A subsea multiphase fluid separation system has a gas separator for separating gas from a well stream containing oil. A water separation stage downstream of the gas separator has at least one dual pipe separator for separating water from the oil of the wellstream. A water treatment system for cleaning oil from water is produced by the water separation stage. On an oil outlet path, downstream of the or each dual pipe separator, there is an electrocoalescer and at least one second separator in series.

A subsea multiphase fluid separation system has a gas separator for separating gas from a well stream containing oil. A water separation stage downstream of the gas separator has at least one dual pipe separator for separating water from the oil of the wellstream. A water treatment system for cleaning oil from water is produced by the water separation stage. On an oil outlet path, downstream of the or each dual pipe separator, there is an electrocoalescer and at least one second separator in series.

An apparatus for treating a multiphase hydrocarbon-containing fluid in an oil and/or gas production facility, the apparatus comprising: (a) an inlet for a multiphase hydrocarbon-containing fluid, wherein the inlet comprises a first pipe network configured to be connectable to a plurality of oil well heads in an oil field; (b) a separation system comprising: (i) a solids separator in fluid communication with the inlet; (ii) a solids outlet connected to the solids separator; (iii) a fluid separator in fluid communication with the solids separator, the fluid separator being configured to separate the remaining multiphase hydrocarbon-containing fluid into an oil phase, a water phase and a gas phase; (iv) an oil outlet connected to the fluid separator; (v) a gas outlet connected to the fluid separator; and (vi) a water outlet connected to the fluid separator; (c) a solids cleaning system connected to the solids outlet, wherein the solids cleaning system is configured to clean deposits of residual oil from the solid particles separated by the solids separator to provide cleaned solid particles and first residual oil, the solids cleaning system having a first output for outputting the cleaned solid particles and a second output configured to output the first residual oil; and (d) a water cleaning and recycling system connected to the water outlet, wherein the water cleaning and recycling system is configured to clean residual oil from the water phase separated by the fluid separator, the water cleaning and recycling system comprising an oil filter for separating the residual oil from the water phase to provide cleaned water and second residual oil, the oil filter having a third output for recycling the cleaned water to at least one well head of the oil field, wherein the third output comprises a second pipe network configured to be connectable to the at least one well head of the oil field, and a fourth output configured to output the second residual oil. Also disclosed is a corresponding method.

A subsea fluid processing system which receives a wellstream flow. The subsea fluid processing system includes a pressure control device which regulates a pressure of the wellstream flow, a gas-liquid separator unit which receives the wellstream flow downstream of the pressure control device and which provides a liquid stream and a gas stream, a first membrane separator which receives the gas stream and which provides a retentate stream and a permeate stream, a compressor which receives the permeate stream and which provides a compressed permeate stream, and a discharge cooler which receives the compressed permeate stream and which provides a cooled compressed permeate stream for injection into a subsurface reservoir. A density of the cooled compressed permeate stream is higher than a density of the compressed permeate stream.

A subsea fluid processing system which receives a wellstream flow. The subsea fluid processing system includes a pressure control device which regulates a pressure of the wellstream flow, a gas-liquid separator unit which receives the wellstream flow downstream of the pressure control device and which provides a liquid stream and a gas stream, a first membrane separator which receives the gas stream and which provides a retentate stream and a permeate stream, a compressor which receives the permeate stream and which provides a compressed permeate stream, and a discharge cooler which receives the compressed permeate stream and which provides a cooled compressed permeate stream for injection into a subsurface reservoir. A density of the cooled compressed permeate stream is higher than a density of the compressed permeate stream.

A natural gas conditioning system for conditioning unconditioned natural gas for use in a gas lift system at a wellbore comprises a series of coolers to receive and cool unconditioned natural gas, and a high-pressure, three-phase separator. The separator receives cooled unconditioned natural gas from the coolers and results in separate flows of conditioned lift gas, waste water and hydro-carbon liquids. The conditioned lift gas can be directed to a first heat exchanger, and the hydro-carbon liquids can be directed to a second heat exchanger. A chiller can be coupled to a third heat exchanger. All the components can be carried by a skid.

A natural gas conditioning system for conditioning unconditioned natural gas for use in a gas lift system at a wellbore comprises a series of coolers to receive and cool unconditioned natural gas, and a high-pressure, three-phase separator. The separator receives cooled unconditioned natural gas from the coolers and results in separate flows of conditioned lift gas, waste water and hydro-carbon liquids. The conditioned lift gas can be directed to a first heat exchanger, and the hydro-carbon liquids can be directed to a second heat exchanger. A chiller can be coupled to a third heat exchanger. All the components can be carried by a skid.

Methods of Enhanced Oil Recovery (EOR) from an oil reservoir by CO.sub.2 flooding are disclosed. One method comprises producing a well stream from the reservoir; separating the well stream into a liquid phase and a gas phase with a first gas/liquid separator, wherein the gas phase comprises both CO.sub.2 gas and hydrocarbon gas; cooling the gas phase with a first cooler; compressing the gas phase using a first compressor into a compressed stream; mixing the compressed stream with an external source of CO.sub.2 to form an injection stream; and injecting the injection stream into the reservoir. Systems for EOR from an oil reservoir by CO.sub.2 flooding are also disclosed.

Methods of Enhanced Oil Recovery (EOR) from an oil reservoir by CO.sub.2 flooding are disclosed. One method comprises producing a well stream from the reservoir; separating the well stream into a liquid phase and a gas phase with a first gas/liquid separator, wherein the gas phase comprises both CO.sub.2 gas and hydrocarbon gas; cooling the gas phase with a first cooler; compressing the gas phase using a first compressor into a compressed stream; mixing the compressed stream with an external source of CO.sub.2 to form an injection stream; and injecting the injection stream into the reservoir. Systems for EOR from an oil reservoir by CO.sub.2 flooding are also disclosed.

A system and method for enhanced oil transport and storage are provided. Comprehensive energy recovery and generation systems are provided which supply a heated gas by product, such as carbon dioxide, which to heat oil stored in a storage tank or oil transported in a pipeline, which reduces the viscosity of the oil, thereby increasing the efficiency of the pipeline and the ability to store and transport the oil without sludge accumulations.