The Miocene Petroleum System, Northern Gulf of Mexico Basin: Implications for CO2 Sequestration in Offshore Texas State Waters

Taylor, Jordan-Leigh; Carr, David; Meckel, Timothy; Trevino, Ramon

This study integrated published data and electronic databases from an 181,000 km2 coastal area from Texas to Alabama that contains 1,357 major Miocene oil and gas fields in order to evaluate the Miocene petroleum system of the northwest Gulf of Mexico Basin. Our goal was to gain a broad, regional knowledge of trapping mechanisms and fluid migration in this mature petroleum province that would provide insights for CO2 storage potential of the sand-bearing Miocene section (up to 25,000 ft). Use of GIS technology allowed us to evaluate relationships between sets of specific field parameters and a multitude of geologic features.

Regional structural features exert primary control on trapping and distribution of Miocene hydrocarbons. In salt basins, such as the Houston Salt Embayment, Miocene traps frequently occur as part of vertically stacked complexes that produce primarily from Oligocene and older reservoirs. Where salt is minor or lacking, Miocene petroleum traps are typically associated with listric-normal growth faulting. Approximately shore-parallel, early Miocene fault zones, such as the Clemente-Tomas in offshore Texas State Waters, typically mark the landward extent of the voluminous Miocene gas play. Miocene-age faults likely prevented large volumes of natural gas from moving into up dip traps onshore. Offshore Texas State Waters partially overlie Miocene faults, suggesting that CO2 injected into Miocene reservoirs has high potential for regional entrapment.

The occurrence of favorable sandstone reservoir facies is the 2nd order control on trap types and geographic distribution of Miocene petroleum accumulations. Major Miocene hydrocarbon accumulations occur primarily in deltaic and shore-zone depositional systems. The largest fields occur in more homogeneous depositional systems, e.g., strand plain/barrier island complexes. The northeastward migration during the Miocene of sand-rich depocenters is evident in age-specific reservoir maps.

Miocene oil & gas fields are the volumetrically minor apexes of their respective, and typically much larger structural fetch areas. As such, existing Miocene fields represent CO2 capacity minima. Known reservoir volumes alone will not provide enough capacity for commercial scale CO2 sequestration, requiring investigation of quantitative CO2 capacity relationships between well-documented Miocene fields and their respective fetch areas.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013