Changes

The interaction between water and rocks where saturated fluide occurs, is causing a stable reaction which changing metastable carbonate or the other stable reaction (recrystallization, includes neomorphism). Weathering and soil formation process in the unconformity involves a combination of diagenetic process that is dissolution, precipitation, biological activity, and neomorphism. Soil and low weathering zone are not always important as the reservoir rocks, because the porosity size of matrix in carbonate is relatively small and have high capillary pressure.

The interaction between water and rocks where saturated fluide occurs, is causing a stable reaction which changing metastable carbonate or the other stable reaction (recrystallization, includes neomorphism). Weathering and soil formation process in the unconformity involves a combination of diagenetic process that is dissolution, precipitation, biological activity, and neomorphism. Soil and low weathering zone are not always important as the reservoir rocks, because the porosity size of matrix in carbonate is relatively small and have high capillary pressure.

General dissolution plays a role as corrosion and increasing porosity in lower burial setting. Lower burial dissolution is called mesogenesis dissolution, following Choquette and Pray (1970) terminology, carbonate porosity classification (Mazullo and Harris, 1992). Saturation depends on CaCO3 in the fluide of burial because the fluide can be rich of CO2, H2S or organically acid. Burial dissolution makes the lower burial-carbonate reservoir to have porosity and permeability which can produce hydrocarbon, though standard “dogma” said that burial carbonate has 5% or low porosity. Increasing of porosity by the diagenetic dissolution produces size of pore with shape with that’s interconnected level widely.

General dissolution plays a role as corrosion and increasing porosity in lower burial setting. Lower burial dissolution is called mesogenesis dissolution, following Choquette and Pray<ref name=CP1970> Choquette, P. W. and L. C. Pray, 1970, [http://archives.datapages.com/data/bulletns/1968-70/data/pg/0054/0002/0200/0207.htm Geologic nomenclature and classification of porosity in sedimentary carbonates]: AAPG Bulletin, vol. 54, pp. 200-207</ref> terminology, carbonate porosity classification (Mazullo and Harris, 1992). Saturation depends on CaCO3 in the fluide of burial because the fluide can be rich of CO2, H2S or organically acid. Burial dissolution makes the lower burial-carbonate reservoir to have porosity and permeability which can produce hydrocarbon, though standard “dogma” said that burial carbonate has 5% or low porosity. Increasing of porosity by the diagenetic dissolution produces size of pore with shape with that’s interconnected level widely.

===Decreasing porosity===

===Decreasing porosity===

[[File:UGM_Subsurface_Fig_4.png|thumb|300px|{{figure number|4}}Establishment of diagenetic trap associated with the initial migration of oil.

[[File:UGM_Subsurface_Fig_4.png|thumb|300px|{{figure number|4}}Establishment of diagenetic trap associated with the initial migration of oil.

(A) The accumulation of hydrocarbons in the stratigraphic trap as a result of loss updip porosity. Calcite cementation happened to overburden contact oil / water. (B) With folding contact of oil / water layer is at end position a reservoir that has no relation with the structure (Aquitaine, 1982)]]

(A) The accumulation of hydrocarbons in the stratigraphic trap as a result of loss updip porosity. Calcite cementation happened to overburden contact oil / water. (B) With folding contact of oil / water layer is at end position a reservoir that has no relation with the structure<ref>Aquitaine, E., 1982, Exploration for Carbonate Petroleum Reservoirs: New York, John Wiley & Sons, Inc.</ref>]]

[[:File:UGM_Subsurface_Fig_4.png|Figure 4]] illustrates the sequence of events associated with diagenetic trap formation. In the example shows the mechanism original trapping with reduced porosity updip as a result of changes facies of grainstone oolitic into calcareous mudstone.

[[:File:UGM_Subsurface_Fig_4.png|Figure 4]] illustrates the sequence of events associated with diagenetic trap formation. In the example shows the mechanism original trapping with reduced porosity updip as a result of changes facies of grainstone oolitic into calcareous mudstone.

==References==

==References==

* Ahr, W.M., 2008, Geology of Carbonate Reservoirs: United States, A John Wiley & Sons, Inc.

* Ahr, W.M., 2008, Geology of Carbonate Reservoirs: United States, A John Wiley & Sons, Inc.

* Anderson, T. F. and Arthur, M. A., 1983, Stable isotopes of oxygen and carbon and their application to sedimentologic and paleoenvironmental problems, in M. A. Arthur (Ed.), Stable Isotopes in Sedimentary Geology: SEPM Short Course No. 10

* Anderson, T. F. and Arthur, M. A., 1983, Stable isotopes of oxygen and carbon and their application to sedimentologic and paleoenvironmental problems, in M. A. Arthur (Ed.), Stable Isotopes in Sedimentary Geology: SEPM Short Course No. 10

 

* Back, W., Hanshaw, B. B., Plye, T. E., Plummer, L. N. and Weidie, A. E., 1979, Geochemical significance of groundwater discharge and carbonate solution to the formation of Caleta Xel Ha, Quintana Roo: Mexico, Water Resources Res.

* Back, W., Hanshaw, B. B., Plye, T. E., Plummer, L. N. and Weidie, A. E., 1979, Geochemical significance of groundwater discharge and carbonate solution to the formation of Caleta Xel Ha, Quintana Roo: Mexico, Water Resources Res.

* Bathurst, R. G. C., 1975, Carbonate Sediments and their Diagenesis: New York, Elsevier Science Publ. Co.

* Bathurst, R. G. C., 1975, Carbonate Sediments and their Diagenesis: New York, Elsevier Science Publ. Co.

* Chapman, R.E., 1983, Petroleum Geology: Amsterdam, Elsevier Science B.V.  

* Chapman, R.E., 1983, Petroleum Geology: Amsterdam, Elsevier Science B.V.  

* Choquette, P.W., dan James, N.P., 1990, Limestones - The Burial Diagenetic Environment dalam Diagenesis: Canada, The Runge Press Ltd.  

* Choquette, P.W., dan James, N.P., 1990, Limestones - The Burial Diagenetic Environment dalam Diagenesis: Canada, The Runge Press Ltd.  

* Choquette, P. W. and Pray, L. C., 1970, Geologic nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin 54

*

* Chilingarian, Mazullo, Rieke, 1992, Carbonate Reservoir Characterization: A Geologic- Engineering Analysis, part I: Amsterdam, Elsevier Science B.V.

* Chilingarian, Mazullo, Rieke, 1992, Carbonate Reservoir Characterization: A Geologic- Engineering Analysis, part I: Amsterdam, Elsevier Science B.V.