Hydraulic Fracturing Treatments in the Permian Basin: Distillation of Best Practices in the Spraberry and Wolfcamp Formations

Abstract

Hydraulic fracturing is being used globally to unlock hydrocarbon resources in unconventional reservoirs. However, the efficient utilization of resources in most treatment designs is debatable. A study of hydraulic fracturing treatments in 56 vertical and horizontal wells representing 1,151 treated stages in the Wolfcamp and Spraberry formations of the Permian Basin in West Texas was conducted in this paper. Intrinsic treatment strategies and operational methodologies used by the well operators were evaluated with the objective of extracting and deducing insights into criteria that characterize operational virtuosity, efficiency and inefficiency. Treatments of vertical wells were studied with 25 wells in both formations, in the Midland basin. 18 wells were studied in Spraberry horizontal well treatments, while horizontal Wolfcamp treatments were studied with 13 wells in the Delaware basin. Well completion records, treatment reports and well files were reviewed for treatment parameters on each well. The study concentrated on indices like, proppants types and amount; fluid types and volumes pumped; treatment rates and pressures; productivity and treatment cost. Empirical and statistical analysis using correlations and analysis of variance were then conducted and used to identify the best practices that actively and positively increased production rates and decreased production costs in each of these formations and well types. The Spraberry is very fine-grained sandstone, siltstone and carbonates with interbedded shales in the studied area. The Delaware Wolfcamp is a complex formation with carbonates, mostly limestone, and interbedded organic rich mudstones in varying proportions. Results show that the use of 20/40 white as a proppant is not economical, in both formations either in vertical or horizontal wells, because of the huge increase in treatment costs. Use of 100 mesh and 40/70 white proppant in both formations was amenable to better production rate. Results show that usage of crosslinked gel increases treatment costs drastically. Slickwater was found to improve production rates, although huge volumes were needed for large proppant amounts. The use of HCl acid as spearhead in formations with high carbonate content like the Wolfcamp was found to improve treatment results. Increasing the number of stages increases treatment cost, but increasing the perforated intervals correlates positively with production rate.