Wax and Paraffin Control by Fracturing Fluids: Understanding Mode of Actions and Benefits of Water-Dispersible Wax Inhibitors

Abstract

Abstract During hydraulic fracturing operations in oil wells, the equilibrium balance of the crude oil is disrupted once high-pressure fluids are injected into the formation. Fluid temperature is often less than reservoir temperature, and if the formation is cooled below the cloud point, paraffin precipitates may deposit in the formation pores and faces as fractures develop. For paraffin-rich reservoirs, such as shale oil, damage caused by wax deposition at the fracture skin can cause decreased production, slow or hard to clean up wellbores, or failure to achieve predicted maximum recovery. Developments in horizontal drilling and hydraulic fracturing during the past decade provided the industry with a versatile tool that utilized fracturing fluids as a carrier to deliver chemical additives in the form of liquids or solids deep into the reservoir. Chemistries, such as scale, wax and asphaltene inhibitors, are impregnated or infused in porous solids and placed into fractures during the fracturing job, which can provide long-term well protection and production control. Water-soluble additives can be easily formulated within these fluids and/or delivered via slow-release solid products, but the delivery of water-insoluble additives are difficult on an equivalent base. Non-polar additives are not going to be released from solid carriers since the water cut is relatively high within one to four weeks of a hydraulic fracturing job. The risk of organic deposition persists if minimum inhibition concentration of chemical additive is not attained during and after the job. The scope of discussion in this paper will largely focus on water-dispersible systems, in particular to colloidal microdispersion, since they are the most prevalent type of dispersions found to be viable for hydraulic fracturing applications. A methodology is presented that demonstrates the advantages of water-dispersible wax inhibitors that prevent paraffin deposition from waxy crudes in the Bakken, Permian and Eagle Ford basins while complementing long-term control further provided by solid wax inhibitors. This study adapted a novel approach by incorporating wax and paraffin control chemistries into a microdispersion system that is fully dispersible in water. In such micron-sized liquid-in-liquid or solid-in-liquid colloidal dispersed systems, active chemistries comprising polymers from poly (EVA), poly (alkylacrylate), poly (EVA-alkylacrylate), poly (α-olefine-MAA) esters/amides/imides, and selected dispersants and surfactants are brought together to deliver immediateand short-term inhibition for paraffin wax control.