Changes

[[file:evaluating-diagenetically-complex-reservoirs_fig1.png|thumb|300px|{{figure number|1}}Cross section in the Crane Field, Richland County, Montana, showing extreme irregularities in the development of porous dolomite zones in the Red River Formation below the C-anhydrite.<ref name=pt06r78 />]]

[[file:evaluating-diagenetically-complex-reservoirs_fig1.png|thumb|300px|{{figure number|1}}Cross section in the Crane Field, Richland County, Montana, showing extreme irregularities in the development of porous dolomite zones in the Red River Formation below the C-anhydrite.<ref name=pt06r78 />]]

Diagenetic alterations are defined here as all physical and chemical alterations that affect a sediment subsequent to deposition, including tectonically produced fractures and faults. Diagenetic alterations that have been observed to generate reservoir heterogeneities having a major influence on reservoir rock properties are shown in Table 1. In sandstone reservoirs, carbonate and anhydrite cementation, clay authigenesis, secondary porosity generation, and fracturing are the most commonly reported alterations. In carbonate reservoirs, the diagenetic components most often observed are gypsum/anhydrite cementation, dolomite replacement, secondary porosity generation, and stylolitization. A [[cross section]] from Longman<ref name=pt06r78>Longman, M. W., Fertal, T. G., Glennie, J. S., 1983, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0067/0005/0700/0744.htm Origin and geometry of Red River Dolomite reservoirs, western Williston basin]: AAPG Bulletin, v. 67, p. 744–771.</ref> illustrates the complexity of porosity development in one of the few well-documented examples of a diagenetically complex reservoir ([[:file:evaluating-diagenetically-complex-reservoirs_fig1.png|Figure 1]]).

Diagenetic alterations are defined here as all physical and chemical alterations that affect a sediment subsequent to deposition, including tectonically produced fractures and faults. Diagenetic alterations that have been observed to generate reservoir heterogeneities having a major influence on reservoir rock properties are shown in Table 1. In sandstone reservoirs, carbonate and anhydrite cementation, clay authigenesis, secondary porosity generation, and fracturing are the most commonly reported alterations. In carbonate reservoirs, the diagenetic components most often observed are gypsum/anhydrite cementation, dolomite replacement, secondary porosity generation, and stylolitization. A [[cross section]] from Longman<ref name=pt06r78>Longman, M. W., T. G. Fertal, and J. S. Glennie, 1983, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0067/0005/0700/0744.htm Origin and geometry of Red River Dolomite reservoirs, western Williston basin]: AAPG Bulletin, v. 67, p. 744–771.</ref> illustrates the complexity of porosity development in one of the few well-documented examples of a diagenetically complex reservoir ([[:file:evaluating-diagenetically-complex-reservoirs_fig1.png|Figure 1]]).

{| class = "wikitable"

{| class = "wikitable"

|   Siderite

|   Siderite

| C Unit, Kuparuk Field, Alaska

| C Unit, Kuparuk Field, Alaska

| <ref name=pt06r38>Gaynor, G. C., Scheihing, M. H., 1988, Shelf depositional environments and reservoir characteristics of the Kuparuk River Formation (Lower Cretaceous), Kuparuk field, North Slope, Alaska, in Lomando, A. J., Harris, P. M., eds., Giant oil and gas fields—A core workshop: Society of Economic Paleontologists and Mineralogists Core Workshop 12, p. 333–389.</ref>

| <ref name=pt06r38>Gaynor, G. C., and M. H. Scheihing, 1988, Shelf depositional environments and reservoir characteristics of the Kuparuk River Formation (Lower Cretaceous), Kuparuk field, North Slope, Alaska, in Lomando, A. J., Harris, P. M., eds., Giant oil and gas fields—A core workshop: Society of Economic Paleontologists and Mineralogists Core Workshop 12, p. 333–389.</ref>

|-

|-

|   Dolomite

|   Dolomite

| Oregon basin Field, Wyoming

| Oregon basin Field, Wyoming

| <ref name=pt06r91>Morgan, J. T., Cordiner, F. S., Livingston, A. R., 1977, Tensleep reservoir study, Oregon Basin field, Wyoming— reservoir characteristics: Journal of Petroleum Technology, v. 29, p. 886–896, DOI: [https://www.onepetro.org/journal-paper/SPE-6141-PA 10.2118/6141-PA].</ref>

| <ref name=pt06r91>Morgan, J. T., F. S. Cordiner, and A. R. Livingston, 1977, Tensleep reservoir study, Oregon Basin field, Wyoming— reservoir characteristics: Journal of Petroleum Technology, v. 29, p. 886–896, DOI: [https://www.onepetro.org/journal-paper/SPE-6141-PA 10.2118/6141-PA].</ref>

|-

|-

|   Anhydrite

|   Anhydrite

| Pierce and Black Hollow Fields, Colorado

| Pierce and Black Hollow Fields, Colorado

| <ref name=pt06r76>Levandowski, D. W., Kaley, M. E., Silverman, S. R., Smalley, R. G., 1973, [http://archives.datapages.com/data/bulletns/1971-73/data/pg/0057/0011/2200/2217.htm Cementation in Lyons Sandstone and its role in oil accumulation, Denver basin, Colorado]: AAPG Bulletin, v. 57, p. 2217–2244.</ref>

| <ref name=pt06r76>Levandowski, D. W., M. E. Kaley, S. R. Silverman, and R. G. Smalley, 1973, [http://archives.datapages.com/data/bulletns/1971-73/data/pg/0057/0011/2200/2217.htm Cementation in Lyons Sandstone and its role in oil accumulation, Denver basin, Colorado]: AAPG Bulletin, v. 57, p. 2217–2244.</ref>

|-

|-

|   Authigenic clays

|   Authigenic clays

| Hankensbuttel-Sud Field, Germany

| Hankensbuttel-Sud Field, Germany

| <ref name=pt06r34>Gaida, K. H., Kessel, D. G., Volz, H., Zimmerle, W. 1987, Geologic parameters of reservoir sandstones as applied to [[enhanced oil recovery]]: SPE Formation Evaluation, v. 2, p. 89–96, DOI: [https://www.onepetro.org/journal-paper/SPE-13570-PA 10.2118/13570-PA].</ref>

| <ref name=pt06r34>Gaida, K. H., D. G. Kessel, H. Volz, H., and W. Zimmerle, 1987, Geologic parameters of reservoir sandstones as applied to [[enhanced oil recovery]]: SPE Formation Evaluation, v. 2, p. 89–96, DOI: [https://www.onepetro.org/journal-paper/SPE-13570-PA 10.2118/13570-PA].</ref>

|-

|-

| Stylolitization and associated cementation

| Stylolitization and associated cementation

|   Carbonate

|   Carbonate

| Spindle Field, Colorado

| Spindle Field, Colorado

| <ref name=pt06r102>Porter, K. W., Weimer, R. J., 1982, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0066/0012/2500/2543.htm Diagenetic sequence related to structural history and petroleum accumulation: Spindle field, Colorado]: AAPG Bulletin, v. 66, p. 2543–2560.</ref>

| <ref name=pt06r102>Porter, K. W., and R. J. Weimer, 1982, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0066/0012/2500/2543.htm Diagenetic sequence related to structural history and petroleum accumulation: Spindle field, Colorado]: AAPG Bulletin, v. 66, p. 2543–2560.</ref>

|-

|-

|   Anhydrite

|   Anhydrite