Construction of an intergranular volume compaction curve for evaluating and predicting compaction and porosity loss in rigid-grain sandstone reservoirs

Abstract

A B S T R A C TTo evaluate compaction as a factor in porosity evolution, a plot of intergranular volume vs. depth was constructed using data from relatively uncemented reservoir sandstones from a variety of depths, ages, and geographic locations. The resulting intergranularvolume-decline curve reveals that sands compact mechanically and intergranular volume declines rapidly, from about 40 to 42% at the surface, to about 28% at 1500 m. Between about 1500 and 2500 m, intergranular volume continues to decline slowly, until the framework stabilizes at around 26% (maximum potential porosity in the absence of cement or matrix). No further significant decrease in intergranular volume is observed to the depth limits of the data set at 6700 m. Comparison of intergranular volume and volume of quartz cement for different formations reveals no obvious balance between intergranular pressure solution (as monitored by intergranular volume) and quartz cementation. This indicates that grainto-grain pressure solution and quartz cement precipitation do not proceed concomitantly on the thin-section scale. Moreover, grain compaction is limited (to about 26% intergranular volume) in rigidgrain sandstones, which suggests that the occurrence and distribution of deep porosity is a function of the volume of cement available to fill the intergranular pores. Therefore, deep, porous sandstones are relatively uncemented rather than undercompacted.

Quartz Cementation in Polycrystalline Sandstone: Insights From Phase‐Field Simulations

“…The reduction of porosity in arenitic sandstone is governed by physical and geochemical processes that include mechanical compaction and cementation (e.g., Paxton et al, 2002;Taylor et al, 2004;Worden & Burley, 2003;Waugh, 1970;Walderhaug, 2000). The intergranular pore space is occluded by authigenic cement phases (such as quartz) resulting in the reduction of storage and flow capacity of sandstone reservoirs and thus reservoir quality (Amthor & Okkerman, 1998;Ajdukiewicz & Lander, 2010;Oelkers et al, 1996;Taylor et al, 2015;Worden et al, 2018).…”

Compaction control on diagenesis and reservoir quality development in red bed sandstones: a case study of Permian Rotliegend sandstones

“…Flechtingen Sandstones lacking major pore-filling cements, showing the most continuous illite coatings, and lowest IGVs, therefore, are interpreted to have experienced the highest degree of chemical compaction. Mechanical compaction in clean sands like Cornberg and Penrith Sandstones did not reduce IGVs below the theoretical minimum of 26% (Paxton et al 2002), however, IGVs in Flechtingen Sandstones are reduced down to 15%. Considering burial histories for study areas where they are available (Kohlhepp 2012;Turner et al 1995), burial depths are interpreted to be sufficient to lead to a maximum mechanical compaction under the boundary conditions proposed by Paxton et al (2002).…”

“…Mechanical compaction in clean sands like Cornberg and Penrith Sandstones did not reduce IGVs below the theoretical minimum of 26% (Paxton et al 2002), however, IGVs in Flechtingen Sandstones are reduced down to 15%. Considering burial histories for study areas where they are available (Kohlhepp 2012;Turner et al 1995), burial depths are interpreted to be sufficient to lead to a maximum mechanical compaction under the boundary conditions proposed by Paxton et al (2002). Chemical compaction has been discussed to be mainly controlled by thermal boundary conditions in burial depths exceeding 2 to 3 km, and only to a lesser extent by effective stresses (Bjørlykke 2006).…”

“…Sandstone compositions were classified after Folk (1980). The intergranular volume (IGV) was classified according to Paxton et al (2002) as the sum of the intergranular pore space, intergranular cement, and detrital matrix. Compactional porosity loss, cementational porosity loss, and compactional indices were calculated after Lundegard (1992).…”

“…Mechanical compaction Mechanical compaction commenced after initial deposition due to burial. Due to ongoing consolidation, both by compaction and cementation, the effect on porosity reduction by mechanical compaction in clean sandstones typically begins to approach equilibrium at burial depths exceeding 2 km (Paxton et al 2002).…”