1984 and beyond: The advent of horizontal wells

Horizontal wells are perhaps the single most important productivity improvement in the history of the petroleum business. Horizontal wells helped realize the measurement of well position and direction while drilling during the 1970s. It was also key to the realization of lithology-marker technology in the form of natural gamma and resistivity measurement. Early advances involved the use of a nonrotating drillstring, with a motor for propulsion and a bent sub for angle build. The technique employed the rotation of a string and providing motive power by the rotary and the motor. Another supporting technology is the appearance of the first quantitative porosity sensor. Major advances in drilling were being made as well as well as the practical realization of 3D-seismic interpretation, which increased certainty regarding the location of sweet spots in the reservoir and provided a firmer basis for the increased productivity likely from a horizontal well.