P rocess Description Figure 2: Flow Diagram for Alba Field Oil and Gas Processing and Corresponding Abbreviations of units

P rocess Description


Figure 2: Flow Diagram for Alba Field Oil and Gas Processing and Corresponding Abbreviations of units

F.S.S.	First Stage Separator	K.O.D.	Knockout Drum
T.S.	Test Separator	E.C.	Electrostatic Coalescer
D.U.	Degasser Unit	W.T.U.	Water Treatment Unit
HE	Heat Exchanger	C	Compressor
G.S.	Sweetener	S.D.	Salt Deposit

Table 1: Temperature of Vaporization for different compounds at different pressures
Figure 2 depicts the flow diagram along with all units that are used for initial treatment and processing of crude oil produced in Alba Field. The table which follows below the flow diagram is used to interpret the corresponding abbreviations for units that can be seen in the flow diagram. As it can be observed from the figure, the crude oil processing is comprised of several stages and in each stage of treatment with the aim of providing safe and secure segregation process of volatile constituents from the composition, the pressure value is being progressively reduced. The principal objective of the whole process is to achieve stabilized oil and gas content as well as to separate water from the content attaining the maximum feasible recovery factor. Flash vaporization which occurs due to great pressure drop leads pump damage, the stream flooding, the decline in production rate, etc.; therefore, to preclude something like this from happening, it is crucial to carry out the separation processes in several steps rather than performing the entire separation in a single stage.

As it is described in the flow diagram, from manifold which is at well-head temperature of ( ) the hydrocarbons fluids are flowing through RF-1, RF-2, RF-3 trains into FSS and TS which are both functioning at 9 bar and ( ). The percentage distribution of mass flowrates in different for FSS and TS, namely, 90% of the total mass flowrate is equally allocated to the streams entering FSS-1 and FSS-2, whilst the remaining 10% goes into TS-1. After the lines RF-1, RF-2 and RF-3, bypass lines are constructed in order to work under 2 scenarios: The first one of them is when the production newly started, in this case the gate valves on the RF-11, RF-13 and RF-15 are closed and the gate valves on the RF-5, RF-6 and RF-7 are kept open. The purpose can be explained by the fact that when the well is young, reservoir pressure is higher (approximately 50-60 bar at wellhead), but after some time reservoir pressure will decrease (minimum about 6-8 bar at wellhead) and 2^nd scenario is considered now. In 2^nd scenario, gate valves on the line RF-5, RF-6 and RF-7 are closed and gate valve on RF-11, RF-13 and RF-15 are kept open in order to maintain fluid flow through the pump, which in turn increase the pressure to the working pressure of the F.S.S. and T.S.

FSSs and TSs are gravity driven three-phase vertical separators which have large capacity vessels where the segregation process of oil, water, and gas takes place. Since the available area on offshore platforms is restricted, the units which have smaller areas are more preferred than those occupying large space; therefore, vertical separators were the choice instead of horizontal ones. The main function or purpose of usage of Test Separator is under certain conditions or circumstances to perform regular measurements of production rate from one or several wells. For the gas to settle at the top of the vessel and at the same time for water to settle down at the bottom of the vessel, the required residence time id approximately 5 minutes for FSSs and for TSs. The heat exchanger units (HE-1, HE-2, HE-3) which are positioned before FSSs and Ts units serve to either cool or heat the hydrocarbons to some value before they enter separation units. The decision whether to boil or cool the hydrocarbons is made based on the boiling temperatures of components of the crude oil which has low API value with the aim of precluding flash vaporization from happening and successfully separating light constituents. Moreover, to ensure that the required temperatures were achieved and, subsequently, to control temperatures, temperature control vales were put before HEs. The boiling temperatures of various heavy and light compounds together with water are outlined in