Petrographic Evaluation of Fractures and Geochemistry of Core from the Lower Smackover Formation: Case Study – Anadarko Petroleum Talley #B 1-22 Well, Columbia County, Arkansas

Peng Li and Michael Ratchford

Core samples were analyzed and examined from the Anadarko Petroleum No. B 1-22 well (API 03027110540000) that was drilled in Columbia County, Arkansas. Thin sections and geochemical samples were collected from the core sample interval 9,143.5 to 9,200 ft of the Lower Smackover Formation. Three main types of fractures were observed: 1) naturally occurring, vertical fractures cemented by calcite or anhydrite and locally containing intercrystalline porosity. 2) naturally occurring, open to straight and horizontal fractures within limestone, poorly to well connected, commonly associated with stylolite seams. 3) drilling induced open, horizontal to low-angle fractures entirely confined to carbonaceous stylolite seams and concentrated along planes of preferential weakness. Matrix porosity is uniformly low under thin section photomicrographs. The primary lithologies consist of 1) silty to sandy, peloidal lime grainstone to packstone, interlaminated with microbial (stromatolitic) lime mudstone; 2) silty peloid lime wackestone; and 3) cryptalgal lime boundstone (microbial thrombolytic). Carbonate grains (allochems) are dominated by small peloids (less than 0.5 mm); spheric particles are composed of microcrystalline calcite. Other allochems include sparse to locally common ostracod shells. Detrital organic matter is present in all of samples examined, ranging from a trace (<1%) to as much as 2% (visual estimate). Organic matter occurs as wispy, disseminated fragments, and concentrated as an insoluble residue along stylolite (dissolution) seams. Bitumen/asphaltic residue are present in intercrystalline voids, moldic pores, wispy discontinuous laminations and styloseams. Mercury injection capillary pressure (MICP) analysis conducted at a depth of 9190.5 ft indicates pore-throat sorting (PTS) within rock samples is fair (about 3). Geochemical analysis indicates that measured TOC values range from 0.39% to 1.11% with an average of 0.71% and production index averages 0.25. 

AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013