bluuebunny/crossref_metadata_2025 huggingface dataset:
A Unique Wireline Re-Entry System for Seafloor Wells at Kepiting Field, Indonesia
Authors: Kadi I. , Wybro P. G. , Rodriguez F. H.
Published: December 2007

This paper presents the work performed by Conoco Indonesia Inc. in developing and testing a unique re-entry system for wireline work on two seafloor wells in 295 feet of water at Kepiting Field in the Natuna Sea of Indonesia. This system does not require the use of a floating drillship for conventional wireline work in a seafloor well.

The main components are:

A 240 foot buoyantly tensioned steel seafloor riser A surface buoy which connects temporarily to the seafloor riser and also supports an above water work platform for the wireline lubricator assembly A set of strategically located permanent workboat moorings A workboat arranged to serve as the wireline unit's operating platform and to provide all support services.

This paper discusses the components, installation and performance of this unique wireline re-entry system.
Effects of Perforation Flow Geometry on Evaluation of Perforation Flow Efficiency
Authors: Liu Z. , Peden J.
Published: December 2007

This paper presents a study on effects of perforation flow geometry on the evaluation of the flow performance of perforations. From data obtained in the laboratory serious deficiency and poor accuracy were identified in exploring the linear perforation targets recommended by API RP 43 Section II for the evaluation of the flow performance of perforations. This discredits the validity of the procedure and poses doubt to the correctness of applying API RP 43 results to the downhole conditions. The work suggested that perforations with radial flow configuration should be utilised in such an evaluation.
The Challenge of Thin Oil Development: A Case Study
Authors: Prasser R. S.
Published: December 2007

The Snapper field, which is located in Bass Strait, offshore south-eastern Australia, contains a large gas reservoir, the "N-1", with an 8 metre "pancake" oil leg. While Snapper was developed primarily as a gas field, initial work has concentrated on maximizing oil recovery prior to eventual large scale gas production. Phase I development was undertaken during 1981-1983 with fourteen N-1 oil completions coming on-stream. Encouraged by the successful performance of these wells, a second drilling phase was undertaken during 1986-87, resulting in nine new oil completions.

Some gas production has been required to meet gas market demand. This production, from gas completions and-gas coning in oil wells, has caused the oil zone to steadily rise. Over the next few years, workovers in many of the wells will extend production as the column continues to rise.

This paper examines the highly variable performance of the mature Phase I wells and the early performance of the Phase II wells. This will assist other operators in planning similar, thin oil developments.
Fire Protection System Upgrade
Authors: Soo C. S.
Published: December 2007

EXXON has implemented new specifications for the Fire Protection System on Its offshore platforms. This paper will, discuss the evaluation of these specifications and also describe how EPMI retrofitted its existing twenty facilities to meet these guidelines so as to achieve the most effective use of money spent.
Handling of Liquid Holdup in Duyong Two-Phase Flow Pipeline System
Authors: Saad M. R. , Singh B.
Published: December 2007

The paper deals with the handling of liquids in the multi-phase flow pipeline system within Carigali's Duyong Offshore Gas Complex and the Onshore Gas Terminal, in Kerteh, Terengganu. The data and operations experience gathered necessitate changes to the operating procedures originally identified during the design phase. This is to ensure more efficient handling of liquid hold-up in the pipeline during low gas flowrates.
The Study on Phase Behaviour of the Flowing Fluid in Tubing and its Application
Authors: Wang S. H. , Wu C. I.
Published: December 2007

In order to minimize the tubing corrosion during production in a gas well, it is necessary to determine the factors such as wettability of tubing and critical erosional velocity etc. for the design of tubing corrosion prevention. The purpose of this work is to study the phase behavior of the production fluid in a production tubing in connection with the flowing velocity and wettability of tubing. Data from a CO2-rich offshore gas well of Taiwan are analyzed by a procedure developed in this study. It is shown by our calculation that the tubing in the well should not be corroded seriously during production because the tubing inner wall is oil-wet and the flowing velocities are much less than the critical erosional velocities.
Using Short-Term Pressure Buildup Tests for Reserves Estimation in Tight Gas Reservoirs
Authors: Sullivan S. A. , Poston S. W. , Piper L. D.
Published: December 2007

Average reservoir pressure must be known when material balance equations are used to determine gas in place. Most pressure data available for material balance analysis comes from single point tests (static bottom hole pressure tests). Unless the reservoir has been shut-in long enough for the pressure in the reservoir to stabilize there is no direct means of determining the average reservoir pressure.

A method has been developed to estimate gas in place in volumetric gas reservoirs using transient pressure data. The method is similar to the isochronal flow test. Pressure data recorded at a specific shut-in interval is collected during a portion of the producing life of the reservoir. A p/z plot is constructed using this pressure data and the corresponding production data. The p/z curve will plot as a straight line with a slope similar to the stabilized p/z curve. However, this nonstabilized p/z curve will be shifted slightly downward from the stabilized p/z curve. Gas in place can be estimated by drawing a line parallel to the nonstabilized p/z curve through a point on the stabilized p/z curve, such as pi/zi. This new line is extrapolated to the point of intersection on the (Gp) x-axis.

This analysis procedure was tested with production data simulated for a single well reservoir model with and without wellbore storage distortion. The procedure was also tested with production data simulated for a hydraulically fractured well model. The results indicate this method can be used to estimate gas in place within a margin of error acceptable for most engineering purposes.
Gas Production Outlook and Technological Progress: European Problematics and Answers
Authors: Valentin E. P. , Valais M. R. , Champion D. J.
Published: December 2007

Western Europe is far from lacking in natural gas. Its gas reserves are much greater than its oil reserves with regard to their energy content, and its gas production covers nearly three-quarters of its own needs, as opposed to only one-third for crude oil. Western European gas reserves are thus an important asset in the security of its energy supplies.

However, most of the increase in European gas reserves over the last fifteen years has come from offshore discoveries, mainly in the North Sea. This zone now contains 60% of the proven reserves and accounts for nearly half of gas production in Western Europe.

This trend will continue in the coming decades, with increasing difficulties in the development and exploitation of new resources, whether due to the water depth or to the increasing distance between consumption regions and recent discoveries. Therefore, the new generation of fields in the North Sea will necessarily call for new technological developments far in advance of the techniques now mastered.

The experience gained during the development of giant fields (Frigg, Troll) together with the studies carried out for the exploitation of marginal fields make up the basis for current research routes, which have been redirected in keeping with the economic situation. In addition to the optimization of proven concepts aiming at greater process integration, new technological developments will aim at both multiphase concepts and subsea implementation. The production of "frontier" gas resources and hence the development of new technologies are the price that Europe will have to pay to limit its dependence on gas imports.
A Predictive Model for Analyzing Erosional Velocity and Corrosion Effects Enhances Optimized Production of a Gas Well System
Authors: Farshad F. F. , LeBlanc J. L. , Root P. J.
Published: December 2007

As depth increases, so do reservoir pressure and temperature and the mole fraction of carbon dioxide and hydrogen sulfide in the reservoir gas. Furthermore, it is becoming more and more desirable for the operators to produce gas at high flow rates. These factors result in an increase in the corrosiveness of produced fluids and the percentage of wells with corrosion problems. Today, it is estimated that over 50% of the producing gas wells in the U.S. are produced under conditions conducive to corrosion (corrosive wells).

Corrosion costs the petroleum industry more than $900 million annually. This includes production down-time, chemical treatment costs, material replacement costs, and increased workover costs caused by additional fishing time needed to retrieve parted tubing and repair damaged casing. Severe downhole corrosion problems may even force the abandonment of a well and the drilling of a new well.

The objective of this paper is to show that the economic development and production of these wells dictates consideration of three separate but related subjects: Total optimization of the production systemLimitation of pressure drop through the gravel packConsideration of erosional velocity

This study will show that the maximum production rates possible from these wells are usually restricted by the following limiting design parameters (1) pressure drop through the gravel pack (for a gravel packed well) and (2) the erosional velocity. Proper evaluation of these critical areas can extend the life of the production tubing in a corrosive well six to seven-fold.

Although this paper is addressed specifically to corrosive wells, the production optimization techniques shown can be applied to almost any other gas production system.
An Integrated Gas Transportation Management System
Authors: Hansen J. A.
Published: December 2007

Today's world of gas brokers, spot markets and interruptible service is not conducive to the monthly cycles of billing and customer reconciliation of imbalances which supported the business of transporting gas for large, established, long-term transportation customers.

Today's gas transmission company must be able to monitor, control, and report transportation business within shorter time constraints. Traditional divisions between real-time pipeline control and custody transfer billing must be removed and computer systems supporting these functions must reflect these business changes.

GSAM is an integrated computer system designed to support real-time and custody transfer transportation management. Through the integration of meter facility, customer, transportation agreement, SCADA, gas composition, and custody transfer volume data, daily monitoring of customer activities and monthly calculations for commodity billing are accomplished to provide pipeline system and customer imbalance control.

In order to function in the deregulated gas industry in North America and remain competitive, gas transportation companies need to not only automate but integrate traditionally segregated areas of real-time pipeline control and custody transfer billing. NOVA Corporation of Alberta is meeting this challenge with a gas transportation management computer system, GSAM, integrating the Gas Supply and Measurement areas.
Furan Resin Process Replaces Workovers in Gas Storage Reservoirs
Authors: Weaver J. D. , Morgan J. A.
Published: December 2007

A furan resin process has been successfully used to stop sand production in underground gas storage wells used by the Illinois Power Company.

The resin process consolidates formation sand into a matrix which is permeable to gas flow but screens sand out of casing perforations. Sand produced with gas can severely damage production equipment, enlarge perforations in the casing, and plug wells so that injection and withdrawal are prevented.

This paper presents a discussion of furan resin characteristics and applications for which it is suited. Treatment methods are detailed and treatment sequences presented. Case histories given for three wells show up to 13 years of gas injection into and sand-free gas withdrawal from storage wells that had previously produced enough sand to stop injection/withdrawal and to ruin valves and other production equipment. Storage wells completed initially with the furan resin process or recompleted after producing sand have required no workovers during the several years since treatment with the resin.
Single-Phase Simulation of an Aquifer Gas Storage Field
Authors: Damle A. S. , Berry R. M. , Kothari K. M.
Published: December 2007

In an aquifer gas storage field, the gas/water boundary or transition zone expands and contracts cyclically due to the cyclic injection and withdrawal of gas in the field. The physical pore volume occupied by the gas phase thus changes with time. Although this change is cyclic, it is usually not in phase with respect to the gas injection and withdrawal cycle due to relatively slow response of the aquifer. The two phase (gas-water) system in aquifer gas storage field can be simulated using a single phase simulator, provided accurate predictions of the gas phase pore volume can be made as a function of gas injection/withdrawal rate and schedule. The established procedure for predicting gas/water boundary movement based on influence functions and the principal of superposition is tedious, time consuming and requires field history data from its early development stages.

This paper presents an alternative approach based on an equilibrium pore volume concept. An equilibrium pore volume at a given time may be defined as the pore volume that will be occupied by the gas in storage at that time if brought to the equilibrium aquifer pressure. At any given time, the actual pore volume occupied by the gas phase may be different than the corresponding equilibrium pore volume; and the difference provides the driving force for the water movement. This approach was successfully used in the analysis of data from an existing aquifer storage field. This concept for predicting gas/water boundary movement was incorporated in a reservoir simulation model to carry out a single gas phase simulation of an existing aquifer gas storage field. The field history was accurately predicted by this simulation procedure. This approach is simple, easy to incorporate in a simulator code, and can utilize current operating history data to obtain necessary model parameters.
Natural Gas From Low Permeability Formations
Authors: Kuuskraa V. A. , Haas M. R.
Published: December 2007

This paper discusses the technology challenges and economically recoverable natural gas from three low permeability sources: tight gas sands, methane from coal seams and fractured, organically rich Devonian age shales. It discusses the nature of the low permeability resources and the technologies being developed by the Gas Research Institute (GRI), the Department of Energy, and industry. The paper contains three case studies where the application of improved technology has led to lower cost gas recovery. It concludes with an overview of the economic potential of gas reserves from low permeability formations.

There are two major themes of the paper: first, in the geologically most favorable reservoirs, natural gas is already being economically produced from low permeability formations; and, second, advances in gas extraction technology are essential for reaching the full potential of this resource.
Future Prospects of Saudi Natural Gas
Authors: Al-Fariss T. F.
Published: December 2007

Saudi Arabia has about 3% of the total world reserves of natural gas. The total annual production of natural gas in Saudi Arabia is about 32 billion cubic meters. Most of this production is from associated gas to the crude oil production. It is also produced from gas fields such as Dammam, Hamur, Jawb, Lawhah, Maharah, Marjan, Shaybah, Zuluf, Abqaiq, Berri, Ghawar, Kidan and Qatiaf. In the past, associated gas were directly flared with little uses as fuel mainly in domestic appliances. It sometimes injected into oil reservoirs to help in oil production. It is often used in industrial purposes either as a source of energy in electricity generation, refinery fuel or in lime or fertilizer manufacturing. Nowadays, natural gas is considered the backbone of many petrochemical industry in the country. This paper will review the current utilization of Saudi natural gas with an insight look toward the brightful future.
Modeling Heterogeneity To Improve 3-D Simulation Results: A Case History on a North Sea Gas Field
Authors: Haak A. M. , Elewaut E. F. M.
Published: December 2007

A 3-D simulation model of a Rotliegend gas field was made to describe the fluid behavior in the reservoir under strong water drive. The model was supported by a detailed geological model giving the lateral distribution of the porosity, horizontal permeability and the flow characteristics of the reservoir rock. The vertical effective permeability was coupled to the horizontal permeability by means of a statistical probability technique.

The model was matched satisfactorily with the decline of the average field pressure and with the detectable water movement in the field (including water breakthrough in one of the producing wells). The adjustments to the matching parameters were endorsed by the geological research. The geological model thus provided a base for an adequate and relatively simple modeling procedure.

The simulation model indicates that the gas-water contact in major parts of the field is at present located at a higher level than is supported by field observations. The presence of fluviatile shaly members plays an important role in the water movement in the field. It is believed that field observations on the water movement may to some extent be masked by the presence of major shale breaks in the eolian units in the vicinity of the wells.

The simulation model was used successfully to predict fluid movement in the reservoir.
Velocity of Sound Correction of Vibrating Element Density Transducers.
Authors: Norvik H. A. , Tambo M.
Published: December 2007

A mathematical model for ‘vibrating element’ density transducers is derived. The origin and magnitude of reading errors inherent in this type of instrument is analysed. The theory is substantiated by newly acquired experimental data, covering a wide range of pipeline operating conditions up to 150 bar. The model is believed to be suitable for correction of density meters in field applications. The treatment specifically deals with ‘cylindrical membrane’ transducers, but the qualitative findings are believed quite generally applicable.
Iron Sulfide Scaling and Associated Corrosion in Saudi Arabian Khuff Gas Wells
Authors: Kasnick M. A. , Engen R. J.
Published: December 2007

Khuff reservoir gas wells have been produced for 5 years in Saudi Arabia. These wells are classified as sour gas producers with hydrogen sulfide and carbon dioxide contents of four to five mole percent each. The production contains 1.5 to 2 barrels water per million standard cubic feet of gas with a moderate (30–50 barrels per million standard cubic feet of gas) amount of heavy condensate.

Scales with iron sulfides as the major components form in nearly every producing well. These scales have minor compositional variations but form at differing rates and thicknesses in the lower half of the L-80 tubing string. Tubing has been recovered with scale deposits from several wells. Intense analysis of the scale, the underlying corrosion, and the metal pipe have revealed information about scale formation in these wells. Although the investigation continues, several conclusions regarding the causes of scale formation, the effects of completion practices, and recommendations for mitigation are discussed.
Quantitative Evaluation of Highly Laminated, Complex Lithology Formations
Authors: Andreani M.
Published: December 2007

Thinly bedded and laminated shale-sand-carbonate formations exist in most of the producing formations in Egypt (a thin bed is defined as having a thickness of the order of two inches). Over certain sections of the field considered in this paper, such formations make up the bulk of the reservoir, and conventional interpretation techniques could mask the true nature of the formation, resulting in an erroneous evaluation and the possible risk of missing the reservoir completely. This paper outlines an interpretation technique which has been developed to evaluate the thin producing zones and their contribution to a formation's producibility. With this information it is possible to know, with accuracy, the size of the reservoirs, where to perforate, and the test intervals to consider.

Both the attenuation (Eatt) and the transit time (Tpl) of the Electromagnetic Propagation Tool (EPT*) are used to evaluate the laminated shale and lithology distribution. The attenuation is calibrated to provide a direct and quantitative shale content value with excellent vertical resolution and pass-to-pass repeatibility with the sonic transit time and neutron porosity (ΔT - øN) shale indicator, which is an established reference in this environment. The Tpl measurement, after compensating for the shale volume, is used effectively to differentiate the matrix lithology. This gives calibrated thin bed shale and lithology transforms, which are combined with conventional logs to evaluate the porosity and saturation values. The computed water saturation in the invaded zone is used to obtain high resolution permeability and producibility for all the layers. The results are compared with well test and high resolution dipmeter data. It is found that the producibility data, predicted by this technique, matches the flowmeter data. This technique is used successfully to identify transition zones in laminated beds. In addition, the recoverable volume of reserves in shaley, laminated reservoirs, is often found to be much higher than previously expected.
A Simulator for the Recovery of Heavy Oil From Naturally Fractured Reservoirs Using Cyclic Steam Injection
Authors: Briggs P. J.
Published: December 2007

This paper describes a simulator which has been developed for the specialised application of predicting the performance of cyclic steam injection, when used to recover heavy oil contained in naturally fractured reservoirs. The potential application of the simulator will be for evaluating fractured carbonate reservoirs, which contain a large proportion of the known heavy oil resources.

The reservoir is divided into a rock matrix/fracture system with the rock matrix assumed to be described by a number of cubic blocks surrounded by interconnecting fractures. The flow of injected steam and its condensate is limited to the fractures and heat transfer to the rock matrix is only by conduction. The temperature of the matrix blocks and the heat lost to the overburden/underburden are obtained using an approximate analytical solution to the heat diffusivity equation. The simulator then predicts the rate of interchange of fluids from rock matrix to the fractures by the processes of thermal expansion and countercurrent imbibition. Production rates of oil and water from the thermally stimulated well are calculated, based on a PI which is adjusted to account for the temperature dependent fluid viscosities and the fluid heights in the fractures. During the production period, the heat loss to the overburden/underburden and the produced fluids is calculated at each time step.

Results from the model show the advantage of a fracture system in conducting heat into the rock matrix, because of the large surface area exposed to heating. The simulator can be used to investigate the interaction between various reservoir and input parameters in an attempt to devise the best reservoir management strategies. Initial results show the importance of steam slug size, steam injection rate, steam temperature and applied drawdown in attaining the best economic operating conditions. The matrix block size and permeability were found to be the most important of the reservoir variables changed in the sensitivity analysis.
History Match and Future Production Strategy of a Multi-Reservoir Field
Authors: Sheshodia T. S. , Mubarak S. I. , Javed M. S. , Rahman B. A.
Published: December 2007

The paper briefly describes the reservoir simulation model, history match, fluid migration and future production strategies of a multi-reservoir oilfield in Kuwait. The reservoirs have production history of forty years and about 28 percent of in-place oil have been recovered. Edge-cum-bottom active water drive from an extensive aquifer has helped to maintain the reservoir pressure in major parts of the field. Water intrusion has taken place in some wells due to bottom water coning and in few others due to water fingering.

Variation in lateral as well as vertical fluid migration with production changes is found interesting. The increase in quantum of water cut production with time has been predicted to facilitate timely planning for proper design of produced water disposal. Infill wells have been recommended for proper drainage and for enhancing the production potential of the field for a longer period.
Tests of ASR, DSCA, and Core Discing Analyses To Evaluate In-Situ Stresses
Authors: Perreau P. J. , Heugas O. , Santarelli F. J.
Published: December 2007

The vertical distribution of the minimum horizontal in-situ stress is the major parameter which controls the confinement height and direction of hydraulic fractures. The minifrac technique has been extensively used to collect these data. However, its implementation in the payzone and adjacent layers is often hindered by technical and economic considerations. Consequently, the determination of the stress field on the basis of laboratory measurements in orientated core samples has been investigated. New developments and the results of three methods are described: anelastic strain recovery (ASR), differential strain curve analysis (DSCA), core discking analysis. The results obtained using these methods on cores extracted from several wells are described and discussed. A comparison is made with data available from minifracs, logs and regional tectonics. The main conclusions are that different methods give a good idea of the principal horizontal stress.
Operation of a Second Steam Stimulation Pilot Project in Kuwait
Authors: Ahmad K. N. , Milhem M. M.
Published: December 2007

Two pilot steam stimulation projects were initiated to study the feasibility of application of steam for recovery of heavy oil occuring in a shallow depth reservoir in Kuwait.

The first pilot cyclic steam stimulation project was started in September 1982 with 4 wells1. This is still in the first production cycle with an overall OSR of 10.316 till end September 1988.

The second pilot cyclic steam stimulation project was commissioned in June 1986 and steam injection to the first well commenced on 25th June 1986. Injection continued from well to well and terminated in the 4th well on 23rd August 1986.

The salient features of this pilot are: 1)Use of treated brackish water produced from a shallow water well.2)Facility to switch steam from one well to another without interruption of operation by using combination steam and oil header.3)Compared to the first pilot a very short natural flowing life of the wells.4)Long distance pumping of the crude oil without any additive or pipeline heating.

These 4 wells are now in the production cycle and they have produced 222,874 bbls [34,434m3] of oil by 30th September 1988 with an overall oil steam ratio of 3.0832.

There was no primary production.
Planning of an Appraisal/Development Program for the Complex Khuff Carbonate Reservoir in the Yibal Field, North Oman
Authors: Bos C. F. M.
Published: December 2007

In 1986, oil was discovered in the Permo-Triassic Khuff carbonates of the Yibal Field in North Oman. This formation, which covers extensive areas of the Arabian Peninsula and Arabian Gulf, had hitherto never tested oil and the Yibal Khuff accumulation is therefore unique in the region.

Dry but sour oil rates of up to 1 200 m3/d [7 550 bbl/d] were tested at a depth of 3 036 m [9 960 ft]. Subsequent appraisal wells, however, revealed the reservoir to be highly complex and dramatically downgraded initial expectations of an early, large scale development.

This paper describes the stepwise approach adopted to meet the dual objective of better defining the reservoir whilst at the same time developing the reserves in a cost effective way.

To this end, an appraisal/development plan has been designed consisting of the installation of limited liquid and gas handling facilities, further appraisal drilling, coring and extensive production testing.

The synthesis of production test, reservoir geological and petrophysical interpretations has allowed the construction of a conceptual reservoir model consisting of a prolific, fractured crest where early gas breakthrough hampers the oil productivity and marginal, low permeable flanks. Areas of non-producible oil have also been identified.
Evaluating Tracer Response of Waterflood Five-Spot Pilot: Dukhan Field, Qatar
Authors: Al-Dolaimi A. M. , Berta D. , Dempsey M. J. , Smith P. J.
Published: December 2007

A five spot pilot waterflood was designed to investigate the reservoir potential of the Upper Reservoir Section, Arab ‘C’, Dukhan Field, Qatar. The long term plan involves development of these reserves which have been by-passed by the peripheral waterflood presently generated through the Lower Section. The monitoring programme over the five year period of the pilot has consisted of pressure and production/injection testing, open hole and cased hole log surveying and processing, a full suite of laboratory measurements on the produced effluent water and a full programme of data acquisition on an observation well. Radioactive and chemical tracers have been injected and their activity regularly determined in the produced water. These data plus the production water-cuts and salinities represent important evidence in unravelling the complex behaviour of the Upper Reservoir Section. This complexity stems from the highly heterogenous reservoir material and the variable production and injection rates.

This paper describes a three pronged approach to analysing these data:– AAnalytical Tracer EvaluationBSingle-Well ModelCThree Dimensional Models of the Region

In Part A we apply analytical tools to interpret the tracer and salinity response. By assuming constant production rates, no permeability variation and no cross flow a broad characterisation of the reservoir is obtained.

In Part B the variability in the reservoir and injection/production rates can be accommodated by the numerical simulator. Moreover, a tracer option in the simulator is used so that the formation, injection, and tritiated waters can be individually tracked. The results of Part B suggest that a reservoir characterisation based on many separate layers is unnecessary since much of the variability in tracer response can be produced by a few layers.

Finally, in Part C by developing a three dimensional 10000 cell model of the five-spot area, based upon the findings from A and B and a previously constructed coarse full field model, the dependency between the different well responses can be more fully understood.
Enhanced Recovery by Horizontal Drainholes
Authors: Dijkum C. E. van
Published: December 2007

In 1986 PDO has drilled 3 horizontal dralnholes to gain experience with the horizontal drilling technique and to assess the gain in well productivity. The three wells (horizontal section 65-120 m) have been drilled in low permeability formations (permeability 1-30 mD) with oil columns ranging from 20 to 60 m.

In view of the thin oil columns and drilling difficulties in overlying shales the dralnholes were drilled by a small radius (9-12 m) technique. The drilling of the horizontal sections was completed in 42 days. No problems were encountered during drilling.

Analysis of the production performance shows that a horizontal drainhole can enhance oil production substantially, provided its location with respect to the 0WC is optimal and its orientation is such that in a heterogeneous formation it penetrates several layers.

To improve the understanding of the horizontal drainhole simulation studies have been carried out to match production history and pressure build up test. Both the historical and the predicted performance of a horizontal well are compared with a vertical well. The actual and simulated performance of the horizontal well shows that oil production Is enhanced by a factor two to three.

Another objective of horizontal wells may be the suppression of waterconing. A scouting study on the performance of a horizontal well in a high permeability reservoir with high watercut shows that, contrary to expectation, no significant improvement in oil production was calculated.
Petrology and Diagenetic Effects of Carbonate Rocks: Jurassic Arab C Oil Reservoir in El Bunduq Field, Offshore Abu Dhabi and Qatar
Authors: Honda N. , Obata Y. , Abouelenein M. K. M. , Kitagawa H. , Negishi T.
Published: December 2007

The depositional and diagenetic model of the Arab C4 Reservoir (Upper Jurassic) in EL Bunduq Field is constructed based on core studies (sedimentological core examination, petrographical analysis of thin sections, petrophysical core analysis, scanning microscopy, cathodoluminescence analysis, X-ray diffraction analysis) and wireline log data from 13 cored wells.

The Arab C4 Reservoir which comprises one of the main oil reservoirs in the Field is composed of inter-bedded limestones, dolomites, and anhydrites displaying lagoonal, tidal flat, and sabkha environments. The following seven different lithofacies have been identified. (1)Bioclastic Grainstone Lithofacies(2)Pelletoidal Grainstone Lithofacies(3)Oolitic Grainstone Lithofacies(4)Laminated Carbonate Mudstone Lithofacies(5)Mottled Carbonate Mudstone Lithofacies(6)Algal Boundstone Lithofacies(7)Nodular Anhydrite Lithofacies

Reservoir quality is best within lime grainstones and dolomitised grainstones. The original depositional textures have the most important effects on reservoir quality. For example, grain-supported limestones often preserve their original intergranular porosities. While limestones with mud matrix have generally poor reservoir quality. Moreover, the depositional environments and primary pore systems within the sediments themselves have a great influence on the subsequent diagenetic processes.

Deposition within mainly intertidal to supratidal environments resulted in early surface related diagenetic processes and then the sediments were subjected to later stage, deeper burial diagenetic processes.

The following processes can be recognized; (1)Surface Diagenetic Processes Micritisation,Pyrite Formation(2)Early Stage Diagenetic Processes LeachingCalcite CementationDolomitisationAnhydrite GrowthEarly Compaction(3)Later Stage Diagenetic Processes Later Compaction and Pressure SolutionBitumen ImpregnationFracturing

The most significant diagenetic processes affecting the reservoir quality are leaching, calcite cementation dolomitisation, and replacement by anhydrite which took place early in the diagenetic history within near surface environments.
Inversion Technique To Determine the In-Situ Stress Field From Fracturing Data
Authors: Aadnoy B. S.
Published: December 2007

Typically one assumes that the two horizontal in-situ stresses are equal in borehole stability studies. This simplification has been necessary due to lack of information. The new method presented here distinguishes between the in-situ stresses and estimates the magnitude and the direction of each of the two horizontal in-situ stresses. The input data used are the leak-off fracturing information.

The new method uses stress transformation equations to take advantage of the directional characteristics of offshore boreholes. By including the hole inclination and the azimuth, one can solve for the two unequal horizontal in-situ stresses. The model results in finding the inverse of an overdetermined system of equations. A field study demonstrates the method.
The Separation of Electrolyte Effects From Rheological Effects in Studies of Inhibition of Shales With Natural Moisture Contents
Authors: Beihoffer T. W. , Dorrough D. S. , Schmidt D. D.
Published: December 2007

The shale rolling test is a common procedure that is used to measure the interactions between drilling fluids and shales. This study found that the results of the shale rolling test depend on the moisture content of the shale, the shale composition, the viscosity of the test fluid, the rotation speed of the rollers, and the test temperature. To obtain reproducible results, all of these variables must be carefully controlled.

The rheological behavior of the test fluid has the strongest influence on test results. This led to the conclusion that the rolling test is only valid for unviscosified drilling fluids. This severely limits the applicability of the test.

Drying the shales caused changes that influenced test results. This indicates that, when possible, tests should be run with shales of native moisture content.

When test variables are carefully controlled, the rolling test is a useful technique to measure the interactions of electrolytes with shale granules in partially formulated drilling fluids.
Design and Synthesis of Shale Stabilizing Polymers for Water-Based Drilling Fluids
Authors: Sheu J. J. , Perricone A. C.
Published: December 2007

Troublesome shales can cause costly downtime due to stuck pipe, hole-fill and even hole abandonment. Much research effort has been expended in an attempt to better understand shales and their interaction with drilling fluids. A combination of cations with water soluble polymers are known to effectively stabilize many shale formations including combinations of potassium chloride with partially hydrolyzed polyacrylamide (PHPA). This paper will focus on general aspects of how PHPA and other polymers stabilize shales. In the stabilization of shales by various chemical agents, the specific mechanism by which polymers stabilize shales has not been studied in detail. A shale stabilizing mechanism based on polymer adsorption onto clay surfaces and how solution properties of polymers affect this mechanism, will be proposed. Several simple approaches to the design and the synthesis of improved shale stabilizing polymers for water based drilling fluids will be discussed.

A commonly used shale disintegration test has been modified for use in screening many shale stabilizers. This test method is capable of generating statistically reproducible results and has provided some mechanistic information on shale stabilizers. Such information is valuable and has led to the design and the synthesis of a new improved polymer useful for shale stabilization in water-based drilling fluid systems.
Economic and Performance Analysis Models for Solids Control
Authors: Lal M.
Published: December 2007

This paper presents two models which provide an analytical basis for the economic analysis and selection of proper solids control equipment. The economic analysis model predicts the relative savings in mud dilution and wastes disposal costs for various percents of drilled solids removal and for the closed-loop implementation. The performance analysis model analyzes the performance of a given solids control system in terms of its solids removal capacity. A recent case history illustrates the importance of these models and confirms the savings predicted for a closed-loop implementation.
Offshore Tests of Diamond-Enhanced Rock Bits
Authors: Salesky W. J. , Swinson J. R. , Watson A. O.
Published: December 2007

Maintaining full gage hole while drilling the chert laden Monterey formation offshore California is a constant problem due to the highly abrasive nature of the rock. Three cone rock bits having conventional tungsten carbide gage inserts wear severely necessitating reaming as well as frequent replacement of downhole tools.

Offshore bit tests have been performed on three cone bits with highly wear resistant diamond enhanced gage inserts. These test results have shown these new bits to be capable of drilling in-gage holes through the Monterey formation, and as a consequence, reaming has been significantly reduced.

This paper will give an overview of the drilling problems encountered offshore California. A discussion will be provided on the diamond enhanced insert technology and its impact on drilling performance, downhole tool replacement and reaming time in the Monterey formation offshore California.
An Improved Modeling Program for Computing the Torque and Drag in Directional and Deep Wells
Authors: Ho H. -S.
Published: December 2007

In directional and deep wells, the torque and drag generated by contacts between the drillstring and the borehole play major roles in the following operations of the well: planning, drilling (trouble diagnosis and prevention), and casing running/setting.They also affect the completion/cementing operation.

This paper discusses the shortcomings of the "soft-string" model, which has been widely used in the drilling industry. The soft-string model ignores the effects of drillstring stiffness, stabilizer placement, and borehole clearance. Consequently it generally shows reduced sensitivity to local borehole crookedness and underestimates the torque and drag.

An improved modeling program is presented here that combines a BHA (bottomhole assembly) analysis in the stiff collar section, coupled with an improved soft-string model for the remainder of the drillstring.

Case studies are presented to demonstrate the difference between this improved model and the soft-string model; and also to justify the approach of the improved model.

For deep vertical wells, spiraling of the well can result in very severe torque and drag. Simplified formulas are derived, and examples are given to demonstrate the exponential increases of torque and drag as the well depth increases. In essence, deep vertical wells with spiraling tendencies should be handled as directional wells.
Enhanced Oil Recovery Evaluation of the Flounder T-1.1 Reservoir
Authors: Younes A. M.
Published: December 2007

Under a different and healthier pricing environment, Esso initiated engineering and laboratory work to evaluate a miscible gas process at Flounder. The objective of the evaluation was to study the benefits of immiscible gas injection as well as the potential of achieving miscibility and hence, an incremental oil recovery from the field. To accomplish the project objective, a simulation study and laboratory evaluation of Flounder oil and gas samples were undertaken.

The laboratory studies were necessary to define the miscibility conditions to be expected at Flounder. The simulation study was undertaken to determine if the Flounder reservoir characteristics, such as dip, stratification and permeability contrast, are favourable to achieving higher oil recoveries by gas injection. This paper reviews the results of the simulation and laboratory work which was undertaken at Esso, Exxon Production Research Company and the University of New South Wales.
Transport Mechanisms of Xanthan Biopolymer Solutions in Porous Media
Authors: Kolodziej E. J.
Published: December 2007

The propagation of a polymer slug through porous media is affected by several transport mechanisms including polymer adsorption, inaccessible pore volume, and dispersion. In many previous studies, a specific mechanism (e.g. adsorption) is evaluated, but few studies attempt to evaluate all three mechanisms under a consistent set of flooding conditions. In this paper, a comprehensive study was conducted to evaluate the simultaneous effects of these three mechanisms for single-phase Xanthan biopolymer core floods at 100% brine and at residual oil. The polymer concentration was systematically varied in these floods. The effects of inaccessible pore volume were also investigated in a two-phase Xanthan biopolymer flooding experiment in an initial oil-saturated core. Several key trends on the effects of polymer concentration and residual oil for these polymer transport mechanisms were noted. Attempts are then made to rationalize these trends in terms of microscopic (i.e. molecular and pore level) effects.
Interpretation of High Recovery Obtained in a New Polymer Flood in the Chateaurenard Field
Authors: Putz A. G. , Lecourtier J. M. , Bruckert L.
Published: December 2007

The Courtenay polymer flooding test is being completed, using a larger than usual slug size; a special attention was given to monitoring the concentration and quality of the effluents.

The test is implemented on a ten acres inverted five spot in the center of the field of Courtenay, which is part of the Chateaurenard field. A rather large slug of partially hydrolized Polyacrylamide was injected, consisting of 42% pore volume of a 1000 ppm active polymer concentration solution followed by a 39% pore volume solution at a tapered concentration.

By matching the oil cuts and polymer concentrations in the effluents of the producing wells we estimate that the adsorption of the polymer on the rock was 35 μg/g of rock.

Concentrations and main characteristics of produced polymer at the wellhead were determined using a sampling and separation methodology which prevents chemical and mechanical degradation. An increase in polymer molecular weight versus time has been observed, this polymer is not harmed by flow in the reservoir.
Performance Update of a Dual-Resistivity MWD Tool with Some Promising Results in Oil-Based Mud Applications
Authors: Grupping T. I. F. , Harrell J. W. , Dickinson R. T.
Published: December 2007

A new "Toroidal" Measurement While Drilling (MWD) resistivity tool was introduced to the oil and gas industry in 1986. The tool utilises the drill collar as an electrode to provide two independent resistivity measurements: a focused lateral resistivity measurement and a trend resistivity at the drill bit. In oil based muds the tool provides a single high-resolution measurement at the bit-to-formation contact.

Since its introduction the tool has been operated in a variety of diverse drilling environments, both in the North Sea and in North America, and in a wide range of drilling fluids including oil based muds.

This paper reviews the performance of the tool with specific log examples highlighting the qualitative and quantitative responses of both resistivity measurements in comparison to conventional wireline logs. Particular attention is also given to the advantages and limitations of logging in the MWD environment.

As a result of these operating experiences several changes were necessary in order to improve the reliability of the tool and to ensure good log quality, especially in fast drilling formations. These problems together with the effected solutions will also be presented.

Finally a brief review will be made of future enhancements to MWD systems which will provide additional sensors for formation evaluation and reservoir analysis.