Depositional environments, diagenetic history, and reservoir characteristics of upper Smackover at Eustace field, Henderson County, Texas
Three shoaling-upward cycles were identified in the upper Smackover at Eustace field. Shoaling cycles ended during minor regressive stages. Each successive cycle was more widespread than the previous. Four depositional environments were defined: (1) shoal crest, (2) shoal flank, (3) back shoal, and (4) open marine. The shoal crest and flank environments are represented by ooid grainstones and ooid pisolite grainstones, respectively. Ooid-pellet grainstones and packstones were deposited in the back-shoal environment, whereas skeletal-pellet packstones were deposited in the open marine environment. The burial diagenetic history can be traced from early to late by the occurrences of the following events: micritization, formation of nodular anhydrite, isopachous rim cement, seepage reflux dolomitization, selective leaching, coarse sparry calcite cement, stylolites, saddle dolomite, pyrobitumen, quartz overgrowths, replacive anhydrite, and late leaching. Two porosity types are present at Eustace field: intercrystalline dolomite and oomoldic. Dolomitization occurred early and is the principal reason for the development of reservoir-quality porosity and permeability; it was selective for ooid-pellet grainstones and packstones of the back-shoal environment. Oomoldic porosity, which formed concurrently or slightly late than dolomitization, is not as extensively developed. Several agencies have reduced porosities and permeabilities in the field; they include saddle dolomite cement, sparry calcite cement, and pore-filling pyrobitumen (dead oil).
- Research Organization:
- Texas A and M Univ., College Station
- OSTI ID:
- 5907592
- Report Number(s):
- CONF-8710198-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Vol. 71:9; Conference: Gulf-Coast Association of the Geological Society and Gulf-Coast Section SEPM meeting, San Antonio, TX, USA, 28 Oct 1987
- Country of Publication:
- United States
- Language:
- English
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