Estimating permeability in a limestone geothermal reservoir from NMR laboratory experiments

Characterizing Facies and Porosity-Permeability Heterogeneity in a Geothermal Carbonate Reservoir with the Use of Nmr-Wireline Logging Data

“…In our study, only microporosity and macroporosity volumes are considered with a cut-off threshold between both porosities set at 120 ms. This value has been previously determined from NMR laboratory experiments conducted on core samples from well GBD4 (Catinat et al, 2023). Summing up, the longer the magnetization decay times, the larger the pores and vice versa.…”

“…Here, this relation will be referred to as the SDR (namely KSDR) default relationship. Another equation, named k m , adapted to Middle Jurassic limestones has been found in previous work (Catinat et al, 2023) to improve permeability estimates within the reservoir and will be used later in this paper (see Section 5.1). For more detailed descriptions of NMR physics and its applications, readers are referred to other papers in literature (Dennis, 1997;Dunn et al, 2002;Vincent et al, 2011).…”

“…Other well-logs were used to produce inter-well correlations. Due to technical shortcomings, only the GR well-log could be completed on well GBD4, preventing any comparison between NMR laboratory experiments (Catinat et al, 2023) and CMR log data. The well-logs analysed in this paper are illustrated in Fig.…”

“…Owing to high laboratory experiment costs for geothermal operators and limited core availability, only two sets of laboratory NMR analyses have been carried out on cores from the Middle Jurassic geothermal reservoir of the Paris Basin. A single investigation was conducted on Middle Jurassic limestones collected from the eastern part of the Basin (Brigaud et al, 2014), supplemented more recently by a second one from the central part of the basin in geothermal well GBD4 (Catinat et al, 2023).…”

“…Four geothermal wells have been selected to pursue these objectives related to the petrography and petrophysics of the Middle Jurassic limestones of the Paris Basin. The Schlumberger Doll Research (SDR) permeability equation is commonly used for predicting permeability (k), but another equation (k m ), previously determined on specific Bathonian limestones in the basin, was used to improve permeability prediction in the geothermal reservoir (Catinat et al, 2023). An additional objective is thus to accurately identify the similarities and differences observed in permeability predictions derived from these equations.…”