bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sedimentary Characters and Flow Transitions of Reworked Carbonates: A Case Study of Cenomanian-Turonian Reworked Sediments in the Eastern Abu Dhabi, UAE
Authors: Shimomura Takahiro , Yamanaka Motoyoshi 
Published: October 2022

Abstract
Reworked carbonate caused by the major erosional event of the "Turonian Unconformity" is considered to be distributed around the eastern part of Abu Dhabi, UAE. During 2021-2022, new wells were drilled in a prospective area where the reworked carbonate was deposited. By using the new wells data (wireline logs and cores) and pre-existing wells data, we considered lateral changes in sedimentary character and flow transitions of the reworked carbonate.
We conducted a well-well correlation, based on the wireline logs (GR, Neutron, Density, Resistivity and Sonic) of a total of 5 wells which were drilled in the prospective area. To understand the spaciotemporal changes of the reworked carbonate facies and properties, we conducted core observation and description, and routine core analysis (porosity and permeability) for the new wells.
In addition, based on the distribution and flow direction of this reworked deposit, we considered the changes of flow regime towards the flow direction.
The result of the well-well correlation and seismic interpretation suggests that the wells penetrated the same reworked carbonate body. We can recognize the variety of grain size, sorting, sedimentary structure, and a degree of the bioturbation between the wells: poorly sorted coarse-grained to pebbly carbonate is dominant around the depositional up-dip side, and sharp based well-sorted grainstone with sedimentary structures (grading and lamination) is dominant around the depositional down-dip side, with bioturbation being more intense especially at the upper part of these grading beds. These sedimentary characters suggest that the flow regime changed towards the flow direction: dense flow at the depositional up-dip side and dilute flow at the down-dip side. In addition, several grading beds in the same indicate that the flow repeated several times.
Routine core analysis and log calculation (porosity and permeability) results suggest that the sediments in a middle body of the reworked sediments has better reservoir properties.
There is remaining exploration potential for this new play concept (reworked carbonate reservoir) around Abu Dhabi. In this time, we drilled new wells to confirm this new play concept, and we suppose that the knowledge of this study may have a big impact to the future exploration.
Integration of Computed Tomography Scanning and Nuclear Magnetic Resonance Results with Conventional Laboratory Test Data for Effective Reservoir Characterization
Authors: Shvalyuk Elizaveta , Tchistiakov Alexei , Spasennykh Mikhail 
Published: October 2022

Abstract
The paper suggests a new laboratory tests workflow, aimed at reservoir characterization and rock typing of a polimineral clastic formation, based on microstructural characteristics. The proposed approach is accompanied by a comparative study of various laboratory techniques, including CT, NMR, MICP, centrifuging, and thin section analysis. The methodology for combining quantitative porous medium characteristics, derived from these multi-scale tests is also provided.
The developed laboratory test program includes porosity and permeability measurements, capillary pressure, electrical resistivity, NMR and CT-scanning tests. For initial differentiation of samples based on porosity, permeability and irreducible water saturation, we applied methods of flow zone indicator (FZI) and Winland R35. Afterwards, we performed joint interpretation of FZI with the results of centrifuging, resistivity, NMR and CT-scanning tests. Finally, for the most representative samples from the rock types, defined at previous steps, we performed X-ray fluorescence spectroscopy, XRD, MICP and thin section analyses.
In our study, we applied FZI, calculated as a function of irreducible water and porosity. Compared to conventional FZI, derived from porosity and permeability, our approach enabled more reliable rock typing in both sandstones and low-permeable siltstones.
CT tests showed that within the distinguished 4 rock types grain and pore sizes increase from the 1st to the 4th rock types. CT-scanning and X-ray fluorescence spectroscopy detected presence of pyrite in all samples. Siltstones contain more pyrite than sandstones that reflects deeper marine and consequently more anoxic depositional environment.
The obtained NMR T2-spectra appeared to be effected by both porous medium and mineralogical composition. Pyrite inclusions caused shifting of the T2-spectra to lower values, while carbonate presence – to higher ones. Therefore, since NMR signal is effected by multiple factors, applying of a single T2cutoff value for reservoir characterization and rock typing can lead to ambiguous interpretation.
The proposed algorithm for combining quantitative parameters of the porous medium allowed integration of pore size distributions, derived from CT and capillary tests. This enabled characterization of the whole range of pore sizes covered only partly by the different methods. The resulted pore size distribution enabled calibrating NMR Т2 spectra and defining individual surface relaxivity values for each rock type.
The selected set of techniques allowed confident differentiation and characterization of the rock samples based on multiple parameters, which were interpreted in relationship with each other. Moreover, the developed methodology was verified by applying additional laboratory tests, which confirmed the results of the proposed rock typing and reservoir characterization.
Using Machine Learning to Capture High-Permeability Streaks in Reservoir Models
Authors: Singh Manish Kumar , Parra Humberto , El Jundi Obeida , Ben Jeddou Houcine , Kada Kloucha Chakib , Mustapha Hussein 
Published: October 2022

Abstract
Permeability modelling remains a major challenge in the reservoir modelling exercise. The main reason for this is the limited availability of measured input data and the effect of different geological processes on reservoir permeability. This leads to nonrepresentation of high-permeability streaks in the model. In this paper, we present a machine-learning (ML) driven approach that captures the permeability variation in the reservoir using available input data.
In ML, clustering is an unsupervised approach aimed at automatically grouping data with similar properties. We use several clustering techniques to automatically identify high-permeability data points by dividing data into groups, also known as clusters, and then choosing the cluster with the maximum permeability and assigning it a new rock type. For each rock type, we fit and evaluate many ML regression models, and show their outperformance over traditional fitting approaches. Porosity and several openhole log properties are used as input for the regression models. By fixing porosity but varying the other properties, the variability of permeability values is predicted.
Clustering, using ‘K-Means’ ML algorithm, resulted in an efficient approach of automated high permeability identification. Several ML models were trained and evaluated, and the models with the minimum error scores, namely mean square error (MSE) and R Squared (R2), were chosen for further predictions. Random Forest was within the top models for a variety of rock types. In general, complex curve fitting using ML outperformed traditional fitting approaches (i.e., straight line fitting) and demonstrated high potential for accurate, automated, high-permeability identification and integration. The predicted permeability has been calibrated with well test permeability data.
CO2 Plume Detection Using Ras, Temperature and Noise Tools in A CO2 WAG Reservoir
Authors: Igogo Arit , Hutajulu Astia , Mohamed Sallam Yassin Farouk , Khan Sara Hasrat , Bhushan Yatindra , Al Ali Mona Yousif , AlSeiari Reem Ali Mabkhout , Aidroos Alwahedi Mohamed Abdulhameed , Al Hammadi Shareefa Ahmed , Al Teneji Aamna 
Published: October 2022

Abstract
In alignment with most company's vision to reduce greenhouse effects by expanding CO2 carbon capture and utilization for oil fields, CO2 gas is injected into the reservoir to enhance oil displacement and maintain reservoir pressure. Since CO2 gas is miscible in the oil, the gas flood front is not piston-like; the gas is slowly absorbed by the oil changing the oil properties. Detection of the CO2 plume is necessary to monitor CO2/ injected water/ oil distribution (at and away from the well) and to track the effectiveness of the complicated CO2 WAG injection process in terms of improved sweep efficiency.
Monitoring CO2 flood front movement requires a logging measurement that can distinguish oil from CO2 in the formation. This measurement must have a sufficiently large dynamic range for the change from no CO2 to a high CO2 saturation to be distinguished within measurement error. This paper highlights the utilization and integration of Reservoir Analysis System (RAS) and Noise tools in CO2 plume detection. It also highlights some of the limitations of the RAS tool in high water transition zone in CO2 WAG environment.
As the oil is push away from the injection well, the flood front will be characterized by oil having varying amounts of miscible CO2 gas dissolved in it. The rate and composition of the injection gas determines how much of the oil that will expand. The density of the oil may not change much (since the oil density is close to the CO2 gas density) but the hydrogen density of the oil will decrease considerably as is the case for CO2. Another factor that controls the CO2 plume movement is the stratigraphy of the heterogeneous carbonate reservoir – where the coarsening upwards trend of the facies associations of High Stand Systems Tract (HST) coupled with pervasive cementation, creates non-uniform movement of CO2 plume vertically and spatially.
Logging results shows Neutron porosity (PHIRN) and PNC near/far capture ratio are the preferred log measurement curves because they have the most sensitivity to the large decrease in hydrogen index when CO2 replaces oil or is dissolve in oil. Other curves like Ratio of Near to Long at Burst (RLNB), Long Inelastic Rate Sigma (LIRS), temperature and noise logs also play significant roles in CO2 plume indications.
The outcome of this study has helped understand the vertical and lateral extent of the CO2 WAG flood front, estimate saturations, evaluate the well integrity, and locate un-swept zones. Additionally, RAS data is hard data used as calibration (blind test) to check the robustness of the dynamic model.
The World's Largest Contiguous Onshore and Offshore 3D Seismic Survey is Getting Even Larger
Authors: Al Mesaabi Saif Ali , Cambois Guillaume Marie , Cowell James , Arnold David , Boukhanfra Mohamed Fawzi , Al Karbi Saeed Hamad , Mahgoub Mohamed 
Published: October 2022

Abstract
In late 2018 ADNOC launched the world's largest continuous seismic survey to cover the entire Abu Dhabi Emirate, onshore and offshore, with high-resolution and high-fold 3D seismic. In 2021 ADNOC started acquiring the remaining transition zone (TZ) area bridging the divide between land and sea. The onshore and offshore survey designs could not be repeated for the TZ survey design due to environmental difficulties and associated costs. Instead, we adopted a novel approach using uneven source spacing to secure some far-offset coverage but not as dense as near-offset coverage.
TZ acquisition started in July 2021 and is close to 35% complete at time of writing. The crew has performed according to plan and has met its rigorous HSE objectives while operating in very sensitive areas. The full TZ survey is smaller than the onshore and offshore areas, but it is without a doubt the most difficult part of this entire project. We expect completion in 2024.
This transition zone survey uses an innovative design and the first offshore nodes with MEMS sensors. It is also the largest nodal TZ operation ever conducted.
Delivered the First Maximum Reservoir Contact Well in Giant Mature Field Using Source-Less LWD Technology; Case Study, Onshore Abu Dhabi
Authors: Holmquist Andrei , Thakur Parmanand , Barragan Ernesto , Bazuhair Mohamed , Pandey Vikram Kumar , Singhal Sangeeta , Nazarbayev Nurbek , Fares Wael , Ghobashy Ahmed , Mubeen Muhammad 
Published: October 2022

Abstract
This case study well is in a mature onshore field, which has been under production for a long time (started in 1970) resulting in depletion of some of the reservoir units presenting challenges for optimizing drilling performance and managing risks associated with stuck-pipe incidents. Additional challenges are minimized surface footprint, 100% reservoir contact in thin targets and acquisition of accurate petrophysical data for formation evaluation. A detailed pre-well study was conducted utilizing historical field and nearby wells’ data in the planning phase with close collaboration in a multi-disciplinary team including well and Bottom Hole Assembly (BHA) design and pre-well modeling for geosteering and LWD tool string configuration taking into account the elimination of radioactive chemical sources. The pre-well study has concluded that the azimuthal deep propagation resistivity image is going to provide proactive geosteering solution to identify the approach to both top and bottom boundaries. The BHA has also included rotary steerable system (RSS) along with optimized Logging While Drilling technologies (LWD) which has included, high-resolution micro resistivity imaging, Laterolog resistivity, nuclear magnetic resonance (NMR), sonic caliper and near-bit gamma ray. Continuous real-time monitoring provided drilling performance monitoring and analysis as well as facilitating geosteering services. The 8,356 feet horizontal section was effectively geosteered with 100% reservoir contact tapping into two thin reservoir sub-layers. Real-time azimuthal deep propagation resistivity image/curves were used to geosteer the well trajectory precisely within target zones and provided 4-5 feet TVD detection to bed boundaries. Also, high-resolution microresistivity images, dip picks and near-bit azimuthal gamma ray helped in maintaining the well-bore attitude parallel to the stratigraphy within each sub-layer. This data facilitated a smooth transition from one sub-layer to the next with minimum borehole tortuosity aided by the push the-bit RSS and at-bit-inclination measurements.
In addition, NMR provided real-time porosity and permeability measurements assisting in well placement and enhancing reservoir understanding as well as optimizing future well planning workflows. This paper presents a step change from the traditional field development drilling techniques in terms of horizontal length. Similar well designs are currently being implemented in an effort to benchmark drilling, well placement and petrophysical data gathering requirements for future development drilling in order to maximize asset value.
Machine Learning Applications of 4D Seismic in Carbonate: Case Study Offshore Abu Dhabi
Authors: Mahgoub Mohamed Abdelghany , Bashir Yasir , Berry Andy Anderson 
Published: October 2022

Abstract
Seismic 4D analysis is a model for integrating different disciplines in the oil and gas industry, such as seismic, petrophysics, reservoir engineering, and production engineering. Two 3D seismic surveys were conducted in the studied area with low repeatability of the recordings: the baseline survey in 1994 and the monitoring survey in 2014. A full 4D seismic co-processing of the baseline and monitor surveys was performed for both surveys starting with the field tapes. The 4D seismic co-processing improved poor seismic acquisition repeatability and 4D seismic attributes such as NRMS and predictability showed that. 4D time-trace shift was also performed, using the baseline survey as a reference to measure the time shifts between the baseline survey and the monitor survey at 20-year intervals. Dynamic 4D trace warping was followed by seismic 4D inversion to compare the 4D difference in the seismic inverted data with the difference in seismic amplitude. The seismic inversion helped overcome noise, multiple contamination, and differences in dynamic amplitude range between the baseline and seismic monitoring measurements. Applications of machine learning in the geosciences are growing rapidly in both processing and seismic interpretation. We then examined the relationship between well logs and seismic volumes by predicting a volume of log properties at the well locations of the seismic volume. In this method, we computed a possibly nonlinear operator that can predict well logs based on the properties of the adjacent seismic data. We then tested the Deep Forward Neural Network (DFNN) on six wells to adequately train and validate the machine learning approach using baseline seismic inversion data and monitoring data. The objective of trying such a supervised machine learning approach was to predict the density and porosity of both the baseline seismic data and the monitoring seismic data to verify the accuracy of the 4D seismic inversion.
Characterization of Late Aptian Upper Shuaiba Sequences in Western Abu Dhabi Based on Newly Acquired 3D Seismic Data
Authors: Nag Arnab , Tokhi Barnali 
Published: October 2022

Abstract
The Shuaiba Formation, one of the primary reservoirs of Early Cretaceous Petroleum System, has been an important exploration target in onshore Abu Dhabi due to its excellent reservoir quality specifically along the platform margin. Initially the Bab Basin carbonate development was slow but increased during lowstand sequences of Upper Shuaiba which is also known as Shuaiba Sequence 5 (Strohmenger et al., 2010). The Upper Shuaiba is distinguished from Lower Shuaiba by the presence of clay, high frequency and low amplitude progradational sequences. This study is going to describe the nature of the carbonate development within these Upper Shuaiba sequences in western Abu Dhabi.
Newly acquired 3D seismic data, existing well data and regional information have been utilized for seismic interpretation and litho-facies analysis to characterize Shuaiba Sequence 5. These interpretations were then linked to the depositional processes which generated the geometries and distribution of facies.
Based on well correlations within the study area, the Bab shale is roughly 100ft near the Shuaiba platform. It forms a wedge on the slope of the platform and gradually thins out to ~17ft towards the north. The deposition of the shale is attributed to influx of terrigenous sediments during the lowstand, which were later distributed by longshore currents as inferred from seismic attribute maps. The occurrence of carbonate above the Bab shale has been related to the cessation of siliciclastic input, which created a suitable environment for a carbonate factory. Shallow water depth and frequent sea level fluctuations created several thin clinoform sequences. These fourth order sequences are observed to have an average thickness of ~20ms and are often restricted within two seismic reflectors. The orientation of the clinoforms is NW-SE. These are categorized into three sets as reported by previous authors (Pierson et al., 2010 & Whitcomb et al., 2021).
The clinoforms have higher amplitude in the top set, which gets dimmer in the bottomset. Lithofacies from core data show the presence of thin beds of floatstone to packstone at the topset, which could form potential reservoir subject to better permeability development. The overlying Nahr Umr shale is the regional seal. The clinoform sets are located over a NE-SW oriented structural trend and may form subtle traps due to updip facies change within the clinoforms. Similar type of strati-structural trapping mechanism could be found along the strike of these clinoform sequences and may become potential prospects for hydrocarbon exploration in western Abu Dhabi.
Innovative Solutions to Subsurface Challenges in Deep Hard Rock High Temperature Slim Wells
Authors: Wahshi Khalifa Omair , Thomas Boris Jean , Khaldi Saud Ali , Haji Younis Said , Salehi Yasir Mohammed , Yuan Roger Shihche , Mahrooqi Ali Khalfan , Harthy Khalid Nasser , Habsi Fahad Said 
Published: October 2022

Abstract
In this paper we present the challenges faced in one of PDO's onshore a deep (5200 mTVD) field. Among these challenges were hardness of the rocks, 40 ksi and a high temperature of 155ºC. Further, well bore instability, tectonic stresses and depletion. The time consumed to overcome these subsurface challenges with conventional drilling methods was affecting the economic attractiveness of some of the wells. A multi-disciplinary taskforce was established with the remit to improve overall well economics by overcoming field challenges and by turning some of the challenges into opportunities.
The working group identified opportunities across several themes that were deemed to have the highest impact on the well economics, well design and materials selections and new technologies. The introduction of a new design concept of (Fast Degradation Brine) in the annulus allowed a reduction of the brine weight after cementing the completion. This change enabled passing specific casing design burst loads associated with the reduction of the 7" liner weight from 35 to 29 ppf. This allowed drilling larger hole sizes of 6" and 6 1/8" instead of 5 7/8". H2S fugacity concept was used instead of the conventional partial pressure concept to evaluate the sour severity of the materials. In new technologies, Motorised Reamer Shoe (MSR) drive system, was piloted for the first time in PDO's cemented completion to enable re-drilling and reaming ledges and hole closure caused by tectonic stresses during the completion run. A Polymer Borate System (PBS) plug has proven to be an effective new technology, used as lost circulation material for dealing with severe losses in PDO.
Through introduction of new well design concepts, new technologies and new ways of working we managed to: - Safeguard reserves and enable full access to target reservoirs by overcoming drilling challenges through improvements in the well design. - Realise a 40%-well delivery time reduction, coupled with a significant reduction in NPT. - 30%-reduction in average well cost. - Realise cost saving of 2.9% through well design optimisations. We managed to safeguard production which would be lost in case of short landing the completion. - Replicate MSR technology on planned side-tracks in PDO's wells, and we are planning to apply this technology in horizontal wells. The technology will also be an enabler to further slim down well designs in other fields. - Put in place a replication plan for applying the H2S fugacity concept wherever applicable. The well design concepts and new technologies mentioned above are novel or new to PDO.