Mesozoic-Cenozoic Detrital Record of the Circum-Gulf of Mexico: Implications for Clastic Reservoir Quality Assessment
Pre-burial controls on the quality of Gulf of Mexico Mesozoic and Cenozoic clastic reservoirs are composition and texture, which relate to provenance, source-to-sink parameters, and depositional facies. These factors vary stratigraphically and around the basin, from the passive northern domain, to the tectonically active southern and western margins. To assess the impact of these primary factors on reservoir quality, we compiled a petrographic database consisting of >5900 samples from >200 wells and outcrop localities in the US and Mexico. These data were compared with and corroborated by a detrital zircon database of ~400 samples, to establish links to provenance terranes in North America and Mexico.
We present these results in a series of ternary diagrams depicting the variability of normalized present-day framework (QFR) and rock fragment (Metamorphic, Sedimentary, Volcanic) composition in a chronostratigraphic transect along the Gulf of Mexico. For each time step, we integrate detrital zircon provenance analysis, and identify the key diagenetic events in which porosity may be preserved or destroyed.
Mesozoic sandstones derived from Peri-Gondwanan and Pan African sources in the NE Gulf of Mexico and in the Western Yucatan margin of Mexico are fine- to very fine-grained, well-sorted, and average 85% in quartz. Reservoir quality is driven by the degree of quartz cementation, which is in turn controlled by thermal history and the percentage of clay coatings on quartz grains. Drainage reorganization in North America and active Laramide tectonism resulted in a higher proportion of ductile lithics (up to 50%) delivered into the basin during the Paleogene. The fraction of rock fragments in offshore Lower Eocene turbidites is higher than onshore, probably due to sediment bypass into the slope. Paleogene reservoir quality in the deep water of the Northern Gulf of Mexico is thus driven primarily by effective stress due to mechanical compaction, although locally these effects may be minimized by early overpressure. Miocene sandstones derived from multiple proximal sources in the Southwest Gulf of Mexico (Veracruz and Sureste region) are medium- to fine-grained, moderately- to poorly-sorted, and contain <50% quartz and up to 30% volcanic and sedimentary rock fragments. Mechanical compaction drives porosity preservation in this region. In the northern Gulf of Mexico, the proportion of quartz in fine-grained Miocene rocks increases to >75% so that in deeply-buried and hot mini-basins, quartz cementation may severely impact reservoir quality.
AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019