Luna Develops Unique High-Resolution Rock Stress Measurement Concept
Technology creates continuous strain profiles with microscopic detail that increases the safety and production efficiency of subsurface oil and gas systems
Businesses that rely on underground operations, such as the petroleum and geothermal industries, require accurate estimates of in-situ stress, which refers to the existing pressure that exists underground before a hole is drilled. This affects drilling, surveying, and fluid injection (hydraulic fracturing, water flooding, CO2 sequestration) as well as phenomena such as fault re-activation and induced seismicity.
The new technology, Luna’s Continuous Horizontal In-situ Stress Logger (CHISL), uses Luna’s high-definition fiber optic sensing (HD-FOS) and ODiSI® product to obtain direct, high-resolution strain measurements of induced micro-fractures and borehole deformation. New algorithms then process the strain measurements at the borehole to estimate in-situ maximum and minimum horizontal stress and their orientations.
“The development of this new technology -- using existing Luna fiber optic sensors and our ODiSI instrument -- lets the oil & gas industry assess critical parameters that have otherwise been unmeasurable,” said
Luna’s CHISL sensor integrates fiber optic sensors into a flexible hydraulic sleeve, which applies pressure to a borehole wall until small longitudinal fractures are formed. Unlike hydraulic fracturing, where fluid flows into the fractures and causes them to grow in length away from the borehole, CHISL does not allow the fluid to flow into the induced fractures.
“A reliable estimate of in-situ stress is critical for many applications in oil and gas industry. For example, the success of hydraulic fracturing in shales greatly depends on the created fracture height, which in turn is strongly controlled by the stress variations with depth. Luna’s technology would allow stress depth profiles to be estimated with unprecedented resolution,” commented
The CHISL sensor will provide new kinds of data that can be leveraged to increase safety, production efficiency, and optimization of future subsurface engineered systems. Future field operations using a ruggedized sensor could yield in-situ stress measurements for unprecedented lengths of boreholes and in less time than traditional hydraulic-fracturing techniques. Apart from the stress profiling of rock formations for planning of hydraulic fracturing, other applications include caprock integrity sensing for oil wells and optimized drilling of complex oil wells.
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