ABSTRACT

Significant gas reserves have recently been discovered in the Miogypsinoides sands along the Oligocene trend at the South Lake Arthur field. Detailed subsurface maps and seismic data are presented to exhibit the extent and nature of this local structure and to demonstrate future opportunities along the Oligocene trend.

Since discovery in 1980, the South Lake Arthur field has been extended three miles northeast and has enountered over 200 net feet of Miogypsinoides pay. Estimated reserves are in order of f1500 BCFG with limits of the field still unknown. Cross sections across the field depict the trap as a buried anticline with a gas column approaching 1000 feet.

Interpretation of the origin of this local structure is that of diapiric shale with a probable salt core. Detailed subsurface maps at the Miogypsinoides level and the overlying Camerina level are presented. These maps indicate that the deeper Miogypsinoides is a simple faulted anticline while the overlying Camerina is highly faulted. The apex of the overlying Camerina structure is juxtaposed by almost two miles relative to the deeper Miogypsinoides structure.

Analysis indicates that important structural growth occurred after Miogypsinoides deposition with a local unconformity covering the apex of the structure. Deposition of the overlying Camerina section was rapid, with faulting dying with depth in the underlying shale. State-of-the-art reconnaissance seismic data clearly exhibit this prolific buried structure. Occurrence of similar juxtaposed buried structures are predicted along the Oligocene trend offering explorationists many new opportunities.