Genetic model of dolomite and its influence on development of high-quality carbonate reservoir
Dolomite reservoir occupies a critical position in global oil and gas exploration and development.As a type of calcium magnesium carbonate mineral,dolomite occurs in both marine and continental sedimentary environments,and also in diagenetic processes such as syngenesis,diagenesis,shallow burial,and deep burial.However,it is scarce in modern marine deposits.Therefore,the genesis of dolomite has been a hot point in researches at home and abroad on carbonate reservoir.Study results are as follows:(i)The genesis of dolo-mite can be divided into two types:the original and the secondary.Ultra-thick dolomite formations are mostly originated from the preexisting limestones permeated and reworked by Mg2+-containing diagenetic fluids under specific hydrodynamic conditions.(ii)According to the do-lomite-forming environments,hydrodynamic conditions,and the ion concentration in diagenetic fluids,the genesis of dolomite can be clas-sified as seven models,i.e.,evaporation pump,infiltration reflux,mixed water,seawater,burial,hydrothermal,and biogenic models.(iii)The process of dolomitization impacts the development of reservoir space.Under the theoretical conditions,the ionic radius of Mg2+ is smaller than that of Ca2+,and the porosity often increases when limestone transforms into dolomite.However,under the influence of complex factors such as diagenetic environment,newly generated dolomite content,and crystal structure,the reservoir space of dolomite may not necessarily be better than that of limestone.Usually,the dolomitization process improves the compressive strength and permeability of reservoir parti-cles.(iv)The genetic mechanism of high-quality dolomite reservoir indicates that the original sedimentary environment is the fundamenta-tion,the dolomitization is a necessary condition,and the diagenetic transformation is a key factor.
DolomiteDolomitizationGenetic modelReservoir characteristicsStructural type
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