GEOLOGICAL RISKS WHEN OPENING FRACTURED, CAVERNOUS AND HIGHLY POROUS ROCKS

Abstract

Geological conditions (presence of highly porous, fractured and cavernous rocks in the section) and technological parameters have a significant impact on the occurrence of various complications during well construction. The most frequent complications, which are recorded in almost all oil and gas provinces, include absorption of flushing fluid (circulating drilling fluid). In the process of uncovering the rocks composing the section, their equilibrium is disturbed. As you know, the stability of rocks depends on their strength characteristics, change over time under the influence of various factors: tectonic movements, secondary processes (leaching, dolomitization, calcification), opening of mine workings. Geoecological risks arise in the presence of fractured, cavernous and highly porous formations in the geological section, zones of tectonic fracturing, faults and traps (Eastern Siberia). These risks are expressed in absorption of flushing fluid used during construction of wells; rock falls, water and oil and gas occurrences, open fountains. Scientific novelty. In order to prevent these complications it is necessary to correctly select recipe of used flushing fluids, their treatment with different chemical reagents. Among technological factors causing geological risks one may mention high density of circulating and cementing solutions, speed of their pumping, rheological properties, lowering-raising operations, violation of technological mode and others. Conclusions . Absorption elimination is carried out by colmatation of complication intervals with solid particles (colmatants), special inert fillers, plugging mixtures, reduction of solution density, installation of cement bridges, which do not always give positive results.