bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Considerations for a New High Data Rate LWD Acoustic Telemetry System
Authors: Shah Vimal , Gardner Wallace , Johnson Don H. , Sinanovic Sinan
Published: December 2007

The first commercial acoustic telemetry system was successfully introduced in 2000 as part of a drill stem testing system. However, environmentally challenging LWD offshore applications and a need for higher throughput required a complete redesign of that system. Thus, the new system incorporates a new high power acoustic transmitter driven by an advanced signal processor that maximizes input energy into particular frequencies and therefore minimizes dispersion and distortion effects. Low-frequency acoustic attenuators were specifically designed to attenuate in-band noise entering the communication system. In addition, two other features were introduced as a part of the complete communication system. They were (1) an in-line wireless link to pickup, digitize, and transmit signals off the pipe while rotating and (2) a high data rate acquisition and telemetry processing system. The system is designed to work solo or in conjunction with a mud pulse telemetry system. This paper will discuss the system design considerations and the data rates associated with different modes of operation as well as results of initial field tests.
Obtaining Formation Water Chemistry Using a Mud Tracer and Formation Tester in a North Sea Subsea Field Development
Authors: Hodder M. H. , Magdy Samir , Holm G. , Segret G.
Published: December 2007

Precipitation from and corrosion by formation water co-produced with target hydrocarbons can cause serious problems, and an early knowledge of water chemistry is important for completion and facilities design. Owing to the high cost of interventions, this knowledge is particularly important in deepwater developments and subsea completions.

Samples of formation water are obtained by producing from the well completed in the water leg or sampling after water production occurs naturally. The former method carries significant cost and the latter method may delay the knowledge of the water chemistry.

Alternatively, a formation tester can be run into the wellbore to collect small samples directly from the formation.. In wells drilled with water-based mud, the results are generally mixed because successful collection of formation water requires that the tool be able to discriminate between the water and invaded filtrate. The method depends on the contrast in color or resistivity between formation water and water-based mud filtrate to determine when it is collecting water, and this contrast often doesn't exist.

This paper presents a new solution. A mud tracer was used to change the optical properties of the mud filtrate to make it detectable downhole. Laboratory experiments checked the compatibility of the tracer with gypsum or glycol mud system, sensitivity to high clay content, and ability to be detected with another tracer, and individually and in combination with a dark-colored filtrate. Shop experiments were carried out to establish a relationship between different tracer concentrations and optical properties at specific wavelengths. This relationship represents the basis of tracer detection and contamination prediction in real time downhole.

The first trial was carried in the Otter field in the northern North Sea. The field comprises three producers and two injectors with subsea completions. Downhole water samples were obtained during the logging phase on one of the injectors at an early stage of the field development. Sample quality and flushing time were optimized using the new technique. Sample analysis results compared well with later production tests.
Multiphase Flow Helico-Axial Turbine: Applications and Performance
Authors: Charron Yves , Pagnier Philippe , Marchetta Elise , Stihlé Sylvain
Published: December 2007

Following the installation in production fields of several tens of Two Phase Helico Axial Pumps, IFP and DBGP have recently launched a R&D program for the development of Two Phase Helico-Axial Turbines. These turbines may be used in many process applications in replacement of let down valves for energy recovery but also to increase the cooling duty or the liquid production. They may also be used in systems including a two phase separator with single phase expanders / turbines in view of reducing the number of equipment, space and weight. These turbines, suitable for all gas fractions, may find applications in the production of hydrocarbons (HP/HT wells, fractured reservoirs, oil stabilisation, electricity production in remote areas) but also in hydrocarbon treatment or in gas liquefaction. These applications cover a broad range in flow rate, pressure, temperature, gas fraction and fluid composition. A two phase helico-axial turbine prototype has been tested during the present year confirming the expected hydraulic performance. The hydraulic efficiency was found satisfactory to provide significant energy and liquid recoveries in many applications.
Toucan Smart Field Development: How to Generate More Value from Hydrocarbon Resources
Authors: Braithwaite S. R. , Müssig S. , van der Poel R. , van Putten S. , van de Waal W. , Kass M.
Published: December 2007

The Toucan Field is an oil rim situated in Gabon, discovered late 2001, operated by Shell Gabon. The joint venture partner is Amerada Hess Production Gabon. Experience from an adjacent field indicates that it is critical to manage the oil rim in such a way that reservoir energy is preserved whilst maximizing oil production. Due to the limited amount of information in this early stage of field development, there is high uncertainty in terms of reservoir properties. The smart technologies applied are directed towards reducing these uncertainties and mitigate down side risks of structural uncertainties.

Firstly a smart well completion is described which permits control of drawdown in long horizontal wells where total drawdown must be restricted owing to the proximity of water and gas. The completion instrumentation allows the flow control valve to be positioned using pressure rather than positional information. Based on simulation work, various strategies for well operation are discussed, along with their various merits; both in the context of the well, and the field.

Secondly the combination of frequent well tests, production optimization, and the use of reservoir surveillance tools is used to deliver an optimal solution to help the asset team analyze deviations from the expected reservoir performance. The business benefits of these smart technologies are discussed in the context of implementation in a medium sized oil rim.
Portfolio Analysis for a Bundle of Oil and Gas Projects
Authors: Al-Thani F. F. J.
Published: December 2007

Projects are now being procured or considered in bundles rather than on an individual, stand-alone basis. For the purpose of financial analysis, bundled projects can be considered as portfolios of projects. When projects are considered individually, some may be commercially viable as stand-alone projects and others may not. However, when projects are bundled together, an overall portfolio of projects may meet the promoters Minimum Acceptable Rate of Return (MARR) and be deemed commercially viable. This paper describes the mechanism and software used to assess a portfolio of small oil and gas projects, those being new projects and the refurbishment and operation of existing facilities. This paper describes how a non-commercially-viable batch of refurbished facilities can be financed with the help of cross collaterisation from the commercially viable batch of new projects when considered as a portfolio.
The First Real Zero Gas Flaring Project in the Middle East and Gulf Region
Authors: Wasfi Adel K.
Published: December 2007

The ADNOC group operating companies have over the last few years worked hard to progress towards the company's "Zero Flaring" aspiration. For the first time, within the ADNOC Group and GCC countries, a true Zero Flaring system is now in operation. The previous continuous Flow Suction Tank (FST) flare in one of ADCO's major fields is now completely switched off during normal operation.

This historic milestone resulted in 90% reduction of the Field's total daily process flaring (from about 2.8 MM scfd to 0.3 MM scfd).

On an annual basis the closing of this FST flare results in additional gas being made available to ADNOC, about 900 MMscf worth 1.4 MM$. The total combined value from environmental benefits and recovered gas is $22million over a 25 years period using Net Present Value calculations.

The challenges faced were the following: Recovery of flash gasElimination of gas blanketingElimination of hydrocarbon purge gasElimination of pilot gasHigh H2S gas content and related safety issues.

The implemented solution included: A vapor recovery system using an oil injected screw compressorA high integrity Quick Opening Valve (QOV) in the existing 30 inch flare header.A new high integrity continuous sparking ignition systemControl and monitoring system: –to guarantee quick opening of the QOV–Provide online status information of the QOV and the automatic ignition system.N2 generation package for the continuous purge of the flare header with automatic fuel gas purge as back-up.New flare tip to suit the new operating conditions.Ultrasonic flow meter to measure the gas being sent to flare.
Comprehensive Solutions to Drilling Waste Management
Authors: Al-Suwaidi Abdullah , Hun Christian , Marmash Fuad , Hendy Abdel Fatah
Published: December 2007

ADCO has always been seeking continual improvement to minimise the impact of its drilling operations on the environment and to conserve the desert for future generations. One of the main challenges is proper management of the fluids & solids generated by drilling oil & gas wells.

This paper presents the complete solutions adopted to handle the generated waste streams with the improvements in rigs design ("zero" discharge) and the execution of three recent plants: Reconditioning & recycling plant for drilling Oil-Based Mud (OBM).Indirect thermal desorption treatment plant for OBM drill cuttings with 100% recycling of recovered materials which are converted to usable products (i.e., diesel fuel, irrigation water and interlocking blocks).Two dedicated deep disposal wells for waste mud.

The outcome of the joint efforts of Drilling & HSE Divisions confirms that all hazardous wastes are being managed with true applications of 3R (Reduce, Reuse and Recycle) to maximise hydrocarbon recovery without noticeable impact on the environment.

The new waste management plants are centrally located in the major oil producing fields, thereby reducing hauling distance. These improvements translate in ADCO to minimum disposal and overall costs saving while ensuring compliance with or even exceeding, local environmental regulations.

Such global approach of this scale is a first in the Middle East Region and is setting a new benchmark of environmental standards for others to follow.
The Effect of Diffusion on the Saturation Pressure of Fractured Oil Reservoirs
Authors: Mohebbi A. , Rahimi A.
Published: December 2007

The role of diffusion in reducing the saturation pressure of oil in blocks located at different depths of fractured oil reservoirs has been studied. A model to describe unsteady state diffusion in a matrix block with a given geometry in fractured oil reservoirs has been developed and the results have been compared with the analytical solution. The delay time for solution gas drive due to diffusion in a block with a given shape has been calculated by using the data of Haft kel field.
Petrophysical Models and Techniques for Shaly-Sand Formation Evaluation
Authors: AlRuwaili Saleh B. , AlWaheed Hilal H.
Published: December 2007

Conventional petrophysical models, e.g. using neutron-density cross-plot for lithology and porosity and Archie's equation for water-saturation, can be adequate for evaluating clean sands, which have null or minimal shale and clay. Moreover, routine core analysis can be enough for validating log-analysis results in clean sands. On the other hand, shaly-sand formations have shale and clay present in them and the above standard petrophysical techniques are not adequate for the accurate evaluation of shaly-sand formations. Porosity logs, e.g. neutron, density and sonic, and saturation logs, e.g. deep-resistivity, are affected by clay presence in shaly sands. Such effects need to be modeled and incorporated in the log analysis in order to obtain more accurate formation evaluation of shaly sands.

Some of the hydrocarbon-bearing formations in Saudi Arabia have shaly sands. Soft and hard data was acquired to help evaluate and describe the storage and flow capacities of these formations for optimal production developments. Density, neutron, sonic, resistivity and gamma-ray logs were routinely acquired in wells drilled in these formations. Logs like Elemental-Capture-Spectroscopy (ECS) and Nuclear-Magnetic-Resonance (NMR) were acquired in key wells. In these shaly formations, some wells were cored and core analyses were conducted to obtain formation porosity, electrical properties and clay attributes like clay-type and clay-abundance. The above soft and hard data acquired has helped in developing and applying more reliable petrophysical models and techniques in shaly sands formation evaluation.

This paper will present and discuss methods and modeling techniques for evaluating shaly sands. Applications of these techniques in some shaly formations in Saudi Arabia are included in this paper.
Integration of Impedance Inversion Results into the IRAP 3D Geomodel
Authors: Al Mehairi Y. , Al Khowaildi S , Al-Shaikh Ahmed , Chenot D. , Pizza J. L. , Prat P. , Lalande S. , Barens L. , Hegre J. A.
Published: December 2007

This paper describes the final part of a joint integrated seismic characterization project on a major carbonate reservoir of an onshore field, in the Middle East. The reservoir geomodel building captures well information, the 3D structural and seismic information obtained through seismic interpretation and impedance inversion.

The aim of this seismic characterization project was to improve the reservoir management by optimizing well placement, geosteering and geomodeling. These goals imply to derive the lateral and vertical heterogeneities in the reservoir and to characterize the reservoir porosity variations including the location and volume of some non-reservoir ‘dense’ bodies embedded in it.

Stochastic inversion was carried out with in house software Geolnv™ The stochastic approach enables us to compute a family of equiprobable impedance inversion volumes that are both constrained by seismic and well data. For this inversion, a family of 100 realizations was computed using 22 input wells and a mean wavelet that extracted on 6 high quality wells. Each inversion contained 785 000 traces.
Contribution to the valuation of Microseismic monitoring data recorded from treatment well – Results based on 20 hydro-fracturing jobs recorded from treatment well
Authors: Kaiser P. , Fortier E. , Gaucher E. , Maisons C.
Published: December 2007

To stimulate their oil recovery, oil companies carry out hydraulic fracturing jobs. In this aim the characterization of the fracture, as fluid path, is crucial. It is no longer necessary to prove that the microiseismic monitoring of hydro-fracturing experiments can be used for fracture mapping. Nevertheless, monitoring from treatment well is still a challenge. Using the field experience gained over 20 jobs, we present here a review, as objective as possible, on microseismic monitoring performed during fracturing operations from the injection well (treatment well). Over these last five years, we managed to collect a significant database/catalogue of frac jobs monitoring results, yielding us to keep learning, step by step. Various configurations of the tools in the reservoirs and various probes were experienced. The stimulation jobs were carried out in different types of overburdens, and various behaviours of the formations have been observed. The reservoir behaviour lead to fracture mapping and characterization in successfull cases; however, unconsistent acoustic response was also detected. This is all this feedback we now present here, keeping in mind that these assessments are to be seen just as a starting point within an ongoing learning process.
Can Cement Log be Better Managed and Analyzed
Authors: Talabani Soran
Published: December 2007

Whether cement exists behind casing or not is easily identified by the current generations of cement evaluation tools. However, there are few important questions to be seriously taken into account once analyzing cement log for zonal isolation; is the cement attached to the casing? Does the cement isolate different beds and zones? Does any micro or macro annulus exist over intervals of interest? And if so, does it affect on the well future. Is the cement attached to the formation preventing micro or macro fractures? Does capillary have any effect on the cement integrity? How the width of this micro-crack be measured. And the last, do gas and other fluid seep through the micro-channel.

Looking at cement log might be easy, though not the analysis. Analysis of the cement bond tool data is very crucial for forthcoming decisions on a well. Therefore, it is important to identify cement quality. Some micro-channels might behave as a barrier to prevent any fluid movement, while other good cement body might create cracks soon after the well is set on production. There are some identical cement jobs that results in very different isolation results! So, why this happens? All these have answers once cement log is quantified and later analyzed.

In this paper, case histories are addressed in both, poor and fair cement jobs behind casing. In the field examples, the effect of tool centralization on the log quality, the means and ways of identifying micro and macro channels, and possible remedy based on correct cement log evaluation and analysis are addressed.
Interpretation of Multiple Hydraulically Fractured Horizontal Wells
Authors: Zerzar A. , Tiab D. , Bettam Y.
Published: December 2007

Horizontal wells are ideal in tight reservoirs where economic production cannot be achieved by conventional vertical wells. One of the advantages of a horizontal well over a vertical well is that it can be fractured at a number of positions along its horizontal section. Tight reservoirs generally produce in transient state for a considerable part of their producing life. Therefore accurate transient inflow models are required, not just for well testing purposes, but also for production forecasting. The objective of this study is to determine the number and characteristics of the producing fractures along the horizontal segment of the well.

A new analytical model is developed to describe the transient pressure response of a horizontal well intersected by several fractures in anisotropic reservoirs. The fractures along the horizontal wells are assumed to be rectangular and vertical, and either transversal or longitudinal relative to the well direction. They are also of finite conductivity, infinite conductivity, or uniform flux type. It is further assumed that the fractures are fully penetrating (2D Model) or partially penetrating (3D Model), the well is either open or perforated only at fractures.

A new set of type curves are developed that include five flow regimes: Bilinear, Linear, Radial, Biradial, and Pseudoradial. New equations have been developed describing the unique characteristics of the five flow regimes. These equations allow us to calculate: the number of active fractures, equivalent fracture conductivity and total system conductivity, equivalent half-fracture length, reservoir directional permeabilities, equivalent skin, and the total skin of the system without using type-curve matching. A step-by-step procedure is provided for calculating reservoir parameters of a multiple hydraulically fractured horizontal well and practical applications are carried out by solving some simulated examples.
Vertical Conformance in a Mature Carbonate CO2 Flood: Salt Creek Field Unit, Texas
Authors: Bishop Deborah L. , Williams Mike E. , Gardner Stephen E. , Smith David P. , Cochrane Tom D.
Published: December 2007

Salt Creek Field Unit is one of many mature carbonate reservoirs first waterflooded then CO2 flooded in the Permian Basin. The reservoir consists of multiple layers of porous, grain-dominated shoals with varying permeability and porosity, separated by non-porous layers of varying thickness. The different properties of the layers result in different processing rates and times. As CO2 floods mature and production declines, operators are challenged to maintain efficiency. At Salt Creek this is accomplished by tracking the maturity of each zone, calculating the contributions of each, and modifying the completions to optimize oil production and profitability.

Salt Creek Field Unit was discovered in 1950 and water injection began in 1953. The waterflood was modified several times and by the early 1990's, the field was developed on 20-acre spacing with five-spot patterns. In 1993, a CO2 WAG (Water Alternating Gas) flood was implemented, whereby water is injected alternating with gas (CO2). Consistently optimized reservoir management practices including geologic modeling, zonal injectant tracking, and 3-D seismic have added great value to the field and have created an environment where flood optimization efforts continue to be profitable.

One of the key processes enabled by effective reservoir management is the ability to identify mature (swept) layers and identify workover candidates. First, injection data is allocated based on interpretation of injection profile logs and stored in a database that calculates zonal maturity as a fraction of hydrocarbon pore volume injected. A type curve relating CO2 injection to incremental oil recovery is calibrated to match current pattern production. Post-workover production is then predicted based on the recovery curve applied to the remaining targeted intervals. The resulting production is adjusted for incremental CO2 injection enabled by the workover, changes in producing bottomhole pressure, and gas plant capacity limitations. Where economics are favorable, recommendations are made to modify the wellbore's profile with plugs, cement squeezes, straddle packers, or, where casing is particularly poor, with liners. The result is a more effective use of a valuable injectant and a more profitable lease.
Occupational Health Conditions Improvement Replace Carcinogenic Oxygen Scavenger with an Alternate Safer Product
Authors: Hassan M. A. , Vasagam Manicka , Pandav Prafull S.
Published: December 2007

LNG production units located in Das Island have four (Boiler Nos. 1 to 4) high pressure/high capacity Boilers for steam generation (which supplies steam to LNG Trains 1&2). Each of the four massive Boilers have separate De-aeration unit, where the major portion of dissolved gases (mainly oxygen and carbon dioxide) present in the feed water are removed by scrubbing with steam. Followed by De-aeration, to get rid of the remaining oxygen present in the feed water, an oxygen scavenger is injected downstream of De-aerator. This product chemically scavenges the remaining dissolved oxygen by reaction. The oxygen present in the feed water is the chief culprit for boiler steam system corrosion and would cause accelerated oxygen pitting, especially at elevated temperatures. The oxygen scavenger quietly does its job and keeps up the boiler life; hence the use of this product is very vital in any boiler operation.

During all these years of operation, "hydrazine" was employed as the oxygen scavenger and found to be meeting the operational requirement. But continuing this product became an important issue, because it has been widely claimed as a carcinogen and toxic.

The issue started gaining importance as it directly concerned with "Health Effect". The necessity to evaluate a safer alternative turned out as a challenging task for ADGAS, because on one hand the proven product needed replacement due to the health hazard and on the other hand the Boiler performance/integrity had to be ensured.

The task was handled successfully; a better alternative oxygen scavenger was chosen (DEHA, Diethyl Hydroxyl amine) after detailed evaluation and is in satisfactory service since July 2002 in Boiler 1 to 4. Based on the experience from Boilers 1 to 4, ADGAS have very recently switched over to use of this safer alternative (DEHA) also in the remaining Boilers 5&6 also, which supply steam to Train-3.

The successful approach has helped ADGAS to contribute for the Occupational Health improvement to the working environment and thereby enhance its HSE STANDARDS. Through this paper ADGAS shares their experience in this regard.
Combination of Dual-Energy Gamma Ray/Venturi Multiphase Flowmeter and Phase Splitter for Application in Very High Gas Volume Fraction Environment
Authors: Delvaux E. , Germond B. , Jha N. K.
Published: December 2007

In mature fields, operators are confronted with wells producing high water cut at low pressure with consequently very high gas volume fraction (GVF). Under these conditions, the net oil flow rate is low and therefore, permanent or periodic testing becomes critical to determine profitability and manage the field production.

To optimize and monitor the oil production under these conditions, operators are looking to utilize multiphase flowmetering technologies. Accuracies achievable by inline multiphase flowmeters have greatly improved in recent years, but liquid and water-cut measurement accuracies decrease when the GVF is very high.

At low pressure to reduce the GVF, it is necessary to separate a large portion of the gas upstream of the multiphase flowmeter, thus enabling optimum measurement of the liquid and water cut under lower-GVF conditions.

Market drivers generally dictated by operator requirements have resulted in the formation of an project team with specific Middle East focus to deliver an operational prototype for a production well testing campaign on a fast track basis. The package comprises a partial separation unit and a dual-energy gamma ray/Venturi meter.

The selection of a partial separation design was based on a review of the commercially available solutions capable of handling the large operating range required for use in periodic well testing applications in terms of flow rates and pressure rating. The design comprises gas liquid cylindrical cyclone with tangential inlet. The capacity of each device to ensure a dry gas phase with minimum pressure loss over the complete required operating range was critical in the selection process.

This paper presents test results validating that a gas liquid cylindrical cyclone located upstream of a dual-energy gamma ray/Venturi meter is an effective partial separation system. With an inlet GVF of 99% and 90% of the inlet gas extracted by the partial separation system, the GVF at the multiphase flowmeter condition is below 90%, and accurate measurement of the 3 phases is achieved.
Salvage of Casing Leak Wells on Artificial Lift in a Mature Oil Field
Authors: Sivakumar V. C. Babu , Janahi Isa Ali
Published: December 2007

The Bahrain oilfield, discovered in 1932, is one of the most mature fields still under active exploitation in the Arabian Gulf. Around 750 wells have been drilled in the field and it is worth mentioning that even today the discovery well in the field is also under active service as a gas injector after several salvages.

Over the years starting from the discovery year the well design has evolved from the initial 6 casing string completions to the present simplified 2 casing string completions for the 12 vertically stacked Bahrain Zones from the Mishrifs occurring at 1600 ft. to the Kharaib zone occurring at depths of around 3200 ft. The prevalence of a very highly permeable shallow aquifer has made it very difficult to obtain effective isolation by cementing of the surface casing to surface. In addition, the high salinity and corrosivity of the water in this aquifer has lead to casing leaks is several earlier generation wells. This has in a few cases lead to underground blow outs from the high pressure producing zones into the aquifer and in some instance even surface gas seepages.

In this paper, we shall be presenting an update of the history of casing leak occurrences in the field and the various innovative methods adopted to abandon self flowing high pressure zones and then salvage these wells in low pressure non-self flowing zones. The low pressure zones are completed on artificial lift either on pump or gas lift after isolating the leak zone with a concentric string and packers as necessary. In a way, it can also be said that, these salvaged wells have enabled us to test, evaluate and produce the otherwise economically unviable low pressure, low productivity zones.

To summarize the paper will dwell on the reasons for casing leak occurrence, evolution of the well design to minimize casing leak and optimize well costs, abandonment of high pressure self flowing zones in the casing leak wells and finally the re completion of these wells on artificial lift in non self flowing low pressure zones.
High Resolution Probes Provide Real Time Data for Corrosion Inhibitor Field Trial Test Evaluation
Authors: Elkordi Ali
Published: December 2007

The conventional ER (electrical resistance) probes have a suitable response time in systems with high or severe corrosion rates as defined by NACE Recommended Practice (> 5 mpy).

In low-corrosion environments (< 1 mpy), their response time may become incompatible with the day-to-day management of corrosion. For inhibited systems, where it is now common to expect the residual corrosion rate to be in the low range (for oil and gas lines) or in the medium range (for water injection lines), alternative techniques are required for the surveillance of the critical lines and for the optimization of inhibitor dosage.

A new generation of high-resolution (HR) corrosion monitoring has been introduced in the last 5 years, aimed at improving the response time of the on-line corrosion monitors.

A program was initiated in order to determine the real-time response of the HR probes against changes of inhibitor concentrations at different predetermined time intervals. The trial was performed on 24" transmission line carrying stabilized crude with 0.01% water cut.

This paper presents the real time response of the various probes at different inhibitor concentrations and analyzes the suitability of the techniques in terms of sensitivity, noise and repeatability, in order to be utilized for the forthcoming corrosion inhibitor (CI) field trial test. It also discusses the preliminary results of the actual field trial tests in terms of the aforementioned probes characteristics.
An Analytical Model of Temperature and Stress Fields During Cold Water Injection into an Oil Reservoir
Authors: Kocabas I.
Published: December 2007

A new transient analytical model has been developed to study the temperature and stress distribution induced by a non-isothermal fluid injection, particularly conventional waterflooding. In the model, the transient pressure, temperature and stress fields are computed consecutively. The pressure field has been computed by using the exponential integral solution. The transient temperature field has been computed by using a model that can account for both the overburden heat losses and transversal heat dispersion within the reservoir. The stress distribution has been calculated by a method presented for a plane strain in a hollow cylinder

The results implied that the thermoelastic changes in the cooled zone could affect the surrounding stress fields in a profound manner. For instance for a porous medium with stiff material such as carbonate reservoirs owing to cooling by the injected cold water large scale tensile stresses arise and may induce new fractures or propagates existing ones far into the reservoir. In addition, a major tangential stress concentration develops just in front of the cooled zone and hence shear yield is highly likely to occur ahead of the thermal front.

The two dimensional treatment of the temperature field makes the new method superior to the previous analytical models where only one dimensional field has been employed.
Near Wellbore Stimulation by Acoustic Waves
Authors: van der Bas Fred , de Rouffignac Eric , Zuiderwijk Pedro , van Batenburg Diederik
Published: December 2007

Near-wellbore formation damage reduces the productivity in most of the existing oil and gas wells. The formation damage is caused by the invasion of fluids during the drilling and completion process and in a later stage by the deposition of particles (fines, scale, asphalthenes, etc) due to production. The conventional technique to remove these types of damage is injection of fluids to dissolve the damage. The treatments typically involve pumping of chemicals (acid, corrosion inhibitor etc.) under matrix conditions. Controlled placement of the treatment fluids in the zones that need to be treated is difficult and sometimes impossible in particular in long, horizontal intervals.

A promising new technique to remove the near-wellbore damage is high-frequency acoustic stimulation; a specially designed acoustic tool is utilized on wireline or coiled tubing to selectively treat the required reservoir intervals. The preferred application of this tool is at underbalance pressure condition: damage particles mobilized by the acoustic waves are removed from the reservoir interval by the production flow. The paper reports on the ongoing acoustic stimulation research.

Laboratory work showing the potential of acoustic cleaning has been previously reported; it was performed on sandstone cores saturated with brine in a laboratory set-up using linear acoustic waves. Recent acoustic cleaning experiments examined the effect of various other conditions i.e. oil saturated rock and gravel pack completion. Results from these experiments are presented here.
Improvements in Downhole Equipment for Fluid Injection and Hydraulic Fracturing Monitoring using Associated Induced Seismicity
Authors: Deflandre J.-P. , Vidal-Gilbert S. , Wittrisch C.
Published: December 2007

In the last 10 years the use of passive seismic monitoring has been improved with the development of downhole equipment such as permanent downhole 3C-geophones and downhole telemetry. Simultaneously, surface equipment were improved, 20 and 24-bits system occurred with advanced integrated acquisition software. In these conditions, the ratio of the relevant information (microseisms) to the total amount of recorded files increase from less than 5% to more than 90%. Consequently, processing time decreased significantly and real-time interpretation became possible. These improvements directly benefit to both long term and short term applications of microseismic monitoring.

The paper refers on the principle of passive seismic monitoring, describes the new development possibilities and the way this domain is evolving. Feedback on field experiences are given to optimise data acquisition and interpretation.
Vertical Miscible Displacement of Oil from Fractured Reservoir
Authors: Jamshidnezhad Mohammad
Published: December 2007

This paper discusses the problem of the displacement of oil, saturating the fractured reservoir, by another fluid miscible with it in all ratios, in a gravity field. The equations are derived with allowance for all three mechanisms of mass transfer between fracture and matrix. Utilizing the method of characteristics provides the analytical solutions of the resulting system of equations. The results have been compared with experimental results. There is a very good agreement between the results and experiments.
Determination of Recovery and Relative Permeability for Gas Condensate Reservoirs
Authors: Al-Honi Mohamed , Zekri Abdulrazag Y.
Published: December 2007

Coreflood experiments on gas condensate flow behavior were conducted for a Libyan gas condensate reservoir. The objectives were to investigate the effects of rock and fluid characteristics on critical condensate saturation (CCS), gas and condensate relative permeability's, hydrocarbon recovery and trapping by water injection, and incremental recovery by subsequent blowdown and vaporization by dry gas injection.

The water/gas relative permeability data were generated using implicit historical matching simulator which uses a reverse history matching technique to generate a full suite of relative permeability curves over the range of interest. The results of the tests on the reduction in gas permeability due to retrograde condensate accumulation demonstrated that, in general, the effective permeability to gas decreased significantly at pressures below the dew point pressure due to the condensate trapping effect for all the stacks investigated in this study. Permeability continues to drop at very low pressures even though theoretically condensate should be re-vaporizing. The recoveries of the liquid condensate during the vaporization by dry gas injection at pressures below the dew point pressure were generally high. The recovery ranged from 66% to 70% for the high permeability core stack and 86% to 98% for the lower permeability core stack. In theory, it is possible for all of the condensate to be revaporized into the methane gas stream. However, in practice, the recovery is usually less than 100% due to macroscopic sweep efficiency limitations and mass transfer limitations within the rock matrix.

Poor mobility ratio and viscous fingering during the methane injection characterize the re-vaporization of gas condensate by methane gas. This results in early breakthrough of the methane gas and very high gas/liquid ratios during the test. The volume of methane gas injection required to recover a significant amount of the condensate liquid in the core is a function of temperature, pressure, composition of the gas, heterogeneity and especially the permeability of the core sample.
Laboratory Investigation of CO2 Flooding
Authors: Yongmao Hao , Zenggui Wu , Binshan Ju , Yueming Chen , Xiangjie Luo , Petro Xinjiang
Published: December 2007

Carbon dioxide(CO2) flooding is an efficacious method of EOR and it is a very complicated process, involving phase behavior. To master the performance of CO2 flooding and provide accurate data for designing oil development, a comprehensive investigation of CO2 flooding phase behavior and mechanism based on laboratory study was conducted. In order to get representative fluid samples of a reservoir, it was necessary that the right operation of mixing the separator oil and gas samples to match the bubble point pressure be carried out. The result from PVT experiments shows that for a certain reservoir, through a slight manipulation of the measured PVT properties including bubble point pressure, volume factor, swelling factor, solubility of CO2 and viscosity, it is possible to obtain regression curves, which can be used to estimated the PVT behavior for any hydrocarbon fluid-CO2 mixture of this reservoir. The result of slim tubule tests indicates that it is more appropriate to determine the minimum miscibility pressure of the reservoir fluid-CO2 mixture by the position of inflexion on the curve of oil recovery with flooding pressure than by reaching a special oil recovery point.
Thin Sand Development Made Possible through Enhanced Geosteering and Reservoir Planning with While-drilling Resistivity and NMR Logs: Example from Niger Delta
Authors: Oguntona J. A. , Kelsch K. , Osman K. , Ingebrigtsen E. , Butt P. , Saha S.
Published: December 2007

The horizontal well placement within a thin sand with structural dip and economically produce these reserves are a challenge for the oil industry. New Reservoir Management and Formation Evaluation techniques are making these very thin hydrocarbon sands accessible and economic for development. Upfront planning by multi functional team to define well placement, uncertainty management and tool selection are key. Next execution of landing and lateral require maximum flexibility and accuracy from tools and team.

In this paper, two case studies are presented where Logging-While-Drilling (LWD) resistivity and Nuclear Magnetic Resonance (NMR) were utilized to geosteer a horizontal section through a thin sand and to geo-stop the horizontal well after drilling an optimal drain hole length.

Resistivity and NMR-LWD provides critical formation evaluation information such as resistivity at bit, up and down resistivities, structural dip, formation porosity, bound-fluid volume, free-fluid volume and permeability. Obtaining this information while drilling has a significant impact on drilling and completion decisions in Niger Delta.

In the first case study, based on the information of NMR LWD from a pilot hole, a horizontal sidetrack was optimised in the high permeable section of the thin reservoir. In addition, NMR logs demonstrate the horizontal section was placed generally within the sweet spot of high free fluid section.

Drawing experience from the first case study, a more difficult situation of drilling a horizontal well with a six feet window was addressed. The objective was to place the well within the sand and drill an optimal length that will meet hydrocarbon deliverability. First, resistivity at bit was used to restrict the well within the target sand. Within this heterogeneous sand, the while-drilling resistivity image and up and down deep Resistivity measurements allowed the geosteering team to stay in the "sweet spot" of the reservoir. Concurrently, permeability was estimated from the NMR log. Based on this permeability, hydrocarbon producibility was computed and decision was reached to drill the optimal length. This novel approach combining geosteering techniques using flexibly LWD tools are key to future development of thin hydrocarbon reservoirs.
A Statistical Approach to Reservoir Zonation
Authors: Agunwoke Godwin O. , Egbele Emmanuel , Onyekonwu Michael
Published: December 2007

Reservoir flow zones reflects group of rocks that have similar geologic, physical properties and depositional environment that affect fluid flow. Variations in rock properties result from depositional, diagenetic and post-depositional changes. Aside from a geologic approach, statistical analyses are required to verify the existence of these flow zones.

A statistical zonation technique developed by Testerman1 to identify and describe naturally occurring zones in a reservoir and to correlate these zones from well to well was used here. The flow performance is a strong function of the average permeability, and therefore of the statistical flow unit definition method used.

Five reservoir flow zones were established based on the geologic litho-stratigraphic correlation using gamma ray and resistivity logs. This is against the two flow zones estimated from statistical correlation. Where this happens, the simulator may lump together several geologic layers. Lumping involve adding layers that have similar physical properties. The number of zones depends on the computing limitation and any other constraints of the simulator. Reconciling these two differences provides a better input into numerical flow simulation.
Congenital Reservoir Rock Characterization of Weak Hydraulic Properties
Authors: Chike Ikechukwu , Egbele Emmanuel , Onyekonwu Mike
Published: December 2007

Weak hydraulic units occur frequently in many Niger Delta fields. This makes the characterization of reservoirs in such fields quite challenging.

In this work the interpretation procedure, adopted model and algorithm were chosen such that each unit is treated separately to make the evaluation process as detailed as possible. Also, a conscious effort was made to incorporate functions in our adopted model that take care of the factors responsible for the weak hydraulic units in the reservoir.

The application of cut-offs was done in a manner that blocked properties and predictive algorithm only relate to intervals that will contribute to production. This approach is necessary to improve the precision and predictive algorithm of porosity, permeability and water saturation that form part of the reservoir evaluation process. Usually the inclusion of units with weak hydraulic properties in the evaluation of hydraulic storage at the onset will decrease and weaken the precision of the evaluation process if cut-off were not applied. Also, the approach resulted to a construction of the simplest dynamic model that is compatible with the static model which is the objective of every reservoir characterization.

The prime aim of this approach is a more precise reservoir characterization as against a mere approximate.
The First Coiled Tubing Deployed ESP in the Gulf of Mexico
Authors: Keck Richard G. , Robertson S. W. , Butler D. J. , Bumbaugh D. B.
Published: December 2007

In February 2003 BP installed the first coiled-tubing deployed electric submersible pump in the Gulf of Mexico. The Grand Isle 40 F-1 well had been producing for several years with 27/8" jointed tubing, and the two previous electric submersible pumps lasted 16 and 30 months. Once the ESP failed, the well was produced at a much lower rate using gas lift for another 11 months or more until the ESP replacement could be scheduled and executed. The project discussed in this paper utilized a rig to replace the entire 9,700’ of production tubing with a 2-3/8" coil string that had the ESP at the bottom. The benefits of this deployment method include a reduction in the down time between pump change outs and a reduction in project cost. When the ESP fails, a liftboat and coiled tubing unit can be mobilized sooner, and at a lower cost, than a rig. The added cost of this first coil installation will pay out with the first rig-less pump replacement.

The goals of the paper are to document this successful case study and to illustrate the value that CT-ESP has in the Gulf of Mexico offshore operating environment. We start with a history of CT-ESP's installed elsewhere, and then discuss our well and why it was a candidate for a coil-deployed ESP. We then discuss our rationale for running the 2-3/8" diameter coil instead of other available sizes, and why we decided to run the cable external to the production string. Pre-job planning, regulatory issues, HS&E and equipment testing will also be addressed. Additionally, key elements of the operation, and the procedure to terminate and test the coil while running in the hole are presented. The conclusion will detail some of the lessons learned during the operation and the overall project economics.
Coiled Tubing and Wireline Intervention for Well Abandonment
Authors: Kirby S. , Skelly G. , Gordon D. , Sheed S.
Published: December 2007

This paper discusses the systematic approach adopted by BP Exploration to achieve its goal of safely abandoning the wells on a major North Sea platform. Having determined the abandonment methodology, an integrated team, comprising oil company engineers and key service company personnel developed processes and procedures to reach the objective. These included advances in coiled tubing rig-up procedures and the use of Technical Limit to capture learning. This approach facilitated the timely and cost effective abandonment of 24 wells in a safe and environmentally friendly manner and in achieving world-class performance.