Crossover Valve System for Gas Well Liquid Unloading
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Solution Overview
Problem
Gas wells with low flow pressures and inconsistent production line pressures face challenges in maximizing gas production due to liquid loading, reservoir depletion, and formation damage, making it difficult to implement effective artificial lift methods in sour gas wells.
Innovation Solution
A downhole crossover valve system that utilizes reservoir energy and injected gas to activate a plunger, which reciprocates within the wellbore to unload liquids to the surface, enhancing gas production by increasing gas velocity and overcoming low flowing pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a packer is installed to isolate sour production from the annulus, then corrosion protection of the casing is improved, but the ability to use the annulus for gas injection is lost
Solution Approach 1:
The annulus is divided into two functional zones by the packer: the lower portion maintains corrosion protection isolation, while the upper portion above the packer is available for gas injection operations. This segmentation allows simultaneous achievement of both corrosion protection and gas injection capability.
2Productivity
If tubular size is changed or surface pressure is decreased to increase gas velocity, then liquid loading is reduced, but the cost and risk of intervention increase
Solution Approach 1:
The system uses the well's own produced gas, separated at the surface, and reinjects it through the annulus to provide artificial lift. This self-service approach eliminates the need for external gas sources, compressors, or complex intervention equipment, while still achieving the required gas velocity to unload liquids.
Solution Approach 2:
The invention uses pneumatic injection of separated gas through the annulus into the tubing to create artificial lift. The injected gas acts as a lifting medium to carry liquids to surface, achieving the desired gas velocity effect without mechanical intervention or tubular changes.
3Speed
If a compressor is used to reduce flowing wellhead pressure, then gas velocity increases and liquid unloading improves, but equipment cost and complexity increase
Solution Approach 1:
Instead of using an external compressor to reduce wellhead pressure, the system uses the well's own produced gas that has been separated at the surface. This gas is compressed to injection pressure and reinjected through the annulus, eliminating the need for a dedicated wellhead compressor and associated safety equipment.
Solution Approach 2:
Rather than reducing pressure at the wellhead to increase velocity, the system injects gas from the annulus into the tubing to create upward flow velocity. This inverted approach achieves the same liquid unloading effect without requiring wellhead pressure reduction equipment.
4Speed
If gas is injected into the annulus to activate the crossover valve, then gas velocity in the tubing increases, but the valve mechanism complexity increases
Solution Approach 1:
The crossover valve acts as an intermediary device that controls the flow path of injected gas from the annulus into the tubing. The valve mechanism, while adding some complexity, enables precise control of gas injection timing and flow rate, optimizing the artificial lift process while maintaining relatively simple operation.
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 system effectively increases gas production by maintaining a higher gas velocity above the critical rate, allowing for the efficient removal of liquids and maximizing well production potential, even in low-pressure conditions, thus extending the life of aging reservoirs.
Implementation Method 1
injecting gas into the annulus to at least the closing pressure to activate the pilot section, thereby exposing the power section to the annulus, thereby opening the crossover fluid passage and allowing injected gas to enter the production tubing, wherein the injected gas lifts liquids in the production tubing to the surface
Implementation Method 2
It is well known that liquid loading affects gas production when gas velocity drops below the level necessary to carry liquid droplets upwards, known as the critical gas velocity. Critical gas velocity is a function of flowing pressure, fluid and gas density, droplet size, surface tension, temperature and pipe diameter.
Implementation Method 3
the produced gas and injected gas may activate a plunger which reciprocates up and down the well bore, which acts as interface between the produced liquid and produced gas, thereby unloading all liquid to surface
Data Source
AI summary
A crossover valve assembly for insertion into production tubing, or integral with production tubing, includes an outer housing, an inner production tube, a pilot section responsive to external pressure to open an activation passage above a pre-determined pressure, a power section responsive to pressure in the activation passage to open an injection opening; and a crossover valve responsive to pressure in the injection opening to open a crossover port, allowing fluid communication from outside the outer housing to within the inner production tube. The crossover valve assembly may be used in a method of producing a vertical, deviated or horizontal gas well having an annular space defined by a well casing and a concentrically disposed production tubing, wherein an annulus exists above a packer isolating the annulus, includes the steps of (a) opening a communication path through the tubing into the annulus, and if necessary, removing any fluid in the annulus, (b) landing a crossover valve assembly within the production tubing above the packer and exposed to the annulus; and (c) injecting gas into the annular space to open the crossover valve and enter the production tubing, wherein the injected gas lifts liquids in the production tubing to the surface.