Accurately detecting boundaries for geothermal well drilling

Working alongside Seer, GPC Instrumentation Process (GPC IP), and SMP Energies, SLB leveraged its PeriScope HD™ multilayer bed boundary detection service to help successfully drill two geothermal wells for SIPPEREC's project to expand geothermal heating in the greater Paris region. These wells, producing 450 m³/h of water at 73 degC, will supply 65% renewable energy to more than 8,000 homes in the towns of Grigny and Viry-Chatillon. With a combined heating capacity of 15 MW, the wells are expected to annually reduce CO₂ emissions by 15,000 metric tons, equivalent to removing 700 cars from use.

In 2022, SIPPEREC, which oversees energy and communication operations in the Parisian region, started extending geothermal heating to the suburbs of Grigny and Viry-Chatillon. In recent years, energy poverty and rising conventional heating costs accounted for more than half of expenses for some of the residents. These communities turned to geothermal as a viable solution. Grigny and Viry-Chatillon sit atop the Dogger Reservoir, which provides Paris and its surroundings with access to the one of the densest sources of geothermal heat globally.

As predrilling commenced, several challenges emerged. The new geothermal wells were not only situated close to existing ones, but the targeted reservoir's production layers were exceptionally thin. Conventional vertical wells were insufficient for producing adequate flow rates, therefore creative solutions had to be applied to ensure sufficient production flow rates.

Faced with constraints, a subhorizontal drain well architecture emerged as the sole viable solution to meet the project’s anticipated flow rates. To increase the flow, a horizontal well with a 9.5-in-diameter hole was drilled versus a traditional well with a 7- to 8-in-diameter hole. To precisely target the thin reservoir, the PeriScope HD service was deployed to deliver ultrahigh-resolution, real-time data for reservoir boundary and layer detection. Previously, the technology was used extensively to drill horizontal shale oil and gas wells. The advanced geonavigation capabilities of PeriScope HD service facilitated the precise positioning of the 850-m horizontal well within the most productive layer of the geothermal water reservoir, characterized by a 2- to 3-m thickness and favorable porosity. This precision placement enabled an increase in the well's flow rate and water production, meeting the project's target goals. Furthermore, initial tests of subhorizontal drain wells demonstrated a production increase of approximately 100% compared with conventional wells in the Paris Basin. Following the successful execution of the initial well, GPC IP deemed it unnecessary to drill a pilot hole for the doublet. Instead, the drilling process advanced directly to the doublet horizontal well, saving both time and cost.

Generating 450 m³/h of water at 73 degC, the two geothermal wells will supply 65% renewable energy to more than 8,000 homes connected to a heating network serving more than 20,000 households. Not only will this provide more affordable heating for these communities, but it also will reduce CO₂ emissions from the towns of Grigny and Viry-Châtillon by 15,000 metric tons each year—the equivalent of removing the emissions of 700 cars. This use of PeriScope HD multilayer bed boundary detection service is an excellent example of how oil and gas technologies can play a critical role in advancing the scale of geothermal project developments.