The careful planning of a project prior to the onset of directional operations is probably the most important factor in a project. Each well is virtually unique in the sense that it has specific objectives.
* Location .- The first thing to do is define the local coordinate system originated in the landmark structure. In many wells on land, this point can be the location of surface. The target location is then taken to the local coordinate system, if necessary.
* Target size .- During the drilling of a directional well, the well trajectory in relation to the target is constantly monitored. The technology available today allows us to drill wells accurate. The well drilling cost is heavily dependent on the required accuracy and acceptable limits should be clearly defined objective before the well.
* Cost vs. Accuracy .- This is the key. In many cases the operating companies take an arbitrary size tolerance of the target (radius of tolerance), particularly in multilateral wells. The radius of the target size often reflects an agreement, rather than the actual geological requirement well.
* Good communication .- Good communication with the departments of Geology and Exploration before the well can help prevent all sorts of errors. This is particularly true when contemplating a career as a correction in the well. THE first step in any plan to correct the azimuth of a well must always consult the department of geology.
* Profile Pozo .- Knowing the position of the surface location and determining the location of the target, expressed in TVD and rectangular coordinates, we can determine the best geometry of the profile of the well from surface to bottom of the well.
2. PLANNING INFORMATION FOR A DIRECTIONAL
Planning a directional well requires the following information:
1. Coordinates of the target surface (UTM, Lambert, or Geographic).
2. Size and shape of the target (s).
3. Local Reference coordinate (for multilateral wells).
4. Wellbore inclination required when entering the horizon of the target.
5. Predicted lithology (including types of training, TVD of the top of the formation, direction of dip of the formation).
6. Data Bits BHA proposed and used.
7. Program Types Pipe & Drilling Fluids.
8. Details of all the potential problems that may affect directional well planning and surveying requirements.
9. A list of records of surveys of all nearby wells can cause a collision hazard.
3. OUTLINE PARAMETERS OF A WELL
There are three specific parameters that must be taken into account when planning the trajectory of a well:
• Starting Point (KOP – Kick-off Point) .- The starting point is along the well depth measured which initiates a change in the inclination of the well and the same is directed to a particular address (in terms of North, South, East and West). In general, the most distant objects have a deep KOPmenos reducing the slope of the tangent section of the well.
It is usually easier to have the LAD surface formations in deeper formations. The LAD should start in formations that are stable and not those that cause problems, such as non-consolidated clays.
• Building System (BUR – Build-Up Rate) and System of Fall (Drop-Off Rate – DOR) .- The construction scheme and fall (expressed in degrees of inclination) are the regimes in which the well is deviated the vertical (usually measured in degrees per 100 feet pierced (º / 30m). regimens are elected on the basis of drilling experience in the location and the tools available, but arrangements between 1 to 3 degrees per 100 feet drilled are the most commonly used in conventional wells. Assess building surveyor greater than 3 ° / 100 ft are sometimes called «Paws Dog – Dog Legs.»
• Angle or Tilt Tangent (Tangent Angle – Drift) .- The angle of the tangent is the slope (in degrees from vertical) of a long straight section of the well after the construction of the well section. This section of the well is called «Section Tangent» because it is a tangent of the arc formed by the construction section of the well. The tangent angle is usually 10 to 60 degrees.