Electromagnetically Transparent Plug for Downhole Logging Tool Collars
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Solution Overview
Problem
Downhole resistivity measurement tools face challenges in maintaining differential pressure while ensuring electromagnetic field transparency through conductive tubular collars, requiring resilient yet electromagnetically transparent plugs for slots in the collar to prevent field attenuation.
Innovation Solution
A plug assembly comprising a plug body, inner retainer, and outer retainer, coupled together with seals to maintain pressure differential and electromagnetic transparency, is installed within slots in the tubular member to accommodate antenna elements, ensuring continuous measurement during drilling operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slots are formed through the collar wall to allow electromagnetic field transmission, then electromagnetic field transparency is improved, but pressure containment is worsened
Solution Approach 1:
The plug is divided into multiple functional segments: a body portion for electromagnetic transparency, a sealing portion with radially extending fingers for pressure containment, and retention features for secure mounting. This segmentation allows each portion to specialize in one function, resolving the contradiction between field transmission and pressure containment.
Solution Approach 2:
The plug employs composite construction combining conductive materials (for electromagnetic transparency) with resilient sealing materials (for pressure containment). The sealing fingers may be made of elastomeric or flexible materials that deform to seal against the slot walls while the body portion remains electromagnetically transparent.
2Stress or pressure
If resilient sealing material is used to maintain pressure differential, then pressure containment is improved, but electromagnetic transparency is worsened
Solution Approach 1:
The plug is divided into multiple functional segments: a body portion for electromagnetic transparency, a sealing portion with radially extending fingers for pressure containment, and retention features for secure mounting. This segmentation allows each portion to specialize in one function, resolving the contradiction between field transmission and pressure containment.
Solution Approach 2:
Different regions of the plug have different material properties: the body portion is made electromagnetically transparent while the sealing fingers use resilient material. This local differentiation of material properties allows the plug to simultaneously achieve pressure containment and electromagnetic transparency without compromising either function.
3Device complexity
If a simple plug design is used for slots, then device complexity is reduced, but installation reliability is worsened
Solution Approach 1:
The plug includes pre-formed retention features such as tabs, protrusions, or engagement structures that automatically secure the plug to the slot during installation. These features are built into the plug design beforehand, ensuring reliable retention without requiring complex additional components or multi-step installation procedures.
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 plug assembly effectively seals slots in the tubular collar, maintaining pressure differential and preventing electromagnetic field attenuation, allowing for accurate resistivity measurements and formation analysis during drilling.
Implementation Method 1
the electromagnetic field would be attenuated if not blocked altogether from entering the surrounding formation without the slots
Data Source
AI summary
A plug for use in a downhole tool collar allows a seal between the inside and outside of the collar. The plug provides an electromagnetically transparent window through which the signals from the measurement device may propagate to or from the surrounding formation. The plug assembly includes an inner retainer, an outer retainer, and a plug. The inner retainer may be inserted into the inside of a slot formed in the collar. The inner retainer may have a concave inner surface to match the cylindrical inner surface of the collar. Likewise, the outer collar may be inserted into the outside of the slot, and may have a convex outer surface to match the cylindrical outer surface of the collar. The plug may fit into slots in the inner and outer retainers and be held in place within the slot.