Experimental simulation of chemomechanical processes during deep burial diagenesis of carbonate rocks

Abstract

Chemomechanical processes involved in the deep burial diagenesis of carbonate petroleum reservoirs are still poorly understood. To better understand these processes and explain how porosity and permeability can be preserved at the great depth of DBRs (deeply buried reservoirs), we developed an experimental device allowing both the simulation of high-pressure/stresses/temperature conditions (80°C, 60 MPa of confining pressure, and differential stress up to 40 MPa) of DBR and the circulation of different fluids in rock samples. We tested (triaxial multistep creep tests) four core samples of a cemented limestone and analyzed creep deformations, fluids chemistry, and petrographical and petrophysical properties of samples. Different flow conditions (no flow and flow through) and chemical compositions (natural meteoric water with and without phosphate ions) were considered. Our study showed that the precipitation of calcite on free pore walls of micrites blocks the microporosity between micrite crystals, thus rendering the microporosity inaccessible to fluids. Hence, the connected porosity decreased strongly after experimentation. This is due to the PSC (pressure solution creep) which is the main process implied in the porosity reduction of a carbonate rock during deep burial. The preservation of macropores during PSC allows the preservation of permeability. In addition, calcite solubility is positively dependent on mechanical parameters (axial compaction and axial stress), thus suggesting that calcite can precipitate during decompression of deep basinal fluids, resulting in changes in porosity. A comparison of experimental results with theoretical calculations showed that the integration of the PSC process into calculation databases would greatly improve the modeling of DBR.

Porosity and permeability development in compacting chalks during flooding of nonequilibrium brines: Insights from long‐term experiment

“…PORO-PERM DURING COMPACTION AND FLOW 2935 PUBLICATIONS Journal of Geophysical Research: Solid Earth RESEARCH ARTICLE [e.g., Hellmann et al, 2002b[e.g., Hellmann et al, , 2002aMadland et al, 2006;Risnes, 2001;Korsnes et al, 2008a;Risnes et al, 2003;Grgic, 2011;Neveux et al, 2014aNeveux et al, , 2014b. A similar phenomenon can also be seen in subcritical crack growth experiments where cracks may propagate even at imposed stresses below a critical level because of the chemical interplay between the fluids and the rock surfaces close to the crack tip [Røyne et al, 2011].…”

Origin of Micropores In Late Jurassic (Oxfordian) Micrites of the Eastern Paris Basin, France

“…The next step in understanding micrite diagenesis is to use an experimental approach. Simulation of early diagenesis on modern lime muds with various fluid and sediment compositions and subsequent simulation of burial diagenesis under stress, as recently performed by Neveux et al (2014aNeveux et al ( , 2014b, will allow better constraints for the chemical and geomechanical controls on the textural and petrophysical evolution of micrites.…”

Classifying chalk microtextures: Sedimentary versus diagenetic origin (Cenomanian–Santonian, Paris Basin, France)

“…Many authors have described micrite, based on samples from different locations, differing in age, deposit environment and type of diagenesis (e.g. Friedman, ; Le Roux, ; Masson, ; Loreau, , ; Wright et al ., ; Lambert et al ., ; Fournier & Borgomano, ; Vincent et al ., ; Volery et al ., ; Loucks et al ., ; Neveux et al ., ; Ehrenberg & Walderhaug, ; Tavakoli & Jamalian, ). Loreau (, ) proposed a system to classify micrite structure.…”