Downhole Rotor Density Measurement for Mud Pulse Control
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Solution Overview
Problem
Existing mud pulse telemetry systems face challenges in accurately adjusting pressure pulse settings due to variations in mud properties like flow rate and density, which can lead to excessive pressure or damage, necessitating precise downhole mud property measurements.
Innovation Solution
A method and system utilizing a downhole rotor with adjustable brake torque to measure drilling fluid density by comparing rotor speeds in different torque states, allowing for accurate determination of mud density and flow rate, thereby adjusting pulser settings for optimal signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mud pulse telemetry systems operate without precise downhole mud property measurements, then the system structure remains simple, but the signal strength becomes inconsistent and damage may occur due to excessive pressure pulses
Solution Approach 1:
The drilling fluid itself serves as the measurement medium by causing the downhole rotor to rotate. The rotor speed, influenced by fluid density and flow rate, provides self-contained measurement capability without requiring external measurement equipment, thereby improving reliability while avoiding additional system complexity
Solution Approach 2:
The downhole rotor serves multiple functions: it acts as both a telemetry power source (converting fluid flow to rotational energy) and a measurement device (providing density and flow rate data). This multi-functionality resolves the contradiction by integrating measurement capability into existing system components rather than adding separate measurement equipment
2Object-affected harmful factors
If pressure pulse settings are adjusted without accurate mud density measurements, then the pulser settings remain fixed, but excessive pressure pulses may cause damage
Solution Approach 1:
The patent replaces complex mechanical density measurement equipment with a rotational dynamics approach. By measuring rotor speed and applying brake torque, the system derives density information from mechanical rotation characteristics, achieving accurate measurement while using simpler, more reliable mechanical components already present in the telemetry system
Solution Approach 2:
The system establishes a feedback loop where rotor speed measurements are continuously monitored, processed to determine mud density, and used to adjust pulser settings in real-time. This closed-loop control prevents excessive pressure pulses by adapting to changing mud properties, thereby preventing damage while maintaining measurement precision
3Measurement precision
If downhole rotor speed is measured without applying brake torque, then the measurement system remains simple, but the rotor speed varies with flow rate making density determination inaccurate
Solution Approach 1:
The system changes the operational parameter of the rotor from free-spinning to brake-controlled rotation. By applying a known brake torque and measuring the resulting rotor speed, the system transforms the measurement from direct speed reading to a controlled rotational dynamics measurement, enabling accurate density determination through the relationship between torque, speed, and fluid properties
Solution Approach 2:
The patent transitions from static measurement concepts to dynamic measurement by actively controlling rotor deceleration through brake torque. The system measures rotor speed under controlled deceleration conditions, using the dynamic response to fluid flow and applied torque to derive density information, thereby improving precision while managing system complexity through controlled dynamics
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
Enables precise adjustment of pulser settings based on real-time mud properties, ensuring consistent signal strength and preventing damage, while facilitating accurate downhole operations like acoustic logging and mud pulse telemetry.
Implementation Method 1
The drilling fluid is flowed through the drill string in the wellbore causing the downhole rotor to rotate relative to the drill string
Implementation Method 2
A first brake torque is applied to the downhole rotor to place the downhole rotor in a first state
Implementation Method 3
A first downhole rotor speed of the downhole rotor having the drilling fluid flowing therethrough is measured with the downhole rotor in the first state
Implementation Method 4
A density of the drilling fluid is determined from the measured first downhole rotor speed, and the determined applied first brake torque
Data Source
AI summary
A system and method of determining a density of a drilling fluid in a wellbore. The system includes a drill string in the wellbore, the drill string including a downhole rotor. A drilling fluid flowing through the drill string in the wellbore causes the downhole rotor to rotate relative to the drill string. A brake is configured to apply a first brake torque to the downhole rotor to place the downhole rotor in a first state. A torque measurement system is configured to determine the applied first brake torque. A rotor speed measurement system is configured to measure a first downhole rotor speed of the downhole rotor having the drilling fluid flowing therethrough with the downhole rotor in the first state. A processor is configured to determine a density of the drilling fluid from the measured first downhole rotor speed, and the determined applied first brake torque.