Degasolisation («degasolisation» – recovery of gasoline, petrol); processing plant where specific gaseous and liquid hydrocarbons (methane, ethane, propane, butane, pentane, natural petrol) are separated from the mixture of natural gas.
Dehydration – elimination of water from substances; elimination of water from petroleum and natural gas, and damp from natural gas.
Dehydration of gas - plant for eliminating damp from natural gas.
Density – ratio of mass and volume; value which shows the mass (in kg) of a volume unit (in m3); often in derived units kg/l; for example, water density is 1 kg/l, petroleum density is 0.8000 – 0.9000 kg/l.
Development/exploitation well – well which is drilled on a discovered reservoir of oil/petroleum and natural gas, aiming at optimal depletion of oil/petroleum and natural gas from the discovered reservoir.
De-oiling – elimination of oil from paraffin wax.
Discovered reserves – total determined quantity of petroleum and natural gas in discovered reservoirs, regardless whether it can be technically and cost-effectively drilled.
Distillation – process in which crude oil is separated into specific fractions.
Distillation column – device (vessel) in which specific ingredients (gases, petrols, paraffin wax etc) are separated from a heated mixture of crude oil at different levels and temperatures.
Distribution network – gas pipeline system inside a village or group of villages to which end gas consumers are connected (households, small industry, schools, hospitals etc.).
Diesel fuel - (diesel), fuel for internal combustion engines; produced by further refining of lamp oil (kerosene) and light gas oils which are separated from petroleum and its products at temperatures of 190 – 360 C.
Drilling plant – plant for drilling deep wells.
Drilling derrick – high, steel, screen-like construction, part of the drilling plant which helps to drill the well.