bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated Modeling of a Field of Wells—An Evaluation of Western Shallow Oil Zone Completion Practices in the Elk Hills Field, Kern County, California
Authors: Callison Dave , Jones Joe , Shelley Bob , Lockman Rusty
Published: December 2007

A fresh or different perspective is essential to discovering new opportunity for successful field development. This paper summarizes a new type of analysis applied to reservoir, well, completion, and fracture stimulation information for the western shallow oil zone (WSOZ) completions in the Elk Hills Field of Kern County, California. The focus of this analysis was to identify parameters that are indicators of reservoir quality and to evaluate the effectiveness of stimulation/completion methods.

This evaluation used unstructured modeling methods supported by the use of standard engineering tools. Of particular interest was the identification of ways to help enhance the economic success of WSOZ completions at Elk Hills. When the information derived from this study was applied to new completions, well economics improved significantly. This improved success has justified additional infield development drilling. Specific objectives included:Developing a model or tool to predict production for wells in the fieldIdentifying parameters that are indicators of reservoir qualityDetermining which completion/stimulation methods and designs have been successful in the past and using this information to improve the success of future completionsUsing the above understandings to improve fracture candidate selection

A general objective was to test the applicability and benefits of holistic modeling methods, such as using artificial neural network (ANN) technology to model WSOZ wells at Elk Hills. In this instance, ANN modeling was used to differentiate the contributions of reservoir quality from the stimulation/completion method on a given well production result. The understanding derived from this study influenced decisions about pay selection, perforating practices, operational procedures, and stimulation fluid and proppant selection.
The Application of Pressure Isolated Multilateral Junction Improves Economics in Offshore Arabian Gulf
Authors: DeMong Karl , Al-Yami Hussein , Lambe Steven
Published: December 2007

The benefits of drilling multilateral wells in slot limited applications such as offshore platforms are well known. Using multilateral technology in a project can minimize facility costs, reduce drilling costs, maximize reservoir exposure and reach secondary targets. When a project is in the planning stage, there is often resistance to multilateral concepts due to a perception of increased operational risks and doubts that the economic benefits will be fully realized. The key to broadening the implementation of this technology is matching actual opportunities with robust, reliable multilateral systems.

In a project in the Arabian Gulf, an operator implemented the use of Technical Committee for the Advancement of Multi Laterals (TAML) level 5 pressure isolated junction systems with through tubing access to develop a single reservoir in a slot limited application. Both pre-milled and retrievable oriented milled window technology were used as a platform for the completed junction. This illuminates how this technology is used in new or existing wells.

A study of how the unique operational issues were solved illuminates the success of the application of this technology to this project. It will also provide an insight into best practices to aid in the planning and execution of other complex well types. Operational and economic results, as compared to single lateral wells on the same platform, provide insight into many advantages realized in this program.
Examination of Cement and Casing Evaluation Logs, a Field Study
Authors: Frisch Gary , O'Mahoney Larry , Mandal Bata
Published: December 2007

An analysis was undertaken to appraise the effectiveness of using the current logging program to evaluate both casing damage and the cement sheath for a major offshore field. The standard program consisted of a Conventional Bond Log (CBL) and rotating ultrasonic tool run in tandem. Four different casing sizes were evaluated, running from 5.5-in., 23 lb. to 9 5/8-in., lb. and including several different alloys ranging from standard steel to chrome alloys. These logs were acquired over several years. The suite of logs involved upgrades to both the acquisition software and to the rotating ultrasonic tools. These changes affected both the casing inspection and cement evaluation modes.

The overall correlation between the rotating ultrasonic log and the CBL log are excellent as shown in exa mples that will be provided. These logs demonstrate how two different cement evaluation tools complement each other to provide a detailed and complete zonal isolation study. The rotating ultrasonic may indicate channels while the CBL may not provide a direct indication of the channel.

Likewise, the rotating ultrasonic shows excellent repeatability in both casing inspection and cement evaluation data. Casing inspection consists of both internal diameter and casing thickness. While the casing size will affect the cement evaluation, the rotating ultrasonic tool requires careful head and frequency selection to optimize the casing inspection mode. The repeatability and accuracy of the casing inspection data is astonishing and exceeds that of any other casing inspection device in use today.

Several logs that will be described have questionable features, but some of these features appear to be caused by well conditions. In particular, it is believed that casing in contact with either the formation and/or outer casing string caused erroneous readings in both the cement and casing inspection data. This perceived wellbore artifact also appears to create errors in the CBL for cement evaluation. Casing centralizers and/or lack of centralizers are easily recognized on both the casing inspection data and cement evaluation.

In another case, improper head selection for the ultrasonic device generated an erroneous log. Changes were made to the real time quality control process on the device to prevent erroneous logging from happening thereafter.
Analytical Models for Design of Wellpath and BHA
Authors: Aadnoy Bernt S. , Huusgaard Petur P.
Published: December 2007

Directional drilling is costly. Roundtrips of the entire drillstring is often required to implement directional corrections. The directional driller is a specialist using numerical simulators for analysis. To simplify this, work was undertaken to derive simple analytical equations that would replace the simulators, and, to gain further insight into the controlling mechanisms.

The first part of the paper investigate the minimum weight and length of the BHA. Performing a force balance, including torque and drag (Coulomb friction), minimum BHA length are obtained both for rotating and sliding mode.

The second part of the paper is based on indeterminate beam theory. Explicit equations are derived to model the two key mechanisms; weight (gravity) and geometry (BHA deflection). The equations clearly shows that the build-rate depends on wellbore inclination. Using the insight from the models it is shown that a catenary (minimum friction) wellpath can be approximated by proper stabilizer placement, and can be drilled without altering the BHA, that is, no correction trips are required.

Several practical examples are provided, including a well drilled to 110 degrees inclination. It is shown that buckling defines the maximum bit force, and also shown is the design of such an operation, including optimal placement of stabilizers and drillcollars.
Hardbanding for Drilling Unconsolidated Sand Reservoirs
Authors: Barrios Juan , Alonso Claudine , Pedersen Eric , Bachelot Alain , Broucke Alain
Published: December 2007

Hardbanding materials are used to protect tool joint drillpipe against wear in drilling operations. Hardbanding shall resist wear in openhole conditions with a minimum damage to upper casing. Laying down drillpipe for hardbanding repair can significantly increase rig time and tubular costs. All hardbanding products applied for Sincor were wearing out completely after drilling 15,000 ft in 50 hours in the reservoir. It was necessary to search for new hardbanding alternatives with an extended lifetime. A field evaluation program was designed to compare wear resistance of different commercial hardbanding materials and to evaluate new techniques for welding tungsten carbide pellets with alloying wires and for testing of tungsten carbide spheres being laser applied. Hardbanding products were selected upon analysis of wear mechanisms occurring in drillpipe while drilling horizontal wells in Sincor. Wear resistance was monitored in terms of cumulative drilled footage until gauging complete wear of hardbanding on tooljoints. One of the newly developed hardbanding products was finally selected as the best option after considering its superior wear resistance, minimum expected casing damage, and moderate cost. This is the first reported successful application of tungsten carbide pellets welded within a hard matrix provided by an alloy wire for hardbanding purposes.
The Impact of HCl to HF Ratio on Hydrated Silica Formation During the Acidizing of a High Temperature Sandstone Gas Reservoir in Saudi Arabia
Authors: Thomas R. L. , Nasr-El-Din H. A. , Mehta S. , Hilab V. , Lynn J. D.
Published: December 2007

Since the mid-1990s the use of HCl/HF at a weight ratio of 9 to 1 has been used extensively in field operations to minimize precipitation during sandstone acidizing. Although it was perceived as applying to all secondary reactions, it was originally directed at fluosilicates. Field case histories have been reported to support this recommendation. However, little evidence is available to justify the use of 9 wt% HCl – 1 wt% HF (9-1 mud acid) at the 300°F temperature exhibited in the Jauf reservoir. Thus, a laboratory study incorporating HF systems with various HCl to HF ratios was performed to quantify the amount of precipitation in Jauf reservoir cores at 300°F, and the impact on permeability. The focus of this paper is on the silicon (Si) and aluminum (Al) concentrations in core flow test effluents that were corrected for post-core test precipitation of reaction products in collection tubes. This technique accounts for the Si and Al in the liquid and solid phases of core flow effluents.

The literature teaches that the Si/Al molar ratio of a core test effluent can be used as a diagnostic tool to quantify hydrated silica formation. It is assumed that hydrated silica precipitation increases as the Si/Al ratio decreases from the theoretical value as a result of a greater completion of the secondary and tertiary reactions of HF with silt and clays. The results of this study on short Jauf reservoir and Berea cores at 300°F indicate that cores treated with 9 wt% HCl – 1 wt% HF yield a lower Si/Al ratio than observed with 12 wt% HCl – 3 wt% HF. However, cores treated with 4 wt% HCl – 1 wt% HF yield the lowest Si/Al ratio. The Si/Al ratio is not the only diagnostic tool required to determine the amount of hydrated silica precipitation i.e. factors including the mud acid flow pattern (matrix vs. channel) have a significant impact on the Si/Al ratio.

Core flow test results are presented for acetic acid preflush followed by various mud acid systems. All cores were stimulated, although hydrated silica formed in all core tests and aluminum fluoride precipitated in core tests using 4-1 mud acid formulations at 300°F.
Filtercake Cleanup Techniques for Openhole Water Injectors with Sand Control: Lessons from Laboratory Experiments and Recommendations for Field Practices
Authors: Parlar M. , Brady M. E. , Morris L. , Ali S. A. , Twynam A. , Newberry P. , Svoboda C. , Foxenberg W. E.
Published: December 2007

Many water injection wells in sand control environments are being completed as open holes because of the higher injectivities attainable with open-hole completions. The sand control techniques used in these wells varies from standalone screens or slotted liners (including expandable screens) to gravel packing. In field practice, the drilling fluids used for injectors have also varied from water-based (either sized CaCO3/Polymer or sized-salt/polymer) fluids to oil-based systems. Although a cake cleanup followed by a production period is typically desirable to maximize injectivity, often this is not feasible either due to limited storage capacity on the rig or requirement for artificial lift due to low reservoir pressure. These limitations therefore necessitate direct injection after the completion is installed, which is not trivial as a complete and uniform filtercake removal, including drill solids as well as the bridging agents and polymers, is essential to ensure uniform injection profile in addition to maximizing injectivity index. Although exceeding the fracturing pressure can establish injectivity through bypassing of filtercake damage, this is typically not desirable from a sweep efficiency standpoint.

In this paper, we present details of a series of experiments conducted on core samples using both water-based and oil-based reservoir drilling fluid systems and various cleanup techniques involving displacements and soaks in standalone screen and gravel pack environments. It is shown that with the properly selected and designed cleanup treatments, uniform and high injectivities without producing the well is achievable in long open holes. The results from the experiments are discussed in detail, along with the lessons learned and recommendations for field practice.
A Practical Approach to Evaluating the Value of Information and Real Option Decisions in the Upstream Petroleum Industry
Authors: Coopersmith E. M. , Cunningham P. C.
Published: December 2007

The upstream oil industry lives in the world of Value of Information (VoI) or Real Options (RO) decisions, although many find the evaluation of these types of decisions difficult and/or cumbersome, at best. A shortage of time and calculation complexity are the common arguments used to negate a consistent decision approach to daily decisions spanning from reprocessing seismic, to selecting a development concept, to optimizing the completion technology for a given field. However, with the rapid advance of oilfield technology, and the higher cost of many oilfield decisions, the frequency, and importance, of embedded decisions (exercised after acquiring information) has increased tremendously.

This paper reviews the concepts associated with valuing information and introduces a practical methodology to both "frame" (set up) and value the acquisition of information and embedded decisions. The proposed methodology combines some classic and new decision analysis problem framing tools, Bayesian theory, and a few pragmatic steps - rigorously applied, to result in a repeatable approach, which organizations can readily adopt and disseminate.

The authors propose that both a pragmatic methodology and a sound understanding of the "anatomy", or pattern, of value of information decisions in the oil industry are vital to promoting efficiency and accuracy in asset management. For too long, our industry has claimed to understand how to value information, and embedded decisions, but lacked the consistent use of the methodologies discussed in any widespread and practical manner. Hence, the objective of this paper is to describe a pragmatic approach to evaluate upstream Value of Information ("VoI") or Real Option decisions - and share an illustrative example, using the proposed methodology. The case described will demonstrate the non-intuitive nature of these types of decisions, when taken without the use of some form of decision structure. It will also illustrate the benefit of both problem framing tools and practical decision analysis rigor to promote the right conversations and insights to information decisions.
New Technique Restores Initial Fluid Efficiency Observed in Mini-Frac and Results in Increased TSO Frac-Pack Success
Authors: Holcomb W. D. , Landry T. J. , Comeaux B. A. , Usie M. J. , Smith J. E. , Rivas L. F.
Published: December 2007

It has been observed that pumping a mini-frac prior to a TSO Frac-pack can impact the effectiveness of the frac-pack. The calculated fluid loss parameters determined in the diagnostic test are often not valid for the main fracture design due to the residual effect of the mini-frac and/or step-rate fluids. A technique will be presented in this paper which allows the calculated fluid loss parameters from the diagnostic test to be used reliably without excessive waiting time for the reservoir to recover to its original leak off characteristics. Fifty plus treatments were evaluated to develop a technique which makes this possible. The use of this technique resulted in a significant change in the success of the TSO designed treatments - success being a TSO type pressure increase while pumping. The success rate to achieve designed TSO, by incorporating the changes described in the paper, was increased over 20 percent with a reduction in time between diagnostic tests and the main frac.

In the wells associated with this paper, a borate-crosslinked fluid was used for a mini-frac treatment followed by a steprate test prior to the main proppant laden frac-pack. The fluid was designed with minimal polymer loading for the well conditions. The resulting mini-frac tests had low fluid efficiencies. It was originally thought that using this fluid, followed by injection of a linear step-rate fluid, would minimize the changes observed in fluid efficiency between the diagnostic test and the main fracture treatment. However, the effect of the diagnostic test on fluid leak off still resulted in less than desired TSO predictability.

A technique of adding a pH control additive into the final portion of the step-rate test fluid was found to successfully allow the use of the observed diagnostic test results, honoring the efficiency from the mini-frac test. The quantity and placement of the pH control agent in the step-rate protocol were dependent upon well conditions. The waiting time between the diagnostic test and the main treatment was reduced since a positive, controlled change was applied. The optimum pH reduction for the desired effect was determined in the laboratory and designed into each treatment depending upon well conditions.
Use of Core Data in Log Lithology Calibration: Arab-D Reservoir, Abqaiq and Ghawar Fields
Authors: Ma S. M. , Al-Muthana A. S. , Dennis R. N.
Published: December 2007

The Arab-D is the main oil-producing reservoir in the giant Abqaiq and Ghawar fields. Accurately determining its lithology is important for petrophysics, geological modeling, reservoir management, and directional drilling. To determine reservoir lithology, the neutron-density cross-plot method is often used. This method requires end point matrix densities. The most commonly used "standard" values of end point matrix densities are 2.71 g/cm3 for limestone, 2.87 g/cm3 for dolomite, and 2.98 g/cm3 for anhydrite. However, a review of literature indicates that the end point matrix densities are not consistent, particularly for dolomite rocks. Consequently, this study was initiated to determine the end point matrix densities for Arab-D limestone, dolomite, and anhydrite rocks.

Based on core analysis and geological description, 99 core plugs were selected from nine wells in the Abqaiq and Ghawar fields. For these samples, which cover a wide range of porosities and lithologies, the following tests were performed: porosity, plug and powder matrix density, XRD/FTIR mineralogy, elemental chemistry, and thin section petrography. The data were integrated and the following conclusions were made: The measured powder matrix density agrees with matrix densities calculated from XRD/FTIR data and was found to be higher than the measured plug matrix density, due to micro/isolated pores. The measured plug matrix density was therefore calibrated to the powder matrix density and the calibrated plug matrix densities were used in Arab-D log lithology processing. Comparing with "standard" matrix density values, use of Arab-D specific end point matrix densities yields higher log derived dolomite content, which agrees favorably with core geological description lithology.
Geomechanical Factors in the Successful Implementation of Barefoot Horizontal Completions Totaling 100,000 ft Long, Alpine Reservoir, Alaska
Authors: Ramos G. G. , Erwin M. D. , Enderlin M. B.
Published: December 2007

This is a case study of a successful, field-wide implementation of horizontal, barefoot completions in a moderately competent formation - the Alpine Reservoir in Western North Slope, Alaska, Figure 1. A barefoot completion is a borehole without tubular liners and no cemented support - the least costly but riskiest completion strategy. (In this paper, barefoot and unsupported mean the same and are used interchangeably.) The Alpine experience provides a successful example where the benefits of unsupported boreholes outweigh the risks of borehole failure. To date, this aggressive yet simple completion technique has an aggregate length of more than 160,000 ft, all unsupported.

Combined with good drilling practices, the success of barefoot horizontal wells in Alpine is also due to the following petrophysical and geomechanical factors: Consistent reservoir quality within the layerAbsence of shale-breaks in the producing zoneModerate strength in normal fault geotectonic settingLow variability of strengthLinearly elastic behaviorNon-severe, slight weakening when water-saturatedGood permeability retained under post-elastic strains
The Importance of Extended Leak-Off Test Data for Combatting Lost Circulation
Authors: Økland Dag , Gabrielsen Glenn K. , Gjerde Jørn , Koen Sinke , Williams Ernest L.
Published: December 2007

Lost circulation due to induced fracturing is a costly problem in the petroleum drilling industry. After a discussion of the processes of fracture initiation and propagation, this paper reports a case from the Norne field offshore Norway. A production well suffered lost circulation during drilling at a mud density significantly below what had been perceived as the local fracture gradient.

Striking similarities were found between the lost circulation incident and the results of an extended leak-off test that had been performed at the same depth in an offset appraisal well just months earlier. Both datasets indicated that the formation at the relevant depth had a lower-than-prognosed minimum in situ stress, but a high fracture initiation threshold. This additional barrier to lost circulation was irretrievably lost once a fracture had initiated and penetrated a certain distance away from the borehole.

Based on this understanding of the nature of the problem, and an updated set of operational constraints, the drilling operation progressed to the prognosed total depth of a well section that could otherwise have been lost. Future wells will be based on an updated set of pore pressure, collapse pressure, minimum stress and fracture pressure gradients that were established after the incident.

The case illustrates that the conventional methods of determining the pore pressure and fracture gradient may carry considerable uncertainty.
Microseismic Imaging of Fracture Behavior in Naturally Fractured Reservoirs
Authors: Urbancic T. I. , Maxwell S. C.
Published: December 2007

Microseismic monitoring has been used to image the growth behaviour of hydraulic fractures in the Barnett Shale, Texas1. The Barnett is a naturally fractured shale reservoir, which causes significant variability and complexity in fracture growth during well stimulation operations. Over the past two years, several Barnett treatments have been successfully imaged using microseismicity recorded in realtime during the stimulations. In this paper, we provide examples illustrating how realtime microseismic monitoring can be used to map the complexity and variability of slurry interaction with pre-existing fracture sets during the treatment. In one example, the dynamic spatial and temporal behaviour in microseismicity during a staged treatment procedure was used to vary the hydraulic fracture geometry. The observations described in this paper suggest that realtime microseismic recording and analysis can be used to map hydraulic fracture variability in naturally fractured reservoirs, evaluate the influence of pre-existing fractures on stimulations, and change stimulation procedures in response to observed hydraulic fracture variability.
A Novel Underbalanced Perforating Gun Deployment System Using Production Packer Technology Successfully Completes HP/HT Offshore Horizontal Well in a Single Trip
Authors: Beveridge Martin , Robb Thomas , Herron Steve
Published: December 2007

An innovative completion method was recently used to complete a well in the Skua oil field in the central area of the North Sea. The Skua field is part of the ETAP (Eastern Trough Area Project) and is borderline high-pressure/high-temperature (HP/HT) with a reservoir pressure of 9,350 psi and a reservoir temperature of 307 °F. The initial field development plan was to have one subsea well with a horizontal reservoir section of 2,000 ft to drain the prospect. Production would be tied back to a central processing platform.

The completion design for this well had to address several challenges. What method could be selected for sand control in the long horizontal sectionWhat equipment would maintain integrity in near HP/HT well conditionsWhat configuration would allow the completion to be run underbalanced without completion isolation devices.

Several completion options were reviewed. A new gun-deployment system based on production packer technology was chosen because it appeared to offer the best option for meeting all the well requirements. The system would also allow the tubing-conveyed perforating (TCP) guns to be recovered if they failed to fire or malfunction.

Orientated perforating guns were used to mitigate sand production. The gun system was deployed from a novel polished bore receptacle (PBR) and permanent packer system that allowed for retrieval of the guns should they fail to fire or malfunction after the packer had been set. The polished bore receptacle and hydraulically set permanent packer were designed with the guns hung off the seal assembly of the polished bore receptacle and the tailpipe run through the permanent packer to the TCP guns.

A significant feature of the hydraulically set packer-TCP gun deployment system is that it allows contingencies for recovery of the completion and TCP guns from the well in the event of a total or partial perforation misfire. This was a necessary requirement in view of the fact that a long perforation gun string was to be deployed in a high-temperature reservoir where there would be an increased risk of gun failure due to the ambient reservoir conditions.

The Skua well was completed with a fully cemented liner. The completion and TCP guns were run, and the well was successfully completed and perforated underbalanced (without an isolation device) in a single trip.
Unlocking the Potential from UKCS Low Deliverability Reservoirs
Authors: Cranfield Colin B , Naylor Peter
Published: December 2007

There are over 300 undeveloped discoveries on the UKCS, estimated to contain aggregate reserves of more than six billion barrels of oil equivalent. A comprehensive survey has identified that low well deliverability is a primary challenge to development of this resource.

Following literature reviews, a series of information-gathering meetings was conducted with both oil companies and service providers. Thirty-five undeveloped discoveries were examined in detail and the knowledge gained was used to design an interactive workshop. This paper summarises information from fourteen companies and identifies barriers associated with low deliverability reservoirs and corresponding solutions. The reserves associated with specific barriers and potential solutions are highlighted.

Undeveloped discoveries with a well deliverability barrier are typically low permeability, thin- or inter-bedded and with uncertain reservoir connectivity. The technical barriers are challenging, but many solutions exist to manage the risks and uncertainties. For example, better-targeted, long and/or multilateral well-bores, hydraulic fracturing, under-balanced drilling and non-damaging drilling and completion fluids all have potential to raise deliverability.

In other cases, solutions are being developed, such as improvements in modeling structurally complex reservoirs and advances in the areas of seismic resolution and prediction of reservoir performance from seismic data.

Non-technical solutions also have an important part to play. An example is where companies form an alliance to strengthen their technical capability and generate a sufficient resource target in an area such as under-balanced drilling. The study found that the drive towards low cost can often be at the expense of adding value. Service providers frequently found that even within the same company, buyers and users have different objectives. Buyers are driven by ‘cost’, whereas users should be driven by ‘value’. There needs to be a shift towards value-based procurement practices, with a re-appraisal of company objectives and internal performance measures. Similarly, more effective contracts are needed which recognise the impact of risk.

The stage is set for a new wave of activity on UKCS developed fields and undeveloped discoveries and a series of recommendations is made to help facilitate their development.
How Routine Reservoir Surveillance with Neural Networks and Simplified Reservoir Models can Convert Data into Information
Authors: de Jonge Gert J , Stundner Michael
Published: December 2007

Current levels of Reservoir Surveillance technology associated with intelligent well completions, such as fibre optics and permanent downhole gauges, create an increasing flow of data.

Conventional routine Reservoir Surveillance tools do not help the knowledge worker anymore to cope with high-frequency real-time data. Overloaded with data handling work, the knowledge worker in our industry is not capable to reveal the great potential inherent in this data.

A radical different work process and new applications of Data Mining technologies are presented to support the industry's next goal – The Smart Field.

A learning Data Mining approach is presented to detect discrepancies from expected trends and patterns. These trends and discrepancies are then translated into business rules to enable the closed-loop control of oil and gas assets.

Lessons learned are presented and necessary future developments are identified.
The Economic Advantages of Managing Data, ONCE!
Authors: Smith Alan H
Published: December 2007

Most data collected by operators in the North Sea is moved from the contractor to the operator, copied for use within the operator and then copied again to partners. Some data is stored to meet regulatory requirements and/or delivered to the regulator. The consequence of this multifaceted life of the data is the same data is available in many locations with an ever-increasing probability of alteration and corruption as more and more people use it. The net result is a significant amount of avoidable time, and money, spent on copying and data quality control as the same data moves to and fro.

The estimated savings available in the UKCS from managing data ONCE! are of the order of £1.5 billion per annum, or about US$1 per barrel. Realizing these savings would enable vital increased recovery in the North Sea, and beyond.

Managing data ONCE! employs a set of principles, which, when applied will result in the realisation of these practical savings. The principles are: One time data managementNew ways of workingConsistent and correct dataEconomic and efficient

Usage of this principle set achieves value delivery to the operator, partners, and industry as a whole.

One time data management results in a New way of working that delivers Consistent and correct data. The Economic efficiencies achieved through reliable data being managed once, with secure storage and access availability, translate into significant cost savings!

Just as poor management of data can have a significant effect on the bottom line profitability. Placing a cost on managing data ONCE! and employing best practice data management is a key economic advantage.
Full Field Tertiary Gas Injection: A Case History Offshore Abu Dhabi
Authors: Bonnin E. , Levallois B. , Joffroy G.
Published: December 2007

In 1997, a full field non-miscible tertiary gas injection scheme was implemented offshore Abu Dhabi. The purpose of the project was to enhance the oil recovery of a mature carbonate reservoir, in a field located on the border between U.A.E. and Iran.

Analysis of the pilots and early stages of the full field development were extensively described by Stofferis1 and Nicolle2. The present paper focuses on the practical problems encountered and the solutions developed to tackle and efficiently manage this challenging project.

The observed reservoir response to tertiary gas injection is first described at the well level and the main macroscopic parameters controlling this response are presented. The impact of the constraints linked to the surface facilities is then introduced and the overall field gas management policy explained. Finally, almost halfway through the designed project life, a technical and economical assessment is also presented together with the future project extensions.
Nuclear Magnetic Resonance NMR, A Valuable Tool for Tar Detection in a Carbonate Formation of Abu Dhabi
Authors: Najia Walid , Shaban Mohammad , Gossa Hedhili , Ferraris Paolo , Vissapragada Badarinadh , Petricola Mario , Namboodri K. M. N.
Published: December 2007

During the geological history, water borne bacteria may react with oil and result in the formation of tar (synonymous of bitumen in this paper). The dynamics of the reservoir over its history may also leave some tar within the hydrocarbon zones. Tar occupies a portion of the pores and may plug partially or fully the pore throats, significantly affecting the fluid flow in the reservoir. Detection of tar is of high significance in the field development for understanding the recovery and effectiveness of water/gas injection.

Tar can be easily identified in the water zones using the resistivity response. In the oil zone, it is difficult to separate tar and hydrocarbons by using exclusively a resistivity log. NMR transverse T2 relaxation contains useful petrophysical and geological information. The T2 histogram is a function of both fluid properties and pore size distribution. Tar is almost solid and the hydrogen it contains relaxes very fast because of its strong binding forces. The shortened T2 in the presence of tar results in lower NMR porosity, compared to the conventional Density-Neutron porosity. The missing porosity from NMR along with other conventional logs and wireline formation tester can be reliably used in the evaluation of tar in the formation. The results can be quantified with confidence after calibrating with core results.

Two examples are presented from the carbonate formations of Abu Dhabi, in the Middle East, where tar evaluation was successfully performed using NMR, Density-Neutron and MDT data.
An Advanced Method of Determining Insitu Reservoir Stresses: Wireline Conveyed Micro-Fracturing
Authors: Carnegie A , Thomas M , Efnik MS , Hamawi M , Akbar M , Burton M
Published: December 2007

Interest is rapidly growing in obtaining reservoir geomechanical data such as insitu stresses and rock strengths, since it is now realized that they are important to a wide range of applications; from bore hole stability, through to well stimulation and reservoir management issues such as optimal placement of water injectors and oil producers. Reservoir stress magnitudes can be inferred by continuous logs, for example by sonic based measurements. But these must be calibrated to direct measurements of stress. At present the only reliable, accurate measurements of insitu stress come from micro-fracturing. Following an introduction to geo-mechanical effects on limestone reservoirs, the paper focuses on a micro-fracturing technique, based on the Modular Dynamics Tester, MDT*, which efficiently and economically yields high quality stress information. The theory and application of micro-fracturing with the MDT* will be illustrated by an example in which reliable estimates of stress magnitudes, and lower bounds of rock tensile strengths, were obtained in an onshore Abu Dhabi limestone reservoir. This is the first published example of any stress test which has been performed by micro-fracturing in a limestone reservoir. To allow an understanding of the feasibility of the technique in limestone reservoirs, current best practice guidelines for planning and running MDT* minifracs will be summarised. This will include recommendations on how the MDT* can be combined with sonic, imaging and caliper logs to gain other valuable stress related data, such as principle horizontal stress directions, and continuous depth vs stress profiles (minifrac can only give point wise data).
An Integrated Workflow to Account for Multi-Scale Fractures in Reservoir Simulation Models: Implementation and Benefits
Authors: Bourbiaux Bernard , Basquet Rémy , Cacas Marie-Christine , Daniel Jean-Marc , Sarda Sylvain
Published: December 2007

The recent years have seen the emergence of detailed field data acquisition and efficient modelling tools to characterize reservoirs and model their complex internal structure in a realistic way. This progress led to the detection of multi-scale fractures in most reservoirs, and enabled to interpret unexpected field production features such as early breakthroughs. Therefore, the availability of a workflow and an integrated modelling methodology becomes more and more crucial to take into account the geological information about fractures/faults into the reservoir dynamic simulation process for optimizing field productivity and reserves. This paper reviews and illustrates the overall methodology and the specifically-involved procedures and tools we have gradually built from the experience acquired in various fractured field case studies.

The main steps of this multidisciplinary approach include (a) the detection, geological analysis and modeling of multi-scale natural fracture network from seismic and well data, (b) its validation and calibration from dynamic field information such as well tests, (c) the choice of an equivalent simulation model applicable at reservoir scale, and its construction thanks to innovative flow up-scaling procedures applied to the realistic model provided by the geologist, (d) the implementation of predictive and numerically-efficient algorithms to represent the physics of flow transfers occurring both at local and large scale during multiphase field production.

Thanks to this consistent workflow, field simulation models remain interpretable in geological terms, which is helpful for subsequent model updating. Thus, specialists in geosciences and reservoir engineers can cooperate in a very effective way to improve the management of fractured reservoirs.
Well Delivery Limit: Two years' experience with a breakthrough drilling performance initiative
Authors: Al-Suwaidi Abdullah , Faure Alban , Mukhalalati Talal , Al Taweel Abdul Rahman , Bamajbour Abdul Rahman , Edwards Clement , Macklin Jonny
Published: December 2007

ADCO and NDC launched its Well Delivery Limit (WDL) initiative in May 2000 to deliver the step change in performance required to meet its business objectives of increasing production capacity and containing technical costs. In partnership with Shell's Drilling The Limit* philosophy, WDL's performance management system challenges the true value of ADCO's well delivery operations, as opposed to simply doing the same things in a faster and cheaper way. Two years into the initiative, WDL has been implemented on all ADCO rigs with great success and new ways of working have been created by breaking down the barriers between departments in addition to those between ADCO and its Contractors.

From an operational perspective, ADCO has reduced well construction time by more than 30% and reduced cost by 8%. In addition to this, substantial improvements in well quality and HSE performance have been achieved, demonstrating the positive impact that WDL has made on ADCO's entire business.

The successes to date have essentially been in the form of time and cost savings, but even more can be gained by applying of the process to the entire well lifecycle. In other words, now that ADCO have learned how to "drill the well right", focus has shifted to the higher-level objective of "drilling the right well right". This next step has already been implemented on new development projects where existing practices have been challenged to ensure that the overall field development objectives are met in an optimal manner.
"Cement Packer": An Innovative Technique to Recover Reserves Above Packer Without Re-completion
Authors: Susilo Yoliandri , Wibowo Wahju , Rich David
Published: December 2007

Reserves with marginal production potential are often by-passed during the early stages of reservoir development. Re-evaluations of well logging data has resulted in the discovery of potential reserves located above the production packer that were not previously considered in the initial completion strategy.

Conventional completion techniques required a workover to re-complete to these potential zones. However, due to marginal reserves or the presence of production from existing zones below the proposed re-completion (ex: a dual completion where the long string is still producing while short string is shut-in), a workover is not a good economic option to recover these zones. A novel technique of cement packer has been successfully developed in Offshore West Java (OWJ) field to re-complete these zones without pulling out the existing completion. Pressure isolation of potential zones is accomplished by placing cement in the tubing-casing annulus above the production packer. This cement then acts as a new production packer further up the wellbore. Conventional or oriented perforating is then used to complete the well in the new productive intervals.

The advantages of this technique are it is inexpensive (rigless), there is no need to wait for other tubing strings in the well to deplete to their economic limit before re-completing up-hole and –most importantly-access to and production from lower completion is not affected.

To date, a total of 9 wells have been reactivated using this technique to recover productive zones located above the production packer. The average cost was only 20-60% of conventional workovers and savings of up to US$ 800,000 have been achieved. These successful results have brought new opportunities for reactivating many more shut-in wells with by-passed reserves that are economically marginal.
A Mechanical Model of Shale Instability Problems Offshore Abu Dhabi
Authors: Yamamoto K. , Shioya Y. , Matsunaga T. , Kikuchi S. , Tantawi Ibrahim
Published: December 2007

Natures of Nahr Umr shale instability problems in Zakum field are studied in Geomechanical and chemical views. Literatures, past drilling data, wireline logging and well test data, and analysis of cuttings and cores are studied to define the cause of the problem and find the way to fix it.

By using the record of past drilling troubles, problems are likely in the highly deviated well, and relationship between drilling direction and trouble occurrence is not clear. It has obvious relationship with mud weight and chemicals, however the causality is not clear.

The Geomechanical model was set for the formation from the analyzed data, available literatures and measured data in the recently drilled well. Also, mechanical and chemical characteristics of the shale are examined with cuttings recovered from wells, and cores from past wells. Mineralogical test are mechanical strength measurements are performed for the samples. Observation and testing of the samples unveil the fact that the shale has severe anisotropic feature of the mechanical strength and physical feature such as permeability.

By integrating the facts and findings, the authors determine the failure mode as bedding plane failure caused by its anisotropic feature and pressure penetration. Counter measures are proposed based on the numerical studies of poro-elastic and discontinuous modeling.
Using Solid Expandable Tubulars for Openhole Water Shutoff
Authors: van Noort Roger , Rivenbark Mark , Jones Mike
Published: December 2007

In recent years, many operators in the oil and gas industry have moved to horizontal drilling, a process that has proven much easier than trying to move hydrocarbons into vertical wellbores. For the last several years, a major Middle East operator has been leveraging horizontal drilling technology to maximize oil recovery. Although horizontal drilling technology has resulted in significant production increases, this operator saw that recovery efforts were somewhat hampered by water breakthrough in the horizontal openhole section of some wells. Unwanted water production is a problem for many operators, not just because of water content and reduced lift efficiency, but also because of the cost of water handling facilities and the cost of disposing of or re-injecting the unwanted water.

This paper describes the planning and deployment of solid expandable tubular technology in the application mentioned above and cites an actual case history. This paper also discusses applications under development that leverage emerging solid expandable tubular technology.
Reconciling Core Derived Permeabilities and Well Test Using A Fracture Network: A Field Case Example
Authors: Charfeddine Mohsen , Al-Deeb Maged , El-Abd Salem , Bahar Asnul , Ates Harun , Soeriawinata Tono , Kelkar Mohan
Published: December 2007

It is a common observation that well test permeability values do not match with thickness weighted core permeability averages. This is not a surprise because of the differences in the measurement scales where, unlike well test measurements, core samples represent a very small portion of the reservoir around the well bore. In addition, the presence of fractures and/or high permeability channels will further enhance the difference between the two sources of data. Therefore, reservoir descriptions based on core measurements alone cannot honor well test results. They need to be modified properly without violating the underlying geological and geostatistical information.

In this paper, we present a methodology to properly enhance permeability fields that also accounts for fracture distribution in the reservoir. The basic idea is that radial upscaling around a wellbore within a given investigation radius should match the permeability obtained from well tests. The enhancement is caused by two factors: microfractures, which cannot be explicitly represented in the reservoir description, and macro-fractures, which can be interpreted using 3-D seismic data. To account for these two different types of fractures, we calculate two different enhancement factors, one for the base level (microfractures) and one for the higher level (macro-fractures). The base level, after appropriate interpolation, is applied across the entire reservoir, whereas the higher level is applied only to locations where macro-fractures are interpreted from 3-D seismic data.

The technique was successfully applied to a Middle Eastern carbonate reservoir. A significant correlation is observed between the enhancement required to match the well test data and the fracture density (macro-fractures obtained from 3-D seismic data) within a given investigation area. A correlation function is then obtained between the enhancement factor and the fracture density for a given grid block, which in turn is used to apply enhancement to interwell locations. Thus, the resulting permeability field did not only honor the well test results but also the fracture distribution and the underlying geological and geostatistical descriptions. In a later stage, a tensorial approach was used to upscale permeability to account for the anisotropy in permeability distribution. Using this approach, a proper anisotropy of permeability distribution, matching the fracture orientation, has been obtained.