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Hydraulic Fracturing from the Groundwater Perspective
Published in M. Thangarajan, Vijay P. Singh, Groundwater Assessment, Modeling, and Management, 2016
Ruth M. Tinnacher, Dipankar Dwivedi, James E. Houseworth, Matthew T. Reagan, William T. Stringfellow, Charuleka Varadharajan, Jens T. Birkholzer
Well stimulation and associated activities may result in the release of contaminants into the environment, including surface and groundwater resources. Releases can occur during chemical transport, storage, mixing, well stimulation, well operation and production, and wastewater storage, treatment, and disposal (Figure 7.5). A physical connection or "transport pathway," either natural or induced, between the release location and the impacted surface or groundwater body is required for releases to occur, along with a driving force (e.g., pressure difference, buoyancy) for contaminant migration. The probability of contaminant migration is regulated by a number of factors, including reservoir depth, the physical and hydrological properties of the formation, reservoir production strategies, drilling and casing practices, plus the unique geologies of each oil and gas-producing region.
Preliminary assessment of water-supply availability with regard to potential shale-gas development in the Karoo region of South Africa
Published in Jude Cobbing, Shafick Adams, Ingrid Dennis, Kornelius Riemann, Assessing and Managing Groundwater in Different Environments, 2013
Shale may also contain gas, but has a poor ability to transmit fluids. As a result, gas cannot readily migrate in shale formations. Fracking is a well-stimulation technique aimed at opening existing cracks or creating new ones to more effectively and efficiently extract gas from low-permeability (or tight) shale formations. It entails drilling vertical wells until the target horizon is encountered, whereafter horizontal wells are drilled (Figure 18.1). Using water, sand and chemicals, sections of the horizontal well are systematically subjected to very high pressures (as high as 70 000 kPa, or 700 bar) to open existing fractures or create new ones. Fractures are generally less than 1 mm wide and the sand is used as a proppant to keep the fractures open. Typically the section of well fracked at any one time is between 100 m and 150 m in length, while the induced fracture zone extends between 200 m and 300 m from the horizontal well. The drilling of a single well takes about 1 month to complete and the fracking of the well 14 d in total.
Productivity optimization of the oil wells using matrix acidizing- Haoud Berkaoui field case study
Published in Petroleum Science and Technology, 2023
Madjid Yarou, Messaoud Hacini, Hamid Lebtahi, Mohammed Khodja
Recently, well stimulation techniques become one of the most important focuses to increase profit and reduce cost in oil and gas wells. Oil production can be enhanced by using chemical reagents to eliminate scales and asphaltene (Azizollah 2018, 2021a, 2021b). It is also realized by waterflooding which is often a suitable method to ameliorate oil recovery (Norman 2011). Matrix acidizing is a developed stimulation technique used to improve it by removing or minimizing formation damage and changing the petrophysical properties of the reservoir rock which are the porosity and the permeability near the vicinity of the wellbore (Crowe et al. 1992). This damage is the result of the natural depletion and major during pre-operations and productions such as drilling, completion, water/gas injection, and improved oil recovery (IOR). The treatment involves pumping acids below the formation fracturing pressure and it is applied in both sandstone and carbonate formations (Shafiq et al. 2014). The acid system differs but the same practice is done. In carbonate reservoirs, the acid job design is based on the use of hydrochloric acid (HCl) to dissolve carbonate minerals and create wormholes that allow fluids (oil, gas, and water) to flow more freely into the well (Mohammed 2002). In sandstone reservoirs, mud acid is more common, which is a mixture of hydrochloric acid and hydrofluoric acid (HCl/HF), used to dissolve sand (quartz), feldspar, carbonate minerals, and clay particles and achieve permeability increase by less or more radial penetration of acid deeply into the formation (Leong and Hisham 2019).
A structured hazard identification method of human error for shale gas fracturing operation
Published in Human and Ecological Risk Assessment: An International Journal, 2019
Jinqiu Hu, Laibin Zhang, Qianlin Wang, Bin Tian
Hydraulic fracturing, commonly known as fracking, is a well stimulation technique in which a shale rock formation is fractured by hydraulically pressurized water jet, which is mixed with abrasives and chemicals (Tiwari 2015). Hu et al. (2018) listed the detailed process of shale gas fracturing, including three main stages—pre-fracture, fracturing, and post-fracture—which could be further classified into 29 sub-stages. For example, there are 4 sub-stages in the stage of pre-fracture, such as road preparation, well-site preparation, feed-flow preparation, and material preparation. Therefore, it is a complex system of continuous operation.