Offshore Drilling
Natural gas and oil (hydrocarbon fluids) are formed underground as a result of multimillion-year tectonic processes. Hydrocarbons are accumulated in some areas of the earth called fields. To produce hydrocarbons accumulated in the ground, a well must be drilled.
Fields can be either offshore or onshore. In the 1980s Soviet geologists found several large offshore accumulations of hydrocarbons in the north east of Sakhalin—two of them now known as the Piltun-Astokhskoye oil and gas field and the Lunskoye gas field. To develop them, Sakhalin Energy was established in 1994.
Wells in offshore fields are drilled by offshore drilling rigs installed on production platforms or drill ships. For offshore fields, a number of platform configurations are available, including jack-ups, semi-submersible and gravity platforms.
Molikpaq means “big wave” in the language of the indigenous Inuit people of Alaska. Prior to installation on the Sakhalin shelf in 1998, the platform was used as a drilling rig in the Beaufort Sea north of Canada.
By now, three gravity base offshore platforms are installed: Piltun-
An offshore drilling rig is a wind-protected metal structure which supports drilling equipment and a long length of pipe, at the end of which is a drill bit. Drill slots are openings in the concrete jacket of the platform between which the rig can move.
The drilling rig lowers the length of the pipe into the platform slot and rotates it. The pipe, in turn, rotates the bit and causes it to dig through the rock, creating a wellbore. A well must not be vertical: the drill string can be deflected from the vertical to penetrate much more of the reservoir.
One well is not sufficient—to make production more efficient a group of production and water injection wells must be drilled. Higher than atmospheric pressure in the formation drives oil and gas into the well and out of the ground. As the pressure in the formation diminishes, water injection wells are used to introduce water into the formation to maintain the required pressure.
In accordance with the requirements of Russian laws, Sakhalin Energy committed to environmentally safe development of the Piltun-Astokhskoye and Lunskoye fields. To this end, drill cuttings and process fluids
Drill cuttings (separated from hydrocarbons) are injected into the rock, thus preventing the pollution the Okhotsk Sea during drilling and production operations.
Wells may be deviated from the vertical to penetrate targets up to 12 kilometres away from the drilling point.
In the long term, horizontal wells with super-large deviation exceeding 12 kilometres will be drilled to develop more of the fields from the existing platforms and
Currently, the maximum deflection of water-injection wells drilled from the Molikpaq platform is 6.3 km;
Sakhalin Energy will also use Smart Wells technologies for the completion of water-injection wells at the
