bluuebunny/crossref_metadata_2025 huggingface dataset:
Turning a High-Pressure, High-H2S Oil Carbonate Reservoir Development Viable Through Miscible Gas Injection in the Sultanate of Oman
Authors: Mourad Ahmed , Awadhi Mahmood , Calvert Stephen , Djermouni Karima , Hattali Ahmed , Nabhani Abdullah , Noirot Jean-Christophe
Published: November 2018

The development of low porosity, low permeability carbonate oil reservoirs remains a challenge in the industry. Identifying a technically and economically viable development is further complicated when high pressures, high temperatures & high H2S concentrations are encountered at large depths. For such reservoirs, depletion developments are typically the only economically justifiable option but typically result in very low Hydrocarbon Recovery Factors. This paper presents a case study of a complex field located in the south of the Sultanate of Oman that includes a carbonate stringer reservoir encased in the Ara Salt. A viable Miscible Gas Injection (MGI) development scheme has been identified and turned into an economical option for this field.

The field X A3EC was discovered in 2011 within the Greater Birba area. Since it was put on production in 2013, the performance of this carbonate stringer has been relatively poor compared to other analogue fields. No feasible technical solution could be identified to develop the field beyond the very low estimated ultimate Recovery Factor (~6%) achievable under depletion. Alternative developments could not be sanctioned mainly because of poor economics resulting from limited expected incremental recovery. Moreover, the drillability of additional wells could not be confirmed following subsurface re-interpretation & dynamic history matching of the available pressure data.

In 2017 a study was carried out that incorporated newly collected pressure data, seismic and geological interpretations, as well as static & dynamic modeling. A new approach to history matching was also applied. This study turned further field development from technically unfeasible into an economically attractive & doable project. Moreover, new appraisal and well stimulation plans were identified to address the remaining field uncertainty on the in-place volume and well productivity. The proposed technical solution for further development of Field X A3EC involves a phased implementation of a MGI scheme which will increase the expected Recovery Factor in the target zone by more than 35 %. The drillability of the targeted field area was established by reducing the uncertainty on the reservoir pore pressure through extensive dynamic simulation work supported by newly collected long-term pressure build-up data. Field X A3EC development will feed into and benefit one of the largest projects in the Middle East - the Rabab Harweel Integrated Project (RHIP) that is currently under construction, further adding to the value of this large integrated facility.

This paper highlights the challenges faced whilst developing complex contaminated oil carbonate reservoirs and identifies technically feasible solutions for further development of such fields via an integrated approach.
Integrity and Life Extension Assessment of Fixed Offshore Platforms
Authors: Shanker Vivek
Published: November 2018

A considerable number of fixed offshore platforms around the world have either already surpassed their design life or are approaching it. In the Middle East, more than 70% of the platforms are operating for more than 25 years; some of the assets are even operating for more than 40 years. High oil price and advancement in technology planned to increase the productivity of reservoirs have led to significant investment in terms of cost and resource to manage these assets. There is still a lot of recoverable oil and gas in the reservoirs hence, there is an increased need to extend the life of these facilities while managing the associated risk. This technical paper details a methodology for assessment of remaining life and details some of the degradation/ life extension issues for fixed offshore assets. As it is extremely difficult to cite all the degradation issues, some of the critical degradation issues based on experience and knowledge has been covered in this paper.
Use of Distance Protection in EHV Submarine Cable Network in Oil and Gas Industry
Authors: Mandal Prabuddha , Paul Raju , R. Kamal Faris , Takeiddine Oussama
Published: November 2018

Objective

Present trend around the world is to power up the Offshore Oil and Gas facilities by power from shore. The popular choice is to use Extra High Voltage submarine cables for handing these large quantities of power. The objective of this presentation is to focus and explain how the EHV cables and offshore facilities can be protected by Distance Protection.

Application of Distance Protection in Oil and Gas Industries

The efficient protection of the costly submarine cables and the offshore facilities from the electrical fault is extremely important. One of the most efficient ways to protect these types of electrical network is by using Distance Protection. EHV Interconnected grid network often involves bidirectional flow of power. If a fault in one interconnecting cable is not identified and isolated fast, it can cause substantial damage to the equipment and system. Also it is necessary to identify the faulty section correctly and ensuring the continuity of the service for the healthy section.

Benefits of Distance Protection in EHV Submarine Cable Network

Novelty focused on this paper

This paper provides comprehensive ideas about effective use of Distance Protection in EHV submarinecable network. This is utmost important because offshore oil and gas facilities are increasingly powered up from shore power using EHV submarine cable. Effective use of the Electrical System will both reduce downtime of the plant and save cost of operation.
Reactive Flow in Unconsolidated Sandstone: Application to Carbon Geosequestration
Authors: Yu Hongyan , Zhang Yihuai , Lebedev Maxim , Wang Zhenliang , Verrall Michael , Iglauer Stefan
Published: November 2018

Carbon dioxide (CO2) inject to the saline aquifers are general considered as the best candidates for large-scale storage and CO2 enhance oil recovery. The pore structure and permeability are changed by the fines release, migration in the initial stage of CO2 injection, which is of great importance for reservoir screening and injection design requires adequate understanding. We thus imaged an unconsolidated sandstone at reservoir condition before and after live brine injection in situ with micro-CT core flooding apparatus. We conclude that the pore structure of the unsolid high pores media rock can be significantly changed after live brine injection, although the porosity just have a small increased. Meanwhile, many fractures are generated in the quartz after live brine flush away. Specific surface area are quantified from micro CT scan image analysis to calculate the absolute permeability. The permeability is significantly improved due to the pore structure change which can improve CO2 infectivity, especially low-permeability reservoirs. The results of this study present a broad characterization of the mechanical properties in lacustrine shale and can therefore help optimize hydraulic fractured fundamental and enhanced gas recovery.
Enhancing Rock Mechanical Properties Estimation for Thin Beds Using Microresistivity Borehole Imaging Tool
Authors: Abbas Ahmed K. , Al-Hamad Nasser , Alsaba Mortadha
Published: November 2018

The knowledge of rock mechanical properties of the Zubair Formation is required to assure the success of future exploration and development of this reserves. Hence, high consistency and quality of these parameters could expressively increase the economic revenues derivable from the reservoir. The main objective of the current work is to generate a high-resolution continuous profile of the rock mechanical properties using microresistivity image log across the thin-bed intervals along with rock mechanical properties laboratory tests.

Retrieved core samples from the Zubair sandstone formation were run through extensive laboratory testing. The rock strength parameters were determined using consolidated drained (CD) multistage triaxial tests, while static elastic parameters were measured using consolidated drained (CD) triaxial tests. A petrophysical log enhancement technique was applied to achieve enhanced resolution neutron porosity log (with a vertical resolution of 0.2 in.). The critical components of this process were achieved high-resolution neutron porosity log from microresistivity image log. This log was directly utilized to calculate high-resolution rock mechanical property logs through porosity empirical correlations.

The resulting downscaled rock mechanical logs exhibited a reasonable degree of positive agreement between the estimated rock mechanical property logs (i.e., unconfined compressive strength (UCS), internal friction angle (φ), Young's modulus (E), Poisson's ratio (v), bulk modulus (K), and shear modulus (G)) and those acquired from the lab measurements, with 1.42%, 2.21%, 2.44%, 1.86%, 2.33%, and 1.92% absolute relative average difference (ARAD), respectively.
A Robust Surveillance and Optimization System for Unstable Flows in Offshore Gas Lifted Wells
Authors: Xiao Feng , Long Ted A. , Velamur Asokan Badri , El-Bakry Amr , Dani Neeraj R. , Holub Curtis , Poole Stephanie
Published: November 2018

In [1] and [2], an automated surveillance and optimization system has been developed and deployed to multiple offshore gas lifted assets. In this paper, we will present key enhancements to the system that improve the detection and management of unstable flows in offshore gas lifted wells. The enhanced system provides engineers and operators with a comprehensive solution for well flow surveillance and optimization.

Examples will be presented to show the successful implementation of quantitative slug scanning, gas lift multi-pointing diagnostics, and production surveillance for unstable flows. The slug scanning module supplements the pattern recognition and machine learning features in GLOWTM [1]. It scans the historical high-frequency pressure data, quantifies the amplitude and frequency of the cyclic oscillations, and then aggregates the data into bins of varying severity levels and a simple slugging index that can be used by operations for effective communication. To better understand gas lift multi-pointing that damages gas lift valves and harms production, transient flow models were developed with accurate modeling of gas lift valves, and then calibrated to historical well tests. Models accurately replicated the amplitude and frequency of pressures that may appear like hydrodynamic slugging, and revealed the open-and-close behaviors among multiple gas lift valves. Finally, the calibrated models were used to generate operational maps with different flow regimes, and such maps aid either asset staff or the GLOW™ system to optimize asset production while managing various types of unstable flows.

The developed system combines data-driven and physics-based approaches for online advisories, and utilizes a novel history matching procedure to enhance the model's predictive capability for complex well behaviors. In summary, the system provides a comprehensive, robust, and integrated set of tools that meets the surveillance and optimization needs of asset staff.
Study on Chemical Combination Formulations for High Temperature and High Salinity Carbonate Reservoirs
Authors: Zhang Fan , Yang Siyu , Ma Desheng , Lv Jianrong , Zhang Qun , Luo Wenli , Zhou Zhaohui , Tian Maozhang , Cai Hongyan
Published: November 2018

Chemical flooding technique is one of effective EOR (Enhanced Oil Recovery) ways to improve the oil recovery for mature oilfield in China. It is usually applied successfully in low temperature and low salinity sandstone reservoirs, such as Daqing oilfield (45°C, 5,100 mg/L) and in Changqing oilfield (50°C, 4,700 mg/L). However, it is great challenges to develop chemical EOR formulations for the high temperature and high salinity carbonate reservoir. On the one hand, the high temperature and high salinity condition may cause decomposition of the conventional chemical agents with poor long-term stability. On the other hand, the oil types and compositions, rock surface property and pore structure are all different for sandstone and carbonate reservoirs. Therefore, it is necessary and important to development low cost and high efficiency chemical formulations for high temperature and high salinity carbonate reservoirs.

In this paper, the betaine surfactant has been synthesized with cheap raw material of fatty acid, and its functional group of hydroxyl propyl sulfo hydrophilic group can improve the heat resistant and salt tolerant abilities; the star-polymer has been developed and the introduction of multi-functional monomer can inhibit the hydrolysis at high temperature and high salinity conditions. The new SP and ASP chemical formulations have been developed, and show good properties for high temperature and high salinity carbonate reservoir. The SP chemical formulations of the betaine and star-polymer show good heat resistant and salt tolerant capability. It could achieve ultra-low interfacial tension (less than 1.0×10-2mN/m) with temperature range from 30°C to 95°C, or salinity range from 5,000 mg/L to 220,000 mg/L.The effect of alkalis on interfacial tensions were studied, including Na2CO3, Na2SiO3, Na3PO4 and Na2B4O7. The ASP combination formulas with Na2B4O7 showed the best interfacial properties.The SP and ASP chemical formulations had good long term stability, and could maintain ultra-low IFT within 180 days, and the viscosity retention rates were greater than 90%.The dynamic adsorptions of this betaine were less than 1.0 mg/g rock, which can meet the requirement of field applications.After water flooding, the oil recoveries of the SP and ASP formulations increased about 22% (OOIP, Original Oil In Place) and the oil displacement efficiencies of chemical combination flooding reached to 75%.

Excellent properties of chemical formulations with the sulfobetaine and star-polymer indicate that this EOR technology can be applied in high temperature and high salinity carbonate reservoir with or without alkaline.
Verification of Shore Pull Anchor Pile Designed Using Simplified Method
Authors: Chen Zongrui , Tan Joshua , Huang Zhiwei , Ng Eng Bin
Published: November 2018

Shore pull anchor piles, which have been proven to be effective during pipeline installation, are designed using simplified method and basic structural analysis software in accordance with API RP-2GEO. This method simplifies the interaction between soil and pile using a series of non-linear soil springs along the pile shaft. In this paper, this simplified method is validated by using a refined finite element model and software which captures the soil and structural member interaction behaviours more accurately. The actual project site soil data is used in this paper for the validation. It is proven that the simplified method is capable of considering both geotechnical and structural capacities of the anchor pile and yields a design that is slightly conservative. Additionally, the simplified method is cost effective with regard to the analysis time and software cost. Parametric study such as soil stiffness and pile group effect are carried out to evaluate this simplified method and provide a guidance for the future design.
Verticalization of Sonic Logs Acquired in a Highly Deviated Well from Offshore Abu Dhabi
Authors: Van Kleef Franciscus , Verma Ravi , Brindle Frank , Dasgupta Suvodip , Donald Adam , Waqas Muhammad , Jocker Jeroen
Published: November 2018

Analysis of single-well sonic measurements to determine formation TI elastic parameters has traditionally been done using deterministic models with multiple, simplistic assumptions using only vertical or horizontal wells with flat structural dip. Here a probabilistic Bayesian-type inversion method is shown, which provides a flexible solution for any wellbore orientation solving for all five TI (transversely isotropic) parameters. This inversion is guided by prior information, which may be; core tests, borehole seismic survey results, offset well data or a public database.

The approach demonstrated here uses prior information of TI elastic properties to determine a consistent model at each depth. The inversion uses all sonic slownesses, compressional, fast and slow shear, as well as Stoneley shear and density to provide a continuous output of Thomsen's parameters and anisotropic mechanical properties at each depth. The results are consistent with offset well data as well as walk-above VSP velocities obtained in the same well. This technique was applied on a prominent and thick shale formation, which is present throughout UAE. Most of the wells drilled in UAE penetrate through this shale formation which is locally unstable for drilling, and is a prominent seismic reflector which directly overlies the reservoir. Accurate geomechanical characterization of this shale formation is critical as more wells are drilled at high angles with the application of full 3D finite-element modeling. Similarily the velocity models used for pre-stack depth migration (PSDM) and seismic well tie require accurate anisotropic TI parameters.

This workflow is new and applicable to any well orientation or structural dip and yields results that are consistent with offset sonic and borehole seismic measurements. Application of this method will have a profound impact on geophysical velocity and geomechanical model building methods and results.
Increased Reliability Using Asymmetrical Six Phase Induction Motor with Double Isolated Neutral
Authors: Mahmoud Elhussien
Published: November 2018

This work suggested the use of asymmetrical six phase induction motors instead of the conventional three phase motors for safety critical equipment to improve the overall system reliability. The rule of thumb is that a single fault should not be able to draw safety critical equipment out of service. Multi-phase machine in general and six phase machine in particular are able to continue running with one phase or more open circuit. The ability of multi-phase machines even to start under fault is another useful feature. Statistically, the main reason for losing one of the motor phases is the single open gate transistor fault. The defected phase is entirely disregarded, and then the current in the rest of phases which still functioning is optimized. Consequently, if minimum copper loss criterion is applied, the paid penalty is 50% additional losses that leads to motor derating, if not pre-designed with proper safety factor. This paper introduces an alternative post fault control strategy, which allows the usage of the entire healthy power electronic switches. An achievement of reducing the post fault increase in stator copper losses to 25% is realized.
A Thorough Investigation of PVT Data and Fluid Model for Giant Onshore Field, Hidden Lateral Trends Identified
Authors: Meziani Said , Tahir Sofiane , Al Hashemi Tayba
Published: November 2018

A best practice for PVT modeling and reliability analysis had been developed in order to characterize complex giant oil reservoir fluid model, oil in place assessment and to optimize full field development and management plan for EOR studies. This study builds on previous studies done by various parties but includes recent data and revised objectives. The primary objectives are: (1) to develop understanding of fluid properties across the reservoir and the influence of separator conditions on formation volume factor. (2) to generate PVT models for the reservoir’s units, accounting for lateral and vertical variations in properties and including the ability to predict the performance of gas injection schemes 3) to estimate the potential for asphaltene precipitation and recommend further work to improve the reliability of the reservoir simulation model. The study is divided into three phases: (1) Review of previous work and conduct Data QC of PVT data. (2) Establish lateral and areal PVT property trends and EoS fluid model. (3) Historical separator conditions issues, reserves and oil in place volumes.

The undertaken review of the previous EOS modeling studies had resulted in very different fluid models, each tailored slightly to focus on the specific priorities of the different studies.

In this study, the understanding of the fluid properties and their distribution within the reservoir has been achieved by: Using a thorough QC process which rejected unsuitable sample dataIdentifying C6+ mass content as the reliable indicator of the fluid compositionGenerating lateral and cross-section fluid property plots to identify regional differencesGenerating C6+ mass content versus depth plots to define compositional gradients and property trends.

Besides, analysis of the later MDT samples did not appear to have been used in identifying fluid property trends in any of the previous reviews. However, after Data QC, 18 PVT samples and reports were chosen to determine the compositional trends, 16 to determine property trends and 2 were identified for development of the EoS fluid model.

Therefore, vertical and lateral fluid property gradients have been identified consistent with the reservoir structural and stratigraphy model. The initial GORs in the layer-cake South/Central regions fall between Rsi= 816 scf/bbl at the top (7551 ft TVDss) down to Rsi=582 scf/bbl near the OWC (8245 ft TVDss). A similar trend is observed in the northern clinoform region, but 106.6 ft deeper. None of the earlier PVT studies had identified lateral trends within this complex reservoir. The main uncertainty in the fluid description is a lack of data below 7950 ft TVDss.
Design and Implementation Challenges for Extra High Voltage Gas Insulated Switchgear, Transformers and Subsea Cables at Offshore Platforms
Authors: Singh Kamaljit , Paul Raju , Kamal Faris , Takeiddine Ousama
Published: November 2018

Use of GIS to handle bulk power distribution has now become popular in offshore facilities due to the inherent advantage of a compact design. This paper highlights the challenges faced during GIS (and associated items) design based on experience on recent offshore projects and recommendations are proposed for methodical approach.

Handling of bulk power at Extra High Voltages poses numerous risks to both personnel as well as assets. This paper discusses the key design parameters, industry standards, interface requirements with transformers/subsea cables/platform structure and installation challenges.

Design engineer must be familiar with industry codes so that all design requirements, including proper selection of GIS configuration, are considered from early stages of the project. Omissions or oversight in this regard can impact the whole project.

Duration for design, procurement, installation and commissioning phases must be adequately accounted for. Specialist studies such as insulation coordination, very fast transient and touch potentials shall be carried out in addition to usual power system and arc flash studies.

Special consideration must be given in case of ring configuration with regard to logic diagrams and differential protection based on multiple CT locations and interconnections. Requirement of voltage selection scheme requires extensive wiring for synchronization function. Relay & CT selection shall be made considering required protection functions, interface with remote location and communication interface with Electrical Control & Monitoring System.

Interfaces with transformers and subsea cables shall be in strict compliance with industry standards such as IEC 62271-209 & 211. Requirement of additional surge arrestors shall be verified.

GIS exerts large static and dynamic forces on platform steel structure. These are also sensitive to forces during platform lifting and transportation. Support structure suitably shall be designed to mitigate the same.

This paper addresses concerns and interface requirements to be considered during design of GIS which will benefit the design engineers, Client personnel and Structural designers along with Project Management Team for safe and smooth execution.

Note: Data / details used in this paper are typical for the GIS handled by our Company that may vary based on the makes, models and ratings of GIS.
Commissioning Advanced Hoist Technologies to Mitigate Challenges Associated with Selective Workover Wells - A Revolutionary Approach
Authors: Shehhi Abdul Naser , Draz Alauddin Mohamed , Mahboob Tayyab Aziz , Agnihotri Praveen
Published: November 2018

Since 2014, ADNOC Onshore has utilized the potential of hoists and commissioned its operational significance, which allowed saving in rig time (4 – 6 rig years per year over 5 years business plan period) and generating a cost saving opportunity.

During this period we have faced many challenges and complications mainly during fishing operations which result in unsuccessful retrieval of the completion. Other factors and challenges that are commonly faced which require hoist intervention include: Old wells melted or corroded fish (Tubing + Casing)Reservoir Thammama Zone B wells (High water cut)Pushing the corroded fishComplete plug & abandonPartial plug & abandon required for future side trackWait on conventional rig arrival for intervention

Main challenge we faced during our business development phase is losing number of oil producing wells due to fishing complications, therefore the hoist rig is not capable to drill or sidetrack such wells. This will result in delaying requirements to restore production and meet the field quota objective since the wells should be scheduled to conventional Rig intervention. In order to optimize the hoists capability and performance to overcome this issue, we have to optimize based on priority and cost-effective selection criteria which will support to save the rig time & cost.

Various advantages of hoists applications experienced in the last 2 years in ADCO include: Running scraperCorrosion and Cement Bond LogsFaster rig move.Work-over well repairs for single completion (well-kill, pulling old completion and running new completion)Well preparation for re-entry and sidetrack plug back to top of 7'’ linerESP work-over. Pulled old ESP pumpsFishing and milling operationsRun 7 "tie back liners.Plug and abandon wells partially or fully Abandonment (inactive string).Spotting and squeezing cement plugs and squeeze off old perforations, changing THS and X-mass tree.Cure Sustainable Annulus Pressure (SAP)Pressure test casingRun completion & special completion such as gas lift mandrels

This paper presents methods of optimizing application of hoist in Abu Dhabi onshore fields by modifying enhanced well selection criteria based on the operation experiment and avoid production loss to sustain our field development plan. This implemented strategy benefit the optimization of number of workover wells which will increase in next five years scenarios, which in turn is expected to utilize rig cost savings. In addition, the new selection criteria will create "fit for purpose" solution to overcome these challenges of existing workover wells with less time and complication
Value of PSDM Processing on Low Relief Structure in East Onshore Abu Dhabi
Authors: Ghafri Thuraya Al , Seo Youngtak , Liu Jinhui , Kim Dong-Oh , Aijing Ren , Belaid Kamel , Mingqiu Zhao , Wenrui Jia
Published: November 2018

The Arabian Gulf is prolific of low relief geological structures, however, their definition and imaging present in general a genuine challenge. It is also commonly understood that low relief structures won't benefit from Pre-Stack Depth Migration (PSDM) whereas, Pre-Stack Time Migration (PSTM) is the ultimate required process. Thus, PSTM is frequently applied for the imaging of these low relief structures.

Nonetheless, our recent 3D PSDM processing work has demonstrated that this perception is not all the time correct and has proved that PSDM can indeed add significant value to low relief structures.

An Anisotropic PSDM (APSDM) workflow was carefully designed and meticulously applied on a very low relief structure located onshore Abu Dhabi –UAE.

The main objectives of this 3D Anisotropic PSDM processing were established as follows: Achieve an accurate & clearer depth structure image with higher resolution.Mitigate & address the observed depth uncertainties at the existing wells.Enhance the faults architecture & imaging.Analyze anisotropic velocity & build a reliable velocity model for depth imaging.Interpret azimuth volumes in depth & time domains.

The designed processing workflow consisted of the following main five stages: Gathers pre-conditioning and residual noise attenuation adopting the principle of amplitude preservation.Velocity building & updating using available well data, interpreted horizons and applying VTI full azimuth and multi azimuth velocity tomography processes.Depth imaging using Kirchhoff PSDM in OVT (Offset Vector Tile) domain.Post migration processing for residual inter-bed multiples & noise attenuation in addition to azimuthal anisotropy analysis and final depth-tie examination.Post stack processing for acquisition foot print removal and signal to noise ratio (S/N) enhancement.

It should be noted that the selection of the optimum processing parameters at all the processing steps was done after the implementation of an intensive testing & rigorous QC/QA procedures.

The main results and findings revealed by the 3D Anisotropic PSDM processing and the subsequent 3D seismic data interpretation are summarized as follows: PSDM shows less depth uncertainty compared to PSTM at existing wells. However, based on the results of recent drilling activities which have been conducted after PSDM, depth uncertainty at new well locations still exists.Reliable velocity model was built for depth imaging. This was established after 12 tomography iterations carried out for the isotropic velocity model and four iterations of anisotropy updates and VTI azimuthal velocity tomography.Some low relief structures are better defined in PSDM than PSTM.Seismic continuity of some target levels has been improved.Seismic resolution is degraded due to the limited frequency content.Fault imaging has been improved at some locations.
Selected Results from Big Carbonate Pore System Database: A Case Study from Saudi Aramco
Authors: Serag El Din Samy , Clerke Edward , Badawi Ahmad
Published: November 2018

Carbonate reservoir complexities are both described and hidden by the use of the common and generic term, "heterogeneous", with usually little serious effort then expended to define and quantify the meaning and dimensions of the term. Saudi Aramco, the custodian of the world’s largest petroleum reserves in carbonate reservoirs, is making long-term efforts to bring light to the carbonate "heterogeneity" darkness. We are constructing the industry’s largest integrated petrophysical and geological databases for our major carbonate reservoirs.

Our large databases contain porosity, permeability, grain density and pore system information from core plugs carefully integrated with a full suite of well log data and core descriptions. These cores have been described in detail using the most current carbonate sequence stratigraphic techniques and all these data have been captured digitally and integrated consistently and carefully. Our database for one field contains 1695 limestone pore systems (a pore system is defined by a single Thomeer hyperbola), obtained from 931 plug samples by Thomeer analysis of core plug mercury capillary pressure data (MICP) with plans to expand the measurements to 1500 plug samples for just this one major reservoir by the year 2020. The current core plugs for the database now include samples from 30 cored wells (up from the 10 cored wells of the previous Rosetta Stone project) to obtain statistically robust reservoir petrophysical data at the facies level. Pore system data are now also being acquired in vertical wells for constrained reservoir layering and vertical reservoir model tie points using nuclear magnetic resonance (NMR) well log data and the CIPHER software for the Thomeer parameter MICP-consistent spectral porosity analysis.

At Saudi Aramco, our extensive facies – petrophysical properties database process delivers the reference reservoir property database for our major carbonate reservoir models. The reference database improves our understanding and modelling of the variation and covariation of the facies and petrophysical rock types (PRTs) for reservoir modeling. It also provides sound statistical support for the population of the reservoir with petrophysical pore system properties within the sequence stratigraphic facies framework. For the reservoir dynamics, the database allows detailed investigations into the statistical linkages of pore system properties which control permeability and relative permeability developed by Clerke and coworkers to the sequence stratigraphic reservoir facies.

We report here selected results from a very large quantity of relationships and statistical attributes that can be derived from this database. At the general carbonates level, these reference databases demonstrate that the reservoir complexity hidden in the shadow of "heterogeneity" is actually the prevalence and statistical distribution of these multimodal pore systems and their attributes.
A Method to Obtain a Permeability - Constrained and Consistent Saturation Height Model
Authors: Hulea Iulian N.
Published: November 2018

The process of differentiating between rock volumes based on petrophysical properties and geological indicators is commonly referred to as rock typing. A rock type can be identified by a given porosity – permeability (k-Phi) transform and Saturation Height Model (SHM) in petrophysical space. Rock typing is a useful method by which geological interpretations are combined with petrophysical measurements and translated into physical space for use in subsurface modelling. Efforts here involve utilizing k-Phi transforms as an input to SHM, thereby streamlining the rock typing process and allowing for compatibility with existing rock typing workflows.

A fundamental part of building realistic subsurface models includes populating a geologic framework with petrophysical properties. From a petrophysical point of view, critical properties with significant impact on the modelling outcome (hydrocarbon volumes recoverable and producibility) are hydrocarbon saturation, permeability and relative permeability. Hydrocarbon saturation is an expression of the rock capillarity translated into a mathematical expression from capillary pressure measurements or well log saturations. Permeability is commonly predicted from porosity, via transform equations used to differentiate reservoir rocks of different quality.

Previous work has shown that permeability and SHM used for subsurface modelling are generally consistent. This implies that the number of input parameters to the SHM can be reduced, which can be done by integrating permeability and saturation data (from logs and core measurements). The number of parameters used in the predictive SHM is reduced from six to four. Here, we propose to constrain the entry pressure (responsible for hydrocarbon entry height) by using routine core analysis data. This approach aiming to look at the plug and log scale has significant benefits when a SHM is derived from well log saturation data or when a limited range in properties is sampled by capillary pressure measurements. The workflow allows the use of other permeability sources (like Drill Stem Test if representative of matrix) as starting point in the process of building a SHM via a simplified Brooks-Corey function. The function can be looked at as a hybrid between the Leverett's J and Brooks-Corey function with entry pressure dependency on the permeability to porosity ratio higher than for Leverett's J (0.7 vs 0.5). The result of linking k-Phi transforms to saturation height modelling allows for compatibility with multiple rock typing approaches that utilize different sorts of parameters to define k-Phi, including Lucia's classic rock fabric numbers, a useful benchmark.
Producing Heavy Oil – The Subsea Brownfield Challenge
Authors: Conde Joao , Banks Mark
Published: November 2018

Objectives

The key challenges concerning heavy oil are not associated with finding reserves, but in extracting, producing and transporting heavy crudes. This is even more challenging given the new normal lower oil price. In this presentation, a case study will be presented showing the successful implementation of highly technical modelling techniques in brownfield heavy oil field developments (UKCS).

Infinity's flow assurance and process engineers have been involved in almost all of the heavy oil developments in the UK continental shelf. - Mariner (12-14°API) and Bressay (11°API), Kraken (14°API), Bentley (10-12°API) and Corona (16°API) are some of the examples worth noting.

Methods and Procedures

In the last couple of years the Production Assurance team at infinity have been responsible for the pre-FEED and FEED stages of one of the most important heavy oil fields in the UKCS. Infinity have provided engineering support to several major E&P companies for their heavy oil developments. This paper focusses on the unusual rheological properties, variable Flow Assurance characteristics during production and the most recent modelling approaches to study the behaviour of these challenging fluids. These projects are particularly interesting as they combine the challenge of both heavy oil and brownfield developments.

Results/Novel Information

Key issues for design of heavy oil fields and development of a safe/optimum operating philosophy are addressed and will be shared in this presentation such as:Modelling non-Newtonian fluids with very high viscosities (impact on line sizing);Oil/water dispersion and formation of a stable emulsion;Selection of an artificial lift option and their respective impacts on the behaviour of the system (focus on HSP technology);Operational issues including relatively high restart pressures following an unplanned shutdown (gel formation).

The key challenges with modelling heavy oil were developed and a novel approach to simulation and data benchmarking was developed in order to solve the classic heavy oil modelling issues. As an example, the relationship between shear rate and shear stress in difficult fluids that deviate from the classic Newtonian behaviour demands a very close relationship between the flow assurance engineers modelling the system and the fluid lab experiments required to benchmark the models.
Comprehensive Workflow of Matrix Acidizing Design and Analysis in Multi-Layer / Multi-Zone Reservoir - Offshore Case History
Authors: Zareiforoush Ali , Safari Alireza , Momeni Ali
Published: November 2018

In this paper we present details of the approach utilized to optimize the well stimulation campaign in the continued development of a huge carbonate gas condensate field in the Offshore Iran. This study discusses what have been done differently, best practices, and learning. What is different in this campaign from previous ones?

Detailed design ✓ Detailed well-by-well review ✓ Fundamental data collection for parameters analysis - operational, subsurface, treating fluid data ✓ Data management system allowing for quick access ✓ Design tool for detailed damage diagnosis, fluid system selection, pumping schedule design, and pressure matches. ✓ QA/QC and compatibility tests aiming to obtain high success rate. Challenges ✓ High contrasts in porosity, permeability and initial pressure ✓ Complex mineralogical & lithology composition ✓ Fissures and Vuggy porosity ✓ Long perforated intervals and well inclination effects ✓ Pre-acid nearwellbore reservoir initial condition ✓ High rate and ΔT effects on completion & cement integrity Objectives ✓ Optimum zonal coverage ✓ Keep completion integrity while high rate injection ✓ Use minimum volume of chemicals ✓ Reduce operation risks & costs

Optimum acid placement in bullheading treatment in commingled mode is still the challenging issue in in Iran well stimulation jobs. We propose a comprehensive step-by-step workflow to get the best results using Nodal Analysis & Stimulation Software in a logical way described later in the text. Diversion techniques history in this field is: Mechanical diversion, Ball sealers, Selective perforation with polymer based diverter, Selective perforation with high injection rate and VDA technique. Our new diversion method that deployed along with a revised placement model, field calibrated to more accurately predict treatment pressure responses, to optimize acidizing design and to maximize diversion in this layered reservoir, studied in this paper.

Results presented include stimulation treatment plots alongside model post treatment pressure matches, pre and post stimulation production logs, clean up data and well test interpretations to validate the models. We describe high/low permeability, multi zone treatments with a bullheaded matrix acidizing technique. We observed in one well through tubing treatment pressures response and oscillate between 2000 and 3500 psi, far above what is typically observed in this field in which the pressure reduction happened quickly from 3000 to 1000-500 psi.

We conclude that due to enhanced diversion results in uniform zonal depletion which is due to uniform zonal acid coverage. We have also found operational benefits in deploying the system in that commingled zones, normally perforated and stimulated in several stages can now be easily and effectively stimulated using a one-stage technique.
Project Specific AUT Automatic Ultrasonic Testing Validation to Determine Height Sizing Accuracy for Pipeline Girth Weld ECA Acceptance Criteria.
Authors: Putsherry Dinesh , Misra Durgamadhaba
Published: November 2018

Objective of project specific AUT (Automated Ultrasonic Testing using Zonal Discrimination) Procedure validation is to verify that the implementation of pre-qualified AUT system performance for the inspection of project specific Pipeline girth welds without changing any essential parameter of system qualification processes.

As per the requirement of DNV-OS-F101, the purpose of the project specific AUT validation is not to perform any new PoD (Probability of detection) analysis. However, to verify the reliability aspects of the system in terms of HSA (height sizing accuracy) to meet the AUT system qualification requirement is to ascertain the project specific AUT procedure adequately capable of detecting and sizing of the smallest critical defects. This is achieved through a detailed validation programme using the project specific welding procedure and pipe material representing actual pipelay scenario.
Modern Approach for Determination of Natural Gas Composition and Heating Value at Custody Transfer
Authors: Veerakumar Ukkirapandian , Lallan Sanjay Singh , Bahumaish Zeyad , Abbas Ahmad
Published: November 2018

Objective and scope

Determination of composition of natural gas and its gross heating value (GHV) at the custody transfer is important for the seller and buyer to calculate the energy content transferred in million BTU (MMBTU). The objective is to develop right analytical technique and equipment to ensure collecting representative sample at high pressure and accurate determination of its composition and gross heating value.

Method and procedure

The low pressure gases at different pressure are compressed and dehydrated to remove moisture. The liquid condensate is dehydrated in a stripper and its pressure is boosted to 150 bar and mixed with dry gas. A special flow and temperature controlled vaporizer is used and spot samples are collected in high pressure cylinders for gas and piston cylinders for liquid. GC with thermal conductivity detector (TCD) and flame ionization detector (FID) with automated gas conditioning unit are used for determination of gas composition. TCD detects the permanent gases and hydrocarbons from C1 to C5 and the FID detects C6 and break down compounds up to C14 including heavier aromatics. Their concentration is derived based on their response factors and bridge calculation using i-pentane in FID. As the gas is sour containing high H2S, special safety precautions are taken with appropriate personal protection.

Results, discussion and conclusions

The gas composition analysis was performed as per GPA 2286 using a gas chromatograph. The low pressure gas contained 35 - 45 mol % of methane while the high pressure gas had 80 – 85 mol % methane. Ethane, propane, butanes and hydrocarbons up to C14 were present. H2S and CO2 were present up to 6.0 mol%. The GHV was calculated from the gas composition and the energy content of the gas was derived from the flow rate and GHV. The laboratory data was compared with online analyzer and corrective actions were taken in case of any abnormality. The designing a special vaporizer and a customized gas chromatograph helped us to determine the export gas composition and its energy content accurately. The trend and variation of gas quality are correlated with feed gas supply and helped for adjusting process conditions to achieve operational excellence.

Novel/Additive Information

The measurement of gas composition and its energy is important for the seller and buyer. Any difference in the gas quality will have direct cost implications in the sale and it is important to standardize the sampling and analysis techniques to be best accuracy possible.
ASP Journey, from Pilot to Full Field Implementation in South of the Sultanate of Oman
Authors: Alkindi Abdullah , Mahrouqi Dawoud , Baqlani Safa , Llaguno Inaki , Mjeni Rifaat , Mahrooqi Majid , Nadeem Muhammed
Published: November 2018

The Marmul inverted five-spot pilot was successfully completed in 2016, demonstrating the effectiveness of Alkaline Surfactant Polymer (ASP) flooding in improving oil recovery from Al khalata reservoir. Earlier studies including core flood experiments, single well chemical tracer tests and small scale models indicated a potential of >10% of ASP incremental recovery over polymer flood and >20% over water flood. The pilot included a custom-built ASP facility, a first of its kind of scale squeeze treatment for high pH, state-of-the-art nuclear magnetic resonance (NMR) technology for vertical saturation estimates and very extensive sampling and surveillance programme. Overall, the pilot operation was very smooth and stable, achieving high facility uptime, good injectivity, accurate chemical dosing and met the surveillance target.

The estimated ASP incremental recovery from the pilot was over 30%, which increased the interest in a field-wide ASP injection. The acquired pilot results and operation experience were used to scale up the facilities design and assess the impact of key uncertainties observed in the field and the lab. Major factors influencing the recovery factor and project efficiency were analysed including chemicals formulation, facilities design and water treatment technologies. A mind-shift on the formulation cocktail and facilities design was proposed to improve the economic attractiveness of the process on large scale implementations. A phased development is proposed to de-risk subsurface and surface concepts which are different from those in the pilot.

This paper discusses in brief the pilot operation & performance, scaling up the results to full field implementation and key design considerations for a cost effective ASP project.