Compound Grease Coating for Dissolvable Downhole Plugs
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Solution Overview
Problem
Current coatings for dissolvable magnesium alloy plugs in the oil and gas industry fail to maintain mechanical integrity during hydraulic fracturing due to conflicting requirements of premature disintegration or non-dissolution, and are sensitive to downhole conditions like temperature and fluid salinity, leading to inefficiencies and operational challenges.
Innovation Solution
A compound grease coating comprising an activation layer, a first grease layer with NLGI 200-250 consistency, and a second grease layer with NLGI 280-320 consistency, applied non-uniformly onsite, forming a transition zone that protects the plug from premature dissolution for 6-24 hours and allows controlled degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a dissolvable magnesium alloy plug is used to temporarily block the wellbore during hydraulic fracturing, then the plug can quickly disappear after fracturing by dissolving in produced fluids, but the plug may experience premature disintegration or fail to dissolve at all due to conflicting dissolving rate requirements
Solution Approach 1:
The coating system is segmented into multiple layers with different functions: a polymer spray coating layer provides initial protection and controlled dissolution, while a grease coating layer provides secondary protection. This segmentation allows each layer to contribute differently to the overall dissolution control, enabling the plug to maintain mechanical integrity during operation while ensuring reliable dissolution after fracturing.
Solution Approach 2:
The invention uses a composite coating system combining polymer materials and grease materials on the dissolvable magnesium alloy substrate. This composite structure leverages the complementary properties of both materials: the polymer provides controlled dissolution characteristics while the grease provides additional protection and lubrication, together resolving the contradiction between maintaining strength and enabling dissolution.
2Productivity
If the dissolving rate of the dissolvable magnesium alloy is increased to enable rapid removal after hydraulic fracturing, then the plug can be quickly removed, but the plug loses mechanical strength during operation and disintegrates prematurely
Solution Approach 1:
The coating is applied preliminarily to the dissolvable plug before deployment into the wellbore. This preliminary protective action ensures that the plug maintains its mechanical strength during the high-stress hydraulic fracturing operation, and only after the fracturing is complete does the coating begin to dissolve, enabling rapid removal without compromising operational strength.
Solution Approach 2:
The invention changes the dissolution parameters by introducing coatings with controlled dissolution rates. The polymer spray coating and grease coating layers are designed to dissolve at controlled rates that prevent premature disintegration during operation while enabling rapid dissolution after fracturing, thus resolving the contradiction between maintaining strength and achieving fast removal.
3Adaptability or versatility
If downhole fluid salinity and temperature vary significantly, then operators must use flow-back water and produced water instead of freshwater, but this requires specific grades of dissolvable magnesium alloy and respective compatible polymer coatings for each well
Solution Approach 1:
The grease coating layer serves multiple functions: it provides protection during conveyance and operation, acts as a lubricant, and offers a secondary dissolution control mechanism. This multi-functionality reduces the need for highly specialized coatings for each specific well condition, as the grease layer provides robust protection and controlled dissolution across a range of salinity and temperature conditions.
Solution Approach 2:
The invention uses consumable coating materials (polymer spray coating and grease coating) that are designed to be temporary and disposable, dissolving after they have served their protective function. This approach is more cost-effective and simpler than developing and maintaining multiple permanent coating formulations for different well conditions, as the coatings are applied once and then naturally dissolve when no longer needed.
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 compound coating effectively maintains mechanical integrity and controlled degradation of dissolvable components, enabling reliable operation and efficient removal of downhole tools, reducing the need for pre-fabricated coatings and inventory management, and accommodating varying well conditions.
Implementation Method 1
prevent downhole oil and hydraulic fracturing proppants from 'wrapping' the dissolvable magnesium alloy of the dissolvable plug, which isolates the dissolvable magnesium alloy from contacting waterborne downhole fluids
Implementation Method 2
the dissolvable plug is dissolved in the downhole fluids. The dissolvable plug includes a plug formed with all dissolvable components or plug formed with at least one dissolvable component to collapse and release the plug from set position in the borehole
Data Source
AI summary
A coating protects a dissolvable component of a downhole tool, so that the dissolvable component can be deployed to a desired downhole location, perform under high stress for fracturing operations, and be efficiently dissolved after the fracturing operations are completed. The present invention elevates known greases for this functionality usually performed by complex factory fabricated polymer and metal coatings. The coating includes an activation layer, a first grease layer, and a second grease layer. The first grease layer and the second grease layer have differential grease layer consistency ranges and thickness rages. The coating includes non-uniform layers of manually applied greases onsite to control degradation of the component substrate as effectively as factory coatings pre-fabricated on the components.