Previous Talks

Wednesday, April 10th, 2013

Relationship between fractures, fault zones, stress, and reservoir productivity in the Suban gas field, Sumatra, Indonesia

Peter Hennings, Patricia Allwardt, Pijush Paul, Chris Zahm, Ray Reid Jr., Hugh Alley, Roland Kirschner, Bob Lee, and Elliott Hough, ConocoPhillips

Abstract

It is becoming widely recognized that a relationship exists between stress, stress heterogeneity, and the permeability of subsurface fractures and faults. We present an analysis of the South Sumatra Suban gas field, developed mainly in fractured carbonate and crystalline basement, where active deformation has partitioned the reservoir into distinct structural and stress domains. These domains have differing geomechanical and structural attributes that control the permeability architecture of the field.

The field is a composite of Paleogene extensional elements that have been modified by Neogene contraction to produce basement-rooted forced folds and neoformed thrusts. Reservoir scale faults were interpreted in detail along the western flank of the field and reveal a classic oblique-compressional geometry. Bulk reservoir performance is governed by the local stress architecture that acts on existing faults and their fracture damage zones to alter their permeability and, hence, their access to distributed gas. Reservoir potential is most enhanced in areas that have large numbers of fractures with high ratios of shear to normal stress. This occurs in areas of the field that are in a strike-slip stress style. Comparatively, reservoir potential is lower in areas of the field that are in a thrust-fault stress style where fewer fractures with high shear-to-normal stress ratios exist. Achieving the highest well productivity relies on tapping into critically stressed faults and their associated fracture damage zones. Two wellbores have been drilled based on this concept, and each shows a three- to seven-fold improvement in flow potential.

Speaker Biography

Peter Hennings is Manager of Structure and Geomechanics, ConocoPhillips Technology and Projects. He leads a group of structural geologists, petrophysicists, geophysicists, and rock mechanicists whose mission it is to support ConocoPhillips’ global exploration and production businesses through research, technology development and application, consulting, and knowledge sharing activities. The areas of focus include the formation and evolution of petroleum systems; architecture and effectiveness of structural traps; the internal architecture, pore pressure, and stress state of reservoirs and their overburden; characterizing and modeling deformation and fluid flow in stress-sensitive, faulted, fractured and compliant reservoirs; and deriving detailed models of subsurface stress and rock strength for horizontal drilling and stimulation of low permeability reservoirs and ensuring asset operational integrity.
Peter is Consulting Professor of Geophysics at Stanford University with a focus on reservoir geomechanics and is Adjunct Professor of Geology at the University of Wyoming with a focus on the petroleum geology of the Laramide Rockies.
Peter is the Chair of the AAPG Petroleum Structure and Geomechanics Group, which is currently seeking AAPG division status, is an AAPG distinguished lecturer, and a GSA Honorary Fellow.
Peter received his Ph.D. in Geology from The University of Texas and his B.S. and M.S. in Geology from Texas A&M University.