In gas well corrosion treatment by batch application, it is essential to know an accurate inhibitor fall rate for assessing necessary shut in time to avoid formation damage from contact with inhibitor, and to ensure full coverage of the inhibitor on the internal tubing wall. A series of experiments to measure the inhibitor fall rate using a “gradiomanometer” tool have been conducted in nine (9) gas wells. One of the important parameters involved in the batch application is the corrosion inhibitor fall rate. This paper presents a study to determine the actual corrosion itilbitor fall rate in several tubing sizes and types, and at several different tubing pressures. However, the focus of this paper is on the methodology
used to generate the data, not the data itself. The experiments were performed by locating the “gradiomanometer” tool just above the plug or
above the liquid level in the well, and pumping the inhibitor into the well. Pressure differential indications between two sensors on the tool enabled the falling time to be measured, and the fall rate calculated. The
tubings used for the experiments were from two types; one was internally coated using a type of “modified phenolic”, and the other was uncoated tubing. The generic chemistry of the corrosion inhibitor used for this
experiment is “a partially neutralised C 18+ long chain complex Amine”. The result indicated the average fall rate of 4521 ft/hr (0.383 m/s) for the uncoated tubing, and 5355 ft/hr (0.453 m/s) for the coated tubing, with an overall average of 4760 ft/hr (0.403 m/s). After rounding, these figures can be used for assessing the required shut in time when conducting batch corrosion treatment. Keywords: fall rate, corrosion inhibitor, gas well, gradiomanometer, batch treatment, shut in time, field experiment, electrical wireline pressure differential sensor.