Contributions of Early Basin Deformation Heritage on the Creation of Complex Reactivated Fractured Zones in Carbonate Reservoirs

Loïc Bazalgette¹ and Jean-Pierre Petit^2
1Shell EP, Rijswijk, The Netherlands
²Universite Montpellier II, Montpellier, France

A large amount of outcrop data and experimental results have pointed-out the pre-eminent role taken by early basin deformation history - and especially early fracturing episodes - on the structure acquisition in carbonate reservoirs and on the mechanisms of initiation of high K fractured drains. This influence is particularly sensible on the development of fracture concentrations that form during further solicitation related to later tectonic episodes (basin inversions, for example).

Understanding the origin of early fractures and their behaviour during reactivation episodes is therefore crucial to be able to enhance the quality of the structural modelling of fractured carbonate reservoirs. Due to the potential effect of highly fractured drains on fluid flow, this understanding is also very important in order to predict realistically the reservoir’s dynamic behaviour.

This paper will first address some possible mechanisms of fracture initiation and propagation during early basin formation stages and will tackle some aspects of the evolution of the mechanical properties of rocks, during burying to early diagenetic stages, on early fracture style and distribution. Then through outcrop examples and experimental results, it will show how early fractures can influence deformation processes during later solicitations. The case of multiple fracture reactivations during tectonic inversions and stress field rotations will be especially studied. The effects of these mechanisms on the initiation and development of several types of highly fractured lineaments that can constitute high K drains, or on the opposite strong barriers for fluid flow, will finally be discussed.

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands