Course description

This EET course starts by introducing definitions of fundamental concepts such as force, stress and strain; which are the building blocks of natural and operationally induced geomechanical failure, both at deep and shallow zones of the Earth lithosphere. In that context natural rock and lithospheric stress homogeneity vs heterogeneity, and isotropy vs anisotropy are also discussed. The course goes on to address and illustrate naturally occurring rock fractures. Natural fractures' statistical, geometric, and kinematic categories, and structural habitats are also discussed.  

Subsequently, the course presents the impact of natural fractures on fluid transmissivity /permeability and fluid storativity/effective porosity of rock masses which are crucial in many aspects such as hydrocarbon assets (both conventional and unconventional reservoirs), geothermal, and water reservoirs and nuclear waste repositories, cap seal and fault seal integrity and seismic hazards.

The high-resolution detection, measurement, and diagnosis of fractures and stress indicators on drill bore scale (e.g. oil and gas wells, geothermal wells, site investigation boring in environmental, and geotechnical engineering projects like nuclear waste repositories, dam sites etc) are a starting point to any effective geomechanical assessment of rocks. These are presented focusing particularly (amongst other tools) on borehole image logs like resistivity and ultrasonic images and rock samples such as full diameter drill core, side wall plugs, and cuttings. Quality control on logs- and core-based data is an essential step in assuring reliability of their interpretation and subsequent decision-making. Therefore, the course covers the uncertainties associated with such tools (e.g. natural versus induced fractures; borehole deformation phenomena and their stress/strength implications etc).

Current day Earth stresses are the driving engine for any ongoing natural and artificially induced rock deformation and failure. Operational geomechanics’ workflows used for the assessment of in situ stress magnitude and the in-situ stress orientation are introduced and discussed. Uncertainty sources in such workflows are also considered. The application areas of operational geomechanics with a particular attention to borehole instability and other engineering infrastructure integrity risks are then illustrated.

The course will also discuss the concept of rock-based mechanical anisotropy and heterogeneity and how they affect our operational practices. In that context it will discuss the impact on areas such as: hydrofracture stimulation; rock mass stability in deep and shallow environments including tunnels and dams, deep oil and gas boreholes and the seismic stability of existing faults in response to human made activities such as hydraulic fracturing and other operational activities.

Course outline

The course will cover the principles, and tools relevant to operational geomechanics with specific attention to borehole-scale characterization. The following aspects are covered:

1. Introduction to force, stress and strain;
2. Natural rock fractures: their causes, statistical, geometric, and kinematic categories;
3. Borehole-scale geomechanical tools:
    3.1 Borehole images
    3.2 Borehole rock samples (whole core, plugs, cuttings)
    3.3 Sonic logs and supplementary open hole logs;
4. Rock mechanical characterization based on rock samples and logs;
5. In-Situ Stress Characterization based on rock samples, logs, and special field tests:
    5.1 Assessment of in situ stress magnitude
    5.2 Assessment of in situ stress orientation;
6. Assessment of rock mechanical and in-situ stress anisotropy;
7. Application areas of operational geomechanics.

Participants' profile

The course is designed for geologists, geophysicists, and engineers working on and managers concerned with natural fractures and in-situ stresses characterization and instability risks of rock masses. The course is relevant to:

1. Oil and gas conventional and unconventional exploration, development and production;
2. Reservoir stimulation (e.g. hydrofracturing);
3. Assessment of geomechanical impact on fluid flow or sealing capacity of rocks (e.g. sealing faults; cap rock integrity etc);
4. Geothermal reservoirs;
5. Nuclear waste repository site investigation;
6. Geotechnical/engineering projects like tunnels, dams foundation, highways etc.

Prerequisites

Participants should have a basic knowledge of geology and a perception of the definition of rock porosity, permeability, and rock mass texture and structure. No software will be utilized in the course.

Mohammed S. Ameen holds a PhD in structural geology and rock mechanics, from Imperial College, London, 1988 and has had over 30 years industrial and academic experience in the Middle East and Europe. As part of his industrial experience he has spent nearly 22 years working with Saudi Aramco, as the Principal Professional in Geomechanics. Ameen joined the Exploration Organization in Aramco in 1998, and has worked on diverse structural and geomechanical issues for exploration and development on all hydrocarbon provinces in Saudi Arabia, covering both conventional and unconventional resources across the expansive stratigraphic section of the kingdom. His work has covered both carbonate and siliciclastic reservoirs.

Prior to joining Aramco Ameen worked on geomechanical issues related to hydrocarbon exploration and geotechnical projects, e.g. nuclear waste repositories, strategic gas storage in depleted reservoirs, tunnel stabilities etc. Ameen started his career working as an explorationist by pioneering comprehensive fractures and fold traps characterization across the Taurus-Zagros of Iraq, incorporating 30 structural traps. Ameen is an Associate editor of the AAPG Bulletin, and the Journal of Unconventional Oil and Gas Resources (JUOGR). He has been an instructor of industrial courses for the AAPG and in house in Aramco. He has 28 peer-reviewed articles; 3 edited books; one published book on operational geomechanics; and over 900 citations. He has been awarded four US patents, and has filed a few pending patent applications.