Dynamic Viscosity Fracturing Fluid for Proppant Transport
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Solution Overview
Problem
Proppant settling issues in fracturing fluids, particularly in low viscosity fluids used for tight gas reservoirs, lead to costly pumping challenges and equipment damage due to high specific gravity proppants and insufficient viscosity to suspend proppants during transport, resulting in reduced fracture area and increased treating pressures.
Innovation Solution
A fracturing method using a mixture of water, a viscosifying polymer, and a crosslinking agent to create a fracturing fluid with high viscosity at the wellhead, which decreases rapidly upon entering the reservoir, minimizing proppant settling and maintaining effective proppant transport while reducing formation damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If low viscosity fluids are used for fracturing tight gas reservoirs, then fracture area is increased and formation damage is reduced, but proppant settling occurs and transporting proppant becomes difficult
Solution Approach 1:
The fracturing fluid uses a dynamic viscosity profile that changes over time and position: high initial viscosity at the wellhead for proppant suspension, transitioning to low viscosity distally in the fracture for optimal fracture geometry. This is achieved through time-dependent crosslinking mechanisms where viscosity evolves from minutes to hours after injection.
Solution Approach 2:
Different viscosity characteristics are applied to different locations within the fracturing system: high viscosity near the wellhead and pump equipment for reliable proppant transport, and low viscosity in the distal fracture regions for maximum fracture area and minimal formation damage. This spatial differentiation resolves the contradiction between transport reliability and fracture area.
2Reliability
If high viscosity fracturing fluids are used, then proppant transport is improved and settling is minimized, but fracture area is reduced and formation damage increases
Solution Approach 1:
The fluid transitions from high viscosity during injection to low viscosity after treatment, allowing both reliable proppant transport during the fracturing operation and optimal fracture geometry afterward. This temporal transformation eliminates the need to choose between high and low viscosity for different stages.
Solution Approach 2:
The fracturing fluid is prepared with high viscosity before injection to ensure reliable proppant transport, then undergoes a controlled viscosity reduction after completing its transport function. This preliminary high viscosity state is maintained only as long as needed for proppant delivery.
3Strength
If high specific gravity proppants are used, then fracture conductivity is improved, but proppant settling increases and transport difficulty increases
Solution Approach 1:
The high viscosity fracturing fluid acts as a counterbalancing force against the gravitational settling of high specific gravity proppants. The viscous drag force generated by the fluid counteracts the gravitational force on the dense proppant particles, enabling their transport without settling in the horizontal wellbore section.
4Object-affected harmful factors
If low viscosity fracturing fluids are used, then formation damage is reduced, but proppant settling occurs and pump failures increase
Solution Approach 1:
The fracturing fluid exhibits dynamic viscosity characteristics: high viscosity during the pumping phase to prevent proppant settling and maintain pumping reliability, then low viscosity after treatment to minimize formation damage. This temporal transformation allows both conflicting requirements to be satisfied at different times.
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 method effectively transports proppants to the perforation site with minimal settling, reducing pump failures and equipment damage, and optimizing fracture area by maintaining high viscosity only where needed, thus enhancing fluid efficiency and fracture conductivity.
Implementation Method 1
an aqueous fluid, a hydratable polymer, a crosslinking agent and proppant are mixed together
Implementation Method 2
the apparent viscosity of the fluid decreases distally from the entrance site of the reservoir
Implementation Method 3
transporting proppant into the wellhead... the viscous nature of the fracturing fluid enables the fluid to transport the proppant to the perforation sites in the wellbore while minimizing settling
Implementation Method 4
Increased viscosity at the surface protects the surface equipment when pumping the suspended proppant into the wellhead
Data Source
AI summary
Subterranean formations are subjected to hydraulic fracturing with an aqueous fracturing fluid having guar or a derivative thereof, a borate crosslinking agent and proppant. The fracturing fluid is prepared in a blender and then pumped into the wellbore through an entrance site. The apparent viscosity of the fluid decreases distally from the entrance site such that (i) the apparent viscosity of the fracturing fluid 100 feet from the entrance site is less than 10 percent of the apparent viscosity of the fracturing fluid at the entrance site; (ii) the apparent viscosity of the fracturing fluid 15 minutes after introduction into the entrance site is less than 15% of the apparent viscosity of the fracturing fluid at the entrance site; or (iii) the apparent viscosity of the fracturing fluid is less than 10 cP within 15 minutes after being introduced through the entrance site.