Two-Stage Membrane Process for CO2 Rejection in Flowback Fluid
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Solution Overview
Problem
The challenge is to effectively treat flow back fluid from subterranean formations stimulated with CO2-based fracturing fluids, which initially contain high CO2 concentrations, leading to wastage of valuable hydrocarbons and excessive natural gas consumption due to flaring, as the fluid cannot be directly sent to downstream processing facilities until CO2 levels drop below 10%.
Innovation Solution
A two-stage membrane process is employed to separate CO2 from natural gas components, providing pipeline-quality natural gas and recovering condensable hydrocarbons, allowing for early recovery of valuable resources and reducing logistical and operational costs by reusing CO2 for subsequent fracturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flow back fluid with high CO2 concentration is sent directly to downstream processing facility, then CO2 concentration specification is violated, but treatment process adds complexity and cost
Solution Approach 1:
The treatment process is divided into two distinct membrane stages: first stage for water removal and second stage for CO2 removal. This segmentation allows each stage to be optimized for its specific function, with the first stage preparing the feed for the second stage, thereby achieving specification compliance through a modular, manageable process design
Solution Approach 2:
The first membrane stage performs preliminary water removal from the high CO2 concentration flow back fluid before it enters the second stage. This preliminary action reduces the water content that would otherwise interfere with CO2 removal efficiency in the second stage, enabling the overall process to meet specification requirements
2Reliability
If flaring is used to handle high CO2 concentration gas, then CO2 concentration specification is avoided, but valuable hydrocarbons are wasted and natural gas consumption increases
Solution Approach 1:
The membrane separation process extracts CO2 and water from the flow back fluid, concentrating these components in the permeate streams while recovering the natural gas components in the retentate streams. This extraction approach allows valuable hydrocarbons to be separated and reused rather than wasted through flaring
Solution Approach 2:
The process discards CO2 and water in dedicated permeate streams while recovering natural gas components in retentate streams. The recovered natural gas can be reused for flaring operations or other purposes, eliminating the need to burn valuable hydrocarbons and reducing natural gas consumption for maintaining flaring operations
3Loss of substance
If two-stage membrane process is implemented, then natural gas and hydrocarbons are recovered, but equipment complexity increases
Solution Approach 1:
The first membrane unit performs multiple functions: it removes water from the high CO2 concentration feed and prepares the stream for the second stage. The second membrane unit removes both remaining water and CO2 while recovering natural gas. This multi-functionality approach maximizes hydrocarbon recovery within a integrated two-stage system
Solution Approach 2:
The membrane process is structured with the first stage nested within the overall treatment train, feeding into the second stage. The permeate from stage one becomes the feed for stage two, creating a nested configuration where each stage builds upon the previous stage's output to achieve progressive separation and recovery
4Ease of operation
If CO2 is not recovered and reused, then logistical issues of providing liquid CO2 to remote wells persist, but additional equipment is required for CO2 recovery
Solution Approach 1:
The membrane separation system recovers CO2 from the flow back fluid at the well site, making the system self-sufficient for CO2 supply. The recovered CO2 can be stored and reused for subsequent fracturing operations at the same or nearby wells, eliminating dependence on external CO2 supply logistics and making the operation self-service
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 enables the recovery of valuable natural gas and hydrocarbons at an earlier stage, reducing flaring, natural gas consumption, and logistical challenges, while allowing for the reuse of CO2, thereby optimizing resource utilization and operational efficiency.
Implementation Method 1
a first stage membrane unit downstream of the pretreatment unit to separate out water and/or water vapor from the pretreated flow back fluid... a second stage membrane unit downstream from the first stage membrane unit to separate out CO2 from the water depleted flow back stream
Data Source
AI summary
The invention relates to a system and method of treating a flow back fluid exiting a well site following stimulation of a subterranean formation. The invention utilizes a two-stage membrane process during the period that the gas contains high concentrations of CO2 by volume, and allows for separation of CO2 from the natural gas components, providing pipeline-quality natural gas (approximately 5% CO2 by volume) to the gas collection system.