Superimposed Multiple Orders of Sequences Predict Reservoir Migration and Thickness in Stratigraphically Trapped Haynesville Carbonate Reservoirs
NEUHART, DONNA, and DENNIS HWANG, Exxon Company U.S.A., Houston, TX
The Upper Jurassic Haynesville Formation is part of the Louark group located on the east flank of the East Texas salt basin. Haynesville gas production is from ooid grainstones which formed on a gently dipping carbonate ramp. Hydrocarbon was sourced from the underlying Smackover Formation basinal deposits and trapped stratigraphically by multiple ooid shoal pinch-outs. Therefore, an essential tool in prospecting for Haynesville gas is an understanding of Haynesville stratigraphy. Toward that end, we placed the formation into a sequence stratigraphic framework.
Haynesville stratal-stacking patterns and lithology distribution result from the superimposition of three orders of cyclicity. Evidence of second order (>10 m.y. plate motion), third order (1-10 m.y. eustatic sea level changes), and fourth order (0.1-1 m.y.) sequences are found within the Haynesvill data.
The entire Haynesville Formation lies within a second-order transgressive systems tract, which is expresses in facies as an overall deepening event. The superimposition of second-order extreme retrograde deposition during periods of in-phase second- and third-order transgression. The results were large shifts in deposition centers and additional reservoir thickness due to increased accommodation. Fourth-order sequences exerted the greatest control on ooid reservoir distribution due to shoal progradation.
By superimposing the observed multiple orders of sequences into the Haynesville geologic model, the top of Haynesville becomes both a sequence boundary in the third order and a maximum flooding surface in the second order. Together, fourth-order and third order sequences indicate the direction of reservoir migration as well as areas of maximum reservoir thickness.
AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)