CO2 Injection Optimization for Incomplete Miscible Reservoir Flooding
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Solution Overview
Problem
Existing carbon dioxide flooding methods for low permeability reservoirs fail to consider incomplete miscible displacement characteristics, leading to pressure funneling, uneven well spacing, and inefficiencies in recovery evaluation, gas breakthrough time prediction, and oil-gas migration laws, which hinder optimal development strategies.
Innovation Solution
A method and system for optimizing carbon dioxide injection that includes building a three-dimensional reservoir model, analyzing fluid and reservoir components, and optimizing injection mode, well pattern spacing, and water alternating gas systems based on incomplete miscibility characteristics using mathematical and numerical simulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If continuous gas injection is adopted, then injection simplicity is maintained, but recovery efficiency deteriorates due to pressure funneling and poor miscibility
Solution Approach 1:
The patent implements water alternating gas (WAG) injection, where water and gas are injected in periodic cycles rather than continuously. This periodic action allows water to improve sweep efficiency and control pressure distribution, while gas provides superior oil displacement and extraction. The alternating cycles prevent pressure funneling by using water to maintain pressure uniformity between injection and production wells, thereby resolving the contradiction between operational simplicity and recovery efficiency.
Solution Approach 2:
The patent optimizes key parameters including gas-water slug ratio, slug size, and injection rate based on the incomplete miscible displacement characteristics of low permeability reservoirs. By adjusting these parameters, the system achieves better pressure distribution and miscibility conditions, improving recovery efficiency while maintaining operational feasibility. The optimized parameters enable the WAG process to overcome the limitations of continuous gas injection.
2Reliability
If five-spot well pattern is used, then control over sand bodies and injection-production intensity are improved, but adaptability to different reservoir stages deteriorates
Solution Approach 1:
The patent introduces a dynamic well pattern adjustment strategy that transitions from five-spot to inverted seven-spot configuration as reservoir development progresses. In early stages, the five-spot pattern provides strong control and high injection-production intensity. As development advances and pressure funneling occurs, the system dynamically switches to inverted seven-spot pattern, which offers better adaptability and reduced gas channeling. This dynamic adjustment resolves the contradiction between initial control effectiveness and long-term adaptability.
3Area of stationary object
If too much water is injected, then macroscopic scanning efficiency improves, but microscopic scanning efficiency deteriorates
Solution Approach 1:
The patent optimizes the gas-water slug ratio and slug size parameters to achieve the right balance between macroscopic and microscopic scanning. The optimized parameters ensure that water slugs are sufficient to maintain pressure distribution and provide broad sweep (macroscopic scanning), while gas slugs are appropriately sized to penetrate pore structures and displace oil effectively (microscopic scanning). This parameter optimization resolves the contradiction between the two scanning efficiencies.
4Adaptability or versatility
If existing optimization models are used, then general applicability is maintained, but prediction accuracy deteriorates due to ignoring incomplete miscible displacement characteristics
Solution Approach 1:
The patent develops specialized optimization models tailored to low permeability reservoirs with incomplete miscible displacement characteristics. Instead of using generic models that assume complete miscibility, the patent creates localised models that account for the specific physical and chemical conditions of these reservoirs, including pore size, throat dimensions, and connectivity. This localized approach significantly improves prediction accuracy for recovery evaluation, gas breakthrough time, and oil-gas migration laws while maintaining reasonable general applicability through systematic methodology.
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
Improves recovery evaluation, gas breakthrough time prediction, and oil-gas migration laws by optimizing injection mode, well pattern spacing, and water alternating gas systems, enhancing reservoir development efficiency and sustainability.
Implementation Method 1
carbon dioxide has high solubility and good extraction function
Implementation Method 2
carbon dioxide has good extraction function... greatly improving the recovery effect of crude oil
Implementation Method 3
reduce the interfacial tension, greatly improving the recovery effect of crude oil
Implementation Method 4
based on the incomplete miscible displacement characteristics of carbon dioxide... carbon dioxide water alternating gas
Data Source
AI summary
A method and a system for optimization of development by carbon dioxide injection based on incomplete miscibility characteristics are provided, where the method includes following steps: building a three-dimensional reservoir model based on laboratory experiments and reservoir values, where the three-dimensional reservoir model includes: a fluid model and a reservoir model; based on the three-dimensional reservoir model, obtaining incomplete miscibility characteristics of reservoir development by carbon dioxide injection; and completing whole life cycle optimization development of carbon dioxide injection based on the incomplete miscibility characteristics.