Inner Wellbore Casing Isolation for Restimulation
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Solution Overview
Problem
Existing methods struggle to effectively isolate old fractures from new ones during restimulation operations in well fracturing, leading to significant fluid loss and reduced control over stimulation treatments.
Innovation Solution
The use of biodegradable diverting agents, such as polyester-based particulates and polymeric materials, combined with an inner casing and outer casing setup, creates a frictional pressure drop to divert treatment fluid away from old fractures and perforations, allowing for effective isolation and consistent stimulation of new zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolation methods are used to isolate old fractures during restimulation, then some level of isolation is achieved, but significant fluid loss occurs and control over stimulation treatments is reduced
Solution Approach 1:
The wellbore is segmented into distinct zones using an inner casing string positioned within the outer casing. This segmentation creates isolated intervals that allow independent stimulation of new perforation clusters while preventing fluid communication with old fractures. The inner casing acts as a physical barrier that divides the wellbore into treatment zones, enabling precise control over where fracturing fluid is directed.
Solution Approach 2:
An intermediary fluid system is introduced between the inner and outer casings to manage pressure and fluid flow. This intermediary system includes friction reducers and other additives that control fluid dynamics in the annulus, allowing the inner casing to effectively isolate old fractures while maintaining controlled flow to new perforations. The intermediary fluid acts as a mediator that enables the isolation mechanism to function properly.
2Loss of substance
If inner casing is used to isolate old fractures, then fluid loss is minimized, but device complexity increases
Solution Approach 1:
The inner casing string is nested within the existing outer casing structure, creating a concentric arrangement that provides isolation functionality without requiring complete replacement of the wellbore infrastructure. This nesting approach allows the inner casing to be deployed through the outer casing and positioned at specific depths, providing a space-efficient solution that minimizes the additional structural complexity while achieving the desired isolation effect.
3Loss of substance
If diverting agents are used alone for isolation, then some fluid diversion is achieved, but consistent stimulation of new zones is difficult
Solution Approach 1:
The system merges mechanical isolation (inner casing) with chemical diversion (diverting agents in the annulus) to create a hybrid isolation mechanism. The inner casing provides the primary physical barrier for consistent isolation, while the diverting agents in the annular space between casings enhance fluid direction toward new perforations. This combination of mechanical and chemical approaches ensures both consistent isolation and effective fluid diversion, overcoming the limitations of using either method alone.
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 provides better isolation between new and old perforation clusters, enabling more controlled and effective restimulation treatments by directing fluid flow towards new fractures, thereby enhancing production efficiency and minimizing fluid loss.
Implementation Method 1
The frictional pressure drop in the annulus between the inner casing and outer casing aids in this diversion
Data Source
AI summary
Methods and systems for restimulating a previously fractured subterranean formation penetrated by a wellbore are described. The methods include plugging existing perforations in an outer casing and existing fractures in the formation with a diverting agent, placing an inner casing in the wellbore while the existing perforations and existing fractures are plugged with the diverting agent, perforating the inner casing and the outer casing to form new perforations, and pumping a fluid through the new perforations to create new fractures in the formation.