May 07

In the mid-1970s, new technologies like steerable down-hole motor assemblies and measurement-while-drilling tools became more prevalent and allowed drilling to proceed at angles off of vertical. Drillers could now more easily turn the well bore to reach targets at a horizontal offset from the location of the wellhead. This opened up many new possibilities for improving production.

Three variations of directional drilling include extended-reach drilling, horizontal drilling, and multiple laterals off of a single main well bore.

Extended-Reach Drilling: In some situations, it is impractical or too expensive to drill wells from locations directly above the target formations. For example, offshore drilling is much more expensive than drilling from a shore-based facility. If the target formation is a mile from shore, it may be much more effective to directionally drill from a shore-based location. Another option involves using a single platform or drilling pad to drill multiple extended-reach wells in different directions or to different depths, thereby minimizing the number of surface well-pad facilities.

Horizontal Drilling: Some productive formations are not thick but extend over a large lateral area. Prior to the advent of directional drilling, such formations were either uneconomical or required multiple wells to recover the resources. Modern technology allows wells to be drilled and completed in a relatively thin horizontal layer. A single horizontal well can contact more of the resource and therefore takes the place of several traditional vertical wells. Because the well bore interval from surface to producing formation is drilled only once, a horizontal well generates less waste than several vertical wells.

 

Multiple Laterals: Some formations contain multiple, small, oil-bearing zones or zones at several different depths. To recover these resources using traditional vertical wells would require many wells. With directional drilling technology, lateral well bores can be drilled off of a main vertical well bore to reach individual targets. The main well bore is drilled only once, followed by drilling of several smaller-diameter laterals. The total volume of drilling waste is lower than would be generated if several full wells were drilled.

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