The Genesis of TDR Multiphase Level Measurement A Magnetrol® Level Matters Series White Paper

INTRODUCTION Multiphase level measurements exist throughout the process industries and are particularly relevant in the Oil & Gas and Petrochemical sectors due to the value derived from effective water and hydrocarbon separation. While level instrumentation has come a long way in measuring liquids of all varieties, multiphase level measurement is often considered the greatest challenge and opportunity that exists today. This is evidenced by over half of separator failure modes being attributed to level instrumentation per Offshore Reliability Data (OREDA, 2002). Many technologies attempt to tackle...

EMULSION CHALLENGES When immiscible liquids reside in the same vessel, eventually the lighter liquid rises to the top and the heavier settles to the bottom. This is the case with oil and water, where effective separation is critical to the productivity of upstream wells, processing plants and refinery/petrochemical complexes. Gas Oil and water that undergoes emulsification is widely seen as the most difficult type of interface to control. Emulsion layer Water Sand A thick or dynamic emulsion layer creates challenges for one of the most widely utilized level technologies: Guided Wave Radar (GWR)....

GENESIS OF MULTIPHASE TDR An innovative approach was required to take advantage of the strengths of traditional TDR-based transmitters while improving upon the design to compensate for thick emulsion layers and potential sediment levels. A new TDR Multiphase Detector, aptly named Genesis®, was invented to dynamically measure thick emulsions and sediment levels. The measurement is accomplished by sending high frequency energy down the probe to detect upper level(s) while simultaneously sending energy back up the probe to detect various other levels that may be present. Genesis Multiphase Detector...

As with other technologies that contact the process, the probes are a critical element to maximizing the performance of Genesis. Probes will range from a large diameter coaxial to a completely new Pentarod design. The Pentarod is a fiveconductor probe with four reference rods surrounding a PFA coated active center rod. The concentrated signal yields coaxial-like performance; yet it has an “open” design that is less susceptible to measurement errors due to media buildup or bridging. The PFA coated center rods, aside from improved resistance to heavy coating, allow the pulse to travel in water...

TABLE 1: LEVEL TECHNOLOGIES IN INTERFACE SERVICE WITH THICK EMULSIONS TECHNOLOGY TOTAL LEVEL SAND / SEDIMENT Thick emulsion layers TDR MULTIPHASE DETECTOR (GENESIS) TDR-based with concentrated topdown and bottom-up signals for multiphase measurement No calibration or density dependency Lower upfront cost relative to profilers Higher power consumption and price point compared to GWR Buildup detection GUIDED WAVE RADAR TDR-based with signal concentrated down the probe reflecting off the liquid level(s) when impedance changes are detected DIFFERENTIAL PRESSURE Inferred interface measurement near...

REALIZING OPERATIONAL IMPROVEMENT Liquid-liquid separation is fundamental throughout the Oil & Gas value chains. Level measurement is the primary method of tracking fluid interface and the following are a few core applications with thick/dynamic emulsion layers where enhanced multiphase measurement improves productivity, safety and ultimately profitability. DESALTERS At the early stages of a refinery, a desalter separates water and salts/ chlorides/sediment from crude oil to mitigate effects on downstream equipment—particularly corrosion caused by chlorides. If water is carried through to the...

SEPARATORS Most upstream liquid-liquid separators are designed to separate immiscible liquids by gravitational force as the higher density liquid falls to the bottom while the lighter liquid rises to the top. These can be two-phase or three-phase separators in a variety of shapes. As with any separation process, particularly upstream Oil & Gas, it is imperative to maximize profitability by recovering as much of the oil as possible while limiting oil removal mixed in with the water. Better visibility into the thickness of the emulsion layer helps accomplish this. Another difficulty often found...