Objective
The aim of the project is to give a field demonstration of the capability of a compact separation system implementing cyclonic forces to separate a mixture of gas, oil and water coming directly from wells. The system includes four static cyclones in series : one gas-liquid, two oil-water and one final hydrocyclone for water cleaning.
A prototype of the complete separation system has already been built and tested on a loop in the Kvaerner laboratory using an oil refinery cut and air. Further verification on real fluids has been planned in industrials laboratories during 1997. The field demonstration will prove the efficiency and operability of the system on fields; the critical aspects to be demonstrated will be the efficiency and reliability of the separation of the fluid coming directly from the wells. It is essential to demonstrate that the system is able to separate fluids with different properties; this is the reason why we have to plan testing on two different industrial sites.
The control system is an important element of the unit and it is necessary to demonstrate that it can operate on a field and cope with the variation of flowrates and slugging phenomena that can be experienced on oil & gas fields. The demonstration should prove that the separation system can be integrated in any conventional platform process, that it can also be operated on simple unmanned wellhead platforms and that it has potential for subsea applications.
Gas is separated from liquid in the first cyclone using a specially patented gas lock static arrangement; it is this special device that made gas-liquid separation in a static cyclone possible. When present, sand is also eliminated in the first cyclone and stored in a container which can be emptied when required. Gas is delivered to the gas drying process on the platform or sent into a transport pipeline when this installation is located on a simple wellhead platform.
The separated liquid flows through the second cyclone (first oil-water separator) which separates the bulk of the water from the oil. Typically 5% of the water is left in the oil and 5% of the oil in the water. Depending on the field development scheme, oil is delivered for further drying on the platform or transported to another platform or to shore. Water flows to the third separation cyclone (second oil-water separator); At the outlet of this cyclone it contains less than 1000 ppm oil, and it is sent to a conventional hydrocyclone which cleans it to the required specifications for discharge at sea (below 40 ppm oil in water) or for re-injection into the reservoir (below 500 ppm oil in water). For some applications the last hydrocyclone will not be required.
The main component for the control system is a water cut meter on the separated liquid from the first cyclone. It is the reading on this meter which sets the parameters for the separation in the cyclones. The oil flow from the two last cyclones is recycled to the inlet of the first oil-water cyclone separator in order to improve the overall separation quality in the system. The maximum capacity of the prototype is 20 m?/hour of liquid with a corresponding gas volume of 100 m?/h at separation conditions. The pressure drop in the separation system will depends on the flowrate, but will in any case be lower than 10 bar. The small amount of gas that could be separated due to the pressure drop will follow the oil flow.
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DEM - Demonstration contractsCoordinator
1361 Billingstad
Norway