Past and Present: NETL Contributions to Shale Gas Extraction

Horizontal drilling (A) gives a well more contact than a vertical one (B) within an oil or gas play.

Modern shale gas extraction (fracking) technology is attributed to George Mitchell who demonstrated extraction of natural gas from the Barnett Shale in Texas. However, George Mitchell's success is due in significant part to technology contributions by NETL and other government researchers.

Modern fracking technology is adapted from hydraulic fracturing. This technology was first demonstrated by NETL and DOE in 1977. The initial shale research efforts were sponsored by U.S. Department of Energy (DOE) and the Gas Research Institute in the late 1980s and early 1990s in the Lower Huron play that underlies southeastern Ohio, West Virginia and northern Kentucky.

George Mitchell learned of shale's potential from the Eastern Gas Shales Project, a partnership begun in 1976 between NETL and dozens of companies and universities that sought to demonstrate natural gas recovery in shale formations.

Three key technologies converged to enable modern shale gas extraction: micro-seismic analysis, which was developed by DOE laboratories; 3-D imaging, which was developed with DOE support; and horizontal drilling and well installation. In 1976, two NETL engineers, Joseph Pasini III and William K. Overby Jr., patented an early-stage directional drilling technology that became the precursor to horizontal drilling. Horizontal drilling was the breakthrough that could capture much more shale gas than conventional vertical wells. DOE also pioneered better drill bits and air-based drilling, which better protected the gas assets of geological formations.

Today NETL is conducting research to ensure that shale gas production will be an environmentally sound method of providing a clean energy resource as it becomes an extraordinary economic return on taxpayer investments.

Avoiding Leaks from Gas Wells

Aircraft fitted with geomagnetic survey instrumentation.

The oil and gas industry is seeking to take advantage of new resources in parts of the country where oil and gas production had taken place many decades ago, before modern environmental regulation and drilling practices were established. Many of these older wells may have been abandoned improperly, and if so, represent a pathway for modern wells to leak to the surface. One way of identifying old wells is to look for the steel casings by measuring perturbations in the earth magnetic field.

Recently, NETL participated in an aeromagnetic survey over approximately 1,800 acres of Washington County, Pennsylvania, where past oil and gas production had occurred and where future Marcellus Shale gas production is expected. The survey's purpose was to locate existing wells with vertical steel well casings.

Employing a helicopter fitted with magnetometer sensors, the survey was designed to optimize the detection of ferromagnetic targets that are susceptible to Earth-induced magnetization such as steel well casings. Survey conditions were selected to detect all significant magnetic anomalies. Conditions included flying 30 meters above the ground with close, nominal flight-line spacing to ensure a good overlap of signals, reduce potential terrain conflicts and maximize sensitivity. Proprietary hardware and software systems compensated for unwanted magnetic aberrations caused by the maneuvering of the helicopter, electronic interference, etc.

Preliminary results indicate that the survey correctly located known wells and identified numerous other magnetic anomalies that are likely to be wells. A ground investigation is underway to identify the ferromagnetic source for magnetic anomalies believed to be unknown wells, which if improperly plugged could compromise safe natural gas extraction operations.

Understanding Sources of Ground Water Contamination

Strontium isotopic ratios can distinguish water from the Marcellus Shale (is the deviation of the 87Sr/86Sr ratio from that of seawater in parts per 104.)

Extraction of natural gas by hydraulic fracturing of the Marcellus Shale results in significant quantities of produced water containing high total dissolved solids. Deep injection is the least expensive method for disposing produced water. However, only limited opportunities for deep injection exist in the areas of Pennsylvania where Marcellus Formation gas development is most intense. In these areas, increasingly greater volumes of produced water are being reused to hydraulically fracture subsequent wells. Where reuse is not practical, produced water is either treated for surface discharge or transported to nearby states where deep injection capacity exists.

Transporting and storing produced water prior to reuse, treatment, or deep injection may provide some opportunity for these waters to become commingled with surface water or shallow groundwater through spills or releases. Deeper groundwater also could be affected if the integrity of the well is compromised. Efforts to understand the impact of water produced from wells while drilling for gas in shale formations require that researchers be able to distinguish water that occurs naturally in the shale formation from other water sources in the surrounding geological formations.