Sand thickness prediction from 3D seismic data: A case study of the Upper Jurassic Frisco City Sand of southwest Alabama

Abstract

Discovery of oil at Frisco City Field in 1986 opened up a new play in the Upper Jurassic Haynesville Formation, Monroe County, southwest Alabama. (Figure 1). The Haynesville play, now in its second decade, has expanded to include 22 fields. There are two main productive areas: Conecuh Ridge in southern Monroe County and Covington High in southern Covington County. To date, these fields have produced approximately 22 million bls of oil and 33.6 billion ft3 of gas. Discoveries are linked to basement paleohighs that are part of the updip basement structure trend of the eastern Gulf. Reservoirs are found in structural traps, basement-cored anticlines, and faulted anticlines. There are also combination structural-stratigraphic traps in which the Haynesville Sand pinches out on the flanks of basement highs. Figure 1. Regional map of southwest Alabama showing major structural features and location of Frisco City Field (modified after Mink and Mancini, 1995). Essential geologic factors associated with Haynesville fields are: Haynesville Formation (Figure 2) can be divided into an upper (unnamed) member and the lower Buckner anhydrite member. The Haynesville conformably overlies the Smackover Formation. If the Smack-over is absent, it overlies basement rocks. The Haynesville is conformably overlain by the Upper Jurassic/Lower Cretaceous Cotton Valley Group. Figure 2. Jurassic stratigraphy and schematic cross-section of Monroe County, Alabama. The only upper Haynesville members found to be productive include the Haynesville, Frisco City, Megargel, and Baas reservoirs. The Haynesville reservoirs are concentrated in the Covington High area. The Frisco City, Megargel, and Baas reservoirs are on Conecuh Ridge. The Frisco City Sand, the most prolific …