Onshore Drilling (Part 3)

As of result of advances in horizontal drilling natural gas resources in shale basins has been more accessible leading to more diversified sources of natural gas. Combining this with other technologies such as seismic imaging has contributed to lower marginal operating and capital costs, which in turn allow natural gas producers to more economically extract natural gas from resources.

Horizontal drilling also permits the development of natural resources with minimal above-ground disturbance, reducing the environmental footprint of natural gas operations and the cost and potential disturbance of existing roads or other infrastructure. Directional drilling and horizontal drilling terms are often used interchangeably. Directional drilling refers to drilling at a slant or angle to increase contact with the resource. Horizontal drilling is a type of directional drilling. Horizontal drilling uses a technique known as hydraulic fracturing in order to extract natural gas from geologic formations. For more information please visit our hydraulic fracturing section. Measurement while drilling is something that is carefully done during this process. To fail to do so can be financially crippling - leaving plenty of money on the table.

Most wells drilled for water, oil, natural gas, information or other subsurface objectives are vertical wells - drilled straight down into the earth. However, drilling at an angle other than vertical can obtain information, hit targets and stimulate reservoirs in ways that can not be achieved with a vertical well. In these cases, an ability to accurately steer the well in directions and angles that depart from the vertical is a valuable ability.

When directional drilling is combined with hydraulic fracturing some rock units which were unproductive when drilled vertically can become fantastic producers of oil or natural gas. Examples are the Marcellus Shale of the Appalachian Basin and the Bakken Formation of North Dakota.

Why Drill Wells That Are Non-Vertical?

Directional and horizontal drilling have been used to reach targets beneath adjacent lands, reduce the footprint of gas field development, increase the length of the "pay zone" in a well, deliberately intersect fractures, construct relief wells and install utility service beneath lands where excavation is impossible or extremely expensive.

Sometimes a reservoir is located under a city or a park where drilling is impossible or forbidden. This reservoir might still be tapped if the drilling pad is located on the edge of the city or park and the well is drilled at an angle that will intersect the reservoir.

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.

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.