Comparing with water-based fluids, oil-based fracturing fluid is not in wide use. The main reasons are lower cost effectiveness and more dangerous handling of oil-based fluid. However, as non damaging fracturing fluid, the oil-based fluid has numerous advantages over water-based. In fact, in many cases, where water-based fluid failed, switching to oil-based fluid resulted with successful stimulation of well productivity. One of such cases is fracturing of partially depleted oil reservoirs of Bakhilov and North Khokhryakov fields in Western Siberia, Russian Federation. The oil fields were discovered in 1983. Production started in 1987 and water injection began in 1988. The peak oil production was reached in 1991/92, followed by drop of 50%. An attempt was made to increase wells productivity by performing small hydraulic fracturing treatment using water- based fluid. Although it resulted in some increase in wells productivity, the analysis of that treatments suggested necessity for longer fractures and careful tailoring of fracturing fluid. Recently the twenty-three fracture treatments have been performed using an oil-based fracturing fluid and pumping significantly higher quantity of proppant. The result is excellent: nearly all wells started to flow at the average initial oil rate of 70 m3/day [440 bopd] what is more than ten-folds production increase in comparison with pre-fracture production. Comparison of median values of early and late post-fracture production indicates sustained productivity improvement. P. 121