Patent ID: 6829928
Filing Date: 2004-12-14
Classification: E21B

Abstract:
A method for gauging water and non-electrically conductive light or dense non-aqueous liquid contaminants, LNAPL or DNAPL respectively, that can eliminate cross-contamination between wells comprising the steps of:(a) installing an elongated sensor extending down the entire length of a well, said elongated sensor having (a-1) a conductive liquid circuit, including a first resistive network extending down the entire length of the well, for sensing electrically conductive liquids only; together with (a-2) a hydrostatic circuit that responds to the actuation pressure of conductive and non-conductive liquids, said hydrostatic sensing circuit including a second resistive network extending down the entire length of the well; together with (a-3) a well depth sensing circuit, including a third resistive network extending down the entire length of the well; (b) after completion of installation of the elongated sensor in accordance with step (a), measuring the electrical resistance of the first resistive network of said conductive liquid circuit from the top of the well to produce a conductive liquid depth signal indicating the depth of the electrically conductive liquid in the well; (c) after completion of installation in accordance with step (a), measuring the electrical resistance of the second resistive network of said hydrostatic circuit from the top of the well to produce all liquid depth signal indicating the depth of all liquids including said LNAPL in the well if present; (d) after completion of installation in accordance with step (a), comparing the measured resistance of the hydrostatic circuit with the measured resistance of the conductive liquid circuit and recording any difference therebetween indicative of the thickness of the LNAPL layer; (e) after completion of installation in accordance with step (a), measuring the resistance of the conductive liquid circuit from the bottom of the well and recording this measured resistance from the bottom of the well as indicative of the thickness of said DNAPL; (f) after completion of installation in accordance with strep (a), measuring the resistance of said third resistive network indicating the length of said well mud subtracting the measured resistance recorded in accordance with step (e) from the resistance of said third resistive network to record the depth of a DNAPL layer if present; (g) after completion of installation in accordance with step (a), subtracting the measured resistance of the conductive liquid circuit in the measured resistance of said third restive network to record the height of the conductive liquid column.