Retrospective Analysis of Hydrofracturing with the Dimensionless Parameters: Comparing Design and Transient Tests

Abstract

Due to the frequent application of hydraulic fracturing technology (HF) on oil and gas fields, there is a large amount of statistical information about the operations carried out. It is possible to make a conclusion about the efficiency of the hydraulic fracturing, consider the design changes and make recommendations on the basis of results of data processing. However this task becomes complicated because conduction of pressure transient analysis on fracking wells reveals that the values of the fracture parameters, in particular the half-length, significantly differ from those planned for design. This paper is devoted to the investigation of the possible reasons of this discrepancy by using dimensionless variables, which allows analyzing of information about the performed fracturing operations. The nondimensionalization of the basic equations using for the hydraulic fracture modeling made it possible to obtain the dependence of the dimensionless half-length of the fracture on the dimensionless volume of the injected liquid, and also to obtain an empirical formula for estimating the half-length of the fracture. Also, the analysis provides a possibility to exclude the influence of different factors that could make a significant contribution to the existing discrepancy. As a result of the analysis, limitation of PTA models, related, for example, to the non-uniform fracture conductivity and the lack of interflow between layers with different properties, as well as the fracture design errors associated with incorrect closing ratios are identified among the most probable causes of the fracture length difference.