Alkali Silicate Induced Shale Creep for Well Abandonment
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Solution Overview
Problem
Current well abandonment techniques in the oil and gas industry are costly and time-consuming due to the limitations of Ordinary Portland Cement (OPC) and the slow natural deformation of shale formations, which require extensive drilling operations to create effective barriers in annular gaps.
Innovation Solution
The use of alkali silicates, such as lithium silicate, to induce creep deformation in shale formations, creating a reliable and high-strength hydraulic seal that accelerates the formation of a permanent barrier without the need for extensive drilling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ordinary Portland Cement is used as plugging material, then barrier formation is achieved, but the process is time-consuming and costly requiring drilling rig operations
Solution Approach 1:
The invention extracts and removes the casing string from the wellbore, exposing the open hole formation directly. This eliminates the need for complex milling operations and allows direct placement of abandonment plugs into the formation, significantly reducing the time and cost associated with drilling rig operations while maintaining reliable barrier formation.
2Ease of manufacture
If casing milling and pulling is performed to expose open hole formations, then abandonment plugs can be set, but the operation becomes time-consuming and costly
Solution Approach 1:
The invention performs preliminary action by removing the casing string before the abandonment operation. By extracting the casing in advance, the wellbore is already prepared with exposed open hole formation, eliminating the need for time-consuming milling operations during the abandonment process itself and allowing direct plug placement.
3Reliability
If OPC is used as barrier material, then zonal isolation is created, but the material is brittle and has low tensile strength
Solution Approach 1:
The invention employs composite materials by combining abandonment plugs with formation gravel and native formation materials. This composite structure leverages the strength and durability of the formation materials while the plug provides the sealing function, creating a more robust barrier system with improved tensile strength and resistance to brittle failure compared to OPC alone.
4Reliability
If OPC is used for plugging, then barrier is formed, but CO2 emissions are significantly increased
Solution Approach 1:
The invention replaces expensive, environmentally harmful OPC with a more sustainable approach using formation-based materials and gravel packs. This substitution eliminates the high CO2 emissions associated with OPC production while providing effective plugging functionality through the composite barrier system, reducing the environmental footprint of well abandonment operations.
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
Alkali silicates significantly reduce the time required for shale deformation and enhance the sealing properties, forming a stronger bond with the casing that can withstand higher pressures, thus providing an efficient and cost-effective solution for well abandonment.
Implementation Method 1
Certain shales 12 have the ability to plastically deform and 'creep' into wellbore and annular spaces 14 under certain pressure, temperature and fluid conditions
Implementation Method 2
lowering the near-wellbore stiffness of the rock accelerates the deformation and creep of the shale into an uncemented annular space
Data Source
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AI summary
A method and agent to induce accelerated creep deformation of shale rock formations in the annular gap between a shale formation and non-cemented sections of a casing string have been developed. A fluid containing alkali silicate or a modified alkali silicate is added to the annular space between the shale rock formation and the casing string. The alkali silicate promotes creep deformation of the shale rock, effectively closing the annulus surrounding the casing. It has been found lithium silicate provides the strongest shale-casing bond and is the presently preferred material for closing abandoned wells.