Horizontal drilling what is

This method significantly reduced the footprint of natural gas development within the campus area. Maximize pay zone: If a vertical well is drilled through a foot-thick reservoir rock, then natural gas or oil can seep into the well through 50 linear feet of "pay zone. Some horizontal wells have over one mile of pay zone penetration. If a rock unit is fifty feet thick, a vertical well drilled through it would have a pay zone that is fifty feet in length.

However, if the well is turned and drilled horizontally through the rock unit for five thousand feet, then that single well will have a pay zone that is five thousand feet long - this will usually result in a significant productivity increase for the well. When combined with hydraulic fracturing , horizontal drilling can convert unproductive shales into fantastic reservoir rocks.

Fractured reservoir: Some reservoirs have most of their pore spaces in the form of fractures. Successful wells must penetrate fractures to have a flow of natural gas into the well.

In many geographic areas there is a dominant fracture direction along which most of the fractures are aligned. If the well is drilled perpendicular to the plane of these fractures, then a maximum number of fractures will be penetrated.

This is done by drilling in a direction that intersects a maximum number of fractures. The drilling direction will normally be at right angles to the dominant fracture direction.

Geothermal fields in granite bedrock usually get nearly all of their water exchange from fractures. Drilling at right angles to the dominant fracture direction will drive the well through a maximum number of fractures.

If a well is out of control, a "relief well" can be drilled to intersect it. The intersecting well can be used to seal the original well or to relieve pressure in the out-of-control well. Horizontal drilling has been used to install gas and electric lines that must cross a river, cross a road, or travel under a city.

Relief well: If a well has a problem and begins to flow out of control, it must be sealed at depth or the pressure must be relieved. In this situation a "relief well" can be drilled from a nearby site. The relief well will be a directionally drilled well that intersects the bore of the problem well to drain off some of the pressure or to plug the well by pumping cement into the bore.

Vertical wells can effectively drain rock units that have a very high permeability. Fluids in those rock units can flow quickly and efficiently into a well over long distances. However, where permeability is very low, fluids move very slowly through the rock and do not travel long distances to reach a well bore.

Horizontal drilling can increase the productivity in low-permeability rocks by bringing the well bore much closer to the source of the fluid. Horizontal drilling is accomplished through the use of whipstocks, bottomhole assembly BHA configurations, instruments to measure the path of the wellbore in three-dimensional space, data links to communicate measurements taken downhole to the surface, mud motors and special BHA components, including rotary steerable systems and drill bits. While many techniques can accomplish this, the general concept is simple: Direct the bit in the direction that one wants to drill.

By placing a bend near the bit in a downhole steerable mud motor , the bend points the bit in a direction different from the axis of the wellbore when the entire drillstring is not rotating. By pumping mud through the mud motor, the bit turns while the drillstring does not rotate, allowing the bit to drill in the direction it points.

It involves the use of a directional drilling machine, and associated attachments, to accurately drill along the chosen bore path and back ream the required pipe. The first stage consists of drilling a small diameter pilot hole.

Drilling fluid is pumped through the drill pipe to the drill bit where high pressure jets and the bit will grind the soils ahead of the drill stem. The drilling fluid will also carry the cuttings back to the entrance pit at the drill rig. Tracking of the pilot hole can be done in several ways depending on the size and complexity of the shot.

Smaller shots are done using a walkover guidance system whereas the larger more complex shots have a wire line magnetics type system. With both methods there is a transmitter or steering tool located near the drill head which sends a signal to the location engineer giving the exact coordinates of the drill stem. The angle of the drill bit in use can be adjusted by a computer using global positioning signals GPS to pinpoint the location of the bit in relation to the oil or gas field.

Horizontal drilling has become a valuable technique in recent years due to certain advantages over traditional vertical drilling. It permits access to subsurface reservoirs that may not be accessible from directly above. Horizontal drilling also allows one drilling pad, or kickoff point, to explore a broader underground area. Horizontal drilling can also be used to seal off—or relieve pressure on—an out of control well by drilling an adjacent relief well.

Finally, beyond the purpose of oil extraction, horizontal drilling can be useful in the construction of underground pipelines or utility lines that need to travel beneath a river or an existing building. Horizontal wells have proven particularly useful as a component of the hydraulic fracturing process. Fracking helps extract natural gas and oil from huge shale reservoirs in the U. These deposits tend to be inaccessible to traditional vertical drilling due to the impermeability of the shale formations.

Instead, oil and gas companies drill horizontally into the shale and pump a compound of water, chemicals, and guar gum—also known as mud—into the shale. The force of these injections fractures the rock, creating openings through which petroleum and natural gas flow.

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