Changes

How do we predict the quality of a carbonate reservoir? The procedure outlined below is one way to approach this problem. Use the parts of the suggested procedure that fit your situation.<ref name=ch09r49>Read, J., F., 1995, Overview of carbonate platform sequences, cycle stratigraphy and reservoirs in greenhouse and ice-house worlds, in Read, J., F., Kerans, C., Webber, L., J., Sarg, J., F., Wright, F., M., eds., Milankovitch Sea-level Changes, Cycles, and Reservoirs on Carbonate Platforms in Greenhouse and Ice-house Worlds: SEPM Short Course 35, 183 p. ''Good summary of concepts of climatic effect on sea level cycles, carbonate deposition, and reservoir development.''</ref><ref name=ch09r36>Loucks, R., G., Sarg, J., F., eds., 1993, Carbonate Sequence Stratigraphy, Recent Development and Applications: [http://store.aapg.org/detail.aspx?id=585 AAPG Memoir 57], 545 p.</ref> or <ref name=ch09r52>Sarg, J., F., 1988, Carbonate sequence stratigraphy, in Wilgus, C., K., Hastings, B., S., Kendall, C., G. St. C., Posamentier, H., W., Ross, C., A., Van Wagoner, J., C., eds., Sea Level Changes: An Integrated Approach: SEPM Special Publication 42, p. 155–182.</ref>

How do we predict the quality of a carbonate reservoir? The procedure outlined below is one way to approach this problem. Use the parts of the suggested procedure that fit your situation.<ref name=ch09r49>Read, J., F., 1995, Overview of carbonate platform sequences, cycle stratigraphy and reservoirs in greenhouse and ice-house worlds, in Read, J., F., Kerans, C., Webber, L., J., Sarg, J., F., Wright, F., M., eds., Milankovitch Sea-level Changes, Cycles, and Reservoirs on Carbonate Platforms in Greenhouse and Ice-house Worlds: SEPM Short Course 35, 183 p. ''Good summary of concepts of climatic effect on sea level cycles, carbonate deposition, and reservoir development.''</ref><ref name=ch09r36>Loucks, R., G., Sarg, J., F., eds., 1993, Carbonate Sequence Stratigraphy, Recent Development and Applications: [http://store.aapg.org/detail.aspx?id=585 AAPG Memoir 57], 545 p.</ref> or <ref name=ch09r52>Sarg, J., F., 1988, Carbonate sequence stratigraphy, in Wilgus, C., K., Hastings, B., S., Kendall, C., G. St. C., Posamentier, H., W., Ross, C., A., Van Wagoner, J., C., eds., Sea Level Changes: An Integrated Approach: SEPM Special Publication 42, p. 155–182.</ref>

# Make regional strike and dip [[Cross section#Stratigraphic cross sections|stratigraphic cross sections]].

# Break down cross-section stratigraphy into sequences and parasequences (see [[Fourth- and fifth-order sequences (Parasequences)]]).

# Group parasequences into sets by identifying [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradational, aggradational, or retrogradational patterns]] within sets. Make isopachs of systems tracts using parasequence sets and their correlation surfaces.

# Map [[paleogeography]] and facies tracts through time using systems tract maps; use core and log data to infer shorelines and platform edge locations.

# Study known accumulations that occur within the target formation.

#*  What are the trap types?  

| Make regional strike and dip [[Cross section#Stratigraphic cross sections|stratigraphic cross sections]].

#*  What are the pore types, pore geometry, thickness, and lateral extent of porous facies?  

#*  What are the facies sequences within parasequences?  

#*  How does facies distribution relate to trapping?

| Break down cross-section stratigraphy into sequences and parasequences (see [[Fourth- and fifth-order sequences (Parasequences)]]).

# Put known accumulations into the paleogeographic framework. Are they near the platform edge or near the shoreline? Nearshore sea level cycles cause more frequent changes in pore-water chemistry than offshore where subsidence is greater. Therefore, the diagenetic evolution of carbonate sediment is less complex offshore.

# Put known accumulations into a sequence stratigraphic framework. Were reservoir rocks deposited in transgressive, highstand, or lowstand systems tracts?

# Put target formation in a global and regional climatic framework. At the time of deposition, was the global climate in greenhouse, icehouse, or transitional conditions? Was the local climate arid or humid? Do expected geologic features due to climate correlate with observed features?

| Group parasequences into sets by identifying [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradational, aggradational, or retrogradational patterns]] within sets. Make isopachs of systems tracts using parasequence sets and their correlation surfaces.

# Predict reservoir location and quality using knowledge of known accumulations and regional geologic framework developed above.

#*  Can you find undrilled areas that share similar qualities to areas that produce from the target formation?  

#*  If prospects exist, will reservoir quality be similar?  

| Map [[paleogeography]] and facies tracts through time using systems tract maps; use core and log data to infer shorelines and platform edge locations.

#*  If not, why not?  

#*  Does the geology suggest other plays?

| Study known accumulations that occur within the target formation.

*  What are the trap types?  

*  What are the pore types, pore geometry, thickness, and lateral extent of porous facies?  

*  What are the facies sequences within parasequences?  

*  How does facies distribution relate to trapping?

| Put known accumulations into the paleogeographic framework. Are they near the platform edge or near the shoreline? Nearshore sea level cycles cause more frequent changes in pore-water chemistry than offshore where subsidence is greater. Therefore, the diagenetic evolution of carbonate sediment is less complex offshore.

| Put known accumulations into a sequence stratigraphic framework. Were reservoir rocks deposited in transgressive, highstand, or lowstand systems tracts?

| Put target formation in a global and regional climatic framework. At the time of deposition, was the global climate in greenhouse, icehouse, or transitional conditions? Was the local climate arid or humid? Do expected geologic features due to climate correlate with observed features?

| Predict reservoir location and quality using knowledge of known accumulations and regional geologic framework developed above.

*  Can you find undrilled areas that share similar qualities to areas that produce from the target formation?  

*  If prospects exist, will reservoir quality be similar?  

*  If not, why not?  

*  Does the geology suggest other plays?

==Making regional cross sections==

==Making regional cross sections==