1st FLNG Development in Mozambique: Real-Time Monitoring & Subsurface Insights Supporting Project Start-Up
Authors: Spagnuolo M. , Esperanca F. , Norelli V. , Boane M. , Balate B. , Parracello V. Parasiliti , Ursini F. , Furlani S. 
Published: October 2023

Abstract
During 2022, Mozambique successfully joined the list of Liquefied Natural Gas (LNG) producing countries with the launch of a Floating Liquefied Natural Gas (FLNG) development project. It consists of six deep-water development wells targeting a giant gas reservoir and feeding one FLNG unit with a nominal capacity of 3.4 MTPA of LNG production. The aim of this work is to share the subsurface work that has been performed to support the start-up operations, including real-time well monitoring and interesting reservoir insights.
The wells real-time monitoring was made possible thanks to the Eni Digital Oil Field (e-dof™) system, which allowed reservoir teams in Mozambique and Italy to access real-time data and efficiently follow-up offshore operations. During the start-up of the FLNG, the Inflow Performance Relationship (IPR) of each well over time was monitored by performing frequent Multi-Rate (MR) tests at the test separator, acquiring robust data for comparison with the Wet Gas Flow Meter (WGFM) installed in every well and the Real Time Virtual Flowing Metering (RTVFM), an online, in-house tool for real-time production estimation. Additionally, every build-up is being analyzed using Pressure Transient Analysis (PTA) to confirm reservoir properties and well damage. High-resolution bottomhole pressure gauges were also monitored to detect any dynamic interference within the wells and conduct Rate Transient Analysis (RTA), a powerful tool for flow regimes identification and contacted Gas Initially In Place (GIIP) estimation.
The reservoir is being efficiently monitored with the above-described workflow, confirming that wells deliverability meets production targets, and achieving optimum reservoir management of the field during start-up operations. In this framework, the e-dof™ system in place has allowed to close the spatial gap within the offshore operators and the working teams in Mozambique and in Italy.
Additionally, the study of wells dynamic interactions, coupled with standard and flowing material balance methods, made possible to infer about reservoir hydraulic communication and estimating the contacted GIIP. These estimates were found to be consistent with the 3D reservoir model, confirming its representativeness for long-term production forecasts.
Besides, the RTVFM, characterized by high reliability and integration within the e-dof™ system, proved to be a cost-effective solution to introduce measurement redundancy in the system, acting as a back-up of the WGFMs and avoiding the need for eventual expensive offshore interventions.
In this work, it is described how the start-up of Eni's first FLNG development in Mozambique is being managed from a reservoir perspective, using the most cutting-edge tools to guide the analysis and most importantly the real-time data availability thanks to the e-dof™ system in place. The integration of the deployed tools, which are being continuously improved, produced exciting achievements and interesting results, whose uncertainty will be reduced as more data will become available.