Changes

===Confirmation phase===

===Confirmation phase===

Once a basin containing a potential BCGA has been identified, the task becomes one of confirmation. Because all BCGAs are abnormally pressured, the principal task during this phase is the determination of reservoir pressure and the mechanism of abnormal pressure. Most basins do not have sufficient quantity or quality of pressure data for this determination. Therefore, a combination of attributes listed on Table 1 can provide compelling evidence for the presence of abnormal pressure and a BCGA. Pore pressure indicators such as pore fluid composition (gas with little or no producible water) in conjunction with porosity (<13%), permeability (<0.1 md), thermal maturation (>0.7% Ro) data, and sustained gas shows are very useful. In some cases, sonic velocity data have been used to indicate the presence of abnormal pressures.<ref name=Surdam_1997>Surdam, R. C., 1997, [http://archives.datapages.com/data/specpubs/mem67/ch17/ch17.htm A new paradigm for gas exploration in anomalously pressured "tight gas sands" in the Rocky Mountain Laramide basins], ''in'' R. C. Surdam, ed., Seals, traps, and the petroleum system: AAPG Memoir 67, p. 283-298.</ref> <ref name=Surdametal_1997>Surdam, R. C., Z. S. Jiao, and H. P. Heasler, 1997, [http://archives.datapages.com/data/specpubs/mem67/ch12/ch12.htm Anomalously pressured gas compartments in Cretaceous rocks of the Laramide basins of Wyoming: A new class of hydrocarbon accumulation], ''in'' R. C. Surdam, ed., Seals, traps, and the petroleum systems: AAPG Memoir 67, p. 199-222.</ref> <ref name=Surdametal_2000>Surdam, R. C., Z. S. Jiao, and N. K. Boyd III, 2000, Delineation of anomalous pressured gas accumulations in the Riverton Dome area, Wind River basin, Wyoming, ''in'' G. Winter, ed., Fifty-First Field Conference, Wyoming Geological Association, p. 121-148.</ref> <ref name=Surdametal_2001>Surdam, R. C., J. Robinson, Z. S. Jiao, and N. K. Boyd III, 2001, Delineation of Jonah field using seismic and sonic velocity interpretations, ''in'' D. S. Anderson, J. W. Robinson, J. E. Estes-Jackson, and E. B. Coalson, eds., Gas in the Rockies: Rocky Mountain Association of Geologists, p. 189-208.</ref>

Once a basin containing a potential BCGA has been identified, the task becomes one of confirmation. Because all BCGAs are abnormally pressured, the principal task during this phase is the determination of reservoir pressure and the mechanism of abnormal pressure. Most basins do not have sufficient quantity or quality of pressure data for this determination. Therefore, a combination of attributes listed on Table 1 can provide compelling evidence for the presence of abnormal pressure and a BCGA. Pore pressure indicators such as pore fluid composition (gas with little or no producible water) in conjunction with porosity (<13%), permeability (<0.1 md), thermal maturation (>0.7% Ro) data, and sustained gas shows are very useful. In some cases, sonic velocity data have been used to indicate the presence of abnormal pressures.<ref name=Surdam_1997>Surdam, R. C., 1997, [http://archives.datapages.com/data/specpubs/mem67/ch17/ch17.htm A new paradigm for gas exploration in anomalously pressured "tight gas sands" in the Rocky Mountain Laramide basins], ''in'' R. C. Surdam, ed., Seals, traps, and the petroleum system: [http://store.aapg.org/detail.aspx?id=749 AAPG Memoir 67], p. 283-298.</ref> <ref name=Surdametal_1997>Surdam, R. C., Z. S. Jiao, and H. P. Heasler, 1997, [http://archives.datapages.com/data/specpubs/mem67/ch12/ch12.htm Anomalously pressured gas compartments in Cretaceous rocks of the Laramide basins of Wyoming: A new class of hydrocarbon accumulation], ''in'' R. C. Surdam, ed., Seals, traps, and the petroleum systems: [http://store.aapg.org/detail.aspx?id=749 AAPG Memoir 67], p. 199-222.</ref> <ref name=Surdametal_2000>Surdam, R. C., Z. S. Jiao, and N. K. Boyd III, 2000, Delineation of anomalous pressured gas accumulations in the Riverton Dome area, Wind River basin, Wyoming, ''in'' G. Winter, ed., Fifty-First Field Conference, Wyoming Geological Association, p. 121-148.</ref> <ref name=Surdametal_2001>Surdam, R. C., J. Robinson, Z. S. Jiao, and N. K. Boyd III, 2001, Delineation of Jonah field using seismic and sonic velocity interpretations, ''in'' D. S. Anderson, J. W. Robinson, J. E. Estes-Jackson, and E. B. Coalson, eds., Gas in the Rockies: Rocky Mountain Association of Geologists, p. 189-208.</ref>

{| class = "wikitable"

{| class = "wikitable"