Duration Of Acid Treatment Research Articles

Study on the Effect of Acid Corrosion on Proppant Properties

Pre-acid fracturing is an effective technique to improve productivity of tight reservoirs. While acid injection can clean the formation and improve the fracturing performance by reducing the fracture pressure of the reservoir, the chemical reaction of the acid solution with proppant may reduce the compressive strength of the proppant and therefore negatively affect the fracture conductivity. In this study, we experimentally investigated the solubility of the proppant in acid and the effect of acid corrosion on proppant compressive strength and fracture conductivity. The results show that the concentration of the acid solution has the greatest effect on solubility of the proppant, which is followed by the contact reaction time. Though a proppant of larger particle size indicates a lower solubility, the acid corrosion poses a greater damage to its compressive strength and conductivity. The quartz sand proppant exhibits superior stability to ceramic proppant when they are subjected to acid corrosion. The experimental results could serve as reference for selection of proppant and optimization of acid concentration and duration of acid treatment during pre-acid fracturing.

Effective Condition for Purification of Multi-Walled Carbon Nanotubes by Nitric Acid

The multi-walled carbon nanotubes were synthesized on Fe-Ni bimetallic catalysts supported by MgO using thermal chemical vapor deposition. A comparative study on the effect of nitric acid molarity and time duration of acid treatment on purification of multi-walled nanotubes was done. The studies revealed that for finding a suitable condition for purification of multi-walled carbon nanotubes, it is necessary to determine suitable molarity of acid and immersion time of the carbon nanotubes. It was found that 5 M of boiling nitric acid at 3 h leads to the highest removal of the impurities with the least destructive effect. Various analytical techniques such as: scanning electron microscopy (SEM), high resolution transition electron microscopy (HRTEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and Raman spectroscopy techniques were employed to investigate the morphology, graphitization and quality of the carbon nanotubes.

I. Acid treatment and mechanical scarification

Abstract Only about 30% of the Centrosema pubescens (centro) seed examined germinated under favourable conditions of moisture and temperature. Germination percentage increased to more than 80% after seed treatment with concentrated sulphuric acid or by mechanical scarification. Seeds could be treated with acid for up to 20 min without impairing germination capacity. Maximum normal seedlings with scarification were recorded when seeds were scarified at 22.5 psi or 25.0 psi for 5 min. As the pressure or duration of scarification or the duration of acid treatment was increased, the number of abnormal seedlings also increased. Furthermore, acid-treated or scarified seeds produced more abnormal seedlings than untreated seeds.