![]() Multiple horizontal wells being drilled from the same pad decreases the site footprint. With horizontal wells, geologists now become part of the drilling operation, actively involved in steering the well along a desired geological profile and responding to feedback data in real-time as drilling occurs. With a vertical well a geologist’s role is primarily to evaluate “what has been drilled.” Technology advances have allowed horizontal laterals to be drilled in excess of a mile under very controlled conditions. There has been a significant increase in the number of horizontal wells in the US over the past two decades. These factors, in addition to drilling equipment advances, have made horizontal wells commercially viable. This reduced footprint makes horizontal drilling ideal for shale reservoirs that are shallow and spread out, fractured reservoirs like the Austin Chalk in Texas or for in drilling in sensitive environments. drill numerous (multi) wells from one location or padīecause horizontal drilling can drain a larger area, fewer are needed, which means less surface infrastructure.follow a complex structure, like a shale layer. ![]() intersect a larger number of fractures in certain geologies.increase exposure to producing zones structures. ![]() Wells commonly are turned to a horizontal direction to: ![]() Note that a horizontal well is deviated, but a deviated well may not be horizontal. Today, most wells drilled are deviated or horizontal. Though horizontal drilling is more costly, it can reach subsurface objectives that could not easily be reached with a vertical borehole. As shale plays which are wider than they are thick became economic, horizontal wells became dominant. Prior to the 1990’s vertical well drilling was the preferred method. The term for this technology is Measurement While Drilling, or MWD.ĭata links from the drill bit to the surface communicate these measurements to allow constant positional adjustment to the mud motors and BHA components. ![]() The directional driller also can alter other drilling parameters such as weight on the drill bit and rotary table speed to help direct the bit to the desired directional path.ĭownhole instruments continuously measure the path of the wellbore in three-dimensions. Some examples of these type of drilling tools are: mud motors, whipstocks, and sophisticated bottom-hole assembly (BHA) configurations. This is accomplished through the use of specialized steering mechanism or tools attached to the drillstring. Note that a horizontal well is deviated, but a deviated well may not be horizontal.” Directional Drillingĭirectional drilling is the intentional deviation of a wellbore from the path it would naturally take. “Today, most wells drilled are deviated or horizontal. In the drilling operation, most deviations occur naturally because of the flexibility of the drill string and its reaction to downhole geological structures, such as changes in formation density, or faults and dips in the rock strata that is being drilled through.Ī wellbore is often deliberately deviated to miss high-risk obstacles, such as adjacent producing or injection wells in a more developed field location.Īdditionally, deviation can be used to reach additional reservoirs when drilling “multi-wells” from a single drilling location – especially offshore.įinally, wells are also deviated to avoid risky drilling subsurface formations like salt layers. In the Directional Drilling lesson, we’ll discuss some common types of deviated oil and gas wells.ĭeviated Wells – Directional Drilling and Horizontal Drillingĭeviation is defined as the angle at which a wellbore diverges from the 90° vertical position. ![]()
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