Drill String Rotation and Mud Pumping Control for BHP Stability
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Solution Overview
Problem
In subterranean drilling, maintaining consistent bottom hole pressure (BHP) is challenging, especially when drilling deep and extending the drill string, as existing methods require stopping mud flow or using complex valve systems, which can lead to inefficiencies and risks of formation fluid influx or fracturing.
Innovation Solution
A method where the rate of drilling mud circulation is linked to the speed of drill pipe rotation, adjusting the mud pumping rate in response to changes in rotation speed to maintain optimal BHP, using electronic controllers to automatically regulate both the pump speed and drill string rotation, and incorporating an adjustable choke in the annulus return line to manage fluid pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the drill string is extended by disconnecting and reconnecting sections, then the borehole can be drilled deeper, but the mud flow must be stopped which increases the risk of formation fluid influx and reduces drilling efficiency
Solution Approach 1:
The drill string is divided into multiple sections that can be independently connected and disconnected. Each section has its own side bore with valve and pump capability, allowing modular extension without stopping overall mud circulation. The side bores are segmented and can be activated independently based on which section is being connected.
Solution Approach 2:
Side bores with valves and pump connections are pre-installed in each drill string section before drilling begins. This preliminary preparation allows immediate activation of alternative mud flow paths when sections need to be connected, eliminating the need to stop circulation during extensions.
2Productivity
If mud is pumped continuously through the drill string during extension, then drilling efficiency is maintained, but complex valve systems and side bores are required which increase device complexity
Solution Approach 1:
The main bore and side bores are designed with universal valve assemblies that can switch between different flow paths. The same valve mechanism serves both to control mud flow during normal drilling and to redirect flow during section connections, reducing the need for separate specialized components.
Solution Approach 2:
Each drill string section is equipped with self-contained pump connections and valve systems that can independently control mud flow through that section. This self-service capability allows any section to maintain circulation independently, simplifying the overall control system compared to a centralized complex valve arrangement.
3Reliability
If the pump speed is increased to maintain BHP during drill string extension, then pressure control is improved, but energy consumption increases
Solution Approach 1:
The pump speed is dynamically adjusted based on real-time monitoring of BHP and the drilling conditions. During section extensions, the system automatically modulates pump speed to maintain target pressure, avoiding constant high-speed operation and reducing unnecessary energy consumption while ensuring pressure control when needed.
Solution Approach 2:
A feedback control system continuously monitors bottom hole pressure and automatically adjusts pump speed in response to pressure deviations. This closed-loop control ensures BHP is maintained within acceptable ranges during extensions without requiring excessive pump speed, optimizing energy usage while maintaining pressure control.
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
This approach allows for improved control of BHP, reducing the risk of formation fluid influx or fracturing, enabling continuous drilling with reduced frictional effects and maintaining stability during drill string extensions, thus enhancing drilling efficiency and safety within tight formation pressure gradients.
Implementation Method 1
the rate of pumping of the drilling fluid is increased as the speed of rotation of the drill string is decreased, and the rate of pumping of the drilling fluid is decreased as the speed of rotation of the drill string is increased
Implementation Method 2
incorporating an adjustable choke in the annulus return line to manage fluid pressure
Implementation Method 3
The mud flow also serves to cool the drill bit, and to pressurise the borehole, thus substantially preventing inflow of fluids from formations penetrated by the drill string from entering into the borehole
Data Source
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AI summary
A method of drilling a subterranean bore hole comprising a) pumping a drilling fluid down a drill string, the drill string having a drill bit at an end thereof, b) rotating the drill string about its longitudinal axis to that the bit forms bore hole in the ground, the method further comprising the steps of: c)changing the rate of pumping of the drilling fluid into the drill string in response to a change in the speed of rotation of the drill string, and / or changing the speed of rotation of the drill string in response to a change in the rate of pumping of the drilling fluid into the drill string.