bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Carbonate Reservoir Characterization: A Case Study from a Supergiant Field in Southern of Iraq
Authors: Al-Ali Ali , Stephen Karl , Shams Asghar
Published: March 2019

The objective of this work is to characterize the porosity distribution and the types of carbonate facies in the Mishrif reservoir in the West Qurna/1 Oil Field using seismic inversion results, well log data, rock physics model and core data analysis. Identification of the pore system and the spatial distribution of lithology are keys for constructing Mishrif reservoir model, which have a great impact on the development of the most prolific reservoir in the field Mishrif reservoir.

Seismic inversion process is transforming of seismic response into a quantitative elastic properties of the reservoir rocks. It enables the modeling of porosity and lithology distribution in 3D space away from well control. In order to achieve the aim of the work, a step wise approach will be taken. First of all, the vertical distribution of porosity based on well log data and its relationship with elastic properties was undertaken. A model-based seismic inversion guided by rock physic analysis modeling was applied across the high resolution 3-D seismic data, and integrated with core data for validating at Mishrif intervals. The porosity volume was then generated over the entire West Qurna/1 field based on the linear-regression analysis.

The interpretation of seismically derived characterization in the Mishrif reservoir observed a different lateral distribution of acoustic impedance. The results were correlated with computed acoustic impedance log and core analysis data to classify lithofacies of the Mishrif interval. The resulting porosity volume was validated with well log data where good consistency was indicated. By slicing through the porosity volume, it shows a high porosity in many carbonate features with low acoustic impedance which reflect a good reservoir quality (grainstone tidal channel or the accumulation of corals and mounds facies). This observation implied that Mishrif zones displayed a wide range of porosity and lithology fluctuations due to the impact of depositional environment.

The workflow provided insight into the porosity distribution and quantification of its influence on dynamic reservoir behavior. The estimation of the porosity based on seismic data, can increase the reliability of reservoir characteristics through providing a more detailed of porosity distribution in interwell regions. Overall, this study will ultimately lead to improve the development plan of wells in terms of production performance, and economic value of the West Qurna/1 oil field and similar heterogeneous carbonate reservoirs.
Single Station Triaxial Seismic Event Detection, Direction Finding and Polarization Analysis
Authors: Greenhalgh Stewart , Al-Lehyani Ayman , Schmelzbach Cedric , Sollberger David
Published: March 2019

The bearing and elevation (azimuth and inclination) of a seismic event can be estimated directly from measurements at a single triaxial station. There are instances in which the angular resolution secured by triaxial polarization analysis is better than that obtained by beamforming with an extended scalar array. In these situations, one depends totally on understanding the inter-relationships between the triaxial records that make up a seismic wavetrain. There are many approaches to seismic direction finding (SDF). Monte-Carlo techniques of triaxial seismic direction finding seek to maximise signal power by examining the seismic wavefield in many rotated co-ordinate frames. There are variants on this approach, which entail null seeking in an inverse space. Instead of searching all possible directions for the one which best fits the polarization model of a single arrival, it is possible to carry out an eigen-decomposition of the (complex or real) covariance matrix formed from the three-component data. The eigenvector corresponding to the principal eigenvalue yields the polarization direction automatically, with significant savings in computational effort.

Numerical experiments undertaken for different levels of random noise superimposed on a pure mode signal show that there are no significant advantages in using the Monte-Carlo techniques over eigendecompsoition. Confidence measures of event detection may be obtained by examining eigenvalue ratios when using the eigendecompsoition method. A time-domain formulation (covariance or coherency matrix) is preferable to a frequency-domain formulation (cross-spectral matrix) when there are multiple transient events present. The analysis window should be as long as possible (at least half the dominant period of the signal) without causing separate events to interfere.

In practise, the direction-of-arrival estimates deteriorate with increasing levels of random noise, and are generally unacceptable for a SNR of less than 1. Special care is needed to avoid direction errors associated with systematic noise, such as sensor gain misalignment between channels, coupling variations between receiver components, velocity inhomogeneity and anisotropy, the free-surface effect, and multiple event interference.
A Casing Damage Prediction Method Based on Principal Component Analysis and Gradient Boosting Decision Tree Algorithm
Authors: Song Mengxin , Zhou Xiangguang
Published: March 2019

The examination and prevention of casing damage is an important work in oil and gas field development projects. Casing damage will directly influence the production of oil and gas, the effect of water injection and the life cycle of oil, gas and water well. With the number of casing damage wells increasing year by year in each oil field, inspections and precautions of casing damage status have become more and more important during development of the filed. With the development of big data technologies, we can predict the casing damage based on historical and real-time data, and optimize the maintenance intervals of casing.

In this paper, we proposed a casing damage prediction method based on principal component analysis (PCA) and gradient boosting decision tree (GBDT) algorithm. Building a three-nodes Spark big data platform, we tested our proposed method on a dataset in an oil-field in mid-east China. Firstly, based on data analysis and expertise, selected 10 parameters which affect the casing damage most, including casing outside diameter, wall thickness, perforation density etc. Secondly, using PCA to reduce the dimension of parameters. Thirdly, building the algorithm model of casing damage risk assessment by GBDT, training and optimizing the model parameters. Fourthly, using the proposed model for casing damage prediction.

Using precision and AUC(Area Under ROC Curve) to evaluate the proposed method, and compared with traditional methods, including decision tree, logistic regression and Naïve Bayes, the experiment results show that compared with traditional methods, the proposed method gain 86.3% precision and AUC is 1, both higher than traditional methods, which means it has better prediction precision and performance. The proposed method also can apply to predict the probability of a normal well becoming a casing damage well, and finally can provide the decision support for on-site operations. The proposed method using data-driven idea to provide the decision support for oilfield operations, and lay the foundation for the construction of intelligence oilfield.
Influence of Surface Choke on Water Cut and Flow Profile in Horizontal Wellbores Intersecting Fractures and Super-Ks
Authors: Al Sulaiman Ahmed A. , Dimitrios Krinis , Al Shehri Dhafer
Published: March 2019

The surface choke has been utilized in the oil industry to control withdrawal rates per well and to optimize production especially after water breakthrough. However, as found out from this study, applying undue restrictions in horizontal wellbores intersecting high permeability features can have an adverse impact on well performance and unnecessarily lock oil potential.

This paper investigates the effect of surface choke on water cut and flow contribution along horizontal wellbores that encountered natural fractures and high permeability streaks (Super-Ks). The study considered different down-hole completions; open-hole and cased-hole. The investigation was carried out using Multi Phase Flow Meter (MPFM) measurements at different choke sizes in addition to production logs (FSI), wellbore simulation modeling, and real-time data. Instant data monitoring was instrumental in insuring stabilization of sub-surface static pressure while performing many rate tests at different choke sizes. Moreover, it flagged the role of rate stabilization on water cut behavior and rate data quality.

The presence of conductive fractures and Super-Ks substantially influences the flow profile and water cut of horizontal wellbores. These features create high permeability conduits along wellbores such that they dominate production and may cause some matrix sections to contribute little or nothing as observed on FSI profiles. The effect of fractures on production from less permeable sections in the wellbore was investigated at different operating rates using horizontal wellbore simulation modeling.

Both MPFM measurements and FSI logs showed that water cut from horizontal wells, affected by fractures and/or Super-Ks, can decrease if they're flowed at higher rates. Upon reviewing and analyzing data from numerous FSI logs, the study has been able to relate the water cut and surface choking to the well productivity index (PI). Consistently, wells with PI more than twice the averaged matrix PI were found to always perform better at bigger choke sizes. By choke relaxation, the water cut decreased by up to 22% while increasing oil production. Wellbore modeling also suggested that the influence of a fracture on flow contribution from remaining sections in the wellbore can be minimized if the well is operated at higher rates. Restrictive surface chokes were found to disproportionately affect lower permeability sections compared to conductive fractures or Super-Ks which in most cases were invaded by water after water breakthrough. Relaxing these surface chokes allowed more contribution of dry oil from the lower permeability sections, hence the increase in overall oil production and drop in water cut in the affected wells.
Insights into the Impact of Water Salinity on Multiphase Flow at the Pore-Scale in Carbonate Formations
Authors: Abu-Al-Saud Moataz , Esmaeilzadeh Soheil , Tchelepi Hamdi
Published: March 2019

Understanding the effect of injected water salinity is becoming crucial, as it has been shown to have a strong impact on the efficiency of oil recovery process. Various experiments have concluded that carbonate wettability is altered when the water ionic-composition is changed. In this work, a numerical investigation of an oil blob mobilized by water is conducted inside a single pore. The presented model studies the synergy effect of multiphase flow and water salinity at the pore level.

To model the multiphase flow at the pore-scale, the full hydrodynamic Navier-Stokes equations are solved using direct numerical simulation (DNS). The effect of brine ionic-composition is examined through the electric double layer effect. Experimental zeta potential values, published in the literature, of crude oil/water and water/carbonate interfaces have been employed in the model, which capture the water salinity effect.

The simulation results show that the water wetting film surrounding the oil-droplet collapses to an adsorbed nanometer water layer when high salinity water is used. As a result, a large pressure gradient is required to mobilize the oil inside the pore and overcome the attractive surface forces between the oil/water and water/carbonate interfaces. For low-salinity injected water, the carbonate surface becomes more water-wet. The wetting film surrounding the oil blob becomes stable due to the repulsive electric double layer force. Therefore, less energy is required to mobilize the oil blob inside the pore compared to high water salinity. The effect of solid roughness and injected water flow rate are also studied, which show to have a strong impact on the oil displacement efficiency.

The novelty of the numerical method lies in efficiently capturing the nanoscale effect of the electric double layer in pore-scale multiphase flow at the microscale. The simulation results provide fundamental insights on the efficiency of low-salinity waterflooding at the pore level.
Research of Drilling and Completion Technologies for Heavy Oil in Venezuela and Offshore Presalt Hydrocarbons in Brazil
Authors: Fu Jin , Wang Xi , Zhang Shunyuan , Chen Chen
Published: March 2019

Located in south of Eastern Venezuela Basin, Orinoco Oilfield is an onshore heavy oil field in South America. The heavy oil is known for its high content of acids, heavy metals and asphaltenes with a viscosity of 1000-10000mPa·s. According to the reserve report released by PDVSA by the end of 2016, JUNIN Block that is situated in east of Orinoco Oilfield has an OOIP of 178*108bbl.

Data of drilled wells and distances between offset horizontal intervals in Orinoco were both studied to improve ultimate production rates. 3-dimension borehole trajectories were designed and the most effective anti-collision measures were taken.

After optimziation 8-12 horizontal wells are distributed on one pad. As the horizontal interval extends, the stable production time is prolonged and the accumulative production per well improves. However, the recovery rate stops increasing when the horizontal interval is over 1600m in JUNIN Block. Economically a large space between offset horizontal intervals results in fewer wells and lower costs, but a smaller space contributes to a higher production efficiency per well. If the space exceeds 600m, the accumulative production rate increases much more slightly. A three-dimension well trajectory consists of a vertical interval, an angle building interval, an angle holding interval, an angle building & direction changing interval, a direction turning interval as well as an absolute horizontal interval.

Since Petrobras developed the first ever offshore deep reservoir (Lula) by scale in 2006, Brazil has been conducting a progressive campaign targeting hydrocarbons buried under deep water, which contributes to discovery of Lula, Carioca, Jupiter, Buzios, Libra and other giant presalt reservoirs in Santos Basin after Campos Basin, where there are 9 oil fields ranking among the top 20 offshore oil fields in terms of OOIP. By June 2017 over 160×104bbl oil and gas were produced per day in deep water of Santos Basin, taking up 57.1% of the total yield of Campos and Satos.

Creep deformation of ultra-thick salt beds, severe loss of limestones, poor drillability of formations and insufficiency of deep water drilling equipment all make drilling and completion challenges more complicated. Mud systems and casing programs are optimized to conquer creep of salt and formation of hydrates due to low downhole temperature. Turbines + impregnated bits are deployed to improve drilling efficiency of siliceous carbonates (Lagoa Feia A Group). Precise control of ECD and efficient LCMs solved engineering challenges caused by narrow density windows (Lagoa Feia B Group and Lagoa Feia C Group).
Dynamic Response of Side-Mounted Guns and Assessment of the Potential Damage Risk to Sensitive Tools
Authors: Craddock G. G. , Rios Federico , Burky Thomas , Rodgers John , Serra Marco , Khairy Tamer
Published: March 2019

Side-mounted gun strings present a unique challenge for predictive perforation modeling tools because of their asymmetric geometry. To fully capture the dynamic response of the side-mounted system and more accurately predict the response of any gun system in general, it is important to fully capture the three-dimensional (3D) effects of model geometry and detonation-induced loading.

This work details the modeling approach developed for a side-mounted gun system that enables the full geometry to be simulated so that accurate predictions of stresses and displacements could be made; these predictions are necessary for evaluating the damage potential to sensitive tools in the string, It is important to allow operation designers to optimize gun spacing and provide string flexibility to help ensure it can withstand downhole conditions without affecting performance.

The simulation methodology was calibrated against previous test measurements, where loads and accelerations were captured during surface testing of a gun string. A detailed model was developed for the planned operation, and simulations were performed to predict the dynamic response of the wellbore fluid and tool string. Multiple damage sensitivities were identified for particular tools, and model results were extracted to evaluate 1) pressure dynamic loading on the tool, 2) displacement levels where movement is expected, and 3) dynamic loading of the tool. These results were provided to the developers of the sensitive tool to help assess potential damage risks.

For each case, predictions were compared to previous test results and operation experience to develop a risk evaluation for the planned operation. Further, results were used to make adjustments to the operation to help optimize performance; comparison plots are presented for the different configurations evaluated. This overall process provided confidence to the operators that the operation would be performed successfully with no damage to the sensitive tool.
Multifunctional High Temperature Water-Based Fluid System
Authors: Panamarathupalayam Balakrishnan , Manzoleloua Cedric , Sebelin Linus , Aung Tint Htoo
Published: March 2019

The development of deep oil and gas reservoirs requires high temperature stable drilling fluid systems. The properties of conventional polymers in water-based systems decline above 300°F which led to the development of the new high temperature water-based system.

The high temperature water-based system, featuring a newly developed synthetic polymer, has been developed to provide enhanced rheological profiles and fluid loss control, along with long-term stability under elevated temperature and pressure conditions. The system has been designed to minimize formation damage by forming a thin and ultra-low permeable filter cake. The versatility of the developed polymer allows the new system to be formulated at a wide range of densities using most conventional oilfield brines including monovalent and divalent halide and formate brines.

The clay-free high temperature drilling fluid has stable rheological properties, no gelation and low sag tendencies which are ideal for high temperature logging applications. Also, the highly branched nature of the polymer provides a rheological profile suitable for coil tubing applications.

A new breaker package was developed along with the high temperature water-based system to slowly and uniformly clean-up its deposited filter cake, reducing near wellbore damage and maximizing production when the system is used to drill open-hole completion wells.

This paper summarizes the fluid design in the lab and recent field applications, where the new high temperature polymer-based system was successfully deployed in different locations around the world.
High-Order Accurate Method for Solving the Anisotropic Eikonal Equation
Authors: Waheed Umair bin
Published: March 2019

High frequency asymptotic methods, based on solving the eikonal equation, are widely used in many seismic applications including Kirchhoff migration and traveltime tomography. Finite difference methods to solve the eikonal equation are computationally more efficient and attractive than ray tracing. But, finite difference solution of the eikonal equation for a point source suffers from inaccuracies due to singularity at the source location. Since the curvature of wavefront is large in the source neighborhood, the truncation error of the finite difference approximation is also significant, leading to inaccuracies in the solution. Compared to several proposed approaches to tackle source singularity, factorization of the unknown traveltime is computationally efficient and simpler to implement. Recently, a factorization algorithm has been proposed to obtain clean first order accuracy for tilted transversely isotropic (TTI) media. However, high order accuracy of traveltimes is needed for quantities that require computation of traveltime derivatives, such as take off angle and amplitude. I propose an iterative fast sweeping algorithm to obtain high order accuracy using factorization followed by Weighted Essentially Non-oscillatory (WENO) approximation of the derivatives. Although this method yields highly accurate traveltimes but it also results in increased computational load. Therefore, I propose a parallel fast sweeping algorithm to compute fast and accurate solution of the anisotropic eikonal equation. High accuracy is achieved first by using factorization followed by the WENO approximation of derivatives, whereas computational speed up is obtained by sweeping the computational domain in parallel. With a large number of CPUs, significant reduction in computational cost can be achieved for large 3D models. Numerical test shows improvements in accuracy of the TTI eikonal solution.
Advanced Wellbore Stability Analysis for Drilling Naturally Fractured Rocks
Authors: Han Yanhui , Liu Chao , Phan Dung , AlRuwaili Khalid , Abousleiman Younane
Published: March 2019

An advanced wellbore stability analysis software product has been developed in-house at Aramco. This product offers three analysis modules: (1) the classical mechanical module (elastic); (2) the time-dependent analysis module (poroelasticity); and (3) the time-dependent analysis of naturally fractured rock module (dual-porosity and dual permeability poroelasticity). The stress and pressure analyses are integrated with four rock failure criteria (Mohr-Coulomb, Drucker-Prager, Modified Lade, and Hoek-Brown) to calculate critical mud densities. The basic mechanical module is similar to the wellbore stability module provided in the most-frequently-used drilling geomechanics software. What sets this product apart from the others is that no commercial drilling software to date has the time-dependent stress and pressure analyses modeled by this product's poroelastic and dual-porosity poroelastic modules, which can capture real-time phenomena introduced by the time-dependent fluid pore pressure perturbation and the wellbore time-dependent failures in tension and/or compression.
Using Hypothesis Testing to Evaluate Key Performance Indicators in Real Time: An Edge Computing Use Case
Authors: Kowalchuk Peter
Published: March 2019

Harvesting vast amounts of data has long been identified as an enabler of operational performance. The measurement of key performance indicators is a routine practice in well construction, but a systematic way of statistically analyzing performance against a large data bank of offset wells is not a common practice. The performance of statistical analysis in real time is even more rare. With the introduction of edge computing, devices capable of complex analytical functions in physical proximity to sensors and operations, this practice can be realized. Two case studies are presented: rate of penetration (ROP) and amount of vibration per run.

Hypothesis testing is a statistical method in which a sampled dataset is compared against an idealized or status quo model. This model is built using many samples from a population. The characteristics of the population are then inferred from these samples. The model is built in centers where large amounts of data are available. These models are then transferred to an edge device in the field. The device collects real-time data and compares results to the status quo model. In the two cases presented, hypothesis testing was used to determine maximum and minimum levels of ROP and downhole vibration. This information is used to determine the effectiveness of new drilling practices, technologies, or methodologies. Because calculations are performed in real time, changes to drilling practices can be adopted quickly.

The ROP case was performed at a US operating unit; the vibration case was performed in a Middle East unit. The models showed what improvement values should be. It was revealing to find wells that were thought to be poor performers were actually well within the population normal. Wells were also found that were thought to be good performers, but where new drilling methods were used, actually fell within the population model and thus suggested that the new methods had not affected performance. By performing this analysis on the edge device, operations can make changes early in such a way that results fall outside the status quo model and deliver real performance improvements.

The paper presents the novel use of statistical models calculated in data centers in conjunction with real-time operations. Similar approaches in technical and physics modeling exist in which models are produced in the office and used in the field. However, building models for operations management, from a large bank of offset data, and performing analysis in the field with real-time data is a not common practice. This paper shows both technology and statistical methods that provide a valid scientific framework for operational performance improvement.
Turning an Offshore Analog Field into Digital Using Artificial Intelligence
Authors: Espinoza Roberto , Thatcher Jimmy , Eldred Morgan
Published: March 2019

Replacing all analogue sensors in the oil field is very costly and normally only a fraction of them is done. Currently, there is no cost-effective method to efficiently, reliably and accurately capture analogue meter readings in a digital format. Operators are then left with only two options: either replace them with digital (high capex) or continue with manual gathering (high opex). This paper shows how computer vision and artificial intelligence was used for the first time to capture analogue field gauges data with dramatic reduction of cost and increase reliability.

This unique solution was implemented in the Cheleken Oil field, Caspian Sea, Turkmenistan. In the offshore platforms, only low-cost cameras were necessary, and gauges were identified using QR codes. During the field trial, operators were only required to take pictures of the gauges at a given interval of time and upload the photos to the application. After an innovative process of calibration, the acquired images were processed using artificial intelligence and deep learning computer vision.

Routine manually gathered data was compared with data collected using this solution with the following observations made: Date/time: Operators usually round time. The solution described records time on the captured pictures automatically.Value: Manually gathered data is subject to reading, typing and transcription errors. This solution has no error (provided a good calibration is done).Data Modification: Data gathered automatically with this solution has no human intervention. Therefore, is not subject to alteration, copying or duplication.Data collection with pictures was completed in 1/10th of the time that manual processes take.The business benefits from quicker operator rounds with improved accuracy in meter reading data, and time stamps. The administrative burden for operators of filling in extensive spreadsheets which are prone to error was reduced, this allowed them to collect more meter readings or be reassigned by management to more important scopes of work that bring greater value to the business. Once more it was proved that "a picture is worth a thousand words ".

This solution offers an excellent opportunity for digitizing the marginal section of the field and provides a unique way to turn all analogue data into digital with a very low cost of implementation, on an infinitely scalable platform that is vendor agnostic and simple to manage.
Integrated Formation Evaluation Using High Resolution Sedimentary and Facies Analysis an Aid for Field Development: A Case Study from North Kuwait
Authors: Sanyal Arunava , Kumar Sanjeev , Al Awadh Ahmed , Al Samhan Sarah , Al Azmi Jassim , Sikdar Koushik , Sultan Gamal Ali , Das Sourav
Published: March 2019

Zubair Formation is one of the key producers in North Kuwait; however, the reservoir complexity and hydrocarbon movement along with pressure depletion always poses challenge for determining the perforation and completion strategy to optimize the production. Zubair Formation is broadly divided into three parts e.g. upper, middle and lower, the upper and lower units are of utmost importance for the current study. An integrated approach was adopted utilizing the high-resolution borehole image outputs; which has not only helped in identifying thin bedded reservoir zones but also facilitated the understanding of detail reservoir geology and sand dispersion.

Integrated formation evaluation and workover design is always the key to sustain the production and it becomes even more important when the reservoir is highly heterogeneous in nature and coupled with declining pressure trend. Therefore, an innovative methodology was necessary to address the uncertainties. High resolution borehole images were utilized to determine the sand count, which can detect even the thinnest reservoir layer in the formation. Heterogeneity analysis was also performed to understand the relative sorting of the different reservoir units; sorting has a direct relation with reservoir permeability and thus reservoir productivity. High resolution sedimentary analysis was performed to understand the detailed sedimentology using the borehole image derived dip data; cross bedding types were identified which provides fair idea about depositional energy condition along with depositional environment. All the high-resolution inputs were integrated with openhole logs and volumetric results, which led to a clear deterministic picture of the reservoir, based on which crucial decision was taken.

This integrated approach was adopted in three deviated well sections in Zubair formation, which has facilitated in improving the well performance. Detail sedimentary analysis and cross bedding typing in multiwell helps in fine tuning the sand dispersion in the reservoir model; which in turn found to be helpful for deciding future well locations.
Using Unstructured Grids for Modeling Complex Discrete Fracture Network in Unconventional Reservoir Simulation
Authors: Ding XiangYang
Published: March 2019

Unstructured gridding has become an important subject matter in reservoir simulation. Its flexibility of grid generation and enhanced simulation accuracy have gained popularity in reservoir simulation, especially when modeling reservoir with complex wells and faults. In this work, unstructured gridding is being extended to model the complex discrete fracture network in unconventional reservoir simulation. The typical way of gridding in reservoir simulation is using structured grid due to the easiness of cell indexing but the drawback of zig-zag approximation of reservoir geometry is also apparent on the cells near well, fault or fracture. However, such challenge is addressed when using unstructured grid, where the grid cells can be generated conforming to the geometry without large extent of approximation. In this work, 2.5D unstructured PEBI gridding is being used to model the complex discrete fracture network where the fracture geometry can be straight line or irregular. Grid density is controlled by a multi-level scheme based on region of interest in the reservoir and geometry locations of well and fracture. Near-well and near-fracture flow modeling are being enhanced with the use of high resolution grids in the area close to wellbore and fracture pathway. Particularly in the near-fracture area, the unstructured gridding method generates Logarithmically Spaced Locally Refined (LSLR) grid to capture the transient in the ultralow-permeability shale, to satisfy the requirement to model the large fracture pressure gradient which is sensitive to stress changes.

This adaption of unstructured gridding method in modeling fracture in unconventional reservoir brings the gridding flexibility to model the complex fracture geometry. By using the fracture oriented grid density control scheme, pressure gradient change in near-fracture area can be modeled with enhanced accuracy. Benefits of using unstructured grid are demonstrated on simulation example by using unstructured grid and being compared with the structured grid.

This presented work introduces an enhanced way of complex fracture modeling in unconventional reservoir simulation by using unstructured gridding framework. It improves the grid generation efficiency and simulation accuracy, which is valuable in unconventional reservoir simulation and development.
Enhanced Augmented/Mixed Reality and Process Safety Applications
Authors: Potts Jeff , Sookdeo Terrance , Westerheide John , Sharber Dustin
Published: March 2019

As the oil and gas industry undergoes a digital transformation, the massive volume and variety of information being ingested at increasing velocity necessitates new methods of data interaction for decision making. Additionally, effective management of safety risks and flawless operational execution in an evolving oil and gas industry requires innovative applications of digital technology. By superimposing contextually-relevant digital information on the physical world, augmented and mixed reality (AR/MR) technologies have tremendous potential to meet these challenges by providing a more intuitive way to interact with data, train personnel, and ensure process safety.

However, a major challenge with AR and MR technologies is the limited processing power and capability of available hardware. A cloud-based software platform has been developed to overcome computational limitations of AR and MR devices, enabling interaction with significantly more complex 3D content. Additionally, this enhanced AR/MR software platform enables real-time connectivity across different hardware architectures – such as smartphones and Microsoft HoloLens devices – creating powerful new capability for remote collaboration. This unique software platform transforms consumer-grade AR and MR devices into powerful industrial tools useful for a variety of oil and gas applications.

This study will illustrate the functionality enhancements provided by this software platform and how it greatly increases the application potential of AR and MR, including a case study on adoption of this enhanced AR/MR technology for process safety using threat response drill (TRD) scenarios. Enhanced AR and MR provides full-scale virtual TRD scenarios that enable practical demonstration of operational readiness and proactive risk management. Crew response capability and human performance can be collaboratively evaluated with gamified AR/MR techniques, allowing for multiple outcomes based on user inputs through multiple interaction modalities, enabled by the underlying software platform. Enhanced AR/MR enabled by this software platform can drive major improvements in process safety and ultimately help reduce CAPEX, increase efficiency, and mitigate risk across the oil and gas industry.
Integrated NMR Fluid Characterization Guides Stimulation in Tight Sand Reservoirs
Authors: Ighodalo Endurance , Hursan Gabor , McCrossan John , Belowi Ali
Published: March 2019

Unconventional tight reservoir sands have low porosity and very low permeability (mostly less than 0.1mD) due to their fine grain size and poor grain sorting that is often exacerbated by extensive diagenetic effects such as cementation and compaction. Petrophysical evaluation in these formations is very challenging. Conventional downhole logs such as density, neutron, sonic, gamma ray and resistivity measurements provide limited information on pore size variations and often missed Key geological features especially at the early stages of reservoir development. Fluid characterization at the earliest possible stage is paramount to guide the development of these reservoirs where tight well spacing, stimulation (fracturing) and or horizontal well completion is usually required. The main objective of this paper is to show a process of fluid characterization in unconventional tight sand that guides reservoir stimulation.

Porosity partitioning using nuclear magnetic resonance (NMR) logging data helps address these challenges in three distinct steps. First, the 1-dimensional (1D) NMR T2 spectrum quantifies the amount of bound and free fluids pore space and reveals reservoir quality with unique sensitivity. In this step, the NMR fluid substitution method was utilized to ensure consistency between NMR logs in oil-based mud (OBM) and water-based mud (WBM) systems. Second, the free fluids are further subdivided into hydrocarbon and water phases using a 2-dimensional (2D) NMR T1/T2 processing technique. Third, the hydrocarbon phase is subdivided again into liquid and gas phases where a gas flag is turned on whenever the NMR gas signal significantly exceeds measurement uncertainty. This enables detection of live hydrocarbons with high gas-oil ratio (GOR).

This paper presents the integration of NMR analysis into petrophysical evaluation of an unconventional tight sand reservoir. The evaluation helped optimize the best interval for stimulation. Fluid sample acquired with formation tester correlated very well with NMR log-based fluid prediction.

Integrated NMR analysis, including bound fluid vs. free fluid analysis and 2D NMR-based fluid characterization, including gas indicator flag, was applied to establish the presence and type of hydrocarbon in tight sands and select the best representative interval for stimulation. The continuous reservoir quality and fluid distribution profiles provided by these logs were beneficial for the geological understanding and complex formation testing operations in this challenging reservoir.
Virtual Workstation Deployment in Malaysia Oil and Gas Company: Performance Improvement and Cost Reduction Experience
Authors: Mat Dait M Hafiz
Published: March 2019

The objective of the paper is to share the experience and result of deployment of Virtual Workstation in Malaysia Oil and Gas Company replacing the more expensive high-end workstation. This is a part of company's digital transformation program towards the 4th Industrial Revolution. VWS is a modern technology that accelerates and improves subsurface and petroleum engineering application and function. It replaces outdated high-end workstation set-up. In high-end workstation set-up, subsurface technical software was installed at user workstations. Master Data on the other hand, located at centralized data center, BDC; but in order for the user to retrieve the data, it has to go through regional data center at KPC first. All these processes happened through existing small 1 GB cable networks capacity. Separate software and data location, multiple location points for data retrieval and weaker cable network capacity lead to less efficient software performance and data insecurity. But in VWS set-up, issues of under-performed software and data security are eliminated. Now both software and data are installed and located at BDC. Then the user will access their software and data virtually via company's intranet at with the strength of 10 GB cable network capacity that VWS has. VWS deployment resulting in: i) Performance and productivity: increased efficiency for technical applications and optimization of technical resources. ii) Cost: optimization of cost on IT infrastructure. iii) HSE: Reduced IT footprint and energy consumption. iv) Data security: increased data security. v) Flexibility: improved collaboration for technical users. vi) Standardization: standardized desktop environment for enhanced support. VWS deployment only need the VWS system and standard normal workstation to function as good as the more expensive high-end workstation. With VWS, standard workstation is enough to process and run petroleum engineering software and data, since the workstation only act as a visualizer of their actual software and data that located in BDC. With deployment of standard workstation instead of high-end workstation, VWS expected to contribute to cost saving of RM 86k per user for 3 years of leasing.
Robust Tomographic Full Waveform Inversion using Adaptive Amplitude Estimation
Authors: Almomin Ali
Published: March 2019

I examine the basis of slow convergence of tomographic full waveform inversion (TFWI) and discover that the reason behind it is the unbalanced effects of amplitudes and phase in the design of the regularization term. This imbalance results in a strong reliance of the kinematic updates on the amplitude fitting, slowing down the convergence. To mitigate the problem I propose two modifications to the tomographic inversion. First, by modifying the regularization term to focus more on the phase information, and second, simultaneously updating the source function for modeling. The adjustments reduce the gradient artifacts and allow for explicit control over the amplitudes and phases of the residuals.

Tomographic full waveform inversion (Symes, 2008; Sun and Symes, 2012; Biondi and Almomin, 2012) is an innovative inversion technique that preserves all the advantages and benefits of full waveform inversion (FWI) while at the same time bypassing its strict initial model requirement and cycle-skipping challenges. To reach this objective, TFWI alters FWI by merging its classical form with a modified form of wave-equation migration-velocity analysis (WEMVA). This combination displays itself as an extension of the velocity model through virtual axes (Biondi and Almomin, 2013).

The modeling operator is able to match the observed data by extending the velocity model with the proper axis, no matter what the accuracy of the initial model is, by using kinematic information from the extended axis with disregard to the occurrence of cycle skipping. The inversion is set up to extract all the essential information from the virtual axes and smoothly fold them back into their original, nonextended form of the model. The kinematic and dynamic information of the data were successfully inverted with exceptional robustness and precision.

Even though cycle-skipping is not an issue with TFWI, this method creates its own challenges, which are; its high computational cost and the big number of iterations that it needs (Almomin and Biondi, 2013). The conventional FWI uses only a single frequency per iteration to match the phase (Pratt, 1999; Shin and Ha, 2008). Not using amplitudes reduces the accuracy of the solution because it prevents the simultaneous inversion of scales. Modifying the gradient calculation is another method that is used to reduce some "kinematic" artifacts (Fei and Williamson, 2010; Shen and Symes, 2015). These methods are appropriate for image-domain velocity analysis methods, such as WEMVA. The explicit calculations of the nonlinear modeling operator and residuals in the data space prevents it from being applied in TFWI.

Two adjustments to TFWI are proposed to reduce the slow convergence and allow for more control of the ratio between amplitude and phase. These adjustments are consistent in the framework of TFWI and allow for an accurate calculation of the gradient in the data space. The adjustments were tested and resulted in a reduction in the kinematic artifacts in the gradient.
The Use of Digital Core Analysis in Understanding the Effects of CO2 Aging to Carbonates Samples
Authors: Sazali Wan Muhammad , Md Shah Sahriza Salwani , Kashim M. Zuhaili , Kantaatmadja Budi Priyatna , Knuefing Lydia , Young Benjamin
Published: March 2019

PETRONAS is interested in monetizing X Field, a high CO2 carbonate gas field located in East Malaysian waters. Because of its location (more than 200 km from shore) and the preferable geological formation of the field, reinjection of produced CO2 back into the field's aquifer has been considered as part of the field development plan. To ensure feasibility, the PETRONAS R&D team has conducted a set of laboratory analyses to observe the impact of CO2 on the carbonate formations, through combining the use of static CO2 batch reaction experiments with advanced helical digital core analysis techniques. The analysis of two representative samples, from the aquifer zone is presented here. The initial state of the samples was determined through the use of theoretically exact helical micro computed tomography (microCT) techniques. The images were processed digitally to determine the porosity and calibrated with RCA to ensure the reliability of digital core analysis results. After scanning, both plugs were saturated with synthetic brine with similar composition as the fields' formation brine and aged with supercritical CO2 at reservoir temperature and pressure for 45 days. After 45 days, the aged core plugs underwent post reaction analysis using micro-CT scan and image processing software. Based on macroscopic observation, the core plugs showed no changes after aging with supercritical CO2 at high pressure and high temperature (HPHT) as per reservoir condition. However, analysing the high resolution micro CT images, the team was able to determine the changes in porosity before and after CO2 aging, which are around 1%.
Standardize/Simplify Water Flood Pattern Reviews
Authors: Al-Yazeedi Zeyana , Al-Zaabi Yousuf , Al-Oraimi Mahmood , Al-Kiyumi Wafa , Al-Rawahi Ashwaq , Al-Tobi Kifah , Al-Gheithy Ali
Published: March 2019

Objective/Scope

Water flood WF accounts for 40% of Petroleum Development Oman PDO's oil production and volumes. A proper WF management is a key to realize that. This project aims to standardize and simplify WF performance review process, which is very important part of WF management.

Methods, Procedures, Process

The current condition of WF performance review vary from field to another in term of frequency of conducting the reviews i.e, once a year, quarterly which resulted in missing the opportunities to improve the WF performance on the right time.

Different in house tools and databases are used to prepare the technical materials for the review meeting. As a result, different fields have different way of presenting the technical materials to the reviewers across the company, so no standard pattern review template available and multiple sources for data are used. The field petroleum engineer takes up to 4 hours to prepare the technical material for one pattern review and usually senior or high skills PE requires generating different type of plots. When the Pattern review conducted almost 4 hours for the individual petroleum engineers spent during one pattern review.

The proposed counter measures for this project were to replace the review frequency to exception or requirement base to ensure no missed opportunities. As well as standardizing the technical materials for WF pattern review using a single tool/source. The standard template has to fit all patterns in a field. It has to be accessible, with good visualization, and secured storage

A Successful pilot run in one of the water flood fields in North Oman with 30+ WF patterns and has demonstrated the following results; standard review template developed within one source data platform. The pattern review was conducted on exceptional based which was a proactive approach. The PE team managed to generate extra optimization opportunities which resulted in proven an increased in oil production of +30 m3/d from 5 patterns. PE saved 3.5 hours/ pattern in preparation. The reviewers appreciated the improvement of quality of the technical materials, which create direct focus on issues identified based on exception. All the technical material were easy to generate by any less experience engineers.

To maintain sustainability of the achieved improvements, some lean tools have been used. These tools are summarized in the following points; Standard operating procedures (SOP); two SOPs were generated, one to set up the tool and the other to do the review.Visual management (VM); was also generated to keep track the pattern review and ensure healthy WFM and.Leader Standard Work (LSW); it was completed to ensure sustainability through leader ship support.