Investigation of change in different properties of sandstone and dolomite samples during matrix acidizing using chelating agents
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Properties of rock, such as effective porosity, permeability and pore size distribution (PSD), are generally referred to as petrophysical properties. These properties are among the most significant for reservoir evaluation. Acid stimulation treatments are usually used in sandstones to mitigate the impact of formation damage, with the aim of restoring or enhancing the natural matrix permeability and consequently boosting the well productivity. Hydrochloric acid (HCl) is commonly used in the preflush stage to remove calcium and other metal ions, preventing the development of calcium fluoride (CaF 2 ) and other silicate precipitates that could block the pore throats, while an acid mixture (HF–HCl combination) is usually preferred as the main stimulation fluid for the removal of quartz and remaining metal ions. However, sometimes the application of these acids can lead to other problems, including fast reactions, corrosion of pipes, environmental hazards, precipitation reactions and formation damage due to the incompatibility of HCl with clay minerals, so chelating agents have been proposed as an alternative for matrix stimulation fluids. In this study, three different chelating agents, ethylenediaminetetraacetic acid (EDTA), N-(2-hydroxyethyl) ethylenediamine-N,N′,N′-triacetic acid (HEDTA) and N-acetyl-l-glutamic acid (GLDA), have been used to stimulate Berea sandstone, Colton tight sandstone and Guelph dolomite samples. Core flood experiments were conducted on 1.5 × 3 (in 2 ) core plugs, at a temperature below 180 °F. A slow injection rate of (1–0.5 cc/min) was chosen for the treatment fluid, promoting the dissolution of ions by increasing the contact time between the fluid and the rock. Furthermore, nuclear magnetic resonance, wettability and micro-computed tomography (CT scan) analyses were employed to evaluate the effect of the acid treatment on formation properties such as porosity, PSD, pore topology, wettability and pore structure. After exposing the samples to HEDTA, large wormholes were detected in their pore network, demonstrating that HEDTA has the highest potential to create new pore spaces when compared to GLDA and EDTA when reacted with both types of samples.
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Investigating the Effectiveness of Emulsified Acid on Sandstone Formation under High Temperature ConditionsBen Mahmud, Hisham ; Norlee, Adeline; Tan, Inn Shi; Foo Chee Yew, Henry; Shafiq, Mian Umer (2019)Acid stimulation supports the oil and gas industry as a versatile mean in enhanced oil recovery to fulfill the world energy demand. Although hydrochloric acid can significantly improve the reservoir permeability, its rapid ...
Mineralogy and pore topology analysis during matrix acidizing of tight sandstone and dolomite formations using chelating agentsShafiq, M.; Ben Mahmud, Hisham; Arif, M. (2018)© 2018 Hydrochloric acid (HCl) is commonly used during acidizing but certain problems are associated with its application such as corrosion of pipes, environment hazards, precipitation of fluosilicates or calcium fluorides ...
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