Horizontal spool tree wellhead system and method

A system for drilling and completing a subsea production well with a casing installed in the well bore and a wellhead housing having a wellhead housing bore installed on the upper end of the casing, the drilling operation including drilling a hole with a drill bit having a cutting diameter, the system comprising:

• a horizontal spool tree connected with an upper end of the wellhead housing, the spool tree having a spool with a spool bore and at least one spool side port extending radially from the spool bore;
• a BOP connected with the upper end of the spool tree and having BOP bore aligned with the spool bore and the wellhead housing bore;
• a casing string supported on a casing hanger within the bore of the wellhead housing;
• an orientationl sleeve between the wellhead housing and the spool, the orientationl sleeve having a predetermined rotational orientation with the spool and an internal diameter less than the cutting diameter of the drill bit;
• and
• a tubing hanger having a side port extending radially from a tubing hanger central bore for landing on the orientation sleeve and rotationally oriented by the orientation sleeve to align the tubing hanger side port with the spool side port.

A method of drilling and completing wells with a casing installed in the wellbore and a wellhead housing having a wellhead housing bore installed on the upper end of the casing, the method comprising:

• lowering a spool of a horizontal tree into connection with an upper end of the wellhead housing, the spool having a spool bore and at least one spool side port extending radially from the spool bore;
• installing a BOP at the upper end of the spool, the BOP having a BOP bore aligned with the spool bore and the wellhead housing bore;
• drilling a first hole with a first bit having a first cutting diameter by passing the first bit through the BOP and the spool on the wellhead;
• lowering a casing string carrying a casing hanger through the bores of the BOP, the spool and the wellhead housing into the first hole;
• landing the casing hanger on a shoulder within the wellhead housing;
• drilling a second hole with a second bit having a second cutting diameter less than the first cutting diameter by passing the second bit through the BOP and the spool on the wellhead, through the casing hanger and at least a portion of the casing string;
• thereafter installing an orientation sleeve between housing bore and the tree bore, the orientation sleeve having in a predetermined rotational orientation with the spool of the tree;
• and
• lowering a tubing hanger having a side port extending radially from a tubing hanger central bore for landing on the orientation sleeve and rotationally oriented by the orientation sleeve to align the tubing hanger side port with the spool side port.