bluuebunny/crossref_metadata_2025 huggingface dataset:
The Shale-Gas Permeability Measurement Considering the Rarefaction Effect on Transport Mechanism in the Nanopores
Authors: Gao Cheng , Xu Ruina , Jiang Peixue , Xue Huaqing
Published: March 2015

The pulse-decay technique is a well-established laboratory method for measuring the permeability of hydraulically tight rocks. Nitrogen or helium is routinely used in measurement of pulse-decay method, but the main components of natural gas reservoirs are hydrocarbons such as methane. In addition, nitrogen or helium has greater access to the fine pore structure of shale than larger molecules such as methane. Utilizing gas such as methane other than N2 or He to measure permeabilities requires corrections for gas rarefaction effect to be incorporated in the analyses.

Knudsen number (Kn), the ratio between the gas free molecule distance and the pore diameter, is one of the key parameters to evaluate the rarefaction effect on the transport mechanism in micro/nano channels or porous media structure. When 0.001<Kn<0.1, the velocity slip cannot be ignored in the channel and the permeability will decrease. Due to the Knudsen numbers which indicate the interaction between gas molecules and micro-pores for helium, nitrogen and methane in the same micro-structure of tight rock are significantly different; the permeability measurements are specific for individual working gases. However, our analysis shows that neither of these pulse-decay approaches takes into account the differences in transport mechanisms in shale due to different Kn numbers caused by different working gases.

In this paper, we conducted a series of experimental studies to investigate different pulse-decay permeabilities measured using helium, nitrogen and methane for the same specimen under the same reservoir conditions. Specifically, the importance of estimating accurate Kn numbers of different working gases in rock samples directly impact permeabilities of rock samples was demonstrated. In reviewing these approaches, we also would propose the need and possible direction of new models that will be required for making evaluations more accurate and accurate. The new theoretical model was indicated to illustrate the inherent relationship between the microscopic parameter Knudsen number and the macroscopic parameter permeability of a tight rock.

The results showed that Knudsen number would strongly affect the pulse-decay permeabilities measured under the same in situ confining-stress state reservoirs because of these existing pulse-decay models of gas flow in nanopores was inapplicable to measure permeabilities since the original assumption of no-slip boundary conditions in the Navier-Stokes equation was incorrect at nanoscale. It would be highly recommended using methane to measure permeability of micro-structure tight rocks (i.e. shale).
Environmental Liabilities in Oil and Gas Industry and Life-Cycle Management
Authors: Zhao Lian , Wells Joseph , Dong Benjing , Jin Qiuying , Tang Xu
Published: March 2015

This extended abstract provides an overview of the environmental liabilities of oil and gas assets, asset retirement obligations (AROs) and environmental reporting requirements under the regulatory regimes in Alberta, in Canada and International Financial Reporting Standards (IFRS). Lifecycle asset liability and environmental management processes are associated with abandonment, remediation and reclamation, decommissioning and closure. Alberta's production of conventional oil and gas and oil sands projects has resulted in increased concerns related to climate changes and environmental liabilities of oilfield assets. More stringent regulatory compliance and standards have been developed and are likely to continue. Operators are responsible for the costs to comply with environmental regulations and take sufficient social responsibilities. The industrial experience of discharging liabilities has indicated that planning at early stages of the operation and managing asset liability bring a reduced cost and risk. Full lifecycle cost-effective and efficient environmental management begins with planning and successful acquisition. The best estimate calculation can be based on internal or external costs, depending on which is most likely.
A Model for Wettability Alteration in Fractured Reservoirs
Authors: Andersen Pal Ostebo , Evje Steinar , Kleppe Hans , Skjaeveland Svein Magne
Published: March 2015

Many of the world's oil reservoirs are naturally fractured. Injected water will flow into this highly permeable network and not sweep the matrix containing most of the oil. Spontaneous imbibition can drive oil into the fractures by capillary forces. However the wettability of the reservoir is critical for the ultimate potential of oil recovery. Experimental results indicate that exposing chalk cores to seawater or similar brines may alter the wettability towards a more water-wet state. In a fractured reservoir this exposure will happen by molecular diffusion and by water imbibing into the matrix. The injected brine is not in chemical equilibrium with the in-situ rock, water and oil so that chemical reactions occur. Experiments have shown that for chalk rocks the relevant processes are adsorption/desorption of ions on the mineral surface, precipitation/dissolution of minerals or ion exchange. We have developed a model where a reservoir is defined by a fracture surrounded by matrix on both sides. The injected brine contains a component that can adsorb on the matrix surface. These changes of the mineral surface are assumed to alter the wettability towards a more water-wet state. The wettability alteration is described by shifting curves for relative permeability and capillary pressure from curves representing oil-wet conditions towards curves representing more water-wet conditions. The model can make predictions regarding the effect of matrix properties such as wettability and external parameters such as schedule of brine compositions and injection rate. The understanding of the coupling between wettability alteration controlled by water-rock chemistry and fracture-matrix flow is highly relevant for gaining more insight into the observed high recovery in the North Sea chalk field Ekofisk.
Unconventional Reservoir Fracture Evaluation Utilizing Deep Shear-Wave Imaging
Authors: Patterson Doug , Mekic Natasa , Bolshakov Alexei , Harrison Charles , Tang Xiaoming
Published: March 2015

Unconventional shale reservoir evaluation and development are extremely challenging. One of the most dominating aspects is permeability, which is measured in the nano-darcy range. Although these wells are stimulated to enhance production, the presence or absence of natural fractures can have a large impact on the production results. In addition, the fracture variation across a reservoir can be substantial, leading to large production variations, even in adjacent wells. Gaining insight about the natural fracture system, both intersecting and around the borehole, is crucial and can often help determine the economic success of a well and/or reservoir.

The standard means of fracture evaluation, such as borehole imaging, Stoneley permeability analysis, and azimuthal shear-wave anisotropy evaluation from cross-dipole, provide valuable information when evaluating fractures. These standard methods, however, can only investigate a limited area around the borehole—imaging looks at the borehole wall and the other borehole acoustic methods rely on refracted and guided modes that respond to an area as large as 2 to 4 ft out into the formation. The flexural wave from the dipole is one of the guided modes that generally reads the deepest and is used in the standard cross-dipole analysis. In addition to flexural mode, the dipole source creates shear body waves that radiate away from the borehole and into the formation. When these shear waves impinge on a fracture their energy reflects back to the borehole, enabling the facture to be imaged. The reflection strength is a function of the shear-wave polarization and the nature of the fracture, with the strongest response occurring from the shear waves intersecting a fluid/gas-filled fracture and polarizing in the fracture's strike direction.

Another important aspect is that these shear waves have azimuthal sensitivity, providing a means to determine the fracture direction. These features enable the evaluation of fractures over a much larger area around the well, often in excess of 60 ft from the borehole, and even detecting major fractures that do not intersect the well.

We will look at the application of this deep shear-wave imaging technology in several unconventional reservoirs across North America. Our review includes conventional methods and the deep shear-wave imaging analysis, showing its value in gaining important insight about the natural fracture system around the borehole, especially non-intersecting fractures. In addition, we will look at its application in mapping geologic structures in horizontal wells, demonstrating the ability to detect sub-seismic faults.
Modelling Sub-Seismic Reservoir Discontinuities: Integrating Production Data with Seismic Data and Geological Analogues
Authors: Barr D.C. , Kalu M.U. , Musa F. , Flynn M.J.
Published: March 2015

The "Z" Field, located in Block A-18 of the Northern Malay Basin, has been producing gas from complex, multiple-stacked sandstone reservoirs for approximately four years. Most reservoirs are located between around 3600 and 4300 ft TVDSS, and generally exhibit Class III AVO response, with better-quality zones exhibiting low acoustic impedance resulting in a high amplitude seismic expression. Consequently, the success rate for targeted production wells is high, with 100% of seismic anomalies drilled at these levels encountering commercial gas deposits.

Well "X" targeted one such amplitude anomaly and consistently produces gas at a rate of more than 20 MMscf/d. Two years later, another well, "Y", was drilled approximately 1 km away. Both wells lie within the same seismic anomaly, share similar electric log profiles and were originally thought to lie within the same sand body. However, reservoir pressure in well "Y" was found to be around 160 psi greater than in well "X", and CO2 concentrations were 7–8% higher, indicating the reservoir was compartmentalized.

Paleoenvironment is believed to be estuarine, with most sands interpreted as tidal bars. Analogue studies show that such deposits are frequently heterolithic, containing thin shale beds that can act as baffles or barriers. The zone of interest was subjected to a chemostratigraphic study, which revealed that the provenance of the sand differed between the two wells. This difference in provenance indicates that the reservoir is likely to be divided into at least two genetically distinct sand bodies.

After closer examination, several narrow zones of high acoustic impedance were identified in seismic attribute extractions. These zones were defined as permeability barriers in the static geomodel, which was subsequently used as the basis for the dynamic simulation model. The dynamic model was then history-matched to production data, and the position and extent of the modeled shale barriers were adjusted until an optimal history-match was achieved.

Complex, compartmentalized reservoirs are never easy to model. However, by incorporating multiple geological, geophysical and reservoir engineering data sets, geologically consistent models of static and dynamic reservoir behavior can be achieved.
Advanced Analytical Capabilities for Optimising Exploitation of Unconventional Resources
Authors: Hippler S.J. , Neal J.E. , Alramahi B. , Becker S. , Klimentidis R.E.
Published: March 2015

Unconventional resources (tight gas, shale gas, and tight liquids) have become a transformative energy source in North America largely through trial and error field experimentation. Low gas prices in North America and the expansion of unconventional developments internationally are driving a need for more rapid and lower cost assessments of potential. Operational efficiency will always be the critical success factor in unconventional resource development, but a holistic understanding of the system from plates to plays to pores can enhance that efficiency, achieved by integrating results from a variety of advanced laboratory analytical techniques with stratigraphic models that enable mapping of key play parameters.

Geochemical analysis of core and cuttings is used to determine organic matter type, richness, and thermal maturity, from which hydrocarbon yields and fluid properties can be predicted. With unconventional resources, the hydrocarbon source rock is often also the reservoir. To understand storage capacity, the new generation of scanning electron microscopes enables nanometer-scale imaging of pores in the mineral matrix and organic matter, and generation of three dimensional volumes of the pore network that provide insight into hydrocarbon habitat and shale permeability. Finally, geomechanical experiments are performed to measure compressive strength and elastic properties, which are used to calibrate log-scale measurements to understand the variation of these rock properties across a play. Proppant embedment tests are used to understand the mechanical interaction between rocks, proppants and stimulation fluids at simulated downhole pressure conditions.

Putting the results of these laboratory analyses and experiments into a play-scale stratigraphic framework provides an understanding of the geologic factors driving past successes and failures in a range of unconventional resource types. This has enabled assessment of basin potential in new plays before investment, and rapid evaluation of play-scale sweet spots.
HSE Management for China Offshore Drilling Project
Authors: Cheng Zhong , Cheng Kun , Yang Guang , Mou Xiaojun , Huang Xiaolong
Published: March 2015

According to the International Drilling HSE (Health, Safety, and Environment) management standards and advanced management experience as well as hazard management techniques, CNOOC (China National Offshore Oil Corporation) constantly improves HSE management objectives of offshore drilling platforms, HSE organizations and HSE operating specification in compliance with its particular drilling operation and development features, with the aim of in-place management and effective measures. During more than 30 years' drilling operations, CNOOC has already learned and summarized a set of drilling project HSE management systems, which have achieved good results. This article introduces the CNOOC Offshore Drilling HSE management organization and management system. Specifically, it presents the offshore drilling HSE guarantee measures from five aspects, which include field operation risk control, traffic safety, staff health, environmental protection, and emergency measures. Through the implementation of these management methods and measures, the CNOOC offshore drilling projects have gradually achieved the HSE management objectives: minor damage, low accident rate, and zero pollution.
The Utilisation of High-Definition Borehole Images to Determine Fracture Properties and Their Relative Age for Fractured Basement Reservoirs
Authors: Li Bingjian , Singam Thanapala , Kieu Pham Thi , Nam Thang Tran
Published: March 2015

Fracture data from borehole images has been a critical portion of well data for the fractured granite basement reservoir characterization for long in Vietnam. However, acquiring good quality electrical borehole images can be often challenging due to extremely high formation resistivity and also abnormal wide range of resistivity spectrum within the basement. A new imaging tool was introduced in the local basement wells recently to provide high-definition full-coverage electrical borehole images. The enhanced borehole images allowed better interpretation confidence and accuracy for fracture properties for the basement reservoirs.

There are a few case studies presented in this paper to illustrate some key improvements and applications of this new image data. First of all, the image quality enhancement from the high-definition tool is shown in comparison with conventional image data acquired from the same basement formation. Secondly, a case example is presented to show that accurate fracture properties derived from the high-definition images can help to better predict permeable zones with validation from dynamic data in the same well. Thirdly, examples on how to interpret relative fracture ages for the various sets of fractures developed in the basement using the new images are also discussed. Such fracture information potentially allows better understanding of the fracture/fault development as well as assisting geoscientists to build proper fracture models in the basement.

Introduction

The basement reservoirs in southern offshore Vietnam are naturally fractured with very tight matrix. Multiple fracture sets, developed under different deformation stages, provide permeability and part of storage capacity along with some other pore types like vuggy porosity associated with fractures or matrix-alike pore developed in the fault damaged zones. Such reservoirs are highly heterogeneous in terms of porosity distribution and permeability anisotropy.

Acquiring good quality microelectrical images in high-resistivity formations like granite basement can often be a challenge. Random noise sometimes obscured fine details or resulted in pixilated or "speckled" images in high-resistivity formations. An example of FMI* images from a basement is shown in Figure 1 to illustrate a few typical quality issues in the hard formations. First of all, the image can often have a "grainy" looking (or "speckled") background due to the tight matrix and very high formation resistivity, for instance in the low zone in Figure 1. Secondly, high level noise particularly in the zones with huge range of resistivity variation can result in geological features poorly defined. This can be also observed in the middle zone in Figure 1, where the vugs and fractures are not well defined due to high noise level (white spots) in the zone.
Drilling and Completion Technique Selection Methodolgy for Coalbed Methane Wells
Authors: Caballero J.
Published: March 2015

Geographically, coal-bed methane exploration or development has occurred on every continent with the exception of Antarctica. Worldwide, many different completion techniques have been utilized to develop coal-bed methane reservoirs. These techniques range from vertical well multi seam completions to multiple lateral wellbores drilled into a single coal seam. Stimulation techniques include open-hole under-ream, cavity creation, and hydraulic fracturing. A number of factors influence the selection of completion techniques including proximity to established oil and gas infrastructure, depth, number and thickness of coal seams, permeability, gas content, composition, and saturation, porosity, etc. The purpose of this paper is to survey the various techniques that have been utilized, to provide the rationale for utilization of each technique, to comment on the commercial success of the various techniques, and to propose a general selection criteria approach that may be useful in the selection of a drilling and completion technique.

Introduction

While CBM well drilling and completion permutations may be practically endless, the following summary descriptions will be covered in this paper: Vertical well, open-hole and under-ream completion, single seamVertical well, cased and open-hole, perforate and under-ream completion, multi-seamVertical well, open-hole cavity completion, single seamVertical well, cased perforated, hydraulic fracture completion, multi seam

Plug and Perforate Ball and Baffle Multiple Zone Stimulation Technology (MZST)Vertical well, open-hole under-ream with intercepting single or multiple surface to in-seam open-hole horizontal well(s), single seamVertical well, open-hole under-ream with intercepting a surface to in-seam open-hole multi-lateral horizontal well

Other techniques not listed here can generally be considered to be a variation or combination of one or more of these techniques. Many authors have proposed methods for determining the optimum drilling and completion method [1, 2, 3]. These methods have consisted of flow diagrams, empirical studies, and reliance on a few critical reservoir parameters and form the basis for conceptual understanding of the problem. This paper will present an overview of the various CBM drilling and completion techniques; reservoir parameters that need to be considered in the selection of drilling and completion techniques; and a proposed methodology for selecting optimum drilling and completion techniques will be proposed.
The Development of a Workflow to Improve Predictive Capability of Low Salinity Response
Authors: Suijkerbuijk B.M.J.M. , Kuipers H.P.C.E. , Van Kruijsdijk C.P.J.W. , Berg S. , van Winden J.F. , Ligthelm D.J. , Mahani H. , Pingo Almada M. , van den Pol E. , Joekar Niasar V. , Romanuka J. , Vermolen E.C.M. , Al-Qarshubi I.S.M.
Published: March 2015

Low Salinity Waterflooding (LSF) is an emerging improved oil recovery (IOR) technology that has been shown to work in a number of cases, while sometimes - unexpectedly - no incremental oil production is observed. Industry has not yet reached consensus on the mechanism behind LSF, which precludes effective screening and prioritization of LSF candidate fields.

In this paper a workflow is introduced that improves the way fields are screened for their LSF potential. It employs closely interlinked experiments and modeling work from the molecular scale to the macroscopic Darcy scale, thereby closing gaps that previously impeded the predictability of the low salinity effect. The new workflow is based on the notion that wettability is a surface phenomenon. Elucidation of the low salinity mechanism should thus not be based on bulk measurements, but rather on the characterization of surface compositions and forces.

The main insights that follow from this work are:Application of successful LSF leads to a wettability modification towards more water-wet, which is consistently observed at the atomic scale and at the core scale;The surface alterations that occur during LSF correlate with macroscopic observations such as oil recovery from core plugs;The time scales involved in wettability modification towards a more water-wet state can easily be long enough to lead to false negatives in common SCAL experiments;

It is demonstrated that double layer expansion (DLE) is likely behind the low salinity mechanism, as processes involving cation exchange are expected to only occur long after breakthrough of the low salinity bank.

Even though the workflow has been developed for LSF in sandstones, it is also being employed for LSF in carbonates. The fundamental insight that surface properties dominate the response does not only impact how LSF research and related SCAL experiments are being conducted, but impacts all other EOR processes relying on interfacial phenomena, as well as oil field science in general.
Novel Applications of Formation Testing to Optimise Field Redevelopment Program and Gas Injection EOR Project in Matured Fields
Authors: Guo Q. , Xiao C. , Zhao Y. , Chen J. , Xian C. , Zhuang X.
Published: March 2015

Formation testing has been utilized widely worldwide as well as in China for field exploration and appraisal, helping reservoir characterization and evaluating hydrocarbon reserve. However, using formation testing technology at development stage in order to improve the reservoir ultimate recovery is not mentioned much in published literatures. In this paper, two case studies were summarized on how formation testing was used at the secondary and tertiary stage of development field in west China including the first domestic gas injection monitoring application.

HD Field is one of the oilfields of PetroChina which contributes significant oil production in Tarim basin. With strong aquifer support, one challenge in the adjustment of oilfield development plan is to identify how a potential zone has been water flooded. This case study demonstrates how data acquired from the formation testing helps reservoir engineering study, revises the field development plan and eventually identify the new wells locations with encouraging production result.

The second case study demonstrates the first ever application in China of gas injection monitoring in field YH. This field is rich of gas condensate and utilizes gas injection as the main approach to drive the field production and to maintain the reservoir pressure. Because of commingle gas production from multiple zones; it is challenging to understand the sweeping efficiency of injected gas from different formation. With the help of real time downhole fluid composition measurement and innovative new designed probes, formation testing is able to pin point zones that have been swept by injected gas. So the gas injection strategy was adjusted accordingly to improve the overall field recovery.
Optimizing Operational Performance of Riser Systems Through Improved Understanding of Riser Thermal Behaviour
Authors: Sarkar Suranjan , Moeleker Piet , Kotikanyadanam Mohan , Chin Grace , Schwing Alex , Henkes Ruud , Zabaras George
Published: March 2015

One of Shell's deepwater projects has decided to use the cost-saving Single Casing Combo Top-Tension Riser with nitrogen insulation for the Tension Leg Platform (TLP) dry-tree wells to reduce the overall riser cost and TLP payload. However, the thermal performance of such a riser is poorly understood and an accurate prediction model was not available. A conservative thermal-hydraulic design approach would result in redundant requirements for the flow assurance chemicals and unnecessary challenges for the TLP operations. Numerical and experimental work was carried out to better understand and predict the riser thermal performance during startup, normal operation, and shut-in conditions. This paper described the numerical and experimental results. The overall heat transfer coefficients (U-values) from the detailed numerical simulations and experiments were used to derive the effective thermal conductivity (keff) of the nitrogen in the annulus, which includes the effect of all three modes of heat transfer (i.e. conduction, radiation and convention). This effective conductivity for the nitrogen gas was used in a one-dimensional model for the riser. The results of that model give the operator confidence in the system design and operability. The main benefit for the project is less chemical storage weight and space required on the TLP. The experimental and numerical model, with some modifications as required, can be used to optimize performance of riser systems in other projects as well.

Introduction

Single casing combo top-tensioned riser (SCC-TTR) for deepwater oil and gas developments

The development of deepwater oil and gas reserves constantly faces the challenge to reduce costs and complexity of the operations involved. This requirement increases the attraction of dry tree floating production facilities such as Spars and Tension Leg Platforms where direct accessibility of the wells below the production platform is possible. Dry tree units will continue to be the favored development approach for deepwater and ultra deep water developments [1]. Top-tensioned Risers (TTRs) have been in service on floating production facilities with either TLPs or Spars as the host vessel. A TTR primarily consists of a production tubing and casing(s) and it may be of the single casing or dual casing type. The single casing combo TTR (SCC-TTR) consists of a single casing and internal production tubing. This arrangement has the smallest diameter and offers the lightest solution with lowest capital cost.
The Damage Appraisal on Elemental Sulfur Deposition in High Sulfur Content Gas Reservoirs
Authors: Yang Xuefeng , Hu Yong , Zhong Bing , Yang Hongzhi , Wang Songxia
Published: March 2015

Research on the elemental sulfur deposition belongs to one of the most important tasks in the development of high sulfur content gas reservoirs. In order to evaluate the formation damage from elemental sulfur deposition in the developing process of the sour gas reservoir accurately, experimental procedures are devised to establish measurement method for determining elemental sulfur deposition by purchasing corresponding experimental accessories. The quantitative research on the elemental sulfur deposition is carried out for the first time at home and abroad. Natural carbonate cores and over-saturated natural sour gas are adopted to observe sulfur precipitation and plugging in the sulfur precipitation damage experiments, which is conducted under the condition of pressure and temperature close to actual reservoir as much as possible. Results illustrate that the sulfur deposition in core has little effect on the porosity with pressure decreased, but great impacts on the permeability. The damage factor of permeability increases with rising initial pressure, and temperature has rarely influence on the sulfur deposition with the same initial pressure. Furthermore, the declining permeability of core results in increasing the damage to the permeability, which means sulfur deposition will cause more harm in low permeability formation. Therefore, it is essential to lay full emphasis on the sulfur deposition during the development of sour gas reservoirs. The reasonable and efficient development strategy can be achieved by alleviating the elemental sulfur deposition as far as possible.

With the expanding energy contradiction between the supply and demand in the world, the development of high sulfur content gas reservoirs has caught more and more attention in public. However, the dissolution and deposition of elemental sulfur will take place during the developing process of sour gas reservoirs, compared with sweet gas reservoirs. The elemental sulfur solubility in sour gas decreases with the descent of formation pressure, the elemental sulfur will precipitate once the sulfur content exceeds its solubility. The precipitated sulfur will block the formation pore and reduce its permeability, which leads to lower the capacity of gas well seriously and even brings great detriment to the normal production and management of gas well. So far elemental sulfur deposition researches are mainly concentrated on oil reservoirs, papers about sulfur deposition experiment in sour gas reservoirs has not been published yet. Consequently, experimental procedures are devised to establish measurement method for determining elemental sulfur deposition by purchasing corresponding experimental accessories. Experiment of elemental sulfur precipitation in core is carried out for the first time at home and abroad, which lays the foundation for the further research on the safe and reasonable development of high sulfur content gas reservoir.
Formation Testing: New Methods for Rapid Mobility and Pore Pressure Prediction
Authors: Zhou Yanmin , Zhao Lixin , Feng Yongren , Yu Qiang , Chin Wilson
Published: March 2015

Fast and direct measurements for pore pressure and mobility are crucial to accurate formation evaluation, economic analysis and drilling safety. Real-time predictions can be obtained from formation tester pressure transient analysis. However, in tight sand and heavy oil environments, this is hampered by conventional approaches which require steady-state pressure responses that may require hours of wait time. These imply prohibitive offshore costs and increase the risks of stuck and lost tools; the methods derive from decades-old formulas intended for high-mobility formations which equilibrate rapidly. New math models are introduced that, now assuming high levels of pressure diffusion, require just seconds to yield acceptable pore pressures, and vertical and horizontal permeabilities. These augment traditional methods, providing suites of pressure evaluation tools covering all permeabilities; moreover, they do not require hardware changes to existing tools aside from downhole firmware modifications. For dual-probe tools, we develop analogies to resistivity logging: pump pistons are oscillated sinusoidally, and pressure phase and amplitude changes monitored at observation probes are interpreted using Darcy's law. Second, parallels to sonic logging are considered: pistons are allowed to impact formations suddenly, and signal arrival times measured at observation probes are converted to mobility. Third, for dual and single-probe systems, rapid "drawdown alone" and "drawdown-buildup" approaches that do not use exponential, transcendental or complicated error functions, but instead, efficient rational polynomial expansions, are described. Detailed examples and validations demonstrate the power and versatility behind the new methods for real-time and job planning applications. Fast calculations support increased downhole data usage, thus enhancing real-time capabilities; they free up resources needed to support other MWD/LWD functions. We also provide a photographic survey of newly developed wireline and "while drilling" formation testers that make use of the fast interpretation models and introduce the reader to new reservoir description capabilities.

Introduction

Formation testers, originally developed for fluid collection, are now widely accepted reservoir description instruments, providing detailed borehole information related to permeability, mobility, anisotropy and pore pressure. These objectives are met using pressure transient analysis models which interpret unsteady flowline changes with specially developed math models. Different designs are available from service companies. A cross-section of tools serving different logging applications developed by the present organization and its oil service subsidiary is shown in Figures 1a and 1b.
Field Trial Results of a Drilling Advisory System
Authors: Chang Dar-Lon , Payette Gregory S. , Pais Darren , Wang Lei , Bailey Jeffrey R. , Mitchell Nicholas D.
Published: March 2015

Field tests of a real-time Drilling Advisory System (DAS) have demonstrated value in several drill well surveillance applications. This system receives drilling data and transmits recommended operating parameters to the driller using existing rig systems and Wellsite Information Transfer Specification (WITS) data records. Using this industry standard, DAS can be deployed to any suitable data acquisition system on the diverse rig equipment available in the industry. The DAS computer may also be connected to a company network to enable desktop viewing of the drilling recommendations in the office.

The method embodied in the software comprises both a learning mode and an application mode. In learning mode, systematic changes in parameters are recommended to explore the operating space, and calculation of an objective function determines results. Complex decisions to change operating parameters such as weight on bit, rotary speed, and flow rate can also be made with the assistance of DAS via early detection of drilling dysfunctions which change with depth and formation.

The operator's ROP (Rate of Penetration) management process is focused on MSE (Mechanical Specific Energy) surveillance, and the DAS process extends this methodology to a real-time operating system. DAS is designed to assist the driller by capturing and organizing real-time data without imposing on their judgment and control. It is intended to be a digital helper that enhances the driller's ability to interpret current drilling conditions and make effective decisions.

Remote access capabilities and customized output to the driller's display were demonstrated in field trials, and key lessons from field trials have been implemented. The field trials included multiple hole sections in onshore and offshore wells across a wide variety of drilling conditions. In one example provided in this paper, the use of DAS provided 35% higher ROP when DAS was used to avoid drilling dysfunctions.

Introduction

In a recent paper by Dupriest and Koederitz from the 2005 SPE/IADC Drilling Conference ("Maximizing Drill Rates with Real-Time Surveillance of Mechanical Specific Energy": SPE 92194), Figure 1 was presented to illustrate the three basic regions on a drilling response curve. The chart shows that although operating above the founder point may provide slight increase in ROP, the system is operating in dysfunction and the WOB should be reduced to eliminate the dysfunction.
An Experimental Investigation on Archie Parameters at Ambient and Overburden Condition of Iranian Clean Carbonate Reservoir Rock and Developing a new Formation Resistivity Model for Limestone and Dolomite Samples
Authors: Eshraghi Ehsan , Moghadasi Jamshid
Published: March 2015

Electrical resistivity measurement is widely used to estimate porosity and water saturation. Archie equation is not easy to apply to carbonate rocks because formation parameters (a, m, n) are functions of changes in the pore geometry, clay content, tortuosity of the pores, as well as formation pressure. The Archie equation is also valid only when the rock is strongly water wet and clay free, which is not the case in carbonate rocks, therefore cannot be generalized over the entire carbonate reservoir, so the straightforward application of that in carbonate rocks has severe limitations.

In this paper, we discuss a new method using saturation analysis data to derive the correct form of the Archie equation that can be applied to carbonate rocks. Correlations among resistivity, and porosity derived from 108 actual core data of 18 core samples (10 dolomite and 8 limestone samples) in 6 different overburden pressures. The generalized equations can then be applied to any carbonate formation with varied geometry and clay content. The results of this comparison showed that the new developed model gave the best accuracy with average absolute errors of 20.4% and 10.9% for dolomite and limestone samples respectively, while the other common models are ranked, according to their accuracy in the following order to be Humble, Archie, and Shell, with average absolute errors of 26.0%, 26.7%, and 32.6% respectively for dolomites samples and in order to be Archie, Humble, and Shell with average absolute errors of 12.2%, 22.3%, and 26.2% respectively for limestone samples.

The advantages of this model is improving the accuracy of formation resistivity calculations by exerting the overburden pressure effect and specially usage of each formula for each mineral type.
Qatargas Greenhouse Gas Management Strategy
Authors: Al-Sulaiti Khalifa , Subedar Afzal Azizullah
Published: March 2015

Climate change presents a fundamental challenge to the way industries use energy and resources. Qatargas, the world's largest LNG producer is improving operational performance and energy efficiency to reduce Greenhouse Gas (GHG) emissions through an effective, well-structured and maturing GHG management strategy. This approach is aligned with the State of Qatar's position on climate change. Qatargas' strategy has three phases.

Phase 1 involved understanding the GHG issue, preparing an action plan, and focusing on internal capacity building through analysis of GHG policies, projects and markets. It also analyzed the potential impact of climate change on Qatargas' operations, and reviewed potential opportunities to reduce GHG emissions and participate in the global carbon market.

Phase 2 of the GHG strategy focuses on:Preparing a comprehensive GHG emissions inventory that includes emission sources from various business divisions, development of GHG management procedures and plans, and corporate GHG KPIs;Benchmarking GHG efficiency per tonne of LNG produced; andComparing company GHG performance relative to peer companies.

Qatargas' verified emissions inventory portfolio is providing data and trends, which is assisting in the understanding of key emission sources and provides a platform to progress Phase 3 of the GHG strategy.

Phase 3 focuses on carbon reduction opportunities and abatement techniques via sustainability assessments and engineering studies; and will also include a Life Cycle Assessment for GHG emissions from Qatargas' operations. These are in addition to the ongoing emissions reduction efforts such as the Flare Management Team initiative and the upcoming Jetty Boil-off Gas Recovery (JBOG) project.

Introduction

Anthropogenic related climate change effects are now generally accepted by the global scientific community, and although uncertainties persist, many governments and industry sectors around the world are implementing programs to address climate change issues. The Intergovernmental Panel on Climate Change (IPCC) 2007 report concluded that "warming of the climate system is unequivocal" and that it is "very likely that emissions from human activities have caused most of the observed increase in globally averaged temperatures since the mid-20th century." IPPC also identified many potentially devastating impacts resulting from climate change, including changes in Arctic temperatures and ice, ocean salinity, wind patterns, droughts, precipitation patterns, frequency of heat waves and intensity of tropical cyclones. These may not only have direct physical effects but create socio/economic-political instability and security issues for a wide range of directly and indirectly affected areas of the world.
The Controlled Freeze Zone Technology for the Commercialization of Sour Gas Resources
Authors: Valencia Jaime A. , Kelman Scott D. , Nagavarapu Ananda , Maher David W.
Published: March 2015

Controlled Freeze Zone™ is an efficient single-step cryogenic distillation process for the removal of carbon dioxide, hydrogen sulfide and other impurities from natural gas. Rather than avoiding the freezing of CO2 at cryogenic temperatures, the solidification is allowed to take place, albeit in a very controlled fashion. The technology has shown the potential to more efficiently and cost-effectively separate carbon dioxide and other impurities from natural gas, and to discharge these contaminants as a high-pressure liquid stream ready for underground injection, either for enhanced oil recovery applications or for acid gas injection disposal.

Introduction

Natural gas is the cleanest burning hydrocarbon fuel available and its growing demand is only projected to rise throughout this century. ExxonMobil anticipates total global energy demand to grow 35% by 2040 relative to 20101. Greater demand for electricity accounts for more than half of this increase. The clean burning characteristics of natural gas and its increasingly competitive economics for power generation are driving its expanded use in electrical power generation. Natural gas emits up to 60 percent less CO2 than coal when generating electricity, which becomes quite significant as costs arising from greenhouse gas policies mount. ExxonMobil forecasts natural gas to emerge as the leading source of electricity generation by 2040, and to become the second largest global fuel by 2040 behind oil, displacing coal from the second spot.

Meeting such a growth in demand will require a significant increase in gas production. New resources will be developed, many of them containing substantial amounts of CO2 and H2S that must be properly managed once brought up to the surface along with the produced hydrocarbons. Returning them to the sub-surface for geosequestration or using them in enhanced oil-recovery is emerging as a preferred option in their management and disposal. Commercial application of a technology like the ExxonMobil Controlled Freeze Zone (CFZ™) process can help meet that goal at a significantly lower cost than other competing technologies available today.

Acid Gas Injection

When acid gas injection is called for in the processing of sour gas resources, the relative advantages of the various types of treatment processes shifts towards options that release the acid gases, removed from the natural gas, at a relatively high pressure, and especially as a liquid. Natural gas fractionation can be designed to recover the acid gases at high pressure and at least partially in some cases as a liquid. This minimizes the power required for compression or pumping for reinjection of the waste acid gases.
The Hydrocarbon Pipeline Network and Development in Qatar
Authors: Al-Rasheed Abdulla Ezzat
Published: March 2015

The Transmission and Distribution Network comprises of interconnected gas and oil pipelines network of approximately 3000 km length, associated manifolds and more than 70 distribution stations located through Qatar. The hydrocarbons transported in this network such as sweet Methane gas, Ethane network, stripped associated gases, and tail gas, etc… are all utilized as fuel and feedstock gases to supply the various power plants and industries located in the State of Qatar. In addition, Transmission and distribution network is also responsible to monitor and maintain all QP and third party Companies' pipelines such as row gas, condensate and LPG pipelines, Ethylene pipeline and crude oil pipelines.

As the State of Qatar is booming with tremendous expansion and development to the infrastructure for hosting the FIFA World cup 2022 and to meet its 2030 National Vision, the Gas pipeline network is also being expanded to meet Year 2030 supply and demand forecast, future industries and Urban and infrastructure development.

The aim of this paper is to illustrate the development/expansion of QP pipelines network to cover the future national gas supply and demand forecast up to 2030. This will cover the expansion of power generation due to the increase in future national energy demand and the expansion and requirement for the new industries. In addition, the paper will highlight the urban development requirement such as domestic gas supply to houses and using Compressed Natural Gas CNG for local transportation. Moreover, the paper will discuss the infrastructure developments such as the new pipeline corridor tidiness and rationalization, new rail way interfaces with the existing pipeline network, and new Jet fuel requirement to the new Doha International Airport. All the significant challenges and lessons learnt for the network's planning, interfaces, construction, re-routing and operational challenges will be also addressed in this paper.

Overview of the Gas Distribution System (GDS) Suppliers and Consumers

This network is responsible to supply continuous and uninterrupted fuel gas needs of the State power plants for power generation and desalination within the State of Qatar. In addition, it is responsible to supply fuel and feedstock gases to the various industrial plants located in Mesaieed, Ras Laffan and Doha. The various types of consumers from power plants to industrial consumers require different types of gases as a fuel or feedstock to their plants. The various gases are provided by the Gas distribution system (GDS) which consists of sweet gas network, Ethane network, stripped associated gases from onshore ONSAG and offshore fields OFSAG, and Tail gas.