Method for determining distance and direction from an open well to a cased well using resistivity and directional survey data

摘要

The invention disclosed herein is a method for determining distance and direction from an open well to a cased well. The method comprises: (1) utilizing resistivity logs obtained in the open well and/or in the cased well before casing is run to determine the thicknesses and resistivities of earth strata which are penetrated by the wells, (2) determining the actual trajectory in the subsurface of the open well from borehole directional survey data, (3) determining theoretically expected resistivities for long and short spaced electrode- type resistivity tools at various depths in the open well for different assumed positions of the cased well relative to the open well, (4) determining measured resistivities for long and short spaced electrode- type resistivity tools by logging the open well, (5) varying the assumed relative positions of the open and cased well to adjust the spacing of the resistivity curves until the expected resistivities match the measured resistivities in a best fit mathematical sense; the amount of variation in assumed relative position required to match the resistivity curves determining the distance of each station in the open well to the cased well, (6) determining the direction of the cased well from the open well by constructing a plan view of the open well trajectory from the directional survey data and utilizing the distances to casing previously determined.