Restimulation of Wells using Biodegradable Particulates as Temporary Diverting Agents
- David Blair Allison (Halliburton Energy Services Group) | Shawn S. Curry (Halliburton) | Bradley Leon Todd (Halliburton Energy Services Group)
- Document ID
- Society of Petroleum Engineers
- Canadian Unconventional Resources Conference, 15-17 November, Calgary, Alberta, Canada
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 3.2.6 Produced Water Management, 2.2.3 Fluid Loss Control, 2.2.2 Perforating, 1.6.6 Directional Drilling, 5.8.2 Shale Gas, 4.2.3 Materials and Corrosion, 4.3.4 Scale, 4.1.2 Separation and Treating, 2.5.2 Fracturing Materials (Fluids, Proppant), 3 Production and Well Operations, 1.14 Casing and Cementing, 4.1.5 Processing Equipment, 2 Well Completion, 1.3.3 Wellhead integrity, 3.3.1 Production Logging, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 2.4.3 Sand/Solids Control, 1.2.3 Rock properties, 1.6 Drilling Operations, 1.10 Drilling Equipment
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During the life of producing wells, there comes a time when the well approaches its economic viability as a producing well. If the reservoir potential is sufficient to support the expenditure, many wells are candidates for recompletion, reperforation, or restimulation. This type of focus on the Barnett shale began in the late 1990s. Drilling activity dramatically increased during the ensuing years and now there are more than 14,000 wells that have been drilled, most of which are producing wells. A lot of these wells are potential candidates for restimulation (refrac) because their production rates have declined but still have significant reservoir potential. The completion techniques deployed in the Barnett evolved over time to where many wells have dozensof perforation clusters and hundreds of individual perforations. Generally, refracsare ineffectual unless the perforations can be temporarily isolated so that the energy of the subsequent fracturing treatment can be focused on individual portions of the reservoir. Additionally,refrac candidate wells often contain challenging wellbore environments that further complicate the ability to successfully refrac the wells. The use of biodegradable particulates to facilitate the temporary diversion and concentration of frac energy has increased the success of restimulation.
This paper discusses the recent development of techniques and materials being used in refracturing operations. Included are discussions of laboratory results of new and novel materials, along with case histories of refrac wells demonstrating application of such materials and techniques.
At some point during the life of a producing well that has been stimulated,it will be evaluated for a restimulation. Because a majority of wells in North America require an original fracturing stimulation treatment to be an economic success, the necessary restimulation is a secondary (or tertiary) fracturing treatment commonly known as a refrac. The initial investment to drill, complete, and hook up a well to a sales line is significant, and logic dictates that a proper evaluation should be undertaken to determine if a refrac is plausible on candidate wells. Refracs are enticing compared to the outlay in capital and the process to drill a replacement (new) well. The refrac greatly reduces the time it takes for production flow to increase, thus having a significant impact on the net present-value calculations. It is not unusual for a refrac to be an order of magnitude less expensive than the alternative of drilling and completing a new well.
The discussion of how, why, and when to refrac vertical well completions has been ongoing for decades (Coulter and Menzie 1973) and has been reasonably well-documented for vertical,biwing fractures.Recently, the industry has focused on burgeoning shale plays,such as the Barnett shale. The origins of Barnett production can be traced back to 1979, but many do not consider the true development of this resource to have begun until the early 2000s (Grieseret al. 2006). The evolving completion techniques associated with horizontal drilling, multiple original fracturing treatments, and perforating schemes that made the Barnett such a prolific producing reservoir have dictated an evolution in the refrac process. Operators have evolved drilling and completion processes from a traditional biwing-fracture approach to the manufacturing-like process of perforate, stimulate, and isolate (PSI). Each well was a "real-time laboratory?? where new techniques, process improvements, and material progression took place. Feedback on the success of the improvement was determined by initial and sustained
production results balanced against the cost to accomplish the process. Possibly all of these wells in the evolution can be considered candidates for refracs once they reach threshold production criteria, as determined by the operator. Even wells completed with the PSI process may be candidates, should their production fall below the operator's threshold criteria. (See "Candidate Selection??section for additional discussion on key characteristics that can guide candidate-selection criteria.)
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