AAPG Southwest Section

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Statistical Approach to Interpreting Clear Fork Zones for Perforation in Old Wells


The Bluff Creek area is part of the Sharon Ridge Field in Scurry County, Texas, and is comprised of 23 producing wells, 1 injection/disposal well, and 7 plugged wells operated by H.P. Slagel Producing Company, LLC. Management is with a third generation family member but with less historical well data available than desired. Obtaining logs and other information was of initial concern.

Sharon Ridge produces from Clear Fork, San Andres, and Wichita-Albany and dates to 1923. Other wells in the region produce from Wichita-Albany, Wolfcamp, Cisco, Canyon, and Strawn. Slagel production is from upper and lower parts of the Clear Fork; opportunities also exist for Glorieta and San Andres production. Bluff Creek production increased at various times from in-fill drilling along with suspected secondary recovery from specific wells. Recent production is over 1,900 bbls per month.

While logs were not found for all of the wells, many had GR-N logs from 1979 and mid-1980s. Some older logs had footage marked where perforations had been conducted. Other logs had no such markings, though scout cards/tickets usually listed upper and lower boundary for the producing zone. Thus a statistical method was needed for comparison and identification of other possible zones within the Clear Fork based on available GR-N log suites and the known perfed zones.