Magnetotelluric data analysis using 2D inversion: A case study from Al-Mubazzarah Geothermal Area (AMGA), Al-Ain, United Arab Emirates

Abstract

Geothermal manifestations (hot springs) emerge in the Al-Mubazzarah Geothermal Area (AMGA), Al-Ain city, Abu Dhabi Emirate, United Arab Emirates. This paper presents the application and results of a Magnetotelluric (MT) survey, which was carried out in 2017 at the AMGA geothermal field. The MT method was used to investigate the variations in the electrical conductivity beneath the AMGA. This study focuses on characterizing the patterns of subsurface electrical conductivity of the AMGA geothermal reservoir. Dimensionality analysis of the measured MT data indicate that 2D inversion is appropriate for the subsurface resistivity interpretation. The inversion results support a model consisting of three resistivity-defined layers; from top to bottom they are: (1) a shallow layer with resistivity ranging from 10 to 20 Ωm, representing recent alluvial and windblown deposits, (2) a second conductive layer with resistivities less than 10 Ωm, beneath the first layer. This layer is recognized as the Tertiary carbonate sequence in the region, (3) a deep, moderate to relatively high resistive zone, 10–30 Ωm beginning at 800 m depth and reaching 4 km depth in the northern part of the profile, representing Mesozoic basement rocks. The observed moderate to high resistivity zone (10–30 Ωm) in the 2D model may represent a region where the hot groundwaters originated (geothermal reservoir), with the hottest geothermal located at a depth greater than 4 km. The geothermal reservoir zone is also represented by a low to high density contrast and a low to moderate magnetic susceptibility, as indicated in the inverted potential field data models, and confirmed the existence of a north dipping major fault.

Identification of shale gas existence based on 2-dimensional magnetotelluric data in the Kutai basin, East Kalimantan, Indonesia

“…The resistivity and thickness of each layer are parameters in 1-dimensional modeling [37]. The results of 1-dimensional inversion modeling are in the form of a resistivity profile for each measurement point, while for 2-dimensional modeling, they are in the form of modeling the distribution of subsurface resistivity [38], [39].…”

Geobody estimation by Bhattacharyya method utilizing nonlinear inverse modeling of magnetic data in Baba-Ali iron deposit, NW Iran

“…Results confirmed an increased correlation between susceptibility and density models in horizontal and vertical directions and demonstrated the existence of isolated sources with high density and magnetization distinctions. Saibi et al [ 70 ] performed a magnetotelluric data analysis using 2D inversion in a geothermal field. The Reservoir zone showed a low to moderate magnetic susceptibility, confirming a dipping major fault.…”

Magnetic and gravity modeling and subsurface structure of two geothermal fields in the UAE

“…Some groundwater sources are geothermal especially those associated with deep fracture systems (Saibi et al 2021b). These hot springs occurrences are found in several places in the Emirates including Abu Dhabi (The Green Mubazzarah-Ain Faidha) and Ras Al Khaimah Emirate (Ain Khatt) (Saibi et al 2021c(Saibi et al , 2021d. In the Abu Dhabi Emirate, just south of the city of Al Ain lies a limestone mount known as Mount (Jabal) Hafit.…”

“…The previous geophysical studies of the Al Ain area are regional and focused on the study of the structural evolution of Mount Hafit (Ali et al 2009;Woodward 1994;El-Mahmoudi and Gabr 2006;Saibi et al, 2017Saibi et al, , 2019aSaibi et al, , b, 2021dSaibi, 2018). Saibi et al (2021d) performed a magnetotelluric survey which discovered a geothermal reservoir beneath Green Mubazzarah (Al-Ain) in Mesozoic basement and overlying Tertiary carbonates with depths ranging from 1 to 4 km. This study confirms the existence of E-W striking steeply dipping normal faults that may connect Green Mubazzarah and the Ain Faidha hot springs.…”