Directional well to the Tournaisian deposits with the designed depth of 5941 m.
The following two zones with the incompatible drilling conditions are to be drilled in: Visean deposits that are developed and where formation pressures declined significantly; and promising Tournaisian deposits where formations with AHFP are to be drilled in.
The biopolymer system "Biocar-MT" that allows to avoid drilling mud losses and provide high quality of drilling into the formations with low pressures is planned to be used in the interval of the Visean deposits occurrence (4010-5381 m). Formation temperatures within the range of 135-138oC allow the use of the similar drilling mud systems. The interval is plugged off by the casing string with the diameter of Ø177,8 mm.
Further drilling in the interval of 5381-5941 m will be conducted using the polymer-clay drilling mud with the density of 1540-1560 kg/m3. Formation temperature in the drilling interval will reach 150oC that excludes the use of the clayless polysaccharide drilling muds, especially in their weighted form.
Therewith, we strive to maintain formation properties of the Tournaisian deposits. The polymer-clay drilling mud system that is planned to be used in drilling is an analogue of the drilling mud that we used last year for elimination of gas showings and further drilling of the well near Poltava. As it is known, that well had a record-breaking amount of production from the carbonate fractured reservoir.
Preparation of the "Biocar-MT" drilling mud is carried out directly at the well after the intermediate casing string with the diameter of Ø244,5 mm was run in.
PARAMETERS OF DRILLING MUD "BIOCAR-MT" :
- Density – 1,18-1,22 kg/m3;
- Funnel Viscosity – 40-100 s;
- Gel – 15-50/40-140 dPa;
- PV – 15-30 mPa*s;
- YP – 120-240 dPa;
- Flitration Loss – 3-5 сm3/30 min;
- Salinity – up to 27%;
- KCl - 5-7%;
- рН – 8,5-10,5.
