Abstract The development, analysis, and evaluation of type curve matching techniques for lenticular gas bearing formations are presented. The type curves are generated using a three presented. The type curves are generated using a three dimensional, single phase, transient reservoir simulator modified to take into account lenticular sand lenses and hydraulically created fractures. The gas bearing sand lenses are assumed to be randomly distributed in orientation and space throughout the formation. Type curves are generated for an unfractured formation and vertically fractured formation with finite conductivity. Assuming different sand lense fractions, type curves are generated and compared with type curves developed for continuous (so called blanket) sand formations. The results of this comparative analysis indicates that the type curves for lenticular formations are significantly different from those of the blanket sand case that it may be possible to assess the degree of lenticularity of a given formation. Conclusions are drawn from the research presented and recommendations given concerning future research efforts.
Introduction Type curve matching is a graphical procedure routinely used for analyzing drawdown, buildup, interference, and constant-pressure well test data. A type curve is a plot of dimensionless pressure change, PD, vs dimensionless time change, t. In general, these dimensionless groups are defined as
(1)
(2)
The variables in the above equations are defined in the nomenclature of this paper. Type curve matching can provide information concerning permeability, porosity, fracture length and distance to a symmetrical drainage limit.
Type curve techniques have been proposed in the literature over the past 25 years. A comprehensive literature review of the relevant papers on type curve analysis can be found in reference 1.
Numerous studies have appeared in the literature concerning the effects of vertical fractures on well productivity. The majority of the papers published are for a slightly compressible liquid assuming either an infinite conductivity fracture or a uniform flux fracture, with little emphasis on finite conductivity fractures or gas flow in the fractures. Sawyer, Locke and Overby, considered the effects of finite-conductivity fractures on gas reservoirs. The authors employed one- and two-dimensional gas reservoir simulators to determine pressure distributions, both in the surrounding fracture and in the formation.
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