Both hydraulic and electric downhole motors were applied to directional drilling and allowed significant improvements in well construction. The overall drilling speed and in many cases drilling costs of the directional wells were equalized with vertical wells. In these circumstances, the directional drilling techniques became useful not only as a method of borehole construction for special cases but also as industrial technology for development drilling. The latter appeared to be true in both deepwater and onshore in complicated geographic and topographic environments.

The second stage of directional drilling technology development, characterized by the grouping of wells at one location, provided for significant modification of oilfield development. Labor productivity in both drilling and production was increased; length of communication lines and surface construction costs were decreased. Seasonal work in high latitudes was eliminated and environmental impact dramatically reduced. The further improvement in cluster drilling techniques for wells 2500 3000 m deep can be tied with the implementation of dual-bore drilling technology.

The third and major stage in the development of directional drilling technology proved to be horizontal and multilateral wells. Drilling horizontal boreholes into production reservoir significantly increased the flow rates and fluid recovery. This up-to-date horizontal and multilateral drilling technology allowed fulfillment of predetermined system-defined development of new oil and gas fields by drilling both production and injections wells. In some circumstances, horizontal drilling can be effectively combined with the cluster drilling approach. Horizontal and multilateral drilling may be also used in exploratory drilling, providing a decrease in the number...