A Comprehensive Validation Methodology for Benchmarking Polymeric Chemistries for Controlling and Inhibiting C60+ Paraffin Waxes in Shale Oils

Abstract

Recent developments in sampling and analytical techniques have enabled scientists to identify and track compositional changes in the molecular weights of paraffin hydrocarbons in organics rich shales wells towards higher molecular weight paraffin hydrocarbons. High molecular weight carbon chains (HMWCs) are generally regarded as the problematic hydrocarbons as they have the highest tendency to precipitate, deposit, and restrict flow in near wellbore zones, flowlines, valves, and chocks. This paper presents a systematic laboratory approach for monitoring and screening for of C60+paraffin waxes in shale oils and field deposits. A comprehensive validation methodology for benchmarking polymeric chemistries in laboratory for controlling and inhibiting C61 – C100 paraffin waxes is discussed based on the results from gas chromatography analysis (GC), differential scanning calorimetry analysis (DCS), X-ray diffraction analysis (XRD), and cold finger wax deposit testing. Modes of action of four polymeric chemistries are discussed based on laboratory data. Results showed none of the polymeric compounds performed as wax crystal modifiers for C60+paraffins, but more likely did disperse C60+wax crystals to some degree. This leads to the alarming conclusion that use of some paraffin inhibitors could lead to a much severe wax deposition when higher amounts of very large paraffin molecules are present in reservoir hydrocarbons. A plausible theory is proposed based on the "folded chain model" and common understanding of how polymeric inhibitors interact with paraffin wax molecules. It was found that model oil systems are more realistic for suitable to screening existing and new inhibitor chemistries for wax control and management when very high molecular weight paraffin molecules are present.