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Finding Optimal Hydraulic-Fracture Angles in Productivity-Maximized Shale Well Design

Fig. 1—Reservoir- and fracture-geometry schematic. Pseudosteady-state-flow-regime model.

In general, hydraulic fractures propagate perpendicular to the horizontal-well axis whenever drilling is parallel to the minimum principal-stress plane. However, operators frequently drill horizontal wells parallel to lease boundaries, resulting in slanted hydraulic-fracture planes at angles less than 90° from the well axis. This study provides a model for the inclined fracture case. It applies and further extends the unified-fracture-design approach for rectangular drainage areas, relating the dimensionless proppant number to the maximum productivity index in pseudosteady-state conditions.

Introduction

Industry experience suggests that horizontal shale-gas development is enhanced by drilling in the direction parallel to the local minimum principal horizontal stress. Because US mineral leases frequently are rectangular areas with north/south and east/west boundaries, operators often drill parallel to the lease boundaries, prioritizing well saturation over optimum fracture-length propagation. This practice leads to the creation of hydraulic-fracture planes that are slanted at an angle less than 90° with respect to the well axis.

Extensive research has investigated the effects of angled fractures on well productivity. Theoretical and empirical data have been used to address the effect of wellbore azimuth on well performance in the Marcellus shale. Results showed that, for each degree a well was suboptimal to minimum horizontal stress, the estimated ultimate recovery decreased by 7.25 Mscf per foot of effective lateral length.

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 170965, “Optimal Hydraulic-Fracture Angle in Productivity-Maximized Shale Well Design,” by Nadav Sorek, SPE, Jose A. Moreno, Ryan Rice, Guofan Luo, and Christine Ehlig-Economides, SPE, Texas A&M University, prepared for the 2014 SPE Annual Technical Conference and Exhibition, Amsterdam, 27–29 October. The paper has not been peer reviewed.
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Finding Optimal Hydraulic-Fracture Angles in Productivity-Maximized Shale Well Design

01 March 2015

Volume: 67 | Issue: 3

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