The following are just my ideas related to natural gas development in Pennsylvania. To minimize problems with natural gas development, the citizens, communities, educators, and companies should consider working together and it may be advisable to implement the following:
1. Establish private well construction standards that include grouting annular spaces and initial water quality testing. This monitoring should include documenting static water level and direction of groundwater flow.
2. Requiring predrilling and post-drilling water testing of groundwater wells, springs, and surfacewater sources.
3. Royality owners with wells should consider replacing substandard wells with sanitary wells. If royality owners have old hand-dug wells, these wells should be abandon.
4. Royality owners should reach out to none royality owners and encourage them to get their wells tested.
5. Drilling and Exploration companies
a. Install at least one nested groundwater well within the general vicinity of the construction pad or establish additional regional monitoring sites to better understand the vertical extent of the freshwater aquifer. These wells should be fitted with a pressure transducer and the water pressure should be monitored during the drilling and fracing process.
The nested wells should be divided into zone - shallow groundwater consolidate formation (< 150 feet), moderately deep consolidated (150 - 400 feet), deep consolidated (400 to 600 feet), deep possible brine water (600 to 1500 feet), and if shallow gas is present from 1500 to 2500 feet.
b. In the production well - the drillers should install additional fresh water casing. The first freshwater casing should not extend more than 300 feet below ground - Typical depth of most private wells) and should not penetrate a shallow gas producing formation. The second freshwater (shallow gas) casing should extend from 300 feet to 800 feet or the maximum depth of private wells and community water supplies within 1 mile from the production well and this casing should not penetrate a shallow gas zone. If a shallow gas bearing zone is encountered, a separate casing would have to be installed. There are databases available to assist with this evaluation or it may be necessary to survey local well drillers and private well owners.
Note: It may be advisable to have a PA licensed geologist be part of the decision making regarding the extent and depth of the freshwater casing.
Note: Casings should be cemented to the surface. The revisions in the casing should include the installation of the 13 3/8 casing that is used for coal seams - even when coal is not present and this casing should be grouted to the surface.
Possible Casing Breakdown
1. 24 inch conductor casing - up to 60 feet.
2. 20 inch casing - up to 600 feet to 800 feet (i.e., freshwater interface) cemented to the surface * - If many of the surrounding private wells are shallow the well design may want to attempt to add a casing segment that has a maximum depth of 300 feet and then 600 feet.
3. 13 3/8 inch casing - up to 1000 feet cemented to the surface
4. 9 5/8 casing - seal off shallow gas - cemented to the surface
5. 5 1/2 casing - this should be cemented to within the 9 5/8 casing.
c. These decisions would be based on a combination of database searches, information from local drillers, information from surrounding private wells, and on-site water quality monitoring during drilling to document the variation in the freshwater chemistry and presence of shallow gas deposits.
d. At the production well - it appears that it may be necessary to improve the cementing process to make sure that the freshwater sections are properly cementing. I believe that limiting the vertical leg of each casing section and grouting segment will help and create multiple barriers in the system and conducting third party assessments of the cement seal are necessary.
In addition, the cement should be field tested. From experience with drilling in the consolidated formation in PA, it is possible that the minimum amount of cement required to fill the annulus may be 3 to 5 times the actual void volume. This would take into consideration loss of cement to the formation or fractured zones.
Limiting the vertical sections also limits the chance that shallow gas may be pushed by grouting into a shallow freshwater zone.
6. If PA levees a tax on natural gas - a portion of the funding should go to a program to replace substandard private wells, install water treatment for sites that have been impacted, and water systems for areas that have been impacted by natural gas drilling. The program could then take the legal action to recover from the companies- so each homeowner does not have to carry the financial burden.
7. Municipalites - should develop a private well construction and permitting ordinance and facilitate education and outreach in the community.
Just a few thoughts.
Brian Oram, Professional Geologist
B. F. Environmental Consultants
http://www.bfenvironmental.com
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