Aggressive Stimulation Design Yields Better Returns

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 191864, “Aggressive or Not? Experimenting With Fracturing Design and Fluids in Pursuit of Better Returns,” by Max Nikolaev, SPE, Haiyan Zhao, Yenny Christanti, SPE, and Sergey Makarychev-Mikhailov, SPE, Schlumberger, prepared for the 2018 SPE Argentina Exploration and Production of Unconventional Resources Symposium, Neuquén, Argentina, 14–16 August. The paper has not been peer reviewed. The authors examine methods of adopting an aggressive approach to optimizing stimulation design to lower the breakeven level of operations and evaluate the results. Operators achieved significant improvements in production by changing parameters in the fracturing and completion design strategy, including, but not limited to, the amount of water used, the amount of sand pumped, stage spacing, maximum sand concentration, and fracturing-fluid selection. The complete paper addresses the importance of aggressive design, its evolution, and its enabling technologies. Trends in Development of Unconventional Resources Although completion practices and production numbers vary from basin to basin and from play to play, certain high-level trends remain in the development of unconventional reservoirs over the past few years. In most places, operators have been drilling increasingly longer laterals. Although public fracturing-stage-count information is scarce, internal service-company data still show a continuous increase in stage count and, in certain plays, an increase steeper than the increase seen in perforated intervals. Cased-hole completions with more than 50 stages per well are becoming common in all basins, thanks to the improved efficiency of fracturing and plug-and-perf•operations. At the same time, fracturing treatment sizes have grown even faster than have perforated intervals and stage counts. Median proppant volumes have nearly tripled during the past 5 years. The stimulation fluid volumes increased nearly proportionally to proppant volumes. Slickwater (SW) has become a fluid of choice in most plays, thanks to its operational simplicity and low cost. Hybrid treatments also remain popular; in these approaches, a high-viscosity crosslinked fluid, usually guar-based, often is pumped at the end of a treatment to deliver higher proppant concentrations and effectively prop the near-wellbore area. The number of higher-cost and operationally more-complex crosslinked fluid-fracturing jobs has decreased as placement of large amounts of proppant with crosslinked jobs becomes uneconomical. Longer laterals, better wellbore coverage, and significant amounts of fracturing materials enable increased well productivity in most plays. Production here is expressed in barrels of oil equivalent, calculated on the basis of relative cost, with 20 Mscf equal to 1 bbl of oil. Median production volumes, normalized by 1,000 ft of perforated interval, still demonstrate substantial increase over time. However, with production normalized by 1,000,000 lbm of proppant, or by proppant density per perforated interval, the trends turn negative, indicating diminished returns with further increase of proppant volumes per well.