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What pressures should be used in the remote fire gas gun volume chamber?
The remote fire gas gun volume chamber should normally be pressurized to 200 PSI in excess of well pressure. The gas gun, when energized, should supply a gas pulse which travels through the casing annulus gas and reflects from the collars and the liquid level. The pulse should reflect from all collars and the liquid level and an optimum acoustic data set would consist of collar reflections from the surface to the liquid level with a distinct liquid level reflection. Acoustic collar response from the surface all of the way to the liquid level is not required since the computerized Well Analyzer will filter the acoustic data and extrapolate from known collar responses down to the liquid level. However, the measured liquid level depth is more accurate when a maximum number of collar reflections are obtained. The minimum acceptable acoustic data set would give a few collars and a liquid level response. In general, the more pressure that is used in the gas gun volume chamber, the further down the well that the collar response is obtained and a more distinct liquid level will be obtained. However, if satisfactory results can be obtained with less gas pressure in the volume chamber, gas can be conserved by using less pressure in the gas gun volume chamber.
The collar and liquid level response from CO2 or nitrogen gas is be very similar. The pressure in a fully charged CO2 container is limited to 1,000 PSI at 80°F. Nitrogen gas can be used to charge the gas gun volume chamber to higher pressures if the nitrogen cylinder is fully charged. The limiting pressure on the remote fire gas gun is 2,000 PSI at normal operating conditions. Do not exceed the ratings of pressure gauges, pressure transducers and any other parts.