Multiphase Characterization of Waxy Crude Oil and its Impact to Optimize Flow Assurance Mitigation for Operation and Field Development

Waxy crude oils are crude oils that contain high paraffins content. The paraffins can be of wide range of high molecular weight straight chain, normal paraffin and branched or cyclic paraffin [3]. Flow Assurance issues normally associated with waxy crude oil are wax deposition and wax gelation. Wax deposition is when solid wax crystals precipitate on the colder surfaces of the wall of pipeline, as the temperature drops below the wax appearance temperature. With respect to wax gelation, as the temperature drops lower than the wax appearance temperature, the paraffins will further crystallize [4]. The crystal-crystal interactions and interlocking effects will cause increase in viscosity, leading to ultimately the gelation and solidification of the crude oil [3]. Flows from production wells are in multiphase form. Produced water and associated gas are among the common phases that are produced in every production wells. The separation and stabilization to its individual phase normally conducted at the central production platform, or further downstream at onshore terminal for field with long tie back. The presence of water and gas in the production fluid has an influence on the severity of the waxy crude oil properties. Addition of gas lift, gas injection, water injection, EOR fluid in the field can also have an influence on the fluid properties and phases [4]. Management of waxy crude oil especially in the area of wax gelation had always been conservative. The practice in design and operation normally allocated high margin of uncertainties to totally avoid the wax related flow assurance issues. Based on industrial experience, it is common to develop a field with waxy crude oil flow assurance issues only by referring to its single phase stabilized crude oil properties. It is not common for the multiphase properties, and the influence of the different phases to be included in the design basis. This can lead to over conservatism in curating the flow assurance strategy affecting the economic of the venture. Additionally, new technologies like remote monitoring and machine learning, as well as concerns like impact to green house gas emissions are seldom considered.