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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 37 (1987), Pages 35-42

Fan-Delta Reservoirs in the Lower Cotton Valley Group (Jurassic), Kildare Field, Northeast Texas

Cynthia E. Black (1), Robert R. Berg (2)

ABSTRACT

Fan deltas are alluvial fans that prograde into a standing body of water from a proximal highland area. Few fan deltas have been recognized in the subsurface, but the Cotton Valley Taylor "B" sandstone can be interpreted as the distal part of a fan delta in Kildare field, Cass County, Texas. Three facies are distinguished in cores of two sandstones that are 40 ft (12 m) in thickness. They are, in descending order, (1) a beach facies of massive to laminated, well-sorted sandstone, (2) a channel facies of massive to laminated, pebbly sandstones and (3) an offshore facies of very fine-grained sandstones and interbedded black shales.

Facies 1 is a fine-grained (0.21 mm) and nearly structureless unit that is 15 ft (5 m) thick, lacks bedsets and has a high quartz content that approaches 95%. Facies 2 is conglomeratic in beds that fine upward and are 0.5 to 3 ft (0.15 to 1 m) in thickness. Facies 3 is thinly bedded in massive to laminated sets that are graded and separated by black shales. The total section represents a coarsening upward, rapidly prograding sequence that was partly reworked by wave action at the top. The dip-trending channel facies (2) is overlain by the strike-trending beach facies (1). Higher porosities of 12% and permeabilities of 7 md are found in the beach facies.


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