09122-30

Primary Performer
TerraTek, A Schlumberger Company

Additional Participant
Schlumberger Unconventional Gas Regional Technology Center

Abstract
Understanding the geologic conditions controlling reservoir potential, and controlling fracture surface area generation and preservation, are essential for successful unconventional shale gas resource exploitation. These conditions, in turn, depend on reservoir properties and production mechanisms, as well as on hydraulic fracturing network mechanics. The latter is predominantly affected by localized heterogeneities (e.g., the presence and distribution of interfaces, mineralized fractures or other planes of weakness), that define a broader-scale reservoir fabric, and are fundamental sources for fracture complexity¹ . These are factors that may be understood but cannot be controlled. However, field experience suggests that other operational conditions (e.g., pumping rate, fluid viscosity, proppant) may also play a significant role in the development of fracture complexity² . If so, understanding these conditions will help us exercise some control on fracture complexity and will result in a significant opportunity for developing enhanced fracturing methodologies, leading to higher production and higher ultimate recovery.

The main objective of this theoretical and experimental project is to understand the operational drivers of fracture complexity (pumping rate, fluid viscosity, and proppant) and provide guidance for maximizing this opportunity. Other objectives of this project are to study the equivalency between pumping rate and viscosity (proppant effectively adds viscosity among other things) for controlling fracture complexity, and to define scaling relationships for relating laboratory-scale experiments to field-scale hydraulic fracturing treatments. The end product deliverable would be a methodology for control and management of fracture complexity such that this can be maximized on desirable loca-tions and minimized in undesirable locations, with the objective of maximizing gas production and recovery. The problem is difficult, but the potential for greatly improved production is real.

The project tasks include selection of optimal outcrop sites, collection of adequate samples, characterization of these samples and their interfaces, and a considerable number of tests on large-scale blocks (1 ft x 1 ft x 1.5 ft) for evaluation of fracture complexity under multiple conditions of stress, orientation of the planes of weakness, and for changing conditions of pumping rates and fluid viscosity. The project is expected to include measurements on outcrop rocks from the Marcellus, the Barnett, and the Mancos shales and/or other gas shales, tight sandstones and coal.

The project team includes the Schlumberger Innovation Center (Principal Investigator), TerraTek a Schlumberger Company (for laboratory testing), the Schlumberger Unconventional Gas Regional Technology Center (located at TerraTek and Dallas), and an external Advisory Board including representatives of producers with important portfolios of gas shale plays. These participant groups bring critical, essential technology, unique laboratory and field experience, access to outcrop sites, and completions information (including possibly micro-seismic measurements and well production). The management of the project will be led by Dr. Suarez-Rivera, Schlumberger Scientific Advisor and Head of the Innovation Center and located at TerraTek in Salt Lake City. Other team members encompass geologists and engineers, and most importantly, technical advice from supporting producer companies.

¹Suarez-Rivera et.al, 2006 ARMA/USRMS 06-1130.
²George King, SPE Completions Workshop, Horizontal Well Stimulation, Pittsburgh 2009.

Principal Investigator: Dr. Roberto Suarez-Rivera