Multilateral well and electrical transmission system

A multilateral well and electric transmission system, comprising:

• a primary wellbore in which a primary well tubular is arranged;
• and
• a branch wellbore in which a branch well tubular is arranged;
• wherein the branch well tubular is connected in an electrically conductive manner to the primary well tubular such that the primary and branch well tubulars form a link for transmission of electrical power and/or signals between the primary and branch wellbore;
• wherein the primary and branch well tubulars form a link for transmitting low voltage power from a first pole of an electrical power source which is electrically connected to the primary well tubular to electrically powered equipment within the branch wellbore which is electrically connected to the branch well tubular, and wherein a second pole of the electrical power source and the branch well tubulars are electrically connected to the earth;
• wherein the electrically powered equipment comprises a re-chargeable battery which is trickle-charged by the low voltage electrical power transmitted via the well tubulars;
• wherein the electrically powered equipment comprises measuring and/or control equipment which is powered by a rechargeable lithium-ion high-temperature battery and is mounted on an equipment carrier module which is removably secured within the branch well tubular such that one electrode of the battery is electrically connected to the branch well tubular and another electrode of the battery is electrically connected to the subsurface earth formation surrounding the branch wellbore;
• wherein the equipment carrier module formed by a sleeve which is removably connected within the branch well tubular by means of a number of expandable clamps;
• and
• wherein the sleeve spans an inflow area of the branch wellbore where the branch well tubular is perforated, the expandable clamps consist of a pair of expandable packers which seal off an annular space between the branch well tubular and sleeve near each end of the sleeve and wherein the sleeve is provided with one or more fluid inlet ports which can be opened and closed by one or more valves which are powered by the rechargeable battery.