Fracture study of a horizontal well in a tight reservoir — Kuwait

An integrated fracture study was conducted to evaluate the fracture flow potential of the low permeability Mishref Formation, using electrical open hole logs, borehole images and production data from a horizontal well, and pressure transient analysis from a vertical well. Image logs show at least three stages of intense faulting and fracturing but the reservoir has only a limited fracture flow potential because (i) the early stage of NW/SE faults and fractures were all cemented. (ii) Although NE/SW fractures generated by recent tectonic episodes and very recent NW/SE fault rejuvenation are open and fluid conductive, faulting created fractures only within the brittle layers, which are a few inches thick and dispersed within thick low porosity and ductile units. Faults have wide fractured zones with flow potential only within a 2–5 ft thick brittle layer close to the reservoir top. The development of fracture permeability in a reservoir requires not only deformation and faulting but also the presence of mechanical layers which are prone to fracturing. A high degree of faulting is not a guarantee for a high degree of fracturing. In this particular reservoir, production from fractures is possible only by targeting the brittle fracture prone layer near the reservoir top of the vicinity of faults.