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Abstract A method is presented to plan a directional well through two targets, considering bit-walk, and determine the surface location that meets a given set of constraints. Introduction A common practice today in the petroleum industry is to drill a directional well following a planned trajectory, conceived in a 2-D plane configuration, and correcting for the spatial 3-D trajectory through the use of a "lead angle" at kick-off. Sometimes the estimate of the best lead angle is made based on subjective analysis of experienced field personnel in a given area, or there have been some attempts to quantify "bit-walk" in order to better estimate this angle. For most of these wells the target is intercepted within an acceptable range of error (even when the lead angle is incorrectly estimated) although in some cases, many trajectory corrections are needed in order to meet this goal. Steerable systems have partially solved these problems but can be prohibitive partially solved these problems but can be prohibitive in some cases due to economics. Things get even tougher when there is the need to intercept two targets. For this situation, the direction in which the first target is intersected can make it impossible to drill through the second target, for the amount of correction is limited, specially at higher inclination angles. The main purpose of this work was to attack this problem where there is the need to intercept two problem where there is the need to intercept two targets and bit walk is present, and develop a method and computer program that allows to plan the 3-D trajectory and follow the executed plan easily using any Personal Computer. Method The problem is solved in three steps: The first step comprises the calculation of the directional trajectory of the well in a vertical plane containing both targets (Figs. 1 and 2).To define the surface location, a straight line is drawn through both targets that intersects the end of the build up portion of the well (only the buildand-hold type trajectory is used). In order to limit this intersection to a unique point there is the need to define two out of three parameters: Kick-off point (KOP); Build-up rate (BUR); Horizontal Departure (HD). |
