The existence of natural fractures in hydrocarbon bearing formations may significantly enhance hydrocarbon production rates and recovery factors. Horizontal wells or drainholes drilled in these types of reservoirs (especially tight gas reservoirs) increase the possibilities of intersecting discrete natural fracture systems in ways that render high well productivity indexes and higher recovery factors than vertical wells, thus enhancing field developmental opportunities.
The performance of horizontal wells in naturally fractured formations and their ability of draining the formation effectively depend on a number of well and formation parameters. Simulation results clearly illustrate that the well location within the flow region, degree of fracture clustering, fracture density, fracture aperture distribution, along with the degree of fracture interconnectedness can govern gas production rates, ultimate gas recovery and reservoir drainage patterns (Hatzignatiou, 1999). Therefore, gas recovery factors for tight fractured reservoirs may differ significantly from those of homogeneous reservoirs with large formation permeability.
This work demonstrates a means of estimating well recovery factors in single-phase gas naturally fractured reservoirs. Uncertainties in these estimates due to network heterogeneity and variability in the connection between the well and the network are quantified in the form of probability-based recovery factors. Emphasis is placed on horizontal wells because these wells are commonly used in developing and producing tight fractured reservoirs.