Optimization of Riser Design and Drill Centers With a Coupled Reservoir and Facility Network Model for Deepwater Agbami
- Gene M. Narahara (Chevron Energy Technology Co.) | John A. Holbrook (Chevron Corp.) | Mack E. Shippen (Schlumberger) | Alpay Erkal (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- August 2006
- Document Type
- Journal Paper
- 402 - 410
- 2006. Society of Petroleum Engineers
- 4.1.5 Processing Equipment, 5.6.4 Drillstem/Well Testing, 3.1 Artificial Lift Systems, 4.1.1 Process Simulation, 5.1.5 Geologic Modeling, 5.4.2 Gas Injection Methods, 5.5.11 Formation Testing (e.g., Wireline, LWD), 4.2.4 Risers, 1.6 Drilling Operations, 4.2 Pipelines, Flowlines and Risers, 4.3 Flow Assurance, 2.4.3 Sand/Solids Control, 4.5 Offshore Facilities and Subsea Systems, 3.1.6 Gas Lift, 5.3.2 Multiphase Flow, 5.5 Reservoir Simulation, 2.4.6 Frac and Pack, 2.4.5 Gravel pack design & evaluation, 4.1.2 Separation and Treating
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The use of multiple wells connected at a subsea manifold provides the opportunity to reduce the number of risers and capital expense. The problem is the proper modeling of the reservoir well flow coupled with the combined flow into the facility network (i.e., manifolds, flowlines, and risers), which is necessary to prevent underdesign, resulting in flow-rate bottlenecks, or overdesign, resulting in extra expenditures. This paper presents a tool and methodology for better modeling of the well-to-riser flow and the optimization of riser count and configuration.
Although reservoir models coupled with facility networks is not new, software enhancements provided the capability of including operation logic that could duplicate operations in the field. The reservoir model coupled with the facility network provided more reasonable and accurate modeling of multiphase rates and pressures as wells were combined into a single riser.
To optimize the riser count, operation logic was applied to maximize rate in the riser at all times against the erosional-velocity limit. This in turn prevented overdesigning by placing more risers than needed to obtain the field-facility capacities.
The use of the coupled model and operation logic allowed the optimization of the riser count for any particular reservoir model. The optimum riser count was then determined for 3 earth (geologic) models.
The Agbami structure is a northwest/southeast-trending four-way-closure anticline and is located on the Niger delta front approximately 65 miles offshore Nigeria in the Gulf of Guinea (see map in Fig. 1). The structure spans an area of 45,000 acres at spill point and is located in 4,800 ft of water. The Agbami No. 1 discovery well was drilled in late 1998. The appraisal program was completed in 2001 and included five wells and one sidetrack drilled on the structure, with each encountering oil pay. These five wells and a sidetrack penetrated an average of approximately 350 ft of oil.
One of the key outcomes of the previous work phase (Phase 2) was the selection of the facilities design. The Agbami team adopted an all-subsea field-development scheme. This scheme involved modeling all field-production and injection-fluid flow through numerous subsea manifolds.
One of the important objectives in the current phase (Phase 3) of development was to determine the optimum number and locations of the production risers. The problem was determining how to properly model the reservoir and facility design such that the impact of riser count can be properly quantified. The determination of this impact was necessary to make a quality decision on the riser count and configuration.
|File Size||3 MB||Number of Pages||9|
Ghorayeb, K., Holmes, J., Torrens, R., and Grewal, B. 2003. A General Purpose Controller forCoupling Multiple Reservoir Simulations and Surface Facility Networks.Paper SPE 79702 presented at the SPE Reservoir Simulation Symposium, Houston,3-5 February.
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