Seismic and Seismochemical Stimulation Increases Well Injectivity and Productivity

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 190456, “Increasing Well Injectivity and Productivity by Seismic and Seismochemical Stimulation,” by K. Furman, S. Miftakhov, SPE, M. Nazyrov, R. Nefedov, and V. Zamakhaev, Terratec, and A. Andrianov, AIA Consulting, prepared for the 2018 SPE EOR Conference at Oil and Gas West Asia, Muscat, Oman, 26–28 March. The paper has not been peer reviewed. Many oil fields in Russia and the Commonwealth of Independent States are in late-development stages, with waterflooding having being used for decades. A relatively new technology in production optimization is wave stimulation, in which the wellbore and reservoir are treated by acoustic, seismic, or other types of waves generated by tools. Approximately 250 wells have been treated in this manner, with a high success rate and significant oil-production increase. This paper discusses the potential of seismic and seismochemical well simulation in particular within the scope of this recent technology. Introduction Wave-stimulation technologies have short treatment times and can be applied in different types of formations and wells. This paper focuses on seismic-impact well treatment. The well treatment is based on a wellhead pneumatic generator that uses special valves. Energy is generated at the surface with compressed inert gas and released into the well. A shock wave then propagates through the liquid-filled well column and transforms into a seismic wave in situ. Movement of the shock wave creates a damped self-oscillating process with a frequency of 0.2 Hz, the effect of which can stimulate injection and production wells. One method of increasing the efficiency of seismic stimulation is use in conjunction with the injection of chemical reagents. Mechanisms of Seismic and Seismochemical Stimulation No generally accepted theory describes the effects of seismic impact on reservoirs. On the basis of theoretical, experimental, and field research, various authors have proposed mechanisms and concepts, which are described in the complete paper. Porosity and Permeability Change in Dilatancy Area for Sandstones. Studies of dilatancy processes under dynamic effects have shown that, for sufficiently high unevenness of the stressed state, dilatancy processes occur even at stresses that are only 3–5% of the ultimate strength, causing irreversible change in the rock density, porosity, strength, and permeability. Dilatancy is observed in the deformation of soils and rocks. Extensive experimental data on the deformation of a wide class of formations under volumetric stressed-state conditions show that compaction is seen in highly porous rocks, while loosening is seen in dense rocks. Reduction in the volume of highly porous rocks occurs as the result of a reduction in the number of defects. Positive (compaction) and negative (loosening) rock-dilatancy values are related to the value of the initial effective porosity. If the effective porosity value is less than a certain limiting value, then the rock is dense and loosens during deformation. When the effective porosity is greater than its limiting value, the rock is compacted. However, the compaction of the rock can occur up to a certain value, after which it breaks down. The main influence on the amount of dilatancy is the result of an uneven load (i.e., the ratio of the minimum main stress to the maximum). However, at the same level and at the magnitude of the uneven loading in the stronger rocks, the dilatant component of the volume deformation exceeds the rock compaction more than is seen in less-rigid rocks.