Multi-mode pumped riser arrangement and methods

A method of operating a drilling system in open mode and closed mode, respectively, the method comprising:

• providing a riser having a return outlet to be coupled to a return pump, the return pump being adapted to pump fluid from the riser to above a surface of the body of water;
• positioning a sealing element in the riser above the return outlet;
• providing a by-pass with a selectively controllable isolation valve around the sealing element;
• and
• switching between open and closed mode by opening, respectively closing, the bypass.

A method of performing operations in a well extending from a bottom of a body of water, the method comprising:

• providing a riser having a return outlet to be coupled to a return pump, the return pump being adapted to pump fluid from the riser to above a surface of the body of water;
• positioning a sealing element in the riser above the return outlet;
• providing a by-pass functionality through the sealing element, wherein the sealing element is configured to open, allowing flow therethrough;
• operating in a closed mode where the sealing element and the by-pass are essentially closed to prevent flow therethrough;
• operating with drilling fluid level reduced to below slip joint in the riser above the sealing element;
• operating the return pump to reduce pressure below the sealing element;
• and
• switching to an open mode by selectively opening the sealing element to allow flow between the riser below the sealing element and the riser above the sealing element.

A method of handling gas accumulated below a sealing element in in a riser, the riser extending from a bottom of a body of water to above the surface of the water, the method comprising:

• providing a return outlet in the riser below the sealing element, the return outlet being coupled to a return pump, the return pump being adapted to pump fluid from the riser to above a surface of the body of water;
• providing a by-pass functionality of the sealing element;
• closing the by-pass;
• filling the riser with drilling fluid above the sealing element;
• and
• using the by-pass functionality, allowing the drilling mud to flow out the return outlet and through the pump at a rate high enough to flush gas in the riser through the pump and up to above the surface.

A method of performing operations in a well extending from a bottom of a body of water, the method comprising:

• providing a riser having a return outlet to be coupled to a return pump, the return pump being adapted to pump fluid from the riser to above a surface of the body of water;
• positioning a sealing element in the riser above the return outlet;
• operating in a closed mode, where the sealing element and a by-pass of the sealing element are essentially closed to prevent flow therethrough;
• arranging a boost line coupled to the riser at an inlet below the sealing element, the boost line extending to above the surface of the body of water;
• stopping flow through a drill string extending through the riser when the system is in closed mode;
• and
• using the boost line as a pressure equalization line to take up U-tubing volume though a drill string extending through the riser.