bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracturing Mechanism and Fracture Systems Analysis of Fractured Carbonate Reservoir from Abu Dhabi, UAE
Authors: Sirat M. , Salman S. M. , Bellah S. 
Published: December 2007

Abstract
Many fractured carbonate reservoirs of Abu Dhabi have different structural styles and exhibit unpredicted behavior for development-production realizations. We have studied one of these reservoirs that comprise a domal structure with very gentle dipping flanks, and high fractures density. These fractures play an important role in controlling fluid flow and recovery.
In this study, we present a conceptual model that explains the fracturing mechanism; formation, development and reactivations of these fractures. It also provides answers to questions about the main factors that control fracture geometries and densities with respect to reservoir structure and rock typing. Based on the available data from 2D seismics and cores examination, fracture systems identification and classification were carried out. We have also discussed the relationships between these fracture systems with curvature, faults and shear zones.
We believe that fracturing mechanism is mainly controlled by reactivations of the pre-existing basement faults (structural grain), which have been reflected throughout the sedimentary cover as two main fractures systems each of which comprises three fracture sets: one extensional and two conjugate shear ones. It is evident that curvature of doming whether on the crest (convexity) or on the flanks (concavity) have no major effect on fracture densities. Instead, fracture densities increase in the vicinity of faults or shear zones. Fracture densities also increase in dolomitic layers compared to limestones and anhydrates.
This new fracturing concept has a significant impact on production and recovery, where different scenarios for fractures opening/reactivations due to the present state of stresses are presented.
High Resolution CT and Pore-Network Models to Assess Petrophysical Properties of Homogeneous and Heterogeneous Carbonates
Authors: Youssef S. , Rosenberg E. , Gland N. , Kenter J. A. M. , Skalinski M. , Vizika O. 
Published: December 2007

Abstract
Carbonate rocks often present complex pore-structures involving multiple porosity systems with various interconnectivity degrees. These pore-systems, from microporosity to vugs/fissures, drastically affect petrophysical properties. Pore network models are well suited to calculate petrophysical properties of rocks from pore space structure information. The predictability of such models depends on the accuracy with which the complex geometry and topology of the pore network are captured. Computed MicroTomography (μCT) produces 3D images of the porous medium at the micron scale thus giving the opportunity to describe quantitatively and with a high precision the geometrical and topological characteristics of the 3D pore space. By providing a full description of pore space connectivity and geometry, such studies promise to improve both the understanding of diagenetic overprint and predictability of pore network models used to calculate petrophysical properties of these porous media.
This methodology is applied to a set of rocks with various heterogeneity degrees from the Tengiz buildup (Precaspian Basin). The Tengiz central platform contains a succession of cyclic shallow water deposits ranging from Famennian to Bashkirian in age. The distribution of reservoir rock-types in this depositional zone is determined by a combination of primary deposition and burial diagenetic modification and includes spatial variations of both porosity enhancing as well as porosity filling effects. A pilot study using pore-network modeling from μ-CT imagery of several selected samples resulted in spatial pore and pore-throat size distributions, level and type of pore interconnectivity. Porosity, permeability and capillary pressure were calculated from μ-CT analyses and show a close match with those derived from measurements. Most strikingly, μ-CT allowed the extraction of 3Ddistribution of pore type and connectivity as well as cement types, information essential to reservoir quality assessment but very difficult to reconstruct using the classic petrographic approach. These models can be used for rock-typing, up scaling, to extrapolate petrophysical properties to uncored wells and to investigate new phenomena like evolution of properties due to dissolution/precipitation inherent in CO2 injection.
Progress in Immiscible WAG Modelling
Authors: Skauge A. , Dale E. I. 
Published: December 2007

Abstract
The paper reviews recent development in modelling of immiscible WAG processes (IWAG). Several different approaches have been made to model three-phase relative permeability in particular. In most cases capillary pressure has been neglected in application of these models in numerical simulations of IWAG. The argument behind eliminating capillary pressure is to simplify the model, and the assumption that capillary pressure is of less importance for the problem analysed or because there are no experimental data available. This study also shows the consequence of neglecting capillary pressure.
A novel approach to include three-phase capillary pressure is discussed, and also a procedure for estimation of three-phase capillary pressure from more available two-phase capillary pressure data. A practical case study of history matching IWAG core floods is also presented.
Evaluating the Efficiency of Near Neutral Pickling Fluids
Authors: Mofunlewi Samuel S. , Uchendu Ugochukwu 
Published: December 2007

Abstract
With continuous efforts to introduce new technologies for wellbore cleaning, a near neutral pH pickling fluid has been evaluated for use as a pickling fluid. Pickle treatments are done to improve well productivity by removing various contaminants from well tubulars in an efficient and cost effective way.
Traditionally, iron oxides and hydroxides scales in tubular are removed with weak HCl (typically 5–15%). However, the use of acid as a pickling fluid has become a deterant to operators since they pose safety and environmental handling risks. The disposal of the spent acid is also very costly due to its corrosive nature (pH&lt;0).
Laboratory evaluation has shown that, near neutral pickling fluid has a better derusting effect than HCl. It gives a phosphate coating at the metal surface delaying it from further reoxidation. The pH of the fluid before and after treatment was found to be 5.90 and 6.20 respectively making it more safety and environmentally friendly than the traditional HCl. Field application of the fluid has shown it to be 8% more economical than HCl.
This paper will discuss details of our laboratory analysis and findings. Case histories of this fluid shall also be discussed.
Technology Based Formation Damage Control & Mitigation Measures in the SINCOR Zuata Field, Venezuela
Authors: Nnabuihe Larry , Couzigou Erwan , Chan Albert , Solana Alberto 
Published: December 2007

Abstract
The poor productivity and abnormal productivity decline in some SINCOR horizontal wells in the Faja field could be traced back to drilling and well completion practices. The wells were drilled with solid-free XCD mud and completed with slotted liners. Drilling operation is characterized by severe mud losses. The wells were brought into production without wellbore cleanout to remove the drilling mud induced damage. The wells produce Extra Heavy Oil (EHO). The observed trends since the start-up of production was indicative of the skin damage magnitude.
An in-house review in 2005 adopted an approach that included acquiring and extending information derived from cores and reservoir fluids, laboratory analysis data, drilling, well completion/well test results, and production data. X-ray diffraction studies show that the formation contains about 8% of clay minerals which comprise mostly kaolinite (~85%) with traces of illite and smectite. The damage mechanisms identified included fines migration, the swelling of reactive clay minerals, physical blockage by unremoved filter-cake masses, water-block resulting from massive leakoff of aqueous mud filtrate, the wax crystallization and asphaltene precipitation blockage.
Engineering work and technology-based solution which encompass diagnosis of damage mechanism, laboratory testing, formulation and optimization of treatment fluids, job design and field execution procedure were carried out to mitigate the formation damage. The surfactant-diesel based (SDB) treatment design and application has yielded great successes in removal of formation damage, resulting in a high incremental oil production with job payback time of 3 – 24 days. Evaluation of the two SDB treatment campaigns conducted in 2005/2006 revealed that water-block with its associated high Interfacial Tension against the EHO constitutes a serious impediment to oil productivity.
Achieving Nigeria's Gas Flares-Out Target: Challenges and Implications for Environmental Sustainability and Global Climate Change
Authors: Igbatayo Samuel A. 
Published: December 2007

Abstract
Following Nigeria's global acclaim as a dominant crude oil producer and exporter, the nation's natural gas industry has demonstrated a huge potential as a strong player in the emergent global natural gas market. Although Nigeria is yet to explore directly for gas, as most of its gas discoveries are incidental to production of crude oil; the nation has one of the largest natural gas reserves in the world. Currently estimated at about 187 trillion standard cubic feet, Nigeria's natural gas reserves are rated amongst the top ten largest in the world. Distributed evenly between associated and nonassociated gas, most of the nation's natural gas production has been flared or re-injected to enhance greater crude oil recovery. However, gas flaring is accompanied by considerable environmental degradation, particularly in the Niger Delta, where the bulk of the nation's oil and gas resources are found. Also, Nigeria has been blamed for the emergent global climate change through its green house gas emissions. This has serious consequences for both regional and global environmental sustainability. Consequently, the nation's policy makers decided to capture the economic benefits associated with Nigeria's huge stock of natural gas and stem the damaging tide of environmental degradation. This development has informed the nation's gas flare-out target set for 2008, and imposed on the nation's oil and gas industry. Therefore, this paper provides a holistic framework for attaining the nation's flare-out target and ensuring compliance with elimination of global greenhouse gas emissions.
Managing Pipelines Risk in Nigeria
Authors: Awonusi Samuel 
Published: December 2007

Abstract
In Nigeria today, there are networks of pipelines cris-crossing the entire nation. These lines are used to transport hydrocarbon from the oilfields to the terminals and LNG plants. They are also used to move products from petroleum refineries or petroleum receiving jetties to product depots in the downstream sector.
Pipelines risks are negative and undesirable factors that could erode the benefits of safe movement of hydrocarbon products cheaply and efficiently through these pipe networks. These risk factors are increasing by the day with the changing complexities of the Nigerian society.
There are three keys drivers that drive the management of risks associated with pipeline transportation. These are economic benefits to users of pipelines, corporate social responsibility on the part of companies (multinationals) to their employees and third parties; and government regulations.
The consequences of the attendant poor management have been loss of thousands of lives to fire outbreak on exposed pipelines, pollution of the environment, loss of earning power and scarcity of refined petroleum products in the country.
Applying the HEMP process, it is the intention of this paper to take a critical look at pipelines associated risks, assessment of the risks taking into consideration current realities in the country and what controls are required to safeguard the pipelines, people and the environment in Nigeria.
Impact of Structural and Stratigraphic Heterogeneities in Deep Water Development
Authors: Onyeagoro Kachi , Naruk Steve , Van der Vlugt Frans , Barton Mark , Pirmez Carlos , O’Byrne Ciaran 
Published: December 2007

Abstract
Recent successful exploration and production programs in deepwater settings worldwide have increased the need to better understand the range of structural and stratigraphic depositional complexities and their impacts on performance and sweep efficiency. As oil and gas companies explore and produce hydrocarbons in deeper water settings, and in their quest to produce hydrocarbons from difficult or unconventional reservoirs, there is a need to develop innovative ways of achieving success and reducing the overall cost – an enabler to remaining competitive and profitable.
First generation deep-water production in the Gulf of Mexico was from well imaged, structurally and stratigraphically simple fields, penetrated by multiple wells and producing at high ultimate - high recovery rates with gradual pressure declines. A second-tier of deep-water fields in the Gulf of Mexico, Deep-water Nigeria and Brazil are structurally and stratigraphically complex and are posing more challenges to cost efficient development. A poor initial understanding of the distribution and impact of these heterogeneities has led to unforeseen compartmentalization issues within these second-generation deep-water reservoirs.
One of the key challenges in the development of structurally and stratigraphically complex fields is to realistically translate geological and reservoir engineering data into parameters that can be used to assess and mitigate compartmentalization. Many structural and stratigraphic features that do not define pressure compartments prior to production become significant barriers to flow during production, necessitating the drilling of more wells to increase recovery from the field. Clearly the ability to make early predictions on when and where such barriers occur and their effectiveness during a production lifecycle can be key to successfully developing second generation fields in deepwater settings.
The importance of answering these questions and realistically characterizing and quantifying structural and stratigraphic heterogeneities has been demonstrated in many deepwater fields. These characterizations have yielded more accurate and better-defined well paths of highly deviated and horizontal wells across faults and different stratigraphies, robust field development plans with clear economic advantages, and successful history matches.
Tuning the Analytical Model for Better Prediction of Recovery Factor
Authors: Akpara Kingsley 
Published: December 2007

ABSTRACT
Recovery factor is one of the key determinant variables for establishing reservoir description in reservoir modeling. Existing analytical solutions postulate the use of average reservoir and pressure dependent parameters to estimate static recovery. At start of field development, prediction of recovery factor could sometimes be misleading because insufficient data is used to tag the economic value of the field. Though this practice is necessary to quantify the profitability of the venture, it is advisable to apply reservoir simulation for detailed description of the reservoir hence better dynamic prediction of recovery.
This paper therefore, investigates an excellent idea that improves estimation of recovery by using dynamic parameters; dynamic in the sense that better understanding of the reservoir character changes the initial perception of its properties. This idea recognized the mathematical model by Arps et al, but the modification here is that post history matched reservoir initial properties are inputs in the correlation, resulting to changes in the multiplicative and exponential constant. With this, one could investigate segment, zones and cell contribution to recovery.
A Didactic Analysis of Water Cut Trend During Exponential Oil-Decline
Authors: Lawal Kazeem A. , Utin Emmanuel , Langaas Kåre 
Published: December 2007

Abstract
While a number of methods, including semi-log/linear plot of water cut versus cumulative oil and water-oil ratio versus cumulative oil, have been published for extrapolating water cut during oil decline, the challenges of internal consistency, accuracy and limited areas of application have remained unresolved. These make the application of the methods threatening to the associated estimates of oil reserves and investments on water-handling facilities.
In this paper, based on an investigation of internal/practical consistency and the physics of fluid flow, a didactic analysis of water cut models derivable from popular oil rate models of Arps, Li and Horne, as well as the Flowing Material Balance is carried out. This culminated in the development of an internally consistent water cut model, applicable during exponential decline of oil production. The development supports an exponential function of oil-cut vs production time.
Using both hypothetic and field examples, applicability and performance of the derived model are demonstrated, and compared with six of the popular water cut models, including those of Ershagi and Omoregie, Liu, Warren and Purvis. Besides its simplicity, the proposed model consistently performs better and shows robustness.
Although the form of the proposed model is here limited to exponential oil rate decline, the principles can easily be extended to other oil production decline trends.
An Experimental Investigation of In-situ Combustion in Heterogeneous Media
Authors: Awoleke Olurotimi G. 
Published: December 2007

Abstract
An extensive literature exists on the nature of the reactions that occur when air comes in contact with crude oil during in-situ combustion (ISC); however the effect of reservoir heterogeneity on the ISC process has not been experimentally addressed in prior studies. This paper presents the results of recent experimental efforts to shed more light on ISC. We probe the effect of pressure, temperature, injection flow-rate, and matrix properties on the combustion of a Middle-Eastern 19.7° API oil in a tight-formation sand. The experimental perspective includes both oil oxidation kinetics and combustion-front dynamics in a 1-m long combustion tube. Most importantly, geological effects on the ISC process are investigated by incorporating various degrees of porous medium heterogeneity in the combustion tube runs. From the experimental data, pre and post burn CT scans of the combustion tube, and postmortem analyses, we deduce the effect of both small and large-scale heterogeneities on the spatial and temporal propagation of the combustion front.
Specifically, kinetic runs show typical ISC behavior consistent with oxidation and good reactivity of the oil-rock system. It was observed that the supply pressure, injection flow-rate, the reservoir matrix and a metallic additive significantly affected the performance of this particular system. Better combustion resulted from greater oxygen partial pressures and by using the reservoir rock as compared to an artificial sand-clay mix. The combustion tube runs indicate that the process of in-situ combustion can be successfully implemented in a reservoir with small-scale heterogeneities (a few inches) and may be challenged by much larger scales (feet).
Effect of Sugar on the Thickening Time of Cement Slurries
Authors: Bermudez Marta 
Published: December 2007

Abstract
Sugar is widely recognized as a cement retarder by the drilling industry and has been used in cementing operations where cement returns are expected on surface.
Experts disagree about the effect that sugar has on cement slurries, a few believe that it acts as both an accelerator and a retarder depending on the concentration, but the majority believe that the sugar acts as a retarder only.
Lab tests of thickening time and compressive strength were conducted using different concentrations of sugar. The results indicated that the sugar acts as a retarder of cement slurries when added in small concentrations and as an accelerator when added in high concentration.
The compressive strength tests showed that the accelerated slurries developed very little or no compressive strength, indicating that no hydration of the cement grains occurred. The retarding mechanism of the sugar is well documented, but the acceleration effect is not widely known. An attempt was made to explain the mechanisms involved in the shorter thickening time and lack of compressive strength observed at high sugar concentrations.
These project findings are of great practical importance to the drilling industry. Sugar is currently used in the field with the idea that it will always retard the slurry.
Enhanced Coal Bed Methane Recovery Using Nitrogenase Enzyme
Authors: Vishnukumar Joshi Neeti 
Published: December 2007

Abstract
As per the present-day scenario, energy consumption is increasing by 5.6% per annum, so it is today's requirement to extract more efficiently from currently available reservoirs and to find novel energy resources. Coal Bed Methane (CBM) is one such non-conventional hydrocarbon resource, which is easily extractable. This paper focuses on Enhanced Coal bed Methane Recovery using biogenic enzymes for increasing secondary recovery. The primary recovery of CBM is nearly 50 % (Jichun Zue et al, 2003) and the conventional secondary recovery using gas injection technique is around additional 6-8%. This paper introduces the concept of Enhanced Coal bed Methane Recovery using biogenic enzymes for increasing secondary recovery. Here, use of thermostable Nitrogenase enzyme is suggested to fix the injected nitrogen as a compound for enhancement in secondary recovery of the Methane. The enzyme can be generated in biochemical plants using ‘Nif’ gene as a microbiological tool. The Nitrogenase Enzyme is immobilized for longer activity. The immobilized enzyme, which is then injected into the well bore suspended in the proper medium. This paper provides systematic approach and relevant theoretical explanation for the proposed technique, which is suggested for the first time.
Technical-Economic Modeling of CO2 Sequestration Considering Injection in Mature Oil Fields
Authors: Ravagnani A. T. F. S. Gaspar 
Published: December 2007

Abstract
The oil industry with its technological developments and tools may help to alleviate the greenhouse gases emissions into the atmosphere. The CO2 injection in oil reservoir as an agent for EOR (Enhanced Oil Recovery) has a dual benefit. This technology can improve to recover oil that is not produced through natural methods anymore, besides to store CO2 in the reservoir for thousands of years avoiding it reach the atmosphere, through the technology known as CO2 sequestration. It consists on the capture of the gas from an anthropogenic source, its compression and transportation to the oilfield. This work presents a technical-economic methodology to evaluate the feasibility of the process in a hypothetical mature oilfield. It considers a cash-flow model besides a sensitivity analysis considering the main components such as revenues, investments, operating costs, taxes according Brazilian fiscal regime and the carbon credits to be earned due to the project. The methodology takes into account the quantification of emissions and energy used in the process, emphasizing the technology contribution to the environment.