bluuebunny/crossref_metadata_2025 huggingface dataset:
Injection Strategy and Best Practices for Managing Produced Water
Authors: Abou-Sayed A. , Zaki K.
Published: December 2007

Proposal

Hydrocarbon production is associated with the generation of waste and by-products. The safe disposal of produced water, a common by-product, is of prime concern in oilfield operations. Long thought of as an economical and environmental liability, Produced Water Re-Injection (PWRI) provides an unrivaled option that is beneficial on both fronts. The paper identifies the operation's associated opportunities and risks. Emphasis is placed on procedures and best practices compiled during a 10-year, joint industry project (JIP). The overall theme of the paper is injector performance.

PWRI is used in water flooding for the purpose of pressure maintenance and the possibility of Improved Oil Recovery (IOR). The design process must meet production requirements, assure conformance and sweep and achieve desired pressure maintenance. Additional considerations include meeting waste management requirements for disposal volumes and reducing waste. These constraints translate into injector performance metrics and sustained delivery of the injection rate/injectivity. The paper examines the options available for balancing CAPEX (treatment facility, pumping equipment, and well drilling and construction) and OPEX (filtration, chemical, and biological treatment, stimulation and voidage replacement) to ensure long term injectivity maintenance.

Addressed are selection criteria for well completion, injection and thermal treatment. Issues such as vertical vs. horizontal wells, matrix vs. fractured or cool vs. hot water injection are tackled. Investigated are the damage mechanism and their effect on extended injection. Identification of the damage cause is paramount in guiding the design of an effective stimulation treatment or intervention. The optimal injection design provides the equilibrium between how to mitigate (selection of appropriate water quality) and when to remediate (plan effective stimulation) damage. Several field examples are included to support the conclusion and recommended best practices discussed in the paper.

Monitoring is an essential task during injection. The primary product of which is large amounts of raw data. The paper investigates the use of non-deterministic models and data mining techniques in ascertaining the physical correlations and observations from the data. A field case from the North Sea illustrates this application.
Permeability Estimation From Stoneley Amplitude, Corrected for Borehole Geometry and Rugosity
Authors: Canady W. , Spooner P. , Vasquez R.
Published: December 2007

Theoretical research and field studies conducted over the past 20 years have demonstrated that the acoustic Stoneley-wave is strongly influenced by formation permeability. However, due to the many nonpermeability-related petrophysical parameters that affect Stoneley properties, the development of a practical Stoneley-to-permeability relationship has met with only limited success to date. Existing commercial techniques commonly compute useful, and often accurate, qualitative estimates of Stoneley permeability but are unable to make accurate quantitative measurements of formation permeability because of the complex acoustic nature of the mixture of pore fluids, the acoustic effects of drilling-induced damage to the sensed volume, and to other non-Biot mechanisms yet to be understood.

Current Stoneley-based permeability products use Stoneley amplitude, frequency, attenuation and phase attributes, by means of a comprehensive acoustic model or by forward modeling techniques, to identify and quantify the nonpermeability effects. However, the sophistication required by these methods, in terms of computing resources and expertise, makes them generally unavailable as workaday tools for the petrophysicst.

This paper presents an alternative approach designed for routine use by an analyst or petrophysicst. A simple empirical model of Stoneley-derived permeability is calibrated against a measured standard. To a limited degreee, this method also accounts for borehole rugosity (washouts), variations in borehole size, and for permeability estimation.
New Operational Technique Improves HSE in Offshore Acidising Operations
Authors: Sinanan B. , Rae P.
Published: December 2007

The world consumption of hydrocarbons is projected to increase by some fifty percent in the next twenty years. Yet, many of the countries supplying the world's insatiable demand will, themselves, become net oil and gas importers in the very near future. It becomes ever more important, therefore, to maximize the productivity of each and every well. While many new wells benefit from improved drilling and completion practices, there are a significant number of mature wells that are still capable of producing at economic rates, if properly stimulated. One of the simplest and most cost effective methods to do this is by matrix acidising.

Acidising has established itself as an indispensable technique for enhancing production from hydrocarbon reservoirs worldwide. Over the years, research scientists and engineers have developed and improved many chemicals and additives to enhance the efficiency of these acid systems, as well as reduce the health, safety and environmental impact they have on operations. Despite huge improvements in the last decade, many issues and concerns still exist today. Handling, mixing, storage, pumping and disposal of acid and acid additives remain critical concerns in the industry.

In response to these concerns, new operational methods using specialized equipment, improved mixing techniques and new acid systems have been developed. This paper discusses the current practice, reviews its shortcomings and introduces these improved methods for enhancing HSE practices and optimizing operational efficiency in offshore operations.

Finally, actual implementation of the technique in various offshore scenarios is discussed, describing the HSE and logistical advantages of the process, as well as the resulting synergies.
NMR and Capture Spectroscopy Help Resolve Producibility and Fluid Distribution in the North Alwyn Triassic
Authors: Longis C. , Vignau S. , White J.
Published: December 2007

Hydrocarbon is found in both Jurassic and Triassic sandstones in the Total Alwyn North field, but the Triassic reservoir has historically attracted little attention as the production effort focused on the prolific Jurassic sands that lie above. As the larger reservoir is coming off plateau production, increasing attention is being paid to the Triassic where significant reserves remain.

Productivity of the complex Triassic formation is far less predictable than the Jurassic, and new techniques are being developed to better understand the production behavior. Part of this process is gathering data on the rock and fluid using new measurement technologies. On two recent wells (N46 and N47) the Triassic logging programs included a CMR Combined Magnetic Resonance log and ECS Elemental Capture Spectroscopy measurement. These two measurements are quite complimentary, as the CMR looks only at the fluid and the ECS looks purely at the lithology. Such focused measurements help simplify the interpretation in this complex formation.

The CMR was run primarily for porosity and permeability, which can be difficult to measure in the Triassic using standard density/neutron logs. In addition, some MRF (Magnetic Resonance Fluid characterization) T2-Diffusion stations were acquired, which were very effective in separating out the reservoir hydrocarbon from oil filtrate, water and any other fluids that may be present.

In N46 this was particularly useful as the alternative of formation sampling with a formation tester was not always an option. This is because much of the Triassic is too tight to get any samples with a formation tester within a reasonable time. Now a combination of MDT and MRF can effectively appraise the fluid type and distribution within these long reservoir intervals.

The ECS was run to address the lateral variations of reservoir quality that is a particular feature of the Triassic depositional environment, and understanding the reservoir quality ideally before setting casing would be a major objective of any operator. This sensor directly measures the elemental concentrations of Iron, Calcium and Silicon (among others) that indicate the volume of clays, carbonates and clastics present. Measurements of clay type and volume, along with any carbonate cement are useful indicators of reservoir quality, and could assist in the design of any stimulation job that was planned. Comparison of core XRD data with the ECS on N46 shows a good match, allowing the confident use of ECS on future uncored wells.

The contribution of CMR-MRF and ECS to the understanding of the North Alwyn field is reviewed in this paper. The applications discussed here should also be helpful in other fields, both new and old, with the potential of extending the life of many assets currently in the post-plateau stage of production.
Reservoir Management in a Deepwater Subsea Field – The Schiehallion Experience
Authors: Govan A. , Primmer T. , Douglas C. , Moodie N. , Davies M. , Nieuwland F.
Published: December 2007

The Schiehallion field has experienced many reservoir management challenges since first production in 1998. Dynamic data such as RFT's, pressure transient analysis, interference testing, tracer analysis and 4D seismic need to be interpreted with great care - Schiehallion has examples where the data has been invaluable, and others where the data is ambiguous or misleading. It is essential to integrate several data types in order to obtain reliable conclusions. The paper describes some of the highlights and pitfalls experienced in Schiehallion.
A Methodology To Quantify the Impact of Uncertainties in the History Matching Process and in the Production Forecast
Authors: Maschio C. , Schiozer D. J. , Moura Filho M. A. B.
Published: December 2007

Proposal

Traditional history matching provides a unique deterministic reservoir model. However, it is well known that history matching is a complex inverse problem that can have multiple solutions. Therefore, a unique model is not sufficient to guarantee reliable production forecasting. This work presents a quantitative analysis of the uncertainties of the reservoir attributes integrated to the history matching process. Instead of use a set of deterministic attributes and changes them to adjust to the observed data, as in conventional way, a probabilistic analysis is incorporated. In this methodology, probability density functions are discretized in given number of levels. Comparing models response (simulation data) with observed data, there is a reduction of the probabilities of the scenarios that do not present a good match; some models can be discarded during the process. The major difficulty in this process is to determine how to redistribute the occurrence probability of the attributes of the remaining models. In this paper, a criterion to make the rearrangement of the probabilities is established. The main objective of the paper is to present a consistent methodology to integrate history matching and the impact of uncertainties in the production forecasting.

Firstly, the methodology is validated with synthetic cases derived from Tenth Comparative Solution Project (SPE 10, Model 2). Then, the proposed methodology is applied to a real case from an offshore field. In the two applications, the conventional history matching process is also applied in order to compare the results and evaluate the reliability of a unique model prediction against a set of most probable models predictions.

The main contribution of this work is to increase the reliability of prediction through reservoir simulation models and to show the necessity of incorporating uncertainties in the history matching.
A Laboratory Study With Field Data of Downhole Gas Separators
Authors: McCoy J. N. , Podio A. L. , Lisigurski O. , Patterson J. , Rowlan L.
Published: December 2007

Downhole gas separators are often the most inefficient part of a sucker rod pump system. This paper presents laboratory data on the performance of five different gas separator designs. Only continuous flow was studied. Field data is presented on two of the designs. The field data indicates that success or failure of the gas separator is dependent upon the fluids and wellbore pressures as well as the mechanical design of the gas separator. Successful and unsuccessful examples of gas separator performance in the field are shown along with field fluid data properties.
Profiling the Wall-Cake Characteristic of the Wellbore for Optimal Comparison of Logging-While-Drilling and Wireline-Bulk-Density Measurements
Authors: Terry B. , Lindsay G. , Elliot R. , Jebutu S.
Published: December 2007

The comparison of Logging-While-Drilling (LWD) and Wireline (WL) measurements is an ongoing challenge in Formation evaluation quarters. The differences are more often due to the dynamic changes that occur along the borehole wall and near wellbore formation environment, altering the measurement environment during the acquisition of both measurements. In conditions where these alterations are minimal, the LWD and Wireline usually have excellent agreement, while with increasing severity of the wellbore alterations, significant differences can occur between the LWD and Wireline.

This paper presents a methodology to profile the dynamic wallcake alterations by utilizing the variations in resistivity of the wallcake and near wellbore environment from time lapse logging-while-drilling and Wireline measurements. Traditionally such dynamic wellbore alterations are quantified with downhole mechanical calipers and ultrasonic acoustic caliper measurements, both of which measure variations in the physical dimensions of the wellbore diameter as a direct indication of wallcake and nearwellbore alterations.

Field examples are presented from wells drilled in the Columbus basin, Trinidad and Tobago. The near wellbore alterations are observed to show a strong correlation to the time-lapse resistivity ratios. Logging-while-drilling and Wireline-bulk-density measurements showed good agreement in the sections with minimal near wellbore alterations where the hole maintained near gauge conditions, while significant differences were observed in sections where severe alterations of the near wellbore has occurred and the hole had become under-gauged or over gauged. We also discuss some of the causal factors of the dynamic near wellbore alterations such as wall cake sleek along shale swells, filter cake buildup in permeable formations and hole washouts, and the implications for accurate petrophysical evaluation and reservoir description. The limitations of utilizing the time lapse resistivity method in profiling the near wellbore characteristics are also highlighted.
A new Integrated LWD platform delivers improved Drilling Efficiency, Well Placement, and Formation Evaluation services
Authors: Weller G. , El-Halawani T. , Tribe I. , Webb K. , Stoller C. , Galvin S. , Scot G.
Published: December 2007

Logging-while-drilling (LWD) services are today often provided by several separate tools that, when used in combination, result in some measurements being made far from the bit. Time to make up and break out LWD tools, memory dumping, as well as multiple tool reliability issues can significantly add to the well construction costs.

An innovative new LWD tool has been developed to simultaneously provide drilling-related measurements and an industry standard suite of formation evaluation measurements, equivalent to the classic "triple-combo" service, but co-located and closer to the bit, using only a single short collar. This means that less rathole is needed for logging, and fewer collar connections have to be made, resulting in a more efficient drilling operation. In addition, the co-location of the sensors reduces uncertainties in the interpretation of measurements that rely on multiple sensors.

A key focus during the development of the tool has been improvement in service delivery. This has been achieved through increased operational efficiency, higher rate of penetration (ROP) capability, significantly improved reliability throughout the system, and greater ease of maintenance. The use of a pulsed neutron source instead of a chemical source also dramatically reduces the environmental and operational risks normally encountered with the use of traditional LWD tools.

Pulsed neutron measurements delivered by this service include formation capture cross section (sigma) and elemental analysis from neutron capture spectroscopy. These new measurements are used to compute mineralogy while drilling. Azimuthal measurements are also available, allowing the formation and borehole to be imaged using a variety of properties. The result is a robust and complete interpretation with significantly reduced uncertainty, as well as a large choice of steering methods for effective well placement.

In this paper we describe the development of this new LWD service and show field-test examples of improved formation evaluation, increased drilling efficiency, and more effective well placement that the tool has provided.
Smoking Cessation Program in the Workplace
Authors: Custodio L. E. , Manlapaz P. S.
Published: December 2007

Introduction

Cigarette smoking is a significant risk factor for cardiovascular and other chronic diseases. Hospital or clinic based smoking cessation programs are scarce and inaccessible to workers working in the field. To encourage and assist employees to quit smoking and thus improve their health; and to make the program accessible, a smoking cessation program was conducted in the workplace.

Method

A survey was conducted to determine the number of smokers among Unocal employees and who were interested in joining the smoking cessation program. Enrollment to the program was on a voluntary basis. The program consisted of one-hour small group session/week for a total of 4 weeks. The program was conducted by the company's Health & Medical staff after proper training from hospital-based personnel conducting a similar program. The sessions focused on health effects of smoking, understanding and coping with urges/cravings; nutrition and fitness activities. Bupropion medications for a 4- week course were offered for free to employees who joined the program. To reinforce cessation efforts and to monitor the quit rate, monthly follow-ups were done either by telephone or group meetings.

Results

Based on the survey conducted, there were a total of 105 (32.5%) smokers out of 323 employees. Out of the 105 smokers, 22 (21%) were interested to join the program. However, only 12 (55%) actually joined and completed the program. Six (50%) employees successfully stopped smoking for 6 months while the other 6 employees (50%) initially stopped but relapsed. Four (4) out of twelve (12) employees who joined the program availed of the pharmacotherapy (Bupropion). However, the medication was discontinued by all three since they felt they could manage the withdrawal symptoms even without it. Problems encountered by employees who relapsed were peer pressure and withdrawal symptoms. All employees who joined were followed up regularly for 6 months.

Conclusion

The quit rate of UPI's smoking cessation program is comparable with reported quit rates from hospital or clinic- based programs or may even be better at 6 months period. This could be due to accessibility and better support system for the employees. Other local companies are encouraged to offer a similar program for their employees.
Cardio Vascular Health Program
Authors: Inciong E. A. , Clemena T. , Custodio L.
Published: December 2007

Introduction

To further assist in the improvement of our employees’ heart and health awareness, our Cardiovascular Disease Health Program was enhanced using the Heart Risk Assessment as a tool in educating and identifying contributing risk factors of the employees.

Method

All employees were invited to undergo Heart Risk Assessment using Framingham Heart Risk Scoring. The parameters used in this scoring are Gender, Age, BP, Smoking History, Total cholesterol and HDL and if in medication for hypertension. Results were discussed to employees individually. Those employees with moderate to high risk scores and those diagnosed with hypertension even with low risk score were monitored for six months. Health education, nutrition counseling, referrals to smoking cessation program and fitness program were done. Repeat Heart Risk Assessment was done to target employees only after six months.

Results

403 (96.4%) employees participated in the screening program with the following results: 339 (84.12%) employees with low risk scores; 46 (11.41%) employees with moderate risk and 18 (4.47%) employees with high risk scores. Based on the result, 132 employees were encouraged to enroll in the company's CVD Program. These were those employees with moderate (46 or 34.85%) and high risk (18 or 13.64%) heart risk assessment scores and those employees diagnosed with hypertension but with low risk (68 or 51.52%) scores.

All enrolled employees were monitored on the following parameter: BP, Lipid profile, weight and compliance to medication. Health education was provided to all. They were also encouraged to participate in the company's other wellness programs such as: DM Progran Fitness Program, Nutrition program and Smoking Cessation program.

104 (78.78%) out of 132 target employees have a repeat HRA after six months. The following were the findings: 55 (52.88%) employees with low risk scores, moderate risk 33 (31.73%), high risk 16 (15.38%). There were 9 (8.65%) employees who improved their HRA scores, 77 (74.03%) employees with the same score and 18 (17.31%) employees with higher risk score. The most common causes of the higher risk scores were smoking and elevated cholesterol levels.

Conclusion

Heart Risk Screening and the company's CVD Program were well participated by the employees. This could be due to heightened interest, health awareness of the employees and the enthusiasm of the Health and Medical Staff in promoting health. To improve employees’ health status, more efforts should be directed to encourage lifestyle modification and implementation of significant health programs.
Pioneering "Gate Valve Milling" Operation Performed With Coiled Tubing Recovers an Important Oil Producer Offshore Brunei
Authors: Al Araimi N. M. , Gedge B. , Burns K. , Mahajan M.
Published: December 2007

Brunei Shell Petroleum offshore well A was offline and shut in due to the 3 1/8" 5K lower master valve on the monoblock tree, being seized in the closed position, due to scale production. The subsequent loss of production was 200 m3 (1260 BOPD), with a monetary value of US$1.5 million per month at $40 per barrel.

Two options were considered for recovering the well using well intervention techniques rather than a complete workover and well killing operation. Mobilize a "Gate Valve Milling Machine" the nearest being available was in Europe.Mill the Gate Valve with a coiled tubing unit, which was already on the platform, performing a stimulation programme on adjoining wells.

Option one was expensive due to high mobilization costs, some HSE issues, well control but this was a tried and test method of remedying the problem. Option two was a somewhat untried operation, which had only been performed as far as BSP and the contractors involved knew, once before in the North Sea.

Given the coiled tubing unit was already on the platform, and the specialist low speed high torque motors with an anti stall device and specialist mills were availed in the time frame required. The decision process based on HSE, engineering review (SWOP), and cost considerations, chose the coiled tubing option.

The paper will examine the problem with the wellhead master valve, the HSE, engineering and cost decision process leading up to the decision to go with the coiled tubing option. The milling operation from programme inception to successful execution of the milling operation, and placing the well back on line, will review in detail.

Other operators will be able to benefit from this safe, low cost and time saving method of recovering production from wells with similar problems, which are many around the world.
Modeling Permeability Reduction Caused by Asphaltene Deposition
Authors: Garrouch A. A. , Al-Ruhaimani F. A.
Published: December 2007

This study formulates a model for estimating permeability impairment caused by asphaltene deposition. The model is based on a mass balance and is capable of predicting permeability reduction in either vertical or horizontal wells. The model accounts for both the effects of position in the reservoir and time. The model is formulated in integral form to allow for analytic solutions when symbolic formulation exists for the parameters affecting the deposition process. The modeling approache accounts implicitly for the effects of pressure, temperature, and fluid composition, by including the asphaltene radius distribution.

Even though the mass-balance model is one-dimensional and is valid for only single-phase flow in porous media, it can be used to estimate the permeability reduction for both homogeneous and heterogeneous formations.
Managing Life Extension in Aging Offshore Installations
Authors: Galbraith D. N. , Sharp J. V. , Terry E.
Published: December 2007

Many North Sea installations are now at or beyond their original design lives, and this raises questions about the demonstration of the safety of the structures to remain in service. Whereas most of the topsides equipment is accessible for inspection and maintenance, and deteriorating parts can be repaired and replaced, such IRM is extremely expensive for the underwater structure. Indeed, widespread inspection of structures cannot realistically be undertaken for both cost and safety reasons. The North Sea concerns on managing life extension affect both fixed platforms and semi-submersibles, and these are also reflected in many other parts of the world including the Gulf of Mexico and the Far East.

The management of life extension requires an assessment of both the original design requirements, changes in standards and loading conditions and the current state of the structure. ISO 19902 includes a new section on reassessment, which has been developed with international input (including the authors).

A methodology has been developed by Cranfield University, in conjunction with Galbraith Consulting and Sauf Consulting, to assess how well operators and their contractors apply their knowledge of individual structures, corporate requirements, behaviour of materials and worldwide experience in determining inspection and repair requirements for an individual structure.

The work was funded by the Norwegian Petroleum Safety Authority (PSA), as they needed a tool to provide a framework for their structural audits; however the methodology can be used by operators as a self assessment tool. An assessment determines the "maturity" of the operators’ decision making in a number of different areas — higher maturity requires greater understanding and investment in planning, but the resulting maintenance should be both cheaper and safer, particularly for life extension purposes.

The paper describes the main issues in managing life extension, including evolution and operation of the above methodology.
Moving From Wireline Logging to Logging-While-Drilling in an Aggressive North Sea Drilling and Formation Evaluation Program—A Case Study of the Brenda Accumulation
Authors: Dawber M. , Mitchell E. , Barson D.
Published: December 2007

LWD was integrated into an aggressive drilling program to assess the Brenda field from a previously un-appraised discovery in the Central North Sea. In a six well drilling program in 2004, shifting the logging program from wireline to LWD facilitated a rapid but detailed evaluation of the Brenda accumulation with considerable time and cost savings. Originally single, vertical wells with wireline were planned but practice evolved into drilling 3-legged directional wells using full LWD suites to maximize information garnered per well. Using LWD enabled logging suites to reach TD in directional wells on first attempt and meant logging in-gauge hole rather than the washed-out hole suffered by the wireline tools due to drilling reactive shales with water based mud.

Sophisticated LWD toolstrings including a formation pressure tester and a slow shear sonic tool were used in addition to the standard triple-combo (resistivity/density/neutron). Applying advanced data processing methods including phase velocity processing and a physics-based dispersion correction of the sonic as well as thin-bed processing of the resistivity facilitated quality control and quantitative use of the LWD data.

The LWD formation tester was used to estimate the oil gravity and to accurately identify the depths of the oil-water contacts. This was required to identify the main Brenda East and Brenda West stratigraphically-trapped accumulations and also for reserves estimates. Downhole fluid sampling was not necessary in these wells.

The LWD sonic measurements were used to refine the seismic models with accurate measurement of compressional and slow shear velocities in the overburden. This improved the top reservoir pick which is very important in a stratigraphic trap such as Brenda. The compressional and shear velocities measured in the reservoir were used to refine the acoustic impedance models. This meant that a costly VSP/Check shot survey was not required. This was fortunate because the only check shot survey that was run became stuck in the reactive formations above the reservoir.

Thin-bed modeling of the resistivity logs helped derive a more accurate reserves estimate by providing horizontal and vertical true resistivities in a series of thin-beds in the "abandonment facies" above the main reservoir. Thin-bed modeling effectively increased the resolution of the LWD resistivity tool.
The Logistics of International Technical Training
Authors: Hughes J. A.
Published: December 2007

As the technology of the industry continues to develop, there is often an urgency to transfer that technology from the developer to the end user. In order for the technology to be used properly and to its full potential, the end user needs tools such as documentation and training. Depending on the level of complexity, documentation alone is not enough, as users may be faced with volumes of technical information. Arguably, the best way to connect a user with his or her new technology is to offer hands-on, practical instruction. Such training requires a certain level of planning and effort when hosted within the same region. Taking the training on the road to other areas of the world presents extra logistical and cross-cultural challenges.

Recently, a new treatment monitoring system was introduced to the field in the USA, which required on-site training. When the same system was exported to operations in Russia, the logistics of personnel movement and busy work schedules demanded the training be hosted at a field base.

This paper discusses some of the considerations for planning and hosting a technical training course in an international location. Various topics are covered, from the logistics of getting equipment through foreign customs to the challenges of translating literature and presentations into another language. Based on the information in this paper, an instructor will be better able to plan and prepare a technical training course in a remote location. Details which are often overlooked and cause last minute crises are discussed, and priorities are assigned to certain tasks which require more time to plan for than others.
Tracing the Path of Carbon Dioxide From a Gas/Condensate Reservoir, Through an Amine Plant and Back Into a Subsurface Aquifer – Case Study: The Sleipner Area, Norwegian North Sea
Authors: Hansen H. , Eiken O. , Aasum T. O.
Published: December 2007

The Sleipner Vest Field, which came on stream in 1996, is the largest gas/condensate field in the Sleipner area. Having a higher carbon dioxide content (9 mole%) than the gas export quality specifications of 2.5 mole% CO2, it was necessary (prior to development approval) to find some way of handling the excess CO2 without damaging the natural environment. An amine plant was installed at the Sleipner T platform to extract the CO2 from the reservoir gas, which was then injected and stored some 800-1000m below sea level and 2.5 km east of the Sleipner A platform in the Utsira Formation - a water-filled acquifer. Up until now (mid 2005), about seven million tonnes of CO2 have been injected. The stored CO2 has been monitored using time lapse seismic to confirm its behaviour and evaluate (i) whether any of it has migrated towards the Sleipner installations, potentially leading to corrosion problems for well casing; or (ii) whether any of it has leaked into the overburden seal, the ocean or the atmosphere. The results show that neither of these eventualities has occurred.
Developing an Intervention, Maintenance, and Repair Strategy for Ormen Lange
Authors: Eriksen R. , Gustavsson F. , Anthonsen H.
Published: December 2007

Field development profitability is a function of many income and expense factors such as capital expenditures (CAPEX), operating expenditures (OPEX), production rate, product price, frequency of component failures and intervention vessel expenses. Component failures reduce the field total production rate and increase OPEX. The losses are directly drawn from the bottom line. Regardless of the chosen concept, the ability to efficiently keep production wells on stream is one of the most important factors determining field economic performance. A strategy on how to manage the Intervention, Maintenance and Repair (IMR) activities is therefore of utmost importance.

This paper describes the risk based approach used to develop the IMR strategy for the Ormen Lange field during FEED phase. The Ormen Lange field, the first deepwater discovery to be developed offshore Norway, is located 130 km from the West Coast of Norway at a depth of about 1000 meters. Developing Ormen Lange represents a major challenge with a combination of large water depth, extremely rough seabed conditions, long tie-back distance and demanding weather conditions. Fully developed the Ormen Lange production system potentially consists of 24 subsea wells and multiphase transport to an onshore terminal. This novel "Subsea to Land" concept was chosen in preference to a more traditional deepwater concept with an offshore processing facility with wet and dry wells (SPAR, TLP or SEMI) putting more emphasize on the management of reliability and maintainability of downhole, well and subsea equipment.

The paper illustrates how to estimate the cost associated with future unplanned interventions due to component failures (Risk Expenditures) - both direct intervention expenditures and the value of lost revenue - and how to assess the impact of different intervention strategies on overall life cycle economics. The link between high production volumes and intervention cost is quite straight forward - frequent and immediate interventions give high production volumes and evidently high intervention costs, while deferred/campaign interventions give lower intervention costs, and potentially lower production volumes. The challenge is to find the right balance. Findings regarding the effect of different interventions strategies, tooling and repair solutions are provided.

The benefits of the Ormen Lange approach are that improvement efforts are directed towards areas where the value yield is highest. It has put focus on critical equipment packages giving the highest contribution to Risk Expenditures, which subsequently has resulted in: »improved design/architecture to increase equipment reliability and/or»smarter and less expensive ways to fix the failed unit

The approach has also given a more transparent input to the budgeting process by providing an intervention cost breakdown on equipment level and a dynamic model to reflect the effect of improvement initiatives as the project moves forward.
Delivering a HIPPS Safety Critical Control System
Authors: Roberts P. , Phillips R.
Published: December 2007

Production pipelines from wellhead to initial processing or storage facilities are conventionally designed for the full wellhead shut-in pressure. However under normal operating conditions, the pipeline experiences a fraction of this pressure, sufficient to maintain product flow.

If a Pipeline Protection System is installed, the pressure rating of the downstream pipeline and associated equipment can be reduced significantly, which in turn lowers capital investment for overall project execution. High Integrity is required as the safety of the pipeline depends on the correct operation of the protection system.

Reduction of pressure rating by installing HIPPS could realise the following advantages:- Reduced cost of pipeline - can constitute a significant portion of field development cost (dependent on length, diameter, pressure rating, material type and installation costs).Reduced pressure rating of downstream equipment - risers, separators, process plant, etc.Could allow a new marginal field to tie in to existing lower pressure infrastructure.Could increase safety by ensuring reduced pressure levels - particularly for high pressure wells on manned facilities.Could be enabling technology for HPHT projects and some floating production systems using flexible risers.

This paper reflects on experience gained from work on various HIPPS studies, and delivery of two systems.
Field Test Results of the New Combinable Magnetic Resonance Autotune Logging Tool
Authors: Minh C. C. , Bordon E. , Hürlimann M. , Smithson T. , Kovats J. , Badry R. , Claverie M. , Haiyan Q. , Davenport M. , Rose H. , Womack G.
Published: December 2007

A new combinable magnetic resonance tool that automatically tunes and corrects the operating frequency for changes in the static magnetic field, Bo, has been developed. These changes can occur when metallic debris adheres to the tool's permanent magnet. The Bo field directly affects the Larmor frequency, which is required for the tool to generate correct porosity values. Traditionally, the Larmor frequency is determined during a Larmor frequency search task (LFST) prior to logging. The procedure during logging is to monitor changes in Bo (Delta Bo), and to perform a new LFST whenever Delta Bo exceeds a given threshold.

In many situations, such as deviated or deep-water wells, removal of metallic debris by ditch magnets is ineffective. Excessive debris causes the Bo field to drift, resulting in frequent tuning stops, which can add considerable rig time to the logging job. Tuning might even be impossible when heavy metallic debris prevents the tool from being tuned, resulting in non-productive rig time or total loss of nuclear magnetic resonance (NMR) data acquisition. Other difficult NMR tuning conditions include the following: ■Low measured signal amplitude when formation porosity is less than 5 p.u.■High bottomhole temperatures (above 135° C), where tuning stops expose the tool to long periods of high temperature.■Conductive muds, such as when the mud resistivity Rm is less than 0.05 Ω-m. In these cases, the high-gain-corrected noise amplitudes are similar to the LFST signal amplitudes.

Intuitive as it may seem, we demonstrate that the detuning information is contained in the echo itself. Theoretically, the shape of the echo is distorted if the tool is not operated at the Larmor frequency. The distortion can be quantified by measuring the phase difference between the two halves of the echo. Deviation from the Larmor frequency can then be monitored continuously and a feedback loop automatically adjusts the operating frequency. For optimal radio frequency (RF) transmission and echo reception, a second feedback loop maintains the resonance condition of the antenna. An additional feature of the new tool is the capability to acquire up to 16,000 echoes with wait time as long as 26 sec, thereby increasing the application range of complex fluid evaluation modes using diffusion editing (DE) pulse sequences.

Extensive testing has taken place in a wide range of environments in North America, Africa, the Middle East, and Asia. Examples presented in this paper illustrate rig-time savings, data acquisition in environments where acquisition was previously deemed impossible, and improved data quality because of the tool's ability to maintain a proper tuning. In addition, automatic tuning has simplified the new tool's data acquisition and log quality-control (LQC) procedures for field operations. New operating guidelines are included in the paper.
A Study of Fluid-Flow Mechanism for Cold Production With Sand and Single-Well Fine Numerical Simulation in Heavy-Oil Reservoirs
Authors: Wang Z. , Li S. , Yan C.
Published: December 2007

In order to study the fluid flow mechanism for cold heavy oil production with sand (CHOPS) and predict their production performance precisely, criteria for the skeleton sand erosion and movable sand startup have been set up, based on the stress analysis on formation rock and sand particulates. According to the principles of effective stress, mass conservation, virtual displacement, equivalent virtual work and so on, both the single-well-black-oil model of CHOPS with three dimensions and four phases and the equilibrium equation of borehole wall rock with elasto-plastic deformation have been established. Considering the basic definitions of physical property parameters and the effect on physical property parameters caused by bulk strain, skeleton sand erosion, movable sand deposition on the pore surfaces and movable sand bridge plug at pore throats, dynamic models of physical property parameters have been established for numerical simulation of CHOPS. Then, the coupling solutions of the model have been studied. Finally, a case to verify the correctness and validity of the model is simulated and analyzed. The establishment of the mathematic model describing the fluid flow mechanism of CHOPS is of great significance to help us recognize correctly and exploit heavy oil reservoirs efficiently.
A New Refracture-Candidate Diagnostic Test Determines Reservoir Properties and Identifies Existing Conductive or Damaged Fractures
Authors: Craig D. P. , Blasingame T. A.
Published: December 2007

A new refracture-candidate diagnostic test is presented that requires a brief injection at a pressure exceeding the fracture initiation and propagation pressure followed by an extended shut-in period with the pressure falloff recorded. Provided the time of injection is short relative to the reservoir response, the pressure falloff can be analyzed as a slug test by transforming and plotting the falloff data on a variable-storage, constant-rate drawdown type curve for a well producing from single or multiple finite- or infinite-conductivity vertical fractures in an infinite-acting reservoir. Characteristic variable storage behavior is used to diagnose a pre-existing fracture retaining residual width and to determine if a pre-existing fracture is damaged. Using the proposed model and analysis methodology, a quantitative type-curve/model match can be used to estimate reservoir properties.

In addidtion to the new fracture diagnostic solution, a new single-phase fracture-injection/falloff dimensionless pressure solution is also provided along with new pressure-transient solutions for a well producing from multiple arbitrarily-oriented finite- or infinite-conductivity fractures.
High-Performance, Water-Based Drilling Fluid Helps Achieve Early Oil with lower Capital Expenditure
Authors: Reynolds D. , Popplestone A. , Hodder M. , Gwynne P. , Kelly B.
Published: December 2007

The Forties field was discovered in 1970 and at its peak produced 500,000 bbl of oil per day (bopd). To re-start major drilling operations using oil-based drilling fluids on some of the field's old platforms would have required significant capital expenditure (CAPEX) to ensure total containment of both the fluid and cuttings. An alternative approach on three of the field's platforms has been successfully employed. The first utilisation in the North Sea of a high-performance, environmentally friendly, water-based drilling fluid has helped the operator achieve early oil with much lower CAPEX. It has also proved possible to drill side-track wells through the Eocene overburden and through the reservoir in one hole section. This was not previously considered possible - historically intermediate casing was set and the reservoir drilled with a smaller hole size. Expensive retrofitting of aging platforms to meet environmental obligations for total containment may be unnecessary when a high-performance, water-based fluid is utilised.

This paper describes the characteristics and field performance of this innovative drilling fluid system. Six wells have been drilled from three different platforms during 2004 and early 2005. This paper describes how the fluid performed drilling reactive formations that have only been successfully drilled in the past using oil-based muds. The paper presents a cost model of the alternative approaches to developing Forties using either oil-based muds with total containment or high-performance, water-based fluids with cuttings discharge. This paper will be of interest to Operator's of aging assets looking to continue drilling without heavy CAPEX investment for Total Containment.
Combining Slimhole Rotary-Steerable Technology With Real-Time Geosteering To Rejuvenate a Mature North Sea Field
Authors: Eaton G. , Blasdale T. , Heidenreich K.
Published: December 2007

More than 70% of the oil produced today comes from brownfield environments such as the North Sea. Increasingly complex geological targets demand a more sophisticated and reliable drilling system. The combination of a slimhole rotary steerable system (RSS) and a leading-edge geosteering solution can help operators optimize their well placement. In addition, a Web-based, real-time monitoring and data delivery system can produce the most accurate information possible for decision makers onshore. In this way, an integrated team can use modern logging-while-drilling (LWD) tools to make real- time well path corrections in a challenging environment.

This paper presents a case study in which real-time decisions placed a well successfully and also increased production levels greater than the estimates. The drilling system components responsible for the success were an advanced slimhole RSS,a leading-edge real-time formation evaluation tool, and a Web-based real-time monitoring and data delivery system.