ABSTRACT

The Bureau of Economic Geology and Pemex Exploracion y Produccion conducted a joint study of gas plays in the Macuspana Basin, which shows that major plays occur in upper Miocene and Pliocene shallo-wmarine shoreface and wave-dominated deltaic systems in the onshore part of the basin.

The upper Miocene shoreface and wave-dominated deltaic complexes in the onshore part of the basin were sourced from north- and northwest-trending fluvial systems from the Chiapas foldbelt. Episodic movement along growth faults in the east and southeast parts of the basin intermittently halted progradation, controlling sandy deltaic depocenters. Traps occur as both four-way and three-way structural-stratigraphic combinations. Reservoir seal is provided by a 328- to 984-ft (100- to 300-m) lower Pliocene transgressive shale. Downdip pinchout of reservoir-quality shoreface sandstones is a key risk factor in the onshore part of the basin.

The offshore upper Miocene section consists of deepwater slope systems downdip of an inferred clastic-carbonate source associated with the Yucatan Platform. Thin, calcareous, turbidite sandstones lapped onto a major turtle structure, potentially providing updip-porosity pinch-outs.

Sandy Pliocene shoreface depocenters formed in shale-withdrawal subbasins, primarily in the northwest part of the basin. To a lesser extent, the upper Miocene was also affected by shale withdrawal. Unlike in the more productive upper Miocene, reservoir seal is a major risk factor in upper and middle Pliocene reservoirs having few thick, upper bounding shales.