Horizontal directional drilling (HDD) has been an established technique since the 1930s, though it was originally used to provide relief to wells under enormous pressure. In fact, it was recognized at the national level after the process was used to save a large oil field in Conroe, Texas. Horizontal directional drilling is still used to relieve high pressure wells, but now it has an even more important application – increasing productivity in gas wells, particularly in shale plays.
Going Horizontal
It’s been a running theme in the oil and gas industry for decades – technology improves, and more energy sources are unlocked as a result. Horizontal directional drilling is a major step forward in this regard, as it allows access to all kinds of underground and subsea reservoirs that would otherwise be impossible to reach. And it makes sense even when there is no obstacle present, as drilling horizontally can dramatically improve productivity when utilized properly. Just how effective is horizontal directional drilling? Consider the numerous ways the technique has improved oil and gas extraction:
1. HDD can reach targets that would otherwise be impossible to get to. There are many reservoirs sitting under cities and protected lands. There are reservoirs that are beneath difficult to manage terrain. Vertical wells may be infeasible or even forbidden in these areas, leaving horizontal wells as the only option. Using horizontal drilling methods, it is possible to safely extract oil and gas from reservoirs under populated areas.
2. HDD can produce a relief well for high pressure situations. Even with sophisticated blowout prevention technology, extreme pressures can compromise a well and force a shutdown. The blowout preventers may avert disaster, but without some form of relief, the well will be too dangerous to continue operating. Horizontal directional drilling allows a crew to intersect the high pressure well and either reduce the pressure to safe levels or seal the well off permanently.
3. HDD can reduce the footprint of extraction operations. A single oil or gas field may require dozens of vertical wells to comprehensively map and drain the reservoir. With so many wells, drilling operations may take up a lot of space and require a lot of labor, time and money to scale up. Specifically, this means building an access road, drilling pad and pond for each vertical well. Horizontal wells can do the work of several vertical wells, however, and they can be kept close together to reduce the drilling footprint.
4. HDD can greatly improve access to a fractured reservoir. Occasionally, a promising excavation site turns out to be fractured, with branches full of valuable gas running off in parallel branches. A single vertical well won’t be able to access more than a couple of these branches at a time, whereas a horizontal well can cut through many at once, jumpstarting productivity and reducing the number of wells required to extract gas.
5. HDD increases the “pay zone” of a well. Oil and gas reservoirs form horizontally, sometimes extending for miles and miles. But it may only be several feet tall. So, for instance, if a vertical well is drilled into a well 20 feet tall, then the “pay zone” of that well (or the part of the well that is extracting oil or gas) will only be 20 feet long. If, however, a horizontal well is fished through the well lengthwise, the pay zone will be hundreds or thousands of feet long, multiplying productivity by several times.
6. HDD may be the only answer to certain types of rock. Vertical wells work best in high permeability fields, as less pressure is needed to push the oil or gas into the well. In denser, less permeable rock, a vertical well will have trouble exerting the pressure needed to drag in valuable material. A horizontal well can be pushed through a reservoir, placing it closer to the oil or gas, and can be used to punch a hole through tough rock, loosening it up and increasing its permeability.
7. HDD is a go-to method when fracking. The increasing prevalence of fracking has made horizontal drilling even more important, as a horizontal well can more easily deliver high pressure fluid to pores of dense rock saturated with valuable hydrocarbons.
The only challenges with horizontal directional drilling is that it tends to be more expensive, as constant surveying is required to ensure the well is on target, and that it takes additional technologies to execute. These challenges, though, have been largely mitigated over the decades, and modern horizontal drilling methods are nearly as sustainable and expedient as vertical drilling. As processes and technology are perfected further, horizontal drilling will continue to be a valuable tool for oil and gas companies.
And supporting those drilling operations will be polyurethane components, which can provide material handling at the surface, or material stability in punishing down hole operations.