Micro Calcium Carbonate Plugging for Thief Zone Conformance
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Solution Overview
Problem
Subsurface reservoirs with thief zones exhibit uneven fluid flow profiles, leading to rapid breakthroughs and inefficient use of injected fluids in enhanced oil recovery and geothermal systems, resulting in reduced production rates and project economics.
Innovation Solution
Utilizing extremely small calcium carbonate particles to plug and seal thief zones, forming deep-penetrating, low-permeability seals that divert injected fluid to targeted zones, improving conformance and sweep efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If subsurface injection is used to enhance oil recovery or geothermal production, then production rates can be increased, but thief zones cause rapid fluid breakthrough and poor injection conformance
Solution Approach 1:
The patent applies local quality by using particles of specific sizes (0.01-0.5 mm) that are optimally suited to plug thief zones while allowing targeted zones to remain open. The particle size distribution is carefully controlled to achieve different flow characteristics in different reservoir zones, improving both conformance and production.
Solution Approach 2:
The patent changes the physical parameters of the injected fluid by adding solid particles with specific size distributions (0.01-0.5 mm range). This parameter change transforms the fluid from a uniform flow to a non-uniform flow that can selectively plug high-permeability thief zones while maintaining flow in targeted zones, thereby improving injection conformance.
2Reliability
If solid particles are injected to plug thief zones, then injection conformance improves, but particle size selection becomes critical and complex
Solution Approach 1:
The patent segments the particle size into specific ranges (0.01-0.5 mm) that correspond to different thief zone characteristics. This segmentation allows the system to address different fracture sizes and permeability levels with appropriate particle sizes, simplifying the selection process while maintaining effectiveness.
Solution Approach 2:
The patent establishes specific parameter ranges for particle size (0.01-0.5 mm) that optimize plugging efficiency. By defining these parameters clearly, the complexity of particle selection is reduced to following established guidelines rather than requiring complex real-time calculations.
3Loss of energy
If larger particles are used to plug thief zones, then flow resistance increases, but particles may not penetrate deep enough into the reservoir
Solution Approach 1:
The patent segments the particle size into fine (0.01-0.5 mm) and coarse fractions, with fine particles penetrating deep into the reservoir to plug smaller fractures and pores, while coarse particles provide immediate flow resistance at the injection point. This segmentation resolves the contradiction by having different particle sizes perform different functions.
Solution Approach 2:
The patent introduces particle size distribution as an additional dimension to the plugging mechanism. Instead of using a single particle size, the system utilizes a spectrum of sizes (0.01-0.5 mm range) that simultaneously provide deep penetration and effective flow resistance, adding a dimensional complexity that resolves the contradiction.
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
Enhances oil and geothermal production rates by effectively shutting off fluid flow in thief zones, increasing the utilization of injected fluids and improving project economics.
Implementation Method 1
Solid particles in the injected fluid can form bridges and blockages in the fractures and over the pores of the high-permeability streaks, increasing flow resistance in the thief zone and diverting injected fluid to targeted zones.
Implementation Method 2
The injected fluid then flows through the reservoir rock and displaces the oil towards the production wells to enhance oil production.
Implementation Method 3
The injected water circulates through the fractures and heats up. The hot water is then pumped back from the production well to the surface, where it can be used to generate electricity.
Data Source
AI summary
A method of shutting off injected fluid flow into the thief zones and of improving subsurface injection conformance using micro calcium carbonate particles includes estimating the pore size and fracture width of the thief zone, designing of a treatment program for the required calcium carbonate particle size, spectrum and concentration for plugging the pores and fractures, and creating a tight and deep-penetrating seal of low permeability over the thief zone, determining the post-treatment permeability of the seal and injected fluid flow rate profile before and after the treatment.