Oriented Fracturing – A Practical Technique for Production Optimization
Authors: Manrique J. F. , Venkitaraman A. 
Published: December 2007

Oriented fracturing is suggested to address complex reservoir issues such as multiple fractures, near-wellbore tortuosity, maximum proppant concentration, vertical coverage, natural fractures, tortuosity and erosional effects. These issues have significant impact on reservoir performance and well deliverability. Net pressure matches and geomechanical data indicate that effective oriented fracture stimulation treatments can be implemented where other treatments have failed or unacceptable production changes occurred.

Understanding of the near-wellbore stress distribution is critical to implementation of effective fracturing strategies. Reservoir quality variations and mixed lithologies with plastic behavior will alter the near-wellbore stress distribution, reducing the compressive stress of the rock. Thus, constant stress gradients (psi/ft) are misleading and rock mechanical properties measurements are of extreme importance.

Based on a detailed geomechanical model, the technique can be selectively applied. It is useful in intelligent completions where zone determination and the design and placement of perforations and/or fractures are critical for optimum production performance. Another application is optimal placement of perforations for reservoir, productivity and stimulation considerations. This technique also efficiently places fracture stimulation treatments having optimized fracture geometry, vertical coverage, fracture length and treatment volumes.

Several experimental1 and theoretical2 studies have investigated fracture initiation and propagation from vertical and deviated wellbores, providing insight into both the potential problems and the factors controlling near wellbore effects. The primary problems were identified to be: the near wellbore tortuosity, the occurrence of multiple competing fractures, micro-annulus pinch points etc., that lead to problems during job execution such as fracture initiation and premature screenouts. The primary controlling factors associated with these difficulties were identified as the orientation of wellbore and perforations in stress space, the effective shot density (number of "open holes"), perforation diameter, mechanical properties of the formation etc.

Geomechanical models have found great use in drilling and completion. For the purpose of effective fracturing, our geomechanical modeling includes a detailed description of earth stresses (vertical, minimum and maximum horizontal), pore pressure (depletion, overpressured, variable pressures, layered systems), and rock mechanical properties.

Perforating for fracturing methodology, as discussed in this work, uses the results of building a geomechanical model to 1) place the perforations oriented along the Preferred Fracture Plane (PFP); 2) account for stress contrasts, variable pressure effects and fracture initiation mechanics; and 3) optimize productivity. The methodology is based on the integration of a geomechanical reservoir description into fracturing design. This integration is discussed by Manrique et al.3,4 and Kordziel et al.5 as part of an integrated approach for stimulation treatment design and optimization.

As demonstrated by field and production results, the improved efficiency of the perforating and/or fracturing strategies minimizes treatment failures and significantly impacts treatment implementation and production enhancement.