Production Process

The production of natural gas from the Marcellus Shale formation is important because it produces a clean-burning, Pennsylvania-based energy source in an environmentally sound manner. It also provides economic benefits to communities across the Commonwealth. Natural gas producers already invested more than $4 billion in Pennsylvania in lease and land acquisition, new well drilling, infrastructure development and community partnerships, with an even greater investment expected in the future.

Leasing

Gas producers begin the process of exploring and producing natural gas from the Marcellus Shale by obtaining gas and mineral rights from property owners interested in leasing their land for potential drilling activity. Land professionals or a "landman" conduct research in county courthouses for information on property owners and meet with those owners to develop a lease agreement giving the gas producer the right to drill for natural gas from their mineral estate. The lease typically includes a per-acre signing bonus for a specified number of years and an agreed-to royalty payment to the property owner if a drilled well produces natural gas. A number of market-based factors influence the terms included in each agreement.

Leases also include provisions to allow for the construction of underground gathering lines to transport natural gas from wells to larger transmission pipelines and processing plants. Landowners are compensated for the use of property needed for these pipelines, as well as other facilities that may be needed.

It is important to note that leases are legal and binding documents. The lease or "contract" represents the official written agreement between two parties, usually the gas company and the mineral/gas owner.

Exploration

Prior to drilling, gas producers like to gain a better understanding of the specific geologic conditions beneath the ground, and whether it has the potential to produce natural gas. Geophysicists use both two- and three-dimensional seismic testing approaches to learn about underground rock formations such as the Marcellus Shale. Seismic trucks are used to generate geologic images, sending shock waves into the ground that bounce off of rock formations and are reflected back to the surface and received by microphones or geophones that are strategically embedded in the ground and on the earth’s surface. Geophones translate the vibrations received from the ground into electrical signals, which are transmitted to a recording truck that logs the acquired data to be processed on a computer.

Three-dimension seismic testing, a more advanced tool, involves the placement of small charges into holes approximately 20 feet in depth on a grid and firing those charges in a timed sequence. Geophone instruments record the data generated by the test, showing three-dimensional images of the rock formations, including the Marcellus formation. By providing data about the location and thickness of the shale in that area, the three-dimensional seismic image helps geologists increase the probability of a more accurate placement of drilling locations.

However, these images cannot show whether the rocks contain natural gas. That requires drilling the well.

Drilling

Marcellus gas wells can be drilled vertically or horizontally. Vertical wells are sometimes first drilled in an area to obtain information valuable for planning the drilling of more costly and technically demanding horizontal wells. Marcellus Shale natural gas wells in Pennsylvania are drilled horizontally because it offers access to a larger quantity of natural gas while disturbing a smaller area on the surface. Both vertical and horizontal Marcellus Shale wells produce marketable quantities of natural gas.

The drilling process focuses first on reaching – and protecting – water-bearing zones beneath the ground. Drilling is completed using a small amount of lubricating agents, then the entire length of the well, from the surface to the groundwater strata, is cased and cemented tightly to form a barrier between the wellbore and the earth. As the drill continues to push deeper into the earth, a series of long drilling pipes follow it to establish the well. While drilling through the water barrier there may be short-term cloudiness or turbidity and diminishing of flow.

After drilling vertically to the depth that reaches slightly above the Marcellus Shale formation, the drill bit can then turn to push its way horizontally into the Marcellus Shale, sometimes as much as 5,000 feet, into the formation. This allows for the extraction of larger quantities of natural gas from a single wellhead. Marcellus Shale wells generally take between 15 – 30 days to drill, operating around the clock.

Casing the Well

The casing process keeps the well open and protects the earth, similar to the efforts to protect groundwater. The hard metal casing shores up the wellbore and extends through both the vertical (if the well is completed vertically) and the horizontal drilling phases, assuring the long-term integrity of the well from end-to-end. Cement is then pumped down the well under pressure and forced up the outside of the steel casing until the well column is sealed. The casing process ensures that the producing well is isolated from any fresh water zones. This assures during the producing life of the well that fracture fluids, produced brine water and natural gas are isolated and the freshwater bearing zones are protected.

Fracture Stimulation

Extracting natural gas from horizontal Marcellus Shale wells requires the use of more water than traditional shallow vertical wells, ranging between three and five million gallons of water per well. Gas producers must identify and obtain permits from the state regulatory agencies to withdraw water from streams or rivers, with additional oversight on limiting water withdrawals to protect fish and aquatic life.

Water used for fracturing is transported to the drilling pad where it is mixed carefully with sand and lubricating agents to fracture the well. The first step in the process involves setting a charge, similar to a rifle shot, in a specific area of the Marcellus Shale formation at the end of the well bore. Setting the charge perforates the casing and cement and starts the fracture of the shale formation, opening the interior of the casing to the formation. The water and sand mix is then injected under controlled high pressure to break open the formation, and expand and hold open the fractures, allowing the natural gas to flow to the well head.

The fracturing of a vertical Marcellus Shale well is completed when the drill reaches the Marcellus formation. The fracturing process for a horizontal well is typically done in stages, with each stage continuing in the same manner along the horizontal bore of the well, using a series of plugs to isolate the portions of the well that were previously fractured. Once all the fractures are established, a drill bit is sent into the well to drill through or remove each of the plugs, allowing the gas to flow from the multiple fracture points to the surface.

It can take several days to complete the fracture stimulation process, and requires continuous monitoring to ensure the safety of workers and the protection of the environment. Drilling companies invest millions of dollars to develop a single well. Protecting that investment through a safe operation and successful completion is the first priority for every well drilled.

After a successful fracturing procedure, wells are tested using a controlled flaring process and plugged while equipment is put in place to allow the well to move to the production phase. Some development areas have a pipleline ready to take the gas to market. In these areas, the producer will typically put the gas directly into the pipeline so there is no visual sign of flaring.

Pennsylvania's natural gas developers recognize that the drilling process is not without short-term inconveniences. The project requires a large fleet of trucks to service the site, including on an average of 400 trucks coming and going during the fracturing process, transporting water to and from the drill pad. Gas developers work with municipalities to post bond to protect and repair roads, post road flagmen when needed, and repair any impacts to the environment that may occur temporarily during the drilling process.