Hydrocarbon Recovery via Sulfate-Enriched Displacement Fluid
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Solution Overview
Problem
In oil-bearing reservoirs with interbedded carbonate rock layers of varying water-soluble sulfate mineral content, existing secondary recovery methods, such as waterflooding, face challenges in achieving optimal incremental oil recovery due to insufficient sulfate mineral content in certain layers, leading to insignificant oil displacement.
Innovation Solution
A computer-implemented method determines operating modes for a crude oil displacement system by modeling the dissolution of water-soluble sulfate minerals and flow characteristics of injection water through carbonate rock layers, generating a sulfate-enriched aqueous displacement fluid to enhance oil recovery, particularly by isolating low-soluble layers and injecting low TDS water to form the displacement fluid in high-soluble layers, which then flows into and through adjacent low-soluble layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If waterflooding is used in carbonate reservoirs with interbedded layers of varying sulfate mineral content, then reservoir pressure is maintained and oil is swept towards production wells, but incremental oil recovery is insufficient in layers with low water-soluble sulfate mineral content
Solution Approach 1:
The patent applies local quality by injecting low TDS water selectively into high-soluble layers to generate sulfate-enriched displacement fluid in situ, rather than uniformly treating all layers. This targeted approach allows the displacement fluid to be generated where sulfate minerals are abundant, creating local zones of enhanced oil recovery while acknowledging the heterogeneity of the reservoir
Solution Approach 2:
The patent changes the TDS parameter of injection water (using low TDS water) to enable dissolution of water-soluble sulfate minerals in high-soluble layers. This parameter change transforms the chemical composition of the displacement fluid, enabling it to become sulfate-enriched and effective for wettability alteration and incremental oil recovery
2Productivity
If sulfate-enriched displacement fluid is generated in high-soluble layers, then incremental oil recovery is improved, but the displacement fluid must flow effectively through low-soluble adjacent layers
Solution Approach 1:
The sulfate-enriched displacement fluid acts as an intermediary that transfers the recovery benefit from high-soluble layers to low-soluble layers. By generating the displacement fluid in high-soluble layers and allowing it to flow into adjacent low-soluble layers, the system mediates the heterogeneity between layers, enabling incremental oil recovery to propagate across the entire reservoir interval
3Productivity
If low TDS water is injected to form sulfate-enriched displacement fluid, then wettability alteration and oil displacement are enhanced, but injection strategy complexity increases
Solution Approach 1:
The patent segments the reservoir into high-soluble and low-soluble layers based on sulfate mineral content, and applies different injection strategies to each segment. Low TDS water is injected selectively into high-soluble layers, while low-soluble layers receive the benefit indirectly through fluid flow from adjacent layers. This segmentation simplifies the overall strategy compared to attempting to treat all layers uniformly
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases oil displacement and recovery by optimizing the injection strategy based on rock layer characteristics, improving oil recovery rates and maintaining reservoir pressure, with incremental oil production ranging from 1% to 25% above conventional methods.
Implementation Method 1
model, using at least the data indicative of the characteristics of the injection water and of the characteristics of the carbonate rock layers, dissolution of water-soluble sulfate minerals from at least one first carbonate rock layer of the one or more first carbonate rock layers into the injection water that will occur on configuring the crude oil displacement system to inject said injection water into the said at least one first carbonate rock layer, whereby to generate first data representing chemical characteristics of a sulfate enriched aqueous displacement fluid formed in the at least one first carbonate rock layer
Implementation Method 2
model, using at least the data indicative of the water permeabilities of the carbonate rock layers, flow of the sulfate enriched aqueous displacement fluid through the at least one first carbonate rock layer, whereby to generate first flow characteristics of the sulfate enriched aqueous displacement fluid
Data Source
AI summary
A method for recovering crude oil from a reservoir that is penetrated by at least one injection well and at least one production well wherein the reservoir comprises a first carbonate rock layer and a second carbonate rock layer each having crude oil and a resident water present within the pore space thereof, the method comprising: isolating the second rock layer from direct hydraulic communication with the injection well; and injecting an injection water having a total-dissolved-solids (TDS) content lower than the TDS content of the resident water from the injection well into the first rock layer thereby forming a sulfate enriched aqueous displacement fluid through dissolution of water-soluble sulfate minerals from the first rock layer into the injection water wherein the displacement fluid flows through the first rock layer and from the first rock layer into and through the second rock layer thereby displacing oil towards the production well.