Cooling Fluid Injection for Hydraulic Fracture Initiation
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Solution Overview
Problem
Hydraulic fracture stimulation in complex tight oil and gas reservoirs often fails to initiate fractures within the pressure limits of modern equipment due to high rock competency, in-situ stresses, and stress contrasts, resulting in significant costs without enabling production.
Innovation Solution
Injecting a cooling fluid into the near-wellbore zone to reduce fracture initiation pressure, followed by a frac fluid with a proppant, using coiled tubing and isolation devices to efficiently deliver the fluids and maintain temperature gradients, thereby lowering the compressive stress concentration and initiating hydraulic fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydraulic fracturing is applied to tight oil and gas reservoirs, then production can be enabled in fracturable formations, but it is impossible to initiate fractures in highly competent rock with large in-situ stresses due to equipment pressure limits
Solution Approach 1:
The patent applies preliminary action by injecting cooling fluid into the formation before the main fracturing operation. This pre-cooling step reduces the rock temperature and thermal stress in the near-wellbore zone, lowering the fracture initiation pressure before the high-pressure frac fluid is injected. The cooling fluid is injected through coiled tubing to a targeted depth, creating a favorable stress state that enables subsequent fracture initiation within equipment pressure limits.
Solution Approach 2:
The patent changes the temperature parameter of the formation by injecting cooling fluid at a lower temperature than the formation. This temperature change induces thermal contraction and reduces the in-situ stress in the near-wellbore zone, thereby reducing the fracture initiation pressure. The temperature differential between the cooling fluid and formation is used as a controllable parameter to achieve the desired stress reduction.
2Stress or pressure
If cooling fluid is injected to reduce fracture initiation pressure, then fracture initiation becomes possible within equipment pressure limits, but additional equipment and process complexity is required
Solution Approach 1:
The patent applies multi-functionality by using the same coiled tubing injection system for both cooling fluid injection and frac fluid injection. The coiled tubing unit serves dual purposes: first as a cooling fluid delivery system to reduce fracture initiation pressure, and then as a frac fluid delivery system for the actual fracturing operation. This eliminates the need for separate injection equipment for each function, reducing overall system complexity.
Solution Approach 2:
The cooling fluid acts as an intermediary substance that mediates between the equipment pressure limits and the rock fracture initiation requirement. By introducing this intermediate cooling step, the system can achieve the necessary stress reduction without requiring the frac fluid injection system to exceed equipment pressure capabilities. The cooling fluid transfers thermal energy to modify the stress state, enabling the subsequent fracturing operation.
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
Significantly reduces the hydraulic fracture initiation pressure, allowing for effective fracture initiation and propagation in previously unfracturable zones, enhancing production from tight reservoirs by creating permeable channels for fluid flow.
Implementation Method 1
injecting a cooling fluid into a near-wellbore zone to cool the near-wellbore zone and thereby reduce fracture initiation pressure
Data Source
AI summary
Method and systems and workflows are provided that cool a near-wellbore zone by injection of cooling fluid for reducing hydraulic fracture initiation (breakdown) pressure.