Proppants are required in hydraulic fracturing operations in the oil and gas industry. They consist of solid particles with specific strengths and are used to keep the rock fractures open in order to increase well production. They can be naturally occurring sand grains or artificial ceramic materials. Studying the acid resistance of proppants is important. Acids are needed to remove the scale and clays that affect the fracture conductivity.

This study investigated the different factors affecting the interactions between mud acid and sand proppants. Several experiments were conducted using the aging cell with mud acid (3 wt% HF, 12 wt% HCl) up to 300°F. The effects of temperature, soaking time, and static and dynamic conditions were examined. The supernatant of solubility tests was analyzed to measure total silicon concentrations using ICP-ES. The proppant was sieved before and after the experiments. Following that, the residual solids were dried and analyzed using a scanning electron microscope (SEM).

The results showed that sand proppant is soluble in regular mud acid, nearly 10 wt% dissolved in some cases. The amount of proppant dissolved increased with temperature, soaking time, concentration, and dynamic conditions. The fines generated and the changes in grain size distribution are detrimental to the proppant conductivity.

This work will help to achieve a better acid treatment design when sand proppant is used.

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