Comparison of Multiphase-Flow Results in Transverse vs. Longitudinal Fracturing
Authors: Wilson Adam 
Published: April 2017

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 181813, “Multiphase-Flow Performance Comparison of Multiple-Fractured Transverse Horizontal Wells vs. Longitudinal Wells in Tight and Unconventional Reservoirs With Stress-Dependent Permeability,” by Rashid S. Kassim, SPE, Missouri University of Science and Technology; Larry K. Britt, SPE, NSI Fracturing; and Shari Dunn-Norman and Fen Yang, Missouri University of Science and Technology, prepared for the 2016 SPE Asia Pacific Hydraulic Fracturing Conference, Beijing, 24–26 August. The paper has not been peer reviewed.

There is an ongoing debate about whether the best practice is to drill a horizontal well in the direction of minimum horizontal stress, which would create a transversely fractured well, or to drill the well in the direction of maximum horizontal stress, which would create a longitudinally fractured well. This paper presents the results of a comprehensive multiphase-flow study that investigated the relationship between the principal stresses and lateral direction in hydraulically fractured horizontal wells.

Introduction

Rock mechanics research has shown that hydraulic fractures propagate perpendicular to the minimum horizontal stress in a normal fault environment, creating transverse fractures. This occurs if the perforations are aligned with the preferred fracture plane, which, in this case, is the maximum horizontal stress. However, the debate has centered on whether transversely fractured horizontal wells or longitudinally fractured horizontal wells are appropriate and best practice in a given area and for a given reservoir permeability.

The motivation for conducting this research came out of the realization that all previous studies that looked into the performance comparison of transversely vs. longitudinally fractured horizontal wells were limited in scope either by the range of reservoir permeability studied or by the single-phase-flow models that were used. None of the previous work undertook extensive integrated completion and reservoir simulations that modeled multiphase flow in transversely fractured vs. longitudinally fractured horizontal wells. This study incorporated the effect of non-Darcy flow, adsorption gas, the relative permeability effect on fluid flow in the fracture, and the effect of stress-dependent permeability on fracture conductivity, which were missing in previous studies.

Methodologies

Multiphase-flow study and performance comparison of transversely fractured horizontal wells vs. longitudinally fractured horizontal wells in tight sands and unconventional reservoirs with stress-dependent permeability were conducted using three different reservoir-simulation models. The first reservoir-simulation model was for a dry-gas reservoir (in contact with water) and produced only gas and water. The second reservoir-simulation model was built for a black-oil-type reservoir (undersaturated), which honored accurate reservoir-fluid properties for Permian Basin oil. The third reservoir-simulation model was built for saturated reservoirs and used compositional reservoir-simulation methods and honored the reservoir-fluid properties of Eagle Ford oil.