Directional Drilling Engineering Guide
1- Petroleum Geology Overview
Petroleum Geology Overview for directional drillers. in this article, we shall discuss different types of rocks which is drilled in the oilfield.
2- Positioning and Coordinate Systems Overview
Important Definitions for the directional drilling engineer to be aware of the coordinates systems and the grid, magnetic, true north
3- Direction Drilling Depth Reference And Geographic Reference
The trajectory of a deviated well must be carefully planned so that the most efficient trajectory is used to drill between the rig and the target location and ensure that the well is drilled for the least amount of money possible. The most important two items are the depth reference and the geographic reference.
When planning, and subsequently drilling the well, the position of all points along the well path and therefore the trajectory of the well must be considered in three dimensions.
4- Planning & Calculating The Trajectory
Nowadays there are software programs that work on these mathematical equations to solve them and give you the results but it is good to know what you have and what you can get from it
5- Deflection Tools
There are a number of tools and techniques which can be used to change the direction in which a bit will drill. These tools and techniques can be used to change the inclination or the azimuthal direction of the wellbore or both. All of these tools and techniques work on one of two basic principles. The first principle is to introduce a bit tilt angle into the axis of the BHA just above the bit and the second is to introduce a side force to the bit (See Figure 5). The introduction of a tilt angle or side force to the bit will result in the bit drilling off at an angle to the current trajectory. The major tools currently used for this purpose are:
- Bent Sub and Positive Displacement Motor
- Non-Rotating Steerable Drilling Systems
- Rotary Steerable System
- Directional Bottom Hole Assemblies (BHA)
6- Directional Surveying
When drilling a directional well, the actual trajectory of the well must be regularly checked to ensure that it is in agreement with the planned trajectory. This is done by surveying the position of the well at regular intervals. These surveys will be taken at very close intervals (30’) in the critical sections (e.g. in the build-up section) of the well. Whilst drilling the long tangential section of the well, surveys may only be required every 120′. The surveying program will generally be specified in the drilling program. If it is found that the well is not being drilled along its planned course, a directional orientation tool must be run to bring the well back on course. In general, the earlier such problems are recognized the easier they are to be corrected. Surveying therefore plays a vital role in directional drilling.