Abstract

Mineral scales frequently form during oil production as the result of changes in temperature, pressure, or the mixing of incompatible formation and injection waters. For hydraulic fracturing, there has been an ongoing effort to replace the use of fresh water with seawater or produced water to address the fresh water shortage issue in many areas in the world. When seawater is injected into the formation, the scaling tendency is inevitable. Among many different types of scale, barite scale, which is a product of the encounter of sulfate ions (typically abundant in seawater) and barium ions (exist at high concentrations in various formations), poses a serious problem. To effectively mitigate this serious scale issue, a combination of water treatment and chemical scale inhibitor is recommended. Nanofiltration (NF) technology has proven to be a reliable water treatment method that specifically removes sulfate ions from water sources with high sulfate content. This paper presents the results of a NF water-treatment process and discusses how the treatment process is a feasible method for barite scale inhibition. In addition, a comparative study of different organic polymers as scale inhibitors was also conducted. For barite scale inhibition in particular, sulfonate polymers were more effective than phosphonate polymers. Scale inhibitor development was conducted using standard evaluation methods, including static bottle testing and a dynamic scale loop. A new, quick laboratory method using ultrasonic vibration was also developed to evaluate scale inhibitor performance during the bottle testing. A combination of NF technology and the new scale inhibitor enabled a new technology to help prevent scale formation during fracturing with seawater or heavy brine water.

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