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

Abstract

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.