Changes

|+ {{table number|1}}Problems and approaches to [[evaluating tight gas reservoirs]]

|+ {{table number|1}}Problems and approaches to [[evaluating tight gas reservoirs]]

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! Reservoir Formation Problem

! Reservoir Formation Problem || Approach

! Approach

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| Reservoir performance is controlled by sedimentary facies, lithology and/or geometry

| Reservoir performance is controlled by sedimentary facies, lithology and/or geometry || Determine sedimentary characteristics and origin of facies through [[core description]] and construct predictive models for lateral variability and heterogeneity of reservoir units

| Determine sedimentary characteristics and origin of facies through [[core description]] and construct predictive models for lateral variability and heterogeneity of reservoir units

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| Reservoir performance and formation permeabilities are negatively impacted by presence of detrital or authigenic clays (very common)

| Reservoir performance and formation permeabilities are negatively impacted by presence of detrital or authigenic clays (very common) || Identify and map reservoir facies with the least detrital clay content; avoid treatment of formation by acidization or injection of any fluids; use oil-based muds; enhance recovery through artificial fracturing of the formation<ref name=pt06r93>Moslow, T. F., Tillman, R. W., 1986, [http://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0250/0271.htm Sedimentary facies and reservoir characteristics of Frontier Formation sandstones, southwestern Wyoming], in Spencer, C. W., Mast, R. F., eds., Geology of Tight Gas Reservoirs: AAPG Studies in Geology Series 24, p. 271–295.</ref>

| Identify and map reservoir facies with the least detrital clay content; avoid treatment of formation by acidization or injection of any fluids; use oil-based muds; enhance recovery through artificial fracturing of the formation<ref name=pt06r93>Moslow, T. F., Tillman, R. W., 1986, [http://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0250/0271.htm Sedimentary facies and reservoir characteristics of Frontier Formation sandstones, southwestern Wyoming], in Spencer, C. W., Mast, R. F., eds., Geology of Tight Gas Reservoirs: AAPG Studies in Geology Series 24, p. 271–295.</ref>

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| Reservoir performance is dictated by origin and distribution of natural fractures

| Reservoir performance is dictated by origin and distribution of natural fractures || Evaluate the relationship between fracture occurrence and lithology<ref name=pt06r100>Pitman, J. K., Sprunt, E. S., 1986, [http://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0200/0221.htm Origin and distribution of fractures in Lower Tertiary and Upper Cretaceous rocks, Piceance basin, Colorado, and their relation to the occurrence of hydrocarbons] in Spencer, C. W., Mast, R. F., eds., Geology of Tight Gas Reservoirs: AAPG Studies in Geology Series 24, p. 221–234.</ref>

| Evaluate the relationship between fracture occurrence and lithology<ref name=pt06r100>Pitman, J. K., Sprunt, E. S., 1986, [http://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0200/0221.htm Origin and distribution of fractures in Lower Tertiary and Upper Cretaceous rocks, Piceance basin, Colorado, and their relation to the occurrence of hydrocarbons] in Spencer, C. W., Mast, R. F., eds., Geology of Tight Gas Reservoirs: AAPG Studies in Geology Series 24, p. 221–234.</ref>

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| Fracture mineralization impacts reservoir performance.

| Fracture mineralization impacts reservoir performance. || Determine the nature, origin, and timing of mineralization through petrographical and stable isotope techniques<ref name=pt06r100 />

| Determine the nature, origin, and timing of mineralization through petrographical and stable isotope techniques<ref name=pt06r100 />

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| [[Porosity]] and permeability trends are controlled by clay diagenesis or secondary cements

| [[Porosity]] and permeability trends are controlled by clay diagenesis or secondary cements || Determine the petrological and mineralogical history of reservoir facies; identify and map “diagenetic facies” relative to sedimentary facies

| Determine the petrological and mineralogical history of reservoir facies; identify and map “diagenetic facies” relative to sedimentary facies

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| Reservoir gas accumulations lack a floored gas-water contact

| Reservoir gas accumulations lack a floored gas-water contact || Map structural, isothermal, and pressure gradient contours that are likely coincident with boundaries of the gas envelope<ref name=pt06r113>Rose, P. R., Everett, J. R., Merin, I. A., 1986, [http://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0100/0111.htm Potential basin-centered gas accumulation in Cretaceous Trinidad Sandstone, Raton Basin, Colorado] in Spencer, C. W., Mast, R. F., eds., Geology of Tight Gas Reservoirs: AAPG Studies in Geology Series 24, p. 111–128.</ref>

| Map structural, isothermal, and pressure gradient contours that are likely coincident with boundaries of the gas envelope<ref name=pt06r113>Rose, P. R., Everett, J. R., Merin, I. A., 1986, [http://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0100/0111.htm Potential basin-centered gas accumulation in Cretaceous Trinidad Sandstone, Raton Basin, Colorado] in Spencer, C. W., Mast, R. F., eds., Geology of Tight Gas Reservoirs: AAPG Studies in Geology Series 24, p. 111–128.</ref>

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| Overpressured formation or reservoir (occurs frequently due to common distribution of tight gas with basin center locations and excessive overburden)

| Overpressured formation or reservoir (occurs frequently due to common distribution of tight gas with basin center locations and excessive overburden) || Requires appropriate exploration strategies or reservoir engineering approach to gas recovery

| Requires appropriate exploration strategies or reservoir engineering approach to gas recovery

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| Underpressured formation/ or reservoir due to stripping (erosion) of overburden

| Underpressured formation/ or reservoir due to stripping (erosion) of overburden || Requires appropriate exploration strategies or reservoir engineering approach to gas recovery

| Requires appropriate exploration strategies or reservoir engineering approach to gas recovery

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|+ {{table number|1}}Potential [[production problems]] inherent to each fractured reservoir type

|+ {{table number|1}}Potential [[production problems]] inherent to each fractured reservoir type

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! Type

! Type|| Problems

! Problems

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| rowspan = 4 | Type 1. Fractures provide essential porosity and permeability || Rapid decline rate

| rowspan = 4 | Type 1. Fractures provide essential porosity and permeability || Rapid decline rate