Controlled Acid Delivery for Carbonate Reservoir Stimulation
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Solution Overview
Problem
Current acidizing treatments for carbonate reservoirs face challenges such as rapid acid consumption, limited penetration depth, and safety concerns due to the high reactivity and corrosiveness of strong mineral acids like hydrochloric acid, which require large volumes and pose risks during handling and application.
Innovation Solution
A composition and method for controlled acid delivery that includes a strong acid and a second acid or acid-generating compound, optimized to reduce available free water, slowing the acid's reaction rate with the formation, allowing deeper penetration with reduced acid consumption and minimizing corrosion, using a combination of strong acid, second acid or acid-generating compound, salts, and chelants to control the reaction rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strong mineral acids like hydrochloric acid are used to stimulate carbonate formations, then the acid reacts effectively with calcite and dolomite to create conductive flow paths, but the rapid reaction kinetics causes the acid to be spent quickly, requiring large volumes and limiting penetration depth
Solution Approach 1:
The patent applies preliminary action by pre-mixing the strong acid with a weak acid or acid-generating compound and a viscosity-enhancing agent before injection. This pre-formulated composition controls the acid's release and reaction rate in advance, allowing the acid to penetrate deeper into the formation before reacting, thereby reducing the total volume of acid needed while maintaining effective stimulation.
Solution Approach 2:
The patent changes the physical and chemical parameters of the acid system by adjusting viscosity (through gelling or emulsification) and controlling pH (through weak acid buffers). These parameter changes slow the reaction kinetics, extend acid lifetime in the formation, and enable deeper penetration with reduced acid volume requirements.
2Productivity
If strong mineral acids are used for carbonate stimulation, then effective dissolution of calcium and magnesium carbonates is achieved, but high reactivity and corrosiveness pose safety concerns and cause corrosion to drilling equipment, metal tubulars, and casing
Solution Approach 1:
The patent introduces a weak acid or acid-generating compound as an intermediary that buffers the strong acid's reactivity. This intermediary controls the release rate of active acid, reducing immediate corrosiveness to equipment while maintaining sufficient acidity to dissolve carbonate minerals effectively, thereby mitigating safety risks without compromising stimulation effectiveness.
Solution Approach 2:
Corrosion inhibitors and viscosity-enhancing agents are added preliminarily to the acid composition before injection. This pre-protection approach ensures equipment is protected from corrosion before the acid contacts it, and the enhanced viscosity keeps the acid contained in the target zone longer, reducing exposure time and corrosion risk to downhole equipment.
3Length of stationary object
If large volumes of acid are injected to overcome rapid consumption, then more acid is available to penetrate the reservoir, but the cost increases and handling and transfer safety concerns are exacerbated
Solution Approach 1:
The patent changes the reaction rate parameter by controlling pH through weak acid buffers and adjusting viscosity through gelling agents. These parameter changes extend the acid's effective lifetime in the formation, allowing it to travel farther before being consumed, thereby achieving greater penetration distance with reduced injected volume.
Solution Approach 2:
The patent creates local quality differences by formulating the acid with viscosity-enhancing agents that cause the acid to preferentially flow into lower permeability zones and fracture networks. This localized flow control ensures acid is delivered where needed most, maximizing penetration efficiency and reducing the total volume required to achieve effective stimulation.
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
The controlled acid delivery system enables deeper penetration of acid into the reservoir, reduces acid consumption, minimizes corrosion, and enhances safety by slowing the acid's reaction rate, thereby improving oil and gas production and reducing the risk of equipment damage.
Implementation Method 1
controlling the available free water in a provided composition facilitates control of the diffusion of acid within the composition
Implementation Method 2
restricts the ionic separation of the proton (H+), in other words, the dissociation of the acid
Data Source
AI summary
Provided herein are compositions and methods for the controlled delivery of acid to a subterranean formation.