Sandstone Stimulation via In Situ Hydrofluoric Acid Generation
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Solution Overview
Problem
Current acidizing techniques for sandstone formations face challenges in efficiently generating hydrofluoric acid in situ to dissolve quartz and remove formation damage, while avoiding the handling of hazardous hydrofluoric acid and ensuring effective wellbore pressure and flowback.
Innovation Solution
A method involving the pumping of ammonium salts and nitrite salts through a wellbore into a sandstone formation, followed by an acid, to generate heat, nitrogen gas, and hydrofluoric acid, which dissolves quartz and enhances permeability, while using the generated nitrogen to increase wellbore pressure and facilitate flowback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrofluoric acid is pumped directly into the sandstone formation, then quartz dissolution and formation damage removal is effective, but handling and transporting hazardous hydrofluoric acid becomes complex and dangerous
Solution Approach 1:
The ammonium salt and nitrite salt are pumped into the formation in advance, positioned and ready before the acid injection. This preliminary placement allows the reactive components to be in situ when the acid arrives, enabling immediate HF generation at the treatment zone without the need to transport hazardous HF
Solution Approach 2:
The ammonium salt and nitrite salt act as intermediary substances that transform the injected acid into hydrofluoric acid in situ. These intermediaries react with the acid to produce the desired HF agent locally, avoiding the need to handle and transport hazardous HF from surface facilities
2Reliability
If ammonium salts and nitrite salts are pumped in sequence followed by acid, then hydrofluoric acid is generated in situ to dissolve quartz, but the treatment process becomes more complex compared to direct acid pumping
Solution Approach 1:
The ammonium salt and nitrite salt are pumped into the formation in advance, positioned and ready before the acid injection. This preliminary placement allows the reactive components to be in situ when the acid arrives, enabling immediate HF generation at the treatment zone
Solution Approach 2:
The multi-stage pumping process creates a continuous reaction sequence where ammonium salts and nitrite salts are first placed in the formation, then acid is injected to trigger continuous in situ generation of hydrofluoric acid. This continuous action ensures sustained quartz dissolution and formation damage removal throughout the treatment period
3Productivity
If conventional acidizing methods are used, then the process is simple, but formation damage removal and permeability enhancement are insufficient
Solution Approach 1:
The invention changes the chemical parameters of the acidizing process by introducing reactive ammonium salts and nitrite salts that transform the injected acid into hydrofluoric acid in situ. This parameter change enables effective quartz dissolution and formation damage removal, significantly enhancing permeability compared to conventional acidizing methods
Solution Approach 2:
The treatment system uses a composite approach combining ammonium salts, nitrite salts, and acid in a multi-stage pumping sequence. This composite material system creates the desired hydrofluoric acid treatment effect while avoiding direct handling of hazardous HF, achieving both effectiveness and safety
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 effectively generates hydrofluoric acid in situ to dissolve quartz, increases permeability, removes organic deposits, and promotes flowback by increasing wellbore pressure, thereby improving hydrocarbon production and reducing formation damage.
Implementation Method 1
generating heat, nitrogen gas, and hydrofluoric acid from reaction of the ammonium salts with the nitrite salt and the acid in the subterranean formation
Implementation Method 2
using the generated nitrogen to increase wellbore pressure and facilitate flowback
Implementation Method 3
acidizing the sandstone formation with the hydrofluoric acid, wherein the acidizing includes dissolving quartz in the sandstone formation with the hydrofluoric acid
Data Source
AI summary
Acidizing a sandstone formation in Earth crust, including pumping ammonium salts (an ammonium salt not having fluoride and an ammonium salt having fluoride) and nitrite salt through a wellbore into a sandstone formation, pumping an acid through the wellbore into the sandstone formation, generating heat, nitrogen gas, and hydrofluoric acid from reaction of the ammonium salts with the nitrite salt and the acid in the sandstone formation, and acidizing the sandstone formation with the hydrofluoric acid.