The authors consider improving the quality of the mounting of wells in unstable terrigenous sediments, through the improvement of methods for monitoring the technical state of the wellbore, the development of sedimentation-resistant cement materials and buffer liquids. The objective was to determine the optimal drilling conditions, ensuring maximum short-term and long-term stability of the open well bore based on the analysis of previously drilled wells stock. Based on this, authors have proposed an appraisal system qualifying the well bore stability and designed a counting pattern. The main idea of the work was implemented in the development of the method for assessing the technical state of the wellbore, using color clusters taking into account the drilling events conducted during the construction of wells, and the time spent on the construction of the drilled section. Based on multivariate iterations we formulated conditions for increasing the stability of terrigenous deposits in the well casing process on the R. Trebs and A. Titov oil fields. In particular, as one of the solutions, new recipes of the sedimentation-resistant and high-strength light-weight oil-well cement and buffer liquids with polymers were proposed. The test results of the viscoelastic buffer fluid showed the lowest static filtration loss compared with standard buffer fluid containing anti-absorbing additives. Besides gel-cement solution with the addition of the reagent in the complex state with a density of 1500 kg/m3 showed high sedimentation stability according to the strength characteristics similar to the cement slurry density of 1600 kg/m3.
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