Geothermal fluids disposal

Significant amounts of waste heat arise from geothermal energy utilization the amounts vary with the utilization type. The possibilities of waste heat disposal are often limited by technical or legislative barriers. For technical reasons, re-injection of used geothermal fluids into the subsurface often remains incomplete. Regulations, on the other hand, can restrict discharges of waste fluid and heat to (or dissipation) in the environment. A beneficial way of waste heat treatment is the use of the heat for purposes that can even result in economic profits. Several such options have been described above but many more possibilities are technically feasible and economically viable. 

Re-injection into the subsurface is the most often used technique to dispose of geothermal waste heat. The cooled-down fluids, after having fulfilled their tasks in the power generation cycle (or in the direct-use application), can be reinjected into the same geothermal reservoir from which the hot fluid has been produced. The fluid re-injection can help to sustain reservoir pressure, which otherwise would decrease during production. For the re-injection, however, additional wells must be drilled and - if required by the rock permeability at depth - the fluid must... 

Stress induced permeability change is of crucial importance in various kinds of applications such as nuclear waste disposal in deep geological formations, geothermal energy utilization and underground excavations. In particular, coupling between the stress and permeability is a key element in understanding the nature of flow in the fractured rock (Rutqvist and Stephansson, 2003). This is because fractures, which are the main pathways of fluid flow in fractured hard rocks, are heavily dependent on the stress conditions for their deformations. 

In 1980, Congress enacted the Solid Waste Disposal Act Amendments (Public Law 96-482), which amended the RCRA in several ways. Pertinent to special wastes was the addition of Sections 3001(b)(2)(A) and 3001(b)(3) (A). These new sections—frequenfly referred to as the Bensten and Bevill Amendments—exempted "special wastes" from regulation under Subtitle C of RCRA until further study and assessment of risk could be performed. Specifically, the Bentsen Amendment (Section 3001(b)(2)(A)) exempted drilling fluids, produced wafers, and other wastes associated with the exploration, development, and production of crude oil or natural gas or geothermal energy. The Bevill Amendment (Section 3001(b)(3)(A)(i-iii)) exempted the special wastes listed above. 

Drilling fluids and cuttings from offshore operations disposed of onshore Geothermal production fluids... 

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