Hydraulic fracturing is more popular, due to its revolutionary impact in the US oil industry, especially in unconventional reservoirs. This paper first presents the analysis of hydraulic fracturing treatments in 56 vertical and horizontal wells in the Wolfcamp and Spraberry formations of the Permian Basin in West Texas. Intrinsic treatment strategies and operational methodologies used by different operators in the Basin were evaluated with the goal of extracting and deducing insights into criteria that characterizes operational virtuosity. The evaluation focused on: proppants types and amounts, fluid types and volumes, treatment rates, well productivity and treatment cost. The second part presents the application and integration of these best practice concepts in the re-designing of hydraulic fracture treatments in a case study well already stimulated with available treatment data.
Vertical wells were studied with 25 wells with over 150 treatments in both formations, 18 horizontal wells in the Spraberry formation with over 200 treatments, in Midland sub-basin and 13 horizontal wells in horizontal Wolfcamp in Delaware sub-basin. The Spraberry formation is very fine-grained sandstone, siltstone and carbonates with shales. The Wolfcamp is a complex formation divided into A, B, C and D, mostly limestone, with interbedded organic-rich siltstones. Empirical and statistical analysis using correlations and analysis of variance were used to identify and distill the best practices that actively and positively increase the production rates and decrease the production costs in each of these formation and well types. These results were then integrated in designing optimal hydraulic fracture treatments for these formations in the case well. Log analysis was done with industry standard software for accurate interpretation of the target formations and determination of rock mechanical properties used in the hydraulic fracture design software.
Mined data and analysis showed that operators merely replicate designs from similar wells and formations. This practice increases the errors, costs, and reduces expected productivity. Results show that the use of 20/40 white proppant is not economical, while the use of 40/70 white proppant is recommended in both formations. Crosslinked gel creates more complex and wider fractures, but it increases cost drastically, while slickwater was amenable to treatment costs and production rate, but more volume will be needed for the treatments, hence, the use of hybrid fluids are recommended. The original design used 20/40 white sand, the total stage cost of the treatment was 707,236. In the new treatment design, 40/70 white was used instead; all the scenarios evaluated gave a reduction in cost with $100,000.
These results are applicable in enhancing optimal hydraulic fracture treatment designs for these formations in the Permian Basin. Also, they serve as templates for other basins with similar formations. These results will be made better by continuous improvements with integration of field results.