bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Model for Predicting Productivity Index Pending Water Breakthrough in Oil Field
Authors: Yang Renfeng , Zhang Jinqing , Yang Li , Jiang Ruizhong
Published: November 2015

It is believed that the productivity index (PI) of vertical, horizontal, hydraulic fractured, or multilateral wells is considered to keep stable before water breakthrough. However, PI changes and presents different characteristics several months before water breakthrough, especially pending water breakthrough. If no measure is taken, the production rate will not keep stable. This condition has not aroused enough attention. Furthermore, there is currently no model for predicting which could reduce production forecasting accuracy.

Based on Buckley-Leverett equation, material balance equation and Corey-type functions for relative permeability, a new model for predicting productivity index was derived. It considers oil/water viscosity ratio, relative permeability, permeability, porosity, net pay, water injecting rate, well space, etc. Complete equations are provided and the method is described in detail to permit readers to replicate all results.

The most significant new finding is that the characteristics of productivity index pending water breakthrough depends on the relative filtration resistance changing rate with calculating the derivative of filtration resistance function. The productivity index monotonically decrease pending water breakthrough in volatile oil reservoirs, especially when the oil viscosity is less than water, while it monotonically increases in heavy oil reservoirs. Moreover, there are breakpoints in some medium viscosity reservoirs. It is found that the key influence factor is a function related with relative permeability and oil/water viscosity ratio. Based on mathematical analysis of mechanics equation and more than 100 simulation runs, it can be concluded that the permeability, porosity, net pay, heterogeneity, water injection rate, well pattern, and well space don't change the rules, but influence the initial value and change rate. The proposed model has been validated using production data from many oil wells and several reservoirs with a wide viscosity range.

The novelty of the new model is that it can be used to quickly and accurately predict production rate pending water breakthrough without involving time consuming simulation technique. Corresponding measures could be taken in time when PI begins to change in order to improve the development efficiency.
Contribution of Fluid Cleanliness to Smooth Gas Plant Commissioning and Start-up at GASCO's Habshan 5 Integrated Gas Development (IGD)
Authors: Trifilieff Olivier , Gardin Alessandro , Tecnimont Maire , Al Maskari Saleh Mohamed
Published: November 2015

The Habshan 5 Process Plant (H5PP) is one of the four packages that constitute the GASCO Integrated Gas Development (IGD) Scheme. The JGC-Tecnimont Joint Venture was awarded the EPC phase. The project was completed on schedule within 50 months, and the plant was successfully handed over in September 2013. One of the key contributions to the smooth plant commissioning and start-up is the choice made by the JGC-Tecnimont JV and GASCO for fluid contamination control. In the form of liquid aerosols and solid particles, contamination in process gases and liquids represents a major contributor to operation issues in gas processing units, such as foaming. A strategy for fluid cleanliness control was implemented to keep fluids clean: supported by PALL from the design phase, the specification and the selection of filter and coalescer technologies at critical contaminant-challenged locations were made carefully. Appropriate activities during prefabrication, precommissioning and commissioning phases were implemented to minimize contamination from installed equipment. Performance tests carried out at start-up on the main coalescer and filter equipment confirmed that clean process fluids were delivered and compliant separation efficiencies were achieved.
Geomechanical Heterogeneity Diagnosis of Carbonate Reservoirs in Onshore Abu Dhabi
Authors: Sirat Manhal , Noufal Abdelwahab , Simon Janelle , Zhang Xing , Subbiah Surej Kumar
Published: November 2015

The main objective of this paper to is to discuss the recent finding on the formation anisotropy and lateral heterogeneity in the different hydrocarbon fields of onshore Abu Dhabi. The study was focused on Thamama and Wasia groups, mainly related anisotropy and spatial heterogeneity of the geomechanical poperties for reservoir characterization. This would have an impact on the stress variation and the definition of potential "sweet spots" for well placement optimization and identification of suitable completion methods.

The 1D Mechanical Earth model (MEM) is a description and quantification of rock elastic and strength properties, in-situ stresses and pore pressure as a function of depth, referenced to a stratigraphic column. The available wireline logs of several existing wells, including the compressional and shear slowness, stonely, bulk density, and gamma ray were used to compute log-derived elastic parameters, strength properties and stress components. Rock mechanics laboratory core plug tests were performed to calibrate the log-derived mechanical properties. Anisotropic modelling was applied to understand the anisotropy in elastic properties and horizontal stresses.

Integrating the 1D-MEMs indicate that Onshore Abu Dhabi Geomechanical properties (elastic and strength) and in-situ stresses vary laterally and vertically. Further, several mechanical layering and horizontal stress anisotropy can be identified. These results imply that the Wasia and Thamama reservoirs are susceptible to different fracturing mechanisms. Hence different fracture and faults sets can be predicted within the highly anisotropic deformation zones.

These findings significantly impact the exploration play concepts, where lateral variations are anticipated. This also applied to the production and development, where the stress barriers control the stimulation and completion strategies.
Towards Predicting Multi-Phase Flow in Porous Media Using Digital Rock Physics: Workflow to Test the Predictive Capability of Pore-Scale Modeling
Authors: Masalmeh Shehadeh K. , Jing Xudong , Roth Sven , Wang Chenchen , Dong Hu , Blunt Martin
Published: November 2015

Digital rock physics (DRP) has gained significant development in the last decade. At its current state, in general DRP cannot yet reliably a priori predict two-phase fluid flow properties without knowledge of wettability/contact angles, especially for non-water-wet rock. Prediction of two phase flow properties becomes even more challenging for carbonate rocks which are rarely water-wet and have a complex pore structure. The two main challenges are to model pore geometries and size distributions at a representative elementary volume (REV) and the representation of wettability. Advances in micro- and nano-CT imaging and computer capability may help solve the first challenge, although the translation from images to model input parameters and REV consideration remains a research topic. However, wettability distribution (as an input parameter) cannot be predicted and will remain to be the most significant problem in attempting to predict multi-phase flow properties.

In this paper, we study the use of pore-scale imaging and modeling (DRP) to predict relative permeability curves. We recommend that we should shift focus from a priori prediction of fluid-flow properties, to instead investigate how much experimental special core analysis (SCAL) and imaging data is required as input to calibrate or constrain the model before computing two- or three-phase flow properties for field applications. In this paper we will focus on two main issues: 1- The role of DRP and how it can complement SCAL data, 2- How can we improve the predictive capability of DRP through the use of imaging data combined with benchmarking and tuning to match core-scale measurements. A case study and a recommended workflow to integrate DRP in the whole SCAL procedure is presented. In the case study, the measured primary drainage capillary pressure is used to modify the pore size distribution inferred from multi-scale imaging, while the waterflood capillary pressure is used to estimate contact angle. Then waterflood relative permeability is predicted and compared to experimental measurements: the water relative permeability lies within the range of measurements made on four core samples, while the oil relative permeability is over-predicted.

The core samples used in the study are carbonate samples; however, the workflow described in the paper applies to both sandstone and carbonate rock. The workflow relies on using DRP as a complementary and integral technology to conventional SCAL that might help to reduce cost and fill some gaps instead of replacing SCAL.
Realization of Over Half a Billion USD Worth Centrifugal Compressors for Mega Oil & Gas EPC Projects
Authors: Remy Philippe , Mossolly Mounir
Published: November 2015

Mega oil and gas projects have become more frequent as scale has increased and as resources in increasingly remote locations are produced.

Despite the harsh operating environments, the size and complexity of these projects are unprecedented. Contractors must; and are still expected to deliver their commitments as per the specifications, within budget and on-time. Technological novelty is avoided where possible but in cases such as the one discussed in this article it must be managed.

When it comes to ethylene and LNG, turbo-machinery; and in particular centrifugal compressors, are the core of such projects involving sophistication, cutting-edge technologies, and specialty know-how. Being custom-made to project specifications and operational requirements makes their successful realization a unique technical journey and a serious technological and managerial challenge.

In some cases centrifugal compressor shaft lines extend to 50 meters long with a rotating mass reaching hundreds of metric tons turning at a speed close to 3600 rpm, for compressing millions of kilograms per hour of process gas, all happening with vibrations levels barely felt by human sensation.

Such shaft lines are designed and engineered with latest simulation tools, verified with most advanced rotor-dynamic and aerodynamic models and software, manufactured to the most precise and accurate tolerances and rigorously inspected and tested for full trouble-free functionality.

The total cost of such compressor strings as part of a compression system in an LNG plant may reach over half a billion USD. The resources required involve hundreds of experts, specialists, engineers and technicians, and accordingly their realization is far from being a usual task.

This paper present the best practices and some of the know-how that have been progressively learnt, refined and implemented through the execution of several projects of this kind.
Asset Lifecycle Information Management as a Service
Authors: Koumpan E. , Noller D. , Kaijim W. , Webb G.
Published: November 2015

The Chemical and Petroleum (C&P) Industry is waking up to the power of data to create more value, reduce cost, and gain competitive advantage. When dealing with Major Capital Projects (MCP), we have seen an increasing transition from paper to digital, from stand alone to collaborative, from product to outcome, and from CAPEX (capital expenditure) / OPEX (operational expenditure) to TOPEX (total expenditure). This includes a shift from the traditional engineering, construction and handover to the owner/operator lifecycle and, ultimately, to the full asset lifecycle. The extended asset lifecycle and more, as well as new requirements to manage, have increased complexity. This is mainly do to more disciplines needing to work together in an integrated way using a shared asset information model

Data is the new natural resource. The amount of data the Engineering, Construction and Operation (EC&O) processes and activities produce, is authored in many different systems and consumed by many organizations and users in different formats. Not only is capturing their own data in their own systems of record (SOR) important to the C&P Industry, but so is external data, including unstructured data. The combination of SOR data with extended data can create additional value and provide new insights for better decision management.

Another complication is the fact that the EC&O processes of large scale Major Capital Projects have changed. Delivery today is typically divided across multiple organizations, and supported by multi-level supplier networks, in order to share the risk.
Optimizing Oil Development of a Super K Compartmentalized Reservoir with Large Gas Cap and Bottom Water Aquifer Case Study
Authors: El Gazar Ashraf , Bin Sumaidaa Saleh A. , Alklih Mohamad Yousef , Syofyan Syofvas , Al Shabibi Tariq Ali
Published: November 2015

This paper presents a case study of developing a significant volume of super K compartmentalized oil reservoir with a large gas cap and bottom water aquifer in Abu Dhabi-UAE. The reservoir is a low relief heterogeneous carbonate, located in a complex environment represented by natural and artificial islands in the surface, shallow and medium water marine areas with subsurface lateral, and vertical heterogeneities as well as variation in reservoir fluid properties.

The static and dynamic data were utilized to construct representative geological and dynamic models for the reservoir. The field development objective focused on maximizing the oil production and achieving 70% RF while minimizing the gas cusping, water conning and early breakthrough via super K interval.

Nine years production dynamic data were available from 6 oil producers in addition to well testing "14 wells", core "11 wells", MDT "17 wells" data during the appraisal phase. These data were used to quality control the initialization and history match phases. In preparation to the development options, the team included pressure support using water injection, lean gas injection, miscible gas injection, miscible WAG injection. The predicted reservoir performance of the super K oil reservoir indicated considerable gas production and high water production from the bottom water aquifer through super K interval in all the development options.

It was a big challenge to reduce the amount of gas production, water production, and early breakthrough for all development options. A new development option was introduced to perform peripheral miscible Hydrocarbon WAG injection accompanied with optimization of the wells and completion intervals locations for producers and injectors, as wells as WAG cycle to minimize the gas production from the gas cap, water production from the aquifer, and early breakthrough. This resulted in significant enhancement to plateau length, sweep efficiency, and recovery factor.

This paper provides the methodology followed to guide the development plan to fill in the uncertainty gap along with a detailed data acquisition and monitoring programs to better understand the reservoir behavior.
Successful Implementation of Sidewall Coring: 1st Trial in UAE
Authors: Mahmoud Gehad , Snaineh Bashar Abu , Steiner Stefan , Monson Eric , Shrivastava Chandramani
Published: November 2015

With the ongoing trend of E&P companies worldwide, there is currently an increasing pressure to tap the unconventional resources in the UAE as well as try to optimize well costs. Petrophysical evaluation of these reservoirs requires non-standard measurements. In this paper we will present how this approach was successful in utilizing the Side Wall Coring technology for the first time in ADCO fields.

This job required understanding what studies can be conducted on the acquired core plugs, as well as the operational planning and risk assessment to ensure a safe and successful operation. Two runs were planned on wireline due to maximum capacity of 50 core plugs per run.

A coring program was designed to investigate the potential of these source rocks formations.  And we managed to get 88 side wall cores (with a total length of 2 in by 0.92 inch diameters) with a recovery of 100% in two wireline runs. The coring operation was conducted in 12-1/4'' hole. The program was adjusted to record the log with less under balance, and before increasing the mud weight to avoid the risk of differential stuck by wire line while conducting the operations. Core analysis results are presented to show the importance of the acquired data.

This paper describes the first side wall coring job conducted in the UAE.  This includes planning, risk assessment, the core handling procedures, and lessons learned. A cost-benefit analysis is presented in which the applied coring technology has been compared to conventional coring
Beyond Compliance: Reduction of Emissions and Effluent Discharges
Authors: AlHanaee Shaikha , Ibrahim Muneef , ElHendawy Mohamed
Published: November 2015

Vertical well bores are drilled thousands of feet into the earth through sediment layers, the water table, and shale rock formations in order to reach the oil and gas. The drilling is then angled horizontally, where a cement casing is installed and will serve as a conduit for the massive volume of water, fracking fluid, chemicals and sand needed to fracture the rock and shale. In some cases, prior to the injection of fluids, small explosives are used to open up the bedrock. The fractures allow the gas and oil to be removed from the formerly impervious rock formations.

Pollution occurs from entry of foreign materials into air, water and/or ground. In marine environment many toxic chemicals convert to tiny particles which are then taken up by plankton and benthos animals. In this way, the toxins are concentrated upward within food chains. Many particles combine chemically in a manner highly depletive of oxygen, causing water to become anoxic.

In this context, for NDC, the adoption and implementation of a vigorous Environmental Management System (EMS) is paramount. The company is an ISO-14001 certified, therefore, it embraces an effectual process for evaluating the aspect related to its operations. This process is in accordance with ADNOC code of practices (ADNOC COPs), which are the general framework of all ADNOC groups of companies.
New Optimized Slot Recovery Method
Authors: Al Darkazly H. S. , Karrani S. , Al-Marzouqi A. , Khamis A. , Mukai N.
Published: November 2015

Slot recovery method has been applied in drilling industry. However, the current techniques have limitations in terms of cost efficiency, uncertainty of operation duration and limited to wells with integral conductor casing. The new slot recovery method can overcome all the above limitations with additional benefits to the new well. The new method is simple and environmentally friendly that can be applied under the HSE standards worldwide.

The method is to run hallow bit with diamond cutters. Clean the cement between the 30 inch conductor and the old 36 inch hole to 50 feet below old conductor shoe. Cuttings will be returned to sea bed, after cleaning cement, casing cutter will be run in to cut the 13.375 inch casing from inside to 50 feet below the conductor shoe. Afterwards, the casing spear will be run and latch internally in the 9.625 inch casing and then the casing is pulled out to rig floor. The casing is then secured and cut into intervals. As a result, after pulling the conductor pipe will have 37 inch empty hole. Cement string will be run to spot the cement plug inside the 37 inch Hole, and then dress the top of cement to the planned new 30 inch conductor shoe. Run new conductor and utilize the cement plug to kick off for the next drilling phase.

By using this method in slot recovery, the new well would have new conductor and no risk of old corroded conductor. The operation time guaranteed to match with planned days with estimated saving of 20 days compared to old methods. The cost saving is estimated USD 3 Million $ per well. Moreover, no more heavy milling that requires milling fluid and containers to collect the steel cuttings. By saving the time and cost, re-entry wells can be switched to slot recovery for achieving more sweet targets and insure long term well investment. The slot recovery wells can be drilled as dual string compared to single string in some cases of re-entry where casing size is a limit. The new method is simple to apply by rig crew, no need for service engineer and consumable mills. Utilizing this method to change wells from re-entry to slot recovery and hence enhancing oil recovery is a new approach of cost optimization.
Modelling for Safe Operations
Authors: Read Peter , Pushkarna Arun , Al Katheeri Z. A. , Al Rashedi H. , Ibrahim W. A.
Published: November 2015

Objectives/Scope

Problems in operations are not unusual to drilling. When a problem cropped up during drilling operations in the artificial islands and started manifesting itself in broken bolts, dropped objects, etc it posed a risk to the safety of personnel as well as integrity of operations frustrated staff from the OPCOs, Service Companies and Drilling Contractor examined their equipment while safety continued to be threatened with serious vibrations resulting in continued incidents of high potential dropped objects from heights.

Methods, Procedures, Process

The Drilling Contractor took the proactive step of resorting to modelling the rig and assemblies with the involvement of experts from a reputed University. The objective was to scientifically identify the reasons behind the undesired occurrences and seek solutions for safer operations. A continuum model was utilized and the drill string modelled to simulate the site conditions. The impact of the various positions oft he bottom hole assemblies was examined in the model and the results recorded to get a deeper understanding of the effect of these. Additionally the stiffness values were changed to simulate different Bottom Hole Assemblies.

Results, Observations, Conclusions

Surprisingly what was earlier thought of as a problem with the mast and the Topdive was eventually revealed as a problem with the type of bottomhole assembly which was giving rise to whirl and causing the mast and Topdrive to vibrate as a consequence. The modelling not only identified the root cause of the problems but even offered solutions to the problem. It gave an unexpected benefit by establishing a better, safer solution for performing drilling operations without risk of damaging vibrations.

Novel/Additive Information

The approach has opened up a completely new vista of operational safety and provided the tools for safe operations by allowing all involved parties to test any combination of downhole tools before deployment thus eliminating operational risks, improving process safety and operational efficiency.
Understanding Geomechanics in Clastic Sand Formations Proved Critical to the Success of the First Hydraulic Fracturing in the Offshore Clastic Sand Formations Abu Dhabi.
Authors: Aboujmeih H. F. , Al-Mansoori A. M. , Al-Mutwali O. , Al Ameri F. , Kaneko M. , Kuroda S. , Castro Ponce de Leon M. F. , Abbott J. , Akbari A.
Published: November 2015

Hydraulic fracturing is an important technique widely used for to improve well productivity in tight reservoirs and enable economic development. Geomechanical modeling is an important prerequisite required to ensure effective fracture construction and the required contact with the formation. In this paper, we show the first successful hydraulic fracturing in the Offshore Abu Dhabi clastic sand formations in which geomechanical modeling played an essential role in fracture design, completion design and successful execution.

The geomechanical properties and behavior of the clastic sand formations are still largely unknown in the Abu Dhabi region. In other parts of the Arabian Plate this formation is known to be a complex geological environment with high fracture gradients, poorly consolidated intervals, natural fractures and often rock that exhibits poroelastic behavior.

Due to the aforementioned complex geological environment resulting geomechanical attributes, the fracture design and key inputs including the calibrated Mechanical Earth Model (MEM) were essential to the successful design and execution of the first hydraulic fracturing in the Offshore Abu Dhabi clastic sand formations. The lessons learned during this successful design and application is critical for the design of future wells and the development of the UAE clastic sand formations.

The constructed MEM played a key role in successful hydraulic fracturing. Fracture height, length, width, direction, complexity and overall fracture performance are all largely controlled by the formation stresses, stress direction, rock properties and complexity of the rock fabric.

Geomechanical properties in the clastic sand formations in Abu Dhabi offshore were evaluated with less uncertainty by utilizing the advanced MEM. The calibrated MEM was integrated with an advanced fracture design simulator to optimize hydraulic fracture design. Results of the advanced MEM agreed well with fracture diagnostics and temperature surveys.

Work flow in this geomechanical analysis can be applied to hydraulic fracturing in other offshore tight reservoirs with a complex geological environment. Understanding the geomechanical properties of a formation allows engineers to optimize well placement, completion design, perforation placement, charge/gun selection and fracture design for improved well productivity.
Modelling Foam Displacement in Fractured Carbonate Reservoirs
Authors: AlMaqbali A. , Agada S. , Geiger S. , Haugen Å. , Fernø M. A.
Published: November 2015

Foam displacement has been employed in several field pilots which report improvement in mobility control, sweep efficiency, delayed gas breakthrough and EOR. However, foam behavior in highly heterogeneous porous media in general and fractured reservoir in particular is not well understood. Effective application of foam for enhanced oil recovery requires a good understanding of physical displacement processes (e.g. adsorption, foam generation, foam decay) at the laboratory and field scale. This is particularly important for the more complex fractured carbonate reservoirs which host over half of the world's remaining conventional oil reserves.

We investigate the effect of foam displacement in fractured carbonate reservoirs using numerical simulations tuned to experimental data to compare recovery for different injection strategies at different scales. In the experiments, high quality foam was generated by the injection of surfactant solution and N2 gas either in-situ or prior to injection. A mechanistic Lamella Density model was used to simulate core-scale laboratory experiments and history match the unknown foam parameters. We applied our understanding of foam displacement processes at the core scale to a reservoir model at the inter-well scale where additional heterogeneities were encountered. For this model we used a cross section of highly heterogeneous simulation model of a middle Jurassic carbonate ramp that is an analogue to the Arab D formation in Qatar. We used this model to test the effect of foam injection for different injection mechanisms, analyze the displacement processes, and compare the overall sweep and recovery.

Foam injection showed very promising results by diverting the flow from the high permeability fractures to the matrix, allowing for a better sweep efficiency that lead to a noticeable increase in differential pressure. Pre-formed foam yielded a higher recovery (around 78% of OOIP) compared to the in-situ generated foam in the core samples. This might be due to the smooth nature of the fractures leading to fewer snap off sites for foam generation. Varying the foam injection strategies (i.e. pre-formed foam, co-injection, and SAG) resulted in at least a 12% change in recovery compared to conventional water flooding and water-alternating gas injection. Foam quality, foam stability and injection mechanism were all factors that controlled sweep efficiency.

Our results illustrate how the laboratory-scale displacement mechanisms could operate on a larger (i.e. inter-well) scale where additional heterogeneities are encountered and the ratio of viscous to capillary and gravity forces changes. Our simulations also demonstrate that uncertainties in parameterizing foam models using experimental data from core floods translate into considerable uncertainties for predicting recovery at the field-scale. Still, foam can be an effective agent to increase oil recovery in fractured carbonate reservoirs by improving sweep efficiency and reducing gravity override.
A New Solution for the Characterization of Unconventional Shale Resources Based on Analysis of Drill Cuttings
Authors: de Block Merijn , Hofmann Andreas , Rigollet Christophe , Ravestein Johannes , Power Matthew , Haverkort Robert , Slot Bas Bruins , Bonijoly Didier
Published: November 2015

We introduce a new, cost-effective solution for the characterization of unconventional shale resources based on innovative analysis of drill cuttings. This solution was tested successfully on the Toarcian shales of the Couy-1 well, located in the southern Paris Basin, France. Ten samples of cuttings-sized rock fragments from different depths were subjected to several analytical methods to determine geochemical parameters (LECO and Rock Eval), the mineralogy and texture (QEMSCAN), and the mechanical properties (nanoindentation). Based on the results, the Toarcian shales were subdivided into two mineralogically distinct lithostratigraphic intervals. The Upper Toarcian shales consist of siltstone with a matrix of illitic clays, whereas the Lower Toarcian shales consist mainly of calcareous mudstone with a matrix of finely intermixed calcite and clays. The Young's modulus varies between 12.5 and 25.6 GPa and decreases with increasing TOC content. An interval with high TOC content (> 1.9%) is located between depths of 330 and 350 meter in the Lower Toarcian shales, with a maximum TOC content of 7.6%. A basic set of wireline logs was available and subjected to multi-mineral stochastic log interpretation. By calibrating the log interpretation with the results of the analytical methods, the main petrophysical parameters (TOC content, lithology, porosity, saturation) were successfully determined on log scale. This provides a method for upscaling core and drill cuttings measurements to reservoir scale. In addition, nanoindentation data were used to create a synthetic shear sonic log, allowing for calculation of elastic moduli and brittleness logs. The workflow introduced here provides a method for reliable and accurate characterization of unconventional shale resources based on existing data sets, i.e. drill cuttings and basic log sets. The results can be used for assessment of the hydrocarbon potential and identification of the most prospective zones within source-rock intervals.
Strategic Vocational Training for Nationalization
Authors: Jaber Nizam , Hashem Hekmat Bani
Published: November 2015

Objectives

the aim of this paper is to provide a practical model to qualify the National Workforce to meet the increasing demand for skilled workers especially in critical industries such as the oil & gas sector. It builds on the governmental nationalization initiatives and extends human resource development efforts beyond formal education and training to embrace workplace learning as the most effective and efficient approach for competence and capability building.

Method/procedure and process

based on ADNOC standards and guidelines, a model for workplace technical skills development was constructed. ADNOC Code of Practice is integrated with Scottish Vocational Qualifications Standards (SVQs) to ensure achievement of the desired outcomes. The main features of the proposed model include competence – based and structured on the job training (S-OJT). The model makes extensive use of the Scottish Workplace learning and development standards, in particular, facilitation of workplace learning through coaching, assessment of workplace competence and internal verification standard to ensure the quality and effectiveness of workplace learning interventions.

Results/Observations and conclusions

In line with ADNOC competency assurance policy, employees handling HSE critical roles have to know exactly how to do their job properly and be able to rely on the person next to them todo the same. SQA qualifications are designed to ensure that every employee is fully competent and can demonstrate their competence in their normal workplaces to the standard expectations. Integrating SVQs with ADNOCcompetence assurance policy and Code of Practice, will result in developed and well-preparedworkforce that will satisfy the requirements of the international standards as well as UAEPetroleum Industry Sector.

Novel/Additive Information

the unique structure of the presented model as a practical skill acquisition approach spans the trainee to expert knowledge and skills levels. It provides a systematic intervention for implementing vocational training based on experiential and adult learning principles to accelerate workplace learning. This adapted version of SVQs that are specifically tailored to meet ADNOC group demands of highly qualified and ready toparticipate National Workforce. While taking into account the current and future pressing needs for skilled national workforce in the petroleum sector, the model can be implemented in other sectors at the national scale as a supplement to NQA national skill development efforts.
Permeability Estimation from Production Logging for Horizontal Open Hole Drains in Carbonate Reservoir: Myth or Reality?
Authors: Espinoza Irina Baca , Maalouf Christophe Bassem , Al-Jaberi Salem , Ahmed Husnein Shershad , Amer Mohamed Mostafa
Published: November 2015

The estimation of permeability in openhole horizontal drains in carbonate reservoirs poses petrophysical and reservoir engineering challenges. The usual approach relies on the pressure transient analysis (PTA) from well testing data to estimate the average reservoir permeability. The attempt to estimate the permeability from production logging (PLT) usually fails due to many unknown parameters and to complex flow regimes. However, we believe that the average permeability estimated from PTA combined with PLT results can be used to evaluate the distributed permeability across the drain.

In this paper, several approaches for deriving permeability from PLT were evaluated. Considering that PLT is usually performed during early linear flow regime, the Babu and Odeh (1990) equation is used for average permeability estimation. The zonal permeability is calculated proportionally to productivity index (PI) per zone per foot.

In the proposed method, the distributed permeability calculation along the horizontal drain is closer to the average permeability estimated from PTA than other methods, such as core and nuclear magnetic resonance (NMR) permeability index log. Downhole rates and flowing bottom hole pressure are used as reference for history matching. The results from different methods were inconsistent in some zones. A wide range of permeability values were obtained in few zones and could be explained by the presence of fractures.

The paper demonstrates a novel approach of permeability calculation based on PLT data, and could be applicable for previous and upcoming well logging. The method clearly helps to reduce the uncertainties in permeability estimations. The conclusive findings from this study are considered to be a good integration practice that will help to improve reservoir flow characterization and eventually reservoir modeling.
The Interpretation of Permeability Changes During Acid Injection In Carbonates: A New Integrated Methodology
Authors: Qureshi Fahed , Gharbi Oussama , Julien Philippe
Published: November 2015

Monitoring and predicting the behavior induced by the injection of reactive fluids in carbonates is a common challenge for different applications. More particularly, acid is routinely injected in producers and injector wells within carbonate reservoirs to improve the permeability near the wellbore area. During a typical acid stimulation operation, two parameters are mainly monitored; these are the Bottom Hole Pressure (BHP) and the pumping rate. The objective of this paper is to highlight the importance of local changes on the overall pressure evolution and to provide a new methodology providing better interpretation of pressure-time evolution curves during acid stimulation operations.

First, a series of elevated temperature and pressure acid injection core flooding experiments were conducted. The overall pressure drop across the core samples was monitored classically using two pressure transducers at the inlet and outlet of the samples. In addition five pressure taps were recorded along the samples to be able to monitor the pressure evolution along the cores. Permeability time-evolution was then obtained for different flow rates, acid types and carbonate cores. The carbonate cores were characterized using high resolution pore-scale imaging, MICP and XRD measurements. Then, we complemented our core flooding measurements with values of permeability-changes induced by acid injection found in the literature. A database was formed and was subsequently analyzed.

We show that local changes in permeability can take place without impacting the overall pressure response. The measured permeability change depends on the scale of observation. We identified three main regimes of time-evolution permeability changes. We showed that the permeability is not directly proportional to the wormhole penetration. There is a certain time needed before starting to notice permeability increase. The wormhole breakthrough is characterized by a sharp increase in permeability. A new correlation factor that takes into account the pore size and the injection flow rate was obtained in order to correct for the time evolution permeability readings and take into account the impact of the scale of observations. This correlation was validated on the measurements from literature and from our laboratories. The next step will be to implement this correlation on a field case during acid stimulation operations.

Insights and results of this methodology can be applicable to better monitor other injections of reactive fluids in the areas of EOR and CCS.
Real Time Mitigation of Subsea Spool Instability Due to Uncertain Met-Ocean Data or Other Parameters
Authors: Sarkar Tarun Kumar
Published: November 2015

Instability of subsea riser spools or associated subsea pipeline facilities may arise during installation stage due to combined effect of changes in localized met-ocean data, free riser end not supported by the topside, free spanning seabed and absence of concrete coating in some parts of the riser spool. This paper deals with efficient mitigation of the problem on real-time basis by a new analytical approach. Instability of subsea riser spools or other section of a pipeline, observed during extreme weather condition, needs thorough observation and analysis. It may be difficult to quickly pinpoint the actual cause for the instability amongst a large number of variable parameters present. For example it is not possible to detect potential anomaly in theoretical met-ocean data in a short period as it requires at least six months to one year for validating theoretical met-ocean data by hind-casting with actual measured data. Though theoretical model of met-ocean data normally provides sufficiently accurate basis to proceed with FEED stage design, it may fail to accurately capture some unpredictable cases near islands. The new analytical approach determines additional submerged weight requirement indirectly from stable models observed under extreme weather conditions. Morison's hydrodynamic equations form a good basis to compare the observed response of the stable and unstable facilities. A unique stability response parameter of individual pipeline spools is then computed in a spreadsheet considering pipe OD, wall thickness, spool dimensions, applied concrete weight coating and calculated concrete weight. The result reveals that the response parameters of the stable spools are similar but distinctly different from that of the unstable ones. The additional weight requirements of the unstable facilities are then estimated such that their individual response parameters are aligned with that of the observed stable pipelines. Additional weight requirements are provided on the affected pipeline sections or spools by installing concrete mattresses. The proposed method provides a fast and effective mitigation option to deal with subsea instability issues on real time basis during advanced stage of installation. These safeguards against significant cost and schedule impact
Petrophysical Challenges in Unconventional and Tight Source Rocks, Onshore Abu Dhabi
Authors: Steiner S. , Raina I. , Dasgupta S. , Lewis R. , Monson E. R. , Abu-Snaineh B. A. , Alharthi A. , Lis G. P. , Chertova A.
Published: November 2015

ADCO started its unconventional exploration campaign in 2012 targeting the tight carbonate sequences known as Wasia Group, onshore Abu Dhabi. A front-end loaded data gathering strategy was employed to acquire extensive latest generation logging data tailored for unconventional reservoirs. In a number of wells the entire reservoir section was cored, often up to 800 ft per well, leading to more than 3000 ft of core retrieved to date. ADCO applied unconventional core analysis technologies, such as retort analysis, to generate the optimal core results. Key parameters such as effective porosity, pore size distribution, TOC, source rock maturity, mineral compositions and fluid saturations were determined from logs and core data (where available).

This paper will focus on the petrophysical challenges during the evaluation of the Wasia Group. We will demonstrate that conventional core analysis techniques have only limited applicability, whereas core analysis techniques designed specifically for unconventionals provide more relevant results. A log analysis methodology centered on the application and importance of NMR in unconventional liquid plays is presented. Porosity data measured through retort analysis provide an excellent fit to NMR log-based porosity measurements. Conventional core analysis results generated a poor fit to log porosity, and the resulting values exhibited scatter with a large standard deviation. T2 distribution from NMR log data suggests the presence of large pores with good fluid mobility, which requires confirmation through formation testing or production.

Log data-derived rock typing was performed. It is based on principal component analysis of the reservoir section. Rock classification may help in selecting suitable zones for hydraulic fracture initiation.

Lessons learned from the initial wells for core recovery and analysis techniques are summarized below and have been implemented in later wells: –Preserve part of the core for robust saturation measurements.–Stop acquisition of conventional poro-perm data–Focus on unconventional-specific retort-based techniques for core petrophysics–Focus on pulse decay permeabilities–Use scratch test to aid in core analysis sample selection process, especially for rock mechanics–Add core T1/T2 NMR and MICP to future core analysis programs

The complete integration of core and log data has allowed for a thorough assessment of the unconventional hydrocarbon potential within the ADCO concession.
Managing Sulphur Deposits in MP Sour Flare Headers
Authors: Whateley T. R. , Roquet D.
Published: November 2015

Significant sulphur and iron sulphide deposits were observed throughout the MP Sour flare header within the gas processing plant onshore facility. This deposit was generated through both a slow Claus reaction in the header when SO2 and H2S rich gasses combined and from sulfenic acid reaction with the pipe material. This solid material led to restrictions of up to 80% cross section for some flare sub headers and resulted in potential incapacitation of safety protection systems. Through gamma-scanning, the extent of build up was assessed and through hydro-jetting, several tons of the deposits were removed.

To mitigate future deposit formation, all SO2 rich sources to the MP Sour flare were positively isolated; bursting discs installed upstream of PSVs and spectacle blinds installed in closed position in maintenance vent lines to the MP Sour flare. In addition, purging of the relieving and venting lines with nitrogen following operation in SO2 rich service was mandated through revision of operating manuals. Potential sulfenic acid sources were identified and similarly isolated.
Integrated Formation MicroImager (FMI) and Spectral Noise Logging (SNL) for the Study of Fracturing in Carbonate Reservoirs
Authors: Aslanyan Arthur , Aslanyan Irina , Minakhmetova Roza , Maslennikova Yulia , Karantharath R. , Al Hadhrami Badar , Al Gafri Zaaima
Published: November 2015

Carbonate reservoirs are known to contain considerable hydrocarbon reserves. There are, however, several challenges that may complicate the process of development of this type of reservoirs, such as low porosity and high degree of fracturing and heterogeneity, which, cumulatively, could result in a low oil recovery factor (RF). Optimisation of development process in carbonate fields is impossible without preliminary reservoir studies focused on assessment of their production potential. Such studies include an analysis of complex pore space structure and local system of faults and fractures that may serve both as enhanced reservoir capacity and flow channels. Conventional logging techniques (for example, high-precision temperature logging and spinner surveys) solely used for estimation of reservoir productivity may have a limited scope of application. An integrated approach based on concurrent deployment of Formation MicroImager (FMI) and Spectral Noise Logging Tool (SNL) has considerably improved the interpretation of this scenario.

This paper gives some examples of carbonate reservoir surveys conducted in the wells located in one of the Middle Eastern fields. It has been shown that spectral noise logging data have a high degree of correlation with FMI data resulting from fracturing analysis. The active fracture flow zones have been distinctly outlined by Spectral Noise Logging data and further confirmed by High-Precision Temperature Logging data. The advantages offered by joint application of SNL and FMI techniques for studying carbonate reservoirs have therefore been clearly demonstrated. This approach can be successfully applied for the study of both natural and induced fractures.