Gas-liquid flow in hilly-terrain pipelines: a summary of physical behavior and models

The gas-liquid flow in oil and gas transport pipelines over hilly-terrain is a very complex phenomenon.
Due to hilly-terrain effects, the steady state methods for calculation of flow behavior are not enough.
Reliable engineering prediction and analysis methods of this type of flow are compulsory for modern
oilfield projects. A summary oilfield observed features, experimental studies and modeling approaches
related to the gas-liquid flow in hilly-terrain pipelines are presented in this paper. Events like unexpected
slug flow, higher pressure drops and liquid blockage might arise during the pipeline operation.
Experiments and theoretical models describing this behavior are identified in the literature review. The
models included are: time-dependent hydrostatic balances with gravitational segregation, mixture and
two-fluid one-dimensional continuum models. These models are the base of well known commercial
computer codes such as OLGA and TACITE. The information condensed in this work is considered to be
of relevance for personnel responsible to conduct operations and analysis of gas-liquid flow exhibiting
the anomalous behavior associated with hilly-terrain pipelines.
Keywords: gas-liquid flow, hilly-terrain, pipeline, mathematical models