SAGD Dilation Zone Creation via Stress Field Modification
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Solution Overview
Problem
Conventional hydraulic fracturing methods for SAGD well stimulation lack proactive control over fracture orientation and often require sacrificial wells, leading to inefficient communication between SAGD wells and complications in steam conformance, especially in formations with local inhomogeneities.
Innovation Solution
A method that creates a laterally-continuous, vertically-oriented dilation zone connecting SAGD wells by altering the original stress field using poroelastic and thermoelastic mechanisms, without the need for sacrificial fractures, to promote uniform dilation along the well length, facilitating better steam conformance and viscosity reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional hydraulic fracturing is used to stimulate SAGD wells, then fracture formation occurs, but the fracture orientation cannot be proactively controlled and follows the plane perpendicular to the least resistance instead of the desired vertical orientation connecting SAGD wells
Solution Approach 1:
The patent applies preliminary action by first modifying the in-situ stress field through controlled injection at pressures between the minimum and maximum principal stresses, which pre-conditions the formation to favor vertical fracture propagation before the main stimulation phase. This preliminary stress modification ensures that subsequent fractures follow the desired vertical orientation connecting SAGD wells rather than following the path of least resistance
Solution Approach 2:
The patent changes the stress state parameters by injecting fluids at specific pressure ranges (between Smin and Smax) to alter the principal stress orientations temporarily. This parameter change creates a window where vertical fractures become the path of least resistance, enabling proactive control over fracture orientation without requiring sacrificial wells or complex drilling operations
2Reliability
If sacrificial wells are used to create fractures perpendicular to the maximum stress for uniform communication, then inter-well communication improves, but drilling and completion costs increase and steam conformance becomes complicated
Solution Approach 1:
The patent extracts the unnecessary element of sacrificial wells from the system by demonstrating that vertical fractures can be created directly in the production well pair through controlled stress modification. This eliminates the need for additional sacrificial wells, reducing drilling and completion complexity while maintaining reliable inter-well communication through the dilation zones
Solution Approach 2:
The patent enables the SAGD well pair to serve itself by creating the necessary communication channels through controlled injection into the existing wells. The wells stimulate their own formation to create vertical dilation zones that provide the desired uniform communication, eliminating the need for external sacrificial wells to facilitate the process
3Productivity
If conventional hydraulic fracturing is used in formations with local inhomogeneities, then fracture propagation occurs, but uniform propagation along the well length cannot be achieved without segmenting the well length
Solution Approach 1:
The patent applies local quality by allowing the injection pressure and fracture propagation characteristics to vary locally along the well length in response to formation inhomogeneities. The controlled stress modification creates conditions where dilation zones form uniformly along the entire well length, with each segment responding to its local formation properties while maintaining overall uniformity without requiring physical well segmentation
4Productivity
If steam is circulated through SAGD wells independently for 6 months or more to establish communication, then bitumen viscosity is reduced significantly, but the startup time is excessively long
Solution Approach 1:
The patent applies preliminary action by creating vertical dilation zones that establish communication channels between SAGD wells before full steam circulation begins. This preliminary channel creation allows steam to immediately access and heat the bitumen when circulation starts, eliminating the 6-month or longer waiting period normally required for communication establishment through independent steam circulation
Solution Approach 2:
The patent introduces dilation zones as intermediary structures that facilitate rapid communication establishment between SAGD wells. These dilation zones act as pre-formed conduits that allow steam to quickly establish effective communication and heat the bitumen, replacing the slow process of communication establishment through prolonged independent steam circulation
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 enables uniform and controlled dilation along the SAGD well length, enhancing steam communication and viscosity reduction, thereby accelerating the startup of SAGD production without the need for segmenting the well length or using sacrificial fractures.
Implementation Method 1
altering the original stress field using poroelastic and thermoelastic mechanisms
Implementation Method 2
altering the original stress field using poroelastic and thermoelastic mechanisms
Implementation Method 3
steam is injected into the reservoir, to heat up the bitumen
Implementation Method 4
heated or otherwise stimulated to reduce viscosity and promote extraction
Data Source
AI summary
A method is taught for creating a laterally-continuous, vertically-oriented dilation zone connecting the two SAGD wells. A method is taught for drilling and completing the SAGD wells in a formation, conditioning said wells to create a stress condition favorable for forming a dilation zone, injecting one or both of said two wells with a stimulant at pressures greater than the in-situ minimum stress of the formation to initiate the dilation zone connecting said SAGD wells and continuing stimulant injection into a first of said two wells while maintaining a target pressure at a second of said two wells to propagate the dilation zone homogenously along the well length.