When Is Induced Fracture Complexity Necessary for Unconventionals Stimulation?

Abstract

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 168976, “Induced Fracture Complexity—When Is It Really Required in Unconventional Reservoir Stimulation?” by Leopoldo Sierra, SPE, and Mike Mayerhofer, SPE, Pinnacle—A Halliburton Service, prepared for the 2014 SPE Unconventional Resources Conference—USA, The Woodlands, Texas, USA, 1–3 April. The paper has not been peer reviewed. Induced-fracture-complexity maximization in addition to the primary hydraulic fractures has been accepted and fully implemented to improve recovery efficiency or productivity in unconventional reservoirs. This paper aims to develop criteria for identifying situations in which induced fracture complexity and sustained conductivity are or are not required. The results show that the fracture complexity and sustained conductivity are generally important for reservoir permeabilities lower than 100 nd for gas production and 500 nd for liquid production. Introduction The industry-implemented completion strategy for unconventional gas- or liquid- producing reservoirs considers increased reservoir contact to maximize productivity and hydrocarbon recovery through the following methods: Drilling long horizontal wellbores Optimizing the horizontal-wellbore placement to maximize the vertical coverage of the prospective formation Placing multiple transverse fractures by perforating the most-brittle and -prospective areas to generate complex fractures Alternating fractures in parent horizontal wellbores to induce stress interference that could result in more-complex fractures Engineering stimulation fluids to help induce complex fractures Although the existing completion strategy for each shale play has been optimized or is in the optimization process, a correlation between production and the perceived fracture surface area was not observed in some cases. Assuming the stimulation process is adequate and properly implemented in the field, the observed production behavior might be related to the combination of unknown reservoir permeability and induced fracture complexity. This paper investigates the benefits of induced fracture complexity in the stimulation of unconventional gas-or liquid-producing reservoirs for a wide range of reservoir permeabilities (10 nd to 0.001 md) and with a variable stimulation efficiency. Ultimately, this paper aims to answer the question of when induced fracture complexity is really necessary.