Multi-mode pumped riser arrangement and methods

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 bypass around the sealing element;
• operating in a closed mode where the sealing element and the bypass are essentially closed to prevent flow therethrough;
• operating with drilling fluid level reduced to below a 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 bypass to allow flow between the riser below the sealing element and the riser above the sealing element.

A method of measuring changes in liquid volume 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 bypass around the sealing element;
• operating in a closed mode where the sealing element and the bypass are essentially closed to prevent flow therethrough;
• switching to an open mode by opening the bypass to allow flow between the riser below the sealing element and the riser above the sealing element;
• essentially stopping circulation of liquid in the well;
• measuring a level of liquid in the riser over a period of time;
• and
• determining changes in volume of liquid in the well based on the level measurements.