In Halliburton’s second unconventional resources blog article, the topic is about which is the best completion strategy, plug-n-perf or frac valves? An effective completions strategy can help to reduce costs while increasing production for operators. There is no better comparison than that of real examples provided in this next blog.
The authors analyze this question in SPE 148642 entitled Comparison of Frac Values vs. Plug-and-Perf Completion in the Oil Segment of the Eagle Ford Shale: A Case Study. Authors Neil A Stegent, Pinnacle – A Halliburton Service and Kip Ferguson, Magnum Hunter Resources, Corp, and Jon Spencer, Tracerco presented the paper at the 2011 CSUG/SPE Unconventional Resources Conference, November 15-17, 2011, Calgary, Alberta, Canada.
Can you tell me the purpose behind the study?
The primary purpose of the comparative completions (frac valves vs. plug-and-perf) was to determine if there was difference in the production (both initial and 180 day) between the two completions. We were also looking to see if we could get a better completion efficiency from the frac valve completion (more frac jobs done in less time).
Where there any surprises in the study?
Yes. The frac valve completion actually took longer to complete than the plug-and-perf due to near-wellbore restrictions (tortuosity) which we did not anticipate. We didn’t have any issues getting the ball-drop valves open but establishing a good injection rate was sometimes a challenge. We later solved this by pumping Acid Soluble Cement (ASC) in the lateral section of the wellbore. ASC is 80-90% acid soluble while conventional cements tend to be about 10-15% acid soluble. It made a huge difference.
We did not see any difference in production between the two completions (frac valves vs. plug-and-perf). We pumped an oil-soluble tracer on all the frac stages and then analyze the hydrocarbon portion of the flowback. The analysis delivers a pseudo-production log over time and there was no difference between the completion methods. We also used downhole microseismic mapping technology and did not see any noticeable difference in fracture complexity generation between the single entry point (frac valves) and the multiple entry points (plug-and-perf). We did see that the placement of the lateral had an impact with regards to fracture growth. Fracs would tend to go downward toward the Buda in the intervals where the lateral was below the Eagle Ford target interval and they grew upward (toward the Austin Chalk) if the lateral was above the target interval. It seems there is about a 20-25 foot window in the target zone that the lateral needs to be placed in order to optimize the fracture coverage of the Eagle Ford.
What are the next steps?
Improve on the time it takes to complete the well and increase the stage count per 1000 ft. We would like to know we are creating more fractures across a given length of lateral and be able to do that both efficiently and economically. Multiple entry point frac valves may be the solution.
For more information about horizontal completions, please visit our website.
Neil is a Technology Manager for Pinnacle (a Halliburton service) in Houston, Texas. He has worked over 30 years for Halliburton in various roles including engineering, customer sales, management, and marketing. He has a vast amount of field experience which involves the implementation of theory into practice – real-time fracture evaluation, pre-frac and post-frac diagnostics, fracture production evaluation, and completion optimization are his expertise. He has worked in numerous tight gas basins across North America, and has worked globally to provide solutions and commercialize new technologies. Neil has taught numerous courses in completion optimization and has worked most of his career focused on Fracture Stimulation and Completions of tight gas reservoirs. He has been working with the Pinnacle group for the last 2 years and is involved with integrating the frac mapping technologies with real-time on-site fracture decision making and frac design alteration.
For more information, please feel free to contact me.