Analysis and selection of slurry composition, resistant to dynamic loads, in order to improve the quality of fastening the near wellbore zone in unstable formations

Abstract

The practice of cementing the bottomhole zone of wells in unstable formations shows that cement stone, designed to ensure rock stability, is the weakest link and can easily be destroyed under the influence of various loads. Such loads include perforation of the production string, hydraulic fracturing and other technological operations. The main factor contributing to the destruction of cement stone under dynamic loading is its low deformation properties. Repeated or cyclic loads cause fatigue phenomena in cement stone and lead to the formation and development of fractures in it. However, currently used cementing materials based on Portland cement have poor resistance to impact loads and low tensile strength. Therefore, the need to create an effective barrier with sand when cementing the bottomhole zone by developing reliable cementing compositions resistant to dynamic loads is relevant task. Therefore, task of current interest is the need to create an effective sand barrier when cementing the bottomhole zone by developing reliable cement compositions that are resistant to dynamic loads. One of the promising ways to protect the integrity of cement stone during perforation and hydraulic fracturing is to control the physical and mechanical properties of the cement material by adding various types of chemical reagents into cement compositions. The object of the study is cement stone created in the bottomhole zone of sand-producing wells. Here, a scientifically applied problem, the purpose of which was to increase the plastic properties of the cement slurry and increase resistance to deformations, as well as crack resistance was solved. In this regard, it is necessary to study the influence of various additives on the processes of formation of the structure, as well as other rheological and physical-mechanical properties of the cement slurry and stone. The studies carried out are based on the use of local raw materials and residual materials, as well as the correct determination of perforation time accordingly. In order to solve the problem, experiments in laboratory conditions were carried out. A special plugging cement of G-I-100 grade was used in the experiments. To achieve indicators aimed at improving the plastic properties of the prepared cement stone, plasticizers were used. The use of the Bentomix 1275 plasticizer in wells preserves the natural structure and filtration properties of the formation, which helps to increase oil production volumes. The Bentomix 1275 plasticizer accelerates the timing of putting wells into operation, and there is an increase in total and current production due to improved formation opening. The effect is due to the increase in the length of perforation channels in the formation due to the absence of fragments of cement stone, as well as an increase in the efficiency of fastening due to an increase in the structure in oriented zones