Scientists from Perm Technical University, in collaboration with colleagues from the Institute of Oil and Gas Problems of the Russian Academy of Sciences, are proposing an improved method for treating carbonate reservoirs using acids, which allows for the assessment of changes that occur in rocks throughout their exposure to the chemical.
Traditional methods typically halt testing once the first wormhole forms, but the proposed method, in contrast, mimics the entire acid leaching cycle, just as it occurs in a real well. Researchers conducted a series of experiments in the laboratory on ten cylindrical samples, which were prepared to simulate reservoir pressure and temperature, as well as water and residual oil saturation.
"We obtained dual data before and after acid treatment for each sample, which allowed us, for the first time, to establish a clear relationship between the growth of permeability and porosity and the volume of chemical injected," said Sergei Popov, director of the
laboratory at the Institute of Oil and Gas Geology.
The results showed that after acid treatment, the average permeability of the rocks increased by a factor of 6880, porosity increased by 17.4%, while density decreased by 2.5%. This effect is attributed to the formation of a branching network of dissolved channels within the carbonate rock matrix.
According to Sergey Chernyshov, head of the university's oil and gas technology department, the key advantage of this method lies in its ability to predict results based on the acid dosage used. He added,
"For the first time, we were able to demonstrate how permeability and porosity change with increasing concentrations of the chemical, providing engineers not only with evidence of improved rock properties but also with a precise tool for calculating processing parameters."
The researchers noted that incorporating these relationships into computer programs will allow for the calculation of the optimal volume and acid injection rate for each well, reducing the risk of rock collapse and the overuse of chemicals. The team also plans to develop this method to include other types of reservoirs, which would broaden its application in the oil and gas industry.
