This paper describes laboratory studies and field results of a Zeta Potential Altering System (ZPAS) used in hydraulic fracturing treatments. Laboratory and field results show ZPAS minimizes proppant flow back, controls fines migration, enhances fluid load recovery, and inhibits calcium carbonate scale formation. This system, based on an inner salt, modifies the zeta potential of particles such as frac sand and formation substrate, changing the charge towards neutral values and therefore enhancing particle agglomeration. A variety of oil and gas formations can be treated by incorporating the new chemical additive into stimulation fluids. The chemical additive can be applied on the fly using several fluid systems to deliver the product. It is capable of treating proppants such as white and brown sand as well as ceramic proppants in any mesh size allowing flexibility in treatment design. A multi-well comparison of fractured wells, treated with ZPAS and of offset wells without the chemical, has been made in the Des Moines Granite Wash formation of the Texas Panhandle. In this study, results show wells treated with ZPAS had no significant proppant flowback compared to non-treated wells. In one case, a significant difference in production was observed from the ZPAS treated well compared to the untreated well. IntroductionProppant flowback following hydraulic fracturing treatments has been an issue in several regions for the oil and gas industry 1-3 . Proppant flowback is related to the conditions of the field, formation stresses, and the fracture treatment itself. Stimulating a formation with a hydraulic fracture creates a conductive path from the wellbore by placing proppant into the formation extending the effective wellbore radius. If proppant placed during a fracture treatment flows back, the resulting problems can range from sanding off a submersible pump to erosion damage of down hole and surface equipment. Cleaning up produced sand is an added cost to operations and there is the additional cost due to lost production which can not be recovered until the end of the life of that well. The cost associated with cleaning out the proppant flowback ranges in price depending on the type of clean up required, therefore it is necessary for operators to prevent the flowback of proppant whenever possible. Several different methods have been proposed and evaluated over the years.
This paper describes lab studies and field results on how a new Zeta Potential Altering System (ZPAS), utilized in fracturing treating fluids, improves gas rate production. Lab and field results show ZPAS minimizes proppant flow back and coal fines migration, enhances fluid load recovery, and inhibits calcium carbonate scale formation. The mechanism of this system based on an inner salt that modifies the Zeta Potential on particles such as frac sand and formation substrate, changing the charge towards neutral values and therefore enhancing particles agglomeration. This paper also shows how the Zeta Potential Altering System has been applied in numerous coalbed methane wells which were treated by refracturing. The ZPAS has been run in borate cross-linked fluids and linear gel systems. Field results have been positive on wells treated, with less time to clean out frac sand, less flow back sand and coal fines, higher conductivity after load fluid recovery, and higher gas productivity after load fluid recovery and de-watering of CBM Zones. Production has increased up to 15 fold on individual wells with 3 to 20 months production history. IntroductionSeveral factors may affect the productivity of a fractured well. 1-7 Invasion of fines into proppant pack affects the permeability, resulting in early decline in well productivity. Besides this, conductivity of fractured wells with 16/30-mesh standard sand could be significantly decreased when crushed at closure pressures. Invasion of coal fines and proppant may result in early downhole mechanical pump failures. Current approaches to the problem of coal fines and proppant flow back have been flowback preventative additives such as; fibers, resin consolidation systems, ceramic proppants, and resin-coated proppants. Different proppant coating systems have been designed to control the movement of fines generated from crushed proppant: polymer based tacking agents, phenolic resins, furan resins, epoxy resins, and urea-formaldehyde resin among others. These systems also prevent proppant flowback. 8
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