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Gas Facts
• Conventional vs. Coalbed Gas Wells
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Well Duration
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Surface Impact Reductions
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Gas Well Life Cycle
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Spacing Diagram
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Casing Diagram
Because the San Juan Basin is so rich in natural gas deposits, production in La Plata County will be active for many decades to come. How long will production continue and how many wells will be necessary to extract the natural gas deposits are questions that have been asked by many residents in La Plata County.
A projection report produced by the COGCC was presented to La Plata County. Another program, the 3M Project that will map, monitor and model natural gas information, was started in La Plata County in 1999. It combines the efforts and resources of the COGCC, the Bureau of Land Management and the Southern Ute Indian Tribe. Theses two projects can help area residents more fully understand the future of gas development in our county and help the federal, state and tribal authorities assess the environmental impact of that development.
In general, natural gas development in La Plata County will continue for at least several decades. As new technologies evolve, development and existing well spacing is subject to change at any time.
There are two types of natural gas wells in La Plata County, conventional and coalbed. Conventional gas wells are typically deeper (3,500 - 10,000 feet) and extract gas and oil from sandstone formations such as the Mesa Verde and Dakota. Coalbed gas wells generally range from 1,000 to 4,000 feet deep and extract gas from coal-bearing formations. The Fruitland formation is La Plata County's methane-rich coalbed formation.
Conventional wells initially produce large volumes of gas and very little water. Over time gas production declines and water increases. Coalbed wells are just the opposite, producing large quantities of water and low gas quantities at the beginning and, later, the water production declines and gas production increases.
Pump jacks at well sites are used to pump water and sometimes oil -- not gas. On a conventional gas well a pump jack is not necessary at the beginning, but may be added later to remove the increasing amounts of water. On a coalbed well, a pump jack is typically needed during the first few years and can be removed as the amount of water declines.
Conventional and coalbed methane gas wells are significantly deeper than domestic water wells. Natural gas wells are separated from the surrounding surface formations by "casings" discussed below. Geologic studies show that beds of nearly impermeable shale separate and retard vertical water movement between deep and shallow aquifers.
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All wells vary in the duration of natural gas production. Depending on a number of factors, wells can produce from a few years to 40 or 50 years. As advances in natural gas production continue, well duration may change based on how technology affects recovery.
During the productive life of a well, operators are responsible for various types of maintenance associated with the well as stipulated in the lease or other legal documents and/or required by the COGCC. These address issues such as weed control, safety, fencing associated with the well site, pipelines and roads. Wells are also required to be pressure tested so that potential leaks can be avoided. COGCC requires environmental protections during and sometimes after production.
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The natural gas industry is constantly striving to lessen the impacts to the surface. For every inch of surface property that is disturbed in the process of natural gas development, more money must be invested for construction and later reclamation. Relations between surface owners and production companies are enhanced if fewer surface impacts exist. In addition, COGCC rules require that drilling locations are "constructed in a manner that minimizes the total disturbed area." COGCC further requires that "existing access roads are to be used where possible, and oil and gas operators are encouraged to share access roads when developing a field. Operators are required to limit their travel to within original access road boundaries to reduce land damage." For all these reasons, it is in the best interest of natural gas production companies to reduce surface impacts.
Pad Size
People often wonder why a well pad needs to be as large as it is. The main reason is safety. A certain amount of space is required to separate the wellhead from surrounding wildlife, crops or residences. In addition, the well pad must be large enough to accommodate emergency equipment, should it ever be necessary. Finally, a well pad must accommodate the various maintenance and construction equipment necessary for smooth operations and repairs during the life of the well.
Directional Drilling
Most wells are drilled as close to vertical as possible. However, techniques have been developed that allow the production hole to be curved or drilled at an angle. This operation is called directional drilling and has made it possible to drill multiple wells from a single location or drill a well where a surface location is not directly over the gas target area.
There are limits to the degree that the well bore can deviate from the vertical and to the horizontal distance from the well surface site. Moreover, the limit of horizontal distance is affected by many factors, including the depth and the characteristics of the rock formations to be penetrated. The considerable additional costs and increased risks of directional drilling must also be factored into the decision whether to utilize this technology.
Additional time to drill and complete well construction and increases in long-term maintenance activity sometimes necessary in a directionally drilled well, are surface impacts seriously considered before using this technology. Directional drilling can significantly increase well construction time, which includes drilling -- turning a week's activity into a month or more. Increased long-term maintenance may result in frequent and repeated use of construction equipment, such as rigs, and associated noise at a directionally drilled well site. Further, it may be necessary to use additional equipment to draw gas out of a directionally drilled well, such as a pump jack. Thus, while directional drilling might appear to be less intrusive, in some cases the opposite will be true.
Special Accommodations for Agriculture
When a well is located on crop or ranch land, operators work closely with landowners to lessen the interference with agricultural activity. Circumstances permitting, a wellhead and other production equipment may be located close to a property line or in a corner of a field where irrigation equipment does not come into contact with production equipment.
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Spacing
In today's natural gas industry the first step in the life cycle of a well begins with government regulations. Each formation currently accessible to natural gas extraction is spaced by the Colorado Oil and Gas Conservation Commission. This means that the COGCC has determined how many wells per section will adequately drain the resource (A section consists of 640 acres). The Fruitland formation in La Plata County is generally spaced at one well per 160 acres. The Pictured Cliffs, Mesa Verde and Dakota formations in La Plata County are spaced at one well per 160 acres. In the Red Mesa area of the county, oil wells in the Dakota formation are spaced at approximately one well per 40 acres. For more information about specific spacing and formations in a certain location, contact the COGCC.
The diagram above shows how a 640-acre section is divided for 160-acre spacing. To assure correlative rights, an operator must produce gas from the "drilling window" thousands of feet below the surface. At the surface, the drilling window is a starting point from which operators seek to locate a well site. In many cases, wells drilled outside of the drilling window with permission from mineral owners and the COGCC.
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The potential producer must acquire the right to develop the natural gas reserve. Typically a natural gas operating company (operator) acquires a lease for mineral rights by entering into a contractual agreement with the mineral owner. The mineral owner receives royalties from any production that may result.
In some cases, a small-percentage mineral owner may object to granting a lease, thereby stopping natural gas development in a spaced area. The COGCC has rules that enable development to move forward though a process known as "forced pooling." A forced-pooled mineral owner also receives royalties.
Surface Owner Agreements
The next step is geologic and seismic studies to locate the best possible underground source of natural gas, either in sandstone or coal formations. After the studies are completed companies typically select an optimal site. Then well location and right-of-way easements for road access are negotiated with the surface owners. During this phase companies work closely with surface owners to locate the well site within the regulated spacing "window." A window determines the underground area within a spaced unit where a well may be drilled and is specified by the COGCC. Sometimes a gas well can be located outside the window when special circumstances arise such as above ground geography or a special landowner request -- typically agriculture-related. Negotiations for pipeline easements are typically negotiated after a successful well has been completed.
The COGCC requires operators to ask for a consultation with the surface owner about the locations of well sites and access roads, and about final reclamation. Operators typically negotiate a surface agreement regarding the "reasonable use" of the surface during drilling, production and reclamation of the well site. In practice, companies generally pay surface owners for limited land use despite the fact that the law permits reasonable access and use without compensation. If a surface agreement cannot be successfully negotiated, COGCC rules allow companies to post a surface bond with the state. A bond is intended to protect surface owners from "unreasonable crop losses or land damage from the use of the premises" -- not for perceived economic loss associated with mineral owner access. The vast majority of wells in La Plata County are located by surface agreements with landowners.
Permitting
Permitting is the next step in the process. State permits are required for wells in La Plata County. Wells may also require county or federal and/or tribal permits. During the permit process, environmental, archaeological and surface use issues are addressed. Operators must adhere to hundreds of regulations and meet a wide range of standards and requirements before the drilling begins. Rules require companies to plan for the entire life of the well, unexpected events, safety, environmental protection, weed control and final reclamation when the production cycle is completed. Only when all requirements are met and permits granted can drilling begin.
Drilling and Casing
Drilling a gas well is a highly orchestrated event usually done by drilling contractors. Drilling contractors are rigorously trained to work efficiently and safely. Drilling rigs and crews are expensive and brought on the site for immediate action. Because of the safety, technical concerns and expense, drilling rigs operate 24-hours a day until the drilling is completed. For example, if drilling is stopped, the drilled hole can cave in and potentially cause multiple safety and environmental problems. Once drilling is completed, the rig and crew move to another location.
Anywhere from one to three acres are needed for the drilling pad. The well pad is prepared for a variety of heavy equipment needed during the drilling operation. After drilling is completed, the well pad is reduced to between 1/2 and 1-1/2 acres.
The drilling process requires the power of multiple diesel engines. This process is noisy but is over relatively quickly. Actual drilling time can be anywhere from 3 to 10 days -- more for directionally drilled or deeper zone wells. State noise regulations allow for short-term construction noise within prescribed safety limits. Sound diminishes with distance but precautions are taken for workers in close proximity to sound sources. Nearby residents are notified in advance of drilling activity.
Typically well drilling as casing goes like this -- a 12-1/4" hole is drilled to a minimum of 200 feet and to a maximum depth 50 feet below the deepest registered domestic water well in the area. Surface casing is put into this hole. Surface casing is 1/2" thick steel pipe with an outside diameter of 8-5/8". Cement is poured between the hole and the steel casing and is approximately 2" thick all the way up to the surface. Cement is allowed to dry, then the 7-7/8" production hole is drilled 200 feet below the target formation also known as the completion zone. Production casing is then put into the hole. Production casing is 3/8" steel pipe with an outside diameter of 5-1/2". Again cement is poured between the hole the steel casing measuring about 1" thick all the way up to the surface.
Cement seals off formations to prevent fluids from migrating. For example, cement protects freshwater in one formation from methane gas in another. Cement also protects the steel casing from the corrosive effects of other formation fluids. Casings are checked for integrity before the well construction process continues. In some deeper natural gas wells, intermediate casing is needed because some formations are encountered that contain abnormal pressures and/or conditions.
In the completion zone, the production casing is perforated so that natural gas can flow into the production tubing. Production tubing is set in place after the completion process and is 1/4" steel tubing with an outside diameter of 2-7/8" running from the bottom of the hole to the surface. At the bottom of the hole 40 feet of cement is poured with a plastic plug on top to complete the sealed well bore.
In comparison, domestic water wells are required to be cased with only 0.188" steel pipe, or 0.2" plastic pipe, or 3" cement, with a minimum 4-1/2" outside diameter.
Gas wells are separated from the surrounding surface formations by 4.125" of steel pipe and cement that make up a well's casing. Casing is designed, among other things, to isolate gas wells from any nearby domestic water wells. This diagram is not to scale and has been dramatically shortened.
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Completion
Completion not only refers to the target formation, "the completion zone," but is also a term used to describe well construction activity after the drilling and casing is finished. To complete a well, the permeability of the completion zone must be enhanced so that gas can flow out of the sandstone or coalbed in which it is trapped. The two techniques used to enhance permeability are cavitation, and hydraulic fracture stimulation (commonly referred to as "fracing" -- pronounced frak-ing).
Cavitation requires a larger hole, surface casing and production casing. After casing is completed, the hole is sealed with a valve and air is pumped into the well. The valve is opened, creating a vacuum that breaks up the underground formation around the base of the well so that gas can flow through the resulting cracks and holes. Cavitation creates a jet engine-like noise that lasts anywhere from a few minutes to 15 minutes and is done several times before the well is completed. Bits of rock or coal mixed with water often spew out of the wellhead. Cavitation is a similar phenomenon to opening a shaken pop bottle, only on a much larger scale. Environmental and safety precautions are required during the process.
Fracing is done by pumping a mixture of sand and water down to the base of the well and back out again. The gritty water permeates the underground formation enabling the gas to flow from the cracks and holes created. Fracing is generally done once but may be repeated several times before gas flows are sufficient. Fracing utilizes the power of multiple diesel engines and can take from 30 minutes to several hours.
Reclamation
After a well is drilled, all areas which were disturbed by the drilling operations, and which are not needed for production operations, are to be reclaimed as close to their original condition as possible. This "interim reclamation" is required to take place:
On Crop Land: No later than three months after a well is completed.
On Non-Crop Land: No later than twelve months after a well is completed.
Operators must remove drilling waste materials, fill pits and holes, and remove compaction from the soil in areas no longer needed by cross-ripping the soil to a depth of eighteen inches. Then they must close drilling pits by drying out the pit and backfilling it, replacing the soil layers in their original positions.
There are also interim restoration and revegetation requirements for landscape contouring, soil tilling, reseeding, weed and erosion prevention. Sometimes interim restoration and revegetation is negotiated in the surface agreement with the landowner.
Production
After completion, pipeline construction connects the well to the natural gas transportation system. Natural gas is transported through a system of pipelines to a processing plant. It goes through a series of separation and purification procedures to make it ready for consumer use. Natural gas is processed at plants here in La Plata County (see Processing section for more information). Processing plants are heavily regulated so that environmental and safety precautions are met. During processing, a chemical smell is added to natural gas so that it can be detected if leaks occur in consumer homes. The processed natural gas from La Plata County travels through other pipelines to commercial markets around the United States.
Along with natural gas, water also is produced from a well. Water is separated from the gas at the well site. Water is transported off the well site in one of two ways, by pipeline or by truck. A pipeline system transports the produced water to an injection well. Injection wells are drilled into deep formations, often below 10,000 feet. The EPA has regulations for injection wells, which are overseen by the COGCC. These regulations are specifically designed to prevent contamination of underground sources of drinking water.
Sometimes water is pumped into holding tanks later the water is trucked to a disposal facility. Although most water is disposed of by injection in La Plata County, some is allowed to evaporate in regulated pits, permitted and checked by the COGCC.
Compression
Natural gas is transported in pipelines. The amount of gas that can be transported in a pipeline depends upon how much the gas is compressed. The more the gas is compressed, the greater the volume of gas that can be transported through the pipeline. Uncompressed gas is displaced by compressed gas, essentially stopping the flow of uncompressed gas to the processing plant.
Gas compression can either take place right at the well site as it enters the pipelines system or it can be transported by pipeline to a compression facility, where it is compressed and then transported to a processing plant. On-site compression is done with small electric or gas-powered compressors. A compression facility contains large electric or gas-powered compressors and is surrounded by a sound absorbing structure. The type of compression used by companies depends upon economic factors and gas well location concerns -- if a well is too remote, it is more difficult to tie the well into a compression facility. Some companies try to cluster well sites so that a centrally located compression facility can serve the needs of many wells, thus reducing the noise associated with gas compression.
Workover
During the life of a well, it may need additional work to improve performance; this is called a workover. Recavitation or refracing along with other workover activities will result in temporary rig activity on the well pad.
Recompletion
Recompletion is a way of reusing an existing well to gather more natural gas from either the same formation or different formations. Recompletion means changing or adding completion zones (target formations) through one of the following ways: 1) Recompletion to the same zone but to the side of the original hole, 2) Recompletion to a different zone or 3) Recompletion to multiple zones from one well. The COGCC carefully regulates and permits recompletions as new well permits. Recompletions require rig activity that lasts for several days.
Temporary Shut-in
Sometimes the price of natural gas is so low that the cost to produce and process it is higher than the production revenue and creates an economic situation where a well is temporarily shut-in. The well may later be put back into production. This temporary shut-in is regulated by the COGCC for safety and reporting purposes.
Plugging and Abandonment
After all the recoverable natural gas has been drained at a well site the well is plugged and abandoned. The COGCC has rules that specify how the well is plugged, soil reclaimed and other environmental and safety protections completed to avoid future problems. Final reclamation takes place after gas wells are plugged and abandoned. All final reclamation work is required to be completed within six months after plugging a well. An operator is required to:
- remove all production equipment and debris;
- remove or treat any remaining production waste or contamination from spills or releases following COGCC rules;
- backfill all production pits by replacing the soils in their original positions;
- correct subsidence over closed production pit locations by adding additional topsoil;
- close access roads to plugged and abandoned wells and associated facilities;
- re-grade and re-contour the well site and access roads;
- perform compaction removal, restoration, and revegetation on well sites and access roads to the same standards as those for interim reclamation on both Crop Land and Non-Crop Land.
- comply with all COGCC rules unless a surface owner waiver or Commission variance is obtained.
Because La Plata County has had natural gas production since the early part of the century, some gas wells were plugged and abandoned prior to the COGCC's rules. The state has a special fund supported by natural gas severance taxes for the plugging and abandonment of "orphaned" wells in the state. An orphaned well is a well for which an owner or operator cannot be found or is unwilling or unable to plug and abandon the well. Most often, required bond and fund money is used to plug an orphaned well.
Natural Gas Processing
La Plata County is home to a number of natural gas processing plants. At these plants, raw gas is processed to remove undesirable components such as water and separated into distinct gas products such as methane, ethane, butane, propane and others. In fact, one of the plants in La Plata County supplies the majority of propane used in a 150-mile radius.
Natural gas processing may be as simple as drying the gas by passing it through a fixed bed of an absorbent material, or it may be as complex as liquefaction of gas by cooling to extremely low temperatures. Processing plants in the county use a variety of sophisticated processes to treat natural gas. Safety and environmental protection are top priorities at local processing plants. Safety training, regular safety meetings, emergency drills, coordination with local fire departments and emergency personnel are all part of normal operations. Plants must also meet strict federal safety and environmental standards and comply with state and local regulations.
Safety is a top priority to the companies and individuals working in the natural gas industry. The industry's safety record in La Plata County is outstanding. Over the past five years there has been less than one accident per year per company, while there have been tens of thousands of safe workdays at various companies with operations in La Plata County. The overwhelming majority of accidents are the typical work accidents experienced by any company.
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