Optimize Performance Through Customization of Paraffin Inhibitor Molecular Structure

Abstract

Deposition of high molecular weight paraffins and subsequent plugging is one of the most prevalent flow assurance risks in both onshore and offshore oil and gas production. Several thermal (e.g., insulation, heat treatment), mechanical (e.g., pigging, cutting), and chemical (e.g., paraffin crystal modifiers, dispersants, and solvents) techniques are used for wax deposition prevention and remediation. Various chemistries such as long-chain poly alkyl acrylates, olefin vinyl acetate copolymers, alkyl phenol resins and esterified olefin maleic anhydride polymers are used as wax crystal modifiers. This study investigates the impact of the alpha olefin maleic anhydride co-polymers structure on the composition and deposition of paraffin. Eight different crude samples from condensates to black oils with API gravity in the range of 30 to 50° were studied. The focus of this research is on paraffin inhibitors’ effectiveness in reducing paraffin deposition that is driven by thermal driving force between the bulk oil and the pipe wall. Inhibitor performance was measured by cold finger testing. Three different alpha olefin (short, medium and long) maleic anhydrides esterified with different fatty alcohols with varying chain lengths were tested for performance. The impact of selected chemicals on amount and composition of paraffin deposit under different test conditions was studied. Wax deposit composition was characterized using high temperature gas chromatography (HTGC) and differential scanning calorimetry (DSC) techniques. Effect of pendant side chain length as well as the composition and molecular weight of the alpha-olefin backbone on paraffin inhibition is presented. Additionally, the impact of test conditions on the composition and hence the performance of the selected chemicals is investigated. We present our findings on selective inhibition of lower molecular weight paraffin depending on the composition of the oil, leaving a much harder deposit rich in high molecular weight paraffin. This is an important observation since a hard deposit would be extremely difficult to remediate in the field and should be avoided. In summary this work provides guidelines for tailoring paraffin inhibitor molecules based on crude oil composition and field conditions, through a systematic structure-performance study.