Proper Use of Proppant Slugs and Viscous Gel Slugs Can Improve Proppant Placement During Hydraulic Fracturing Applications

摘要

When using hydraulic fracturing techniques to stimulate produc-tionrnfrom an oil or gas well, successful job placement is oftenrnjeopardized by near-wellbore (NWB) problems. Many times,rnthese problems are specifically related to the perforation entry orrnto the width of the fracture near the wellbore. A likely conclusionrnis that insufficient width generation in the NWB region is thernresult of a tortuous (rapidly turning or twisted) path for the firstrnfew inches or feet of the fracture. Within this near-wellborernregion, such fractures must overcome rock stresses greater thanrnthe least principle stress. In other instances, the inadequate widthrnproblem may result from the generation of a large number ofrnindependent near-wellbore fracture planes (starter fractures)rninstead of only one fracture (or at least only a few). Additionally,rnthe hydraulic fracture may initiate from a fluid-filled microannulusrnrather than the perforations, which can lead to significantrnproppant-pumping limitations.rnDuring the early 1990’s, the oil industry began to considerrnthese NWB problems more seriously. Procedures to help iden-tifyrnthe problems were developed, and techniques involvingrnproppant slugs and viscous gel slugs were used to mitigate suchrnproblems before or during a fracture-stimulation treatment.rnAlterations of the well completion plan proved to be a major partrnof successfully reducing the occurrence of similar problems inrnfuture wells in that reservoir. This paper discusses this technol-ogyrnand its evolution through recent years, as well as currentrnapplications of these techniques.