Clean Out Sub Valve Spool for Debris Removal
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Solution Overview
Problem
Current drilling technologies face limitations in achieving high enough pump rates and annular velocities for effective debris removal in wells due to maximum flow rate constraints, particularly in horizontal wells, where debris like frac sand and formation pieces need to be cleared, often requiring diversion of drilling fluid beyond the motor's capacity.
Innovation Solution
A clean out sub with annular circulation ports that can open and close in response to differential pressure, allowing increased pump rates and annular velocities by diverting fluid from the drill string to the annulus, featuring a valve spool mechanism that reacts to flow rate changes and pressure imbalances, ensuring reliable operation and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If drilling fluid flow rate is increased to improve debris removal in the annulus, then annular velocity and debris removal efficiency are improved, but the motor flow rate limit is exceeded causing excessive back pressure
Solution Approach 1:
The tool segments the drilling fluid flow into two separate paths: one through the motor (maintaining motor flow rate limits) and another through annular circulation ports (enabling high annular velocity for debris removal). This segmentation allows independent optimization of each flow path without compromising the other.
Solution Approach 2:
The clean out sub acts as an intermediary device between the drill string and the annulus. It includes a valve spool with a piston that responds to differential pressure to open or close annular circulation ports, mediating the flow distribution between motor and annulus based on downhole conditions.
2Quantity of substance
If a ball and shiftable flow control device are used to divert fluid to the annulus, then annular flow rate is increased, but the tool cannot be returned to full flow through the motor
Solution Approach 1:
The valve spool system is self-actuating through differential pressure sensing. When annular back pressure increases, the pressure differential automatically opens the annular circulation ports. When back pressure decreases, the system automatically closes the ports and returns to full motor flow, eliminating the need for manual intervention or permanent modification.
Solution Approach 2:
The flow control mechanism is dynamic rather than static. The valve spool continuously adjusts the annular circulation port opening based on real-time differential pressure conditions, allowing the system to adapt between full motor flow and high annular flow modes as needed.
3Productivity
If a fracture disc or release means is used to divert fluid, then annular circulation is achieved, but the system lacks reversibility
Solution Approach 1:
The system incorporates feedback through differential pressure sensing across the orifice. The valve spool position is continuously adjusted based on feedback from the pressure differential between the motor side and annulus side, ensuring reliable and reversible flow diversion that responds to actual downhole conditions.
4Productivity
If pump rate is increased to improve hole cleaning, then annular velocity increases, but surface pressure exceeds pump capacity
Solution Approach 1:
The system segments the total pump capacity into two functional components: motor flow (maintained within motor limits) and annular circulation flow (optimized for hole cleaning). This allows the surface pump to operate at high total flow rates without exceeding motor flow rate limits or surface pressure capacity.
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 increased pump rates and annular velocities for improved debris removal without exceeding motor flow limits, maintaining port openness for efficient hole cleaning and protecting equipment from high pressures, with hysteresis allowing operation in various well conditions.
Implementation Method 1
The valve spool responds to differential pressure created across a fixed orifice. The force created by the differential pressure pushes the valve spool into a compression spring.
Implementation Method 2
This creates a large force imbalance on the valve spool which quickly overwhelms the spring force and causes the spool to rapidly shift revealing the annular circulation ports.
Implementation Method 3
The force created by the differential pressure pushes the valve spool into a compression spring.
Implementation Method 4
The valve spool position is only affected by increasing or decreasing the flow rate and corresponding pressure drop created by the orifice.
Implementation Method 5
The annular circulation ports are angled uphole in a swirl arrangement to better lift debris off the bottom of the hole.
Implementation Method 6
The annular circulation ports are angled uphole in a swirl arrangement to better lift debris off the bottom of the hole.
Implementation Method 7
When the pressure to the spring cavity is shut off, the pressure area of the valve spool downhole of the orifice is reduced substantially because the spring cavity is vented to annulus through a bleed hole.
Data Source
AI summary
A clean out sub for use in a drill string having a tool body with a cavity for passage of drilling fluid and annular fluid circulation ports extending through the tool body, a valve spool is positioned within the tool body cavity having a reduced diameter orifice, a compression spring is located within the tool body cavity adjacent the valve spool, wherein a drop in fluid pressure created by the orifice imparts a downhole force on the valve spool and at a predetermined force overcomes a set resistive force of the compression spring thereby moving the valve spool to open the annular fluid circulation ports.