Heterogeneous Proppant Pillars for Fracture Conductivity
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Solution Overview
Problem
Existing methods for heterogeneous proppant placement in hydraulic fracturing lack control over pillar location and tend to result in pillars extending the entire fracture height, preventing channels from connecting to the wellbore, thus limiting hydraulic conductivity.
Innovation Solution
A method involving alternating slugs of thickened proppant-free and proppant-carrying fluids injected through clusters of perforations, with sequences moving at different rates and separated by regions of proppant-free fluid to form pillars that do not extend the entire fracture height, creating interconnected channels leading to the wellbore.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alternating slugs of thickened proppant-free fluid and proppant-carrying thickened fluid are injected through clusters of perforations, then hydraulic conductivity is enhanced by maximizing open space in the fracture, but the complexity of the fracturing process increases due to multiple injection stages and fluid types
Solution Approach 1:
The fracturing fluid is segmented into alternating slugs of proppant-free thickened fluid and proppant-carrying thickened fluid. This segmentation allows the proppant to be distributed in discrete intervals rather than continuously, creating the heterogeneous structure needed for high conductivity while managing the complexity through systematic alternation of fluid types
Solution Approach 2:
Different regions of the fracture are given different qualities: some regions contain proppant pillars for structural support, while other regions remain as proppant-free channels for high-velocity fluid flow. This local differentiation of fracture properties maximizes hydraulic conductivity by creating optimal flow paths in specific locations
2Reliability
If proppant pillars are placed at intervals throughout the fracture, then fracture conductivity increases through interconnected open channels, but control over pillar location becomes difficult resulting in pillars extending the entire fracture height
Solution Approach 1:
The proppant-free thickened fluid slugs are injected first to establish the channel locations and dimensions before the proppant-carrying slugs are injected. This preliminary action creates defined spaces where proppant will be excluded, ensuring pillars form only in specific intervals and do not extend the entire fracture height
Solution Approach 2:
The thickened fluid acts as an intermediary that temporarily occupies space and prevents proppant from entering certain regions. By controlling the placement and volume of this intermediary fluid, precise control over pillar location is achieved, preventing pillars from extending throughout the entire fracture height
3Strength
If pillars extend the entire fracture height, then the fracture is well-supported under closure stress, but channels cannot connect to the wellbore limiting hydraulic conductivity
Solution Approach 1:
The proppant pillars are segmented to occupy only specific intervals within the fracture rather than extending continuously from top to bottom. This segmentation creates discrete support zones while leaving gaps that form interconnected channels connecting the fracture to the wellbore, simultaneously maintaining structural support and enabling fluid flow
Solution Approach 2:
The injection process uses periodic alternation between proppant-free fluid slugs and proppant-carrying fluid slugs. This periodic action creates a repeating pattern of channels and pillars throughout the fracture, ensuring both structural support at regular intervals and continuous flow paths that connect to the wellbore
4Reliability
If heterogeneous proppant placement is implemented through multiple slugging stages, then open space is maximized in the fracture, but the time and cost of the fracturing treatment increase
Solution Approach 1:
The alternating slug injection continues without interruption throughout the fracturing treatment, with proppant-free slugs and proppant-carrying slugs injected in continuous succession. This continuous alternation maximizes open space creation throughout the entire fracture length and height, ensuring optimal channel development while maintaining efficient treatment timing
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 hydraulic conductivity by maximizing open space in the fracture, allowing for superior fluid flow and more effective fracture clean-up, while optimizing proppant placement to increase well productivity.
Implementation Method 1
The slugs of proppant-carrying thickened fluid form pillars of proppant upon fracture closure
Data Source
AI summary
Hydraulic fracturing an individual reservoir fracturing layer of a subterranean formation to produce heterogeneous proppant placement is given in which pillars of proppant are placed such that the pillars do not extend the entire height of the fracture (for a vertical fracture) but are themselves interrupted by channels so that the channels between the pillars form pathways that lead to the wellbore. The method combines methods of introducing slugs of proppant-carrying and proppant-free fluids through multiple clusters of perforations within a single fracturing layer of rock, with methods of ensuring that the slugs exiting the individual clusters do not merge.