Laboratory studies of acid impact efficiency on rocks of low-permeable terrigenous collectors
The paper presents the results of studies on the acid compositions adaptation for treating the bottom-hole zone of reservoir rocks of Yu2-6 low-permeable terrigenous strata of the deposits, located in the south of the Tyumen region. It was revealed that the rocks of the objects under consideration are highly soluble both in the hydrochloric acid and in clay acid (a mixture of hydrochloric and hydrofluoric acids), herewith, in all the cases, the rocks solubility in acidic compositions significantly exceeds their carbonate content. Among the tested compositions, the clay-acidic composition has the maximum dissolving ability with a content of hydrofluoric acid of 3 % wt., which after neutralization forms the largest amount of a secondary sediment. To reduce the mass of such a precipitation while maintaining the effectiveness of the acid effect, a two-stage version of treating a core material by sequentially hydrochloric acid and then clay-acidic compositions is considered. This series of experiments demonstrated the best result when a clay acid composition with a hydrofluoric acid content of 1,5 % was used at their second stage. The procedure effectiveness was confirmed during filtration experiments on reservoir models. It is established that the two-stage acid treatment in combination with a depression effect resulted in 1,5...2,0 times possible increase of the recovery coefficient of the reservoir model permeability in oil as compared with the same indicator achieved after the killing fluid exposure.