bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancing Rock Property Prediction from Conventional Well Logs Using Machine Learning Technique - Case Studies of Conventional and Unconventional Reservoirs
Authors: Negara Ardiansyah , Jin Guodong , Agrawal Gaurav
Published: November 2016

It is timely for our industry to introspect on ways for step improvement in the utility of the wireline and logging-while-drilling logs which remains central to any asset development. Interpretation is limited by our current understanding of rock-fluid physics in source rocks, which is still developing. The gap is clearly evident in unconventional source rock interpretation where approximations such as pseudo-Archie approach are used for saturation estimation. This paper presents the use of emerging knowledge in machine learning to demonstrate its applicability for improving the total organic carbon (TOC) estimation in an unconventional well and permeability prediction in a conventional well.

We have used the support-vector regression (SVR) technique, which is a new machine learning technique. Vast amount of logging data can be quickly processed using this technique. Limited core data is used to train the SVR algorithm. In this work, we first use the SVR technique to establish a correlation between conventional well logs (e.g., gamma ray, formation resistivity, neutron porosity, bulk density) and core measurements, thereafter building a rock property-prediction model as a function of well logs selected. Two field datasets from a South American well and a Mississippi Canyon well were selected to validate the method. Both wells contain a suite of logs and few core TOC and permeability data. Various combinations of conventional well logs were studied to check if the prediction accuracy can be improved.

The results of the two case studies reveal that the SVR technique provides accurate and reliable TOC and permeability predictions. We observed in the case study of TOC prediction that incorporating the carbon weight fraction log as an input, in addition to the conventional well logs, improves the TOC prediction because the carbon weight fraction log provides information about the amount of carbon, which eventually helps the SVR algorithm to learn better from the data. Meanwhile, for the case study of permeability prediction, we observed that the conventional well logs are sufficient to generate a good permeability prediction model. Additional logging data including the nuclear-magnetic-resonance (NMR) logging data do not improve significantly the prediction accuracy. In conclusion, SVR technique could be used to improve our log interpretation. This technique can be easily adapted to predict rock mechanical properties and especially useful for unconventional reservoirs where traditional models may not be applicable and new methods are still evolving. Such new data analysis technologies could optimize our logging service and core analysis planning.
Using Pressure Transient Analysis to Validate the Initial Hydrocarbon Composition and Improve Hydrocarbon Production Forecasting, Shown at an Example Rich Gas Condensate Field
Authors: Perdomo Enrique Alejandro , Clemens Torsten
Published: November 2016

In addition to the challenges of production forecasting of gas fields, gas condensate production forecasting needs to address effects related to condensate drop out in the reservoir.

To forecast hydrocarbon production from gas condensate fields, Drill Stem Tests (DST) and fluid sampling are required. For the example reservoir, an Equation Of State (EOS) model was generated using laboratory data. DSTs were performed and analysed for reservoir permeability, liquid drop out and velocity stripping near-wellbore.

In addition to pressure transient analysis, numerical simulations were performed using the EOS. The simulations indicated that the initial fluid composition determined from fluid sampling leads to a good match of the drawdown and build-up pressures, however, the pressure derivative could not be matched satisfactory for a reasonable set of relative permeabilities, velocity stripping effects and reservoir permeabilities.

Using the initial fluid composition as additional matching parameter lead to an acceptable match of the pressure derivative as well. This indicates that despite careful fluid sampling, the composition of the sampled fluid was not representative for the initial reservoir fluid.

In addition, simulating the well test revealed that the local equilibrium assumption in the numerical simulation might not always hold in the reservoir.

Gas and condensate production forecasts using the initial fluid composition of the sampling and the modified initial fluid composition after history matching were performed. The results indicate that for the example reservoir, the sampling derived initial fluid composition would overestimate the cumulative gas production by 4 %, underestimate condensate production by 9 %, overestimate condensate recovery factor by 17 %, overestimate plateau gas production duration by a factor of 9 and underestimate condensate production rate by 35 %. These differences might lead to different economics and development strategies (e.g. depletion versus gas recycling).
Tectonic Map of Abu Dhabi, UAE
Authors: Noufal Abdelwahab , Obaid Khalid , Ali Mohammed Y.
Published: November 2016

The study of tectonics deals with the broad architecture of the outer part of the Earth, the age, relationship, evolution of regional structural, deformational, and crustal features.

Subsurface geological maps are perhaps the most important tool used to explore for undiscovered hydrocarbons and to develop proven hydrocarbon reserves. However, the subject of subsurface mapping is probably the least discussed in Abu Dhabi, yet most important, aspect of petroleum exploration and development.

This paper presents the tectonic map for Abu Dhabi based on gravity, magnetic and seismic interpretations, along with describing the various elements, their controlling faults and their effect on basin development and also rationalizes previously published structural and tectonic elements to clarify the kinematic relations and naming of individual tectonic elements.

The method, which combines geologic, geophysical data in a comprehensive way, incorporates these data to simulate the interrelated effects of deposition and erosion of sediments and compaction, pressure, petroleum generation and multiphase fluid flow.

The tectonic map of Abu Dhabi distinguishes three principal tectonic cycles: (1) Precambrian cycles are interpreted using the magnetic data, as there are no wells that penetrated the basement in Abu Dhabi and the seismic is mostly covering up to Jurassic layers. (2) The Paleozoic cycle began with continental rifting about 550 Ma, followed by inundation of much of Abu Dhabi by shallow seas. This cycle ended with the opening of the Neo-Tethys, which caused the deposition of the Mesozoic Cycle. (3) The Mesozoic cycle represents the legacy of ocean opening and the rise and fall of sea level created the stratigraphic and structural features that would later trap vast quantities of oil and gas. On the tectonic map, major features record this history. Abu Dhabi is affected by at least seven major tectonic events, which are shaping the present structures. However, these events can be complicated by the salt-movements (halokinesis) in offshore areas of Abu Dhabi, which resulted in change of structural relief and faults/fracture characterization particularly for deep reservoirs.

Understanding of the kinematics and mechanics of the structures will highly impact the preservation of most of the hydrocarbons, and in turn reveals the new ventures to add reserves for Abu Dhabi.
Virtual Learning Environment Program in KOC VLE
Authors: Ashkanani Jenan
Published: November 2016

The use of VLE has been increased, because of the Technology Tsunami. The KOC Geo-Portal (SAHALA) has many applications, tools, reports, customized tasks, workflows and so on, which needs further training or familiarization on demand for every user. Most of the users need to have a training on many applications, thus huge allocation of the time (man days/employee). The conventional (dedicated) training leads to considerable time loss which affects the performance of the whole company. This is why we initiate this way of training (on Demand/On the Job) using the new technology to enable the user to be familiar or get training on his specific points even within the application itself or different application.
To the Edge and Back: Building Relationships with a Marginalized Community in Iraq
Authors: Bourtman Ilya , Al-Mudhaffar Hassan , Boyd Christopher , Skerritt Brendhan , Abrahams Nicholas
Published: November 2016

A consortium of international and national Iraqi oil and gas companies took operatorship of the Qarmat Ali industrial water-treatment plant, which is critical for oil production, in Southern Iraq in 2013. Due to community protests, operations shut down for 6 months as the consortium strived to find the best way to work with the community. This paper explores how the consortium achieved success with the community through constructive engagement and proactively responding to community expectations for social investment while addressing the social impacts of operations.

The paper describes how the consortium developed and implemented a community relations plan, in a high-risk and conflict-affected area. From the very start of operations the local community, accustomed to using force to raise concerns, continued to use force and construction was frequently interrupted by stand-downs, gunfire, rock throwing, violence, and intimidation.

The consortium established a tri-sector partnership between the consortium, civil society and the government to broker an agreement with the community, allowing the consortium to return to work. Each party had a critical role to play in establishing agreed performance goals, consultation processes, monitoring and reporting systems and collaborative activities. As the consortium delivers on its commitments, the partnership continues to build trust and cooperation, reward constructive action for mutual benefit, and improve the health, well-being and livelihoods of thousands of individuals and their families in Qarmat Ali.

The findings of the paper can be used as a reference point for constructive engagement between companies and communities in high-risk and conflict-affected areas. It uses case studies to outline a structured approach to developing tri-sector partnerships to find answers to complex problems and provides a set of lessons learned.
New Process for Complete Removal of H2S from Gas Streams and Conversion to Elemental Sulfur
Authors: Ayasse Conrad
Published: November 2016

Objectives/Scope: The objective of the paper is to highlight an advancement in natural gas sweetening. In particular, the paper will show how the Sulfa-Niltm Process dramatically reduces the operating costs and energy demand of natural gas sweetening, and how the Process can also integrate with existing Amine/Claus plants to boost capacity and completely eliminate sulfur species emissions.

Methods, Procedures, Process: The presentation will be structured in 3 parts. The first part will briefly outline the current state of the art in natural gas sweetening, the second part will explain the Sulfa-Niltm process and the economic and environmental benefits it can bring, and the third part will explain the applicability over a wide range of gas treating volumes, filling voids in the present alternatives.

Results, observations, Conclusions: Sulfa-Nilta is a new Direct Oxidation (DO) gas sweetening process that utilizes only solid catalysts and eliminates all sulfur emissions. The process is very energy efficient because the required energy is produced within the process by the exothermic DO reaction. No steam is required. Because of the small amount of oxygen that is typically required, the oxygen can be supplied with air and so an oxygen plant is not required, reducing capital anf operating costs. Likewise, liquid amines and water are not employed. Hot gas from the DO reactor is used to strip absorbed H2S from solid- particle absorbent in the re-generating absorption column while a second column is completely removing H2S from the treated stream. The presentation will provide the plant schematic and explain the benefits of this transformative technology.

Novel/Additive Information: The Process is entirely novel, having been piloted on an in situ combustion field gas in Canada. The Presentation will enhance the understanding of the audience members of gas sweetening in general and the Sulfa-Niltm Process in particular, and provide a new alternative in treating sour gas.
Application of Real-Time Geomechanics on a Horizontal Well
Authors: Hamid Osman , Hall-Thompson Bryan , Omair Ahmed , Ahmed Sajjad , Ahmed Mujahid
Published: November 2016

Mud weight optimization is a critical driver to successfully drill horizontal wells. Historically, using inadequate mud weight while drilling horizontal wells has proven to be cost effective when it is intended to place multistage fractures in tight formations. The typical problems encountered in such wells are tight spots, requiring hard reaming which sometimes lead to stuck pipe and bottom-hole assembly (BHA) loss during borehole events. It is of paramount importance in drilling that correct mud weight be used from the start and during each section. Subsequently, based on well behavior/response, mud weight is optimized to an optimum range during the course of drilling.

In subsurface areas where rock behavior varies progressively with depth, along with constantly changing regional and local stress regimes, mud weight optimization is one of the tools that lead to successful drilling of wells to depth (TD). Geomechanical characterization of the target formations provides optimum mud weight window to drill along planned trajectory with minimum wellbore stability related issues.

This paper describes the construction of a 1D Geomechanical model and wellbore stability (WBS) analysis performed to determine the mud weight window used to drill multiple sections in a horizontal well for a new offshore field. The paper will further discuss how an integrated drilling and geomechanics approach was utilized for mud weight and drilling/tripping practices optimization, which resulted in successful drilling

This study is a perfect learning example how to use the various surface and downhole data in real-time and integrate it with a pre-drill geomechanical model to forecast and avoid wellbore stability/drilling problems by optimizing mud weight window. The value of geomechanical study is not only limited to drilling the well to TD, in fact, updated information can be further utilized for finalizing completion strategy. This paper also describes how updated stress profile in 1-D geomechanical model was used to characterize the reservoir for multi-stage fracturing.

A comprehensive geomechanics study incorporating offset wells analysis, core data, mini-frac data and formation pressure points resulted in the following starting mud weight recommendations for each section of the horizontal well in tight formation:
Asset Interface Management System
Authors: Naqbi Sulaiman Al , Shokri Samin , Maloney Kelly
Published: November 2016

Achieving operational efficiency has always been one of the top challenges in managing brownfield projects. Considering today's low oil prices, operators are more focused than ever on improving current operations to increase their return on investment. In brownfield projects, there are a significant number of interactions between the expansion and maintenance projects and the existing facilities. Efficiently managing these interactions can greatly improve the performance and resilience of the assets. While interface management has been widely adopted for the design and construction phases of capital projects, its impact and application on brownfield projects has not yet been addressed.

This paper introduces specific approaches on how the concept of interface management can be applied to brownfield projects to improve their operational efficiency. For this purpose, this paper first introduces the business requirements of operational efficiency and its correlation with interface management principles. In addition, a communication strategy from the organizational point of view is introduced to enable formalized communication between projects and facilities. Finally, workflow driven approaches are developed to: Identify interfaces between the existing assets and projectRecord interfaces in a centralized interface register that is available to all appropriate participants through a web-based applicationManage interfaces by providing a communication framework to enable parties to agree on the operation-related deliverables and the required datesRecognize the high-risk interfaces and escalate them to the project risk register and business risk register

The main purpose of the Asset Interface Management System is to assist operators in minimizing business interruption and ensure smooth commissioning and handover through: Increase visibility on the interfaces between projects and assets, and their responsibilitiesEarly identification of potential issuesImprove decision making on outage optimization by having access to real-time informationEnsure effective information transfer between all parties by having centralized information repositoryReduce time spent updating different registers and searching for information

Considering the complexity of brownfield projects and the significant required information transactions between operating facilities and ongoing projects, managing the interfaces between the active participants and coordinating the deliverables is critical. Developing a formalized and workflow-based Asset Interface Management system is a novel approach to assist operators to take control over their operating facilities, optimize shutdowns, and eventually improve operational efficiency of the asset.
Advanced Structural Reassessment of Fixed and Floating Offshore Structures
Authors: Raval Dr. Hirenkumar
Published: November 2016

The procedure of rationalization of Risk Ranking of Offshore Structures (Fixed and Floating structures) by applying Numerical Finite Element Analysis (FEA) in Qualitative and quantitative Structural Risk Assessments in SIMS (Structural Integrity of management systems) is evaluated in this paper. It is demonstrated by providing examples of how in philosophy based Risk Assessments, Advanced techniques like FEA can benefit traditional analysis. Subsequent impact of the outcome of Risk assessments can then be assessed.

Traditional structural risk assessment techniques (philosophy based) exclude the consideration of detailed and accurate FEA output such as component/principle stresses, crack growth rate, damage assessment, numericalstress concentration factors (SCF's), non-linear deformation characterization, complex geometries, etc. FEA inPhilosophy-based risk assessment provides realistic predictions of structural performance, strengtheningthe traditional techniques for cost effective and time consuming construction activities,which are used for life extension of brownfield structures.

The failure mechanisms modelled in FEA are fracture, cracking, fatigue, deformation and plastic collapse. The process involves data collection extracted from existing drawings, history, calculations, inspections, etc., followed by structural performance evaluation by developing 3D modeling and meshing structural elementsto perform FEA. The FEA outputis then used to produce a highly sophisticated and accurate analysiswhich is used to inform the strategy and program for improvement.

The Paper provides the background, procedure and benefits of using FEA outputs in risk assessment for Asset replacement plan, assurance and strategy. Structural parts of Assets integrity are discussed in this paper and so called SIMS. Asset replacement plan is followed by remnant life assessment (RLA) study includes the principal that seeking to fully make use of the existing offshore structures, latest methods for inspection, maintenance and remedial works, Identify the impacts of remedial projects in Capital and operating expenditure and link all existing Development, Engineering, Maintenance and Integrity studies and identify where additional studies are required.
Effects of Pore Pressure and Two-Phase Flow on Permeability Estimation of Reservoir Rock
Authors: Alkafeef Saad F. , Hadibeik Hamid , Azari Mehdi , El-Daou Mohamed K.
Published: November 2016

Various methods have been used within the industry to estimate rock permeability at various stages of reservoir exploration and development. As reservoir pressure declines with production, multiphase flow occurs in the formation requiring special handling of the permeability calculations. This paper provides a new laboratory experiment to quantify effects of pore pressure and two-phase flow on permeability estimation from buildup (BU) data in sandstone cores.

A 1-m long Berea sandstone core was used with a 2-in. diameter, 18% porosity, and 50-md permeability. Pore pressure was varied in 11 experiments from atmospheric to 500 psi with a net-confining pressure of 1,000 psi. A compressible fluid (brine with air) was injected through the core at a constant rate while a backpressure regulator maintained pore pressure in the flow studies. Fluid compressibility was also calculated at different pore pressure values. Experiments were conducted under both constant flow rate and constant producing pressure. After reaching steady-state flow, the outlet valve was shut-in to initiate the pressure BU experiment in the core. Pressure-BU permeability was calculated at different flow rates for various reservoir pore-pressure values. The effective permeability was calculated at various flow rates for pressure BU cases for different applied pore pressure values. The calculated BU permeability values were trending lower with increasing pore pressure. The long core used in this experiment provided enough contact time for the two-phase flow to reach to steady-state condition. Air-phase flow was dominant at early stages of less than 100-psi pore pressure before air bubbles dissolved in the liquid. Single-phase flow effect reduced permeability 19% when pore pressure was increased from atmospheric to 100 psi. Fluid flow in the core sample of more than 200-psi pore pressure became single-phase flow. Permeability declined 10% when pore pressure was increased from 100 to 300 psi. From 300 to 350-psi pore pressure, a 5% increase in permeability was observed because of rock expansion. The declining trend in permeability vs. pore pressure continued afterwards due to decrease in liquid compressibility.

Stresses, pore pressure, and fluid phases in a core sample change when brought to the surface from downhole conditions. It is important to consider effects on permeability estimation from well logs vs. laboratory experiments. Laboratory permeability should always be corrected to take into account the changes from downhole to surface conditions. This paper provides a step forward to overcome such challenges with a new method that quantifies the effect of pore pressure, two-phase flow, and rock and fluid compressibility on permeability estimation.
Treatment of Legacy Oil Based Mud OBM Drill Cuttings and Sustainable Use of Recovered Materials
Authors: AlBeshr Khalid , Al Hammadi Saud , Reddy Vijaya Bhaskar , Ali Etehad Abou , Mohammed Tariq Hasan , Chauhan Deo Kumar
Published: November 2016

In 1990's due to lack of treatment facilities, Oil Based Mud (OBM) drill cuttings generated from drilling operations were dumped in an interim waste storage facility located in prime industrial area. Considering the complex nature of hazardous waste on land, treatment costs and future environmental liability involved, company evaluated number of treatment options and based on techno-economical and legal assessment, selected option of transferring OBM cuttings stored in pits for treatment using Thermal Desorption process.

Thermal desorption is recognized as best environmental remediation process that uses heat to increase the volatility of contaminants to remove hydrocarbons and water from the solid matrix. The storage pits were remediated by removal of bottom contaminated soil upto 1% Total petroleum Hydrocarbon (TPH) and HDPE Liners. The treatment of legacy waste including clean-up of the old pits enabled site decommissioning for future industrial expansion in the area. The successful completion of project resulted in considerable economic benefit compared to other competent treatment costs and reduced environmental liability from legacy wastes. The paper presents the methodology adopted for treating OBM legacy waste and clean up of the site confirming to regulatory requirements.
Confronting the Simulation of Fluid Flow in Naturally Fractured Carbonate Karst Reservoirs
Authors: He Jie , Killough John E. , Gao Sunhua , Fadlelmula Mohamed M. , Fraim F. Michael
Published: November 2016

Flow simulation in carbonate reservoirs presents many challenges due to the frequent occurrence of vugs and natural fractures therein. In conventional reservoir simulation practices, fluid flow in vugs and fractures is usually assumed as Darcy flow, and permeability values are estimated for vuggy regions and fractures. Although such estimations are often accomplished in reasonable ways, no physical or mathematical basis exists for them, and even the assumption of Darcy flow itself is questionable.

In this paper, we propose a novel workflow for the simulation of fluid flow in naturally fractured carbonate karst reservoirs. The workflow is based on simulation results of a single-phase transient Brinkman model, which provides the correct and complete description of the coupled flow in vuggy and fractured reservoirs by unifying Stokes flow in vugs and fractures with Darcy flow in the rock matrix. The new workflow proceeds through an iterative procedure by increasing the permeability values of vugs and fractures without the disadvantages of accurately estimating them, and attains the final simulation results when a convergence pattern is observed.

The novel workflow is implemented and compared with the conventional approaches in commercial reservoir simulators. The workflow is first applied to single-phase flow simulations in a fine-scale 3D geological model which is generated using the multiple-point geostatistical modeling technique, and then extended to immiscible two-phase flow and other multi-phase cases. Simulation results show that in most cases our new workflow yields higher production rate predictions than conventional approaches. This is due to the fact that the permeability values of vugs and fractures estimated by conventional methods are usually lower than the permeability values required for the iterative convergence of the new workflow. The results also have further implications on the history matching process that more focus should be put on fracture geometry, i.e. fracture width and half-length, since the use of fracture permeability alone has lost its physical meaning in the novel workflow according to the Brinkman equation.
People Development Framework
Authors: Mahmoud M. A.
Published: November 2016

This work describes ADCO's Discipline Development Frameworks (DDF); which helps the implementation of a Competency based approach to employee development by grade and discipline across all assets. In addition to ensuring the consistency of skills across ADCO, such Development Frameworks provide structured development programs and monitoring mechanisms, thus enabling a one ADCO Vision. Such effort informs and encourages career paths, and a "lifelong learning culture" through this master guide referred to as the "Discipline Development Framework (DDF). This DDF is therefore, a comprehensive career development framework for all employees, which ensures a high caliber workforce.

The process of the DDF starts with the refinement of ADCO's Career Ladders. Following this detailed identification of appropriate skills levels, the DDF is developed by Subject Matter Experts (SMEs) in the Discipline. This is double checked internally, refined and benchmarked with other OPCOs and the Industry at large. Following this, the DDF emerges; identifying core competencies, Support, Behavioral and all related Soft Skills essential for all disciplines, job grades. The skill levels (Awareness, Knowledge, Skill, Mastery and Expert Levels) for each are highlight. Mixed and blended development initiatives are also identified.

An outcome is therefore a master career guide document that provides clarity to employees, ensures consistency of development within ADCO, minimum standards and transferability by grade and discipline across all assets and functions. It also aids morale and increases employee retention since there is the knowledge of clear progress and strategic support for such. The DDF also ensures a centralized and harmonized approach to learning & development.
PTA and Well Performance Assessment of Dry and Liquid Rich Gas in Unconventional Tight Sands: A Middle East Case Study
Authors: Al-Shawaf Ali , Al-Momen Mohammad , Issaka M. B. , Filipi I. , Lewis C.
Published: November 2016

Saudi Aramco is actively appraising the numerous unconventional shale and tight sand opportunities located across the kingdom of Saudi Arabia. The early phase of the unconventional gas program in the company has been directed towards exploration data gathering activities through drilling, coring, open-hole logging and completion of shale and tight sand gas resources. Due to the ultra-tight nature of these reservoirs, several vertical and horizontal wells have been drilled and completed with multistage hydraulic fractures to be able to produce them. Initial flow back tests, in addition to long term pressure build-up, have already been conducted on some of these wells, the analysis of which will help to characterize and better understand these tight hydrocarbon reservoirs.

This paper discusses the results of pressure transient analyses and modelling performance of two unconventional tight sand wells. An Integrated workflow was developed for reservoir characterization and fluid flow modeling using well test analyses and a simulation tool designed specifically for unconventional reservoirs. Post fracture flowback data along with available petrophysical interpretation, geological and geophysical analyses and 3-D hydraulic fracture models were used to build and calibrate single well numerical models. For the purpose of comparison, two wells were selected: one from a dry gas reservoir, while the other was from a rich gas-condensate reservoir.
Metrology of a Dataset Acquired with an Optical Fiber in a Horizontal Well
Authors: Leclercq Marion , Hubans Christian , Suaudeau Eric
Published: November 2016

Acquiring a seismic profile data in a well using conventional geophone technology requires sensors to be lowered down the well. Unfortunately it is expensive and it involves the production interruption. The Distributed Acoustic Sensing (DAS) is a known alternative to this system for vertical seismic profiles, with the benefit that it can stay after the acquisition, even while producing. The quality of this type of measurements for reservoir monitoring is studied here.

In 2014, several lines were shot around a horizontal well in a carbonate area in Middle East with the DAS technology (walk above and lines in different directions from that of the well, some of them shot several times, some of them while producing, some with the production shut down). First this dataset was used to provide a 2D image of the reservoir below the horizontal part of the optical fiber. It also enabled a comparison of the measurement while producing or not and gave a dataset for repeatability evaluation.

Unfortunately, this dataset is not usable as a VSP for the vertical part of the well, due to coupling issues and directivity of the signal. Nevertheless, in the horizontal part of the well, dense spatial sampling opens the door to detect very small details in the reservoir, below the conventional seismic imaging capacities. However, separating the up-going wavefield from the down-going wavefield is challenging.

The comparison of the repeated lines shows whether this technology is satisfying in terms of repeatability for 4D surveys or not. It is also possible to measure the difference of the direct and reverse paths which are both recorded. Since the equipment varies along the well, it gives information about the quality of the coupling, for e.g. with or without casing. Finally, it shows whether it is necessary or not to shut down the production while acquiring the dataset.

It is already known that optical fibers can be used for VSP and reservoir imaging, but this experiment is the perfect dataset to evaluate the quality and to extract all the potential of this type of measurement especially in terms of reservoir monitoring. Thanks to the lessons learnt from this experiment, it will be possible to optimize the acquisition design of future surveys to improve the signal quality.
Innovative Wireline X-Ray Diagnostic Service Reduces Risk During Well Interventions: A Case Study
Authors: Spannuth Melissa , Achihai Radu , Angel Juan , Gunn Spencer , Johns Jack , Singleton John
Published: November 2016

During well intervention activities, one of the biggest challenges faced is uncertainty about the downhole hardware. Carrying out interventions without understanding the state of downhole equipment can be time-consuming, expensive and ultimately unsuccessful. There are several diagnostic techniques available to assess the state of downhole hardware, but none offer an efficient and reliable solution, particularly if the well fluid is opaque. Recently, an X-ray based wireline tool was introduced for providing downhole imaging, regardless of the well fluid. We will present a case study in which this new tool was run in a brine-filled onshore gas storage well in the Netherlands. In this case, the X-ray images provided measurements of the inner- and outer-diameters of a coiled tubing disconnect to millimeter-scale accuracy. These X-ray images and measurements verified the operator's fishing plan and they successfully retrieved the fish on the first attempt. In general, the quick and reliable visualization of downhole objects provided by X-ray imaging reduces the uncertainty and concomitant risk associated with well interventions, resulting in a higher success rate, less downtime, and lower cost.
An Integrated Reservoir Modelling and Evolutionary Algorithm for Optimizing Field Development in a Mature Fractured Reservoir
Authors: Sambo C. H. , Hematpour H , Danaei S. , Herman M. , Ghosh D. P. , Abass A. , Elraies K. A.
Published: November 2016

In upstream oil and gas industry, infill drilling is a vital practice to increase the productivity as well as recovery factor of hydrocarbons. It concerns with the implementation of accurate and reliable reservoir models in order to evaluate the reservoir behaviour response effectively and be able to predict its future performance. Given the nature of reservoir response of naturally fractured reservoirs, optimal well locations are extremely important to ensure the economic viability of infill drilling programs. However, optimal placement of infill wells in fractured fields is challenging.

In this study a reservoir modelling-optimization workflow for fractured reservoir is developed. Firstly, an integrated static and dynamic reservoir model has been developed and validated using history matching process. For the purpose of maximizing economic recovery, an infill well placement optimization project has been considered for this field to find the best possible locations of infill wells, two different optimization approaches were adopted and implemented on reservoir model. The first method is an exhaustive method which uses the concept of design of experiment to search all grids available in the model in order to locate the best possible well locations. The second method is automatic optimization using Genetic Algorithm. That depends on the principle of natural selection as proposed by Darwin

The genetic program was coupled with the reservoir flow model to re-evaluate the chosen wells at each iteration until obtaining the optimal choice. The proposed location of wells has improved Net Present Value (NPV) by + 10% higher than the base case without infill wells. Examining two different optimization approaches used in this work, the genetic algorithm program gave results similar to the results that were obtained by an exhaustive method with much less computation time which is a great issue mainly for large size fields or fields which possess condensate gas and require the use of compositional simulators.
Redesigning Completions to Overcome Downhole Flow Assurance and Corrosion Impacts in a Giant Field, Offshore Abu Dhabi.
Authors: Aouda Abdel Hakim , Daghar Tariq al , Odeh Nadir , Morrow Timothy , Troshko Andrey
Published: November 2016

A new generation of sophisticated wells are to be drilled in a giant offshore field in Abu Dhabi. These extended reach wells will reach and produce remote areas of the field from artificially built islands. The first maximum reservoir contact (MRC) pilot well was drilled successfully with 20,000 ft total depth and a 10,000 ft producing interval completed with inflow control devices (ICDs). The well started producing dry oil at reasonably high flow rate and uniform contribution from each ICD compartment. After a relatively short period of dry oil production water break-through occurred and started causing unexpected downhole flow assurance concerns, especially at the locations of the ICDs. Production logging along with caliper data showed severe corrosion around water producing ICD nozzles and high gamma ray readings in the water producing intervals, suggesting that scale had precipitated behind pipe either in the near wellbore rock (believed to be unlikely based on the history of scale precipitation in the field) or on the outside of the completion (thought to be more likely).

An investigation was launched to determine the cause of the corrosion around the ICD nozzles and improve understanding of the influence of ICD flow dynamics on scale deposition and material corrosion, with the objective of developing a suitable mitigation method for scale and corrosion in future MRC/ICD wells. The study results showed that high wall shear stress developed in and around the water producing ICD nozzle area are at the origin of the corrosion in the pilot well, and that low-to-moderate wall shear stresses on and around the wire-wrapped screen sections of the ICDs could be the cause of the scale deposition. Consequently, the completion design for future wells with ICD completions has been revised to mitigate the risks of flow induced corrosion.

This paper will present results of the laboratory study into the influence of ICD flow dynamics on corrosion rates and mineral scale precipitation and discuss strategies for mitigating both concerns via the design of the ICD.
Water Alternating Gas WAG Optimization Using Tapered WAG Technique for a Giant Offshore Middle East Oil Field
Authors: Khan Mohammad Yunus , Kohata Akihiro , Patel Harshad , Syed Fahad I. , Al Sowaidi Alunood K.
Published: November 2016

An extensive study was conducted to evaluate enhanced oil recovery (EOR) potential of a giant, offshore, Middle East oil field. The subject field contains a very large reservoir with light oil and has a long production life extending beyond 100 years. Primary recovery began in 1968. The field has been under water flooding with pattern injection since 1982. In order to sustain oil production and increase the ultimate recovery, EOR will likely be implemented at some future time. Miscible gas injection with a water-alternating-gas (WAG) injection scheme is considered to be the most suitable method among the currently available technologies. The WAG injection process is a well-established EOR technique with several successful field applications around the world. This paper describes Water Alternating Gas (WAG) Optimization through Tapered WAG technique (more gas is injected earlier and then reduced over time) and its impact in the subject reservoir.

The primary focus of this study is to estimate the benefit of miscible WAG EOR for the subject reservoir. Finely-gridded, compositional, mechanistic, 2D cross-sectional models as well as 3D sector models were constructed and used for the evaluation. One non-hydrocarbon (CO2) and two hydrocarbon ("associated" and "lean') miscible gases were tested as injectants. The study encompasses different geological areas in the same reservoir and addresses key design parameters including well spacing, optimal WAG operating scheme, and timing of WAG application. In this paper, we will focus on formulation of optimal CO2 WAG operating scheme.

As part of optimization of the miscible WAG application, a concept of Tapered WAG was tested. A typical WAG application consists of injection of water followed by gas injection. Each cycle of water and gas injection is of fixed duration. In Tapered WAG concept, the durations of gas injection varies with longer gas injection earlier and reducing with progressive WAG cycles. Such miscible WAG application, termed as Tapered WAG, was found to be more effective than the Uniform WAG application where the water and gas injection cycle durations are same.

The Tapered WAG technique reduces response time i.e. oil bank arrives earlier. It also uses gas injection more efficiently, i.e. produces more incremental oil per unit of injected gas. Findings were applicable to both a homogeneous (low and relatively Uniform perm) and heterogeneous (high perm with high perm streaks dominant) areas of the reservoir.
Successful Application of a Mechanistic Coupled Wellbore - Reservoir Dynamic Simulation Model to History Match and Plan Cleanup Operation of Long Horizontal Wells
Authors: Syed Fahad I. , Al Saadi Sami , Khedr Osama , Khan Mohammad Y. , Yusuf Rahel , Thakur Kapil K.
Published: November 2016

Cleanup of an extended reach horizontal well with maximum reservoir contact is challenging especially when a large amount of mud is lost into the reservoir formation. During the well cleanup operation, not only the existing completion fluid needs to be unloaded from the wellbore, but also the drilling fluid that invaded into the formation needs to be back-flowed to minimize formation damage and regain well's capacity.

This paper describes the successful application of a mechanistic wellbore model coupled with a near wellbore dynamic reservoir simulation model to history match clean-up operation of a maximum reservoir contact (MRC) well. The coupled model was simulated for a sequence of events starting from mud loss during a stuck liner incident, followed by subsequent well cleanup using coiled tubing unit (CTU) with nitrogen to recover large amount of drilling mud invaded into the pay zone, to PLT run along the long lateral for assessing flow profile. The PLT flow profile was used to calibrate the reservoir model in terms of skin factor, matrix and relative permeability.

Given the transient flow nature of well unloading operation, the coupled model is best suited to simulate oil and mud movement from reservoir through porous media, into the wellbore together with nitrogen, and then being lifted to the surface with the changes in PVT properties (density, viscosity, solution GOR). The coupled transient multi-phase flow model is able to achieve good history match on mud invasion into the wellbore reservoir region, thus providing good insight on the key operational and reservoir parameters influencing cleanup efficiency. The tuned model predicts the total cumulative liquid, oil and water phase volumes with fair accuracy. This study shows the importance of transient dynamic simulation in history matching and predicting well cleanup and the recovery of the invaded mud from the formation. The key benefit from the study is that the model is a very useful tool for designing the most economical and efficient cleanup operation in terms of total operational/rig time, injectant selection and the volume, as well as the operating parameters.
Optimizing CO2 Floods Using Rate Control with Smart Wells Under Geologic Uncertainty
Authors: Sharma M. , Taware S. V. , Datta-Gupta A.
Published: November 2016

Carbon dioxide flooding (continuous or WAG) is a proven and effective EOR technique resulting in improved oil recovery in various types of reservoirs. However, the complex displacement mechanisms in CO2 flooding, in particular adverse mobility and gravity segregation can reduce its effectiveness. It has been demonstrated earlier that by adjusting the well rates, we can manage the flood front and improve the sweep during waterflooding. In this paper, we present the application of rate optimization to CO2 flooding in order to maximize areal and vertical sweep, and minimize CO2 recycling by delaying CO2 breakthrough.

Field-scale rate optimization problem for CO2 EOR processes involve complex reservoir models, production and facility constraints and geological uncertainty. We propose an efficient approach for computing optimal rates for CO2 flooding with application to smart wells completed with inflow control valves (ICV). The approach is based on equalizing the arrival time of flood front at the producers within a selected sub-region to maximize the areal sweep efficiency under hierarchy of production and facility constraints. An additional ‘norm’ constraint on the arrival times is also included to achieve high viscous-to-gravity ratio (VGR) to minimize gravity segregation. The ‘optimal’ strategy is decided based upon the trade-off between maximizing sweep and accelerating production. We use streamlines to compute the analytical sensitivity of arrival times with respect to injection/production rates. Analytical gradient and Hessian of the objective function are also derived, making the approach computationally efficient for field-scale applications.

The approach has been demonstrated using a synthetic 2D example and a 3D benchmark field case. The results clearly demonstrate that rate optimization can improve sweep, delay CO2 breakthrough and increase oil recovery for the same amount of CO2 injection. In addition, we demonstrate the potential of our approach for WAG flooding in the 3D benchmark field case. We incorporate geological uncertainty via a stochastic optimization framework based on the combination of the expected value and variance of a performance measure from multiple realizations.