Fracture Flow Research, Volume 1: Modeling Rock Fracture Intersections - Application in the Boston Area and Estimation of the Well-Test Flow Dimension

摘要

Fractures govern flow, deformation and strength of rock masses. Fracture flow is important with regard to resource extraction (water, gas, oil) as well as groundwater contamination. Fractures through their effect on deformability and strength govern stability of tunnels and slopes in rock and the behavior of building,-, bridge - and dam foundations. Very importantly, they also strongly affect penetration resistance. The research consisted of two components, modeling of joint (fracture) intersections and fracture pattern modeling. The two volumes of the final report correspond to these two components. Fracture intersections govern connectivity of fracture patterns and fracture flow (deformability, strength). The research developed an algorithm with which orientation and length of fracture intersections can be represented. The algorithm was applied and tested with a synthetic case and the fracture pattern in the Boston area. Also, an attempt at simplified flow dimension models was undertaken. The results show that complete numerical modeling is better than simplified modeling. Fracture pattern modeling so far was limited to geometric models or simple mechanical models. The research developed a new model to represent fracture (joint) patterns in sedimentary rock specifically, layer perpendicular joints. One model is mechanically based (flaw model) the other one (rejection model) is quasi-mechanical. Both models have probabilistic aspects. The models' predictions were compared to fracture patterns observed in the field. The models, particularly the flaw model perform satisfactorily. Issues requiring further study are joint spacing smaller than saturation and joints which cross more than one layer.