Shale Gas Development

Development of a shale gas reservoir requires drilling horizontal wells in order to extract all of the reserves in the gas field. Horizontal wells in the Marcellus Shale with a length of 5000 feet (1500 m) can drain 80 to 120 acres if effectively fracture stimulated. A 100,000-acre (400 square km) lease block can therefore support up to one thousand horizontal wells. The horizontal wells are drilled from drilling pads that each have 4 to 8 wells, in order to minimize the surface impacts of the drilling project and reduced the development costs.

The horizontal wells that penetrate the shale gas reservoir must be steered in order to stay within the productive zone. The steering is done with measurement-while-drilling technology (MWD), using the gamma-ray tool as the device that enables the location of the drill bit within the reservoir to be determined. An example of how a horizontal well was steered through the Marcellus Shale is shown on the following cross-section: