Swelling Packer Bottom Hole Assembly for High-Rate Refracturing
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Solution Overview
Problem
The limited drift dimension of production packers in existing well systems restricts the size of service strings used for reperforating and refracturing, making it impractical to achieve desired frac rates due to high fluid velocities and pressure issues, leading to unsatisfactory production rates and potential erosion.
Innovation Solution
A bottom hole assembly with swelling packers and a bottom end anchor seal provides a larger drift dimension, isolates low-pressure casing from overpressure, and allows for single-trip reperforation and refracturing with a service string supporting a releasable plug and frac ports, utilizing location devices for precise tool placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a production packer with limited drift dimension is used, then the well can be sealed and produced, but the service string size is restricted making it impossible to achieve desired frac rates
Solution Approach 1:
The production packer is divided into two separate functions: the anchor packer remains in the well to provide sealing and support, while a separate BHA with swelling packers provides the large drift dimension needed for high-rate fracturing. This segmentation allows each component to be optimized for its specific function without compromise.
Solution Approach 2:
The swelling packers use a dynamic mechanism where the packer elements expand after deployment to increase the internal drift dimension. This allows the service string to be run with adequate clearance, enabling high frac rates of 50 barrels per minute or more without excessive pressure or fluid velocity.
2Productivity
If high frac rates are pumped through small diameter tubing, then fracturing can be achieved, but surface pumping horsepower requirements become impractical and pipe working pressure limits are exceeded
Solution Approach 1:
The internal diameter parameter of the service string is changed by using swelling packers that expand after deployment. This increases the flow area, reducing both the velocity and pressure required to achieve the desired frac rate, thereby avoiding excessive pumping horsepower requirements and pipe working pressure limits.
3Productivity
If high fluid velocities are used to achieve frac rates, then fracturing can be achieved, but serious erosion issues occur
Solution Approach 1:
The internal diameter parameter is increased through the swelling packer mechanism, which directly reduces fluid velocity for a given flow rate. This eliminates the erosion problem caused by high velocities while maintaining the required frac rate for effective fracturing.
4Productivity
If existing perforations are refractured, then production can be improved, but sand buildup occurs on the barrier isolating treated zones
Solution Approach 1:
The barrier function is extracted from the production packer and placed on the service string near the bridge plug. This repositioning allows frac sand to be contained near the treatment zone rather than building up on the barrier, eliminating the sand buildup problem while maintaining zone isolation.
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 effective reperforation and refracturing with larger service strings, reducing sand buildup and maintaining pressure protection, allowing for efficient fracturing operations and increased production rates without the need for multiple trips or milling out anchor packers.
Implementation Method 1
swelling packers that have a very low profile for run in before any swelling commences to allow a larger drift dimension internally
Implementation Method 2
spaced external seals that preferably set by swelling
Data Source
AI summary
A bottom hole assembly to enable reperforation and refracturing a cased hole has a bottom end anchor seal to allow a larger drift dimension in the zones to be perforated and fractured between spaced external seals that preferably set by swelling. A separable section has a seal bore to protect lower pressure rated casing in the upper annulus from overpressure during the refracturing operations. Either existing perforations can be refractured or new perforations made and fractured. With a multiple shot perforating gun all the zones can be perforated and fractured in a single trip with a service string that supports a releasable plug, a gun and frac ports. The BHA can be remove with a line cut above the anchor seal at the bottom and a pull on the tubular sting that takes all the swelling packers out. Location devices can be employed for proper gun placement before firing.