Hydrothermal dolomitization: simulation by reaction transport modelling

Abstract

Reaction transport modelling (RTM) has been successfully used to simulate dolomitization and to predict the lateral extension of dolomitized bodies as potential hydrocarbon reservoirs in the subsurface as well as to give insights into the dolomitization process itself. Geological configurations that have been tested include reflux dolomitization, thermal convection and dolomitization in compactional burial settings. In this study the hydrothermal dolomitization model has been tested with a RTM approach where a limestone reservoir in an intermediate burial setting is fluxed in the presence of deep feeding faults. Hydrothermal fluids migrate upwards from the deep basin areas through extensional fault conduits reaching more permeable levels in the reservoir. The fluids enter the primary interparticle porosity and dolomitize the limestone creating moldic and vuggy porosity. The simulations demonstrate the importance of faulting in this dolomitization process. An effective control on dolomitization is thus exerted by the permeability distribution. Moreover, the type and reactivity of the fluids entering the limestone reservoir exert important controls on the extent of the dolomite bodies.

Petroleum reservoir quality prediction: overview and contrasting approaches from sandstone and carbonate communities

“…The grid cells in such models generally have dimensions on the orders of metres, with time scales that may range from hundreds to millions of years. RTMs have been widely applied to carbonate systems, especially in the area of dolomitization (Jones et al 2002(Jones et al , 2003(Jones et al , 2004Xiao & Jones 2006;Whitaker & Xiao 2010;Consonni et al 2016). They also have been used to simulate silicate reactions associated with sandstone and mudstone diagenesis (Czernichowski-Lauriol et al 1996;Thyne et al 2001;Brosse et al 2003;Sanjuan et al 2003;Xiao & Jones 2006;Yuan et al 2017;Geloni et al 2015).…”

“…Nonetheless, there are detailed, large-scale studies of diagenetic systems that seem to require loss and gain of species such as calcium and magnesium ( Fig. 9; Consonni et al 2016;Poteet et al 2016), potassium (Gier et al 2015) and even aluminium to explain the distribution of minerals in reservoirs (Nguyen et al 2016).…”

“…Carbonate rocks probably involve open system diagenesis during dolomitization ( Fig. 9; Whitaker & Xiao 2010;Jiang et al 2014;Consonni et al 2016) and are also probably susceptible to influxes of CO 2 during kerogen maturation (Heasley et al 2000).…”

Understanding controls on hydrothermal dolomitisation: insights from 3D reactive transport modelling of geothermal convection

“…These studies demonstrate the importance of the geometry of the fault, termination of the fault against a sealing layer, and distribution of permeability and precursor mineralogy in the country rock, but they are all predicated on a supply of hot, Mg 2+ -rich fluid at the base of the fault. Consonni et al (2018) highlight some of the challenges in moving beyond these outcrop-scale models of HTD that arise from uncertainties in fluid composition and volumes, and they contrast these with the RTM simulation of reflux and thermal convection systems for which fluid flow and chemistry can be better constrained from an understanding of the geometry of the carbonate platform, relative sea-level, and climate. Where fluids are derived from compaction, the geometry of the system can help constrain fluid volumes, but specifying fluid chemistries is more challenging -even when the mineralogy of the compacting formation is known (Consonni et al, 2010;Frazer et al, 2014).…”

Reactive transport modelling of hydrothermal dolomitisation using the CSMP++GEM coupled code: Effects of temperature and geological heterogeneity

“…Consonni et al (2016) simulated hydrothermal dolomitisation occurring in a lacustrine limestone reservoir of the Toca Formation (West Africa) and identified permeability as the major control on the distribution of dolomitised bodies. These authors also recognised the importance of flow rate, flow duration and fluid composition in determining the lateral extent of dolomitisation away from the faults.…”