The Art of Debottlenecking to Optimize Production in a Crude-Oil Processing Facility

Abstract

When operators feel comfortable with the performance and safety of a facility producing at its design conditions, it becomes natural for them to push the service company to produce even more. While it might appear safer to increase the capacity beyond the initial design of a crude-oil processing facility than a gas processing facility, many points must be checked using a debottleneck study to guarantee a safe and reliable operation. Schlumberger production facilities engineering, and operations teams collaborated on a debottleneck study to increase the capacity of a Middle East crude-oil processing facility by 40% of its design, which helped to achieve the annual production targets. Debottleneck studies require deep knowledge of the processing train and early identification of equipment presenting significant limitations, which, in a crude-oil processing facility, is the oil train equipment (i.e., heater treater and desalter). Validating these two pieces of equipment was the first step to overcoming challenges to increasing capacity. The original design of the heater treater used a forced-draft burner system, and the study showed severe limitations to safely releasing the necessary heat for the increased throughput. A change to the burner type and configuration was identified as a need; a natural-draft burner system was installed in addition to modifications to the fuel-gas train. This change enabled a greater heat release without compromising the mechanical integrity of the heater; however, because of limitations regarding the heat transfer surface area, total duty to the process fluid remained limited. To overcome this challenge, a mechanical device (turbulator) was designed to increase the convective heat transfer coefficient. The combined effect of these changes resulted in the delivery of the required heat duty to process fluids. For desalting, the challenge was in achieving the required salt specification. Key variables studied were the salinity of the wash water, mixing efficiencies, and the feasible extent of dehydration. Because of the high salinity of the wash water that was being used and limits to the mixing efficiency and ability to achieve deep dehydration, the recommendation was to change the wash-water source to fresh water. Detailed salt balance calculations demonstrated the incremental production increase from using fresh water. In addition, adequacy checks of other process equipment, storage tanks and their venting systems, pumps, pipework, valves, instruments, and utility systems were reviewed and confirmed to be suitable for the increased capacity with only minimal changes. The required modifications were implemented following the approved change management procedures and optimization of the process parameters of the entire processing facility by the operations team. This ensured a smooth and safe operation at a 40% greater flow rate than that provided by the design. Being the technology owner, integrator, and processing facility operator allowed the service company a unique opportunity to conduct a detailed system-wide study, seek real-time performance feedback, and understand the limits, constraints, and opportunities for expansion. These modifications also ensured considerable reductions in greenhouse gas emissions by means of enhancements to the efficiencies of the heating systems.