Delayed Crystallization Plugging for Fracture Control in Reservoirs
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Solution Overview
Problem
Conventional water flooding methods fail to effectively plug thief zones or fractures at substantial distances from the wellbore, leading to poor sweep efficiency and high residual oil saturation in carbonate reservoirs with natural fractures.
Innovation Solution
A supersaturated sodium aluminate solution with a delayed crystallization additive is introduced into the subterranean formation, controlling the crystallization of gibbsite to plug thief zones or fractures at a designed distance from the wellbore, using additives like methanol or surfactants to manipulate the induction period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional water flooding is used to displace oil from permeable zones or fractures, then oil recovery from fractures is improved, but sweep efficiency deteriorates and high residual oil saturation remains in lower permeability zones
Solution Approach 1:
The patent applies preliminary action by injecting a treatment fluid containing crystallizable solutes (such as sodium aluminate, calcium aluminate, or aluminum sulfate) before the main water flood. These solutes remain dissolved during injection and only crystallize after the fluid reaches the thief zones or fractures, creating plugs that redirect subsequent water flood into previously unswept low-permeability zones. This preliminary placement of crystallizable material allows the system to later convert the injected fluid into blocking structures at the desired location.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the phase transition of solutes from dissolved state to crystalline solid state. The treatment fluid is injected in a dissolved state that allows it to flow freely through the formation, and then conditions are changed (temperature, pressure, concentration) to induce crystallization at the target thief zones or fractures. This parameter change enables the same fluid to serve dual purposes: as a flowing carrier during injection and as a solid plugging material at the destination.
2Loss of energy
If plugging material is injected to plug thief zones or fractures at substantial distances from the wellbore, then sweep efficiency is improved, but precise control of plugging location and timing becomes difficult
Solution Approach 1:
The patent employs an intermediary substance (crystallizable solute such as sodium aluminate, calcium aluminate, or aluminum sulfate) that is injected in dissolved form and later transforms into a solid plug. This intermediary approach allows the plugging material to be transported as a fluid to distant thief zones without premature solidification, and then converts to a solid blocking structure at the target location. The intermediary nature of the crystallizable solute provides both flowability during transport and blocking capability at destination.
Solution Approach 2:
The treatment fluid is injected in advance with crystallizable solutes that will later crystallize to form plugs. This preliminary injection allows the plugging material to be positioned at distant thief zones before the main water flood begins, enabling precise control over where and when plugging occurs. The timing and location of plugging are controlled by the injection parameters and crystallization conditions rather than by mechanical placement.
3Productivity
If water flooding is used to improve oil recovery, then production is improved, but water intrusion into the formation increases
Solution Approach 1:
The patent applies preliminary action by injecting a treatment fluid containing crystallizable solutes (such as sodium aluminate, calcium aluminate, or aluminum sulfate) before the main water flood. These solutes remain dissolved during injection and only crystallize after the fluid reaches the thief zones or fractures, creating plugs that redirect subsequent water flood into previously unswept low-permeability zones. This preliminary placement of crystallizable material allows the system to later convert the injected fluid into blocking structures at the desired location.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the phase transition of solutes from dissolved state to crystalline solid state. The treatment fluid is injected in a dissolved state that allows it to flow freely through the formation, and then conditions are changed (temperature, pressure, concentration) to induce crystallization at the target thief zones or fractures. This parameter change enables the same fluid to serve dual purposes: as a flowing carrier during injection and as a solid plugging material at the destination.
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 allows precise plugging of fractures and pores at extended distances, improving oil recovery by reducing water cut and enhancing sweep efficiency, while being reversible and environmentally safe.
Implementation Method 1
A supersaturated sodium aluminate solution with a delayed crystallization additive is introduced into the subterranean formation, controlling the crystallization of gibbsite to plug thief zones or fractures
Implementation Method 2
A supersaturated sodium aluminate solution with a delayed crystallization additive is introduced into the subterranean formation
Implementation Method 3
using additives like methanol or surfactants to manipulate the induction period
Data Source
AI summary
The present invention relates to methods and compositions that can be used to delay crystallization of a treatment solution so that thief zones or fractures are plugged in subterranean formations at a substantial distance from a wellbore. A supersaturated sodium aluminate solution, or other solutions, is introduced into the reservoir. The solution is relatively stable in the supersaturated state. Crystallization, or de-stabilizing the solution, can be controlled, which in turn plugs the thief zone or fracture at a designed point of time. By controlling the time that crystallization starts, that is, the induction period, thief zones that are located at a substantial distant from the wellbore can be plugged.