Extending Field Life for Gas Reservoirs Through Facilities Optimization

Mion, F. S. (Sarawak Shell Berhad) | Schaapveld, M. (Sarawak Shell Berhad) | Zou, S. (Sarawak Shell Berhad) | Mahra, A. (Shell Projects & Technology) | Groote, G. A. (Shell Global Solutions International) | Moeleker, P. (Shell Global Solutions International)


Abstract Objectives/Scope

One of the main objectives of the wells, reservoir and facilities management (WRFM) is to reduce production decline caused by falling reservoir pressure and water breakthrough. Traditional WRFM efforts focus on well interventions; however, facilities optimization can also help to maintain production levels, as has been demonstrated in Shell's Sarawak gas asset in Malaysia, where various measures have led to a total of over 50 Bscf of additional gas production over a period of several years for investments less than $1 million per year.

Methods, Procedures, Process

The Sarawak asset is a complex production network of 14 producing gas fields with 3 manned offshore gas-processing hubs, 7 unmanned platforms and 3 subsea installations. The gas network is producing below its plateau production level. The below capacity production leads to slugging in pipeline-riser systems and wells and creates large liquid hold-ups in pipelines. Water production from wells is increasing. To maximize current production and extend production further into the future, a structured exercise to optimize the upstream facilities was started. Unnecessary pressure drops were eliminated, pigging procedures optimized, and slug and water control methodologies implemented.

Results, Observations, Conclusions

Any location where a pressure drop occurs in the process is a potential opportunity for optimization. Opportunities were found in inlet separators, at the compressor suction sides, water handling capacity and platform export locations.

A novel implementation led to a floating pipeline export pressure matching the pipeline operating pressure to maximize production.

Pigging with large liquid hold ups often incur production deferment by cutting production before pig launch or closing the slugcatcher inlet when the liquid comes in. Bypass pigging has been deployed in 7 production lines to fully eliminate deferment.

Shell Sarawak Berhad (SSB) has been making effective use of Shell's proprietary Smart Choke slug control technology to allow pipeline-riser systems to operate far below their minimum turndown rate. It has now become the first company to adopt the technology directly on a well head to lower the impact of slugging from a well.

Dynamic models of multiphase flow pipelines have been built to extend the production cut-off date by lowering the minimum operational flow rate through a combination of operational changes and novel technologies validated by field tests.

Novel/Additive Information

This paper demonstrates the production gains which can be achieved by doing a relatively small investment. The focus lies on facility optimization (part of WRFM) through a process of continuous improvement of proven technologies. A good example is increasing the operating envelope for Shell's Smart Choke slug control system from pipeline-riser systems to wells applications.