Energy Performance Analysis of Geothermal Drilling Rigs in Menengai, Nakuru

Abstract

Economics of drilling a geothermal well continues to be of great concern to drilling companies worldwide including KenGen and GDC in Kenya. Globally, focus has been placed on climate change, global warming, and the adverse effects of pollution caused by thermal fuels as a source of energy. A major uptake of renewable energy has been noted over the years globally where efforts are being placed in the research of wind, solar, nuclear, and geothermal energy utilization. Geothermal is a resource indigenous to particular regions such as Nakuru in Kenya due to the volcanic nature of the Great Rift Valley. In entirety, cost of utilizing geothermal energy, whose key activities involves exploration, drilling, and then power utilization; drilling is the single most expensive venture undertaken that costs up to six (6) million USD. There are many aspects that lead to the total cost of drilling a geothermal well whose primary source of energy is diesel. Obtaining the energy factor cost per unit well and then identifying measures to reduce this cost may save drilling companies substantial amounts of money spent on purchasing diesel, and further improve drilling efficiencies throughout its drilling time. Drilling companies worldwide have invested in the research of industry best practices. Studies have been made with the objective to increase drilling depth with the same energy input or lowering the energy input while obtaining the same drilling depth. In this study, power requirements necessary for the rig operations were addressed. Data obtained included historical records of the rig output, diesel consumed and depths of the well dug; and on-site real-time measurements. Real-time measuring equipment included rig instrumentation, and a digital multi-meter to compare with historical data. It was determined that a typical 2000HP rig would use about 540MWh per month if powered by electricity. With the current KP electricity tariffs as at 2019, it proved cheaper to continue purchasing diesel than to fuel-switch to electricity. Further, by use of the energy monitoring, targeting, and reporting tool, control limits of ±250𝐺𝐽 would be within reasonable range of drilling using optimum diesel energy supply. Comparison between historical data and real-time measurements resulted to a variation of ≈5%. Rate of return of cashflow economic analysis of the retrofit measures proposed had payback periods of less than or equal to three years with initial capital expenses not exceeding two million Kenya shillings. Simple housekeeping measures of switching lights off during daytime and low-cost periodic rig maintenance activities were also recommended. In addition; bidding for a more competitive diesel fuel supplier may offer a cheaper rate thus realizing savings that would otherwise have been accrued by the taxpayer.