Express-Method of Assessing the Effectiveness of Acid Compositions for Oil Production Stimulation in Relation to Geological and Physical Conditions of Specific Formation

Abstract

As you know, most acid compositions intended for use in oil and gas production stimulation technology contain various surface-active agents (surfactants). During the filtration experiments the efficiency of surfactant-contained acid compositions is assessed by an increase of core permeability, which may be the result of two processes: dissolution of rock material and washing off the oil from porous medium surface. When both processes are at the same time, it is impossible to estimate the contribution of each of them. The express-method involves research on single cores. Only in case of the positive result of acid composition application regarding an increase of permeability and porosity of the core sample, you can proceed to the complete simulation on core samples with residual water or oil saturation. The filtration experiments are performed with a high pressure filtration unit and extracted core samples. The new approach is to replace a complicated research process of acid stimulation effect in order to select the most effective compositions, and the use of a simple study on a single water-saturated and oil-saturated core. This will reduce the work of testing acid compositions by eliminating the time-consuming research process on a stacked core model, as well as prevent from using the inefficient acid compositions in the field. In contrast to the experiments to determine the coefficient of oil displacement by water, as well as experiments to determine the curves of phase permeability, in which stacked core models are applied to avoid end effects, in this case a core material single-sample is used, since the main purpose of these experiments is to identify the impact of acid composition on the reservoir properties. Secondly, the feature of this method is the fact that allows you quickly and without additional expensive studies of the structure and composition of the core material, not only to select, but also to adapt the acid composition to the specific formation and porous medium conditions and characteristics. Thus, the further research is carried out only with the selected acid compositions excluding the rest of provided testing acids, saving a considerable amount of time and money.