A method of estimating a state of a rotary steerable drilling system comprising applying a control input to a rotary steerable drilling system, sensing an actual output of the rotary steerable drilling system, inputting the control input into a mathematical model of the rotary steerable drilling system, receiving an estimated output of the rotary steerable drilling system from the mathematical model, generating an error compensation signal based on a difference between the actual output and the estimated output, and applying the error compensation signal to the mathematical model.

A wellbore intervention tool conveyance system includes an upper pipe injector disposed in a pressure tight housing. The upper injector has a seal element engageable with a wellbore intervention tool and disposed below the injector. The upper housing has a coupling at a lower longitudinal end. A lower pipe injector is disposed in a pressure tight housing, the lower housing has well closure elements disposed above the lower pipe injector. The lower housing is configured to be coupled at a lower longitudinal end to a subsea wellhead. The lower housing is configured to be coupled at an upper longitudinal end to at least one of (i) a spacer spool disposed between the upper pipe injector housing and the lower pipe injector housing, and (ii) the lower longitudinal end of the upper pipe injector housing.

A conductor arrangement is for a collection of subterranean wells for recovering fluids from an underground structure. A frame is provided with several conductor guides, each forming an inlet opening for a conductor in an upper portion of the frame and an outlet opening for the conductor in a lower portion of the frame. The conductor is arranged to border a portion of a borehole towards a surrounding unconsolidated mass and has been passed through the conductor guide and down into the unconsolidated mass. The conductor guides are arranged in a mutually diverging manner in the direction from the inlet opening, and each conductor is extendable by a bend, the deflection angle of the bends providing mutually parallel center axes in coupling interfaces arranged in upper end portions of the bends.