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June 2012
Volume 31 |
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Is the Solution for the "Fracking Mess" Dilution or Concentration 1?
By Don Keer, PE, and Robert C. McCue, PE
MDCSystems® Consulting Engineers
MDCSystems® Consulting Engineers
Waste Reduction and Pollution Minimization
The Problem
The recovery of natural gas from tight rock formations, such as shale, has presented the oil and gas industry with serious environmental challenges. Quite possibly the most significant issue is the use and treatment of the large volumes of water required to fracture a gas well to make the production volumes viable. In tight rock formations the shale substrate porosity is not significant enough to allow large volumes of natural gas to flow into a relatively small diameter well bore. The geology requires pressurized water to create fractures in the shale which are intended to extend hundreds of feet away from the well bore itself.
The recovery of natural gas from tight rock formations, such as shale, has presented the oil and gas industry with serious environmental challenges. Quite possibly the most significant issue is the use and treatment of the large volumes of water required to fracture a gas well to make the production volumes viable. In tight rock formations the shale substrate porosity is not significant enough to allow large volumes of natural gas to flow into a relatively small diameter well bore. The geology requires pressurized water to create fractures in the shale which are intended to extend hundreds of feet away from the well bore itself.
During the fracture of the shale (the “fracking” process) the drillers add chemicals to weaken the shale formation, reduce the friction of the water entering the rock, increase the downhole pressures and initiate the required fractures. Once the fractures open, a “propant” such as sand is pushed into the formation with water to keep the fractures open, creating a significantly greater flow surface for hydrocarbon production. In many instances, but particularly in the case of Marcellus shale gas, the only way to make a well viable is to frack it.
The amount of water necessary for each well can vary but is generally in the 2 million to 9 million gallon range. Each well site may support up to twenty individual well bores. After the fracking process is complete, 10% to 50% of the water used flows back to the surface and is known as “flowback”. Most of the flowback occurs during the first 10 days after completion of the fracking process, but flowback may continue for 60 days or more. During this time the well also produces small amounts of natural gas and other volatile organics which have traditionally been either flared or vented.
The amount of water necessary for each well can vary but is generally in the 2 million to 9 million gallon range. Each well site may support up to twenty individual well bores. After the fracking process is complete, 10% to 50% of the water used flows back to the surface and is known as “flowback”. Most of the flowback occurs during the first 10 days after completion of the fracking process, but flowback may continue for 60 days or more. During this time the well also produces small amounts of natural gas and other volatile organics which have traditionally been either flared or vented.
Green Buildings: Measure and Verify Performance
By E. Mitchell Swann, PE, LEED AP
MDCSystems® Consulting Engineer
By E. Mitchell Swann, PE, LEED AP
MDCSystems® Consulting Engineer
One of the big outgrowths of the green building movement is a new focus on actual building performance. This isn’t just the individualized performance of a singular system at a point in time (“the lights come on when you flip the switch - check”), but the overall performance of the whole building over some extended period of time (annual energy consumption per square foot of building). Green buildings have touted their superior energy or resource efficiency and while there have been some success, there have also been some less than tremendous performances by allegedly high performance buildings. As a result – and in this engineer’s opinion, a logical outcome – there has been a movement towards adding a “measurement and verification” (M&V) requirement to the ratings systems. Taking the two ‘’biggest dogs in the park,” the USGBC’s LEED system and the EPA’s Energy Star program, there are two slightly differing frameworks.
LEED requires a performance target that is better than what would be predicted using “normative” energy conservation standards (i.e. ASHRAE Std. 90.1) and it requires that an energy model be developed for the project. After construction, the M&V mandate requires that the owner submit annual energy bills (for 5 years) to the USGBC and to compare the actual usage to the modeled usage. In short, it is a check to see if you are doing what you said you would do. This is valuable!
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