Tubing hanger and wellhead housing with mating tubing annulus passages

A wellhead assembly, comprising:

• an outer wellhead housing secured to a first string of casing;
• an inner wellhead housing having a lower portion landed in the outer wellhead housing and secured to a second string of casing, the inner wellhead housing having a tubular sidewall defining a bore;
• a casing hanger landed in the bore of the inner wellhead housing and secured to a third string of casing;
• a tubing hanger landed in the bore of the inner wellhead housing, the tubing hanger having a lower end extending into the casing hanger and secured to a string of tubing, the tubing hanger having a production passage extending from the lower end to an upper end of the tubing hanger for flowing well fluid from the string of tubing;
• a tubing hanger seal surrounding the tubing hanger and sealing an exterior surface of the tubing hanger to the bore above the casing hanger;
• a tubing hanger tubing annulus passage within the body of the tubing hanger extending alongside, and having an axis offset and parallel to;
• the production passage in the tubing hanger from a lower port on the lower end of the tubing hanger to an upper port on the exterior surface of the tubing hanger above the casing hanger and below the tubing hanger seal;
• an inner wellhead housing tubing annulus passage extending vertically within the sidewall of the inner wellhead housing, having a lower end at the bore below the tubing hanger seal for communication with the upper port of the tubing hanger tubing annulus passage and an upper end at the bore above the tubing hanger seal;
• a valve mounted to the inner wellhead housing and accessible from an exterior of the inner wellhead housing for opening and closing the inner wellhead housing tubing annulus passage;
• and
• wherein the tubing hanger tubing annulus passage and the wellhead member tubing annulus passage are sized to enable circulation of fluid along a path down the string of tubing and up the wellhead member tubing annulus passage.

A method of drilling and completing a subsea well, comprising:

• (a) providing a tubing hanger having a production passage, a tubing hanger seal, a tubing hanger tubing annulus passage within the body of the tubing hanger extending from a lower portion of the tubing hanger upward to an upper port on the exterior of the tubing hanger below the tubing hanger seal;
• (b) providing a wellhead housing having a bore and a wellhead housing tubing annulus passage with a lower end and an upper end, both terminating at the bore;
• (c) with a drilling vessel, installing a wellhead housing at the sea floor, connecting a drilling riser to the wellhead housing and drilling through the riser and the wellhead housing to a selected depth;
• (d) running a string of casing through the riser and landing a casing hanger in the wellhead housing;
• (e) securing the tubing hanger to a string of production tubing, lowering the tubing hanger and production tubing through the drilling riser, landing the tubing hanger in the bore of the wellhead housing, and sealing the exterior of the tubing hanger to the bore with the tubing hanger seal located between the lower and upper ends of the wellhead housing tubing annulus passage;
• and
• (f) circulating fluid from the drilling vessel along a flow path defined by a tubing annulus surrounding the production tubing, the tubing hanger tubing annulus passage, and the wellhead housing tubing annulus passage.