CT Fracturing Method With Downhole Mixing Designed To Optimize Shale Completions
- Fraser McNeil (Halliburton)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- October 2011
- Document Type
- Journal Paper
- 28 - 31
- 2011. 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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The challenge in recovering hydrocarbons from shale is the low permeability, making cost-effective fracture stimulation treatments essential to economic production. Technology advances and improved operational efficiency have made shale production around the globe far more viable. However, while the wells being completed are proving reasonably economic, are they achieving their full potential?
The most common method of multistage hydraulic fracturing in horizontal completions in the United States is the plug-and-perforate technique. This stems from the successful work performed in the Barnett Shale, starting in the late 1990s, where production results were deemed economic and the completion technique advanced toward a factory approach to improve operational efficiency. This technique involves running in hole with conventional guns to perforate multiple clusters in the first treatment interval, pulling out of hole, pumping a high-rate stimulation treatment, pumping a plug down to isolate the interval, then repeating until all intervals are stimulated. The reality of the plug-and-perforate process is that the efficiencies are achieved at the cost of stimulation effectiveness (reservoir access) and accompanied by a high risk of excessive downtime. Some of these disadvantages are:
- Uncertainty of the number of fractures initiated within the clusters of perforations.
- Uncertainty of proppant distribution along perforation clusters and across multiple fractures within the clusters, leading to potentially poor long-term production performance.
- Underdesigned proppant schedules, intended to avoid screenout but that may not achieve adequate fracture conductivity.
- Overflushing of the near-wellbore region, as a result of using pumpdown plugs.
- The need to displace the entire casing volume before changes on surface will affect the treatment at the perforations.
- Significant cost and time required to recover from unplanned events, such as screenout or stuck plugs.
- Increased environmental footprint, personnel, and hydraulic horsepower required on location.
- Relatively long completion time to bring the well on production
- Added safety concern and potential downtime, both of which are inherent in running guns and pumping plugs.
- Near-wellbore damage that can result from perforating conventionally (with explosive shaped charges).
To address deficiencies associated with the plug-and-perforate method, a fracturing technique deployed by means of coiled tubing (CT) has been developed by Halliburton that maximizes stimulated contact area (reservoir access) and reduces the risk of excessive downtime, thus improving operational efficiency.
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