A Dynamic Simulation Study of an Extra-Heavy Oil Gathering System in the Orinoco Oil Belt

Abstract

The Orinoco Oil Belt (OOB) is the world's largest accumulation of heavy and extra-heavy oil with recoverable reserves of 513 billion barrels. It was divided into four production areas: Carabobo, Ayacucho, Junin and Boyaca. Based on that importance for the country's oil production, the use of dynamic flow simulators is becoming more important for the company when it comes to assess the development of such a huge oil deposit. Currently, in the Carabobo Area, there is a significant uncertainty about the transient behavior of multiphase fluids in the gathering systems, since all studies have been conducted using steady state models. Because of that, there is no a thorough knowledge where there are slug flow formations, the impact of adding new oil production to the current pipeline networks and the transient hydraulics behavior during start-up/shut-in of wells. This project aimed to build a dynamic simulation model, where several scenarios were established to study the impact on the current gathering system due to changes in flow patterns, additional oil and gas production, start-up/shut-in of wells. Results showed that the predominant patterns in the system are slug and stratified flows, being the critical area a 5.7 km pipeline at the end point of the gathering system, where there are considerable slug formations. Moreover, with the oil production growth estimated in the short term (2012-2013), the slug flow formations will be reduced slightly; therefore when wells are shut-in the difficulties to transport the fluids are increased considerably. Even though the dynamic simulator underpredicted pressure values compared to real data in approximately 25%, it is possible to use the program as a reference to conduct transient analysis with oil and gas from Cerro Negro Field. This dynamic simulation proved to be a useful tool to analyzed technical and operational problems in an extra-heavy oil field and for the current and future development of the OOB's vast reserves.