As well, the hydraulic fracturing utilized in most horizontal wells poses a water contamination risk as a result of the chemicals used in the fracturing fluid. On the plus side, horizontal welling has reduced the surface footprint of oil extraction considerably, since much more of the hydrocarbon resource can be extracted from one site.
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Horizontal Drilling Comes of Age. Oil Field Review 2 3 : SPE Drill Eng 7 2 : Categories : 1. Navigation menu Personal tools Log in. Namespaces Read Discussion. Views Read View source View history. Navigation Main page Recent changes Glossary Pet. Handbook Taxonomy Wanted page Random page Help. This method is used when they must cross a road where excavation would disrupt traffic, cross a river where excavation is impossible, or transverse a community where surface installation by excavation would be extremely expensive and disrupting.
Perhaps the most important role that horizontal drilling has played is in development of the natural gas shale plays. These low-permeability rock units contain significant amounts of gas and are present beneath very large parts of North America.
In these rock units the challenge is not "finding" the reservoir; the challenge is recovering the gas from very tiny pore spaces in a low-permeability rock unit. To stimulate the productivity of wells in organic-rich shales, companies drill horizontally through the rock unit and then use hydraulic fracturing to produce artificial permeability that is propped open by frac sand.
Done together, horizontal drilling and hydraulic fracturing can make a productive well where a vertical well would have produced only a small amount of gas. Most horizontal wells begin at the surface as a vertical well. Drilling progresses until the drill bit is a few hundred feet above the target rock unit. At that point the pipe is pulled from the well and a hydraulic motor is attached between the drill bit and the drill pipe.
The hydraulic motor is powered by a flow of drilling mud down the drill pipe. It can rotate the drill bit without rotating the entire length of drill pipe between the bit and the surface. This allows the bit to drill a path that deviates from the orientation of the drill pipe. After the motor is installed, the bit and pipe are lowered back down the well, and the bit drills a path that steers the well bore from vertical to horizontal over a distance of a few hundred feet.
Once the well has been steered to the proper angle, straight-ahead drilling resumes and the well follows the target rock unit. Keeping the well in a thin rock unit requires careful navigation. Downhole instruments are used to determine the azimuth and orientation of the drilling. This information is used to steer the drill bit. Horizontal drilling is expensive. When combined with hydraulic fracturing, a well can cost up to three times as much per foot as drilling a vertical well.
The extra cost is usually recovered by increased production from the well. These methods can multiply the yield of natural gas or oil from a well. Many profitable wells would be failures without these methods. In the production of gas from a vertical well, the gas is produced beneath a single parcel of property. Most states have long-established mineral rights rules that govern the ownership of gas produced from vertical wells.
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Directional drilling is a technique used by oil-extraction companies in order to access oil in underground reserves. What Is Shale Oil? Shale oil is a type of oil found in shale rock formations that must be hydraulically fractured to extract. Read about the pros and cons of shale oil.
How Does a Vertical Well Works? A vertical well is a technique for accessing an underground reserve of oil or natural gas that involves drilling vertically into the ground. What Does Unconventional Oil Mean? Unconventional oil is crude oil that has been identified or extracted using novel methods. Re-fracking Re-fracking is the practice of returning to a previously fracked well to capitalize on newer, more effective extraction technologies.
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