Abstract

LedaFlow® is a new transient multiphase flow simulator which includes 1Dmulti-fluid models consisting of mass, momentum and energy conservationequations for each field (continuous, bubble and droplet), as well ascompositional tracking. In this paper, a new method called Slug Capturing isemployed for slug flow, and the results analyzed and compared with the fielddata of two different fields. Additionally, for some cases, differences betweenthe new simulator and another commercially available transient code results arecompared and analyzed.

The first case corresponds to the production of a TOTAL-operated field in theUK. Produced fluids from the wells are transported through a 21 km long,16-inch multiphase flowline from the well platforms to the central receivingfacilities. The multiphase line (gas/oil/water) must be operated in a narrowrange of pressure and flow rate conditions in order to avoid severe sluggingissues. Flow patterns are compared for various water cuts and superficial gasvelocities. When severe slugging is observed, slug characteristics (frequency, length) are analyzed and compared to simulator predictions.

The second case is from a CONOCOPHILLIPS-operated North Sea asset. The 3-phase,18-inch ID oil flow line runs 3.7 km from a wellhead platform to a centralprocessing platform. The line drops approximately 6 m over the last 3 km beforeflowing up a 130 m riser. The pipeline exhibits severe riser slugging which isnot adequately modeled by conventional transient models, due to the complexinterplay between hydrodynamic and riser slugging, as well as 3-phase effects. Slug frequencies and lengths are analyzed and compared to predictions.

Background
The LedaFlow 1D Model

In this paper, the LedaFlow® 1D Slug Capturing model has been used to simulatethe field cases. The 1D model employs a three-fluid-nine-field modeling conceptto simulate the thermo- and hydrodynamics of the gas-oil-water three-phase flowin pipeline systems. In this approach, the various phases are assumed to flowin continuous zones and in the form of dispersed droplets within another zone. For instance, oil is transported in the form of continuous oil, oil droplets inthe water zone, and oil droplets in the gas zone. In a three-phase situation, the flow generally consists of three zones and nine fields. The momentum andenergy conservation equations are solved for each of the three zones, while themass equation is solved for all nine fields, yielding 15 conservation equationsaltogether.

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