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Wellhead

Cement Soil Conductor Pipe • Set across surface Aquifer soils and shallow rocks.

Cement

Surface Casing • Cemented at appropriate depth to protect shallow fresh water aquifers. Hydraulic

Production Casing • Drilling fluid stays fracturing: inside this pipe. your

T h o u sa n d s o f F e e t / h u n d r e d s o f m e t e r s questions answered r s

In formations where natural gas is trapped very tightly in tiny pores (rather than accumulated in large pools

C K L A Y E or more porous rock), if we simply drill through the rock the gas won’t flow easily, r o making it impossible to extract enough gas to make the well economical.

After we drill a tight gas

T a r g e t F o r m ati o n well, to complete it we stim­ ulate the gas flow from the formation using a technique called hydraulic fracturing. STAGE | STAGE | STAGE This often-misunderstood technique has raised some Note: This image illustrates hydraulic fracturing used with horizontal drilling. In some formations, the well remains vertical within the tight gas formation and the fractures extend horizontally from the wellbore. For each well, casing questions that we would and cementing designs are approved by applicable regulatory agencies. Illustration is not to scale. like to answer. Hydraulic fracturing is a valuable technique for stimulating production from tight gas and shale gas wells.

combined with the low permeability of the tight gas formations themselves, keep the natural gas and other hydro- carbons contained within the target for- mation, and also help prevent migration of any hydraulic fracturing fluids that may be pumped into such formations.

Are the chemicals used in hydraulic fracturing Q dangerous?

Most of the fluid used in A hydraulic fracturing is water. We add chemicals, typically around What is hydraulic the stages in the well, we drill out the 1 percent of fracturing fluids, to keep Q fracturing? plugs, which allows the gas to flow the pipes cool by reducing friction up through the well to begin produc- and to prevent scale build-up and Hydraulic fracturing is a proven tion. The fracturing fluid is typically bacterial growth. Many of these addi- A technique that has been used 99 percent or more water and sand, tives are compounds that are used in for decades in many kinds of oil and with the remainder made up of chemi- other applications you encounter in gas wells, but is particularly valuable in cals. The sand helps to keep the cracks your daily life, from citric acid and tight gas and shale gas formations. A open, and the chemical additives help guar gum, commonly used as food tool called a perforating gun is low- reduce friction and prevent bacteria additives, to ethylene glycol, commonly ered into a newly drilled well and lined growth and scale from forming and used in household cleansers and auto- up precisely within the formation using blocking the flow of gas. motive antifreeze. Some of the chemical tools such as seismic images, well logs, additives can be hazardous if not han- global positioning systems and other dled carefully. We take great care indicators to target the spots from which Can the fractures allow when using all the compounds added tight gas appears most likely to flow. Q natural gas to seep up to fracturing fluid, and meet or exceed When fired, the gun punches small into the water table? all regulatory requirements related to holes in the well casing, cement and handling hazardous materials. rock. Next, fracturing fluid is pushed typically, North American gas out through the perforations under high A formations that require fracturing The formulas for fracturing fluids vary, pressure, creating small cracks in the are located a mile (1.6 kilometers) or partly depending on the composition formation that allow the natural gas more below the water table, trapped of the gas field and partly on the to flow from the rock. We fracture the below many layers of impermeable expert opinion of the operator or fluid well in stages and set a plug between rock. These thousands of feet of rock supplier as to what works best. These each stage. After we fracture all of overlying the tight gas formations, formulas are owned by the supplier Drilling, casing and cementing procedures are designed to isolate the well from the potable groundwater zone.

the rock or shale zone containing formation, which helps to make produc- the gas, which has very low porosity tion as efficient as possible and protects and is typically trapped far below the the environment. deepest source of potable water and underneath many layers of imperme- able rock. Consequently, the fracturing Can the chemicals stored fluid should either stay within the tar- Q on the site affect groundwater? get formation or be forced back out through the well, but in either case safe handling of all water it should remain isolated from ground- A and fluids on site, including water supplies. chemicals used for hydraulic fracturing, is a high priority for Shell. We comply with all regulations regarding contain- Can fracturing fluid ment, transport and the handling of Q get into the water supply? any spills, should one occur. To pro- tect groundwater, we keep chemical and some are considered proprietary. we design and test the integrity containers and all fluid handling equip- Shell is transparent about our opera- A of our wells to meet strict spec­ ment located on site within secondary tional methods and the products used ifications based on the local environ- containment barriers that could capture in our hydraulic fracturing operations. ment. The upper portions of the well, a spill in the unlikely event that one This includes releasing information where the wellbore passes through the were to occur. The containers must about the chemicals we use in our water table, are extensively reinforced pass regular integrity checks and hydraulic fracturing operations to to help prevent either gas or fluids from certification. We check water storage the extent we are permitted by our escaping into the surrounding ground. tanks for integrity before we use them suppliers to release their proprietary Wells are made of steel pipes and and check them visually each day. information. We support regulatory sealed in place with cement from the Single-use containers that are used efforts that require our suppliers to surface to below the level of drinking to transport small volumes of chemi- release such information. water supplies, typically to a depth cals are returned and disposed of of 1,000 feet (about 300 meters) or offsite. Any spill that were to occur more. These barriers help to contain on a well pad would be promptly Can fracturing fluid seep the fracturing fluid and, along with the cleaned up, reported and docu- Q from the gas formation into depth at which fracturing takes place, mented according to both our the groundwater supply? prevent the fluid from mingling with own and regulatory requirements. drinking water close to the surface. shell’s drilling, casing, and A cementing procedures, which During and after hydraulic fracturing, What happens to the fracturing meet or exceed regulatory require- wells are monitored with pressure Q fluid after it is used? ments, are designed to protect ground- sensors to check that they are firmly water by isolating the well from any sealed. Shell also periodically moni- we take multiple steps to groundwater supplies. We pump the tors the fractures and the fluids using A properly handle hydraulic fracturing fluid through the well into micro-seismic technology to map the fracturing fluid. First, when possible, doing things right

we reuse it for additional wells in test injection wells for integrity and a single field.T his both reduces our compliance. We isolate the wells “We have a fundamental overall use of fresh water and reduces in three ways: belief that we have more the amount of recovered water and success if we work with • We choose zones that have multiple chemicals that must be disposed of. people in ways that are confining layers above the zone to Second, we keep the recovered water inclusive and try to find keep the injected fluids within the in storage tanks or lined storage pits the solution that works target formation. until it is disposed of in a permitted salt- best for everyone.” • water disposal well or other approved We use multiple layers of well casing – Jeff Wahleithner, disposal site. All disposal facilities used and cement (similar to our production Vice President, Drilling – by Shell undergo extensive onsite envi- wells) and periodically run mechanical Shell Upstream Americas ronmental assessments to determine if integrity tests to verify that the casing they meet regulatory standards and and cement are holding the liquids. Shell specifications prior to use. • We control how much fluid we inject and at what pressure (specified in how do the disposal each well permit) to help keep the wells hold the fluids? Q fluids in the target zone, and we mon- itor the pressure in the injection well all of our Shell-operated and the spaces between the casing injection wells are designed A layers (also called the annuluses) to to meet regulations to protect ground- check and verify the integrity of the water. Our geologists and engineers injection well. work together to design, drill and We also screen any non-Shell-operated injection wells that we use to verify that they comply with all regulatory requirements.