US 6,142,236 A · Method for drilling and completing a subsea well using small diameter riser

Abstract

A subsea wellhead assembly located at the sea floor that includes a subsea wellhead and a stationary blowout preventer mounted to the subsea wellhead for controlling a well during drilling. A drill pipe defines an annulus within the stationary blowout preventer. The drill pipe extends to a rotational drive mechanism on a drilling rig at the surface. A drilling head forms a seal against a drill pipe with a rotatable inner portion. The rotatable inner portion rotates with the drill pipe and prevents drilling fluid returns from flowing up the annulus around the drill pipe and prevents drilling fluid returns from discharging onto the seabed. The drilling head is mounted on top of the stationary blowout preventer. A riser extends upward from the drilling head and extends to a floating drilling rig. The riser has a lower end that connects into the drilling head below the drill pipe seal for receiving mud-returns flowing up around the annulus of the drill pipe. The riser is offset from and parallel to the drill pipe. After drilling, the riser is used to complete the well.

Claims18

Dependent claims

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

(a) supporting a rotatable drilling head on a subsea wellhead assembly;
(b) connecting a riser from a drilling vessel to the drilling head;
(c) connecting a drill bit to a string of drill pipe and lowering the drill pipe from the drilling vessel alongside the riser, through the drilling head and into the well, defining a drill pipe annulus in the well which is sealed at the subsea wellhead assembly by the drilling head;
(d) rotating the drill bit and drilling head, pumping drilling fluid down the drill pipe and into the drill pipe annulus, and returning the drilling fluid from the drill pipe annulus to the riser, and through the riser to the drilling vessel;
then
(e) after the well has been drilled, employing the riser to run tubing and complete the well.

3 more elements

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

(a) connecting sections of a riser together and extending the riser from a drilling vessel to a subsea wellhead assembly, the riser having a main conduit and an auxiliary line, both of which are offset from a main bore of the subsea wellhead assembly;
(b) securing a drill bit to a string of drill pipe, lowering the drill pipe from the drilling vessel alongside the riser, through the main bore of the subsea wellhead assembly and into the well, defining a drill pipe annulus in the well;
(c) rotating the drill bit, pumping drilling fluid down the drill pipe and into the drill pipe annulus, returning the drilling fluid from the drill pipe annulus to the riser, and through the riser to the drilling vessel;
(d) runnning at least two strings of casing alongside the riser and into the well, cementing the casing and causing cement returns to flow up the riser;
then
(e) after the well has been drilled and cased, retrieving the riser, securing a tubing hanger running tool to the main conduit of the riser, and a tubing hanger and string of tubing to the tubing hanger running tool;
then
(f) with the riser, lowering the tubing into the well, creating a tubing annulus;
(g) pumping completion fluid down the main conduit of the riser and down the tubing into the tubing annulus, and returning the completion fluid from the tubing annulus up the auxiliary line;
and
(h) lowering a perforating gun through the main conduit of the riser into the tubing and perforating the well;
then
(i) closing the tubing and the tubing annulus at the subsea wellhead assembly and retrieving the riser.

10 more elements

Dependencies are inferred from the claim text.

Method for drilling and completing a subsea well using small diameter riser

Life of this patent

Method for drilling and completing a subsea well using small diameter riser

Life of this patent

Abstract

Claims18