New methods for preventing crumbling and collapse of the borehole walls

Abstract

Purpose. To increase the stability of the wellbore during its construction in unstable rocks. Methodology. To solve the set tasks, an integrated approach is used in the work, which includes critical analysis and generalization of scientific and technical achievements in combination with theoretical and experimental research. Findings. Factors influencing the stability of the borehole walls in conditions prone to rock slides and rock falls are analyzed. Expediency of using baths for strengthening the walls of wells in deposits of clay rocks, including clay shales, has been established and substantiated. A formulation of a fuel-bituminous bath has been proposed, the installation of which in a well for 78 hours makes it possible to increase the initial compressive strength of rocks, which will ensure the integrity of the borehole walls. It is recommended to use corrugated casing pipes to cover the sections of the wellbore where there is intensive crumbling and collapse of rocks. Originality. For the first time, the main factors of wall destruction have been established and a method has been developed to prevent the destruction of walls of directional wells composed of rocks prone to loss of stability under the action of drill string loads. Practical value. To combat the collapse of the walls of the well composed of rocks, prone to loss of stability, the authors suggested setting up fuel-bituminous baths in the range of complications. In case when the collapse of the walls of the well can not be prevented with a fuel-bitumen bath, it is proposed to overlap the area of collapse with the casing using advanced corrugated casing pipes with the injection of adhesive into the rock mass in the near-wellbore zone. The use of an adhesive material increases the contact area of the metal shell with the rock, which collapses increasing the stability of the borehole walls.