Sequence Stratigraphy and Depositional Environments of Booch Sandstones (McAlester Formation/Desmoinesian), Arkoma Basin, Oklahoma

Dan T. Boyd and Neil H. Suneson.  Oklahoma Geological Survey, College of Earth and Energy, University of Oklahoma, 100 E. Boyd St., Rm. N-131, Norman, OK 73019 

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The oil- and gas-producing Booch sandstones are in the lower three-quarters of the Desmoinesian McAlester Formation. The Booch interval thickens from the Cherokee Platform south into the Arkoma basin where it consists of eight coarsening-upward parasequences bounded by flooding surfaces. The McAlester Formation probably was deposited in ~100,000 years, suggesting that each parasequence represents a fifth-order glacioeustatic cycle.

From base to top, each parasequence consists of a progradational stacking of distal-marine, prodelta, delta-front, delta-plain, and incised-valley deposits, although the upper deposits may be absent. Isopach maps and well-log character suggest that the distribution of the Booch sands was controlled by fluvial processes. The depositional environments of the sandstone reservoirs at the top of most Booch parasequences include distributary-mouth bars, distributary channels, crevasse splays, and/or multi-story channel-fills. Sedimentary structures such as bidirectional cross-lamination, flaser bedding, lenticular bedding, and small-scale cyclicity observed in outcrop are evidence that the Booch deltas were tidally influenced. All the Booch sandstones are associated with deltas or the incised valleys that fed them. The absence of shoreline sandstones between deltas suggests that wave energy was negligible.

The best Booch reservoirs were fluvially deposited as either incised-valley-fill or distributary-channel sands. Extensive winnowing of clays from tidally reworked sands enabled secondary silica, the dominant Booch cementing agent, to nucleate. As a result, the reworked sandstones typically are poorer reservoirs than the coarser channel-fill sandstones in which the grains are coated with clays.