Nitrogen-Carbon Dioxide Jetting for Horizontal Well Hydrate Fracturing
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Solution Overview
Problem
Existing natural gas hydrate exploitation technologies face challenges in achieving high single-well gas production rates and gas production cycles that are not suitable for commercial exploitation, with limited reservoir reformation methods in field experiments.
Innovation Solution
A nitrogen-carbon dioxide mixed gas jet apparatus is used to fracture the hydrate deposition layer by injecting a mixed gas in a jet state, forming cracks and replacing methane gas with carbon dioxide, enhancing permeability and enabling efficient methane collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing natural gas hydrate exploitation technologies are used, then the exploitation process can be implemented, but the single-well gas production rate and gas production cycle are far from ideal and cannot meet commercial exploitation requirements
Solution Approach 1:
The invention divides the gas injection process into multiple stages by injecting different gases (nitrogen followed by carbon dioxide) at different times. The nitrogen injection stage fractures the hydrate layer and creates channels, while the carbon dioxide injection stage replaces methane and enhances production. This segmented approach optimizes both production rate and sustainability.
Solution Approach 2:
The invention changes the physical and chemical parameters of the injection medium by transitioning from nitrogen to carbon dioxide. This parameter change enables both mechanical fracturing (nitrogen) and chemical replacement (carbon dioxide), thereby improving gas production rate while maintaining a sustainable production cycle.
2Productivity
If reservoir reformation is carried out to improve permeability and increase exploitation capacity, then the exploitation efficiency improves, but the device complexity and operational complexity increase
Solution Approach 1:
The invention uses high-pressure gas injection (pneumatics) to achieve reservoir reformation. By injecting nitrogen and carbon dioxide at controlled pressures, the hydrate layer is fractured and permeability is improved without requiring complex mechanical or thermal equipment. This approach increases exploitation capacity while keeping the device complexity relatively low.
3Productivity
If mixed gas is injected in a jet state to fracture the hydrate deposition layer, then the methane replacement efficiency improves, but the risk of passage blockage increases
Solution Approach 1:
The invention maintains continuous gas injection to keep passages open and prevent blockage. The continuous flow of nitrogen followed by carbon dioxide ensures that fractured channels remain clear while efficiently replacing methane. This continuous action sustains high replacement efficiency without compromising passage permeability.
Solution Approach 2:
Nitrogen serves as an intermediary gas that prepares the pathway for carbon dioxide injection. The nitrogen injection stage creates and maintains open passages, reducing the risk of blockage during the subsequent carbon dioxide injection stage. This intermediary approach ensures both high replacement efficiency and reliable passage permeability.
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
The method improves the efficiency of methane replacement and gas production by fracturing the hydrate layer, preventing passage blockage, and allows for heat and chemical agent injection, thus increasing the practicality and efficiency of natural gas hydrate exploitation.
Implementation Method 1
the mixed gas jet unit is configured to mix nitrogen and carbon dioxide
Implementation Method 2
inject the mixed gas into a hydrate deposition layer of the hydrate layer through the nozzle assembly in a dispersed manner
Implementation Method 3
the high-pressure water-proof chamber is used to isolate the high-pressure gas injection chamber from the outside world
Data Source
AI summary
A nitrogen-carbon dioxide mixed gas jet apparatus for a horizontal well and an exploitation method is presented. The jet apparatus includes: an offshore platform, a natural gas processing unit, and a pressurizing unit, wherein a portion of the gas exploitation pipe in the hydrate layer is provided with a gas injection horizontal well; a mixed gas jet unit and a nozzle assembly are disposed in the gas injection horizontal well; the mixed gas jet unit is configured to mix nitrogen and carbon dioxide, and then inject the mixed gas into a hydrate deposition layer through the nozzle assembly, so that the mixed gas replaces methane gas in the hydrate deposition layer; the portion of the gas exploitation pipe in the hydrate layer is provided with a gas exploitation horizontal well configured to collect the methane gas and convey the methane gas to the natural gas processing unit.