Our goal in planning a well profile is to determine the most economic path from the surface to the bottom hole location. We first have to determine the target coordinates with respect to the proposed surface location. At the same time, we have to assign the target radius based on our well objectives. This target radius indicates how tightly we have to control the well trajectory. The degree of control is much less critical for a relatively thick homogeneous interval than it would be for a thin steeply dipping zone. Dog-leg Severity limits are based on drill string operating specs, completion considerations, and other factors. Note that it's possible to run into problems even when the departure from vertical is within an acceptable range. Here even though the inclination is within its assigned limit of 3˚/100ft, the dog-leg severity is too high. This illustrates the importance of measuring both inclination and direction even on vertical wells.
In laying out the well trajectory, we may start by looking at 4 general patterns: the (Build and Hold), (Build, Hold and Drop), (the Continuous Build) and (the Build, Hold and Build). Type1, the Build and Hold employs a shallow initial deflection from vertical and discreet angle approach to the target. It's good mainly for reaching single targets of moderate depths and sometimes for drilling deeper wells with large horizontal departures. Type2, the Build, Hold and Drop pattern likewise employs a relatively shallow deflection and holds angle until it reaches most of the desired lateral displacement. But then, the angle is reduced or brought back to vertical to reach the target. This pattern is primarily for wells and multiple pay zones or whether lease or target constraints. The Continuous Build pattern as a relatively deep initial deflection at which point hole angle is maintained to the target. This pattern is appropriate for salt dome drilling, fault drilling, sidetracking or re-drilling. The build hold and build pattern describes horizontal wells of which there are several types. Selection of this pattern is based primarily on reservoir engineering considerations. We can define well profiles in terms of several key parameters. The inclination angle is the deflection from vertical at a given point. While the kickoff point is the depth of which we first begin building the inclination angle. The Azimuth refers to the angle in the horizontal plan with respect to true north. The turn-off point is the depth of which we change Azimuth. The turn rate angle represents the incremental change in azimuth over a measured course length. While the build rate angle refers to the incremental increases in inclination. Conversely, the drop rate angle on a Build, Hold and Drop pattern is the incremental decrease in hole inclination. The lead angle measured in the horizontal plan from the left of the target area accounts for the tendency of a rotary bit to walk to the right. Its value depends on local drilling conditions.
But remembered that there's a lot more to planning a well profile in drawing a curve from point A to point B. many other factors: well spacing, casing and completion requirements, read capacity hydraulics, drill string design and specifications, drilling parameters and so forth come into play. There are a number of software packages that can be used to optimize well trajectories while accounting for these drilling variables..
But remembered that there's a lot more to planning a well profile in drawing a curve from point A to point B. many other factors: well spacing, casing and completion requirements, read capacity hydraulics, drill string design and specifications, drilling parameters and so forth come into play. There are a number of software packages that can be used to optimize well trajectories while accounting for these drilling variables..
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