Experiments and Analysis of the Hydraulic Fracture Propagation Behaviors of the Granite with Structural Planes in the Gonghe Basin

Abstract

Hydraulic fracture (HF) propagation behavior is significant when building enhanced geothermal systems (EGS). HF geometry is closely related to the structural planes (SPs) in hot dry rock (HDR), such as natural fractures (NFs), quartz veins (QVs) and lithologic interfaces (LIs). However, the HF behaviors in HDR have not been well understood, especially the influence of multiple SPs on the HF geometry. To clarify this mechanism, several groups of physical simulation experiments of hydraulic fracturing were conducted to investigate the intersection relationship between the HFs and the SPs. Results show that the HF geometry shows great differences when intersecting with different SPs. In summary, the HF geometry displays four basic patterns, namely, propagation along the SPs, branching, capture, penetration/non-dilation. The fluctuation degree of the pressure-time curve and the HF complexity show a positive correlation. The cementing strength of the SP and their different mechanical properties from rock matrix influence the HF behaviors significantly. Therefore, the HF shows diverse geometries when intersecting with the NFs and LIs, while propagating along the QV when intersecting with it. For the complex networks, it is favorable for the HF to penetrate through and dilate several SPs, rather than simply cross or propagate along the SP.

Multiphysics coupling in exploitation and utilization of geo-energy: State-of-the-art and future perspectives

“…Previous experimental studies indicate that the change in mechanical properties of rock mass is controlled by high-temperature fracture and crystal lattice transformation. The principle of the primary reservoir stimulation method (e.g., hydraulic fracturing, thermal and chemical stimulations) is to change the permeability of the reservoir (Xie et al, 2021;Xu et al, 2021). However, it is difficult to reproduce the conditions of deep geothermal reservoirs because the laboratory tests are usually conducted after cooling.…”