Harnessing the Heat from a Mature Oil Field

Globally, significant volumes of water are co-produced with oil and gas in conventional hydrocarbon developments. Usually, this water is a waste stream at temperatures below 100 °C. However, because of the large volumes involved, this water may still be capable of generating electrical power, which could be used to power field production equipment and offset purchased electricity, reducing the fossil energy needed to extract the hydrocarbons, and so reducing pollution costs. Being able to generate geothermal power from existing hydrocarbon developments can extend the life of a given field by delaying its economic cut-off point. Also, there is scope for eliminating the field abandonment costs for the oil and gas operator, who could hand over the field to a geothermal operator when hydrocarbon production became uneconomic; the geothermal operator would in turn save the initial cost of having to drill and complete wells and install surface facilities. However, there remain potential permit and licensing issues associated to the concept of harnessing thermal energy from oil and gas developments, depending on the specific country and legal process. For example, it is often the case that a geothermal exploitation lease is different from a hydrocarbon lease. This paper presents a preliminary assessment of the potential for generating power from the water co-produced by wells in the Villafortuna–Trecate oil field in Italy. Here, there naturally exist an aquifer that not only provides pressure support to the reservoir, but could also represent an in-situ hydrothermal resource, without the need for external water recirculation. An integrated analysis was carried out to model the fluid flow from the reservoir to surface, via a simplified 1-well system, and through an Organike Rankine Cycle (ORC) plant. The study was based on data and information available in the public domain. Preliminary results suggest that, for a single well draining from a cylindrical reservoir drainage area, approximately 26 GWh of electric power could be recovered over a 10-yr period with an installed capacity of 500 kW. The Net Present Value (NPV) of the waste heat recovery process can be viewed as a “bonus” for the field’s operator, who can re-use the generated power within the existing hydrocarbon extraction process.