Sunday, February 7, 2010

Recommended Natural Gas Well Construction Techniques for Pennsylvania

Because of the recent interest in the Marcellus Shale in PA, there has been a significant increase in drilling of deep natural gas production wells.  One of the primary concerns or issues is Pennsylvania, would be the potential for these wells to impact surrounding freshwater wells.  Since most of these freshwater wells are wells that are classified as private or unregulated wells and these wells are typically constructed with no minimal construction standard, a primary concern for developing the Marcellus Shale would be to throughly document the construction characteristics, water level, and quality of these wells.   Since it may not be easy to modifiy the existing wells, the primary recommendations are as follows:

1. A detailed well inventory should be completed and it could be supplemented by the PAGWIS database.
2. The private well data that is critical would be the well location (GPS- using same standard or better and datum) that is being used by the Department of Conservation and Natural Resources - Web Driller Website.  The following is the information that is required for the on-line well submission form-

Driller Well ID – A unique identification number assigned by the driller. It can be any unique combination up to 15 characters long. Once the report is submitted, this number cannot be changed.

Type of Activity – The subject of the driller’s report. “New Well” is the default activity. Click on the dropdown menu to select something other than “New Well.” When another option is chosen, a new box opens up: “Original Well By.” Select the appropriate button (either “Current Driller” or “Another Driller”). If “Another Driller” is selected, an additional box appears asking for the name of the “Original Driller.” If the original driller is not known, indicate “unknown.” If “Well Abandonment” is chosen as the Type of Activity, an additional box “Reason for Abandonment” appears. Select the reason from the dropdown menu.

Date Drilled – Click the date on the calendar.

Drilling Method – Select from the dropdown menu.

Owner – This can be a business entity or a person.

Coordinate Method – The method of determining the well’s location coordinates. Choose from the dropdown menu. When using a hand-held GPS for determining the coordinates, choose “GPS – Global Positioning System.”

Location Type – The type of coordinate system used to locate the well. Choose between “Latitude/Longitude” and “UTM.” Latitude/longitude is the most common method. UTM stands for the Universal Transverse Mercator global coordinate system that is based in meters. If UTM is selected, the latitude and longitude boxes change to the required fields of “UTM Northing” and “UTM Easting.”

Latitude and Longitude – Values of the coordinates of the well location. If using a GPS, set your GPS units to “decimal degrees,” and your datum to North American Datum (NAD) 1983. Latitude and longitude must be reported in decimal degrees in this format: xx.xxxxx for latitude and (negative) -xx.xxxxx for longitude. This format should be set on your GPS as decimal degrees. To convert “degrees and decimal minutes” to “decimal degrees,” divide the minutes by 60 and add this number to the degrees. (There are 60 minutes in a degree and 60 seconds in a minute. There are 3,600 seconds in a degree.)

3.  The size of the pump should be documented, drillers log reviewed, and water level measured.
4. Regarding baseline monitoring, the monitoring should include parameters that can be related to the drinking water standard, parameters characteristic of saline/brine water, parameters that may be related to existing sources of contamination, and constituents related to the mixture and blend of fracing and development chemicals used on-site.
5. Based on a review of the private well logs and water levels, it may be advisable to use a multiple freshwater casing approach.  This multiple casing approach would add additional casing to provide a second barrier between the shallow and deeper portions of the freshwater aquifer.  For most of NEPA, it would be likely that the first cemented casement should probably be at a depth of 250 to 300 feet, the next casement at about 700 to 800 feet, next casement maybe 1500 to 2000 feet, and finally something at about  2500 to 3000 feet.  This would properly seal off freshwater, saline water, and most shallow gas.    In addition, the inner most cement should not just extend 500 to 1000 feet above the kickoff point, but extend up into the protective casing or better to the surface.
6. From the results of the background analysis, the results should not only be used to establish a formal baseline, but used by the community to identify areas were the wells should be improved or upgraded.  The solution to a contaminated private well may not be simply adding treatment, but modifying the well to prevent the contamination from occurring or abandoning the well and drilling a new sanitary well.
7. Local agencies should implement a Water Well Construction and Siting Ordinance and require existing wells that are contaminate to be properly repaired and upgraded.
Just a few thoughts
Brian Oram, PG
B.F. Environmental Consultants Inc.
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