LINKED MICROPALEONTOLOGY AND LITHOLOGY OF CENOZOIC DEEP-WATERSEDIMENTS: APPLICATION OF MULTIPLE OVERLAPPING FORAMINIFERALLITHOBIOFACIES TO CUTTINGS-BASED ANALYSIS OF RESERVOIR PROPERTIES

摘要

Deep-water foraminiferal assemblages contain: (1) indigenous benthic taxa; (2) planktonic taxa from surface habitats; and (3) allochthonous benthic taxa from shelf habitats. Each of these categories of foraminifera carries information on the processes, lithology, and reservoir properties of deep-water environments. Unique associations of foraminifera (index taxa) might therefore be useful proxies for deep-water lithofacies that are important to the study of reservoir quality. Results to date suggest that abundance and succession patterns of frequently associated foraminiferal taxa define lithobiofacies that comprise a range of reservoir-prone and barrier-prone sedimentary units. Key deep-water lithobiofacies taxa and corresponding lithofacies commonly recognized in Gulf of Mexico wells include: (1) clean sands barren of foraminifera / massive fan channel and fan lobe sands composed of grain flows and Bouma "A" turbidite beds; (2) deep-water agglutinated flysch-type index foraminifera / laminated Bouma "B" through "E" turbidite beds; (3) allochthonous marginal-marine deltaic index foraminifera / siliciclastic basin-margin debrites; (4) allochthonous calcareous-bank-turtle-grass-flat index foraminifera / mixed siliciclastic-calciclastic basin-margin debrites; (5) open marine outer-shelf-upper-slope distal prodeltaic index foraminifera / proximal hemipelagites; (6) deep-water calcareous infaunal suboxic-dysoxic-basin index foraminifera/confined (ponded) hemipelagic dysoxites and oxygen-minimum dysoxites; (7) deep-water calcareous infaunal oxic-dysoxic-interface index foraminifera / sapropelites; (8) deep-water calcareous epifaunal index foraminifera /unconfined lower-slope and rise condensed hemipelagites; and, (9) foraminiferal ooze rich in planktonics /unconfined slope to abyssal-plain condensed pelagites.