CHARACTERIZATION OF WAXY AND ASPHALTENIC CRUDE OIL USING SARA ANALYSIS

Flow assurance is the term used to describe the issues that distort the flow of oil, water and gas in production and transportation system. The problems are mainly due to waxes and asphaltenes deposition as temperature and pressure inside wellbore and pipeline changes. Wax will start to precipitate when temperature falls below cloud point or known as wax appearance temperature (WAT) as it travels from reservoir to surface. Experimental data are very limited to confirm the existing prediction models for different type of crude oils.
The focus of this research were to study the characteristic of crude oil in term of SARA (saturates, aromatics, resins and asphaltenes) fractions and carbon distribution by using high performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC-MS) respectively. Differential scanning calorimetry (DSC) and density meter were used to measure the WAT of crude oils. Comparisons of WAT obtained from DSC and density meter were provided and the result shows a good agreement between DSC and density meter technique. Colloidal instability index (CII) was used to correlate the composition of the crude oil with the potential of solid precipitation. A study on the effect of continuous carbon dioxide (CO2) injection on wax appearance temperature of crude oil was provided.
For this research, five crude oil samples from different location (Dulang, Tapis, Miri, Dubai and Arab) were analysed. Each sample has different characteristic hence resulted in different depositional problem. The CII value for Dulang, Arab, Tapis, Miri, and Dubai is 4.09, 1.21, 5.05, 0.64 and 0.90 accordingly. The SARA fractions, WAT, and carbon number distribution of the samples were obtained. The results shows that crude oil samples with higher paraffinic composition have higher wax appearance temperature and wax content than crude oil samples with lower paraffinic composition.
As a conclusion, Dulang, Tapis, Arab and Dubai crude oils have high tendency for asphaltenes deposition while Miri crude oil has low tendency for asphaltenes deposition. The study shows that the CO2 injection will decrease the WAT as tested on Dulang crude oil.