Subsea lateral drilling

A method for drilling a borehole in a producing subsea wellbore wherein a flexible conduit is connected at one end to a surface vessel and at the other end via a pressurized subsea wellhead to the producing subsea wellbore such that a remotely operated electrical drilling device (RODD) can be deployed down the flexible conduit, wherein the flexible conduit is attached to a lubricator that is connected to the pressurized subsea wellhead, the method comprising the steps of:

• directing the RODD to a location for drilling in the producing subsea wellbore;
• wherein the directing step comprises regulating a pressure inside the flexible conduit to be greater than a pressure inside the lubricator while maintaining the pressure inside the lubricator substantially the same as a pressure at the pressurized subsea wellhead such that the RODD is lowered into the producing subsea wellbore without injection;
• and
• drilling a further wellbore section with the RODD;
• wherein the drilling step comprises drilling in underbalanced conditions with respect to a formation;
• and using fluids produced from the formation to transport drill cuttings away from the RODD.