A process for the recovery of energy from a pressurised well stream containing a gas/liquid mixture, the process comprising: treating the well stream to a pre-separation process to separate it into gaseous and liquid phases, selecting appropriate proportions of said separated gaseous and liquid phases, recombining said selected proportions, and supplying the recombined mixture to the inlet of a rotary separation turbine, wherein said components are separated and energy is recovered from the flow by rotation of the turbine, said proportions of said gaseous and liquid phases being selected to produce an optimum mixture for supply to the rotary separation turbine.

A sub-sea submersible compressing apparatus having at least one compressor tank. A compressor tank is configured to receive gas from a gas/liquid separator and has an inlet for water. The compressor further comprises a pump to pump water from the compressor tank thereby drawing gas into the compressor tank from the gas/liquid separator. Valves are provided to shut off gas flow from the liquid/gas separator and to permit gas flow from the compressor tank to a predetermined location such as a recovery line for transferring the gas to the surface or other location. The gas contained within the compressor tank is compressed by allowing water to flow back into the compressor tank, thereby compressing the gas and forcing it from the compressor vessel. Two or more compressor tanks can be provided to facilitate a continuous operation by timing of the water flow to and from each of the compressor tanks.

A subsea multiphase fluid separation system and method are disclosed which provide for efficient and reliable remote separation operation at deep and ultra deep water depths including depths of ten thousand feet or more. The system is preferably of modular construction wherein the modules are secured in a single frame to be lowered as a unit to the seabed. The system utilizes reliable cyclonic operation. The sequence of process steps is designed to make the system more efficient as compared to surface separating systems and thereby permit a more compact size as is desirable for subsea operation. The method of operation includes up to five basic process steps with the initial step in one embodiment including cyclonically separating solids. In a presently preferred embodiment, the cyclonic solids separator is sized to eliminate solids greater than fifty microns. A second stage is directed to cyclonically removing bulk gas from the liquid in either a cyclone or auger separator. A liquid-liquid hydrocyclone for the third stage acts to preseparate the fluid either by separating and/or by coalescing oil droplets in a water continuous stream and/or water droplets in an oil continuous stream. A fourth stage gravity separator is significantly smaller for the flow throughput as compared to surface separating systems due to earlier separation processes and due to the option of subsequent oily-water separation in a deoiling liquid-liquid hydrocyclone.

In accordance with the present invention, a downhole separation tool is provided which utilizes a downhole separation chamber with a series of fluid regulators responsive to a formation fluid and constituent components for separate desirable formation yields from the less desirable yields prior to lifting the fluids to the surface. The separation chamber has an input for the formation fluid, a production output, and a disposal output, in a tree arrangement according to the density order of the fluids in the separation chamber. The input flow regulator is coupled to the separation chamber input, the production regulator is coupled to the production output, and the disposal regulator is coupled to the disposal output. Each of the regulators are responsive to a fluid density of the formation fluid, first constituent and remainder constituent, accordingly, to regulate the flow of the respective fluid. According to a method of the present invention of separating a production fluid downhole, a production fluid is flowed from a subterranean formation into a separation chamber. The production fluid is separated over a given residence time period into a series of constituent layers. The first constituent, such as oil, is lifted in a generally continuously manner when under sufficient pressure to the surface, and the remainder constituent, such as salt water, is disposed to a disposal layer in the subterranean formation.

A heated flowline electrical isolation joint is disclosed for introducing current into a pipe-in-pipe system having an outer and an inner pipe. A hub presents a load flange having tension and compression load shoulders on its terminal end and connects to the inner pipe on its other end. An end flange presents an end flange load shoulder on one end and a high strength, highly electrically insulative first ring separates the compression load shoulder from the end flange load shoulder which engage therethrough in a load bearing relationship. A plurality of o-ring seals secure the compression load shoulder-to-first ring-to-end flange load shoulder interfaces. A retainer flange connects to the end flange on one end and to the outer piper on the other end, encircling the hub and presenting a retainer flange load shoulder. A second high strength, highly electrically insulative ring separates the tension load shoulder of the hub from the retainer flange load shoulder which engage therethrough in a load bearing relationship. A plurality of o-ring seals securing the tension load shoulder-to-second ring-to-retainer flange load shoulder interfaces. An electrical feedthrough tubes receives an electrical penetrator which reaches through the retainer flange to electrical connection with the hub. An electrically insulative material in the annulus between the hub and the retainer flange and between the electrical penetrator and the electrical feedthrough tube secures electrical isolation across non-load bearing areas.