Waterflood Optimisation
Waterflooding is a secondary recovery method where water is injected into the reservoir through injection wells to maintain pressure and sweep oil toward producing wells. It is the most common improved recovery method worldwide, responsible for more than half of all oil recovered beyond primary depletion.
Key Waterflood Concepts
Injection Patterns
Wells are arranged in patterns - 5-spot, 7-spot, line drive, or peripheral injection - to maximise sweep efficiency. The choice depends on reservoir geometry, permeability, and well spacing.
Example: A 5-spot pattern places one injector at the centre of four producers, creating a radial sweep front that contacts a large portion of the reservoir.
Voidage Replacement Ratio (VRR)
VRR = Volume Injected / Volume Produced (at reservoir conditions). A VRR of 1.0 means you are replacing every barrel withdrawn. VRR < 1.0 means pressure is declining; VRR > 1.0 means you are over-pressuring.
Example: Field VRR dropped to 0.75 due to injector well scaling. Two injector workovers restored VRR to 1.05, halting the 2% monthly production decline.
Water Breakthrough & Channelling
Water preferentially flows through high-permeability streaks or fractures, bypassing oil in tighter zones. This causes premature water breakthrough in nearby producers, increasing water cut and reducing oil recovery.
Example: Tracer analysis showed that 60% of injected water from Well-INJ04 arrived at Producer-P11 in just 3 days, confirming a high-permeability channel.
Digital Waterflood Optimisation
Rate Redistribution
Use injection-production response analytics to identify which injectors are inefficiently supporting producers, and redistribute injection volumes to maximise sweep.
Capacitance-Resistance Models (CRM)
Data-driven models that quantify connectivity between injectors and producers using only rate and pressure data - no reservoir simulation required.
Hall Plot Analysis
Monitors injector performance over time. A change in slope indicates plugging (steeper slope) or fracturing (flatter slope).
ML-Based Optimisation
Machine learning models trained on historical injection-production data recommend optimal injection rates per well to maximise oil recovery.