Increasing Production by Applying Field-proven Active Slug Suppression Technology

In mature fields, pipelines are often oversized for their operating conditions. This is because their design was primarily based on the early and plateau production and less on late life production. This oversizing may lead to slugging issues, whereby flow fluctuations cause liquid handling problems in the receiving facilities, which can lead to system trips. The purpose of this paper is to describe the workflow, which includes identifying the operational problems, designing the slug control system, and commissioning and monitoring of the control system. The Smart Choke developed by Shell1 is able to mitigate the effects of slugs and has now been installed at several locations worldwide. It is an active slug control system: the topside choke acts only if surges are observed, reducing the peak flow rate into the separator. Between slugs, the choke valve opens, reducing the imposed backpressure. Since flow fluctuations are reduced, operation is again possible without risking excessive separator liquid levels. The workflow consists of the following steps: (i) If slugging leads to production deferment or to operational problems, a feasibility study is done to assess the benefits of installing a Smart Choke. To this end, the key design and production data are collected in a single data sheet that is analyzed by flow assurance experts, (ii) The analysis may include using dynamic multiphase flow models. The models are used to reproduce the slugging behaviour as seen in the field and to assess the adequacy of the Smart Choke. (iii) If the results indicate a positive outlook, and the asset agrees, the implementation needs to be planned and executed. This requires further data gathering on the choke actuator, the pipework for a suitable transducer location, and the platform control system. (iv) The flow assurance and process control experts go to the platform to help commissioning the Smart Choke, which includes tuning of the controller parameters. (v) Once in operation the Smart Choke performance is monitored remotely by the experts using PI Process Book. In addition to pipeline systems already in operation, implementation of a Smart Choke can also be considered for pipeline projects in the development phase. When in the hydraulic assessment risks are identified with respect to slugging, the decision for full implementation can be postponed, but the production system is made "Smart Choke ready" by reservation of weight/space at a pipe segment at the outlet of the pipeline upstream of the separator. When slugging occurs in a later phase of the field life the spool piece can be replaced by the required Smart Choke hardware without doing any hot work.

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Extending Field Life for Gas Reservoirs Through Facilities Optimization

Mion

Schaapveld

Zou

et al. 2016

Day 3 Wed, November 16, 2016

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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.

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Increasing Production by Applying Field-proven Active Slug Suppression Technology

Cited by 4 publications

References 5 publications

Progress and outlook on severe slugging mitigation techniques for offshore hydrocarbon production: A systematic review

Progress and outlook on severe slugging mitigation techniques for offshore hydrocarbon production: A systematic review

Lean Workflow for Selection and Implementation of Smart Choke Control to Resolve Slugging in Operations

Extending Field Life for Gas Reservoirs Through Facilities Optimization

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