Use of Cumulative-Production Type Curves in Fracture Design

Abstract

Summary When a fracture treatment is designed, the expected increase in productivity or production rate is usually considered. Because production rate varies with time, an economic evaluation based on a production rate increase at a given time can be misleading. A better method of economic evaluation would use the cumulative production after some time period. This can be determined by reservoir simulators that incorporate the effect of propped hydraulic fractures. These simulators are not readily accessible to everyone, however, and are time-consuming and expensive to run. Several authors have stated that cumulative-production type curves can be made with data generated by dimensionless-pressure type curves for a fractured well with infinite fracture conductivity. This paper shows how cumulative-production type curves for finite fracture conductivity can be generated from published dimensionless reciprocal-rate type curves or from reservoir simulators. A simple graphic procedure can then be used to give the combinations of fracture lengths and dimensionless fracture conductivity that will show the desired cumulative production or production rate at some particular time. Charts and simple equations also are given that will allow a quick estimate of the proppant volume required for the various fracture geometries needed for the desired production. This would form the basis for optimizing the fracture treatment. When used with methods to determine fracture fluid volumes for various fracture lengths, the minimum cost for any desired production can be made.