Ball Seat Milling for Single-Trip Well Refracturing
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Solution Overview
Problem
In well refracturing operations, existing technologies face challenges in isolating individual open ports in a wellbore with stuck ball seats, which impedes progress and increases costs due to the need for multiple trips and potential tool interference.
Innovation Solution
A bottom hole assembly equipped with a fluid motor driven mill, ported sub, and resettable packer is used to mill out ball seats and isolate specific open ports for focused refracturing, allowing for a single trip to prepare the wellbore and restore production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional sliding sleeve valves with ball seats are used for fracturing, then multiple zones can be fractured sequentially, but the ball seats remain in the wellbore and impede progress of subsequent tools and prevent effective refracturing
Solution Approach 1:
The milling tool extracts and removes the ball seats from the sliding sleeves by milling them out, effectively taking out the obstructing elements that prevented refracturing. This allows subsequent tools to pass through the wellbore and enables refracturing operations to proceed effectively.
Solution Approach 2:
The ball seats are milled out in advance before the refracturing operation begins. This preliminary removal of obstacles prepares the wellbore for subsequent refracturing activities, ensuring that tools can reach desired locations and refracturing can be performed effectively.
2Reliability
If multiple trips are required to remove ball seats and prepare for refracturing, then complete isolation and refracturing can be achieved, but costs increase and time is lost
Solution Approach 1:
The milling operation and ball seat removal are combined into a single trip operation. The milling tool performs both the milling function and ball seat removal in one journey down the wellbore, eliminating the need for separate trips and reducing overall time loss while maintaining reliable isolation.
3Ease of operation
If ball seats are not removed, then sliding sleeve valves remain functional, but they prevent tools from reaching desired locations and isolate zones that cannot be refractured
Solution Approach 1:
The ball seats are extracted and removed from the wellbore through the milling operation. This eliminates the harmful impediment that was preventing tools from progressing to desired locations, thereby improving ease of operation for subsequent refracturing activities.
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 method enables efficient isolation and refracturing of specific ports within a single trip, reducing costs and avoiding tool interference, thereby enhancing the effectiveness and efficiency of wellbore preparation and production.
Implementation Method 1
a fluid motor driven mill that mills out ball seats
Implementation Method 2
a resettable packer... isolate the open port
Data Source
AI summary
A well that has a plurality of sliding sleeves used to originally fracture multiple zones with balls of increasing size dropped on balls seats to sequentially open ports for fracturing in a direction toward the well surface is refractured. The method involves using a bottom hole assembly (BHA) that has a fluid motor driven mill that mills out ball seats and has with it a ported sub and a resettable packer. Once the lowermost ball seat is milled out a ball is dropped into the BHA to isolate the fluid motor and open a ported sub below a resettable packer. The dropped ball also enables a collet to latch an open sleeve to give a surface signal that the BHA is located properly for packer deployment so that the refracturing can begin through the coiled tubing string that can support the BHA or in a surrounding annular space.