bluuebunny/crossref_metadata_2025 huggingface dataset:
The Offshore NDE and Stress Monitoring of Gas Riser Welds
Authors: Light M. F. , Frazer I.
Published: December 2007

In 1989 a series of study work carried out by Conoco (UK) Limited identified that a number of gas risers could be susceptible to fatigue decay in the region of the riser elbow.

It was considered at that time that further analytical analysis would not add greatly to the confidence in the methods of assessing the long term integrity of these riser elbows.

A decision was made to undertake a work programme that involved detailed underwater NDE inspection of the riser transition welds in question, combined with an offshore programme of stress monitoring. This would provide accurate information on the exact level of wave induced stressing which could then be processed into weld fatigue data.

The offshore work programme was carried out in 1989 and 1990 and the resulting data was used to assess the likelihood of fatigue failure of the risers using probabilistic techniques.

This paper outlines the riser inspection and monitoring programme together with the results and subsequent conclusions.
Testing High-Pressure Gas-Condensate Wells in the UKCS: A Case History
Authors: Wood D. J. , Whitehead N. J.
Published: December 2007

In recent years an increasing number of exploration wells in the North Sea have targeted deep, high pressure, gas condensate prospects. BP Exploration has recently successfully drilled and tested an abnormally pressured Jurassic reservoir with a formation pressure of approximately 15,900 psi and a temperature of 375°F.

Well 22/28b-2 was spudded in October 1988, but following the Ocean Odyssey incident the well was suspended after setting 9-5/8" casing. The well was re-entered in May 1990 using the semi-submersible rig Sedco/BP 711 and drilled to a TD of 5477 mBRT. The reservoir interval was successfully tested from the semi-submersible rig and a maximum shut-in wellhead pressure of 12,300 psi was recorded.

This paper outlines the testing philosophy adopted and discusses the planning, procedures and equipment requirements. It also indicates how the test design was modified in light of changes in the well condition discovered on re-entry.
Beryl Alpha: Increase in Deck-Load Capacity
Authors: Galbraith D. N. , Hodgson T.
Published: December 2007

Fifteen years after the installation of the Beryl Alpha Condeep platform, a programme to upgrade the topsides facilities was commenced. This upgrading increased the overall design weight of the topsides by some 17%. Due to the modular nature of the additional facilities, weight increases of several hundred tonnes each are applied at discrete points around the deck structure.

Prior to this upgrade, Mobil North Sea Limited (MNSL) had commenced the development of reanalysis models of their structures, including the Beryl Alpha deck. A complete reassessment of the strength of the deck was undertaken using detailed finite element analysis and contemporary code checking methods. The methodology used in the checks combined the application of appropriate codes, recent theory, experimental results and both linear and non-linear buckling analyses. Whereas simpler techniques would have suggested a requirement for considerable stiffening, this methodology demonstrated that even the substantial additional loads from the upgrade could be carried with only minor and localised strengthening being required.

This paper discusses the methods used together with the approach adopted for the design of stiffening at minimal cost.
Innovative Technologies Bring New Economical Concepts for Developing Offshore Marginal Fields
Authors: Giannesini J. F. , D’Hautefeuille B. B. , Thomas P. A.
Published: December 2007

After stressing the importance of marginal field developments, especially in the North Sea, the paper describes a new concept based on innovative technologies.

The concept makes use of the multiphase pumping technology recently developed by the oil industry, combined with a small floating support and retrievable flexible fines.

After describing the technical aspects of the system, the paper gives its main advantages compared to traditional development schemes.

A preliminary economical analysis, based on field data, clearly shows the areas of application and the benefit for the oil operator.

The paper concludes on the potential interest of the system to North Sea fields.
Diagnosing Elusive Flow-Induced Turbomachinery and Piping Dynamics Problems
Authors: Jungbauer D. E. , Harris R. E.
Published: December 2007

With the need for increased capacity at existing facilities and the design of larger new systems, flow-induced dynamics problems associated with turbomachinery and piping systems have become more common. These phenomena can result in significant noise and vibration related problems, and potentially lead to fatigue failures. In this paper, a brief review of the characteristics of flow-induced vibration and acoustic phenomenon, as applied to turbomachinery, is presented. A select number of case histories involving on and offshore installations in Europe, the Middle East, and the United States will be presented and involve:

Vortex-excited acoustic resonances of pipeline or gas processing compressor inlet conditioning section. Flow-induced acoustic excitation of safety relief valve piping stubs resulting in excessive vibration and premature venting with loss in production. Acoustic excitation of compressor recycle piping caused by vortex shedding past piping discontinuities.

The importance of meaningful data collection and correlation with existing theory, and the modifications necessary for solution, will be discussed in order to enable design and operating personnel to gain insight as to the impact of flow-induced dynamics problems on safety, reliability, and maximum production.
An Analysis of Formation Damage by Completion Fluids at High Temperatures
Authors: Houchin L. R. , Baijal S. K. , Foxenberg W. E.
Published: December 2007

The use of high density brines has been a major factor in reducing formation damage during completion operations. However, recent studies have suggested that high-density brines can be potentially damaging. More specifically, CaBr2/CaCl2 brines (≥14.2 lbm/gal. [1702 kg/m3]) were found to reduce core permeability from 25 to 29 percent at relatively low temperatures (150°F/51°C). The literature does not address the effects of high-density brines at the elevated temperatures where they are typically in use.

A laboratory study was conducted to determine potential formation damage from high-density brines at temperatures of 250-400°F (94-204°C). Core flow experiments confirm that calcium containing brines produced the most damage at higher temperatures. In addition, at a threshold temperature of approximately 350°F (177°C) all brines have the potential to produce damage.

Numerous operational guidelines have been provided to predict damage potential and identify cost effective preventive measures when high reservoir temperatures are anticipated.
Fibre Optic Well Monitoring System
Authors: Bjornstad B. , Kvisteroy T. , Eriksrud M.
Published: December 2007

Alcatel Kabel in Norway is developing a downwell monitoring system for permanent installations, based on optical excitation and interrogation of micromachined resonant sensors. The optical measuring concept, integrated with fibre optic communication and in combination with silicon material properties, provide unique sensor system performance, which can meet the requirements of downwell monitoring.

The key components have been developed and comprises; sensor and sensor housing, fibre optic cable, fibre optic cable splices, fibre optic wet mateable connector, and optoelectronic equipment for system operation. The components have been fully characterised and tested in an onshore test well. The test results verify the inherent advantages of optical technology and demonstrate the system's high reliability potential and ability to function in high temperature applications.
The Future of UK Gas Marketing: Impact on North Sea Producers
Authors: Hallas P. A.
Published: December 2007

Traditionally, an oil company wishing to develop UK gas reserves almost always faced a protracted gas sales negotiation with British Gas. British Gas then had an effective monopoly in the resale of that gas to final consumers. This traditional pattern is now in a process of fundamental change, as a result oi recent UK gas market re-regulation and the emergence of a new large scale opportunity to sell gas for power generation.

The impact of these changes is still not very well understood outside a relatively small group of gas specialists – but is likely to be significant for British Gas, consumers and UK gas producers. This paper outlines the background to the recent changes, the possible future of UK gas marketing and the likely impact on gas producers in the North Sea.
Experimental Study of Gas Rise Velocity and Its Effect on Bottomhole Pressure in a Vertical Well
Authors: Skalle P. , Podio A. L. , Tronvoll J.
Published: December 2007

A 500 ft vertical well was used to study slip velocity of air in mud and pressure gradients through a 2.93" annulus (5.43 – 2.50") during continuous two phase flow in flowing liquids and in stagnant liquid columns. The well was instrumented to measure liquid- and air flow rate, surface back pressure and annular pressure gradients.

Tests were undertaken with a broad range of air and liquid rates, different liquid properties, and with the injection of air slugs at different rate combinations. It was possible to detect these slugs as they passed the pressure transducers in the annulus. Results were applied to determine gas rise velocity.

Correlation has been developed for gas rise velocity, which was used to estimate gas and liquid hold up. The in situ gas velocity and terminal settling velocity were determined for both dispersed bubbly flow and slug flow. The resulting pressure gradients have been compared to estimates from 8 different empirical correlations. The best results were obtained by using the Zuber & Findley correlation for holdup estimation with a gas holdup of 0.6 to distinguish the boundary between bubble and slug flow. This high transition value was mainly caused by the geometry of the well (tool joints) and partly by the rheology of the mud. A very good agreement between recorded and estimated downhole pressure was achieved, with a mean error of approximately 1% and a standard derivation of 2.9%.
A New Mechanism for Integrating Long Term Reservoir Predictions and Short Term Topsides/Compressor Performance to Produce Accurate Gas Production Forecasts
Authors: Kearns J. , Guinee M. J.
Published: December 2007

North Sea gas sales contracts are defined in such a way that a seller for the decline years of a gas supply must, on an annual basis, nominate expected short term production levels to his gas purchaser. Failure to meet these production targets can result in severe financial penalties. On the other hand, under nominating is detrimental to project economics. Reservoir models alone can be too coarse a tool to provide the necessary accuracy when looking forward only one or two years. Process systems and compressor performance also need to be modelled in order to more accurately define short term production potential. This paper describes a novel way of integrating long term reservoir predictions and short term topsides performance characteristics so as to provide an accurate nomination of gas production rate.
Stress and Strain Wearing Compressed Air-Breathing Apparatus
Authors: Puttiger P. H. J.
Published: December 2007

This paper describes a study carried out among 44 employees who use breathing apparatus in the form of compressed air masks during their work. The purpose of the study was to determine the extra load caused by working with compressed air masks during the performance of (simulated) tasks. The average exertion level demanded by the four tasks varies from 30% to 93% of the maximum load during cycle ergometry. The data relating to the extra load are obtained by recording heart rate using the Sporttester PE 3000 and by measuring oxygen uptake using a modified Oxylog apparatus. The duration of the tasks is also recorded.

The study results show that at a low level of exertion when working with compressed air equipment, the extra load gives no special cause for concern. At high exertion levels, the subjects adapt to the increase in the external load by taking more time to perform the task. This increase in the external load has the additional effect of reducing the available reserve capacity (cardiovascular and energetic).

When rescuing a victim, this could mean that the operation takes longer when compressed air mask equipment is used;it is then in the interests of both the victim and the rescue worker with breathing apparatus that the latter has an excellent physical work capacity.
Presence of Mercury in Natural Gas: An Occupational Health Programme
Authors: Gijselman P. B.
Published: December 2007

This paper describes the occupational health programme used to ensure that NAM and contractor personnel of the Nederlandse Aardolie Mij (NAM) exposed to mercury, common in Dutch gas, are adequately protected through the correct use of Personal Protective Equipment (PPE), proper instruction and suitable work procedures.

To avoid health damage due to mercury exposure during maintenance and shutdown activities the occupational health department of NAM set up a programme covering 3 activities: –monitoring of atmospheric air; sampling of inspired air during work, and measurement of mercury excretion in urine of workers–instruction of company and contractor personnel–consultancy during preparation of work instructions

The monitoring programme showed that, through correct use of PPE, staff do not exhibit mercury concentration levels exceeding the human toxicity limit (100 ug/g creatinine) even after exposure to mercury vapour concentrations above the TLV of 0,05 mg/m3.

The correct use of PPE is a result of the instruction programme which also promotes increased awareness for personnel of the harmful effects of mercury.

Finally, the provision of consultancy during the preparation of work instructions has contributed to various measures; for instance, staff wearing plastic (Viton) protective suits may not work longer than 2 hours continuously to avoid heat exhaustion.
The Analysis Of Drill Stem Test Pressures
Authors: Mahn F.H.
Published: December 2007

Procedures for the analysis of drill stem test pressures are developed. They are based on the solution for radial flow of a slightly compressible fluid from a radially infinite, homogeneous and isotropic reservoir into a finite well with a "skins". They differ from previously used methods in that they take account of variations in flow rate throughout the flowing period.

The formulas cover the cases of measured and unmeasured flow rates; a short flow period with a relatively long shut-in, comparable flow and shut-in periods, and multiple shut-in tests. They solve for fully built-up pressure, formation flow resistance (transmissibility) and skin pressure, formation flow resistance (transmissibility) and skin resistance, and for flow rates when these are not measured.

The procedures are quick and easy to apply, given the appropriate pressure measurements, although checking the validity of results lengthens pressure measurements, although checking the validity of results lengthens the calculations appreciably in one case. It appears that highly precise results are obtainable by these methods for most drill stem tests causing smoothly varying single phase flow in the reservoir.

Introduction

The purpose of this paper is to present methods for the analysis of drill stem test pressures, allowing for the large changes in flow rate which normally occur but are seldom measured. The analysis derives the parameters required both to predict performance for the interval tested parameters required both to predict performance for the interval tested and to estimate the pressure gradients caused by flow in the reservoir nearby.

Detailed analyses of drill stem tests have been made at the BP Research Centre and have shown that:

the peak flow rate usually is two to ten times the final flow rate. this flow rate variation has a considerable effect on the subsequent pressure build-up. the build-up is very sensitive to the final flow rate and the total production but is poorly sensitive to early flow rates. the rate of rise of pressure at the and of a flow period usually differs significantly from the rate of increase of the static head in the drill pipe, even for very low gas-oil ratio fluids such as water, when flow rates exceed a few tens of barrels per day.

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Environmental Risk in the Offshore Industry
Authors: Woods I. T. , Shirley D. , Bottelberghs P. H.
Published: December 2007

The subject of oil pollution of thesea by the offshore industry is topical as a result of recent incidents both in the U.K and overseas. Whilst these incidents have primarily involved crude carriers, it has led to pressure to quantify the risk to the environment from the offshore industry in general. Here a method for the assessment of the frequency and size of oil spills from offshore installations is presented. It relies on previously reported spills to determine spill size/frequency information for a range of offshore activities, such as transport by pipeline, drilling and processing. Modification factors are used solocal conditions, such as the number of wells drilled, throughput andwell depth, can be considered in the assessment of the oil spill riskfrom a particular installation.
Deep Water Oil Production System
Authors: Walker R.W.
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

The offshore industry is rapidly approach-a barrier that may be far more difficult to overcome than the problem of increasing water depth.

The cost of installation and operation of production facilities in deep water increases at such a rate that economics rather than technologies determine the real limits.

To date, substantial research has been directed toward the development of deep water production systems. Unfortunately, the production systems. Unfortunately, the resulting systems consistently fail to achieve economic acceptability. It therefore appears that the question is not "can production systems be devised for deep water locations" but rather, "can the industry afford deep water production systems". production systems".The objective of this presentation is to outline a program that meets the operational and economic limits associated with deep water drilling and production.

Introduction

At the present time the oil industry is entering a new phase of offshore production.

The past years have seen a development of drilling and production techniques that have made possible the recovery of reserves in water depths of 300–400 ft. These reserves are being produced today by fixed platforms as well as produced today by fixed platforms as well as ocean floor installations. As production from deeper water is contemplated it becomes immediately apparent that the increase in cost for fixed structures directs attention toward alternate systems.

Drilling from floating structures and completing the well with all components located on the sea floor has been common within the industry for a number of years. The full economic advantage of the ocean-floor completion has not been realized primarily because a fully integrated production system has not existed.

Designers and manufacturers of subsea equipment in shallow water have in the past been confronted with a marginal advantage, if any, over platform installations. A preference on the part of operators for the more accessible and familiar equipment used on fixed platforms has also served to retard the acceptance of sea floor production equipment. With the advent of installations in deeper water the cost differentials between fixed platforms and sea floor production units become significant and greater production units become significant and greater consideration must be given to the subsea installations.
The North Sea Bird Club: Ten Years of Recording in the North Sea
Authors: Doyle P. A. T. , Gorman M. L. , Howe S. , Patterson I. J.
Published: December 2007

The creation of a club for the purpose of encouraging oil and gas workers to watch birds may not at first seem a viable proposition. To the layperson, birds offshore conjures up an image of hundreds of "seagulls" following fishing boats, and very little else. Also, the act of birdwatching is not seen as a typical offshore worker's activity.

Anyone who has worked on an installation offshore and who has any interest in wildlife will be aware of the occasional presence of land-birds. Two decades ago, prompted by some keen offshore workers, a single oil company set up a monitoring programme, which quickly became popular with a number of its employees. Birds seen offshore were recorded on data forms and collected together. At this stage the club was purely another recreation facility; however, when the data were collated it was soon realised that installations offshore were being used as "staging posts" by birds on migration, and that the information being collected would be of great interest in the study of bird movements.

All over Britain, at strategic points on the coastline, there are bird observatories which record the arrival and departure of migrating birds. The presence of several hundred solid structures up and down the North Sea, which are used by birds en route, represents a huge, unique bird observatory, capable of uncovering facts about bird migration which have long eluded land-based scientists.
Environmental Applications of Plasma Spectrometries Within the Oil Industry
Authors: McCourt C. B. , Price R. J. , John S. D. , Penny D. M. , Clarke L. J.
Published: December 2007

Plasma emission and plasma mass spectrometries are elemental analysis techniques which have been widely exploited for environmental applications. Their effectiveness for such work is due to their truly multi-element nature, sensitivity and wide linear range. This paper provides examples within the context of the North Sea, of their exploitation for analysis of effluent waters, seabed sediments and crude oils.
Bioaccumulation From Mineral Oil-Wet and Synthetic Liquid-Wet Cuttings in an Estuarine Fish, Fundulus grandis
Authors: Rushing J. H. , Churan M. A. , Jones F. V.
Published: December 2007

The long-term effects of discharged oily drill cuttings on native fish populations are of major concern. This study investigates the uptake of oil and synthetic liquid by the mud minnow, Fundulus grandis. when exposed to three different concentrations of low-aromatic mineral oil-wet and synthetic liquid-wet cuttings in flow-through bioassay chambers.

Fish were introduced into the flow-through bioassay system and cultured for 30 days. Water, cuttings, and fish were sampled routinely for analysis. Fish samples were dissected; gut and tissue samples were analyzed separately.

Flow-through water was analyzed by extracting the water sampling tube absorbent. The cutting samples were analyzed by Soxhlet extraction. Fish tissue and gut samples were digested in sodium hydroxide and extracted with ether. The extracted organics in all the samples were analyzed by gas chromatograph!mass spectrometry.

Gas chromatograph!mass spectrometry identified uptake of the mineral oil in fish tissue and gut samples for all cuttings treated with mineral oil-based mud (MOBM). No uptake was measured in any of the tissue samples for all cuttings treated with synthetic liquid-based mud (SBM). An accumulation of synthetic liquid was only detected in one sample of fish gut from the lowest concentration of SBM. The contrast in uptake between the mineral oil and the synthetic liquid is perhaps due to the greater molecular size of the synthetic liquid over that of the mineral oil. It is hypothesized that the greater molecular size of the synthetic liquid restricts uptake by gill and digestive structures.

During the study, there was little migration of either base fluid from the cuttings. Hydrocarbon amounts in the water samples generally decreased during the 30-day test period. All collected organics were liberated as negligibly soluble microdroplets. Tests indicated no selective solubility of released microdroplets and little if any biodegradation for both SBM and MOBM.
Marine Toxicity and Persistence of Surfactants Used in the Petroleum Producing Industry
Authors: Maddin C. M.
Published: December 2007

This paper presents a survey of marine toxicity and biodegradability data for surfactants used in the petroleum industry.

Surfactants are key chemicals in the formulation of products such as emulsifiers, demulsifiers, dispersants and inhibitors. They are also used directly as foaming and defoaming agents. Because they function at low concentrations, below 1%, and have a tendency to adsorb on solid surfaces, their long-term environmental effects are minimal. In applications such as cementing, surfactants cannot migrate into the environment and, thus, have no bioavailability.

The possibility of environmental contamination has caused well operators and regulatory agencies to require fish toxicity and persistence data for products used in servicing wells. This data has been organized for nonionic, anionic, cationic and amphoteric surfactants. Nonionic surfactants are toxic to fish at concentrations below 10 mg/L to over 2500 mg/L depending on their chemical compositions. Anionic surfactants are toxic to fish at concentrations under 1 mg/L to several hundred mg/L depending on their chemical compositions. Cationic and amphoteric surfactants are generally toxic to fish at concentrations below 50 mg/L.

Overall efforts are aimed at low toxicity and high biodegradability with the least compromise in product efficiency. This requires the continual testing and environmental evaluation of surfactants summarized herein.
The Formation of Emulsions at Marine Oil Spills and the Implications for Response Strategies
Authors: Jenkins R. H. , Grigson S. J. W. , McDougall J.
Published: December 2007

This paper describes an empirical laboratory procedure to obtain information about the different tendencies of six North Sea crude oils to form stable and highly viscous water-in-oil emulsions. Very different behavioural patterns were observed between the oils tested and the implications of these differences on the appropriate choice of response strategies are discussed. In particular the effectiveness of dispersant application to the surface slick and the persistence of the slicks are considered in relationship to the different behaviour patterns observed.

No reliable correlations were evident between the behaviour of the crude oils and their pour points, asphaltene or wax contents. Hence the importance was highlighted in obtaining this sort of laboratory data to assist making decisions on the appropriate response strategies following an oil spill incident
Organisation of Psychosocial Disaster Management in an Exploration and Production Co.
Authors: Løvås E. L. , Leitao J. A.
Published: December 2007

In view of data indicating that adequate psychosocial disaster management (PDM) ensures optimal behavior in the crisis situation, increases the number of survivals and reduces the aftermath of trauma, too few companies have established a satisfactory psychosocial disaster organisation.

Following a review of the literature on psychosocial effects of disasters and psychosocial disaster manage-ment, several suggestions are made for improving disaster preparedness and response in a given company. An intra- and interorganisational model is proposed.
Compression Forces on Lumbar Vertebral Column During Drops With an 8-m-Long Freefall Lifeboat
Authors: Westerink J. , Tragter H. , Dekker G. , Rookmaaker D. P.
Published: December 2007

On behalf of and in cooperation with NAM, the University of Twente (UT) has carried out an investigation into the compression forces on the lumbar verte-bral column at the level L5-S1 during drops with a 8-metre long Free-Fall Lifeboat, used for the training of offshore personnel.

The following questions were posed: –What is the effect of two different seat positions at a drop height of 15.5 m:where a seat is reclined at 15° and facing the stern of the boat?where a seat is reclined at 75° and facing the bow of the boat?–What is the effect of different drop heights (5, 10, 15.5 and 20 m)?

In addition,it was requested that the permissibility of the calculated com-pression forces be estimated.

Using the 3-D computer man model TADAPS, approximate calculations have been made of the compression forces for the various situations.

From the results, it can be concluded that there is a substantially lower maximum compression force for the seat reclined at 75° than for that reclined at 15°.

Evaluating the results, using the NIOSH standard and a safety factor of 1.25 for the model approximation, the following conclusions can be made: –The seat reclined at 15° remains below the permissible limit at a drop height of 10 m;–The seat reclined at 75° remains below the permissible limit at a drop height of 15.5 m.

It is recommended that seats reclined at 75°, facing forwards, be used for the Free-Fall Lifeboat under investigation. Furthermore, the training drop height, based on the NIOSH standard, should be 15 m.

Higher 'drops' are only permissible, under emergency conditions.
Structure/Performance Relationships for Barium Sulfate and Strontium Sulfate Antiscalants
Authors: Miller James W. , O'Neill John J.
Published: December 2007

High performance gel permeation chromatography in combination with high temperature antiscalant testing has been used to establish structure/performance relationships for barium sulfate and strontium sulfate scale-control additives. Test results indicate that the best performing antiscalants share two important characteristics: (1) a high anionic charge density due to the presence of repeating succinic acid units in the polymer, and (2) a low weight-average molecular weight (850-2700): Of the 17 antiscalant candidates tested, polymaleic acid, polyitaconic acid, and a maleic acid/acrylic acid copolymer gave the best performance. High performance gel permeation test methodology and high temperature barium and strontium sulfate antiscalant tests are discussed. Structure/performance parallels are drawn between barium and strontium sulfate antiscalants and antiscalants for multi-stage flash evaporators.
Pressure Transient Data Acquisition and Analysis of Pumping Wells State of the Art
Authors: Da Prat G. , Pacheco E. , Sierra L.
Published: December 2007

In this work the advances in pressure transient data acquisition and analysis of pumping wells are presented. A brief summary is presented on methods used in the past 20 years for testing pumping wells. A comparison is made between pressure data acquired using bottom hole gauges and that based on indirect calculation of the bottom hole pressure by determining the liquid level in the annulus acoustically measuring the surface annulus pressure, and calculating the bottomhole transient pressure. The quality of the acquired data using the previously mentioned method is the main topic of discussion and its use and/or limitations for resevoir and well evaluation. Several field examples are used to ilustrate the presentedmethods. As a main result it is concluded that pressure data acquisition using acoustic methods is the best alternative for pumping wells. The pressure data resolution and accuracy is similar to a conventional amerada type of gauge. However the main advantage is that we can get the whole pressure transient profile (flowing/buildup) in real time if necessary. This definitely provides an enhanced data interpretation that can be used for resevoir evaluation specially for secondary recovery projects.
Ramos Field: Feasibility of Gas Cycling, An Integration of Geology and Engineering
Authors: Graue D. J. , Larsen W.
Published: December 2007

A study of the geology, the pressure data, and transient pressure tests from the Ramos Field in Northern Argentina suggest that the reserve of gas-in-place is probably 100× 109 standard cubic meters. However, the gas is probably not contained in the Santa Rosa sandstone formation from which it is produced. Rather it is probably contained in the shale zones which overlie and underlie this formation. The fracture system throughout the Santa Rosa sandstone is the conduit through which the gas is carried from the shales to the wells.

If this analysis is correct it means that any injected dry gas into the wells in the field will cycle very rapidly to the producers, because the pore volume of the fracture system is only a small fraction of the volume containing the gas. The available data indicate that the fracture system contains between .01 and .001 of the total gas indicated by a plot of P/Z versus the volume produced. The evidence is sufficient to caution the operator regarding the implementation of a dry gas cycling scheme which might be used to speed the recovery of the liquids contained in the gas condensate.
Oil Reservoir Sandstone Evaluation with Digital Backscattered Electron Images
Authors: Alvarado V. , Guzman J. , Kancev I.
Published: December 2007

Mineralogical and pore characterization has become an important key when evaluating oil reservoir quality. Presence of diagenetic or secondary mineral such as clays and cementing material can modify rock's texture, affecting in many cases the porosity and permeability during production and EOR processes.

Scanning electron microscopy (SEM) and other related techniques have been widely used in petroleum industry to study and characterize sedimentary rocks.

Backscattered electron (BSE) detectors and X-ray analysers are tools generally associated with SEM instruments, used by petrographers and petrophysicists who have taken a deeper concern with rock porous media (texture and mineralogy) through micrographies (analog signal) and its processing (digital signal). Relation between mineral composition and gray tone in the original signal, results on what could be called BSE imaging technique which shows some advantages over conventional techniques.

Core samples from Venezuela western region have been evaluated by BSEI. Micrographies from a SEM, working in the BSE mode were digitized and processed whith PDIFRAC software which was developed for this purpose.

Mineral and porosity fractions of the cores are presented for different depths. These results are compared with results obtained previously by XRD, IR and thin section petrography on the same samples.

Images are used to provide mineralogical composition, porosity maps, fractal dimention calculations and to visualize potential cases of formation damage by fines migration (kaolinite and pyrite fines)
Determination of True Resistivity (Rt) in Thin Beds Using Microresistivity Logs
Authors: Quintero L. F. , Ramirez M. O.
Published: December 2007

An algorithm for the determination of the true resistivity of thin beds (Rt) has been derived. The algorithm has been obtained using the deep resistivity curve and the microresistivity log. Numerical data modelling corroborate results. A smart computer program provides (with no need of programming skills) a user friendly interface.
X-Ray Tomography Application in Porous Media Evaluation
Authors: Angulo R. , Ortiz N.
Published: December 2007

With the development of a simple and more adequate macroscopic functional representation for the attenuation coefficient, more accurate quantitative and semiquantitative analysis can be made on X-ray tomography data. Numerical as well as visual information can be generated on the description of the phenomena occurring within the porous media. This work presents the results of analysis and numerical modeling of tomography data where a polynomial representation is used to estimate the attenuation coefficient. In addition, its application to the analysis of porous media and substances that are normally found in oil reservoirs is considered.

A polynomial representation is used for estimating the density and average atomic number of the substances occupying a volume element. These properties are also displayed for a better analysis of the system under consideration,
Characterization of an Oil Segregated Column, El Furrial Field
Authors: Alvarez R. , Marcano D.
Published: December 2007

The El Furrial field is located in Monaqas State, eastern Venezuela. It was discovered in February 1986 with the drillinq and completion of well FUL-1 in the sandstone of the Naricual formation, which resulted in an initial production of over 7200 bpd of oil with a gravity of 29 °API and a 1/2" choke.

The results of an intensive assessment plan led to the identification of reservoirs with average sand thicknesses of 1200 feet, original oil in place of over 4,000 MMBBL and a complex fluids system arising from a segregation process of asphaltic components. The crude's API gravity varies from 29 °API at the top of the structure to a layer of bitumen (8 °API) at its base, which prevents any natural water flooding process.

The purpose of this paper is to chemically and thermodynamically characterize the fluid column in the El Furrial field. The peculiar PVT behaviour of the column and the way in which its chemical and thermodynamic properties can be identified through the API gravity figures are described. The methodology used to identify the various zones of fluids in the field and to characterize a transition zone approximately 350 feet thick is also described.
Interpretation of Miscible Displacement Experiments Using Solutions in Laplace Space and Deconvolution
Authors: Portella Ricardo C. M. , Corrêa Antonio Cláudio F.
Published: December 2007

This paper presents a new methodology to interpret miscible displacement experiments. From the monitoring and analysis of effluent tracer concentration in laboratory cores it has been possible to determine the parameters which characterize the porous media and the displacement process.

Miscible displacement models of tracer transport in both homogeneous and heterogeneous porous media have been considered. The three-parameter models for heterogeneous porous media have been solved by numerically inverting solutions obtained in Laplace domain. The numerical inversion has been carried by Crump's algorithm, which yields solutions virtually free of numerical dispersion.

The methodology consists initially of the analysis of the effluent concentration data obtained from one-dimensional tracer injection experiments, by simple graphical methods. The results of the graphical interpretation are then used as initial estimates of the model parameters in an automated curve fitting process.

Application of graphical analysis is only possible in continuous (step) injection experiments. For experiments consisting of injection of a tracer slug, the effluent composition data are deconvolved. The deconvolution process yields the equivalent effluent composition data that would have been obtained from a continuous injection experiment, thus allowing the application of graphical analysis.

An experimental apparatus has been constructed and a series of experiments have been made. Experimental results have been analized with the new interpretation methodology.

The combination of graphical and automated curve fitting analysis has proved to be fast and reliable, and can be employed in on-line experiments.
Automation of Pressure Transient Test in Laboratory Using Deconvolution
Authors: Orellana Enrique Noel , Corrêa Antonio Cláudio F.
Published: December 2007

This work explores the application of automated pressure transient test analysis and deconvolution technique in laboratory scale.

To achieve this, a linear core which provides a pressure response corresponding to predetermined mathematical models, has been constructed.

The pressure response to applied boundary conditions has been monitored in real-time by means of an A/D converter installed in a microcomputer. Applying specific analysis techniques, permeability (k) and compressibility-porosity product (ϕ·ct) can be obtained from experimental data.

Data analysis includes: deconvolution of accumulated production and pressure responses, i.e. the desuperposition of a variable boundary condition;least squares non-linear estimation of system parameters. Greenstadt's modification of classical Newton's method has been selected to perform parameters optimization.

In order to be a reference to related future experiments, practical aspects and problems associated with the materialization of this experiment, specially those related with the interface between physical experiment and computer techniques, are extensively detailed in this work1.
A Brownian Method for Obtaining the Areal Continuous Distribution of Oil Reservoir Parameters
Authors: Martínez R.
Published: December 2007

A method for obtaining the continuous areal distribution of oil parameters (porosity, water saturation, etc.) of heterogenous oil reservoirs is presented. For its application it requires the previous knowledge of a set of discret values z(k,l). The theoretical fundamental assumption of the proposed method etablishes that all natural distributions can be considered as the superposition of each elementary brownian distribution, represented by its discret value z(k,l), whose physical model is the diffusion differential equation and its solution. This is a technique that allows the representation of brownian random distributions as a linear combination of each elementary diffusion function. For illustrating the operational aspect of brownian analysis, four examples are presented. The resultats are presented as digital images by means of image processing techniques. This method can be applied in mapping, two dimensions interpolation, numeric simulation and reserves calculation.
lmbibition as a Dispersion Process
Authors: Hernández J. Cruz , Rosales C. Pérez
Published: December 2007

In waterflooding operations in fractured reservoirs, imbibition is an important mechanism for expelling oil from the rock matrix. Therefore, a detail knowledge of imbibition processes is necessary for improving oil recovery. Here a theoretical-experimental work concerning this subject is described. In the theoretical part of the work, an analytical model is developed. This model is based on the assumption that imbibition can be visualized as a diffusion phenomenon. Some experiments carried out with Berea sandstone samples validate the model.
A Comparison of Deepwater Sand Control Practices in the Gulf of Mexico
Authors: Fahel R. A. , Brienen J. W.
Published: December 2007

Several published articles mention sand control problems in deep water Gulf of Mexico projects. ‘ In the Fall of 1990 Oryx Energy, while preparing for a deep water platform decision, conducted an in-depth study of deep water sand control techniques. At the time of the study, there were eleven platforms in water deeper than 700′ and they were operated by six companies. Each company permitted an interview with their engineers. This allowed us to trace the history of these platforms from conception through current operations, with special emphasis on sand control. This paper presents the specific techniques for wellbore preparation, perforating, stimulation, gravel packing, and completion hardware used by these six companies (companies only identified as A through F).
Sediment Alteration and Fines Migration in Enhanced Recovery Operations, Tertiary Heavy Oil Fields, California
Authors: Barrett M. L. , Mathias R. W.
Published: December 2007

California heavy-oil sands are very similar in alteration patterns during thermal recovery processes. Hot-water and steam reactions (up to 200°C) result in additional smectite and zeolite growth. These reactions alone do not predict the permeability decrease. As in sedimentary diagenesis, grain size allows a better understanding of permeability decreases and fines migration patterns. Finer-grained sediments have a greater order-of-magnitude permeability decrease to injected fluids as compared to coarser sediments. In-situ combustion reactions are much higher temperatures {500+ °C), but inter-well sediment alteration is limited to the matrix. This contrasts with samples from a combustion air injector, where both metamorphic fabrics and minerals were present.
Analysis of Gravel Packing Using 3-D Numerical Simulation
Authors: Nguyen P. D. , Fitzpatrick H. J. , Woodbridge G. A. , Reidenbach V. G.
Published: December 2007

Numerical simulators have proven to be viable tools for studying dynamic systems and providing accurate predictions. When combined with the advanced capability of modern computers, the flexibility of the numerical approach allows a wide array of variables to be investigated that otherwise would be limited by time, safety, or cost. Previous attempts at simulating gravel packing have yielded less than desirable results. This paper provides a comprehensive review of previous models and describes the mathematical development of a full scale, three-dimensional, gravel pack simulator.
Formation Damage Control During Underreaming and Gravel Packing in an Overpressured Reservoir
Authors: Blanton R. J.
Published: December 2007

Performing an underreamed gravel pack in a hot, overpressured reservoir is difficult. Underreaming fluid must be non-damaging, provide hole stability and cleaning, and generate a filter cake that can be removed. The gravel pack must be designed to minimize filter cake removal and gravel/formation sand intermixing. Successful underreamed gravel packs have been accomplished in normal pressure environments, but they have not been attempted in overpressured environments because of the associated difficulties.

This paper describes: 1) Displacement procedures used to clean the casing and protect the open hole, 2) Non-damaging underreaming fluid system which meets drilling and completion requirements, 3) Gravel pack design that minimizes gravel/formation sand intermixing, 4) Post gravel pack acid stimulation to remove the underreaming-fluid filter cake, 5) Gravel pack log, and 6) Well performance.
Hydraulic Fracturing of Soft Formations in The Gulf Coast
Authors: Ayoub J. A. , Kirksey J. M. , Malone B. P. , Norman W. D.
Published: December 2007

This paper discusses hydraulic fracturing treatments for unconsolidated sand reservoirs. The procedures needed for selecting the appropriate candidate wells, designing successful treatments, executing them and evaluating the results, are presented in a format directly usable by the practicing engineer. Field examples illustrate some of the key techniques.