Back to top

Level and Flow Wellhead Instrumentation Enhances Safety and Performance

Reliable wellhead instrumentation for level and flow control is critical to efficient processing and safety shutdown systems required of demanding production applications. The following steps in the wellhead production stream offer opportunities to realize better performance from your wellhead equipment, using level and flow measurement.

WELLSTREAM SEPARATORS
Separators are large drums designed to separate wellstreams into their individual components. They are commonly designed to separate two-phase (gas/liquid) or three-phase (gas/crude/water) wellstreams. Separators are also classified according to horizontal or vertical configuration, operating pressure, turbulent or laminar flow, and test or production separation.

Challenges:
Interface level measurement will actuate a valve to adjust vessel level in the oil separation process. An emulsion layer along the oil/water interface can contaminate the oil with water or the water with oil. Foaming along the gas/liquid interface, if entrained, can cause liquid carryover or gas blow-by.

Level Technologies:
• Continuous Level and Interface Level – Provides effective level measurement of gas/liquid interface that is insensitive to foam, to prevent liquid carryover or gas blow-by. Recommended: Eclipse® Model 706 guided wave radar transmitter
• Visual Indication – Delivers technology redundancy and diversity, especially in remote, power-challenged sites where non-powered visual indication is preferred. Recommended: Orion Instruments® AtlasTM or Aurora® magnetic level indicator, or Jupiter® magnetostrictive transmitter
• Flow Indication – Detects water level to activate shut-off. Recommended: Thermatel® Model TD2 flow/level/interface switch

PROCESS AND STORAGE TANKS
Crude oil and water are stored at the wellhead. Unlike midstream tank farms at terminals and refineries, field storage consists of smaller vessels associated with oil and water processing. Diesel generator fuel, potable water and fire water are also stored.

Challenges:
Wellhead instrumentation that monitors level can provide overflow control and alarm systems or shut down pumps when level falls below the specified low level. Interface controls will sense the beginning of an oil/water interface during tank dewatering and control the water draw-off.

Technologies:
For Oil Tanks:
• Continuous Level and Interface Level – Provides effective level measurement of gas/liquid interface that is insensitive to foam, to prevent liquid carryover or gas blow-by. Recommended: ECLIPSE Model 706 guided wave radar transmitter
• Point Level – Effective “high alarm” device for overfill prevention. Recommended: Echotel® Model 961 ultrasonic level switch
• Visual Indication – Delivers technology redundancy and diversity, especially in remote, power-challenged sites where non-powered visual indication is preferred. Recommended: ORION INSTRUMENTS ATLAS or AURORA magnetic level indicator, or JUPITER magnetostrictive transmitter

For Water Tanks:
• Continuous Level – Effective level measurement across a wide range of process conditions. Recommended: Model R82 non-contact radar
• Point Level – Effective “high alarm” device for overfill prevention. Recommended: ECHOTEL Model 961 ultrasonic level switch
• Visual Indication – Delivers technology redundancy and diversity, especially in remote, power-challenged sites where non-powered visual indication is preferred. Recommended: ORION INSTRUMENTS ATLAS or AURORA magnetic level indicator, or JUPITER magnetostrictive transmitter

VAPOR RECOVERY UNIT
If allowed to escape into the atmosphere, hydrocarbon vapors diminish income through loss of hydrocarbon volume and create fire hazards and pollution problems. A vapor recovery unit (VRU) collects vapors from storage and loading facilities, reliquifies the vapors and returns the liquid hydrocarbons back to storage. Methods to recover vapors include absorption, condensation, adsorption and simple cooling.

Challenges:
A VRU is a simple, economical process unit that provides EPA compliance and improves operating economies by capturing up to 95% of fugitive emissions.

Technology:
• Continuous Flow Indication – Provides precise monitoring of hydrocarbon vapors and flared gases. Recommended: THERMATEL TA2 thermal dispersion mass flow meter

for more information, click the link.