for the influence of public perception, and, most importantly, to guarantee the operation's safety [9,10]. To support this hypothesis, two competing methods for the selection of EFD systems are presented in this paper. One follows a simple system selection approach where no formal consideration on the dependencies between the system components was considered (noncausal approach). The other takes into account the same drilling system components as in the previous approach but, in addition, introduces the effect of the dependencies between events taking place during the drilling operation (causal approach). As it is expected, the non-causal approach permits to reduce the computation time for the selection of the optimal drilling system, becoming a very good reference for preliminary analyses. On the other hand, the causal approach requires further knowledge on the dependencies taking place during the decision-making process, which adds computational effort to the optimal selection of EFD systems. Since the decision-making process is inherently conditioned in a drilling sequence (i.e., reservoir assessment dictates the drilling technologies to use, the area where the drilling is located dictates the technologies used to reduce emission, etc.), a comparison between both approaches seems convenient to address the relevance of interventions as the decision-making for the EFD system progresses. Irrespective of the method used, results show consistent support to the hypothesis that an integrated approach for the selection of EFD systems is needed to maximize the benefits of all stakeholders participating in an oil and gas related drilling operation. To illustrate the benefits and limitations of the proposed methods (non-causal and causal), a case study is presented based on prescribed EFD system selection criteria for a drilling site located in Green Lake at McFaddin, TX, USA. The aim is to help decisionmakers select an optimal drilling system for the site by minimizing environmental impact, maximizing profit, and at the same time accounting for perceptions and safety. In addition to showing the need for the use of an integrated decision-making approach on this case, the differences between each approach are discussed. Results of this comparative analysis show the relevance of introducing causal dependencies between system components during the search for the optimal selection of EFD systems. Methods Optimal drilling system selection This section summarizes an optimal drilling system selection procedure for a given site [9]. The proposed system evaluation protocol defines a decision-making process that ensures the selection of an optimal drilling system according to given criteria. The basis for an EFD system selection includes four main subsystems (Access, Drill Site, Rig, and Operation) and 13 subsets, which have been previously identified through standard EFD operations (see Figure 1). Design of the decision models has been undertaken as part of a comprehensive academic-industry collaboration funded by the US Department of Energy (DOE) and the Research Partnership to Secure Energy for America (RPSEA), which integrates the key drilling phases [2]. Once the subsystems and subsets are defined, available technologies within each subset need to be fully characterized. A drilling technology selection example is also presented in Figure 1, where technologies, indicated within circles for each subset box, represent one possible combination defining a drilling system. Further combinations of technologies are required to evaluate all possible systems and, consequen (...truncated)