Assessment and Diagnosis of Inorganic-Scaling Potential Using Near-Infrared Technology for Effective Treatment

Abstract

Summary Inorganic scaling is a predominant formation-damage mechanism in most producing and injection wells worldwide. Scales are deposited from oilfield brines when there is a disturbance in ther-modynamic and chemical equilibrium. The degree of supersaturation caused by the disturbance in equilibrium can be increased to result in scaling by changes in fluid composition through adverse mixing and by changes in temperature and pressure. Although a few cases have been reported of nonwater-producing oil wells that produced scales, typically oilfield scaling accompanies water production. Scaling problems during well development and supplemental fluid injection are primarily caused by mixing of two incompatible fluids, whereas production-related scaling is typically controlled by pressure and temperature. Acid or any common solvent cannot easily remove some types of scales like barium sulfate (BaSO4), which readily incorporates radioactive radium in its structure. Therefore detection and prevention is critical wherever any precipitation or coprecipitation that includes BaSO4 may be taking place. As severity of scaling is controlled by temperature, pressure, and composition, the key to the detection, prevention, and effective treatment is a methodology to determine at what conditions in the reservoir or at what point in the well the scales are precipitated and deposited, and also to determine the type of scale. This is important because sometimes scales can be forming at a point in the wellbore without showing up at either the surface or at the sandface. Near-infrared (NIR) technology has been used extensively in detecting the organic scales such as asphaltene deposits. To the best of our knowledge, this study presents the first extensive use of NIR technology to diagnose inorganic-scaling problems. This paper presents several examples in which NIR technology has been used to detect the onset of inorganic scale as a function of pressure depletion at reservoir temperature for water from different fields. We also show how the NIR technology has been used to determine the effectiveness of various commercial inhibitors at reservoir conditions. We also present further screening of the inhibitors (selected on the basis of results of NIR tests) to determine their effective use in the field and the design of the inhibitor treatment for the producing wells.