Nonacid Solution for Mineral Scale Removal in Downhole Conditions

Abstract

Mineral scales, in particular calcite (CaCO 3 ) and siderite (FeCO 3 ) have been associated with formation damage in oil fields in Colombia. Scale deposition has been observed within the production flowline as well as in the formation. For many years, this scale problem has been addressed through the use of traditional acid treatments. However, this approach caused additional problems such as re-precipitation due to spent acid, clay swelling, and corrosion, giving rise to rapid losses in production, fine migration, and asset integrity concerns. With this in mind, a process to identify the Best in Class non-acid scale dissolver was developed. Through this process, the service company developed a new alternative based on a material with neutral pH, high dissolution capacity, and no reprecipitation. After thorough laboratory evaluation and testing, the product was successfully applied in the field. The first six applications allowed an increase in crude production of approximately 300,000 bbl. This paper details the methodology developed for evaluation and selection of the Best in Class scale dissolver used in this application, as well as the development and implementation of the strategy that allowed the successful field application of the selected material. The practical improvements achieved through this approach and how the approach can be used to develop effective troubleshooting and improvement processes will be discussed. H H 5 0 I I 5 0 J J 5 0 Sample Calcium In Solution (ppm) Powder @ 24 hrs Powder -final (100 o F) Powder @ 24 hrs Powder -final (100 o F)

General Principles of Well Barriers

“…milling), chemical (e.g. acid wash, non-acid scale dissolver), and scale inhibitor treatment options are available [13]. Figure 2.8 shows a scale build-up in a production tubing.…”

Design and Evaluation of Compound Chemical Scale Remover

“…Most of the scale removers only possess single function, that is, special remover for carbonate scale, paraffin and polymer, respectively. For carbonate scale, it is usually removed by an strong acid treatment, for instance, 10% hydrochloric acid can dissolve 95% CaCO 3 scale [2], whereas, the trouble is realized in practice for spent acid, clay swelling and corrosion [4]. Due to the nonpolarity, paraffin is always soluble in organic solvent.…”