APPLICATION OF AN ELASTIC CEMENT STONE FOR INCREASING STABILITY OF WELL MOUNT AT SHOCK AND DYNAMIC LOADS

Abstract

Background One of the promising directions of well completion is the implementation of multistage hydraulic fracturing (MHF) in a cemented horizontal section of the well. This technique, in comparison with ordinary hydraulic fracturing, allows to abandon the equipment for cuff cementing and casing packers to separate the fracturing intervals, and also provides the ability to perform fracturing in any interval of a horizontal section with the required number of stages. Aims and Objectives To considers possible ways of reducing stresses in the cement sheath during multistage hydraulic fracturing (MHF) in a cemented horizontal section of the well. Methods To assess stresses and deformations in cement stone, an algorithm based on the finite element method was used. The calculation was carried out on the example of a cemented liner 114 mm, located in a horizontal section with a diameter of 156 mm. Results The simulation results showed that there is more stress in the thickened part of the cement sheath. In this case, there is a decrease in stresses inside the cement stone at the place of contact of the cement stone with the сasing and the contact of the cement stone with the rock to values that require the development of measures for reducing of the transfer of dynamic load from the casing to the cement stone. At the same time, the absence of the influence of the steel grade and the wall thickness of the casing strings on the magnitude of the stresses developing in the cement stone was shown. In the absence of «continuous» contact with the casing during hydraulic fracturing, an increase in internal stresses occurs throughout the cement stone, which also increases with the eccentric position of the casing. An increase in the Young's modulus of the cement stone has a positive effect on the resistance of the material to displacement and does not affect the magnitude of the stresses. With an increase in the Poisson's ratio relative to the basic composition, the calculated stresses decrease in both contact zones of the cement stone. The analysis showed that the use of elastic cement slurries with increased elastic-deformation characteristics can prevent contact disruption after completion of dynamic effects.