Carbonate Stimulation Using Chelating Agents: Improving the Treatment Performance by Optimizing the Fluid Properties

Area of Science:

• Petroleum Engineering
• Chemical Engineering
• Materials Science

Background:

• Chelating agents are explored as alternatives to strong acids for oilfield acidizing, especially in high-temperature, high-salinity environments.
• Limited research exists on optimizing chelating agent performance under such demanding conditions.

Purpose of the Study:

• To comprehensively study the solubility and physical properties of common chelating agents (DTPA, HEDTA, EDTA) under various conditions.
• To determine optimal concentration ranges for maximum acidizing efficiency.
• To develop empirical models for predicting chelating agent properties and performance.

Main Methods:

• Experimental measurements of density, viscosity, solubility, interfacial tension, and core flooding at 2000 psi and 120°C.
• Utilized over 340 data sets to develop new empirical models.
• Tested chelating agents: diethylenetriaminepentaacetic acid (DTPA), hydroxyethylenediaminetriacetic acid (HEDTA), and ethylenediaminetetraacetic acid (EDTA).

Main Results:

• HEDTA and DTPA demonstrated good solubility across various pH and concentrations.
• EDTA exhibited limited solubility above 15 wt %.
• Developed correlations accurately predicted chelating agent density and viscosity with ~1% error.
• Optimized solutions effectively treated tight carbonate rocks, creating wormholes with minimal acid volume.
• Models showed high reliability in predicting pressure drops during core flooding.

Conclusions:

• This research provides optimal concentration and pH ranges for chelating agent application in stimulation treatments across a wide temperature spectrum.
• The developed correlations offer rapid and reliable estimations of chelating agent properties and pressure drop at reservoir conditions.
• Findings facilitate improved design of oilfield stimulation treatments using chelating agents.