Page 304 - Intelligent Digital Oil And Gas Fields

252 Intelligent Digital Oil and Gas Fields

7.2 TYPES OF DOWN-HOLE VALVES

Service companies have created different types of control valves,
which are classified based on their structure and main functions. The main
categories include passive, autonomous passive, and reactive-actionable
valves, which are all explained in this section.

7.2.1 Passive Valves
This classification includes ICDs, which restrict flow by creating additional
flow rate-dependent pressure drops. The ICD generates an equalized pressure
drop across the horizontal section avoiding early water- or gas-flow break-
through. The ICD is preinstalled at the surface with the completion jewelry;
once installed the orifices cannot be adjusted through time. It is called
“passive” because there is no adjustment available on the orifice geometry.
However, the potential benefit of an ICD is that this mechanism creates a
homogenous pressure drop, equalizing the flowing bottom-hole pressure
across the lateral length. Fig. 7.3 shows a schematic example of an oil well
completion with and without ICDs which illustrates the reduction of gas
or water coning by equalizing pressure distribution along the lateral.

7.2.2 Autonomous Passive Valves
A relatively new breakthrough technology developed by different service
companies, the autonomous ICD (AICD) was created to bypass the water
and gas by using centrifugation principle or differential density. This new
tool is a self-regulating flow control device capable of controlling the fluids
flowing through internal discs. Fig. 7.4 shows an example of an AICD,
which shows oil and water flowing together through the ICD orifice; grav-
ity and differential density cause oil to go directly to the outlet of the ICD,

Fig. 7.3 Comparison of water or gas front with or without ICD completion.