Assessment of the fracture stress of clay-carbonate rocks of the Vereiskian reservoir for oil fields in the Perm region

Abstract

Currently, one of the most effective stimulating oil production methods from the Vereiskian production zones of oil fields in Perm Krai is proppant hydraulic fracturing (PHF). The effectiveness of the method largely depends on the geometric dimensions of the fracture and the optimal distribution of the proppant in it. The mudstones of the Vereiskian stage limit the growth of the fracture in height, but in certain cases its can be broken in the course of hydraulic fracturing. In this regard, the determination of the conditions for their fracturing is an urgent and important task. In the absence of rock samples of proper quality, the chemical composition of mudstones was determined during the study. The obtained results are compared with the existing data on the minerals of the montmorillonite group of clays. To determine the parameters of the ultimate stress state of the formation, a Mohr’s circle of stress is constructed using the known values of the compressive stress and the angle of internal friction of the clays. As a result, the fracture stress of mudstones is obtained, which is in the range of bottom-hole pressures during hydraulic fracturing, that is, there is a possibility of fracture growth outside the target interval.