Thermal effects of reinjection in geothermal reservoirs with major vertical fractures
Possibilities for characterizing the thermal properties of fast paths by means of different types of tests (tracers, pressure transients, non-isothermal injection) are discussed. Thermal breakthrough in vertical fractures is examined in some detail, using an idealized model for which an analytical solution is available. The model shows that rapid tracer returns are not necessarily indicative of rapid thermal interference. Thermal breakthrough predictions can be made from tracer data only, if both fluid residence time and tracer dispersion are taken into account. However, due to the geometric simplifications necessary in analyzing the tracer data, thermal interference estimates on this basis appear questionable. Pressure transient tests can provide additional parameters for thermal interference predictions, but they cannot resolve the problem of non-uniqueness. A more reliable determination of thermal characteristics of fast paths appears possible from non-isothermal injection tests, combined with numerical simulation. A mixed numerical/semi-analytical approach is employed to model the three-dimensional fluid and heat flow in injection-production systems in vertical fractures, with heat transfer to and from the adjacent rock matrix. Illustrative calculations of thermal recovery after different injection periods suggest that shutting-in an injection well can prevent unacceptable temperature declines at production wells.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5566419
- Report Number(s):
- LBL-16269; CONF-8310121-7; ON: DE84004347
- Resource Relation:
- Conference: SPE annual technical conference, San Francisco, CA, USA, 5 Oct 1983
- Country of Publication:
- United States
- Language:
- English
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