Robert Barba, Schlumberger Well Services
The Spraberry trend of west Texas is a low-porosity naturally fractured reservoir, traditionally completed in the Upper Wolfcamp carbonate, Dean sand, Lower Spraberry sand, and Upper Spraberry sand zones. The overall interval is from 1200 to 1500 ft. thick, with completions encompassing from two to four stages. In all cases the wells require large hydraulic fracture treatments to produce economic quantities of oil and gas. The most common method of perforation selection involves correlating from well to well using cased hole gamma ray/neutron logs and drilling time. The large majority of the wells in the Spraberry trend have been perforated using this technique. The small minority of wells that have used openhole data have relied heavily on basic porosity and water saturation data to select perforations. Recent data suggest that production can be improved significantly by using VOLAN*, CFI*, and FracHite* data to select the perforated intervals. A group of 10 Dean/Wolfcamp wells that used the combination package of VOLAN/CFI/FracHite had a 103 percent increase in initial oil potential over 11 offset Dean/Wolfcamp wells that used basic openhole porosity and water saturation data. In addition, the well group with VOLAN/CFI/FracHite data produced 73 percent more oil over the initial four months of production than the offset wells. A discussion of the methodology, follows, along with the production results of the 21 wells in the study.