Development of Mineral Grouting Technique to Permanently Plug Short Circuits in Geothermal Reservoirs

AltaRock Energy, Inc will develop a technique using in-situ mineralization to manipulate subsurface permeability in an active injector at NGP Blue Mountain Geothermal Power Plant near Winnemucca, Nevada; specifically, blocking a high-permeability pathway typically known as a “thief interval”, “loss zone”, “short circuit”, or “breakthrough interval” in the industry- The well in question, 44-14, has a short-circuit to producer, 17-14, that has been validated through tracer testing and production data, which renders the injector 44-14 ineffective- A unique solution for high-temperature geothermal wells may be the permanent sealing of unwanted fractures with calcium carbonate by mixing urea and calcium chloride- As temperature increases above 120°C, calcium carbonate precipitates; thereby, forming an impermeable layer and eliminating the short circuit- This method was devised and lab-tested at the Energy & Geoscience Institute at the University of Utah with funding provided by AltaRock Energy, Inc- It is patented in the United States (U-S- Patent Number 8091639) by the University of Utah and is ready for field-scale deployment to fully commercialize the product- This product has applicability to both the geothermal, conventional and enhanced geothermal systems, as well as the petroleum industry- In geothermal, injection wells often develop short circuits to producers, causing premature temperature decline in the resource and thereby limiting the project life- Similarly, oil and gas field operators frequently inject steam into oil bearing formations- The increased temperature can improve the “flowability” of the oil and is often used for extraction of very thick or heavy oils- In this process, steam often follows paths of minimal resistance, referred to as short-circuits, that are present or that develop over time- When these short-circuits are present, a disproportionate amount of steam is injected into these which frequently results in poor injection into, and ultimately poor sweep efficiency and incomplete oil recovery from, other portions of the formation-