Knowledge of Mechanisms

  • PetroGem Inc.

Reservoir Containment Assessment and Its Dynamic Nature

Synopsis: In many cases, reservoir containment and caprock integrity assessment is considered as a one-time requirement for proving the safety of a subsurface project while it is important to remember that such assessments are dynamic processes that should continue during the entire life of the project and, in some cases, even after its cessation. This article presents a workflow for dynamic reservoir containment assessment (DCAP) that accounts for the dynamic nature of this process.

Some cases of oil spills close to heavy oil projects in Alberta, Canada (source: AER).

Underground activities are growing very fast while the technologies used in these activities become more and more aggressive and risky. For instance, these days, industry is using high temperature steam, it is injecting chemical fluids in the rocks and it is intentionally fracturing the rocks. On the other hand, public sensitivity towards environment has been increasing on a daily basis. Economic reasons also play an important role as by controlling the containment of the reservoir we can prevent unwelcomed problems such as wellbore damage or surficial leakage that can be quite costly for any project. Major consequences of containment loss are:

  • Leakage of reservoir fluids

  • Ground deformation, in general, and ground surface subsidence/heave, specifically

  • Well integrity issues

  • Induced seismicity (due to induced fracturing and reactivation of faults and existing fractures)

  • Inflow of outside fluids into the reservoir

  • Heat Loss

All the containment-related geomechanical hazards must be studied under a comprehensive program called caprock integrity or reservoir containment assessment. In many cases, reservoir containment and caprock integrity assessment is considered as a one-time requirement for proving the safety of a project (and receiving operations approval from authorities) while it is important to note that reservoir containment assessment should be considered as a dynamic process for the entire life of the project and that may continue even after ceasing the underground operations. The rest of this article presents Dynamic Containment Assessment Program (DCAP), a generalized workflow with different modules required for containment assessment and caprock integrity analysis. Examples of operations that such workflow can be applied to are:

  • Conventional production/water flooding

  • Gas sequestration/storage

  • Thermal operations

  • Unconventional shale gas/oil

  • Nuclear waste deposits

  • Compressed air storage

  • Underground water production

Different mechanisms that can lead to loss of hydraulic integrity and containment of reservoirs (source: Soltanzadeh, 2009)

Dynamic Containment Assessment Program (DCAP)

This workflow implements data, tools, and techniques from different disciplines such as geology, petrophysics, geophysics, reservoir engineering, well engineering, hydrogeology, geochemistry, etc. Ideally, all these information resources are integrated in a comprehensive dynamic process that can even continue after cessation of underground operations. Different steps of this workflow are:

  • Appraisal data acquisition

  • Site characterization

  • Data interpretation and modeling

  • Feasibility assessment

  • Operational criteria and recommendations

  • Field monitoring

  • Real-time data updating

Diagram of Dynamic Caprock Integrity Program (DCAP)

Appraisal Data Acquisition

In the appraisal phase of geomechanical assessment of reservoir containment, data are collected from several different sources including:

  • Geological studies

  • Geophysical surveys

  • Hydrogeological and geochemical characterizations

  • Petrophysical studies

  • Production/injection rate histories<