Integration Of Geophysical Data Research Articles

Complexity of near-surface deformation and subsurface structure of the Chihshang creeping fault-line scarp, eastern Taiwan: insights from integration of geological and geophysical data

The precise position and geometry of a fault and the recognition of contemporary active strands are pivotal elements for formulating regulations for earthquake fault zones and fault setbacks. The western frontal escarpment toe of the Coastal Range in Tapo, eastern Taiwan is commonly considered as the plausible location of the N18°E-trending, east-dipping Chihshang creeping seismogenic fault. Frontal collapse and flattening of reverse faulting, in addition to fluviation and landslide have complicated the process for defining the Chihshang fault configuration. We used a multidisciplinary approach, combining site investigation, geological core analysis and correlation, resistivity prospecting, and inclinometer monitoring, to illuminate the subsurface structure and deformation of the leading edge of the Chihshang fault at Tapo Elementary School. We found that (1) the Chihshang main fault is a contact of alluvium deposits and the mudstone of Lichi mélange, and has a dip angle of approximately 77° within the resistivity gradation zone 55 m east of the toe of the geomorphic escarpment; (2) it has a 2-year cumulative horizontal displacement of 20.7 mm northwestward and continuously creeps without seasonal variation; and (3) the active deformation on the escarpment results from a combined effect of fault creeping and slow gravity sliding of the mass which is steadily supplied by the Chihshang reserve faulting. A mechanism of faulting-relay landsliding is proposed to understand the active deformation on the escarpment. Great caution is needed in the interpretation of the aseismic surface ruptures along the inferred trace of reverse creeping faults as fault branching.Graphical

Three-Dimensional Prospective Modeling and Deep Metallogenic Prediction of the Lintan Gold Deposit in Guizhou Province, China

The Lintan gold deposit, located in the “gold triangle” of Qianxinan, Guizhou Province, has become a focal point for implementing the “exploring near existing deposits” strategy, aiming to identify another large-scale gold deposit within the region. This study addresses the challenges of deep-edge mineral exploration in the Lintan gold deposit by adopting a metallogenic system perspective. Using a multidisciplinary approach, it integrates geological, geophysical, and geochemical datasets to construct various three-dimensional (3D) visualization and prospectivity models. The research leverages geostatistical theories and methods, multisource digital information analysis, and advanced 3D modeling and visualization techniques to verify mineralization anomalies. These efforts expand the scope of prospectivity evaluation for the deep-edge regions of the Lintan gold deposit into 3D space. In the 3D spatial framework, this study elucidates the metallogenic geological characteristics, geophysical anomalies, and geochemical signatures within the study area. Building upon this foundation, it conducts a comprehensive analysis and evaluation of geological, geochemical, and geophysical prospecting indicators under multisource geoscience datasets. This approach transitions from known to unknown domains, effectively reducing the ambiguities and uncertainties associated with single-source data interpretations. The findings demonstrate that, under the guidance of geological prospectivity models, the effective integration and synthesis of geological, geophysical, and geochemical data can reveal the interrelationships between metallogenic geological bodies and the contributing factors of the metallogenic system. This enables the identification of anomalous information associated with metallogenic geological bodies and facilitates the spatial localization and prediction of target areas for deep-edge mineral resources. The proposed methodology provides novel insights and techniques for deep-edge mineral exploration. Comprehensive analysis indicates significant prospectivity for mineral resource exploration in the deep-edge regions of the Lintan gold deposit.

Integration of airborne geophysical data for the characterization of the geothermal system in Valle del Cura, high central Andes

The Valle del Cura region, located in the High Central Andes, over the Pampean flat-slab segment, exhibits several geothermal manifestations suggesting structural rather than magmatic controls. However, the structural and favorable conditions of this geothermal system have not been studied in detail yet. By integrating high-resolution airborne geophysical data with existing geological information using GIS tools, we can better characterize the structural controls of the thermal areas. The application of the upward continuation filter and tilt-angle derivative to the reduced to pole magnetic anomaly map allowed us to delineate structural lineaments that correlate well with known faults in the area. Euler deconvolution successfully identified local structures controlling the subsurface water upwelling and provided reliable depth estimations. Results indicate that the Despoblados area is characterized by NW-oriented deep structural controls reaching depths of up to 5 km. In contrast, the Bañitos-Gollete and the northern thermal areas are controlled by the intersection of N-S with E-W shallow structures at less than 3 km deep. Aeroradiometric data provided additional information for the characterization of several lithological units based on the dominance of radioelements (K, Th and U) in near-surface rocks by using individual and ternary maps. In addition, estimations of radiogenic heat production were crucial for assessing the potential energy of geothermal resources in the region. In particular, higher average values were obtained for igneous and metamorphic basement which may contribute to the geothermal gradient and temperature distribution at depth. Further studies, including new geophysical data acquisition and field verification, are still needed to fully describe the regional and local structures involved in these geothermal areas.

Mineralization characteristics of Lead-Zinc-Copper deposits in Akdağmadeni Region (Northern Central Anatolia, Türkiye): Integration of field study, geochemical, isotope, and geophysical data

The Akdağmadeni region is one of the important Pb-Zn-Cu metallogenic provinces in Türkiye. Most of the Pb-Zn-Cu deposits in the region are located near granitoid intrusions within metamorphic rocks, and they are typically classified as skarn-type ores associated with granitoids. However, no relationship has been determined between the Başçatak prospect and any granitoid outcrop. This raises the question of whether the Pb-Zn-Cu mineralization in the region is related to granitoids or if magmatic processes remobilized pre-existing mineralization. Observations from field studies suggest that mineralization in the Başçatak prospect is a stratiform type, metamorphosed occurrence that might have occurred earlier than the granitic intrusions. The geochemical data indicated that the granitoids have low-grade, subeconomic Cu potential and no Zn productivity potential, supporting these observations. Geophysical data also show that there is no intrusive body beneath this prospect. Granitoid-related deposits (Karapir - Ortaköy and Akçakışla) exhibit two distinct occurrences around the contact between the granite and the surrounding metamorphic rocks. The first type of occurrence (O-1) is formed at the contact and contains magnetite, pyrrhotite, and chalcopyrite. The second type of occurrence (O-2) is located outside the contact and is rich in sphalerite and galena. Both O-1 and O-2 contain skarn minerals along with ore minerals. The δ34S values of sulfide minerals from the deposits range from −0,7 to 7,5 ‰ (V-CDT). These values overlap with those of both magmatic sulfur and reduced sulfur from seawater-dissolved sulfate, making it difficult to suggest a sulfur source without additional data. Lead isotope compositions of the galenas from all deposits plot above the average crustal growth curve, suggesting an upper crustal and orogenic source similar to Western Mediterranean and Türkiye type materials described in the literature for the lead, source in different time intervals. Furthermore, Pb isotope geochemistry suggests a contemporaneous age with the host metamorphic rocks (Carboniferous – Lower Permian) for the Başçatak prospect. These results support observations indicating a syn-genetic formation for the Başçatak prospect. The age range of granite-related deposits forms two sub-groups:105–77 Ma and 61–50 Ma corresponding to the Upper Cretaceous and Paleocene transition. These data indicate that that the galenas were formed in two different stages in these mineralizations. Stratiform mineralization in the Başçatak prospect likely formed either through exhalative sedimentary processes by hydrothermal fluids or through chemical sedimentary processes under reductive conditions in a marine environment during metamorphism. O-1 appears to have been formed by hydrothermal fluids developed during granitic magmatism. A plausible formation process for O-2 involves the leaching of sulfur, lead and other metals from Başçatak type enrichments in metamorphics, with transportation and deposition within the epidotized calc-schist and marbles outside the granitoid contacts. The uplift of granitic intrusions prepared the channels and depositional environment for O-2 and caused heating of the hydrothermal fluids during this mineralization period.

Hydraulically linked reservoirs simultaneously fed the 1975–1984 Krafla Fires eruptions: Insights from petrochemistry

The 1975–1984 Krafla Fires in northeast Iceland was the first plate-boundary rifting episode to be tracked using seismic and geodetic monitoring. Geophysical observations from this episode have inspired conceptual models of magma transport during plate spreading, but a lack of complementary petrologic insights has hindered a holistic understanding of the events. To address this knowledge gap, we studied the petrochemistry of all nine Krafla Fires basaltic eruptions. Our large dataset of new whole-rock, matrix glass and mineral analyses from samples collected during or shortly after each eruption reveal a clear compositional bimodality in the erupted magmas that persisted across the episode, with evolved quartz tholeiite (MgO = 5.7–6.4 wt.%) erupted inside Krafla caldera, and more primitive (usually olivine-normative) tholeiite (MgO = 6.4–8.7 wt%) erupted north of the caldera margin. Barometric calculations indicate tapping of these magmas from distinct reservoirs: a primitive lower-crustal reservoir at a most probable depth of ∼14–19 km, and a more evolved, shallower reservoir at a most probable depth of ∼7–9 km beneath the caldera. These reservoirs were tapped simultaneously in several of the nine eruptions, and in three events the two magma types mixed near the northern caldera margin. Varying levels of trace element depletion in the deep-sourced primitive melts reflect incomplete mixing of diverse mantle-derived melts at depth; the most enriched of these melts could be parental to evolved inside-caldera magma via fractional crystallization. Clinopyroxene rims on gabbroic nodules from primitive September 1984 lavas record lower crustal pressures, while diffusion models suggest that these rims grew up to within a few months before eruption. Ascent of the primitive magma from the lower crust thus occurred over timescales much shorter than eruptive repose periods, without prolonged stalling at shallow depths. These observations are inconsistent with the view that the eruptions were entirely fed by lateral magma outflow from the shallow reservoir. They instead require some decoupling of the flow paths of the two magma types: the primitive magma either bypassed the sub-caldera reservoir laterally or ascended vertically beneath the northern vents. The two reservoirs nonetheless shared a hydraulic connection and jointly responded to rifting. Comparison of the Krafla Fires with other rifting events and eruptions highlights the complexity and diversity of magma transport during plate boundary rifting events, which is not yet captured by a generalizable model. Integration of petrologic, geochemical and geophysical data is essential to provide a holistic view of future rifting events in Iceland and at other spreading centres.

Fuzzy c-mean (FCM) integration of geophysical data from an iron-oxide copper gold (IOCG) deposit under thick cover

Geophysical methods depend on a range of physical and chemical mechanisms, and each method has different sensitivities and resolution of Earth parameters, and over different scale lengths. Additionally, such geophysical methods will also have their own statistical characteristics. Thus, it is a significant challenge to combine different methods through a single inversion framework. Rather than attempting to find an optimal and single model for different geophysical responses, an alternative approach is to use FCM clustering to identify clusters of parameters from two or more different geophysical data sets or models that have similar statistical properties. In this paper, we apply the FCM approach to integrate data and model sets for an array of 100 broadband magnetotelluric (MT) and 100 passive seismic receivers spaced 1 km apart on a 10 by 10 grid above the Vulcan IOCG prospect in the Olympic Cu–Au Province, southern Australia. The challenge for exploration of the Vulcan prospect is that it lies beneath 750 m of regolith sedimentary cover, no single geophysical method provides a unique characterization of the deposit geometry, and drilling is very expensive. Fuzzy c-mean cluster analyses are undertaken in 2D for gravity data and shear-wave velocity model data for basement depths beneath cover and in 3D for shear-wave velocity and electrical resistivity model data. Fuzzy c-mean clustering is shown to provide a simple and efficient method of integrating different geophysical measurements to produce a geological framework that can be verified with drilling information.

Advances in Thermal Infrared Remote Sensing Technology for Geothermal Resource Detection

This paper discusses thermal infrared (TIR) remote sensing technology applied to the delineation of geothermal resources, a significant renewable energy source. The technical characteristics and current status of TIR remote sensing is discussed and related to the integration of geological structure, geophysical data, and geochemical analyses. Also discussed are surface temperature inversion algorithms used to delineate anomalous ground-surface temperatures. Unlike traditional geophysical and geochemical exploration methods, remote sensing technology exhibits considerable advantages in terms of convenience and coverage extent. The paper addresses the major challenges and issues associated with using TIR remote sensing technology in geothermal prospecting.

Impact of Fluid Distribution and Petrophysics on Geophysical Signatures of CO2 Storage Sandstone Reservoirs

AbstractCarbon Capture and Storage (CCS) is a key element to achieving net‐zero energy challenge timely. CCS operations require the integration of geophysical data, such as seismic and electromagnetic surveys, numerical reservoir models and fluid flow simulations. However, the 10–100s m resolution of seismic imaging methods complicates the mapping of smaller scale rock heterogeneities, while borehole measurements commonly show large fluctuations at sub‐cm scales. In this study, we combine laboratory data, well‐logging, rock physics theories and a proof‐of‐concept time‐lapse seismic modeling to assess the effect of pore‐scale fluid distribution and petrophysical heterogeneities on the expected performance of whole‐reservoir CCS operations in deep saline aquifers, by analogy to the Aurora CCS site, North Sea. We monitored the elastic and electrical properties of three sandstone samples with slightly different physical and petrographic properties during carbon dioxide (CO2) flow‐through tests under equivalent in situ effective pressure. We inferred the CO2‐induced damage in the rocks from the variations of their hydromechanical properties. We found that the clay fraction, CO2‐clay chemical interactions, and porosity were the main factors affecting both the CO2 distribution in the samples and the hydromechanical response. We used seismic modeling of well‐log data and the laboratory results to estimate the reservoir‐scale time‐lapse seismic response to CO2 injection and to assess the effect of the rock heterogeneities in our interpretation. The results show that disregarding the effect of rock heterogeneities on the CO2‐brine fluids distribution can lead to significant misinterpretations of seismic monitoring surveys during CCS operations in terms of both CO2 quantification and distribution.

Integration of geological and geophysical data for delineating groundwater potential zones at highly faulted area: a case study Cairo-Suez district, Egypt

Integration of geological and geophysical data for delineating groundwater potential zones at highly faulted area: a case study Cairo-Suez district, Egypt

Multi‐geophysical methods for characterizing fractures in an open pit mine, western Bushveld Complex, South Africa

AbstractIn the Bushveld Complex, South Africa, open pit mines are faced with a challenge of rock slope stability due to geological structures (fractures, faults and dykes) that compartmentalize the rock mass. Geophysical surveys (seismics, magnetics and electrical methods) were conducted in a 0.2 km2 area at Tharisa mine, with the goal to delineate fractures that may be potential conduits for water migration into the pit. Special processing techniques were applied to the dataset to obtain good quality seismic, magnetic and resistivity models. The P‐wave velocity models show distinct low velocities in the centre of the seismic profile, indicating the presence of weak zones associated with faulting or fracturing. Seismic reflection method was used to image the deeper discontinuities and mineralization contacts. Near surface reflections are observed throughout the profiles and are correlated with the contact between the chromitite and host rock. Ground magnetic surveys were conducted to delineate dykes and fractures. De‐trending and de‐culturing techniques were applied on the magnetic data for correcting regional and temporal variations. The low magnetic regions indicate the presence of fracture systems in the subsurface, whereas the high magnetic region is correlated with the dolerite dyke that crosscuts the pit. The electrical resistivity tomography exhibits linear low resistivity contrast zones that differentiate between the fractured and undisturbed hard rock at an estimated depth of 4–10 m. Resistivity shows discontinuities that suggests the presence of fracturing and dyke‐host rock contacts. Correlation among magnetics, P‐wave velocity models, resistivity section and seismic data is evident when overlaying the different datasets, implying that the low magnetic regions are highly weathered and prone to fracturing. The integration of geophysical data is encouraging, because it was able to image the depth to the bedrock, fractures within the host rock and dyke in a complex mining environment.

Integration of Geological and Geophysical Approaches in Meeting the Challenges of Uranium Exploration in the Cuddapah Basin — a Case Study from Chitrial Area, Nalgonda District, Telangana

Abstract Uranium exploration in the Cuddapah Basin is both scientifically and logistically challenging. An integrated multidisciplinary approach is adopted to infer the subsurface geology. Very Low Frequency Electromagnetic (VLF-EM) survey, conducted over parts of Chitrial outlier, Nalgonda district, Telangana, has indicated thirteen subsurface conductors. Two prominent trends, viz. NE-SW and NNE-SSW/N-S, are revealed from the stacked profiles and pseudosections. Six of these conductors (2 NE-SW and 4 NNE-SSW/N-S trending) are found to have appreciable strike extent (>300 m) with steeply dipping (60°–75°) to vertical attitude. These conductors are interpreted to extend ≥75 m into the basement from the overlying sediments. The ballooned-up zones of low apparent resistivity especially in the sediments, associated with one NNE-SSW/N-S and two NESW trending conductors, are interpreted as zones of hydrothermal alteration and, therefore, demarcated as potential targets for subsurface exploration by inclined boreholes. This study indicates that integration of geophysical data with geological features will help in optimizing the exploration input and narrowing down the target zones for uranium exploration even in deeper reaches of the Cuddapah Basin.

How can an integrated multi-method geophysical approach optimise the groundwater management in the Chalk aquifer? Case study of the Seine fault system (France, Normandy)

The Cretaceous chalk aquifer is a strategic water resource in the north of France, especially in Normandy where it faces increasing pressure in terms of its quality and availability. The effective and sustainable manage of this resource relies on a deep understanding of its complex geological and hydrogeological nature. However, modelling this hydrosystem has its limitations due to the spatial and qualitative heterogeneity of the data available. The integration of geophysical data using various methods and scales has improved the geological knowledge by identifying the different chalk formation and highlighting the geometry of the Seine fault system near Rouen. Geophysical analysis has revealed highly complex fault geometries in this area and clarified their impact on the chalk formations. Additionally, it has provided detailed information about the vertical heterogeneity of the chalk, both geologically and hydrogeologically. This new knowledge feeds into the existing 3-D regional geological model, especially in areas with limited data. Supporting hydrogeological modelling, this updated model has already enabled to drill new boreholes. In the future, it will contribute to a better understanding and management of groundwater resources in this region.

Aquifer systems in dry regions: Hydro-geophysical and geochemical investigations providing insights into water resources in southeast Tunisia

Water demands from agriculture and industry have intensified groundwater extraction, prompting a focused study to bolster water resources, particularly at Gabès region (Southeastern Tunisia). Through extensive geologic and geophysical investigations, the reservoir geometry and structural architecture of crucial aquifers, notably the Mio-Plio-Quaternary and Cretaceous aquifers have been studied. The integration of geochemical and geophysical data allows for a nuanced assessment of fault structures and groundwater hydrodynamics. Advanced techniques, like horizontal gradient and upward extension unveils structural features and density contrasts with precision. This study extends to a spatiotemporal analysis of aquifer hydrodynamics and groundwater mineralization. The Gabès aquifer system exhibits four groundwater facies: Ca–Mg–SO4, Na–Cl–NO3, Ca–Mg–HCO3, and Na–K–HCO3. Results reveal relative isotopic depletion, suggesting recharge under colder climates and at higher altitudes. However, the study underscores the impact of climate change, with increasing temperature and dwindling precipitation in North Africa, since the mid-20th century. This research is a relevant contribution to sustainable water management by emphasizing the impact of climate change scenarios and groundwater resources management. The detailed exploration of hydrogeological characteristics and aquifer dynamics in the Gabès region is pivotal on effective management of groundwater resources strategies in semi-arid environments.

Delineation of LNAPL plumes in a clay-rich site in Gyeongsangnam-do Province, South Korea: integration of geophysical survey data with borehole data and soil sampling information.

To effectively delineate the spatial distribution of oil contaminant plumes, geophysical methods indirectly measure the physical properties of the subsurface and can provide spatial information and images on a large scale, as opposed to traditional direct methods such as borehole drilling, sampling, and chemical analysis, which are time-consuming and costly. However, interpreting geophysical responses over non-aqueous phase liquid (NAPL)-contaminated sites is not straightforward due to inconsistent responses from biodegraded oil contaminants. In this study, we performed multi-geophysical surveys including seismic refraction, ground-penetrating radar, electrical resistivity tomography (ERT), and induced polarization (IP) surveys, to locate NAPL-contaminated zones in a clay-rich site. To reduce ambiguity in discriminating between oil contaminants and clay layers, we first figure out the geological structure of the site by interpreting geophysical data incorporating with borehole data. The ERT data highlighted the heavily contaminated regions in the unsaturated zone but were less distinctive below groundwater levels. Conversely, IP responses revealed potential hotspots within the clay layers, extending beneath the groundwater. Considering the 3D geological model, NAPL-contaminated zones are properly delineated through interpretation of ERT and IP data together with borehole data, and the contaminant source zone was properly estimated within the site.

Architectural rift geometry of the Rio do Peixe Basin (Brazil): Implications for its tectonic evolution and Precambrian heritage

Preexisting shear zones in the basement may influence the formation of normal faults in rift environments. However, the specific role and interaction between these preexisting shear zones and younger rift faults in controlling the growth of normal faults remain an area of limited understanding. The Rio do Peixe Basin (RPB), located in Brazil, was the subject of a comprehensive study using integrated airborne magnetic analysis, 2D and 3D seismic interpretation, and 3D gravity modeling. This study investigated tectonic evolution and Precambrian heritage by examining the role of basement structures in controlling the internal geometry of the RPB. The integration of geophysical data supported by field data showed that the underlying basement structures significantly influence the geometry of the basin sedimentary fill. E–W-striking structures controlled the opening of the RPB and the development of the depocenters of the basin. NE–SW-striking structures influenced the segmentation of the depocenters and, consequently, the internal geometry of the basin. Furthermore, the study revealed the migration of depocenters toward the NE associated with developing the NE–SW-striking segment of the Portalegre Fault attributed to the basin-opening process. By investigating the underlying crustal architecture, this comprehensive geophysical study sheds light on the architectural rift geometry of the RPB. The findings underscore the influence of basement structures on the internal basin architecture and provide valuable insights into its tectonic evolution and Precambrian heritage.

Zones of Weakness Within the Juan de Fuca Plate Mapped From the Integration of Multiple Geophysical Data and Their Relation to Observed Seismicity

AbstractThis study aims to explain the nonuniform earthquake pattern along the Cascadia Subduction Zone. In particular, we investigate the relationship between the tectonic features of the subducting oceanic Juan de Fuca slab and the onshore seismicity pattern. We have integrated multiple geophysical data sets toward three general objectives. The first study intends to study variations in physical properties along three 2‐dimensional models through regions of different seismicities that combine public gravity, magnetic, and seismic data sets. These models reveal multiple zones of decreased crustal density that we interpret as regions of weaker oceanic crust. The second objective is to delineate major tectonic features by performing spatial analysis of potential fields. The overall methodology comprises gravity and magnetic data filtering, followed by lineaments mapping and cross‐referencing interpretation with available seismic reflection data. This process allows delineating zones of crustal weakness by extrapolating outside our three 2‐D models. We also map multiple seamounts that appear to cluster along identified zones of weaker crust. Third, we investigate the relationship between the mapped tectonic elements, namely the zones of weak crust with accompanying seamounts, and the observed seismicity trends within the subducted slab. The alignment between those suggests that mapped weak crust zones and associated seamounts may have an influence on the overall subduction process. As more of these structures are heading toward the Washington portion of the margin than to the Oregon portion, more earthquakes are observed in the north than in the south.

A Coupled Poro-Elastic Fluid Flow Simulator for Naturally Fractured Reservoirs

Naturally fractured reservoirs are characterized by their complex nature due to the existence of natural fractures and fissures within the rock formations. These fractures can significantly impact the flow of fluids within the reservoir, making it difficult to predict and manage production. Therefore, efficient production from such reservoirs requires a deep understanding of the flow behavior via the integration of various geological, geophysical, and engineering data. Additionally, advanced simulation models can be used to predict reservoir behavior under different production scenarios and aid in decision making and effective management. Accordingly, this study presents a robust mathematical two-phase fluid flow model (FRACSIM) for the simulation of the flow behavior of naturally fractured reservoirs in a 3D space. The mathematical model is based on the finite element technique and implemented using the FORTRAN language within a poro-elastic framework. Fractures are represented by triangle elements, while tetrahedral elements represent the matrix. To optimize computational time, short to medium-length fractures adopt the permeability tensor approach, while large fractures are discretized explicitly. The governing equations for poro-elasticity are discretized in both space and time using a standard Galerkin-based finite element approach. The stability of the saturation equation solution is ensured via the application of the Galerkin discretization method. The 3D fracture model has been verified against Eclipse 100, a commercial software, via a well-test case study of a fractured basement reservoir to ensure its effectiveness. Additionally, the FRACSIM software successfully simulated a laboratory glass bead drainage test for two intersected fractures and accurately captured the flow pattern and cumulative production results. Furthermore, a sensitivity study of water injection using an inverted five-spot technique was tested on FRACSIM to assess the productivity of drilled wells in complex fractured reservoirs. The results indicate that FRACSIM can accurately predict flow behavior and subsequently be utilized to evaluate production performance in naturally fractured reservoirs.

The specification of hydraulic units of flow – the key direction for the classification of terrigenous reservoirs (in the context of South-West Kamyshitov field)

The paper considers a classification method of terrigenous reservoirs based on Hydraulic Units definition, introduced by Ameafule et al. in 1993. The typical groups of reservoirs of Jurassic and Cretaceous sediments with the similar properties of the pore volume were identified based on the results of the standard laboratory studies of the core material. The integration of core and geophysical data were carried out in the process of interpretation of the logging data. The defined classification of the rocks allowed conducting the specific prediction of the permeability by whole penetrated section of South-West Kamyshitov field.

Well log prediction while drilling using seismic impedance with an improved LSTM artificial neural networks

Well log prediction while drilling estimates the rock properties ahead of drilling bits. A reliable well log prediction is able to assist reservoir engineers in updating the geological models and adjusting the drilling strategy if necessary. This is of great significance in reducing the drilling risk and saving costs. Conventional interactive integration of geophysical data and geological understanding is the primary approach to realize well log prediction while drilling. In this paper, we propose a new artificial intelligence approach to make the well log prediction while drilling by integrating seismic impedance with three neural networks: LSTM, Bidirectional LSTM (Bi-LSTM), and Double Chain LSTM (DC-LSTM). The DC-LSTM is a new LSTM network proposed in this study while the other two are existing ones. These three networks are thoroughly adapted, compared, and tested to fit the artificial intelligent prediction process. The prediction approach can integrate not only seismic information of the sedimentary formation around the drilling bit but also the rock property changing trend through the upper and lower formations. The Bi-LSTM and the DC-LSTM networks achieve higher prediction accuracy than the LSTM network. Additionally, the DC-LSTM approach significantly promotes prediction efficiency by reducing the number of training parameters and saving computational time without compromising prediction accuracy. The field data application of the three networks, LSTM, Bi-LSTM, and DC-LSTM, demonstrates that prediction accuracy based on the Bi-LSTM and DC-LSTM is higher than that of the LSTM, and DC-LSTM has the highest efficiency overall.

A Novel Methodology for the Stochastic Integration of Geophysical and Hydrogeological Data in Geologically Consistent Models

AbstractTo address groundwater issues, it is often necessary to develop geological and hydrogeological models. Combining geological, geophysical and hydrogeological data available on a site to build such models is often a challenge. This paper presents a methodology to integrate such data within a geologically consistent model with robust error estimation. The methodology combines the Ensemble Smoother with Multiple Data Assimilation (ESMDA) algorithm with a hierarchical geological modeling approach (ArchPy). Geophysical and hydrogeological field data are jointly assimilated in a stochastic ESMDA framework. To speed up the inversion process, forward responses are computed in lower‐dimensional spaces relevant to each physical problem. By doing so, the final models take into account multiple data sources and regional conceptual geological knowledge. This study illustrates the applicability of this novel approach using actual data from the upper Aare Valley, Switzerland. The results of cross‐validation show that the combination of different data types, each sensitive to different spatial dimensions, enhances the quality of the model within a reasonable computing time. The proposed methodology allows the automatic generation of groundwater models with robust uncertainty estimation and could be applied to a wide variety of hydrogeological issues.