Clay Mineralogy and Its Controls on Production, Pennsylvanian Upper Morrow Sandstone, Farnsworth Field, Ochiltree County, Texas: ABSTRACT

Abstract

Farnsworth field in Ochiltree County, Texas, is the most prolific upper Morrow oil field in the Anadarko basin, producing more than 36 million bbl of oil and 27 billion ft{sup 3} of gas since its discovery in 1955. The bulk of the production comes from an upper Morrow-aged sandstone locally referred to as the Buckhaults sandstone. The Buckhaults sandstone is a coarse to very coarse-grained, arkose to arkosic wacke. Grain-size distributions, sedimentary structure analysis, and sand-body geometry indicate that the Buckhaults was deposited in a fluvial-deltaic environment as distributary channel and distributary mouth-bar sands. Depositional strike is northwest to southeast. The source area for the Buckhaults sediments was primarily a plutonic igneous terrane, with a minor contribution from volcanic and reworked sedimentary rocks. The proposed source area is the Amarillo-Wichita uplift to the south. In addition, the Cimarron arch and/or Keyes dome to the west-northwest may also have contributed sediment to the study area. The large (average) grain size, the amount of feldspar present, and the overall immaturity of the Buckhaults sediments indicate a relatively short distance of transport. Detailed scanning electron microscopy and x-ray diffraction analysis of cores from the productive interval coupled with comparisons of varying completion practicesmore » across the field indicate a significant correlation between individual well performance, clay mineralogy, and completion technique.« less