Geothermal Aquifer Architecture Model of Alblasserdam Member in Drechtsteden, the Netherlands

Abstract

The decrease in the production of hydrocarbons in combination with a growing urgency to reduce carbon emissions drives a rapid study and application of geothermal energy in the Netherlands. The produced heat from the low enthalpy geothermal energy can be used for heating up the buildings and greenhouses. A doublet system is used in the geothermal scheme, which consists of one production well and one injection well. The reinjection is done to maintain the reservoir pressure and reduce pressure decline due to production, earthquake and subsidence prevention, and environmental safety. Thus, it is crucial to model the aquifer distributions appropriately as the injection and production well should be placed at the communicated sand bodies.
In this study, the architecture of the Alblasserdam Member in the Drechtsteden, West Netherlands Basin is modelled. An investigation of the paleo flow and the distribution of sand prone succession within the Alblasserdam Member is done by integrating seismic interpretation, reservoir sedimentology, and petrophysical evaluation. The data used consist of seismic data, well log dataset and core data from the acquired hydrocarbon exploration data. The Alblasserdam Member was deposited during the Late Jurassic to Early Cretaceous when the high tectonic activities occurred in the West Netherlands Basin and followed by series of inversion impulses made this member bounded by various members at the bottom and the top. The seismic response of the Alblasserdam Member shows a high thickness and depth variations. The sediments of the Alblasserdam Member are highly accumulated in the central part of the study area, bounded by two major faults striking SE-NW.
Several sections of well correlation are made based on cycles of changing accommodation to sediment supply ratio (A/S cycles). The correlation is supported with seismic interpretation, allow to map the distribution of sand-rich interval of the Alblasserdam Member in the Drechtsteden. Two potential aquifer intervals are found. A southwestward shifting of the main fluvial system is observed from the thickness trend of the shallower aquifer intervals. A petrophysical evaluation is made to analyze the properties of the potential aquifer that encompass net to gross thickness (N/G), average porosity, and average permeability. The deeper potential aquifer has a higher clean sand N/G, but lower average permeability, that might be caused by the compaction, and mineral precipitation after the inversion period, especially in the highly inverted area. In the end, a recommendation to place a pair of production and injection wells are proposed based on the high accumulation of sand-rich intervals, sufficient depth to produce heat >70oC and absences of the fault. The wells are placed toward SE-NW trend which is parallel to the distribution of the main fluvial distribution and the orientation of the faults, with production well placed at the deeper level.