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When designing deepwater wells with long or multiple pay zones, completion specialists face economic and technical problems whose solutions are often in conflict.Typically, these long pay zones include variations in fracture pressures, permeability, or other reservoir parameters. In trying to stimulate the entire length as one zone, it can be difficult to manage the many stimulation requirements, such as volume, rate, and pressure factors. The result can be poor reservoir coverage and uneconomic production. On the other hand, traditional multizone sandface completions can impair well economics because of the rig time required.The typical completion of a two-or three-zone conventional, 10,000-ft well takes 10 to 18 days, most of which is nonproductive time (NPT) spent tripping in and out of the well (Turner et al. 2007). For a typical five-zone well in Indonesia, the conventional completion cycle has been estimated at up to 30 days .To address the varied and frequently conflicting problems of completing long-or multiple-pay-zone wells, especially in deep water, a system has been designed by BJ Services for executing gravel-or frac-pack completions over long or multiple intervals in a single trip (Fig 1). Stimulating Multiple ZonesA reservoir with a large gross pay zone and numerous stress layers is difficult to complete and stimulate effectively as a single interval. Frac packs, in particular, require careful planning to avoid overstimulation, which can breach water zones, or understimulation, which can fail to achieve optimal wellbore-to-reservoir connectivity. Even ordinary gravel packs can be difficult and expensive to execute successfully in multilayer formations.In reservoirs such as these, the most effective treatment method is to isolate each zone being treated. This is traditionally done by perforating, stimulating, and isolating each zone individually, a time-consuming process with many trips in and out of the well to run and retrieve various tools.To minimize this NPT for tripping, the single-trip longand multiple-zone completion tool, called ComPlete MST, combines several traditional tools to enable full flexibility in sand-placement techniques. Thus, positive, selective isolation of all zones can be achieved during completion, stimulation, and production operations.By this combination of several tools into one, completion time and cost can be reduced by 20 to 60%, depending on well depth, water depth, and the number of zones being completed. Eliminating one-third of a typical completion schedule on a multizone well could save an operator from USD 750,000 to 2.5 million in total cost for this work, based on a USD 250,000 day-rate for the rig. That cost estimate is conservative. Deepwater rig rates have been running at approximately twice that figure in early 2009.In addition, the system' s capabilities for selective zonal treatment enable optimization of treatments for each zone and enhance the economics of completing marginal zones that might otherwise be bypassed.The technology for each zone comprises...
Reducing recurrent pipe trips offer significant time savings easily translating directly into improved well and/or project economic benefit. Utilizing a reliable multizone single trip method that reduces additional pipe trips compared to performing conventional stacked cased-hole Frac-Pack (FP) or High Rate Water Packs (HRWP) has a major impact on the overall completion costs associated with reservoirs containing multiple completion intervals. This multi-zone single trip system improves operational performance and stimulation effectiveness by incorporating an innovative service tool sealing mechanism with complete independent zonal isolation for each treatment interval. Additionally a selective zonal opening/closing tool offers an added degree of well performance control. This paper provides a summary of multizone single trip system introduction and utilization beginning in 2007 to Bekapai and Sisi Nubi field projects in Mahakam Delta offshore Indonesia for sand control in mutlilayer reservoirs. To date, a total of 74 zones with FP/HRWP's on 16 wells have been successfully installed. An average of 5.3 days completion installation time has been achieved on 13 wells with 3-6 zones at an average depth of 12,000 ft (3,657 m). This compares to a completion installation time of 20 days per typical 5 zone stacked FP/HRWP well. As a result of efficiencies gained utilizing multizone completion technology greater than 70% rig time reduction has been achieved with $US 30 million dollars savings on the project thus far. This paper will also present lessons learned, application concerns when considering multizone single trip as a completion option and challenges going forward to improve implementation of multizone completion technology.
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