Tapered Tailpipe and Auto-Dump Valve for Liquid Loading
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Solution Overview
Problem
Horizontal and deviated oil and gas wells face challenges in maintaining adequate superficial gas velocity (VSg) to effectively lift fluids, leading to liquid loading and slugging issues due to larger casing sizes and changing production conditions, which affect the efficiency of artificial lift systems.
Innovation Solution
Implementing a tapered-string tailpipe design with hydrostatic pressure-regulated valves and annular isolation to optimize VSg along the wellbore, reducing the internal diameter of the tailpipe and using auto-dump valves to manage fluid flow and pressure, ensuring consistent production and minimizing liquid loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If larger casing size is used to accommodate high injection rates during completion and fracturing, then ease of manufacture and construction is improved, but superficial gas velocity decreases leading to liquid loading and slugging
Solution Approach 1:
The wellbore flow system is segmented into two distinct zones: the upper production zone with larger casing ID for ease of installation, and the lower tailpipe zone with smaller ID for maintaining gas velocity. This segmentation allows each zone to optimize for its specific function without compromise
Solution Approach 2:
Different internal diameters are applied to different locations within the wellbore. The tailpipe section has a reduced ID specifically where high gas velocity is needed to lift fluids, while the upper casing maintains larger ID for construction benefits. This local differentiation resolves the velocity problem without sacrificing installation ease
2Productivity
If larger casing internal diameter is used to reduce friction losses during fracturing, then productivity of fracturing operation is improved, but fluid lifting capability deteriorates due to insufficient gas velocity
Solution Approach 1:
The flow path is divided into a fracturing zone (large ID casing) and a production zone (small ID tailpipe). During fracturing, slurry flows through the large ID casing minimizing friction losses. During production, gas and fluids flow through the small ID tailpipe maintaining sufficient gas velocity for reliable fluid lifting
Solution Approach 2:
The system dynamically adapts to different operational phases. The same physical infrastructure supports both high-rate fracturing (using large ID) and fluid lifting (using small ID tailpipe), with the effective flow path changing based on operational requirements
3Device complexity
If standard uniform diameter tubing is used throughout the wellbore, then device complexity is reduced, but hydrodynamic efficiency deteriorates due to inability to maintain optimal VSg in deviated sections
Solution Approach 1:
The tubing string transitions from a uniform diameter design to a tapered design where the lower section has a smaller ID specifically in the deviated/horizontal portion to maintain gas velocity, while the upper section has larger ID. This local optimization improves hydrodynamic efficiency without excessive complexity
4Loss of substance
If produced gas volume is reduced in aging wells, then loss of substance is minimized, but superficial gas velocity falls below critical levels causing liquid loading
Solution Approach 1:
The system changes the geometric parameter (internal diameter) of the flow path to compensate for reduced gas flow rates in aging wells. By reducing the ID in the tailpipe section, the same gas volume produces higher velocity, maintaining the critical velocity needed for fluid lifting even as overall gas production declines
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 enhances the well's ability to maintain optimal VSg, reducing liquid loading and slugging, leading to more consistent production profiles and increased gas and fluid output, even in aging wells with lower gas rates.
Implementation Method 1
the tailpipe has an internal diameter that is less than that of said tubing string to thereby increase a velocity of said gas flowing through said tailpipe which generates a flowing condition possessing a higher gas void fraction and thus reduces a pressure gradient of well fluids flowing in said tailpipe
Implementation Method 2
the flow control valve is operable to (i) open when a lower fluid pressure below the flow control valve exceeds an upper fluid pressure above the flow control valve to allow upward flow through the flow control valve
Data Source
AI summary
A hydrocarbon wellbore production apparatus includes a tailpipe and a control valve connected with the tailpipe. The tailpipe has a fluid inlet receiving well fluids entering the casing from a formation, and a fluid outlet above the fluid inlet to deliver well liquid to a connected pump inlet. The control valve is operable to (i) open when a lower fluid pressure below the flow control valve exceeds an upper fluid pressure above the flow control valve to allow upward flow through the flow control valve, (ii) close when the upper fluid pressure exceeds the lower fluid pressure by an amount which does not exceed a prescribed pressure limit value to hold fluid in the apparatus above the flow control valve, and (iii) open when the upper fluid pressure exceeds the lower fluid pressure by an amount which exceeds the pressure limit value to release excess fluid back down the tailpipe.