Abstract
The number of offshore developments for which long-distance tie-back is usually implemented has increased recently, leading to increasing pressure loss concerns from such systems. In the literature, it revealed that pressure drop in multi-phase transport is quite complex to compute manually. Hence the need for multi-phase flow simulation software. PIPESIM is a leading industry software currently used in the oil and gas industry for multiphase flow simulation. In this study, a 64km subsea pipeline system comprising two sections; 23km, 22.064in ID and 41km, 24inch ID, coated with 3mm (0.003m) polyethene insulation and transporting multiphase hydrocarbon fluid in an ultra-deep-water field was modelled in PIPESIM. Network simulation for the base case was carried out at 114barg (114MPa) inlet pressure and 18.7MMSCfd gas flowrate. The observed system pressure drop was dependent on pipeline inlet pressure, flowrates, and internal pipe diameter. 13.8barg (13.8MPa) was lost from the system for the base case simulation. Sensitivity analysis carried out using Gas volumetric flowrates of 3, 12 and 18.7 MMSCFd. The inlet pressures of 57, 114 and 171barg combined with six different pipe diameters generated a unique combination of 81 data points that were used in the development of a pressure drop correlation using the LINEST regression analysis tool in Microsoft Excel. At high flowrate and high inlet pressure, the pressure-drop observed was minimal and vice versa. Also, at constant flowrates and inlet pressures, the pressure drop was observed to increase with increasing pipe sizes. An R 2 value of 0.9226 was obtained from the analysis. The plot of Predicted Pressure-drop against Calculated pressure-drop similarly gave an R 2 value of 0.8025. Both results showed usefully, and hence the developed correlation can be used as an estimate in the absence of PIPESIM software for pressure drop prediction purposes. Keywords: Pressure drop prediction, Multi-flow Simulation, PIPESIM, Pipe sizing, Regression Analysis DOI: 10.7176/IEL/10-2-06 Publication date: March 31 st 2020
Highlights
The bulk of fluid flow in pipelines/flowlines today, especially in the oil and gas industry is multi-phase in nature (2-phase or 3-phase)
Several factors are considered in the field development plan (FDP), but of utmost importance is considering the viability of flow in the field (Flow Assurance)
The pressure drop experienced can be attributed to the nature of flow which alternates between Stratified and Intermittent flow as well as the pipe roughness and terrain of the pipeline route
Summary
The bulk of fluid flow in pipelines/flowlines today, especially in the oil and gas industry is multi-phase in nature (2-phase or 3-phase). Deep-water oil and gas field development concepts are usually identified in terms of water depth of the offshore location. A critical challenge for ultra-deep-water subsea field developments is maintaining the system pressure or being able to accurately predict the system pressure loss to avoid back pressures or slug flow. This condition has attracted a huge share of the oil and gas industries total annual cost budgets, reserves portfolio and production output. These plans are usually considered during the field development planning of offshore oil and gas fields. Several factors are considered in the field development plan (FDP), but of utmost importance is considering the viability of flow in the field (Flow Assurance)
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