Review of Acid Diffusion Measurement Methods in Porous Media

Abstract

How best to measure molecular diffusion in a mixture is a topic that has been studied widely and is an essential element of various scientific disciplines. In the oil and gas industry, accurate acid diffusion measurement is vital to the design of acid treatments. In fact, predictions of acid penetration distance in hydraulic fractures and wormhole length during matrix acidization are not possible without accurate diffusion coefficient data or correlations. The present study explains and critically compares the various methods used to measure the acid diffusion coefficient, including the rotating disk apparatuses, core flooding, nuclear magnetic resonance, annular reactors, parallel plates, and diffusion cells. This study also summarizes the impacts of acid type, chemical additives, minerals, temperature, and pressure on diffusion measurement. Tabulated summaries of the diffusion coefficient values associated with various acid types are also provided. Popular correlations for predicting the acid diffusion coefficient are also thoroughly discussed. Finally, recommendations are provided regarding best practices for obtaining accurate acid diffusion measurement data.

Acid retardation for deeper stimulation—Revisiting the chemistry and evaluation methods

“…F I G U R E 5 Schematic illustration of an annular flow reactor [22] F I G U R E 4 Schematic representation of a diffusion cell for measuring acid diffusion coefficient [24] The parallel plate experimental setup has been used by many researchers because it simulates the fracture flow geometry and surface better than other methods, [35][36][37][38] but the reaction boundary layer is variable along the flow. When solving the numerical model of acidcarbonate reaction in parallel plates, an effective diffusion which lumped the counter ion effect was used.…”

Comparative Study of Fracture Conductivity in Various Carbonate Rocks Treated with GLDA Chelating Agent and HCl Acid

“…Several studies were conducted to optimize the efficiency of acid fracturing treatments, and experimental and simulation approaches were used. − Different types of acids were examined, including straight, gelled, and emulsified acids. − The most common acid is HCl, which can dissolve different types of carbonate rocks and induce rough fracture surfaces. However, several problems are associated with straight HCl acid injection, such as corrosion due to the high reaction rate and short penetration within the fracture. , The HCl acid can be retarded in acid fracturing treatments by adding viscoelastic surfactants (VES), emulsifiers, gelling agents, and cross-linkers.…”