Abstract

The use of Drag Reduction Agents (DRA) is a frequently used practice in the pipeline industry for optimizing processes; the DRA could be used for flow increasing or pressure reduction depending on the specific requirements of each optimization process, however the DRA injection is limited by pipeline's flow patterns and the presence of shear stresses that could destroy partially or totally the DRA's Drag Reduction Effect. In those cases where shear stresses sources arise, like diameter changes, bends or loops, a partial DRA degradation is generated and the non-degraded DRA performance models should be adjusted.

This paper presents a DRA Degradation Model developed inside a Colombian Oil Pipeline Operator verified with field tests in pipelines where the DRA injection constitutes a normal operation mode that underwent structural modifications; these modifications generated shear stresses sources and the DRA's Drag Reduction Effect was affected, being necessary to predict this affectation that impacts the system performance and fix it.

This research lets the Colombian Oil Pipeline Operator to develop accurately the optimization processes using Drag Reduction Agents on pipelines with shear stresses sources without affecting their flow capacity nor overdosing DRA, as result the Company´s projects where made feasible and the return on invested became increased.

Introduction

Some of Colombian pipeline transportation systems have a particular characteristic: the DRA injection constitutes the standard and permanent operational mode; this is the case of the Eastern Valley Pipeline (EVP). The EVP is a facility that allows the evacuation of some of the major heavy oil fields developed in Colombia; the EVP was originally built as a 20 inch diameter with 120 km length pipeline allowing a maximum flow rate of 200,000 barrels per day (bpd) – 31,796.5 cubic meters per day (m3/d) without DRA dosing, due since 2006 the Colombian oil production has been increasing gradually it was necessary to increase the flow capacity of the system making obligatory the permanent DRA injection for reaching a maximum flow rate of 240,000 bpd (38,155.8 m3/d) at the beginning of 2014.

Regardless of the increase of the pipeline flow capacity it became not enough for evacuating the oil production volumes the forecast analysis held that the EVP should reach a flow rate capacity of more than 300,000 bpd (47,694.7 m3/d). Over this scenario the EVP owner company decided to make short-term structural modifications on the pipeline that let increase its flow capacity.

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