Finding Natural Fractures and Improving Reservoir Performance in WesternVenezuela: An Integrated Approach

摘要

An integrated approach to characterize natural fracturesrnand optimize reservoir performance for Western Venezuela isrnpresented. Due to poor matrix properties, a thorough reservoirrncharacterization is of key importance. Permeabilities arerncommonly in the range of 0.01 mD, with natural fracturernsystems difficult to describe and sensitive to completion fluidsrnand cements.rnThe approach to fractures includes two main topics: fracturerncharacterization and well design. Fracture characterizationrncomprises the description and analysis of the fracture networkrnat several scales from microfractures up to field size, andrnincludes core, well log images, and seismic data. Thernmethodologies used include microfracture upscaling, corerndescription, image log analysis, petrographic thin sections,rnscanning electron microscope images, azimuthal coherencernseismic processing, and Gaussian curvature analysis. Thernintegration of these analyses together with reservoirrnengineering data allowed the selection of candidate zones withrngreater density of open fractures through a semi-qualitativernapproach.rnThe well design includes consideration of optimum wellrntrajectory to maximize fracture intersection and the estimationrnof incremental production based on geometric considerationsrnsuch as fracture orientation, dip and spacing, presence of morernthan one set of open fractures, apparent stratal dip, as well asrnreservoir considerations such as Kh/Kv and geomechanics.rnThese parameters were included in a series of spreadsheetsrnwhich allow fast estimation of incremental production.rnSeveral completion methods were tested in these reservoirs:rncased hole with high penetration perforations, hydraulicrnfracture with pseudo-point perforating, and open-holerncompletions. The results of the different completion methodsrnare integrated in this study to optimize well design.As one of the relevant results of this integration effort, it isrnconcluded that high-angle wells with open-hole completionsrnalong the perforated liners is the optimal method ofrnproduction. This integrated approach allows reclassifyingrnoriginally sub-commercial reservoirs into economic assets.