1. A 3" 15,000 psig Sub Sea Test Tree allows the landing string to be unlatched in the event of anchor failure or as a precaution in the case of bad weather. The well is sealed by a proven twin ball fail safe valve assembly that also provides an injection point for chemicals should there be a risk of hydrates. 2. A 3" 15,000 psig Retainer Valve is available and will act in conjunction with the SSTT and when
closed prevents the escape of hydrocarbons into the annulus when the landing string is unlatched at the SSTT. Entry of wireline tools is simplified by a 3" 15,000 psig Lubricator Valve that is placed below the rotary table thereby reducing the need for long lengths of surface lubricator above the flowhead.
3. A 3" 15,000 psi Temperature Sub is placed below the temporary flow head and allows the temperature of the well fluid to be monitored prior to entering the flowhead and coflexip hose. Alternatively a tapped spool-piece can be inserted on the flow-wing outlet of the flowhead prior to the coflexip hose.
1.7
HIGH PRESSURE / TEMPERATURE WELL TESTING
5. A 2-9/16" 15,000 psig Lower Master Valve is placed below the temperature sub and swivel and can be either manually or hydraulically actuated.
6. A 2-9/16" 15,000 psig Temporary Flowhead is placed on top of the landing string above the rotary table and is equipped with a swivel that is immediately below the chemical injection sub to allow rotation of the flowhead or tubing prior to, and during testing operations. The surface flowhead is equipped with a failsafe actuated shutdown valve on the flow side which is operated by hi-lo pilots or remotely placed shutdown buttons. It can also have an hydraulically actuated kill-wing valve.
7. From the flow wing of the flowhead, the well effluent is conveyed by a 3” 15,000 psig Coflexip Flowline. The 15K production hose is suitable for H2S service and can handle Zinc Bromide and is also suitable for continuous use over a temperature range of -4F to 266F. A 2” 15,000 psig Coflexip Kill Line is placed between the rig manifold and a non-return valve on the kill side of the flowhead. 8. 3", 15,000 psig High Pressure Pipe with either Dynator or Grayloc C25 metal-to-metal seals is used to
connect the coflexip hose to the Data Header.
9. The 3" 15,000 psig Data Header allows upstream pressures and temperatures to be acquired and has sufficient ports for both manual and automatic data acquisition. A Data Header can also be placed downstream of the choke manifold, where reduced pressures make it easier to collect samples, etc. 10. The 2-9/16", 15,000 psig Choke Manifold is placed downstream of the data header and comprises a
four-valve assembly with an adjustable choke and a fixed choke complete with a full range of fixed chokes. A junk trap assembly can be placed on the inlet to remove any debris from the well stream. 11. 3", 10,000 psig Temporary Flowline fitted with Grayloc C25 metal-to-metal seals is used to take the
effluent to the steam exchanger. A Relief Valve and Relief Line is recommended to protect the flowline between the Choke Manifold and the Steam Exchanger in the event that the well flow becomes obstructed at the heater. Relief line sizing will have to be established once the flowing well conditions can be predicted.
12. The Heat Exchanger is provided with a 3", 10,000/10,000 coil or 10,000/5,000 psig split coil, a bypass to permit bypass of the heater coils and an adjustable choke should choking at the heater be required during the earlier part of the well test. For direct steam heat exchangers, a high-pressure pilot can be placed on the shell as an additional safety device. This will activate the ESD system in the event of a coil rupture or leak within the vessel.
13. A diesel fired Steam Generator is used to provide the steam for the heat exchanger and is a zone 2 unit. A zone I unit is also available, which can be tied into the ESD system to shut down in the event of an activation of the ESD system.
14. From the heater 3" fig. 602 5,000 psig Temporary Flowline is used to convey the heated fluid to the separator inlet. The pipework is fitted with 602 Weco connections with CO2 resistant elastomeric seals (Anson Superseals). A Relief Valve may be used to protect this leg of the process line in the event that a blockage occurs downstream, while flowing on Separator bypass.
15. At this point the surface equipment layout reverts to a normal 10K set-up, however careful consideration is given to the placing of Hi-Lo Pilots and shutdown valves so that the reaction times for the ESD System are as short as possible.
1.8
FOAMING OIL WELL TESTING
1. When the pressure is reduced on certain types of crude oils, foam (or froth) can be caused by the liberation of a large amount of micro bubbles in the oil as the gas comes out of solution, where these bubbles are encased in a thin film of oil. In other types of crude oil the viscosity and surface tension of the oil may mechanically lock gas in the oil and cause an effect similar to foam.
2. Where possible, sufficient information should have been made available from the operating company to allow for identification of a foaming problem before equipment mobilisation. This would allow equipment to be selected that best suits the needs of a foaming oil well and for chemical additives etc. to be chosen to help "break" the foam. However, it is essential that a close monitoring of well effluent behaviour, through the collection of samples, is carried out during the initial clean-up period of crude oil wells in order to ensure that there will be no problems with foaming oil during a test.
Presence of foam during a Well Test, if not treated can cause the following:- a) Prevent good separation and reduce separator capacity. b) Disrupt liquid and gas metering.
c) Disrupt pumping operations. d) Cause potential burning problems.
The main factors that increase foam volume and cause problems are :- a) High pressure drops.
b) Pressure drops occurring at low pressures. c) High volumes of produced gases.
The main factors that assist in "breaking" foaming oil are :- a) Settling
b) Agitation
c) Heat
1.8
FOAMING OIL WELL TESTING
1.8.1 PROBLEMS IN HANDLING FOAMING OILThe presence of foam during a well test, if not treated, can cause the following:- 1. Prevent good separation and reduce separator capacity.
2. Disrupt liquid and gas metering. 3. Disrupt pumping operations. 4. Cause potential burning problems.