Real-Time Optimization of a Highly Complex, Integrated Gas System

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 150109, ’Successful Real-Time Optimization of a Highly Complex, Integrated Gas System: Intelligent Energy in the Real World,’ by Derek Gobel, SPE, Shell; Jan Briers and Frank De Boer, IPCOS; and Ron Cramer, SPE, Kok-Lam Lai, SPE, and Martijn Hooimeijer, SPE, Shell, prepared for the 2012 SPE Intelligent Energy International, Utrecht, the Netherlands, 27-29 March. The paper has not been peer reviewed. Real-time optimization (RTO) was used by Shell Malaysia E&P on the integrated gas-production system in Sarawak. Models for real-time monitoring and optimization of wells and facilities were implemented on a gas-production network spanning more than 100 wells on more than 40 platforms across several production-sharing contracts (PSCs). Digital technology enabled field-based data to be used to support decision making and led to actions that ensure that production is optimized continuously. Introduction Traditionally, aspects of gas-supply security relate to reservoir management, development planning, and sustaining plant availability and integrity. With increased computing capabilities, increased attention is given to noncapital-expense-intensive ways to provide additional smaller-scale improvements to the performance of an asset. Production-system optimization (PSO) falls into this category. The Sarawak asset has experimented with ways to improve continuous optimization of its production through model optimization. Implementation of a mixed-integer nonlinear programming model rendered valuable results for medium- and long-term planning. However, network complexity and the volume of required optimization calculations obviated application in the real-time domain. Subsequent unsuccessful approaches included use of rigorous process-engineering simulation and optimization tools linked to the data historian. Two commercial soft-ware packages were trialed, but neither produced results fast enough or was sustainable by local staff. Context The Sarawak integrated gas asset is in the South China Sea off the coast of Sarawak, Malaysia. It comprises three onshore liquefied-natural-gas (LNG) plants at the onshore LNG complex in Bintulu, four onshore customers and an LNG cargo-export facility, 50+ offshore hubs and jackets, 100+ wells, and numerous connecting pipelines. Sarawak is covered by five PSCs and has several active operators. The asset produces offshore natural gas of variable composition that is blended in the source-system pipelines and liquefied in the onshore LNG plants in Bintulu. Associated condensates are collected and processed in the Bintulu complex. Constraints in the system are physical, planning, and contractual/commercial in nature. Possible Optimization Approaches Financial—Impractical. This approach constitutes the monetary bottom line: total profit after royalty, tax, and interest. The revenue is generated from gas and condensate sales at the going rates minus taxes and the costs of investments and operations.