bluuebunny/crossref_metadata_2025_split huggingface dataset:
Buzios Field: Characteristics and Geomechanical Challenges of the Giant Carbonate Offshore Field
Authors: Falcao F. O. L. , Chaves R. A. P. 
Published: September 2023

ABSTRACT
Buzios Field, a pre-salt reservoir located approximately 180 km away from Rio de Janeiro coast, in Santos Basin, is characterized by its great dimensions: Its extensions involve an area of 852 km2 and presents a 400 m of net pay in average, in a water depth of 2000 meters, below an interval of another 2000 m of salt, which is situated below an interval of 1000 m of post-salt sediments. Buzios great production potential may be illustrated by the performance of its production wells: one single well has reached the spectacular mark of 70 kboed of peak production. Along with all this production greatness, come the associated geomechanical challenges: hydromechanical behavior of faults, fractures, and karst; thermal effects due to cold water injection in a warm porous media; determination of relative permeability curves within fractures considering geomechanical effects - just to mention a few. In this way, the aim of this paper is to present the main characteristics of Buzios Field, the associated geomechanical challenges and how Petrobras’ team deals with them, taking the geomechanical role beyond safety, moving towards reservoir management.

INTRODUCTION
Buzios Field, a pre-salt reservoir located approximately 180 km away from Rio de Janeiro coast, in Santos Basin, is characterized by its great dimensions: Its extensions involve an area of 852 km2 and presents a 400 m of net pay on average, in a water depth of 2000 meters, below an interval of another 2000 m of salt, which is situated below an interval of 1000 m of post-salt sediments. It was first discovered in 2010 by the 2-ANP-1-RJS well. It had its commerciality declared in 2013 after a 3D seismic acquisition, reprocessing, and a long-term test. Three other extended tests were performed in 2015, 2016, and 2017, which confirmed its excellent oil production potential, good reservoir communication, and allowed drainage plan adaptations. In the following years four production units were installed, each of them with a processing capacity of 150 kbpd. These FPSOs (Floating Production Storage and Offloading units) made it possible to reach the outstanding mark of taking less than two years to reach 600 kbpd of production, starting from its first oil. As a reference, Tupi Field, the previous pre-salt giant carbonate reservoir, also located in Santos Basin, took almost 6 years to reach the same daily production. Marlim, the previous giant field, a turbidite sandstone, took almost 11 years (Figure 1).
Relationship Between Static and Dynamic Elastic Moduli in Carbonates
Authors: Soustelle V. , ter Heege J. , Wassing B. 
Published: September 2023

ABSTRACT
In an effort to assess the seismic potential of geothermal plays in Dinantian carbonate reservoirs in the Netherlands and Belgium, geomechanical induced seismicity models were developed. However, the static elastic moduli E (Young's modulus) and v (Poisson's ratio) formation properties are required as input for these models. Due to the lack of available core plugs from wells in the area of interest and unsatisfying static-dynamic relationship in the literature, we designed a series of experiments to build a new static-dynamic relationship for Dinantian carbonates that take into account the effective confining pressure ((Equation)). The triaxial experiments were carried out on massive limestone and karstified dolostone collected in a quarry near the Belgium Dinantian geothermal play. The static and dynamic elastic moduli Es, Ed and vs, vd were measured at various (Equation) ranging from 1 to 35 MPa (mean effective stress in the geothermal reservoirs). We established the following relationships for the karstified dolostone:
(Equation)
And the massive limestone:
(Equation)

INTRODUCTION
Geothermal heat is expected to become an important sustainable energy source to help reach the targets set by the National Climate Agreement of the Netherlands, which aims to reduce greenhouse gas emissions by 50% in 2030 and attain zero net carbon emissions by 2050. New geothermal plays, such as the Dinantian carbonates, are targeted to reach these objectives. However, they present geological characteristics quite different from the more conventional sandstone reservoir usually targeted in the Netherlands. The Dinantian carbonates are also heterogeneous and present various geological characteristics that affect the flow and mechanical properties of the reservoirs. In the southeast of the Netherlands, two geothermal doublets in the Dinantian have been stopped after a limited number of seismic events were recorded with a maximum magnitude of ML 1.7 (Baisch & Vörös, 2019). Seismicity has also been recorded in a Dinantian geothermal play near Mol in Belgium. Although the seismic activities were related to geothermal production, the causal mechanisms are still poorly constrained (Ter Heege et al., 2020).
Compaction of Crushed Salt for Safe Containment - Overview of Phase 2 of the KOMPASS Project
Authors: Friedenberg L. , Czaikowski O. , Lerch C. , Müller-Hoeppe N. , Rahmig M. , Bartol J. , Düsterloh U. , Lerche S. , Saruulbayar N. , Laurich B. , Svensson K. , Zemke K. , Thiedau J. , Liu W. , Gartzke A. K. , Popp T. , Lüdeling C. , Rölke C. , Rabbel O. , Reedlunn B. , Bean J. , Mills M. , Coulibaly J. B. , Spiers C. , De Bresser J. H. P. , Hangx S. , van Oosterhout B. 
Published: September 2023

ABSTRACT
Crushed salt may be used as backfill material and sealing measures of open cavities, drifts and shafts in nuclear waste repositories located in rock salt formations. The host rock salt will gradually compact the crushed over time due to salt creep. A comprehensive understanding of the crushed salt compaction process is essential, yet crushed salt compaction involves several thermal-hydraulic-mechanical (THM) coupled processes and is influenced by internal, as well as external conditions. The current understanding has some important knowledge gaps. For example, the porosity/permeability evolution, especially for the low porosity range is not known in its entireness and the calibration of numerical models is not finished yet. The KOMPASS projects were initiated with the aim to reduce these knowledge gaps and improve predictions of crushed salt behavior. This paper gives an insight in the KOMPASS projects with focus on the outcomings of the second phase. The experimental program for a detailed investigation of crushed salt compaction is presented. In the microstructural investigations, microscale indicators were found that can clearly be related to pre-compaction treatment. The numerical work showed that deficits still exists in the simulation of crushed salt compaction with the available constitutive models.

INTRODUCTION
Rock salt is considered as a possible host rock formation for the underground disposal of high-level nuclear waste in several countries. The safety concept for a salt repository in Germany is based on a multi-barrier system including the rock salt as geological barrier, geotechnical seals ensuring the safe containment and the waste canisters (Bertrams et al., 2020). For backfilling and sealing measures of open cavities crushed salt will be used due to its favorable properties as mined-off material, its easy availability and its lithological characteristics which guarantee a maximum compatibility with the host rock. The use of crushed salt for barriers and seals represent an important paradigm shift in repository design in Germany, since crushed salt previously served only as stabilizing backfill.
Numerical Analysis for the Simulation of Crushed Salt Compaction Behavior
Authors: Friedenberg L. , Olivella S. , Düsterloh U. 
Published: September 2023

ABSTRACT
In Germany, rock salt is considered as a possible host rock formation for a repository for high-level nuclear waste. Crushed salt will be used for backfilling and sealing measures of open drifts and shafts, providing the tightness of the repository and the safe containment of the waste in long-term. For safety assessment, a qualified prognosis of the crushed salts long-term behavior is crucial. This includes full knowledge and understanding of the thermal-hydraulic-mechanical coupled process, as well as a reliable numerical prediction of the compaction in long-term. In the current state uncertainties still remain with respect to the numerical simulation of crushed salt compaction processes, especially in the low porosity range (≤ % 5). This paper presents an approach for the modification of a constitutive model formulation implemented in the finite-element code CODE_BRIGHT with the objective to improve the numerical reproducibility of crushed salt compaction. The shortcomings are exemplary presented by means of the simulation of the triaxial compaction test TUC-V2. Based on the findings two approaches for the modification of the geometry-based model formulation are presented.

INTRODUCTION
In Germany, rock salt is considered as a possible host rock formation for the deep geological disposal of high-level nuclear waste. The safety concept is based on a multi-barrier system including the geological barrier rock salt, geotechnical seals, backfill material and the waste canisters (Fig. 1). Immediately after the disposal, the sealing function will be given by the waste matrix, waste canisters and geotechnical barriers. The rock salt as geological barrier and the backfill material will provide the sealing function in the long-term.
The backfilling of open cavities, drifts and shafts will be done with crushed salt, since it is a long-term stable material, easily available (mined-off material) and guarantees a maximum of physo-chemical compatibility with the host rock. Due to the creep ability of the rock salt, the crushed salt backfill becomes naturally compacted with time by convergence of the open cavities. It is expected that during the compaction process, porosity, and permeability of the crushed salt decrease down to barrier properties comparable to undisturbed rock salt (Φ ≤ 1 %).
Post-Fracturing Evaluation of Fractures by Interpreting the Dynamic Matching Between Proppant Injection and Fracture Propagation
Authors: Hou Lei , Zhang Fengshou , Elsworth Derek 
Published: September 2023

ABSTRACT
This study presents a new data-driven approach to interpreting fracture evolutions by analyzing the dynamic matching between proppant injection and fracture propagation. Proppant settling in low-viscosity fluids accumulates at the bottom of the fracture, compresses the flowing channel, and increases the net pressure in fractures due to increasing flow friction, which is the inherent correlation between proppant injection and fracture propagation. Evaluating the flow status of injected proppant in fractures may reveal how much fractures have been filled with proppant, and then estimate the fracture propagation indirectly - the fundamental logic of this study (using proppant as an indicator to detect the underground fractures). To accomplish this new conception, a machine-learning-based workflow is established by integrating an ensemble learning algorithm and a newly defined parameter - proppant filling index (PFI). Data from shale gas fracturing wells are collected to train the algorithm for the prediction of PFIs. The variations in PFI curves are then used to reveal the dynamic matching between proppant injection and fracture propagation, based on which the development of underground fracture volumes is estimated.

INTRODUCTION
The recognition of fracture propagation by hydraulic fracturing is a critical and generic technique for securing the injecting operation, promoting the oil and gas recovery, and evaluating the cracked reservoirs for subsequent storage of CO2 or hydrogen. In shale reservoirs, the artificial fracture system provides the essential underground channels for injection (fracturing fluids and proppant) and production (oil and gas). The safety of proppant injection and post-fracturing production rely on the flow through these artificial channels (Hou, Cheng, et al., 2022; Mayerhofer et al., 2006; Wang et al., 2018). Recent research has suggested that the fracture system is an ideal repository for CO2 or H2 in shale reservoirs, as the extremely tight matrix safely confines extraneous fluids within the fractures (Heinemann et al., 2021; Singh, 2022; Wang et al., 2022).
Seismic Source Wave Propagation Analysis Using Laboratory AE Monitoring System
Authors: Madenova Y. , Suorineni F. T. , Mukhamedyarova Z. 
Published: September 2023

ABSTRACT
The source location algorithm in microseismic monitoring systems assumes a constant velocity model, which does not account for the effects of voids, fractures, backfills, and changing mine geometry in underground mines. This study investigated Acoustic Emission (AE) signal propagation characteristics towards signal receivers in laboratory physical models to understand the influence of various factors on seismic wave velocity. It was observed that the AE wave bypasses the voids and reflects off the backfill boundaries and follows the path of least resistance described by Fermat's principle and Snell's law. AE measurements show 1) similar signal travel time to sensors located across the void when the void in the concrete blocks was empty and when filled with various backfill types; 2) increasing backfill age had no influence on the signal travel time to the sensors. It was also found that the signal triggering behavior of the sensors in the proximity of the block voids is governed by Snell's law. This study concludes that the combination of the sensor network ray tracing method with Snell's law would be a promising solution to accurately determine applicable input wave velocities in seismic monitoring systems.

INTRODUCTION
The accurate location of seismic event sources is of practical importance for identifying seismic and burst-prone areas in underground mining, particularly when the ground condition and mine geometry are continuously changing. The effective tool employed by rockburst suspected underground mines to mitigate rockburst hazards is the microseismic monitoring system. The velocity model (VM) assigned to the rockmass is a fundamental parameter in microseismic monitoring systems used to define the seismic source parameters and to locate the seismic event sources. Several researchers pointed out that high uncertainties in microseismic source location come from the VM (Husen and Hardebeck, 2010; Collins et al. 2014; Reyes-Montes et al, 2016). The microseismic systems in most mines rely on a single or layered VM that is constant for source location purposes. This velocity model assumes an isotropic and homogeneous medium with the same properties throughout the volume of interest.
A Model for Optimizing Proppant Distribution Between Perforations
Authors: Dontsov E. V. , Hewson C. W. , McClure M. W. 
Published: September 2023

ABSTRACT
Uniform proppant distribution between perforation clusters is one of the goals in hydraulic fracturing operations. However, this can be challenging to achieve, even if limited entry is used to acheive a nearly uniform fluid distribution. Two mechanisms contribute to a non-uniform proppant distribution between perforations. The first is particle settling in the wellbore, which becomes especially important towards the toe of the stage where the flow velocity is lower. The second mechanism is related to proppant inertia, whereby some particles are unable to follow the fluid streamlines and miss the perforation. In this paper, a mathematical model is developed to simulate both of these physical phenomena and is calibrated against available experimental and computational data. The model is then combined with an optimization algorithm to investigate perforation designs leading to nearly uniform proppant distribution between perforations. It is found that it is possible to significantly improve proppant placement by varying perforation orientation along the stage. If the same orientation is required for all perforations, then perforations located in the lower part of the wellbore with azimuths between 110° and 120° lead to more uniform proppant distribution, compared to other cases.

INTRODUCTION
Many studies have addressed the problem of particle distribution between perforations because this is a critical issue for optimization of hydraulic fracturing treatments. One of the first experimental studies (Gruesbeck and Collins, 1982) investigated the problem of slurry flow in a perforated vertical well, as is typical for conventional hydraulic fracturing treatments. It was observed that particle size and viscosity play a significant role on the resultant amount of proppant leaving through the perforation. With the rise of unconventional resource development as well as computational capabilities, Computational Fluid Dynamic (CFD) models have been used to address the same problem of particle turning into a perforation (Wu and Sharma, 2016; Wu, 2018). What is interesting is that in this study authors observed practically no dependence on particle size and fluid viscosity. A model that is employed in this study for the optimization purposes (see Dontsov (2023)) is able to explain such a contradiction by showing that the parameters used in Gruesbeck and Collins (1982) and Wu and Sharma (2016); Wu (2018) lead to dominance of different particle turning mechanisms, which in turn caused different sensitivities.
Evaluating Coupled Hydraulic-Mechanical Behavior in the Slate Geothermal Reservoir Using Discrete Element Analysis
Authors: Peng C. H. , Weng M. C. , Le H. K. , Shiu W. J. , Wu P. L. 
Published: September 2023

ABSTRACT
Taiwan is rich in geothermal energy, which mainly distributes in the slate area. Due to the high anisotropy and heterogeneity of slate, the properties of rock mass are quite different from isotropic rock. This study conducted a discrete element analysis to evaluate the damage area of hydraulic stimulation in the slate for the operation of a geothermal power plant. A failure criterion for slate incorporated with a transversely isotropic model was established to describe the behavior of slate. The developed model was validated using a benchmark problem of geothermal techniques under an isotropic condition. The analysis results indicated that anisotropy significantly affects stress and strain distributions. The proposed model was further applied to analyze the injection response in a slate geothermal site. The analysis results revealed that the proposed model could reasonably simulate the anisotropic coupled hydro-mechanical behavior of slate geothermal reservoirs.

INTRODUCTION
Taiwan is located in the active plate with complex volcanic activities forming different foliated metamorphic rocks such as slate and schist. The strata also have a high potential for the development of geothermal energy. The slate was formed in the Eocene to early Miocene, and showed a high degree of anisotropy and heterogeneity, so the physical properties of hereby rock mass were different from the general isotropic ones. The existing estimation method and current constitutive model may not fully reflect the mechanical behavior of foliated slate in the geothermal site of Taiwan.
Moreover, the permeability of rock formations under high temperatures was typically low, resulting in inefficient geothermal heat for energy extraction. The Enhanced Geothermal System (EGS) used high-pressure fluid to generate artificial fractures in the rock formation, which could improve the efficiency of geothermal extraction. Therefore, understanding the mechanical characteristic of rock mass comprising the damage development and fracture propagation during and after the process of high-pressure injection was a key point for the investigation. Compared with expensive and time-consuming in-situ tests, numerical simulation was more economical and potentially applied for geothermal study in the rock mass, especially under complex geological and stress conditions.
In this study, a three-dimensional hydraulic-mechanical coupled model was constructed based on the distinct element method (DEM) software 3DEC, which was first validated by simulating a benchmark problem of the US department of energy. Besides, the mechanical behavior of foliated slate was also developed by performing a series of direct shear and pull-off tests. Finally, the 3D hydraulic-mechanical coupled simulation of the Qingshui geothermal reservoir was conducted to study the stress-strain behavior and fracture propagation of the slate under short-term hydraulic injection.
Particle Size Optimization of Lost Circulation Materials: A Comprehensive Experimental Study
Authors: Li Bingxie , Feng Yongcun , Ma Chengyun , Li Sishuai , Lai Chenxi , Zhang Shuai , Su Feiyu 
Published: September 2023

ABSTRACT
Severe lost circulation in fractured formations is one of the most common and challenging problems in oil and gas drilling engineering. The lack of theoretical guidance on the selection of lost circulation materials (LCMs) for millimeter-level fractures results in unstable fracture bridging, which is prone to repeat failure. In this paper, a comprehensive laboratory experimental study was conducted with modified PPA equipment for millimeter-level fractures. The effectiveness of the LCMs is evaluated by fluid loss amount, pressure-bearing capacity, and the LCMs bridge location and integrity. Experimental results show that a single LCM size distribution cannot effectively seal millimeter-level fractures, while an optimized combination of bridging and filling particles can achieve successful sealing. It is recommended that the mass ratio of bridging particles to filling particles be 2:1. The D50 and D90 of the bridging particles should be 35-40% and 70-80% of the fracture entrance width, respectively. The D90 of the supplementary flaky materials, e.g., mica, should be slightly less than the fracture entrance width. The results of this laboratory study can provide guidance for selecting LCM size for effective fracture sealing and improved wellbore strengthening performance.

INTRODUCTION
During the drilling process, lost circulation happens when a lot of drilling fluid leaks into the formation. Lost circulation can result in the drilling fluid's depletion and prolong the drilling cycle. Improper management of lost circulation may also lead to complex situations, such as wellbore instability, blowouts, and stuck pipes, ultimately resulting in catastrophic engineering accidents. The lost circulation rate is estimated to account for approximately 20% to 25% of the total number of drilled wells. The annual cost of well plugging can reach $4 billion USD.
In North America (the United States and Canada), the percentage of drilled wells that experience severe lost circulation in carbonate oil and gas reservoirs, shale oil and gas reservoirs, and other formations amounts to about 40% of the total. In the Middle East, the wells that experience severe lost circulation during the drilling of carbonate-fractured oil reservoirs account for more than 30% of the total, with the time loss due to lost circulation exceeding 50%.