Field-Detectable Scale Inhibitor for Severe Oilfield Environments

Abstract

Abstract The formation of sulfate and carbonate salts of barium and calcium during oil production and stimulation operations can result in blocked pore throats in the near wellbore region, narrowed production tubing, deposits on equipment, and in more serious cases, formation damage. Polymeric scale inhibitors are commonly used to prevent or slow this process, but one limitation of scale inhibitors is that they must be used at or above the polymer's minimum inhibitor concentration (MIC). Laboratory methods for determining the MIC are well known; however, determining when the scale inhibitor has been depleted below the MIC can prove challenging. One way to combat this is to continuously treat a producing well, but this results in additional chemical consumption and higher operating costs. Polymeric scale inhibitors have been developed that contain detectable tags, allowing the residual polymer concentration to be monitored and reducing the chance of an underdose or overdose. This approach could potentially reduce operating costs; however, sophisticated and time-consuming offsite laboratory analyses, such as ICP or other spectroscopy methods, are required to detect the tags – time during which flow assurance can be compromised. This paper reports an alternative tagged polymeric scale inhibitor that is easily detected by a simple in-field titration and provides outstanding carbonate and sulfate inhibition within favorable cost constraints. Additionally, the new novel tagged scale inhibitor is anticipated to be more environmentally friendly than phosphate-based scale inhibitors, a growing demand in the oil and gas industry. Analyses such as static jar tests and dynamic scale loop (DSL) testing were used to evaluate the scale inhibition efficiency. The performance of the new scale inhibitor versus commercially available scale inhibitor (SI) was highlighted by the DSL, where the MIC was determined to be 20 ppm versus 80 ppm for two widely used scale inhibitors in a barium sulfate scaling brine. The dual benefits of in-field detection and excellent scale inhibition make this alternative tagged scale inhibitor a promising and cost effective addition to the oil and gas industry.