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Recent changes in the environmental compliance rules and regulations regarding the overboard discharge of produced water have altered the way well stimulation fluid returns are processed. The flow back of treatment fluids, formetiy handled under exception rules, was handled in a manner which normally minimized facility processing upsets. Wtih the introduction of the new regulations, processing stimulation returns caused system upsets and has even halted production until the flow back treatment has been completely accomplished.The application of a filtration process used to avoid these problems in several acid flow back situations is presented.The filtration process equipment is described as well as operational considerations that may help eliminate facility upsets while maintaining environmental compliance. Discussion of the additive packages tested for pre-job oil emulsion and water oil and grease screening is inctuded. Fluid analysis of the flow streams into and out of the filtration process and cost for four case histories are summarized. IntroductionThe use of acid systems to stimulate or to improve oil and gas production has been around since 1932.1 As the understanding of the acidizing process has been better defined the acid systems have become more and more chemically complicated.These chemical packages added to the live acid system improve not only the removal of damage but also the cfean-up and flow back of spent acid, not to mention the enhancement of hydrocarbon production. 279Accompanying this practice comes the task of processing well stimulation fluid returns without causin 2!I severe upsets in the surface treating facilities. ' Recently, with the new EPA overboard discharge requirements,' processing the aqueous ghase ha! proven to be much more difficult. Bansal, Durham, Houchin,7 Picou,s and others evaluated the reduction or elimination of acid additives and found that this kind of optimization could be taken to only a minimum threshold concentration before sacrificing the chances of achieving successful acid stimulations.All of the additives used in acid systems are, by design, water soluble or at least water dispersible. This characteri~lc maximizes the efficiency of the acid. This same characteristic causes the return fluid stream to have unacceptable levels of these same chemicals, along with their crude oil extractable counterparts. These chemicals show up in the water phase of the separation system. Rather than attempting to reduce or eliminate key mmponent additives in the #lmulation package and sacrificing the effectiveness of the treatment, some other methods of achieving appropriate water quatity were investigated. This paper discusses the necessity of treating the stimulation flow back fluid through separate handling facilities. In this paper, (1) the impact of acid additives on oil and grease content in overboattl water discharges is quantified, (2) the causes of upsets in production facilities are discussed, (3) the vahous options for processing acid returns are summarized, and (4) a ...