Geomechanical Influences in Water Injection Projects: an Overview

Abstract

Résumé -Présentation générale des effets géomécaniques induits par l'injection d'eau dans les réservoirs -Au cours de l'injection d'eau, l'augmentation des pressions interstitielles et la diminution de température entraînent une diminution des contraintes effectives horizontales, notamment à proximité des puits d'injection. Ce déchargement mécanique peut activer des failles et des fractures naturelles au sein du réservoir, du recouvrement, des couches inférieures ou des fractures hydrauliques à proximité des puits d'injection. Ces effets géomécaniques induisent des modifications anisotropes de la perméabilité, généralement en augmentation, qui devraient être intégrées dans la simulation du réservoir, particulièrement du point de vue de la configuration des puits, afin d'en obtenir les meilleurs avantages commerciaux. , over-or under-burden, or Abstract -Geomechanical Influences in Water Injection Projects: An Overview -During water injection, increasing pore pressures and decreasing temperatures imply reductions in effective horizontal stresses, particularly in proximity to injection wells. This unloading can lead to activation of the natural faults and fractures by brittle failure in the body of the reservoir

The challenges and impact of compartmentalization in reservoir appraisal and development

“…Møller-Pedersen & Koestler 1997;Coward et al 1998;Jones et al 1998;Nieuwland 2003;McClay 2004;Swennen et al 2004;Boult & Kaldi 2005;Shaw 2005;Sorkhabi & Tsuji 2005;, Jolley et al 2007aLonergan et al 2007;Wibberley et al 2008a). In understanding the uncertainties and risks from compartmentalization these largely lie in the areas of: reservoir scale structural analysis Dee et al 2005;Fossen & Bale 2007); fault and fracture growth, fault zone architecture and characterization Wibberley et al 2008b); fault seal prediction (Bretan et al 2003;Dee et al 2007); the incorporation of faults and fault zone properties in reservoir models and simulation (Manzocchi et al 1999(Manzocchi et al , 2002(Manzocchi et al , 2008Harris et al 2005Harris et al , 2007Childs et al 2007;Fisher & Jolley 2007;Zijlstra et al 2007); integrated fluid description (Smalley & England 1994;Larter & Aplin 1995;Smalley et al 2004); the use of geomechanical data along with field and inter-well scale stress and strain analysis and modelling -incorporating the use of micro-seismicity for surveillance (Heffer 2002;Rutledge et al 2004;Sanderson & Zhang 2004;Main et al 2007;Zhang et al 2007;Osorio et al 2008). …”

“…We are now beginning to place a greater emphasis on capturing appropriate ranges of geological scenarios and associated uncertainty ranges, with the incorporation of dynamic signals from production data (Bentley & Smith 2008;Smalley et al 2008). Evidence is also mounting that as fields deplete under production they evolve mechanically: leading to changes in injectorproducer well communication; fault seal integrity; fault zone conductivity; fracture permeability; near and far-field stress configurations and orientations; and reservoir permeability heterogeneity (Heffer et al 1995;Heffer 2002;Main et al 2006;Zhang et al 2007). These effects are commonly not predicted at the early stages of field development.…”

Structurally complex reservoirs: an introduction

“…Finkbeiner et al 1997). Heffer et al (1995) and Heffer (2002) have documented directionality in flow and pressure transmission during water injection in nominally unfractured reservoirs. The direction is consistent with the predicted strike of those faults which were closest to failure, implying that they were already hydraulically conductive or became so as a result of the fluid pressure increase caused by injection.…”

Natural Fractures Characterization and In Situ Stresses Inference in a Carbonate Reservoir—An Integrated Approach

“…Stresses are controlled primarily by lithostatic loads and present-day tectonic loading [20,21,41]. Surface indicators (contemporary stress orientations) such as "pop ups" (small stress relief anticlines), may reveal mean stress orientations, the axis of the anticline will be roughly perpendicular to σ HMAX [42,43].…”

“…Subsurface indicators such as breakouts are the best for oil wells and aligned with σ hmin . Borehole images help in distinguishing genuine breakouts from other features [20,21]. In most cases where breakouts occur the rock was subject to very high stress anisotropy.…”