Downhole Tool String Spacer Placement for Mud Cake Friction

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Solution Overview

Problem

Downhole tools face movement impediments and unpredictable friction due to mud cake formation in boreholes, leading to reduced productivity and potential for stuck tools, as the mud cake hardens and increases frictional resistance during drilling and retrieval operations.

Innovation Solution

A manufacturing system that uses a design device to determine contact parameters between the downhole tool string and mud cake, optimizing the placement of spacers such as standoffs and rollers to reduce contact forces by iteratively adding spacers at high-contact-force points and replacing standoffs with rollers where feasible, based on models of tool, mud cake, and borehole properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the downhole tool string is deployed in a borehole with mud cake formation, then the tool can perform measurements and operations, but the mud cake increases frictional resistance and impedes tool movement

Engineering Contradiction:

Improvetool movement predictabilityVSAvoidfrictional resistance from mud cake

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces spacers as intermediary elements between the downhole tool string and the mud cake. These spacers (including standoffs and rollers) act as mediators that reduce direct contact between the tool and mud cake, thereby minimizing frictional resistance and improving tool movement predictability while allowing the tool to remain deployed in the borehole

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If spacers are added to reduce contact force with mud cake, then frictional resistance decreases, but the device complexity increases

Engineering Contradiction:

Improvecontact force with mud cakeVSAvoidspacer placement configuration

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies local quality by placing spacers at specific locations along the tool string where contact force with mud cake is highest. Rather than uniformly distributing spacers throughout the entire tool string, the design selectively positions them at critical contact points identified through contact force analysis, thereby reducing overall frictional resistance while minimizing the total number of spacers needed

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the spacer system into different types (standoffs and rollers) with different functions. Standoffs provide structural support and spacing, while rollers reduce friction through rolling contact. This segmentation allows the system to address multiple aspects of the mud cake interaction problem using specialized components rather than a single uniform solution

Inventive Principle:

Principle #1Segmentation

3Object-affected harmful factors

If standoffs are replaced with rollers at high contact force points, then frictional resistance further decreases, but manufacturing complexity increases

Engineering Contradiction:

Improvefrictional resistanceVSAvoidspacer assembly process

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent introduces dynamics by replacing static standoff elements with dynamic roller elements at high contact force points. The rollers can rotate to accommodate varying contact conditions and tool movement requirements, providing adaptive friction reduction. This dynamic approach allows the system to optimize friction reduction in real-time while maintaining a relatively simple manufacturing process using standardized roller components

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10125545B2Placement of stabilizers, standoffs, and rollers on a downhole tool string

Publication Date: 2018.11.13 SCHLUMBERGER TECH CORP

AI summary

A manufacturing system that manufactures a downhole tool string, which includes a model that describes relationship between properties of the downhole tool string, properties of a borehole, properties of a formation, and properties of a mud cake formed on a surface of the borehole and a design device that iteratively determines contact parameters that describe one or more contact points expected between the downhole tool string and the mud cake based at least in part on the model, in which the contact parameters comprise contact force expected at each of the contact points, adjusts the properties of the downhole tool string to add a spacer at one of the contact points associated with highest contact force, and indicates location, type, or both of the spacer to enable the manufacturing system to attach the spacer to the downhole tool string before deployment of the downhole tool string in the borehole.