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RISING RASTER DISPLAY

The atmospheric seepage mapped from an airborne platform can be seen using  “rising raster displays” (RRD) on a radar located on the ground.  Three RRDs will be shown: one over area without hydrocarbons and few hard targets such as trees and fences, one over an area without hydrocarbons but with many hard targets, and one over a known oil and gas field.

A rising raster display is created by pointing a radar with a pencil beam, directional antenna, along a fixed azimuth and recording subsequent returns over time.  Along the “X” axis is distance increasing to the right from the radar location.  Along the “Y” axis is time increasing upwards.  The result is a series of amplitude curves stacked one on top of the other as shown in the display below.  If the radar wave encounters a reflector and is reflected back to the antenna a curve will increase in height indicating an increase in amplitude.  The location of this echo can be determined relative to the radar.  The following examples come form the NRL’s 1993 work in West Texas.  Only every tenth return is shown in the RRD.

 

If along the line of sight of the radar there is nothing to reflection from then the series of lines, RRD, will look the same with little to no variation or amplitudes from line to line.  These are the “nonevent” areas in the figure above.  If there are a fixed object or objects present that reflect along the line of sight of the radar they will appear as an amplitude.  And since they are fixed they will appear in the same place with the same amplitude on each subsequent return as can be seen on the previous and subsequent figure.  In the above figure there are a number of hard targets that are marked.  Most of the RRD shows no activity. 

 

The figure above there are numerous hard targets between 700 feet and 1700 feet.  The hard target  returns were from trees and fence posts.  

The figure below is an RRD across an oil and gas field in southeastern New Mexico. 

Notice that at 750 to 1450 feet from the radar the amplitudes throughout subsequent returns display varying amplitudes from echo to echo, chaotic.  These are not from a hard target.  These are a reflector or reflectors that are changing very rapidly as the time difference between each radar trace is 0.01 second on the plot.  This type of return is that and seen with turbulence in the atmosphere.  Notice they fall within the field boundaries.  They conform to the location of the underlying oil and gas field.  Outside of the field we do not see reflections.  We conclude this chaotic pattern is the result of the index of refraction changes created by the mixing in the atmosphere of venting hydrocarbons.  The video below displays how these RRD anomalies appear from an airborne platform over a field in South Texas (it may take a moment to load).  

VIDEO FLYING FROM SEEPAGE TO NO SEEPAGE

The following display is a video of the actual radar screen flying from an area of seepage into an area of no seepage.  The seepage appears as yellowish-white “clouds” and “puffs”.  The difference between the two areas is readily apparent on the radar.  In the area of no seepage the faint linear features are fence rows.  Flight elevation is about 10 feet and speed about 115 MPH.

 

 

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