Carbonate cementation sandstones

Dando, P.P., O Hara, S.C.M., Schuster, U., Yaylor, L., Clayton, C.J., Bayliss, S. and Laier, T., 1994. Gas seepage from a carbonate-cemented sandstone reef on the Kattegat coast of Demnark. Marine Pet. Geol., II 182-189. 

The faulted, non-carbonate cemented sandstones which were sampled from Haltenbanken and Tampen Spur, show clear evidence of diagenetic modifications after the deformation had occurred. Feldspar dissolution, illite precipitation and stylolitization are examples of such diagenetic processes. The pre- and post-faulting diagenetic reactions have been demonstrated to be a useful tool for the purpose of dating fault movements relative to basin subsidence (Sverdrup and Bjprlykke, 1992 Saigal et al., 1995). 

Carbonate-cemented sandstones occur throughout the San Joaquin basin. New isotopic data from nine additional areas combined with published papers allow comparison of cement compositions throughout the basin and a quantitative model of cement timing. 

Analytical data from 21 samples of carbonate-cemented sandstones of the Oseberg Formation are examined in this paper. These were selected from a set of 13 cores (157 thin sections) investigated as part of an integrated study of the diagenesis in the Oseberg Formation (Girard, 1995 Girard et al., 1995). The carbonate-cemented samples described here come from nine wells located in the Alpha... 

In the Gidgealpa Field, reflection coefficients calculated from the sonic and bulk density logs for carbonate-cemented sandstone interfaces with elastics that lack major carbonate cement are in the order of 0.22-0.26, demonstrating a relatively strong 2D seismic response. The seismic response is the relatively strong, generally continuous two-peak event that occurs immediately above the top of the... 

Authigenic kaolinite amounts to less than 1% on average (maximum 6%). It occurs as small booklets in primary and secondary pores, forming a meshwork which usually occupies only a portion of the pores (Fig. 14C), but occasionally may fill them entirely. Authigenic kaolinite is absent in carbonate-cemented sandstones. It is a late cement, which-formed after feldspar dissolution (see discussion on Origin of secondary porosity , below), and commonly occupies oversized, irregular or elongated pores. 

Chen, W. and Ortoleva, P., Reaction front fingering in carbonate-cemented sandstones. Earth Sci. Rev., 29, 183-198, 1990. 

The sandstones studied contain different types of cements, such as clay, quartz and carbonate cements. Clay cements are often a mixture of alio- and authigenic minerals. Kaolinite is the main component... 

Morad, S. 1998. Carbonate cementation in sandstones distribution patterns and... 

Secondary porosity results from the dissolution of carbonates in the subsurface environment. It can occur both in limestones and in sandstones where carbonate cements of original labile detrital minerals are dissolved. Because the formation of secondary porosity can substantially enhance the reservoir properties of sediments, it has received considerable attention from the petroleum industry. 

All granular rocks are rich in interconnected pores. The most common types are sand and sandstone. Their recharge and storage quality increases with the grain size. Cement (carbonate, silica, iron oxide) reduces the pore volume and, in extreme cases, may result in an impermeable sandstone (however, cemented sandstone tends to fracture). Conglomerate (a rock... 

Beckner J. R. and Mozley P. S. (1998) Origin and spatial distribution of early vadose and phreatic calcite cements in the Zia Formation, Albuquerque Basin, New Mexico, USA. In Carbonate Cementation in Sandstones. Distribution Patterns and Geochemical Evolution (ed. S. Morad). International Association of Sedimentologists, Oxford, vol. 26, pp. 27-52. 

The remaining porosity in sandstones with early diagenetic silica or carbonate cement may be preserved relatively better during subsequent burial (Bj0rlykke et al., 1989). Secondary porosity may also have a greater preservation potential than primary porosity during subsequent burial (Bj0rlykke et al., 1989). 

Pitman, J. K., and Spoeeti, C., 1996, Origin and timing of carbonate cements in the St. Peter Sandstone, Illinois Basin Evidence foragenetic link to Mississippi Valley-type mineralization in Crossey, L. J., Loucks, R., and Totten, M. W., eds., Siliciclastic diagenesis and fluid flow Concepts and applications Special Publication, Society for Sedimentary Geology, p. 187-203. 

At shallow depths carbonate cements may cause sands to become brittle and hard. Carbonate which precipitates on the sea floor may also form hard grounds in dominantly clastic sequences. Sandstones may become calcite cemented due to dissolution of biogenic aragonite at relatively shallow depth (less than a few hundred meters). Calcareous sediments flushed by meteoric water at shallow depth or exposed during regression may become rapidly ce-... 

Factors that control the geochemistry, abundance and distribution of carbonate cements are of prime importance in the understanding and prediction of porosity-permeability variations and in tracing the geochemical evolution of pore waters during the burial of sandstones and associated sediments. Moreover, the stable isotopic composition of nearsurface, eogenetic carbonates (e.g. in soil profiles) provides important clues to the palaeoclimatic conditions (e.g. Ceding, 1984). 

Carbonate Cementation in Sandstones Edited by Sadoon Morad 1998 The International Association of Sedimentologists ISBN 978-0-632-04777-2... 

Carbonate cements either indirectly enhance or deteriorate the reservoir properties of sandstones. Enhancement of reservoir properties occurs when (i) appreciable volumes of carbonate cements are dissolved, causing the formation of secondary porosity and (ii) small amounts of carbonate cement are evenly distributed in the sandstones to support the overburden weight and prevent the collapse of framework grains and consequent elimination of primary porosity. Souza et al. (1995) demonstrated that a few per cent of dolomite cement is sufficient to prevent the collapse of Aptian reservoir sandstones from Brazil despite the high content of ductile lithic fragments. 

In nodular cemented sandstones, the areas left uncemented often reveal evidence of later burial diagenetic modifications, such as compaction and quartz cementation (Morad et al., 1995). Burial cements are believed to be sourced from meteoric or dissolution of detrital carbonates and bioclasts (cf. Wilkinson, 1991). As the sandstone framework is expected to be stabilized due to early cementation, the burial dissolution of bioclasts may be recognized by oversized pores and mouldic pores filled with cement. 

Although abundant skeletal bioclastic fragments play an important part in the development of calcite-cemented sandstones, they should not be considered as the only source of such cements. Evidence for this is the common presence of calcite-cemented sandstones in Precambrian sequences. Additional evidence is the absence of bioclastic carbonates in Jurassic sandstones with strata-bound calcite cements (Bjorkum Walderhaug, 1993 Prosser et al., 1993). This suggests that other sources such as sea water and carbonate mud... 

---