Session: 11-10-01 Sustainability and Green Transition in Petroleum Industry

Submission Number: 157109

Techno-Economic Analysis of Geothermal Well Designs: Slim and Standard Hole Well Construction 

The sustainable energy landscape increasingly focuses on geothermal resources due to their renewable and cleaner nature. Geothermal energy extraction, like hydrocarbon exploitation, requires well drilling and completion to access heat from high-temperature geological formations. Despite their environmental benefits, the economic feasibility of constructing geothermal wells often faces challenges. These may include higher costs and complexities compared to oil and gas wells, primarily due to the enhanced axial rating requirements for casing strings that must endure significant tensile and compressive stresses. This study proposes a methodology to reduce the construction costs of geothermal wells, aiming to improve the financial viability of enhanced geothermal systems (EGS) through cost-effective well design.

This analysis employs specialized cost modeling software to generate deterministic cost estimates and visualize the outcomes. Parameters such as well path, formation data, and casing specifications are integral to the methodology. The study investigates the economic potential of drilling two slim hole injectors and one big hole producer at a cost equivalent to that of two big hole injector-producer pairs. It assumes that recent advancements in drilling technology could overcome the inherent drawbacks of slim hole drilling, such as reduced penetration rates.

It is well acknowledged that geothermal systems typically require a producer and an injection well to harness the subsurface heat. While doublet's philosophy has been refined and we have fourth to sixth generation of doublets concepts, a new model is proposed within this paper which includes heat loss effects into the well cost model. The paper will first show the two main cases used for the analysis: classic doublets fourth generation using two identical wells and the new concept using one large producing well and two smaller injector wells. Next, a well cost model will be created for each one of the concepts highlighting the differences and advantages. Finally, the geothermal well farm concept will be discussed in view of the new proposed concept. The results indicate that the total deterministic cost for constructing a pair of slim hole injector wells could be comparable to that of a single standard hole injector well. The novelty of this research lies in its examination of multiple injector-producer triplet EGS wells, emphasizing cost-effective drilling and completion techniques. By utilizing lighter, but stress-qualified casing strings and reducing the need for a higher volume of cement and costly rig equipment, operators can optimize material usage and lower overall project costs. This approach could significantly enhance the economic returns from geothermal energy projects, which typically yield slower financial benefits than those derived from fossil fuels. The paper will conclude with a thorough cost comparison and wellbore thermal highlighting the advantages of the proposed concept.

Presenting Author: Catalin Teodoriu University of Oklahoma

Presenting Author Biography: Dr. Teodoriu is a professor of Petroleum Engineering at The University of Oklahoma, Norman, Oklahoma. Prior to joining the OU, he was assistant professor at Texas A&M and Head of the Drilling, Completion and Workover Department at the Clausthal University of Technology, Germany. He has more than 28 years of experience in the petroleum industry and academia, with key qualifications and research in drilling and production equipment, drilling technology, integrated computer-aided analysis, well completion, testing of OCTG, design of downhole and surface equipment, software development, EOR, geothermal wells, and in the design of laboratory-specific equipment (i.e. high-pressure testing, large scale testing equipment for multiphase flow and drilling process simulation). He is specialized in developing new threaded connections for OCTG as well as an expert on drilling problems and failure analysis. Some of his recent research areas at the OU includes the largest drilling vibration setup worldwide, development of cement repository for long term investigations as well as geothermal well construction and well integrity as well as development of complex mechatronic systems designed to support AI and Machine Learning applications. He is the author of more than 350 publications, from which 95 peer-reviewed articles and two book chapters. He was awarded, among others, the SPE Drilling Engineer Award and Outstanding Reviewer for SPE Journals. He is also well recognized in delivering customized industry courses covering drilling, completion, well integrity and geothermal topics.