the sinking of a group of directional holes from a common platform of small area, on which the drilling rig and wellhead equipment are located. In multiple drilling, directional wells are drilled into the production zones at certain points.
Multiple drilling sometimes proves to be a more economically advantageous solution when developing gas and oil deposits offshore, in very swampy areas, or in areas with complex surface topography. In such cases, multiple drilling offers significant savings in the erection of platforms and derrick installation work. Multiple drilling, or the clustering of wellheads, reduces field drilling equipment expenditures and simplifies the automation of production and maintenance operations. In practice, the number of wells in a single group does not exceed 20, although 68 wells are known to have been drilled into the Gulf of California from a 60 X 60 m drilling island. The maximum bottom hole deflection, 2,000 m from the vertical, was reached in Western Siberia and in the Azerbaijan SSR.
The disadvantages of multiple drilling are increased expense and consumption of materials caused by the lengthening of the directional boreholes, and the reduced drilling rate. Simultaneous double and triple directional drilling, which is performed from a single drilling rig using one or two sets of drill pipes, is a variation of the multiple drilling method.