Study on the Diverting Characteristics of Diverting Acid Based on Digital Rock Physics

Abstract

The application of diverting acid in oil and gas field development is becoming more and more widespread, with its characteristics of clean and pollution-free, self-diverting, and good acidizing effect. Currently, there is little research on the diverting characteristics of diversion acids in reservoirs. Using nondestructive and high-precision digital rock physics (DRP) technology, the diverting characteristics of diverting acid can be studied in three dimensions. At the same time, in the process of digital rock construction, deep learning (DL) technology is used to accurately identify and segment fractures, pores, and matrix in complex rocks, construct a three-dimensional pore-fracture network model and rock mineral model that fit the actual situation, and establish a fluid’s real flow channel. Finally, the acidification characteristics of diverting acid and conventional hydrochloric acid systems were studied using DRP technology, and it was found that for rocks with strong heterogeneity, the conventional hydrochloric acid system has a poor acidizing effect. On the one hand, it is difficult to connect low-permeability channels and effectively increase the oil drainage area. On the other hand, it will cause excessive dissolution of reservoir rocks, destroy the rock skeleton, and block the flow channels due to the destruction of some rock skeletons. Diverting acid flows in rocks, constantly undergoing acid–rock reactions, increases the viscosity of the acid solution, forcing the acid solution to flow from high-permeability channels to low-permeability channels, improving the connectivity of low-permeability channels, and effectively improving the acidification effect to achieve uniform acidification and increase rock permeability. The concentration of the diversion agent is the main factor affecting the diversion effect. Considering the acidification radius, construction cost, and pumping pressure conditions, appropriately increasing the concentration of the diversion agent can improve the effect of uniform acidification.