Abstract
Required distance between doublet systems in low enthalpy geothermal heat exploitation is often not fully elucidated. The required distance aims to prevent negative interference influencing the utilisation efficiency of doublet systems. Currently production licence areas are often issued based on the expected extent of the reinjected cold water plume on the moment of thermal breakthrough. The production temperature, however, may not immediately drop to non-economic values after this moment. Consequently, heat production could continue increasing the extent of the cold water plume. Furthermore, the area influenced by pressure because of injection and production spreads beyond the cold water plume extent, influencing not only the productivity of adjacent doublet systems but also the shape of cold water plumes. This affects doublet life time, especially if adjacent doublets have different production rates. In this modelling based study a multi parameter analysis is carried out to derive dimensionless relations between basic doublet design parameters and required doublet distance. These parameters include the spacing between injector and producer of the same doublet, different production rates, aquifer thickness and minimal required production temperature. The results of this study can be used to minimize negative interference or optimise positive interference aiming at improving geothermal doublet deployment efficiency.
Highlights
Low enthalpy Hot Sedimentary Aquifers (HSA) are often exploited by multiple individual geothermal operators with a single or a few doublet systems
If the life time is 61 years, the cold water plume extends beyond these boundaries (Fig. 4-B2)
The results of this study indicate that interference in HSA exploitation is only significant in terms of life time (Fig. 9)
Summary
Low enthalpy Hot Sedimentary Aquifers (HSA) are often exploited by multiple individual geothermal operators with a single or a few doublet systems. Examples of this type of geothermal exploitation can be found in the West Netherlands Basin (WNB) and the Paris basin (e.g., [9,23]). In the WNB a geothermal production licence typically has an area which is equal to a rectangle with a size of L Â 2 L, in which L is the injector to producer well spacing The current WNB licencing strategy may underestimate the required doublet distance which could eventually lead to an inefficient recovery and a negative interference
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