1984 and Beyond: The Advent of Horizontal Wells
Authors: Rao Vik 
Published: February 2015

The single most important productivity improvement in the history of the petroleum business may have been the implementation of horizontal wells. The engineering and economic challenges its early innovators faced were steep, but rapid advances between 1984 and 1994 progressively broke down the challenges. A Shell executive once confided to me that, in the early days of that period, one needed permission to plan horizontal wells, but by the late 1990s, one needed permission not to plan one. That is the hallmark of a "disruptive technology"—at first it is viewed with suspicion and elicits risk avoidance, but after industry acceptance, the technology becomes the norm and deviations from it are viewed with disapproval by the very people who questioned the technology in the first place.
In the late 1970s, Teleco perfected the technique to measure well position and direction while drilling. Then it and others added important lithology-marker technology in the form of natural gamma and resistivity measurement. The early days of measurement while drilling (MWD) were marked by low reliability, but the industry persevered because of the cost savings in not having to stop to make openhole position measurements. Positioning in 3D space was now available on the fly.

The First Reports
Horizontal wells were still a curiosity. Then, in the early 1980s, reports started trickling in of directional drillers trying something really different. They were making radical angular changes using a nonrotating drillstring, with a motor for propulsion and a bent sub for angle build. But instead of following convention, which called for pulling the string and drilling the new section without the bent sub and motor, they drilled ahead with the assembly, this time rotating the string and providing motive power by the rotary and the motor. The bent sub in a rotary mode held angle, and the steerable system was born.

Groundwork for Advancement
I still remember reading the first such report—I thought the authors were nuts! Bent sub flopping around: What would that do to the hole shape, and what about stressing the string? Well, as it turned out, these were tractable issues and one more brick was in the wall to enable efficient angled drilling. Note that, once again, the advance was to eliminate a rig-time hog. The significance was that the early horizontal wells cost roughly 2.7 times as much as conventional wells, and while well productivity was higher, reduction in well cost was an important objective in those days of decision silos that separated drilling and reservoir actions. There are some who believe, and I can be counted among them, that horizontal wells were a trigger for sustained integrated decision making, although clearly the shift to asset units, which occurred during the same time period, was a significant driver. Decisions about wells were made now not by functional units, but by asset teams made up of representatives from the functional units. These events, together with the key advent of formation evaluation while drilling (FEWD), laid the groundwork for this significant advance.