Construction of thermally insulated well in bovanenkovo field

Abstract

In the Bovanenkovo field, which is located in the permafrost zone, production from gas wells encounters the following problems: The high ice content of rock in the upper part of the section and the low rock temperatures (below -5~ are responsible for periodic collapse of the rock in the space near the well bore, loss of stability of cementing, misalignment of fittings, increased probability of flow of gas between strings, and so on, as a result of the heating effect of the gas flow on this space; other adverse effects include the collapse of casing strings when the fluid remaining outside the casing after drilling and cementing operations refreezes nonuniformly during a period of well shutdown, in the interval before the start of production, or during a period of conservation. The most effective means for preventing these problems is the use, in the operation or conservation of wells, of thermally insulated casing or tubing with a thermal resistance high enough to ensure extended operation of the well while maintaining a subfreezing temperature outside the casing; another possibility is the use of higher-strength casing with a critical crushing pressure higher than the maximum pressure created by the freezing liquid in one interval or another of the frozen ground with a known natural subfreezing temperature. In selecting a well program for conditions of the Bovanenkovo field (Aptian horizons), the following features were taken into account. No thermal insulation or "passive" thermal protection in permafrost is capable of eliminating the gradual