Abstract

A new physical model of carbonate diagenesis has been derived based on physical property measurements from 81 DSDP/ODP (Deep-Sea Drilling Project/Ocean Drilling Project) drill sites in the Atlantic Ocean. Changing depth gradients of porosity, bulk density, P-wave velocity (vertical and horizontal), and acoustic impedance characterize five successive diagenetic stages; (1) compaction of ooze, (2) breakage and dissolution of fossil tests, (3) formation of chalk through precipitation of calcite, (4) cementation, and (5) compaction of calcite crystals. Age-depth information from the drill sites was used to calculate the average duration of these processes in Atlantic Ocean basins. The model can predict carbonate sediment physical properties down to a burial depth of 1000 m. The model is presented for both lab and in-situ conditions and thus can serve as a standard for comparison with lab, log, and seismic measurements. An acoustic impedance vs. age curve derived from the model allows estimation of the initial and present-day diagenetic potential of carbonate sediments and chalk reservoirs.

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