LPG Fracturing System Proppant Transport and Safety
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Solution Overview
Problem
Conventional fracturing fluids, such as carbon dioxide, while effective in minimizing formation damage, are hazardous due to their volatility and difficulty in safely injecting proppant, limiting their commercialization and effectiveness in well fracturing.
Innovation Solution
A liquefied petroleum gas (LPG) frac system utilizing a mixture of propane and/or butane as the fracturing fluid, which provides higher viscosity for effective proppant transport and easy recovery, combined with an inert gas like nitrogen for safety and pressure maintenance, ensures safe and efficient fracturing, especially in coal or shale formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon dioxide is used as fracturing fluid, then formation damage is minimized and fluid recovery is easy, but viscosity is insufficient to carry proppant deep into the formation
Solution Approach 1:
The patent combines carbon dioxide with lower order alkanes (propane, butane) to create a composite fracturing fluid. The CO2 provides formation damage minimization and easy recovery, while the alkanes provide the necessary viscosity to carry proppant deep into the formation. This composite approach resolves the contradiction by integrating the complementary strengths of both substances.
Solution Approach 2:
The patent changes the physical parameters of the fracturing fluid by using lower order alkanes with higher viscosity compared to pure CO2. The alkane molecules provide increased viscous drag, enabling effective proppant transport while maintaining the beneficial properties of CO2 through controlled phase changes and mixing ratios.
2Use of energy by moving object
If lower order alkanes such as propane are used as fracturing fluid, then viscosity is higher for effective proppant transport, but safety hazards increase due to volatility
Solution Approach 1:
Carbon dioxide acts as an intermediary substance that reduces the safety hazards of lower order alkanes. The CO2 dilutes the alkane concentration, reduces flammability risks, and provides a safer operating environment while maintaining the viscosity benefits. The mixture allows the alkane to perform its viscous function without exposing the system to the full safety risks of pure alkane handling.
Solution Approach 2:
The use of carbon dioxide creates an inert atmosphere that suppresses the flammability and reactivity hazards of lower order alkanes. CO2 displaces oxygen and creates a non-reactive environment, allowing the volatile alkanes to be handled and injected safely while retaining their useful viscous properties for proppant transport.
3Productivity
If propane and butane are used as fracturing fluid, then proppant transport capability is improved, but system complexity increases due to safety requirements
Solution Approach 1:
The patent changes the compositional parameters of the fracturing fluid to include a mixture of CO2 and lower order alkanes in specific ratios. This parameter optimization allows the system to achieve effective proppant transport capability while managing safety concerns through controlled composition, thereby avoiding excessive system 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
The LPG frac system effectively extends fractures, allows easy recovery of the fracturing fluid, and enhances well production by maintaining low hydrostatic pressure, reducing formation damage and increasing permeability, while ensuring safety through inert gas usage.
Implementation Method 1
The propane or butane is then vaporized and becomes mixed with the formation gas
Implementation Method 2
Inert gas such as nitrogen is used as a gas blanket and pressure test fluid to ensure the safety of using LPG as the frac fluid
Implementation Method 3
providing higher viscosity than carbon dioxide for carrying proppant deep into the formation
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A fracturing system for a well, in which a stream of LPG, a mixture of propane and butane, is injected into the well at frac pressure. Proppant is supplied into the LPG stream, and carried by the LPG mix into the formation. Inert gas such as nitrogen is used for purging system components of LPG, and to help protect against risk of explosion. Nitrogen may also be added to the LPG mix during a frac of shale gas or coal gas formations.