Exploration Portrayal of the Geometry of Major Unconformities of the Arabian Plate

By

 Walter H. Pierce¹

(1) WHPierce Exploration, Cypress, TX

 This paper stems from construction of a plate-wide tops and age database of greater than 46,000 records for the Arabian Plate. The premise of the paper is that a regional understanding of the geometry of unconformities can facilitate exploration. A "database query to GIS mapping process" is developed to enable recognition and characterization of the major unconformities of the Arabian Plate. Plate-wide plots of ages versus age-count enable age stratigraphy of the major unconformities. Maximum and minimum age queries at unconformity surfaces allow structural mapping of unconformities. The process facilitates mapping of the time value of individual unconformity lacunae and the geographic position of amalgamation with underlying and overlying unconformities. Individual queries for time missing above and below the unconformity surfaces, mapped in combination, portrays transitions from truncation-domination to onlap-domination along unconformity surfaces. Queries tying age to stratigraphy enable worm's eye and subcrop map construction. Mapping recognizes three situations of unconformity impact on Arabian Plate hydrocarbon distribution: a) "juxtaposition", b) "edge", and c) "basal sandstone". "Juxtaposition occurs if an unconformity results in a reservoir and source connecting at the unconformity. The "edge" situation occurs if truncation or onlap makes an edge-termination of a seal. Hydrocarbon leakage focuses at the "edge". The "basal sandstone" situation occurs at the base of a sequence overlying an unconformity. The sandstone caps the unconformity surface and taps carrier systems (stratigraphic or structural) that are truncated by the unconformity. The mapping goal is to make visible geometries that portray these situations.