Well construction mates with many circumstances related to the quality of borehole sinking and cementing. Casing string cementing is one of the most important stages in well construction, summarizing drilling of certain well interval and prviding a further long-term correct operation of the whole well. In order to perform a correct cementing of well casing strings in the presence of permafrost formations (PFF), lost circulation zones of drilling fluid and reduced static temperatures it is required to apply an effective and reliable cementing formulaes, which allow to perform the well cementing in a qualitative manner, relatively cheap and without big labour costs and change of existing technologies.

The work represents the results of performance of laboratory investigations on selction of optimum recipe of grouting mixture of oil-well cement and high-test gypsum. As a result of development laboratory works the gypsum-cement recipe for casing strings cementing (324 mm conductors and 245 mm surface casings) in Eastern Siberia was developed. The differentia of this formulae from cements applied today, are optimum strength characteristics of cement stone and heightened setting time along with acceptable time of grouting mixture thickening.

The work represents the results of pilot testing on conductors cementing with application of the developed gypsum-cement formulae at twenty wells of three fields (Central area of Talakan field, Alinskoe and Eastern-Alinskoe field). As a result of practical application of grouting material with addition of gypsum cementing high-test separated one the following was achieved: improvement of casing string cementing quality and substantial effect on reduction of time of waiting on cement (WOC) two times less in comparison with the traditional cementing technology in PFF gross intervals.

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