A method transports and installs a heavy subsea structure such as a subsea processing center for produced crude oil or natural gas. The method includes controlledly flooding at least one ballast tank attached to or incorporated into the structure to the extent that the structure becomes negatively buoyant at a pre-determined towing depth. The method also includes towing the negatively-buoyant structure at the towing depth by the Controlled Depth Towing Method (CDTM). After towing to the installation location, the method includes further flooding the ballast tank to lower the structure onto the seabed. At the seabed, a fluid transportation pipe of a subsea production installation may be coupled to pipework of the structure.

A system includes a mud return system. The mud return system includes a pressure exchanger (PX) configured to be installed in a body of water, to receive used drilling mud, to receive a second fluid, to utilize the second fluid to pressurize the drilling mud for transport, via a mud return line, from a first location at or near the sea floor to a second location at or near a surface of the body of water.

A system includes a mud return system. The mud return system includes a pressure exchanger (PX) configured to be installed in a body of water, to receive used drilling mud, to receive a second fluid, to utilize the second fluid to pressurize the drilling mud for transport, via a mud return line, from a first location at or near the sea floor to a second location at or near a surface of the body of water.

A method and apparatus for capping a subsea wellhead is disclosed, including channeling a heterogeneous mixture (HM) into an inlet riser; measuring an initial HM temperature; heating the HM; measuring the temperature of the HM post heating; passing the HM through a common port; passing the HM into an oil baffle chamber; monitoring the interphase of the HM in the oil baffle chamber; passing the HM into a water baffle chamber; monitoring the interphase of the HM in the water baffle chamber; controlling oil and water regulators to achieve substantially laminar flow and separation of the oil and water; heating the gas separated from the HM; measuring the temperature of the separated gas; measuring the density of the gas separated from the HM and if in the gas phase, opening a gas regulator to allow the gas to pass through the gas outlets. Other embodiments are described and claimed.

There is described subsea apparatus and a method for processing fluid from a well. In an embodiment, a pipeline may be arranged to carry the multiphase fluid containing liquid and gas from the well. An outlet extending through a wall of the pipeline may let gas out of the pipeline from said region and through the outlet to separate said gas and liquid. A compressor may be connected to the outlet to compress the separated gas. Separated liquid may be conveyed along a sloping portion of the pipe to a low point in the seabed terrain, and may be conveyed to a pump for boosting the flow of liquid. The pump may be located in an excavated hole or glory hole below the seabed.

There is described subsea apparatus and a method for processing fluid from a well. In an embodiment, a pipeline may be arranged to carry the multiphase fluid containing liquid and gas from the well. An outlet extending through a wall of the pipeline may let gas out of the pipeline from said region and through the outlet to separate said gas and liquid. A compressor may be connected to the outlet to compress the separated gas. Separated liquid may be conveyed along a sloping portion of the pipe to a low point in the seabed terrain, and may be conveyed to a pump for boosting the flow of liquid. The pump may be located in an excavated hole or glory hole below the seabed.

A system for recirculating a portion of a liquid fraction of multiphase production fluid to a pump for enhanced functionality thereof. The system includes a splitter assembly that obtains the multiphase production fluid from the pump. The splitter assembly utilizes multiple internal chambers to separate gas and liquid fractions of the fluid. A portion of the liquid fraction may then be recirculated back to the pump as indicated whereas the remainder of the liquid fraction may be recombined with the gas fraction for production.

A system for recirculating a portion of a liquid fraction of multiphase production fluid to a pump for enhanced functionality thereof. The system includes a splitter assembly that obtains the multiphase production fluid from the pump. The splitter assembly utilizes multiple internal chambers to separate gas and liquid fractions of the fluid. A portion of the liquid fraction may then be recirculated back to the pump as indicated whereas the remainder of the liquid fraction may be recombined with the gas fraction for production.

A gas compression system and a method of flow conditioning by a gas compression system are provided. A gas compression system includes a compact flow conditioner in a form of a flow conditioner tank and a combined multi-phase pump and compressor unit comprising an impeller configured to compress a mixture of gas and liquid, wherein the gas compression system is configured such that the gas and the liquid are separated in the flow conditioner tank, the separated gas and liquid are sucked up through the separate gas and liquid pipes and re-mixed again upstream of the impeller, and the liquid is distributed in a gas flow by Venturi effect, and wherein the Venturi effect is obtained by a constriction in the outlet pipe to the impeller, just upstream of the impeller.

A gas compression system and a method of flow conditioning by a gas compression system are provided. A gas compression system includes a compact flow conditioner in a form of a flow conditioner tank and a combined multi-phase pump and compressor unit comprising an impeller configured to compress a mixture of gas and liquid, wherein the gas compression system is configured such that the gas and the liquid are separated in the flow conditioner tank, the separated gas and liquid are sucked up through the separate gas and liquid pipes and re-mixed again upstream of the impeller, and the liquid is distributed in a gas flow by Venturi effect, and wherein the Venturi effect is obtained by a constriction in the outlet pipe to the impeller, just upstream of the impeller.