Abstract
Extensive and detailed research has been accomplished by previous investigators to characterize formation damage caused by various fracture fluid types. Using a simplified method developed specifically to study impairment removal, a body of comparative data was generated to show the tendency of dynamically-formed filter cakes to clean up from formation faces. Data have been developed for most aqueous fracturing fluid types at temperatures from 100 to 300°F.
Of the fluids tested, foams were quickest to clean up followed by uncrosslinked gels and crosslinked fluids, respectively. High viscosity foams produced much thinner filter cakes than non-foamed fluids. Of the crosslinked fluids, borate-based systems tended to clean up more rapidly than systems crosslinked by other metals. Flowing oil stopped all fluids tested from cleaning up, including borates. At temperatures above 250°F, crosslinked fluids exhibited enough thermal breakdown to suggest that damage due to polymer filter cake may be less severe at this temperature.
Field studies after the fracture treatment on five wells showed a high percentage of unrecovered gelling agent residue, suggesting the need for some method to clean up polymer filter cake left in the formation. A special solvent system was developed to remove crosslinked fluid filter cakes. Field results using the filter cake solvent are presented on 33 wells. On 12 of the wells, gel analyses of returns revealed broad ranges of gel content, suggesting that contact with the remaining filter cake is a limiting factor in some cases.
This paper presents a body of data to assist the stimulation planner in selection of fracturing fluids and presents a system to help clean up gel depositions.
