--> Abstract: Climate-Controlled Meteoric Diagenesis in Carbonates Below Unconformities, by Oliver Weidlich; #90077 (2008)

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Climate-Controlled Meteoric Diagenesis in Carbonates Below Unconformities

Oliver Weidlich
Sultan Qaboos University, Oman
[email protected];
o_weidlich@[email protected]

Sedimentologic and diagenetic data are important for the petrophysical characterisation of carbonates because they parameterise reservoir properties and help to predict flow units below the resolution of seismic lines. Among many control factors, meteoric diagenesis affected most carbonate platforms during sea-level lowstands. This diagenetic environment is commonly believed to be associated with increases in porosity, permeability and pore throat diameters. Using data from three carbonate localities, amelioration or deterioration of reservoir parameter was rigorously tested with a three-step approach. In the first step, the study characterized meteoric dissolution and the subsequent late diagenetic products that filled the pore systems. In the second step, sedimentological and diagenetic data was transformed into petrophysical data. In the third step, the importance of climate, especially humidity and aridity, was considered in order to understand meteoric dissolution and infill. The goal of the study is to make petrophysical predictions. Data from outcrop, slabs, thin section and stable isotopes were used to establish three scenarios that summarized significantly different processes involving meteoric diagenesis below unconformities: (1) increase of porosity and permeability and their preservation through time; (2) increase of porosity and permeability and subsequent pore system occlusion; and (3) decrease of porosity and permeability and creation of a barrier for pore fluids. Knowledge of the texture of the host rock, the time span involved in meteoric diagenesis and the climate regime are necessary to predict porosity and permeability of meteoric pore systems. The study provided evidence that a well-connected karst system is likely to be filled with sediment and cement, whereas smaller pore systems have the potential to remain open during basin development under more arid conditions. Depending on the aforementioned parameters, end-members of meteoric diagenesis are either seals or rocks with good reservoir properties.

 

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain