Tool Enables One-Trip Completions in Multiple Deepwater Pay Intervals
- Jed Landry (BJ Services) | Stephanie Weiss (BJ Services)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- May 2009
- Document Type
- Journal Paper
- 28 - 30
- 2009. Copyright is retained by the author. This document is distributed by SPE with the permission of the author. Contact the author for permission to use material from this document.
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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 (Delattre et al. 2008).
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 Zones
A 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 long- and 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.
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