Abstract

This paper shares RasGas Company Limited (RasGas) experience in developing and implementing a production optimisation technology for reservoir management, surveillance and production sustainability. RasGas has recently implemented the Production Optimisation, Management and Planning Tool (PROMPT) with the help of PETEX consultants. The tool was built by integrating the PETEX suite of software (PROSPER/GAP/RESOLVE/IFM/IVM). The entire production system was modeled from wellbore to slug-catcher and connected to a high frequency real-time database for real-time monitoring and system updates. The PROMPT system is model centric and relies on rigorous physics, while its strength relies on using multiple seamless automatic and manual workflows. Many key calculations take place automatically and continuously however, other central workflows rely on engineering judgment such as well models updates.

The PROMPT system has successfully demonstrated its reliability in supporting RasGas efforts to achieve long term production deliverability and secure RasGas' contractual Liquefied Natural Gas (LNG) demand by meeting the LNG production targets and maximising recovery. This is attained by producing the field/wells per the optimum depletion strategy while honoring facility constraints, system availability (well/platforms/pipeline, planned and unplanned downtime, etc.) and operational limits.

RasGas uses the PROMPT system to generate well production guidelines as per the optimum reservoir depletion strategy to meet short term production targets. The PROMPT platform is equipped with an optimizer "Excel Solver" where the desired depletion strategy is coded and implemented. This depletion strategy is translated to actuality by generating short-term production guidelines on a regular basis while honoring the production system constraints. PROMPT is effectively used for real time monitoring and compliance with production guidelines, such as monitoring deviations of daily production from pre-defined targets, and for making well rate adjustments during planned/unplanned shutdowns or increased demand. It gives the engineers the ability to test different well operating strategies in off-line simulation to fine-tune production guidelines to meet changing field conditions and enables effective data integration between RasGas engineers in the Sub-surface group with those in the Operations groups.

Introduction

RasGas Company Limited has been experiencing significant expansion of offshore production. RasGas is operating a lean gas condensate reservoir and is producing from different blocks and completions. Hence there has been a need to develop and implement a means of improving our ability to optimize the well stream composition mixing in order to increase the ultimate value of RasGas' sales stream of LNG and condensate, while proactively manage the reservoir depletion. It was recognized that a production optimization and surveillance system would help in generating specific production profiles to address short term production upsets or opportunities and effectively monitor deviations in daily production.1

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