Dr.  Greg Samways:  Course creator and presenter.

How does geology help us understand the reservoir?  What do we actually need to know about the reservoir that the geology can help us with?  How can we use our understanding of the geology to predict reservoir properties ahead of drilling?

These are the questions that we want to address in this course on reservoir geology.

Reservoir Properties (Knowledge)

Before we consider the geology it is important that we completely understand the reservoir properties that are critical to reservoir performance.  These are the properties that will determine volumetrics, fluid flow in the reservoir and recovery factors.  The key reservoir parameters we need to understand, model and predict to enable to characterise the reservoir are:  porosity, permeability, grain density, wettability, capillary pressure, fluid saturations, and reservoir heterogeneity.

Geological Controls on Reservoir Properties (Knowledge)

All of the key reservoir properties we need to characterise are fundamentally controlled by the geology of the rocks, namely the original depositional texture and the subsequent modification of the original texture during burial compaction and diagenesis.  In this module we focus on the primary geological characteristics of the sediments that control the reservoir properties in carbonates and siliciclastics.

Depositional Processes (Knowledge)

Having defined the primary geological controls on reservoir properties it is time to define the depositional processes that are responsible for the erosion, generation, transport and deposition of carbonate and siliciclastic sediments.  Once we understand these fundamental processes we can go on to consider the environments in which they may occur.  The key processes which drive sediment erosion, transport and deposition in siliciclastics are ice, gravity, wind, and water (unidirectional flows and oscillating wave currents).  Carbonates are a little different in that the grains are largely generated in-situ by biological and chemical processes, but the effects of gravity, wind and water are still critical.

Depositional Environments (Knowledge)

Having defined the fundamental depositional  processes, we  can consider the depositional environments in which these processes might have occurred.  This module will provide an overview of the main characteristics of each key depositional system, focusing on the nature of the sediments that we might expect in each environment, likely reservoir properties and trends to expect, and implications for sand body geometries, heterogeneity and connectivity.

Determining The Geological Controls on Reservoir Quality (Skill)

If we are to make predictions of reservoir quality trends we must first determine the geological controls on reservoir quality in our reservoirs.  This module will show trends in reservoir parameters such as porosity, permeability and fluid saturation can be recognised, and evaluated and explained in terms of, for example, grain size, sorting and clay content.

Compaction and Diagenesis (Knowledge)

The reservoir parameter trends controlled by initial depositional texture typically persist after burial and compaction, as all pore systems are degraded to some extent by compaction and cementation.  If the original textural trends do persist, then the best predictive model will be the depositional model.  If, however, the original textural trends are overprinted by extreme diagenesis, then a diagenetic model will be needed to predict reservoir quality.  This module will explain the fundamentals of compaction and cementation/dissolution required to build reliable predictive models.

Facies Analysis and Depositional Modelling (Skill)

Emphasis will be placed on learning how to recognise each environment from cuttings, logs and cores.  We will also consider how we can predict depositional systems ahead of drilling, based on the wider basinal context

Introduction to Reservoir Quality Prediction (Skill)

There are a great many methods used to predict reservoir quality ahead of drilling and between wells including empirical and theoretical modelling, statistical interpolation of well data and seismic inversion.  This module will focus on generation of predictive porosity-depth trends, prediction of permeability from empirical porosity-permeability transforms and theoretical porosity-permeability models, and interpolation methods using well-based data.  Seismic inversion methods will also be briefly introduced.

Fundamentals of Sequence Stratigraphy (Knowledge)

One of the most important skills at all scales, from exploration to field-scale, is correlation. We need to understand the stratigraphic architecture in order to be able to predict facies distribution and sand body connectivity.  This module will establish the fundamentals of sequence stratigraphy, which provide the basis for seismic stratigraphic analysis and well correlation.

Reservoir Correlation (Skill)

This module will focus on the practical methods of correlation available to the reservoir geologist, including well correlation using logs, and seismic correlation.  Examples will be provided from a range of depositional settings to enable us to consider the issues posed by different depositional architectures and sandbody geometries.

Fundamentals of Structural Geology (Knowledge)

Many reservoir traps are formed by faulting, folding or a combination of the two.  The faulting and folding processes are also associated with fractures and joints, that may have a significant impact on reservoir performance depending on whether they are sealing or transmissive.  The faults themselves may also have a significant impact on reservoir performance, either acting as seals to lateral migration and thereby compartmentalizing reservoirs, or as vertical conduits for fluid flow, thereby causing traps to leak. This module will provide you with the foundation to enable you to undertake basic fault mapping and fault seal analysis.

Basic Fault Mapping (Skill)

This module will focus on the identification and mapping of faults using seismic and the recognition of faults in well sections

Basic Fault Seal Analysis (Skill)

The main way that faults become sealing is through the deposition of shale gouge on the fault plane.  There are many ways to estimate clay smear or shale gouge, including the Shale Gouge Ratio (SGR) method of Yielding et al (XXX).  This module will explain how shale gouge ratio can be estimated using fault throws, bed thicknesses and V-Shale estimates.  The sealing capacity of faults will be tested by comparison of across-fault pressures differentials.

What else would you like to see in such a course?  Let us know in the comments or use the Contact Us form.