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and a cavity depth versus cavity volume relationship will be <br />established. This relationship can be used to cross check the seismic <br />representation of the cavity shape and size. <br />Downhole Seismic Measurements and Modeling <br />The general procedure is as follows: <br />1. The well will be placed on standby. <br />2. Wireline explosive charges will be lowered down the long 4'/'tubing <br />string on the well. <br />3. Ten hydrophones will be lowered down the short 4 %' tubing string on the <br />well. <br />4. The perforating charges will be detonated and seismic signals will be <br />recorded by the hydrophones. <br />5. The process will be repeated to insure that sufficient information is <br />available to characterize the shape of the upper one half to two thirds of <br />the cavity. <br />6. NSA Geotechnical Services (NSA) will perform the seismic measurements <br />and the seismic interpretation. <br />NSA proposes using TRTT"" to perform a test survey for one cavern. The <br />survey will be conducted using groups (arrays) of sources and receivers in three <br />(3) configurations. The receiver array consists of 10 high-temperature <br />accelerometers spaced 20 feet apart. The source array consists of a series of 5 <br />to 20 small explosive charges spaced 20 feet apart and detonated sequentially. <br />If possible, a desired number of charges should be wired together and lowered to <br />the required depth in the long hole and detonated individually from the bottom up. <br />Instantaneous charges from the same lot should be used for the entire survey. <br />Data for all configurations will be recorded on a seismograph to be processed <br />later by the TRTT^" software. <br />Configuration 1: The receivers will be lowered down the short 4'/~' tubing until <br />the entire array is below the gas cap. A total of up to 20 sources will be lowered <br />into the long 4 %_" tubing until the highest source is 10 feet below the top receiver. <br />The sources will be detonated sequentially, lowest to highest. <br />Configuration 2: Configuration 2 will require the gas cap be removed and <br />replaced by fluid. The receivers will be lowered down the short 4'/2' tubing until <br />the entire array is below the gas cap. The sources will be lowered into the long 4 <br />'/_' tubing until the highest source is 10-30 feet below the lowest receiver. The <br />sources will be detonated sequentially, lowest to highest. <br />Configuration 3: The sources will be lowered down the long 4'/z" tubing until the <br />lowest source is 30 to 50 feet above the top of the cavern (gas cap filled with <br />