Effects of cyclic cryogenic treatment on rock physical and mechanical properties of Eagle Ford shale samples - An experimental study

摘要: Abstract Unconventional reservoirs have ultra-low permeability, and the combination of horizontal wells multistage transverse hydraulic fracturing unlocked economical hydrocarbon production from such formations. Fracturing fluid involves large volumes water that is partially recovered during flowback stage, rest remains in formation damaging matrix-fracture interface. In this paper, an alternative waterless stimulation technique has been studied. A cryogenic fluid, liquid nitrogen (LN2), was injected into cores Eagle Ford formation. The effects cyclic LN2 on rock physical dynamic elastic properties were examined. Two cycles injecting at reservoir temperature pressurizing different pressures (1.38, 2.76, 4.14 MPa) implemented. Before after each cycle, computerized tomography scan, porosity, ultrasonic velocities tests conducted samples. results demonstrated treatment increases porosity permeability decreases samples resulting inducing new cracks extending widening existing ones. Permeability enhancement, which creation high-permeable pathways allowing gas to move rapidly across tested samples, noticeable (up 2 orders magnitude). Whilst, comparing improvement not significant 26%) owing small increase pore volume compared sample's bulk volume. showed a direct relationship between injection pressure enhancements completion cycle. Moreover, reductions insignificant changes permeability. Additionally, reduction mainly occurred completing first This because lowering thermal stress reducing possibility creating or propagating current