Wax and Asphaltene Deposition Tendency of Malaysian Crude Oils

Abstract

Flow assurance is a term generally used to describe the processes that may lead to fluid flow restriction in production, processing and transportation systems, and also the comprehensive management of the processes and operations to ensure effective and efficient production and delivery of oil and gas from the reservoir to the refinery. Often, the flow assurance issues are largely associated with hydrates, organic waxes and asphaltenes deposition due to changes in fluid composition, pressure and temperature conditions. Organic wax starts to precipitate from oil when temperature falls below the cloud point. The focus of this research is to characterize Malaysian crude oils from Dulang, Tapis, Miri, Dubai, and Arab fields to evaluate their tendency to precipitate wax and/or asphaltene. The oils were characterized by conducting SARA analysis with high-performance liquid chromatography (HPLC), while carbon distribution of the oils was determined by gas chromatography mass spectrometry (GC-MS). Differential scanning calorimetry (DSC) and density meter were used to measure the WAT of waxy oils and the colloidal instability index (CII) was calculated to evaluate asphaltene deposition potential. The effect of continuous carbon dioxide (CO₂) injection on WAT was also investigated. Results show that crude oils with higher paraffinic content exhibit higher WAT and precipitated wax. Continuous gas injection was found to lower the WAT, thus reducing the risk of wax precipitation. Tapis oil with highest CII (5.05) is the most susceptible to asphaltenes deposition, while Arab oil with CII of 1.21 has the least tendency to cause asphaltenes deposition problems.