Near-Offshore Oceanic Geothermal Resources Developed from On-Shore Directional Drilling

Abstract

New opportunities have emerged for the application of oilfield technologies transfer, such as directional drilling, to utilize base-load renewable energy. Development of geothermal resources have largely been restricted to on-shore sites, yet a major category of untapped geothermal development prospects are near-shore resources. Development of near-shore geothermal resources can provide renewable base-load electrical power options to areas that are now served by non-renewable power generation which can supply domestic, commercial, or industrial land-based and marine use. It may also support emerging technologies such as battery charging and green hydrogen generation for land-based and marine transportation or commercial applications. Additionally, the need for reliable and renewable base-load electrical power to support U.S. Naval operations has increased markedly in recent years, particularly in the western Pacific. The advantages of geothermal over other advanced renewable power sources is its base-load reliability, a relatively small footprint in terms of land use and the long-term durability of the equipment. Additionally, this generally untapped energy field provides an opportunity for oil and gas development companies to expand the application of their technology, experienced staff, and knowledge. However, as exploration and development of these geothermal resources may have substantial effects on their near-shore locations, it is important that this development recognize the commercial and environmental value of the near-shore marine environment and mitigate any effects from these activities. Many of the potential near-shore and shallow marine geothermal plays are associated with volcanic activity. However, non-volcanic structural plays also hold significant potential (figure 1). Perhaps the most dramatic and well-documented volcanic hydrothermal sites are the spectacular deep marine "black-smoker" vents associated with oceanic spreading centers. Yet, other than a few notable exceptions, such as Iceland (Atkins & Audunsson, 2013), these systems are usually located far from shore in deep marine environments (Hiriart et al., 2010) and have currently limited potential for widespread development. Other volcanic geothermal resources occurring near-shore are like structurally controlled settings observed on land. Examples include: Lihir Island, Papua-New Guinea (Peterson et.al., 2002; White, et.al., 2010); in the Mediterranean Sea (Fytikas et.al., 2005; Meteoboy, 2013) and the shores of Mexico’s Baja Peninsula (Vidal, et.al., 1978; Prol-Ledesma et.al., 2002). The western Pacific area is rife with volcanic islands. Yet only a few of these volcanoes have had geothermal resources developed for electrical production. One of the limiting features for geothermal evaluation of these volcanic islands is that, while they are often massive volcanoes, only the central top of the volcano is exposed above the water, while the bulk of the flanks are submerged beneath the sea. These volcanoes would have the same geothermal resource potential as their terrestrial counterpart but due to their partially submerged setting, they have been out of view and out of mind for the geothermal development community. With advances in directional drilling technologies over the past decades, it is now possible to develop near-shore (1~1.5 km) geothermal resources from on-shore locations, increasing the economic viability of these prospects while minimizing seafloor disturbance.