N006 An Introduction to Reservoir Engineering for Geoscientists

The material covered in this course is built around the reservoir model, which can be constructed using analytical (calculator) or numerical (simulation) processes. The process is in three parts:

1. Building a static reservoir model
2. Developing a dynamic model
3. Reservoir management during the producing life of a field

The static reservoir model refers to the description of the reservoir in terms of reservoir and fluid distribution, volumetrics and reservoir zonation to identify the main potential flow units.

The dynamic model builds on the static model to include the consideration of fluid flow in the reservoir, near the wellbore and through the production tubing to the wellhead. The dynamic model is often constructed using a numerical reservoir simulator, but there are analytical techniques which can be used to predict fluid flow in the reservoir.

Reservoir management is a key activity for a producing field, performed with the general objective of maximising economic recovery. Monitoring is performed by measuring production and pressures in the reservoir and the results drive the forward activity programme and production forecasts.

Throughout the course, the use of complex mathematics has been avoided in order not to perturb creative geologists and the material concentrates on the principles rather than the detailed work of the reservoir engineer.

The following topics will be covered:

Introduction

Basic Reservoir Rock And Fluid Description

   Controls on fluid flow in the reservoir

• Rock permeability, and relationship with porosity
• Reservoir zonation; Darcy's Law and impact of permeability contrasts

Defining fluid contacts and estimating volumetrics

• Basic reservoir volumetrics
• Defining fluid contacts; RFT pressure measurements and Pressure vs Depth relationships
• Capillary pressures and saturation-height relationships

   Reservoir fluid properties

• Fluid sampling
• Analysis of fluid samples
  - Chemical properties of hydrocarbons
  - Physical properties of hydrocarbons
  - Phase diagrams
• Making use of the PVT report

   Well test analysis

• Uses of well testing
• Planning a well test
• Well testing operations
• Well test analysis – determining kh, skin, PI, boundary effects
   - Analysis principles
   - Analysis techniques – semi-log and log-log analysis
   - The components of total skin
   - Special test types

Dynamic Behaviour of Reservoir Fluids

   Material balance and fluid displacement

• Drive mechanisms; depletion, gas cap drive, water drive
• Material balance for oil reservoirs
• Material balance for gas reservoirs
• Fluid displacement on a macroscopic scale; sweep efficiency
• Fluid displacement on a microscopic scale; relative permeability
• Estimating recovery factors
• Diffuse and segregated flow regimes
• Buckley-Leverett displacement theory

   Dynamic well performance

• The inflow performance relationship
• Tubing performance curves
• Artificial lift
• Coning and cusping
• Well completions
• Horizontal wells
• Well stimulation; fracturing and acidisation

   Reservoir simulation

• Gridding
• Simulation principles
• Input, output and visualisation
• Upscaling static and dynamic model properties

Measuring Reservoir Performance And Reservoir Management

   Reservoir monitoring

• Overview of reservoir management
• Monitoring tools: pressure, PLT, TDT, RFT, MDT, XPT pressure data, production and injection data
• Well interventions and workovers

   Production

• Field analogues
• Decline curve analysis
• Analytical models
• Reservoir simulation and history matching
• Probabilistic production forecasting
• Reserves reporting

   Enhanced oil recovery techniques

• Defining the target oil
• EOR techniques
• Steam and fire flooding
• Miscible gas displacement
• Immiscible gas displacement
• Novel techniques