Acoustic Leakage Detection in Underground Hydrocarbon Storage Caverns
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Solution Overview
Problem
Current methods for detecting leakage in underground hydrocarbon storage caverns are costly and prone to gas leakage due to friction deterioration, necessitating a more efficient and accurate testing method to prevent financial loss and environmental contamination.
Innovation Solution
The use of an acoustic pulse technique, involving a gas gun and nitrogen gas injection, to establish a reference level for the gas/liquid interface, followed by a waiting period to detect leakage, with measurements taken to determine the volume of gas injected and released, allowing for calculation of leakage rates and comparison to established limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wireline equipment is used to lower sensors into the well bore for detecting gas/liquid interface and measuring temperature and pressure, then measurement capability is improved, but cost and gas leakage through wireline packoff increase due to friction deterioration
Solution Approach 1:
The patent extracts the sensing function from the wireline equipment by using acoustic pulses transmitted through the well bore to detect the gas/liquid interface. The sensors remain at the surface while acoustic waves carry measurement information down the well bore and back, eliminating the need for sensors inside the well bore and the associated sealing problems.
Solution Approach 2:
The patent replaces the mechanical wireline system with an acoustic field-based measurement system. Instead of physically lowering sensors into the well bore, acoustic pulses are transmitted through the well bore to interact with the gas/liquid interface, and the reflected acoustic signals provide measurement data. This substitution eliminates friction deterioration and sealing issues.
2Measurement precision
If wireline equipment is used for leakage detection, then measurement capability is improved, but equipment cost and labor cost increase
Solution Approach 1:
The patent extracts the complex wireline equipment and sensors from the well bore, using instead simple acoustic pulse generation and reception at the surface. The measurement function is extracted from the complex mechanical system and implemented through acoustic waves that can be generated and detected with relatively simple equipment.
Solution Approach 2:
The patent replaces complex mechanical wireline equipment with an acoustic field-based system. Acoustic pulses are generated at the surface and transmitted through the well bore, eliminating the need for complex downhole sensors, motors, and control systems. This substitution significantly reduces equipment complexity and cost.
3Measurement precision
If nitrogen gas is injected to establish conditions for measuring leakage, then leakage measurement capability is improved, but gas leakage through wireline packoff occurs due to friction deterioration
Solution Approach 1:
The patent extracts the gas injection function from the wireline packoff system by using acoustic pulses to detect the gas/liquid interface position. The gas injected for measurement purposes remains in the well bore, and its presence is detected acoustically rather than requiring it to pass through sealing components.
Solution Approach 2:
The patent replaces the mechanical sealing system with an acoustic detection system. Instead of relying on the wireline packoff to contain gas while allowing measurement, acoustic pulses are used to detect the gas/liquid interface position, eliminating the source of friction deterioration and gas leakage through seals.
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 method provides accurate and cost-effective leakage detection, reducing the risk of financial loss and environmental contamination by identifying leaks with high precision and enabling timely remedial action.
Implementation Method 1
an acoustic pulse is transmitted down the well bore through the pipe joints to the gas/liquid interface and reflected back to the well head
Data Source
AI summary
Underground storage caverns are used for the bulk storage of hydrocarbon liquids, such as crude oil and gases. The caverns are typically formed in salt formations by dissolving the salt and removing it with a flow of water. The cavern is accessed through a bore hole which has casing and internal tubing with an annulus between the casing and tubing. Some cavern bore holes may have casing, but no tubing. The cavern typically has hydrocarbon liquid above brine with an inert gas above the hydrocarbon liquid. In order to use the cavern, and periodically check it for physical integrity, it is necessary to test the cavern to determine if there is leakage from the cavern or the bore hole. The interface of the hydrocarbon liquid and overriding gas is moved downward by injecting gas into the annulus. Acoustic pulses are sent down the annulus through the gas to determine when the interface is located just below the end of the casing in the top of the cavern chimney (a reference level) by examining the return reflection pulse from the interface for a polarity inversion. When this is detected, a measured volume of gas is injected into the annulus. After a waiting period, the gas is released from the annulus and measured until the interface is detected by acoustic pulses to again be at the reference level. The volumes of injected gas and released gas are compared to determine if there has been leakage from the cavern. Alternative, the interface can be driven by gas pressure from the surface down to the casing bottom and back to the surface with gas volumes detecting leakage.