In the Appalachian Basin gas wells are air-drilled and a multi-zone well stimulation are the normal completions. The majority of these wells are logged with air in the hole after removing the fines from drilling using compressed air. The sandstones in the Devonian series of the Appalachian Basin are listed in Table 1. These are associated with thinly bedded laminated sand shale sequences causing the Resistivity log to be lower. Many producing gas zones may be defined as so-called low resistivity pays.

Table 1

After Laughrey and Harper7 , 1986, listing of gas well targets in Pennsylvania.

Devonian Riceville Formation  
Venango Group Gantz 
Fifty-Foot 
Thirty-Foot, Upper Nineveh 
Snee, Lower Nineveh 
Gordon Stray, Boulder 
Gordon, Third 
Fourth 
Fifth 
Fifth Stray 
Bayard 
Bayard Stray 
Elizabeth 
Chadadoin Formation Pink Rock 
Bradford Group First Warren 
Second Warren 
Third Warren 
Speechley Stray, Upper Speechley 
Speechley 
Tiona 
First Balltown 
Second Balltown 
Sheffield, Third Balltown 
First Bradford 
Second Bradford 
Third Bradford 
Kane 
Elk Group Haskill, Riley, Elk 
Benson, Humphrey 
Alexander 
Devonian Riceville Formation  
Venango Group Gantz 
Fifty-Foot 
Thirty-Foot, Upper Nineveh 
Snee, Lower Nineveh 
Gordon Stray, Boulder 
Gordon, Third 
Fourth 
Fifth 
Fifth Stray 
Bayard 
Bayard Stray 
Elizabeth 
Chadadoin Formation Pink Rock 
Bradford Group First Warren 
Second Warren 
Third Warren 
Speechley Stray, Upper Speechley 
Speechley 
Tiona 
First Balltown 
Second Balltown 
Sheffield, Third Balltown 
First Bradford 
Second Bradford 
Third Bradford 
Kane 
Elk Group Haskill, Riley, Elk 
Benson, Humphrey 
Alexander 

Normal logging programs do not respond properly to thin or very thin pay zones which will be averaged with surrounding shales. This log response can cause pay zones to be overlooked as stimulation candidates. Information can be found from openhole logs in air filled holes, using a different methodology, to more accurately determine producing gas zones.

Appalachian Basin gas zones of the Upper Devonian section will be analyzed. A strategy will be recommended to help determine which zone(s) contain producible gas reserves or may not be worthy of hydraulic fracturing treatments. These decisions could have significant economic implications for operators. Appalachian Basin log examples, stimulation design and production response will be included as part of this investigation.

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