Reinjection Model Studies in Fractured and Homogeneous Geothermal Systems
Conference
·
OSTI ID:887094
Reinjection of geothermal waste waters has become an important topic of interest for industry as well as for research. The environmental concerns due to chemical composition of geothermal waste waters had urged the industry to dispose it underground. In several field applications no interference due to thermal front breakthrough was observed on the other hand some cases are reported where reinjection had caused severe declines in energy production due to unexpected breakthrough of injected water. Several analytical and numerical studies are available where the effect of fractures on the movement of thermal front are discussed. It was shown that when the conduction heat transfer from matrix to fracture dominates, retardation of the thermal front movement will be observed. Bodvarsson and Pruess considered the above problem in a five-spot well pattern. They observed as the amount of fluid injected reaches the amount produced, the long-term energy output of the system increases. Pruess in his study compares the behavior of porous medium and fractured medium in terms of pressure decline due to production. Temperature and pressure profiles are presented between an injector and a producer where heating of the injected water in porous medium and in fractured medium with small fracture spacing was high compared to a larger fracture spacing. Such observations from the numerical studies were checked against some limited field examples. However understanding of the injection effects in fractured reservoirs is limited. This work presents the results of laboratory experiments where effects of reinjection on temperature and pressure behavior of a porous medium and a fractured medium were investigated. The porous medium was a crushed limestone pack, with 10 mm average particle size, packed in a 3-D box model where injection and production ports are located on the diagonal ends simulating a five-spot pattern. The fractured medium was made from uniformly cut marble blocks packed in such a way to permit uniform fracture geometry. The pressure and temperature response of both models are analyzed as a function of (1) depth of injection and production; and (2) injection rate where 20 C injection water is injected into 110 C reservoir.
- Research Organization:
- Middle East Technology University, Ankara, Turkey
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AS03-80SF11459; AS07-84ID12529
- OSTI ID:
- 887094
- Report Number(s):
- SGP-TR-93-13
- Country of Publication:
- United States
- Language:
- English
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