Qatargas Well Production Back Allocation Project - Methodology & System Requirements
Authors: Abdelmoula D. , Montiel Dunlop J. E. 
Published: December 2015

Abstract
The use of a Well Back Allocation process is crucial in the Oil and Gas industry to facilitate accurate allocation of actual production and injection volumes at every node of a production network. Production engineers frequently use back allocation to estimate actual production volumes from wells based on frequent well test data or theoretical calculations using well and reservoir characteristics. The accuracy and precision of well rates are key elements for volumetric inputs to reservoir simulations and management, well performance surveillance, flow assurance, and revenue to partners.
Qatargas operates three blocks of the North Field (NF), located in north of the State of Qatar, producing gas and associated condensate from nine offshore platforms to feed seven onshore LNG trains. The first block initiated operations in 1996 for Qatargas 1 asset, whilst blocks 2 & 3 associated to Qatargas 2 and Qatargas3 and Qatargas4 assets began in 2009, 2010 & 2011, respectively. An in-house Excel based tool was developed to account for the allocation process back to the wells for Qatargas 1 only, which was driven by a poor data acquisition methodology, lack of well testing validation process, valuable field streams and metering system and a time consuming process for validation which caused continuous manual interventions.
Since 2012, Qatargas moved away from this manual tool to an automated solution that provides high frequency data capture, proper well testing validation functionality, with auditable and accurate allocation process, and with better visualization and reporting capabilities. To support the business growth as well as to provide the required allocated data to respective shareholders and Qatargas management, Qatargas wanted to implement a "world class type" Well Production Back Allocation System (WBA), that integrates the 3 operating blocks with their respective allocation network attributes; to accurately reproduce the estimated production from every well in the production network and improve the overall data quality and information management processes. This new implementation has improved the monitoring and surveillance processes for wells & reservoir.
The new back allocation system was implemented in the Energy Component (EC) system, following the facilities heterogeneities and constraints, and implementing the required functionalities to facilitate engineers the accomplishment of the whole process, from data population, validation, modeling and final allocation from fiscal metering points back to wells. The system implementation was coordinated by Qatargas Hydrocarbon Information Management System (HIMS) group, and it was a major step that contributed to a very reliable wells production data and very good reservoir/well surveillance, management and field's production optimization.
This paper discusses the overall experience for Qatargas to define the new WBA system requirements and methodology, its interaction with HIMS team, the project phases covered and challenges encountered during the implementation.