“A key to increasing US natural gas production has been advances in hydraulic fracturing technologies, enabling exploitation of the country’s tight gas and shale gas resources,” Doug Lehr with Baker Hughes said in a presentation at the 2011 SPE/ICOTA Coiled Tubing and Well Intervention Conference and Exhibition last week in The Woodlands. “Plug and perf technologies will therefore play a significant role.” To achieve the highest probability of mechanical success, it is important to examine best practices associated with composite bridge plug technology, he said.
A best practice as defined by Mr Lehr is a process or method that, when applied to a customary or routine task, results in the highest probability of success.
“In 2010, between 100,000 and 140,000 composite plugs (CPs) were run in the US,” Mr Lehr said. The CPs are made up of composite materials, with a small percentage of components consisting of cast iron, ceramics, brass and rubber, and they are typically available in sizes ranging from 2 7/8 in. to 7 in.
Mr Lehr presented the method used to derive best practices to be applied to the use of CPs and the results of a survey taken among operators. The methodology consisted of soliciting feedback from engineers with extensive experience as end users of CPs in the US, soliciting feedback from service companies on specific topics and using collective knowledge of multizone stimulation with CPs.
The survey was sent to 54 engineers, and 28 responses – representing 13 companies heavily focused on exploitation of unconventional gas in North America – were received. Service company feedback was collected on topics such as plug running speed, perforating distance between the plug and guns and plug removal.
“91% of survey respondents believe that mechanical success with CPs can be improved with a set of best practices,” Mr Lehr said. “71% of survey respondents said that they already use best practices in some way. These respondents were referring to planning, procedures, preparation, performance and product selection.”
The three most important advantages of CPs as ranked by the people surveyed were ease of removal using either coiled tubing or jointed pipe, reliability and consistency in performance and cost effectiveness. Other advantages cited were general availability, pump-down capability, cuttings removal and the availability of flow-through models.
There are areas with respect to CPs that those surveyed felt could be improved through the use of best practices. Those areas include electric line setting tool maintenance and reliability; determining the CP pressure requirement; pre-job checks for electric line tools and CPs; guidelines for running gauge rings; guidelines for determining perforating distance above CPs; selection criteria for positive displacement motors for milling or drilling of CPs; and mills and bit design for minimizing the size of CP cuttings during removal.
For more information, please see SPE 142744, “Best Practices for Multizone Stimulation Using Composite Plugs,” by D.J. Lehr and D.D. Cramer.