Nested Production Tubing Strings for Gas Well Liquid Lift
Solution Overview
Problem
Gas wells face production decline due to insufficient gas pressure and flow rate, leading to liquid accumulation in the wellbore, which restricts gas flow and eventually 'kills' the well, as the gas velocity drops below the critical velocity required to lift liquids to the surface.
Innovation Solution
Installing multiple production tubing strings of varying diameters within the wellbore to provide alternative flow paths, allowing gas production above the critical velocity by transitioning through progressively smaller flow paths as pressure and flow rates decrease, thereby maintaining efficient gas lift and preventing liquid accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single production tubing string is used, then the initial gas production capacity is high, but the production life is limited due to liquid accumulation when gas velocity drops below critical velocity
Solution Approach 1:
The production system is segmented into multiple tubing strings (first production tubing string and second production tubing string) with different inner diameters. This allows the well to transition from a larger diameter string for high initial production to a smaller diameter string when gas velocity decreases, thereby extending production life by maintaining critical velocity for liquid lifting.
Solution Approach 2:
The system changes the flow path parameters by transitioning from the first tubing string with larger inner diameter to the second tubing string with smaller inner diameter. This parameter change allows maintenance of critical gas velocity despite declining production rates, preventing liquid accumulation and extending the productive life of the well.
2Productivity
If the tubing string inner diameter is large, then the initial gas flow rate is high, but the gas velocity drops below critical velocity faster, leading to liquid accumulation
Solution Approach 1:
The system dynamically transitions between different tubing strings based on production conditions. When gas velocity in the first tubing string drops below critical velocity, the system switches to the second tubing string with smaller inner diameter, adapting to declining production rates and maintaining reliable liquid lifting capability throughout the production lifecycle.
Solution Approach 2:
The second tubing string with smaller inner diameter is installed in advance as a backup flow path. When the first tubing string can no longer maintain critical velocity, the system immediately transitions to the pre-installed second string, ensuring continuous reliable operation without interruption for well rework or intervention.
3Duration of action of moving object
If multiple production tubing strings are installed, then the production life is extended by maintaining critical velocity, but the device complexity increases
Solution Approach 1:
Multiple tubing strings serve different functions at different production stages. The first tubing string handles high-rate initial production, while the second tubing string maintains critical velocity during decline. This multi-functionality allows a single well completion to address both high initial productivity and extended production life requirements.
Solution Approach 2:
The second production tubing string is nested within the same wellbore as the first tubing string, with both strings extending from the wellhead to the production zone. This nested configuration allows transition between strings without requiring additional wellbores or major structural changes, minimizing the increase in device complexity.
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 prolongs the production life of gas wells by maintaining gas velocity above the critical velocity, reducing the need for costly reworking or deliquification processes and enhancing profit potential by minimizing liquid accumulation and flow restrictions.
Implementation Method 1
producing gas from a production zone in the subterranean formation through a first production tubing string at a first velocity that is greater than a critical velocity... producing gas from the production zone through a second production tubing string at a second velocity that is greater than the critical velocity
Data Source
AI summary
A system for producing hydrocarbons from a subterranean well including a wellbore extending from a surface into a subterranean formation includes a wellhead disposed at the surface. In addition, the system includes a production tree coupled to the wellhead and a casing coupled to the wellhead and extending into the wellbore. Still further, the system includes a first production tubing string extending into the casing from the wellhead to a first production zone and a second production tubing string extending into the casing from the wellhead to the first production zone. The first production tubing string and the second production tubing string are each configured to provide a fluid flow path for gases from the first production zone. The second production tubing string is radially spaced from the first production tubing string. The first production tubing string has an inner diameter D1 that is larger than an inner diameter D2 of the second production tubing string.