TECHNICAL PROGRESS

REGIONAL STRATIGRAPHY

The 10,000-ft-thick reservoir-bearing lithostratigraphic interval in Starfak and Tiger Shoal fields includes most of the Miocene Series and composes an overall regressive, progradational succession. The interval grades upsection from (1) basin floor and slope depositional facies to (2) distal shelf and transitional distal shelf/lowstand-delta (lowstand prograding wedge) facies to (3) medial and proximal shelf facies, and finally to (4) aggradational coastal-plain deposits a few hundred feet above the reservoir-bearing study interval. This upward-shallowing trend of depositional facies coincides with that of the entire Miocene interval in the offshore northern Gulf of Mexico. Paleontological data from selected wells indicate that the section from the oldest reservoir (Robulus L-8 sand) at the base of the study interval to the uppermost reservoir (A sand) represents about 15.5 my of deposition and ranges in age from early Miocene (about 22 mya) to latest Miocene (about 6.5 mya).

Composite type log of Starfak and Tiger Shoal fields. Delineation of stage boundaries is approximate and is based on micropaleontological data from several wells in both fields. Depositional settings interpreted by log-facies analysis, inferred lateral facies transitions, and vertical sand-stacking patterns.