bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving Class G Cement Carbonation Resistance Using Nanoclay Particles for Geologic Carbon Sequestration Applications
Authors: Mahmoud Ahmed Abdulhamid , Elkatatny Salaheldin , Mahmoud Mohamed 
Published: November 2018

Abstract
The hydrated products of Portland cement drastically change after exposure to CO2 rich brine, compromising the cement physical properties, especially, the compressive strength. This phenomenon is known as strength retrogression which occurs when the Ca/Si ratio of the cement hydrated products is close to 2.0.
Previous studies showed that the use of silica flour enhances the cement resistance to the strength retrogression because of the formation of long silica chains. In this work, the influence of modified montmorillonite nanoclay (NC) particles which are nanoparticles of layered mineral silicates, on the strength retrogression resistance under carbonation process was evaluated.
Two cement slurries with 0% and 1.0% NC were prepared and tested for the change in their different properties of compressive and tensile strengths, porosity and permeability with the carbonation time for 20 days of reaction into 0.5 M NaCl solution at 95°C and 10 MPa. After 7 days of preparation, the properties of the samples were tested, then samples were immersed into the CO2 saturated brine, after 5, 10, 20 days of reaction some samples represent each specimen were collected and tested for the same properties mentioned earlier.
The results revealed that incorporating the NC particles enable to decrease the decline in the compressive strength from 12.62% to 2.13%, and the tensile strength reduction reduced from 8.21% for the base samples to 1.72% for the NC-based samples after 20 days of reaction. The porosity decline was also reduced to be 6.49% compared with 17.58% for the base samples (i.e. without NC), while the permeability reduction changed from 19.51% for the base cement to 8.70% for the NC-based cement.
The permeability reduction, as well as the chemistry of the NC particles which enables them to accelerate the hydration process, are the main mechanisms which enhance the cement resistance to the carbonation.
Combat Unpredictable Losses during Casing Cementation in a Compartmentalized Structure, Nong Yao Field, Gulf of Thailand
Authors: Tongkum Tossapol , McManus Ian , Abu-Jafar Feras , Thanasarnpisut Viraphon , Vargas Bermea Jorge Andres , Kaewpraphan Kingkarn , Wuttikamonchai Pakaporn 
Published: November 2018

Abstract
Lost circulation, while cementing, compromises the objectives of cementing an oil or gas well. Losses encountered during cementingcan cause a weak casing shoe, poor zonal isolation, early water breakthrough for an oil producer, as well as increasing the possibility of costly intervention work. Execution of primary cementing operations can be subject to unplanned circumstances; when a slurry is being pumped or displaced and losses are recorded, in most circumstances the operation switches to damage limitation by slowing down the pumping rate.
The Nong Yao field (Figure 1)is characterized with an interbedded unconsolidated sand / clay lithology within a highly compartmentalized structure, and as such, well construction operations have encountered unpredictable lost circulation during 7-in. casing cementation (but rarely during the drilling phase). Over 60% of the wells recorded losses during 7-in. cementing; it became evident that a proper loss mitigation plan was necessary to combat lost circulation and improve the probability of successful cementation execution. Although the primary objective is to achieve zonal isolation, equally as important for Nong Yao drilling operations are provision of annulus barriers, slurry compressive strength development, "gas tight" qualities, optimum slurry Thickening Time (TT) to allow for safe batch drilling operations.
Figure 1 Nong Yao field localization
To overcome the challenges, an "out of the box" approach was essentialwhich yielded two innovative solutions: i) a combination of advanced lightweight cementwith engineered reticular fiber (ERF) systems, which allows safer placement of the cement in the annulus, while minimizing the potential losses; ii) a combination of several lost circulation materials (LCM) in an optimized ratio in an engineered fiber-basedlost circulation weighted spacer package, which has an additional function of preventing and mitigating risk of losses during cementing. This approach was intended to reinforce the loss zones by using the four-step methodology; disperse, bridge, plug and sustain. The severity of lost circulation while cementing was significantly reduced without compromising the abovementioned objectives.
This paper will discuss the successful implementation of the new approach solution by integrating different technologies to overcome the challenges of unpredictable losses during cementation. Two case histories from numerous jobs will be discussed with cement post-job evaluation via playback simulations and standard cement bond logs, which validates that the new approach increases the chance of achieving well objectives. Consequently, the risk of unplanned (UNP) operations and costly remedial operations are substantially reduced.
Measurement of Temperature in Deep Reservoir Zones by Mobile Sensor Devices
Authors: Li Bodong , Gooneratne Chinthaka P. , Bassam Mohammed K. , Zhan Guodong 
Published: November 2018

Abstract
The second generation temperature microchips were field tested in a deep reservoir section of a well. Out of 140 microchips deployed, a total of 50 microchips with memories were recovered from the well. This was accomplished even with the well experiencing partial lost circulation during the operations. The recorded temperature profile revealed the temperature distribution at different depths and positions inside the drill string/casing. Conventional methods of accessing downhole information would risk the potential of stuck pipe, and associated non-productive time due to frequent loss circulation situations in such wells. The obtained downhole dynamic temperature can be used to optimize the cement slurry and tailor thermal activated loss circulation materials in the current as well as future wells.
Evaluation of Rudist Depositional Environment using X-ray CT Scan Late Cretaceous Cenomanian in Offshore Abu Dhabi
Authors: Yamanaka Motoyoshi , Nanjo Takashi , Taniwaki Takashi 
Published: November 2018

Abstract
Rudists are a group of strange shaped marine bivalves lived in the Tethys Ocean from the Late Jurassic to the Late Cretaceous. The rudist-bearing carbonates form a lot of oil and gas reservoirs in the Middle East. Therefore, the taxonomy, morphology, paleo-ecology of rudists is important to understand the rudist-bearing carbonate reservoir features for oil exploration and development. However, it is difficult to understand these characters of rudists because we can't collect whole rudist samples from the underground oil and gas reservoirs through core sample. X-ray CT is a useful method to visualize three dimensional rudist images with non-destruction of the core. Hence, X-ray CT has a potential to obtain the information of the taxonomy, morphology and depositional environment of rudists from core information. We conducted the X-ray CT scan to the reservoir formation (Formation A) of the Cenomanian age using core slab samples of Well #A and Well #B in the Abu Dhabi oil field. The some rudist fossils were observed on the cutting surfaces of slab cores in the both wells. However, the three dimensional morphology of rudists were not identified inside of the slab core. On the CT images, some autochthonous rudists were identified and it made the colony in Well #A. This rudist is standing position and suggesting original position of depositional environment from Cestari and Sartorio (1995). We demonstrated to be able to obtain the morphology from the slab cores with non-destruction using X-ray CT scan in this paper. Now we are challenging to make the high resolution 3D image modeling of rudists based on this X-ray CT result. This paper is summarized that usage method of the X-ray CT result to understand taxonomy/morphology and depositional environment from three dimensional position of rudists In addition, in the future technique, this paper suggested that combined technique between X-ray CT of core and FMI may reveal more comprehensive depositional setting such as direction of paleo ocean current and paleo wind in the future.
Impact of Seismic Acquisition and Processing Techniques in Challenging Subsurface Imaging; Block G11/48, Gulf of Thailand
Authors: Kaewprain Phansakorn 
Published: November 2018

Abstract
The availability of high quality seismic data is of critical importance in trying to unravel the complexities of subsurface geology. This paper illustrates how proper selection of seismic acquisition parameters and data processing techniques can successfully overcome geological difficulties and minimize uncertainties when exploring for hydrocarbons in the northern part of Block G11/48, Gulf of Thailand, without compromising safety and cost efficiency.
Fluvial and fluvio-deltaic sediments of early to mid Miocene age in low relief faulted structural traps constitute the most common hydrocarbon habitat in the area of investigation. Amplitude support in identifying potential targets is also proven by nearby discoveries. To fully evaluate the exploration potential of this area, a 3D seismic acquisition campaign was successfully carried out using a high-end seismic vessel and without HSSE incidents.
The Nong Nuch dataset was acquired using a 10 deep-flat towed 5.1 km streamer configuration with triple sources to increase cross-line resolution and reduce operational time. This long streamer length relative to the target depth provides necessary information to Full Waveform Inversion and Q-tomography in order to correct push-down effects in broadband anisotropic Pre-stack Depth migration. The dataset also helps to obtain high accuracy velocity model, de-multiple and quantitative interpretation. This acquisition and processing approach significantly improved the ability to image thin reservoirs and correct push-down effects and energy absorption due to gas clouds or unconsolidated sea floor channels.
The large streamer spread and deep tow did not create any major problems throughout the acquisition. The implementation of broadband acquisition and leading edge processing techniques resulted in good signal to noise ratio as well as high vertical and horizontal resolution with minimal acquisition footprint. In addition, long offset data acquisition contributes to successful attenuation of short and long period multiples. Channel-like features and fault plane reflections are very clearly imaged in the dataset, helping to better understand of the depositional environment and structural setting of the area. Severe push-down and abnormal amplitude absorption effects were significantly corrected and compensated by building a high resolution, Full Waveform Inversion (FWI) derived velocity model as well as application of reflection tomography and Q-tomography techniques. Thus, definition of potential traps beneath gas clouds has significantly improved.
Boosting Rock Facies Prediction: Weighted Ensemble of Machine Learning Classifiers
Authors: Shashank Sharad , Mahapatra Mahabir Prasad 
Published: November 2018

Abstract
Modern day challenges in geosciences are "multidimensional," and as the amount of E&P data has proliferated in recent decades, machine learning techniques to handle this data have proliferated as well. However, different algorithms may outperform each other for different data instances. Exploiting this characteristic, we propose a workflow for boosting the prediction accuracy using a weighted ensemble of multiple machine learning classification algorithms to solve the classical problem of supervised rock-facies classification from well logs.
Instead of trying to identify the perfect classifier for rock facies classification, we propose a weighted ensemble of three base level classifiers: extremely randomized trees, support vector machines, and gradient boosting algorithms for obtaining a more generalized predictor. The hyperparameters for each model are optimized using grid search, cross-validation and learning curve assessment, thus tuning the classifiers while reducing overfitting. The "best model" predictions from each classifier are then fed to a weighted-majority rule classifier for obtaining more generalized facies predictions by accentuating each model where it performs best and discrediting a model at instances of poor performances.
This approach applies a robust workflow to address the problem of identifying the interrelationship of wireline logs and core cuttings, a crucial step for predicting reservoir facies in new wells. A family of popular machine learning algorithms is trained on five well logs and two geologic indicator logs for classifying the log samples into nine discrete facies. We discuss the process for evaluating and thus ranking these algorithms on blind data. Because core data are often limited, we also propose an efficient solution to reduce the inherent bias and variance properties of these classifiers. High bias is reduced by hyperparameter tuning on cross-validation sets, and high variance is checked by plotting learning curves of training and test scores as a function of training set sizes. Extremely randomized trees, support vector machines, and gradient boosting have shown low bias, low variance, and highly correlated test predictions, which made them the perfect candidates to be fed into the second level weighted voting classifier. The voting classifier combines these similar and conceptually different classification models for facies classification via majority voting, thus balancing their individual weaknesses. The weighted classifier has been shown to have a higher prediction F1 score than individual classifiers.
This advanced workflow will be beneficial to geoscientists who must routinely solve well data classification problems. In addition to boosting facies prediction in new wells, this novel approach disseminates important machine learning concepts transferrable to other supervised classification and regression problems in exploration workflows.
Mitigating Lost Circulations for Drilling Losses-Prone Wellbores by Accurately Predicting the Fracture Gradient with an Integrated Geomechanics Approach
Authors: Fang Zhi , On Chee Khong , Zamikhan Norshah , Borah Jahnabi , Spanninga Christoffer 
Published: November 2018

Abstract
Lost circulation is one if the top concerns of drilling nearly 50 wells penetrating heavily depleted shallow reservoirs in a recent drilling campaign. Three of the first 5 wells observed losses with the fifth losing a hole section during drilling. A fracture gradient (FG) model developed by an integrated geomechanics approach assessed those five wells and indicated that the equivalent circulation density (ECD) was higher than the predicted FGs in the three losses wells but lower than the FGs in the two non-losses wells. The FG model guided the drilling team successfully re-drilled the lost section of the fifth well and accomplished another two wells by controlling the ECD under the predicted FGs. The sixth well had a predicted FG lower than the ECDs used in the fourth and fifth wells and could have encountered massive losses or losing a section again without the FG model. The FG model was further promoted to minimize the lost circulation risks by predicting the FG of additional 14 wells with 12 having been successfully drilled. It has saved about USD 500k per well on average with mitigating the lost circulation risks for those losses-prone wells by the integrated geomechanics approach. This approach is extended to assist managing the drilling safety and cost savings for remaining wells.
Viable Solution to Drill Through Induced Losses in Limestone Formation in Extended-Reach Wells in UAE Offshore
Authors: Doutoum Mahamat Habib Abdelkerim , Musabbeh Al Azizi Badr , Bermudez Alvarado Romulo Francisco , Eduardo Navas Luis , Popatrao Salve Bhushan , Akyabi Khalid , Kustanto Sigit , Kapoor Saurabh , Jain Bipin , El Hassan Azza , Rahhal Gilbert 
Published: November 2018

Abstract
Lost circulation is a widespread problem in many formations in the United Arab Emirates, including Shallow Unconsolidated, Shallow Vuguler and Limestone. To minimize losses during drilling and cementing, several types of lost circulation solutions such as bridging agents and surface-mixed and downhole-mixed solutions have been used. Still, operators lose huge volumes of mud and cement slurry and expensive rig time. Consequently, many wells also require remedial operations, which can compromise well integrity.
Loss-zone diagnosis and characterization helped to tailor the loss-circulation control solution for different requirements. Losses can occur due to unconsolidated formation (surface holes) or induced and natural fractures. Typical loss rates can vary between 150 to over 700 bbl/hr, particularly while drilling the 16-in. and 12 ¼-in. openhole sections. Thus, total losses in shallow vuguler formation require a different treatment than induced losses in shallow unconsolidated or limestone formation. Induced losses in limestone while drilling prevented increase in mud weights required to drill deeper reactive shale formation. A composite fiber-based system based on a novel four-step methodology was designed using advanced software analysis. Prior to the field trial a complete lab-scale and yard-scale testing was done to confirm superior effectiveness.
In one of the pilot wells, multiple leakoff tests (LOTs) were performed in the Limestone formation to verify the minimum stress (1.40 SG), which did not change with subsequent LOTs. The formation was then treated with the reinforced composite mat based system, and the following formation LOT showed integrity buildup to 1.51 SG. It proved to be an easy to apply solution that can be mixed and pumped through a qualified bottomhole assembly (BHA).
Zone and mechanism specific lost circulation control solutions are most effective in reducing nonproductive time (NPT). It was also demonstrated that fiber-based solutions work well for controlling losses and formation strengthening. The engineered composite fiber-blend system exhibits improved performance and robustness in terms of curing losses and even improves formation integrity.
Fit-For-Service Qualification of Existing 13Cr Tubulars in Mildly Sour Wells Based on Thermodynamic Approach
Authors: Kumar Amit , Srivastava Manish , Al Shehhi Ali , Al Daghar Tariq , Abdulhai Walid , Gan Chee-Lam 
Published: November 2018

Abstract
Most of the existing wells in a giant oil offshore field in Abu Dhabi are equipped with L80-13Cr corrosion resistant alloy (CRA) tubulars to provide protection from CO2 corrosion due to sweet nature of reservoir. Recently, some of the wells are showing a presence of mild H2S due to unexpected reservoir souring or other geological changes. The presence of H2S in production fluids raises concerns about sulfide-stress-cracking (SSC) of L80-13Cr. As L80-13Cr CRA has been known to have limited SSC resistance, it is important to understand the maximum acceptable limit of H2S in production fluids for safe operation.
Industry standards such as ISO15156/ NACE MR0175 and NORSOK-M-001 recommend safe acceptable limits of H2S for 13Cr tubular materials based on the partial pressure of H2S. However, these approaches do not take into account the effect of temperature, or non-ideal gas behavior of H2S at high pressure. Pressure, temperature, salinity and pH in the wellbore impact the solubility and chemical behavior of H2S in the water phase which defines the corrosive environment to which the material is exposed. Therefore, it is important to include non-ideal gas and solution behaviors in order to define the acceptable limit of H2S for fitness-for-service (FFS) material evaluations.
In this work the acceptable limit of H2S in the wellbore was determined using a combination of thermodynamic modeling and field corrosion data. A molecular thermodynamics approach was used to calculate pH and dissolved H2S levels in water along the production tubing length. Shut-in and production operation scenarios were simulated to identify the worst-case scenario using thermal modeling software. Furthermore, tubing inspections were conducted using a multi-finger caliper tool to identify any corrosion damage. All of this information was used to identify the acceptable limit for H2S in the wellbore. This approach to determining acceptable H2S limits will avoid unnecessary workovers and enables cost saving through continued use of existing materials. Furthermore, it supports the development of a corrosion monitoring plan, and FFS assessment of tubulars based on the wellbore environment.
How Broadband, High Dense, Full Azimuth & Point Source Point Receiver Acquisition Improves Seismic Interpretation in Onshore Abu Dhabi
Authors: Al-Naqbi Sheikha , Elila Abusaa , Vargas Jose , Mahgoub Mohamed 
Published: November 2018

Abstract
Acquiring seismic data with S4 (Single Source, Single Sensor) is proven technology and it has many advantages over the conventional source and receiver array acquisition type. The array has an intra array statics issue when deployed on large elevation variation such as sand dunes and attenuating higher frequencies as well. S4 with denser spatial sampling with smaller shotline and receiver line spacing could jointly with seismic data broader bandwidth to improve interpreting many seismic details such faults, fractures, tiny stratigraphic features resolution. A debate was raised locally about the value of acquiring seismic data with S4, if only for the sake of acquiring seismic data with shorter time duration compare to the too much equipment needed for array acquisition type that consumes longer time in general. Alternatively, S4 really bring a real value of information and producing an outstanding seismic volume for amenable interpretation with confidence that will lead to utilize the seismic data to help in optimizing the well trajectories placement.
This high density broadband 3D seismic acquired survey with fully sampled wave-field data has used the latest acquisition and imaging technologies, it has delivered critical information that can help to reduce drilling risks and to support future 4D reservoir monitoring which improved signal to noise ratio when compared with legacy dataset.
An advance seismic processing workflow is tailored to improve the final image quality, and to preserve the azimuthal amplitude variation with offset and azimuth, which in turn can lead to the derivation of intrinsic rock property attributes for better reservoir characterization. A multi azimuth Prestack depth migration approach resolved most of the effects of heterogeneities in the shallow part and in the velocity field, which sometimes can be misinterpreted as azimuthal anisotropy.
Reducing Horizontal Hole Size from 8.5 to 6.75 Reduces Unconventional Well Construction Cost by 25%
Authors: Schumacker Eric David , Vogelsberg Philip 
Published: November 2018

Abstract
Slim hole well design can reduce well construction cost through a reduction in steel, fluids, and disposal costs. In the industry, there has been a misconception that slim hole size possesses the tradeoff of slower ROP and less efficient fracture treatment. Improvements in downhole tools, drill strings, rig capability, and drilling fluid design have been implemented to improve ROP in slim holes. Completions designs were refined for slimmer holes to avoid any significant loss in stimulation effectiveness and maintain well value. Through systematic replication of learnings and designs across basins, slim hole well design has advanced. Slim hole well design (transition from 8.5" / 7.875" hole and 5.5" production casing to 6.75" hole and 5.5" / 4.5" production casing) can reduce Unconventional well cost by over 25% which reduces well unit development cost (UDC).