Mining and Geological Features of Well Drilling in Western Siberia

Novoportovskoe oil-gas-condensate field belongs to Western Siberian oil and gas province. During drilling on this field, the next sections are distinguished: a. Liable to drilling mud losses. This drilling trouble results in full or partial loss of drill mud circulation, which can lead to an emergency;
b. Liable to caving and failure. This drilling trouble can cause considerable narrowing of a borehole. Usually caving and failures occur in deviated intervals built with soft or unstable rocks;
c. Liable to gas, water and oil shows; This phenomenon breaks normal process of drilling, causes equipment wear and leads to emergencies;
d. Liable to sticking and jamming of BHA and drill string, differential sticking, packing, drilling mud thinning and etc.

Development of well construction has taken into account the next geological features of section: permafrost rocks occur in the interval of 0-260m (Table 1). The temperature varies from -7 to -1,5 °С, iciness is in the interval of 0,15-0,28. Reservoir pressures along the whole section of designed wells are equal to hydrostatic pressure (К_а=1,00). Gas horizons are lying in the interval of 505-2035m, anomaly ratio is К_а=1,00. Oil saturated horizons occur on the depth of 1013-2060m, anomaly ratio is К_а=1,00. Oil exploitation target U_2-6 lies in the interval of 2040-2060m with reservoir pressure being Р_RES2040=205kgf/cm² (К_а=1,00). On the base of geological section and drilling equipment, designed profile includes several intervals: one vertical interval, one zenith angle buildup section, two hold sections and one zenith angle drop section.