Hydraulics Analysis of the Heidrun Offshore Field

The present work investigates the ability of the available 1D multi-phase flow simulators MAST [1] and OLGA [2] to reproduce measured field data on the offshore Heidrun oil field located in the North Sea. The production is tied back from two subsea templates through two 5km long 10′ near horizontal pipelines and two ~400 m high risers to the Heidrun TLP. Several tests were conducted at different separator pressures (32–52 bara) and inlet oil flow rates (3000–4700 Sm³/d) by applying a gamma densitometer downstream the riser top, just upstream the separator. For the range of test conditions the reported flow regimes are wavy-stratified flow, hydrodynamic slugging and severe slugging. For the slug flow regimes the gamma densitometer traces are used to back-calculate the relevant slug characteristics, such as the slug void, the slug body and unit length, slug velocity and frequency. When slugging occurs, analysis of the data indicates that the aeration in the slug is fairly high, around 50%, indicating that the gas entrainment into the liquid slug plays an important role in determining the relevant features of the resulting slug flow regime. Detailed flow simulator analysis of the field data show that a one-dimensional description of these phenomena can lead to a fair agreement with the data provided that the adopted closure laws are appropriate for the physical problem under investigation.