For this blog entry I continue to quote from a White Paper prepared by Baker Hughes and available on our website. The complete paper can be obtained here. I will present it here in three parts.
Since the late 1940s, hydraulic fracturing technology has been used in more than a million U.S. wells to safely unlock useful oil and gas reserves that would otherwise remain trapped deep within the earth. The principles of the process have not changed since the early days, but modern hydraulic fracturing relies on vastly improved technology to ensure its continued contribution to a safe, environmentally responsible energy future.
As the world looks forward to a distant but desirable future with safe, renewable energy, the fact remains that today’s energy demands can only be met with fossil fuels. Oil remains the largest primary energy source, with coal in second place, and natural gas in third— but gaining momentum.
The global interest in natural gas stems from its wide distribution around the world and its simple chemical structure, which makes it burn cleaner than oil or coal, therefore producing fewer harmful emissions. As the cleanest-burning fossil fuel, natural gas is an attractive transition fuel, and its availability in more than 85 countries makes it an ideal fuel for energy independence.
Although oil and gas are both described as being found in underground reservoirs, these reservoirs do not resemble surface drinking water reservoirs but rather are solid rock— imagine an extremely hard, dense sponge. Even with thousands of feet of rock applying pressure on these reservoirs, it is difficult, if not impossible, to capture significant amounts of oil or gas in one wellbore without breaking open or fracturing the rock.
Hydraulic fracturing is the practice of pumping fluid into the earth at high enough pressures and rates to crack hydrocarbon-bearing rock, extend the cracks, and leave behind some propping agent (proppant) so the cracks stay open when the pumping stops. These cracks, generally reaching a few feet to a few hundred feet from the wellbore, provide a conductive pathway that guides the fracturing fluid and then the oil and gas to the wellbore so they can be produced to the surface.
Optimized modern hydraulic fracturing is a safe and effective way to maximize the efficiency of the oil and gas production process. Optimized fracturing minimizes the number of wells (and their associated surface impact) required to recover the energy that supports a modern lifestyle.
Ultimately, oil and gas development is a partnership of land owners, regulators, operators, and integrated service company experts working together to minimize risks, ensure environmental stewardship, and efficiently recover energy resources.
Risk management starts with comprehensive reservoir analysis and feasibility studies, combining geological features, rock properties, offset well experiences, regulatory guidelines, and economic drivers to support a team of expert engineers designing:
One of the main barriers to fracture fluid migration is the presence of a non-permeable caprock formation that can trap oil, gas, or water below it. In many cases, this layer of rock is responsible for the creation of the reservoir, having already prevented fluids from moving into other geological strata. Its impermeability also minimizes the risk that fracturing fluid or hydrocarbons will migrate out of the targeted reservoir and into groundwater.
The second geological barrier is geophysics, which guides where a fracture is most likely to propagate, and how far it is likely to extend. Stimulation engineers use data from the reservoir studies with sophisticated computer modeling, such as Baker Hughes’ MFracTM and MShaleTM software, to reduce fracturing risks. As with any modeling software, the results are only as good as the input data and assumptions, making user expertise with real-world hydraulic fracturing as well as the particular modeling software a critical metric for any fracture design proposal.
The length of a typical fracture points to the most significant geological barrier to fluid migration: the thousands of feet of rock layers (geological strata) between most hydrocarbon reservoirs and the deepest surface waters. Economics and geophysics typically limit fractures to a few hundred feet from the wellbore, with an unusually large fracture extending perhaps 1,000 feet.
Most oil and gas reservoirs are at least several thousand feet below the surface, and the deepest drinking water sources are usually less than 1,000 feet. Coalbed methane gas wells tend to be closer to drinking water sources than are other types of oil and gas wells. Nevertheless, the U.S. Environmental Protection Agency (EPA) concluded in 2004 after a five-year study that there was little to no risk of fracturing fluid contaminating underground sources of drinking water during hydraulic fracturing of coalbed methane production wells.
Fractures typically extend just a few hundred feet from the wellbore. With thousands of feet of rock between the targeted strata and any drinking water zones, it’s extremely unlikely that hydraulic fracturing would breach an underground drinking water sources.