straight hole drilling may be a special case of directional drilling where an try is made out to keep the hole vertical. a few reasons for wanting out to keep the hole vertical are :
a. out to keep from crossing lease lines ;
b. out to keep among the specifications of the drilling contract ;
c. out to keep among the well spacing requirements because we are part of a developed field
there will be special cases when multiple sands are drilled with one wellbore. where steeply dipping sand zones are sealed by an unconformity, fault, or salt dome overhang, variety of vertical wells might possibly be needed to actually manufacture every sand, which you ll realize are separated by a permeability barrier. in spite of this, all the sand zones often is penetrated with one directionally drilled well thereby greatly reducing the price of production
directional drilling can be applicable in fault drilling. it is typically troublesome to actually drill a vertical well because we are part of a steeply dipping, inclined fault plane. usually, the bit can deflect when passing in the fault plane, and typically the bit can follow the fault plane. to actually avoid the challenge, the well often is drilled upon the upthrown or downthrown side on your fault and deflected into your manufacturing formation. the bit can cross the fault at enough associated with an angle exactly where the direction on your bit can't amendment to actually follow the fault.
a highly specialized application for directional drilling is that the relief well. if a well blows out and is not accessible direct from surface, then a relief well is drilled to actually intersect the uncontrolled well close to the bottom. water or mud are then pumped in the relief well and into your uncontrolled well. since it is typically needed that the relief well intersect the uncontrolled well, the directional drilling has to actually be extremely precise and needs special tools. survey data isn't correct enough to actually intersect a wellbore at depth. proximity logging is needed when drilling relief wells.
Horizontal wells are used to increase productivity from low permeability reservoirs by increasing the amount of formation exposed to the wellbore. Additionally, numerous hydraulic fractures can be placed along a single wellbore to increase production and reduce the number of vertical wells required to drain the reservoir.
Another application of directional drilling is what is commonly termed extended reach drilling. As illustrated in Figure below, extended reach drilling is where wells have high inclinations and large horizontal displacements for the true vertical depth drilled. Extended reach drilling is used to develop reservoirs with fewer platforms or smaller sections of a reservoir where an additional platform cannot be economically justified. Extended reach drilling will become more popular as the cost of platforms in deeper water and severe environments becomes more expensive.
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