bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Key Cement Additives on the Mechanical Properties of Normal Density Oil and Gas Well Cement Systems
Authors: Heinold Thomas , Dillenbeck Robert L. , Rogers Murray J.
Published: December 2007

Recent advances in oil and gas cementing technology allow for the modeling and prediction of both compressive and tensile stresses upon an annular cement sheath, throughout the life of a well. Given the knowledge of the type and magnitude of stresses likely to be encountered in a specific location in a wells annulus gives designers target parameters for designing the mechanical properties necessary in the set cement to be able to sustain those stresses without failing. Such a mechanical failure in a cement sheath can cause a loss of annular isolation. However, the authors feel the ability to model these stresses is only one-half of the information necessary to design cement systems for long-term zonal isolation. While some good work has been done on certain lower density cement systems in an attempt to develop fit-for-purpose designs with improved tensile and flexural strengths, the authors have found that some wells requiring higher density cement systems, also need cements with "enhanced" mechanical properties. Towards this end, the authors have conducted mechanical properties research of several relatively common cement additives. These included organic materials as well as non-organic materials. For this study, these materials were added to oilfield cements with water contents averaging from 50 to 66 % by weight of cement (bwoc). Besides the more common unconfined compressive strength tests, the samples are also subjected to tensile and/or flexural strength testing. While the API has long ago established procedures for running unconfined compressive strength tests, there are currently no API standards in place covering the testing methodology for tensile and/or flexural strengths of oilfield cements. Accordingly, the authors present not only the mechanical properties achieved with the use of the various materials tested, but also the methodology used to achieve their data. In an effort to more closely scrutinize the effect each individual material has on the mechanical properties of the set cement, each additive is examined independently. Armed with this information, design engineers should be equipped to propose cement systems that produce effective long-term zonal isolation at the induced annular stresses of their own wells.
The Influence of Multi-Pore Volume Water Flooding on Pore Structure and Recovery of Lacustrine Deposit Mixed Wettability Cores
Authors: Wang Demin , Guo Muchang , Wang Gang
Published: December 2007

Daqing Oil Field is a reservoir with lacustrine deposit pay zones of mixed wettability (slightly more oil wet). On the average, after flooding cores with 2 ~ 2.5 PV (pore volumes) of water, the water cut practically reaches 100% and the average recovery is about 40% OOIP (original oil in place). However, results from pressure coring in the field show that sometimes the recovery of high permeability streaks of the pay zone can reach 80% ~ 90% OOIP, much higher than that obtained in the lab.

Since Daqing is a very heterogeneous reservoir, the pore volumes of water that pass through high permeability streaks of the formation is much higher than the average. In order to see the increase in recovery and decrease in residual oil saturation of cores after water flooding by multi-pore volumes to check if the end point of the relative permeability curves that are drawn is the real residual oil saturation, multi pore volumes (some more than 30 thousand PV) water flooding on natural cores was performed in the lab. The results show that for mixed wettability (slightly more oil wet) cores of Daqing Oil Field's pay zones, when using multi PV of water to flood the cores, and when the effluent water cut is very high (practically 100%), oil can still slowly flow in the oil film on the pore rock surface and accumulate to form mobile oil (many cores can obtain a final recovery of more than 90% OOIP, some as high as 99%), which means that the oil has not reached "real residual oil" saturation, it is only because the oil cut of the effluent fluid of the core is extremely low, therefore it is difficult to observe the oil in the produced fluid. This paper shows many relational curves of recovery versus multi PV of water injected; it also shows the changes in pore structure of the cores. These changes are similar to those seen in pressure coring in the field. The reasons why such high recovery can be obtained and the large difference in recovery of different cores is explained.
New Insight Into Eromanga Basin Oil Saturations
Authors: Adams S. J.
Published: December 2007

The Eromanga Basin is an established Australian producing region with oil and gas found in several different Formations. At the request of an Operator, a project was undertaken to construct saturation-height functions for all the Eromanga reservoir units with a secondary objective being to define residual hydrocarbon saturations.

Initial investigations revealed many reservoirs with residual hydrocarbon columns, the significance of which had not been well understood. The residual hydrocarbons implied that imbibition, rather than drainage, capillary pressure curves were representative of water saturations in the reservoir. This insight suggested higher oil-in-place and reserves volumes than previously assumed since mobile hydrocarbons are present very close to the pressure derived Free-Water Level in imbibition systems.

When individual hydrocarbon Fields were considered, there were insufficient special core analyses to derive meaningful residual hydrocarbon or saturation-height relationships. However, on the basin scale, a significant volume of measurements had been acquired over a period of 22 years, albeit using different laboratories and a variety of measurement techniques. With knowledge of the measurement techniques and Formations sampled, the data were combined in such a way that consistent datasets were obtained for endpoint relative permeabilities and drainage and imbibition capillary pressure curves.

Interpretation of these datasets produced residual oil saturation and drainage and imbibition saturation height relationships. These relations were tested against those log-derived water saturations considered most reliable by the Operator, showing excellent matches. The model developed successfully described the water saturation distributions in the reservoirs tested in a manner not previously possible. Indeed, the use of the drainage and imbibition saturation-height functions together with residual hydrocarbon relationships provides a powerful tool to determine both static and dynamic fluid contacts, while checking the validity of wireline log-based water saturations.
The Future of Three Phase Separator Control
Authors: Charlton J. S. , Lees R. P.
Published: December 2007

In response to the expressed needs of Oil Producers, a novel instrument has been developed for measuring and controlling the performance of production separators. The instrument, known as a Density Profiler, provides the operator with realtime information about the vertical distributions of the various materials inside the separator: sand, water, emulsion, oil, foam and gas. This allows the operator to exercise fine control over the operation of the separator in a way never before possible. For example, the results of adding antifoam or demulsifying agents can be visualized immediately in the control room so that the effectiveness of these procedures can be monitored and appropriate action taken.

Over twenty profilers have been installed to date at locations around the world. They are highly reliable: the measurement probes have no moving parts and have no contact with the process fluids, thus minimizing the possibility of mechanical breakdown.

This paper describes the instrument and focuses on its unique mode of operation. Case studies are used to illustrate the substantial economic benefits that are realized from Optimization of the separation processElimination of unscheduled shutdownsOptimized levels of chemical additives leading to reduced costs.Elimination of oil spillsElimination of damage to downstream equipment.
Estimating Pseudopressure Function without Relative Permeability [kr(Sw)] for Two and Three Phase Gas Condensate Systems
Authors: Jokhio S. A. , Tiab D. , Baladi S. , Tunio A. H.
Published: December 2007

This paper introduces a new method of estimating pseudopressure function for gas condensate wells producing under two and three phase conditions. The proposed method utilizes pressure transient test data to get effective permeability as a function of pressure and then uses the definitions of two-phase and three-phase pseudopessure function and combines them to get the final pseudopressure for a given pressure value. Relative permeability as function of saturation can also be used, if available. The method is analogous to the pseudopressure of Ramey and Hussainy12 and Fevang and Whitson5. The proposed pseudopressure will help to estimate well liquid as well as gas IPR, well test analysis, well deliverability, and reserve estimation for gas condensate reservoirs. Finally a wide range of pseudopressure equations for Region-1, Region-2, and Region-3 for two-phase and three-phase gas condensate reservoirs, have been developed. Also, few examples are solved to show the use of the pseudopressure in estimating well performance.
Enhanced Gravel-Pack Completions Revitalize a Mature Sand-Producing Field — A Case Study
Authors: B. Md Noor Mohamed Zaini , Selamat Kasim B. , Salahudin Sharifudin , Kasim Abdullah b
Published: December 2007

The Dulang oilfield is located some 130 km offshore Terengganu in Peninsular Malaysia. The field is structurally complex. Production from the field began in March 1991, and oil production averaged 26 thousand STB/D. Production peaked at approximately 50 thousand STB/D.

As with other field developments in the Malay Basin, all the wells in Dulang field were completed without any sand control measures as sand production under normal drawdown or producing conditions was not expected. However, in the later stages of the field's life, a significant amount of sand production was observed. This condition gradually increased over time, resulting in reduced hydrocarbon production, additional costs for routine wellbore sand clean-outs, and platform shutdowns for surface vessel sand clean up.

To revitalize the field, a wellbore opportunity study was initiated in 1999. The objectives of the study were to 1) identify remaining reserves, and 2) identify new completion options to maximize recovery. The study identified three major scenarios that would improve oil production: Develop by-passed reserves behind casingReactivate idle wells that had been closed in as a result of sand production.Provide drainage points for undeveloped reserves.

From the proposed wellbore opportunities study, ten wells were identified for a workover campaign, and six wells were identified for infill drilling or sidetracks.

Sand control mitigation using a gravel-pack technique was identified as a requirement in the completion plan for the majority of the targeted reservoirs. However, the increase that would result in mechanical skin from sand control installation was also recognized. Hence, it was determined that the best approach for production optimization in these wells would be a combination of a sand control and a stimulation technique. Several technologies, which included frac and pack, extension pack with conductivity enhancer, and high-rate water pack (HRWP) gravel packing were identified. The use of a special completion tool was also identified to enable greater flexibility on short string selective production in multi-zone gravel-packed wells.

The combination of sand control and stimulation techniques (frac pack, extension pack and high-rate water pack) has successfully increased the productivity and prevented sand production in the Dulang wells.
Investigation for Mature Minas Waterflood Optimization
Authors: Hendih Agus Rahardja , Rinaldi Imran , Williams Lawrence Lee
Published: December 2007

With a recovery factor of ~51% and watercut in excess of 97%, the Minas Field in Sumatra Indonesia can certainly be categorized as mature field. Recently, the field has experienced a steep production decline, along with increased operating costs. As a result, a waterflood optimization study was initiated. This paper discusses the reservoir simulation to optimize the waterflood operations. The simulation, a sector model for sections 8C, 8D, and 8E, was used to test various prediction schemes such as pattern realignment and infill drilling. A seven well infill program is in progress to test for unswept oil.
Possible Utilisation of CO2 on Natuna's Gas Field Using Dry Reforming of Methane to Syngas (CO & H2)
Authors: Hanif A. , Suhartanto T. , Green M L H
Published: December 2007

One of the major natural gas reserve in Indonesia is found in the Natuna "D-Alpha" gas field. This is not only a large gas deposit (222 TCF) but is also interesting because it is composed predominantly of CO2 (71%). The last development scheme proposed by the oil companies Exxon and Pertamina for the utilisation of this gas, before the crisis of 1997, was for the CH4 to be sold as LNG, while the CO2 was to be injected back below the ocean floor. However, the marketing of natural gas depends on long-term and high-risk contracts or requires strong commitment between the producer and the buyer, even long before the development stage.

An alternative marketing strategy would be to convert the natural gas mixture to syngas (CO + H2) by the partial oxidation and dry reforming of methane with carbon dioxide or steam reforming and CO2 reforming; the syngas can then be used for the production of a wide variety of chemicals and fuels using gas-to-liquids (GTL) technology, e.g. Sasol or Shell's SMDS.

This has three major advantages compared with the LNG route: i) less separation stages will be needed and the cost of gas injection below the sea floor will be lower, since there will be much less CO2 remaining after the reforming process; ii) dry reforming is an effective way of incorporating CO2 in the products, which will eventually end up, for example, as fuel powering an engine; and iii) the price of the end products are much higher and easier to market as compared with LNG. In this study, it will be shown that molybdenum and tungsten carbide catalysts are active and stable for the process of partial oxidation and methane dry reforming to syngas using a feedstock of high CO2 content natural gas, such as that found in the Natuna ‘D Alpha’ field, Indonesia.
Transforming Conventional Wells in Mature Basins to Modern Bigbore Producers by Applying Solid Expandable Tubulars (SET)
Authors: Nor Norlizah Mohd , Huang Edmund , Hon-Voon Chin
Published: December 2007

Conventional gas development wells in prolific carbonate reservoirs before bigbore completions were introduced do not produce to full potential due to tubing constraints. This phenomenon is observed today in several mature, carbonate basins offshore Malaysia developed back in the early 1980s. At that time, the typical tubing configuration was a 7" completion string run in 9 5/8" production casing. This configuration limits subsequent tubing change out workover options to 7 5/8" tubulars resulting in only a modest 10% gain in well capacity through improved outflow performance.

The advent of solid expandable tubular (SET) technology in the new millennium has opened up a revolutionary possibility for transforming a conventional well with 7" tubing to a modern bigbore producer. The concept involves installing and expanding a long section of 7 5/8" solid expandable tubulars inside 9 5/8" casing and using the SET as a gas flow conduit. For a mature gas field offshore Sarawak where this concept was applied in a pilot well, such a well transformation yielded a production conduit with an internal diameter 24% larger than conventional 7" tubulars, a 61% increase in flow area, and a significant increase in well production.

Results of this field trial carried out to test this novel re-completion concept in a gas field offshore Sarawak showed a 40-50% increase in well deliverability. The technical concept was proven successful, and it is now planned to implement this novel SET re-completion design in other tubing constrained gas wells in the area.

This paper will present the results and economic benefits of this field trial, which is the first of its kind in the world. Details encompassing the conceptual solid expandable completion design, modifications and improvisation required for this first-of-its-kind SET gas well workover, and the required SET installation sequence will also be discussed.
Pressure Transient Analysis in Gas Condensate Reservoirs Producing Under Three Phase Flow Conditions
Authors: Jokhio S. A. , Tiab D. , Baladi S. , Tunio A. H.
Published: December 2007

This paper shows how to establish correlation between effective permeability as a function of pressure using well test analysis techniques in three-phase gas-condensate systems. Rigorous mathematical treatment led to correlations to estimate pseudopressure for gas condensate fluids that also use surface production data. The main purpose of developing correlation from well test analysis techniques is to use it in well performance analysis in such systems. Thus pressure transient techniques are helping to establish the flow behavior of gas condensate systems in their later life. Reservoir properties can also be estimated, however, to estimate absolute permeability, knowledge of relative permeability is required.

Three-phase gas condensate systems include water producing gas condensate reservoirs. Such wells are often equipped with artificial lift to unload the produced water. To model such a three-phase flow, relative permeability curves are needed. Getting relative permeability curves becomes further demanding when reservoir conditions of pressure and temperature coincide with near critical conditions. Analysis of pressure data in such multi-phase systems requires the exact knowledge of the individual phase surface rate, which itself is a demanding task and requires the separator and stock tank properties of gas and liquid phase. In this paper we have eliminated the knowledge of individual phase surface rate. Instead, we have developed models that use the surface measured rate of these phases.

Finally, an example is solved to show the use of the new technique developed.
3D Generalised Inversion (AVO, AI) as Direct Input to the Reservoir Model. Deepwater Exploration Offshore North West Borneo, Malaysia – A Case Study.
Authors: Reymond S. B. , Johnson T. E. , Lucas N. , Davies H. , Voon J. W. K.
Published: December 2007

The need to rapidly produce a notional field development plan, to reduce costs and cycle-time has driven a fast-track reservoir characterization and reservoir model-building project for one of many fields offshore North West Borneo, Malaysia. The objectives of the study have been defined based on the deliverables stated by the reservoir engineers. Considering the list of data and limited time available, an efficient generalised inversion workflow was designed to process a large volume of deepwater 3D seismic data with a single exploration well to: Locate and map all sands (3D geobody identification) versus non-reservoir rocks.Sub-divide reservoir sands into 4 lithofacies (well log neural net based calibration).Propagate 4 lithofacies to entire reservoir volume (within two fluid types).Integrate the fault framework with the sand and fluid distribution to build a first pass reservoir model.Include multiple realizations to manage uncertainty.Check sand connectivity and compute volumes of reserves in place.

An innovative combination of 3D geostatistical and neural network techniques was used both for the well log data and for 3D seismic attributes (AVO, Acoustic impedance and dipazimuth combinations) to map the spatial distribution of the sand and their lithofacies.

The results of the calibrated and quantitative generalised inversion were used in four different modes to assess the best way to build a first pass reservoir model and compute independent reserves within a short time-frame.

This case study illustrates how a purposefully designed 3D/3D reservoir characterisation workflow can reduce the time required to build a first pass static reservoir model and how a similar process can be applied to other complex deepwater hydrocarbon accumulations. It focuses specifically on the different ways a static reservoir model can be built from 3D seismically derived volumes (3D/3D, Hybrid and grid-based).
New Insights into Water Control - A Review of the State of the Art
Authors: Di Lullo Gino , Rae Phil
Published: December 2007

It could be argued today that oil companies would be better described as water companies. Total worldwide oil production averages some 75 million barrels per day (BOPD) and, while estimates vary, this is associated with the production of 300-400 million barrels of water per day (BWPD). These values of approximately 5-6 barrels of water for every barrel of oil are quite conservative. In the United States, where many fields are depleted, the ratio of water-to-oil production is closer to 9-to-1. In some areas around the world, fields remain on production when the ratio is as high as 50-to-1.

Water production is always a harbinger of problems in an oil well. It can cause scaling problems in susceptible wells, induce fines migration or sandface failure, increase corrosion of tubulars, and kill wells by hydrostatic loading, amongst other things. Thus, while water production is an inevitable consequence of oil production, it is usually desirable to defer its onset, or its rise, for as long as possible.

Numerous strategies, both mechanical and chemical, have been employed over the years in attempts to achieve this. Simple shut-off techniques, using cement, mechanical plugs and cross-linked gels have been widely used. More exotic concepts, like relative permeability modification (RPM), have also been applied with varying degrees of success.

This paper reviews the traditional techniques and proposes some new methodologies and technologies that can be used in the design of RPM treatments, in particular. New insights offered in this paper have been gained from the design and analysis of various experimental treatments around the world.

The paper includes several of these, as case histories, to support the concepts and conclusions.
Minimizing Coring-Induced Damage in Consolidated Rock
Authors: Hettema M. H. H. , Hanssen T. H. , Jones B. L.
Published: December 2007

During a successful coring operation some 720 meter of continuous core hasbeen taken with full recovery. The main purpose of the core is to obtainmaterial for rock mechanical testing. To minimize coring-induced damage, asystematic and detailed planning is made for all stages of the coringoperation. New models are developed to avoid core damage due to core bendingduring retrieval through a curved wellbore and to determine the maximumtripping velocity for core retrieval without harmful over-pressurization.Preliminary laboratory test results indicate a high core quality.
Deformation Analysis in Reservoir Space (DARS): A Simple Formalism for Prediction of Reservoir Deformation With Depletion
Authors: Chan A. W. , Zoback M. D.
Published: December 2007

We introduce a formalism, Deformation Analysis in Reservoir Space (DARS), to quantitatively predict the degree of compaction and potential for induced faulting in a depleting reservoir. Compaction occurs when the stress state exceeds the end cap (or critical state) of a formation at any given porosity. For reservoirs in which the vertical stress is larger than the two horizontal stresses, there is also a potential to induce normal faulting in a depleting reservoir when the change of minimum horizontal stress, ΔSh, exceeds a critical fraction of ΔPp (the change in formation pressure due to depletion). The stress path defines the change in horizontal stress with depletion (A=ΔSh/ΔPp). Utilizing relatively simple laboratory experiments, we transform the end caps from laboratory space into reservoir space (DARS) such that production data can be evaluated directly to study the evolution of the deforming reservoir due to production. Field X in the Gulf of Mexico is examined in the context of the DARS analysis. The analysis shows that the initial state of the reservoir was such that normal faults present in the field were active. However, production-induced normal faulting is not likely to occur. Deformation is dominated by compaction. Our analysis estimates that porosity of the formation was reduced from about 23% to 21%, while the permeability was reduced from about 230md to 50-140md.
A New Age in Well Perforating History - Evolving from Roman to Gothic?
Authors: Guinot Frédéric , Papanastasiou Panos , Grove Brenden , Dzialoszynski Arnaud
Published: December 2007

This article presents numerical calculations that show that shooting elliptical perforations can prevent or delay sand production by modifying the state of stress around the perforation tunnel. Elliptical perforations will allow for greater drawdown values and larger depletion before sanding. In formations with anisotropic permeabilities, elliptical perforations could also significantly improve well deliverability. Explosive and charge design technology has been investigated and show the feasibility of properly creating and orienting elliptical perforations to shoot these new elliptical tunnels.

The switch from cylindrical to elliptical perforation tunnels implies a change in mentality similar to when Abbot Suger, getting away from the Roman arch, introduced Gothic architecture to Western Europe. This article uses the analogy of XII to XVth century architectural developments to present and justify attractive and feasible new ideas on well perforation.
Model Identification with Fuzzy-Optimisation Techniques in Geological Data Mining
Authors: Finol Jose , Buitrago Saul
Published: December 2007

Zadeh's proposal of modelling the mechanism of human thinking with linguistic values rather than ordinary (crisp) numbers led to the introduction of fuzziness into statistical and dynamical modelling and to the development of a new class of systems called fuzzy models. In fuzzy modelling, one of the most important problems is the identification of a predictive model from a set of measurements. In a similar way, Data Mining is aimed at sieving data from large databases, data repositories or data warehouses in order to discover interesting knowledge such as pattern associations, trends, and significant structures. Therefore, many similarities can be found between data mining and fuzzy model identification, specially when one has to deal with imprecision and noise in very large data sets. Two of these similarities correspond with the inverse problem of variable selection and parameter identification in order to select the most appropriate predictive model that fits a set of observed (training) data.

In this paper we introduce a data mining procedure which uses global optimisation methods, that seeks for useful features, pattern relations, and functional representations in order to derive fuzzy models from large data sets, that characterise the unknown functions as precise as possible. The effectiveness of the proposed data mining method is proved using petrophysical data (core plug measurements) from two oil wells in the Maracaibo Basin.
Application of Coiled Tubing Technology to control water production in the Greater Burgan Field of Kuwait
Authors: Al-Ali Abeer Khalid , Vegesna Raju , Redlich Lyle
Published: December 2007

Rig workover is the most commonly utilized technique in water shut-off applications for water drive reservoirs. Implementation of a rig workover consumes considerable amount of time with significant cost. Furthermore, it will have an adverse effect on well availability and production.

Alternatively cost effective coiled tubing technology for water shutoff was prformed in the Greater Burgan Field successfully. This paper explains the implementation of the same through case histories with diagnosis before and after each job.
Improving Borehole Quality and Drilling Efficiency with a New Suite of Drilling Tools
Authors: Russell Richard
Published: December 2007

In an ideal world, a borehole would be a perfect cylinder with a smooth, frictionless interior and would retain the original diameter of the drill bit. However, in the real world, a perfectly cylindrical borehole can never be achieved. A number of factors contribute toward this less-than-perfect borehole, such as formation instability and interactions between the drilling and formation fluids. Another major contributor is the actual mechanics of the drilling process and the resulting effect most types of drilling have on the borehole geometry.

This less-than-perfect borehole manifests itself in a number of ways, all adversely affecting the efficiency of the drilling process and all increasing costs. These problems include reduced drift, increased torque and drag, poor hole cleaning, slower drilling rates, and increased downhole tool failures.

The phenomenon of borehole spiralling is being increasingly recognised to be a result of the inefficiencies of conventional drilling assemblies. Short-pitch micro-tortuosity and the mechanisms that cause it are responsible for many of the problems described above. It has been found that borehole spiralling can largely be eliminated with a new suite of drilling tools. This suite of tools has adopted a new drilling assembly design utilising a long gauge bit and the ‘point-the-bit’ concept of directional control.

The application of this suite of tools can have a significant effect on drilling operations, especially in the field of horizontal and extended-reach drilling where the improvement in hole quality can impact well design and economics.
Integration of 3D Seismic with a Reservoir Model for Reservoir Characterisation
Authors: Melville Peter D. , Guruswamy Srikanth
Published: December 2007

This paper presents a methodology and results of the integration of 3D seismic data with well log data and simulation model of a giant carbonate reservoir. The work highlights the vertical scale differences between seismic and reservoir models and brings forward a method to match the scale and resolution. Seismic reservoir characterisation of a field with a large number of wells with different vintage and quality data requires statistical methods to discriminate valid data to build AI-Porosity transforms. The method adopted for integration has allowed a better understanding of the complex wrench faulting, and improved the porosity description of the reservoir. 4D fluid effects have also been observed as a result of combining well and seismic with simulation data.
Fast and Robust Computation of Effective Permeabilities
Authors: Nomura M.
Published: December 2007

The current requirement of geologic detail to be built into reservoir descriptions has been exceeding the computational capabilities of reservoir simulation due to a need of huge number of simulation grids. This has motivated the development of a variety of upscaling techniques for flow simulation.

This paper presents an efficient upscaling method effective for an oil-wet heterogeneous reservoir, which offers a means of simulating multiple geostatistical realizations. A new effective permeability correlation is developed through application of one of the non-parametric regression techniques to the results of intensive numerical experiments. The developed empirical correlation enables us to compute effective permeabilities fast and accurately for a wide variety of heterogeneous permeability fields from layered to random system and can be easily extended for averaging two-phase flow properties under viscous limit or capillary limit.

The paper describes the developed technique in detail and demonstrates how the overall upscaling procedure can be speeded up with the desired accuracy.
Integrated Development Approach For A Mature Oil Field
Authors: Murty Challa R. K. , Al-Haddad Abdulla
Published: December 2007

Bahrain field, discovered in 1932, is a highly faulted asymmetrical anticline trending in North - South direction (Fig.1). There are as many as seventeen oil producing and three gas producing reservoirs within Jurassic to upper Cretaceous formations apart from the Khuff gas zones below in Permian limestone formations (Fig-2). These reservoirs occur with divergent lithology, rock and fluid properties. Some of them are saturated while some are highly under saturated. Some of them are oil wet and some water wet. They operate under various drive mechanisms and pressure maintenance schemes. Gas injection in Mauddud, which is one of the major oil producing zones in Bahrain field, has been in operation for the last 65 years. Gas injection in Arab-D is in progress from 1986. Pilot peripheral water injection is in progress in wara sands in NE area of the field since 1995. Additionally, different production mechanisms like gas lift, pumping and stop cocking for GOR control is applied. The field being mature and structurally complicated naturally demands an integrated approach for effective reservoir management to ensure maximum recovery. Due to application of diverse reservoir management techniques, reservoir characterization, Geo statistical application for anisotropy and increased accuracy for simulation, the field has been producing with minimum annual decline (Fig-3). By integrating the Geological, Seismic and reservoir / production data the productive limits of various reservoirs have been extended adding substantial reserves. This paper briefly discusses the approach adopted in the effective reservoir management of this giant mature oil field.
Sequence Stratigraphy of the Khuff Formation Comparing Subsurface and Outcrop Data (Arabian Plate, U.A.E.)
Authors: Strohmenger Christian J. , Alway Robert H. S. , Broomhall Robert W. , Hulstrand Richard F. , Al-Mansoori Abdulla , Abdalla Azhari A. , Al-Aidarous Abdullah
Published: December 2007

The Khuff Formation can be described as a second-order transgressive-regressive sequence. The transgressive sequence set comprises Khuff third-order composite sequences KS7 through KS5 and the third-order lowstand/transgressive systems tract of KS4. The regressive (highstand) sequence set comprises the highstand systems tract of KS4 as well as Khuff third-order composite sequences KS3 through KS1. Major Khuff gas reservoirs are associated with the second-order highstand sequence set.

Khuff analogues have been studied in the Musandam Peninsula at Wadi Bih and Wadi Hagil (Ras Al-Khaimah, U.A.E.) and are compared to well data from Abu Dhabi (U.A.E.). The outcropping carbonates of the Permian Bih and overlying Hagil formations as well as the lower part of the Triassic Ghail Formation are interpreted to be time equivalent to hydrocarbon bearing carbonates and siliciclastics of the subsurface Khuff of the Arabian Platform.

Khuff Sequence KS1 corresponds to the lower part of the Ghail Formation. The Hagil Formation comprises Khuff sequences KS2 and KS3. Khuff sequences KS4 through KS7 are interpreted to correspond to the Bih Formation. At Wadi Bih the Permian-Triassic Khuff sequence boundary SB1 at the base of the uppermost Khuff Sequence KS1 is well exposed.

It is marked by a karst breccia overlain by oncoid packstones of the Ghail Formation. In Wadi Bih as well as in Wadi Hagil, Khuff sequence boundary SB3 is interpreted to correspond to an exposure surface showing mud-cracks and possible raindrop imprints. This sequence boundary also marks the boundary between the underlying Bih and the overlying Hagil Formation.
Characterization of Tar From a Carbonate Reservoir in Saudi Arabia: Physical Aspects
Authors: Harouaka A.S. , Mtawaa B. , Nofal W.A.
Published: December 2007

A detailed physical characterization of tar from a carbonate reservoir in Saudi Arabia was made to evaluate its mobility and ways of establishing contact between the lighter oil and its aquifer. Density and viscosity measurements were carried out on several tar samples, under simulated reservoir conditions of pressure and temperature. Other physical parameters such as simulated distillation, pour point and penetration index were also experimentally determined.

Tar physical properties were found to vary with depth and area within the same field. The obtained experimental results showed a gradual increase in density and viscosity from the tar/oil contact towards the tar/water contact. This increase was much more pronounced in the neighborhood of the tar/water contact. Density and viscosity of tar diluted with toluene were in excellent agreement with those of pure tar.

The density of non preserved tar varied between 0.956 g/cc at 200°F and 1.008 g/cc at 76°F while that of preserved tar varied between 0.944 g/cc at 200°F and 0. 991 g/cc at 76°F. The tar samples analyzed appear to behave as Newtonian fluids.

Introduction

The present paper discusses detailed physical characterization of several extracted and RFT bottom hole tar samples obtained from a carbonate reservoir in Saudi Arabia. The chemical aspect has already been presented elsewhere [1]. Tar is defined as extra heavy oil with a gravity ranging between 29 and 9°API albeit the distinction between heavy oil and tar is rather shady.

Tar mat is present in abundance in the Middle East, Africa and elsewhere. In recent publications Kaufman et al. [2] mentionned the presence of a tar zone at the water/oil contact in Burgan field. This has been known for a long time. However, to ascertain lateral and vertical delineation of the tar zones appear to be still unresolved. Thick tar zones identified through visual observation and Latroscan analyses of weathered core samples were reported in the Raudhatain field [3].

A tar mat is generally a thick column laying between an aquifer underneath and a much lighter oil reservoir above. This peculiar location poses a host of challenging problems for an efficient management of the lighter oil and ultimately for a proper management of the tar zone itself [4].

In this study, density of tar was measured with a digital Anton Parr densiometer having a maximum temperature range of 300°F and a pressure limit of 6000 psi. Based on these measurements, specific gravity and API gravity were determined.

A rolling ball viscometer was used to measure tars viscosity at elevated pressures and various temperatures. The effect of visbreaking or permanent viscosity reduction due to thermal alteration has also been examined.
Is Bioremediation A Solution for the Treatment of Oily Waste?
Authors: Chaîneau Claude-Henri , Setier Jean-Claude , Morillon Anne
Published: December 2007

As a general trend in the Oil and Gas industry, the treatment and disposal of waste is a serious environmental issue. During Exploration and Production activities, drilling operations may generate oily waste as drill cuttings. Hydrocarbons may also enter the soil ecosystem in the case of accidental oil pollution. These wastes are usually disposed of in a variety of methods including thermal and physico-chemical treatments. Over the last ten years, bioremediation has been considered as a possible alternative to « classical » treatments since it has been well established that hydrocarbons are prone to be biodegraded. This paper presents the scientific principles of bioremediation and on-site applications illustrated with cases of studies: landfarming of drill cuttings, biocomposting of hydrocarbons-polluted soils and oily cuttings, natural attenuation hydrocarbons-polluted soil, development of biodegradable oil-based mud and phytoremediation processes. This publication aims at demonstrating that oily waste can be depolluted by biological treatments; however, in-situ biodegradation must not be over-estimated. Our experience demonstrates that in certain local conditions the biological activity is not efficient, and the treatment duration becomes a critical issue. Systematically, a detailed waste management study, including feasibility, cost, logistics and regulations has to be completed to verify that bioremediation is the key solution for the oily waste treatment and disposal.
Wet Gas Compression – A Logical Step to Follow Multiphase Boosting
Authors: Müller-Link D. , Brandt J. U. , Reichwage M. , Schröder G.
Published: December 2007

Multiphase boosting in oil and gas production may typically be characterized by:

– Slug flow occurrence possible, and – GVF at inlet conditions higher than 50 %.

The physical challenge for the equipment in use is the strong variation of the GVF (Gas Void Fraction), leading to transient flow conditions at the pump's inlet. However, when the GVF during the entire operations constantly exceeds 98 %, control of heat generation becomes a further challenge. Suitable answers need to be found for the following questions like

– How can wet gas compression best be described? – Is this an efficient way to compress wet gas? – What about installation economics?

A technical issue for wet gas compression is the shaft sealing. Available standard seals can either cope with liquid or gas, but not with varying fractions of both. Other limiting factors are differential pressure, lubrication characteristics of pumped liquids, solids, and circumferential velocity.
Applied Carbonate Stimulation – An Engineering Approach
Authors: Sengul Mahmut , Remisio Luis H. A.
Published: December 2007

Carbonate reservoirs are quite tolerant to problems originated by poor stimulation practices. Therefore, acidizing of carbonate formations has been overlooked in many aspects. The objective of this paper is to provide a comprehensive reference material that will help the matrix stimulation designers to quantify formation damage, select optimum fluids for carbonate reservoirs, design and place proper treatment, hence stimulate the carbonate reservoirs in engineered way.

Well operations can damage the formation, from the moment the first drill bit penetrates a permeable formation to the end of its productive life of it. Most types of damage reduce the formation's natural permeability. Identifying the causes of formation damage and how to prevent it have been the subjects of much research, but well operations still continue to cause some degree of damage to the formation in the near-wellbore region. Formation damage has a dramatic, adverse effect on the flow of hydrocarbons into the wellbore, because of plugging or partial plugging of perforations, or plugging of the rock structure by debris from the well and from well operations.

Stimulation design for horizontal wells and surprises in some field results indicated the need for systematic analysis of stimulation process in ADCO fields. Therefore, an applied study has been conducted to address the issues related to carbonate stimulation and set field procedures, best practices for the carbonate reservoir stimulation. Reservoir characterization part of the project included sampling of representative cores from the producing and injection formations in all fields. A total of 287 core samples have been collected. Thin section, acid solubility, iron content, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analysis have been performed on these samples. Existing acid recipes checked and validated against mineralogical composition, acid solubility, and iron content of particular layers and new recipes prescribed accordingly. A detailed questionnaire sent to major oil companies and service providers. Replies processed and findings of the project have been documented as Best Practices.
Lessons Learnt in Planning and Implementation of a Successful Lower Burgan Horizontal Well in North Kuwait
Authors: Azim Shaikh Abdul , Attid Juma , Smith Martin , Al Hajeri Mubarak , Moritz Lee , Ali Mohammad
Published: December 2007

The first horizontal well (RA-156) was successfully drilled and completed in the Lower Burgan sandstone reservoir of Raudhatain Field, North Kuwait. The objective of the well was to produce water-free (dry) oil at high rate from a difficult-to-reach portion of the reservoir. Dry production is especially desirable due to constrained wet crude processing capacity. The well successfully delivered the expected rate, making this well the highest-rate producer in the field.

Uncertainty in structure and stratigraphy are inherent in the area due to weak/noisy seismic reflections and rapid change in reservoir facies in marine-influenced channel deposits. Innovative correlation schemes and detailed reservoir description were used to reduce uncertainties. The trajectory was designed along the direction of maximum principal stress to overcome borehole instability problems. The horizontal-section was drilled with minimum overbalance to avoid potential reservoir damage.

Well-site data including logging-while-drilling (LWD), cuttings, and drilling data were used to identify faults along the well and to optimize the selection of kick-off point (KOP) and end-of-build (EOB). Subtle markers were identified while drilling, and the trajectory was geo-steered within the channel sand while maintaining maximum standoff from a rising oil-water contact (OWC). Absence of shale along 3000-ft of horizontal/high angle section was instrumental in faster drilling. Low mud weight was used to minimize potential formation damage caused by prolonged formation exposure to high-density mud.

The completion of the well was designed to deliver long-term high-rate dry oil production. The horizontal section of the well was cased and cemented to ensure zonal isolation. A perforation strategy was developed and implemented to encourage even flow from the reservoir along the productive section to avoid local water coning, facilitate future well intervention and increase productivity index (PI) by reducing potential skin. External casing Packers were used to further ensure isolation of across a fault in the horizontal section. 5-1/2" tubing with appropriate jewelry was selected to accommodate the expected high rate and to ensure well integrity.

The details of the multidisciplinary approach and the lessons learnt during planning and implementation of this horizontal well are summarized in this paper.