Abstract: Horizontal Drilling in Conventional Reservoirs: Analogs for Development and Exploitation

James R. Ehrets, Vincent J. Coringrato

Horizontal drilling programs in Mississippian fields of southeastern Saskatchewan have generated extensive reservoir engineering and geologic databases for the evaluation of horizontal well performance in a broad range of conventional, platform carbonate and clastic reservoirs. At the end of 1993, approximately 250 horizontal development wells had been drilled along the subcrop trend. Target reservoirs are dominantly within the Mississippian Mission Canyon and Charles formations, and are contained within four stratigraphic intervals including the Tilston, Frobisher-Alida, Midale and Ratcliffe. Reservoir characterization of pilot areas within several fields provides the basis by which horizontal and vertical well performance can be compared and evaluated.

Examples from three reservoir end-members illustrate a range of reservoir conditions within fields in various stages of vertical and horizontal well development. Comparison of reservoir and production data indicates that pore type distribution and drive mechanism are significant parameters in horizontal well recovery efficiency. Grainstone shoal reservoirs with active water drives are characterized by high initial potential rate, rapid decline and average recovery efficiency when compared with other reservoir types. Dolomitized, restricted shelf mudstone reservoirs with solution gas drives (enhanced by secondary water floods) illustrate a greater range in initial potential and decline, but more commonly display above-average recovery efficiencies. Sandstone tidal-channel reservoirs wi h moderately active water drives are characterized by variable initial potential, decline and recovery efficiency, reflecting significant reservoir heterogeneity.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994