bluuebunny/crossref_metadata_2025 huggingface dataset:
First Application of Underbalanced Drilling in Fractured Carbonate Formations of Iranian Oil fields Leads to Operational Success and Cost Savings
Authors: Hooshmandkoochi A. , Zaferanieh M. , Malekzadeh A.
Published: December 2007

Underbalanced drilling techniques (UBD) are evolving at a fast pace as oil companies learn how to use the technology to maximize well production and lower finding costs.

Although there was some air drilling through surface drilling activities in Iran for the past decade, the full package of UBD equipment and other UBD techniques were not introduced until National Iranian Oil Company (NIOC) supplied the package for a pilot project in southern Iran. The first well selected to be drilled UBD was GS 333, the reason for selecting that particular well was because the Gachsaran field is depleted and sever mud losses is experienced while conventional drilling, also, the UBD technique is expected to increase productivity of the well by decreasing formation damage resulted from drilling fluid losses.

The drill pipe injection technique was proposed to be utilized in this well because of its suitability for the well conditions where it is not expected to drill through the gas cap and the well will be completed in 8 ½" open hole.

This paper discusses the well design, UBD design parameters, Underbalanced modeling considerations and the lessons learned from this job which all led to the success of this project. It is also describe the process used to address HSE issues of the project in the face of the potential presence of H2S while drilling. The drilling and production results that were achieved were significant to the future operational potential and viability of this mature field. Of equal importance was the success of the operation from a health, safety and environmental (HSE) perspective in an environment in which the industry has been traditionally reluctant to use UBD techniques.
Mitigating Risks From Waste Subsurface Pressure Injection and Decline Analysis
Authors: Fragachán F. E. , Shokanov T. A. , Ovalle A. P. , Nolte K. G.
Published: December 2007

The progression of new field developments, including brownfield and deepwater, subsequently increases the volume of cuttings and production waste, and particularly produced water, considerably. The economical impact of missing drilling and production targets due to the failures in the drilling waste injection process represents high risks that demand sound engineering processes to ensure injection assurance.

This paper describes the solution and detailed pressure monitoring methodology implemented to maintain safe injection assurance via regular disposal fracture diagnostics. Timely identification and a thorough evaluation of non-ideal pressure signatures observed during injection and post shut-in periods provided critical information required to detect sub-surface anomalies. This can be an effective tool for the sub-surface risks identification and characterization.

The application of comprehensive fracture-mapping techniques is a major step in mitigating the environmental risks posed by waste. Waste mapping represents valuable information, not only in the overall planning of drilling operations, but in the fundamental and invaluable need to provide sound engineering for waste location and fracture containment assurance, thus minimizing environmental impact. Previous, oversimplified interpretations of multiple fracturing systems (or so-called uniform disposal domain) and new fracture initiation process are demonstrated to be in apparent conflict with fracture mechanics, stress calculations and the general principles of physics.

The authors also describe the results of pressure analysis conducted in a North Sea injection well, which simultaneously was used for production. The well was utilized successfully for Cuttings Re-Injection (CRI) and for the disposal of produced water. The success of the operation was a direct result of close monitoring of key injection parameters and in-depth analysis of injection pressure, despite risky geological conditions. Abnormal pressures increases and restrictions observed during injection were mitigated and addressed via a proper root-cause engineering and sound pressure diagnostic process. The drilling waste injection took place below a 13 3/8-in. casing shoe through the B annulus, in an open-hole section at the depth of 1220m TVD with a 240 deviation in the injection interval. The injection took place in close proximity to a major fault axis.
Qualifying a New Expandable Reservoir Completion System
Authors: Wood Pierre-Charles , Duhrkopf Don , Green Annabel
Published: December 2007

Over the past decade BP's primary sand control techniques have been dominated by Frac Packs in the Gulf of Mexico and Open Hole Gravel Packs (OHGP) and Stand Alone Screens (SAS) in the rest of the world.

In 2003, BP formed a collaboration agreement with Weatherford to develop a new Expandable Reservoir Completion (ERC) system. The collaboration aimed to develop a cost competitive high performance sand control system, which would provide open hole productivity with cased hole functionality in an 8 ½″ open hole.

The system would be run and expanded in a single trip to ensure efficient installation, an essential requirement in making the new system competitive with more established sand control technologies in high cost environments.

BP's Exploration and Production Technology Group (EPTG) together with several Business Units, supported the development of this new ERC System. Through the initial development phase from 2004 through 2006 a total of 5 installations (3 producers, 1 injector and one Stack up Test) have been completed to test the functionality of the completion equipment and associated expansion tools.

This paper will describe the development of the ERC system and review some of the most significant lessons learned during the qualification testing and field trial installations.

Careful documentation of all preparation and installation activities has been supplemented by focused data acquisition during installations. Recording high resolution borehole images and caliper data and critical downhole expansion parameters has allowed detailed post job analysis capability. Subsequent well performance data has also been used in evaluating completion durability and effectiveness.

The complications associated with combining single trip functionality with rotary expansion and the importance of the well trajectory with respect to downhole torque will also be discussed.

The data collected will show the new 7″ ERC system has to date provided comparable sand control and productivity / injectivity performance when compared to other well established sand control techniques.
High-Integrity Wellbore Surveys: Methods for Eliminating Gross Errors
Authors: Ekseth Roger , Torkildsen Torgeir , Brooks Andrew , Weston John , Nyrnes Erik , Wilson Harry , Kovalenko Kazimir
Published: December 2007

An earlier paper by the same authors, SPE 1037341, pointed out the potential safety and commercial costs of unreliable directional survey data. It described how a significant degree of reliability can be achieved with the application of quality control checks internal to the directional data, but it also identified the fact that such checks fall short of providing comprehensive reliability assurance.

This paper documents weaknesses in conventional directional survey quality control (QC) procedures through theoretical considerations, statistical analyses of real survey data, and real examples of failed surveys that have made it through conventional QC procedures without detection. The paper defines principles for survey programme design and implementation to eliminate these weaknesses. It proposes a new set of minimum requirements for survey validation, which, in general, incorporate the need for an overlapping verification survey or other independent observation. This requirement is not generally acknowledged in most of today's directional surveying QC procedures, which may be too weak to ensure the validity of a given error model and thus the integrity of the final well survey.

This paper also discusses how analysis of a sufficiently large quantity of data, with the recommended QC methods applied, allows validation and refinement of the error model.

This paper is the product of a collaborative work in the SPE Wellbore Positioning Technical Section (WPTS).
Aggressive Drilling Parameters Capitalize on Cutter Technology and PDC Frame Advancement in Mature Field
Authors: Langille Peter , Hildebrand Jason , Massie Kyle
Published: December 2007

The encroachment of PDC drilling upon previously roller cone dominated fields continues to occur at an ever-increasing rate. In many fields, the mere introduction of standard PDC technology can result in monumental improvements in performance. However, in southwest Washita County, Oklahoma the conversion to a PDC dominated drilling program has proven difficult utilizing standard PDC technology and operating procedures due to the shallow showing (5,000 – 6,000ft TVD) of the highly abrasive weathered granite conglomerate, known as the Granite Wash formation. Recently, the combination of new bit technology and operational practices has resulted in performance improvements allowing for a 41% reduction in drilling time.

In much of the surrounding Anadarko Basin, the interval to 11,000ft (where the Granite Wash is typically encountered), is dominated almost exclusively by PDC bits. However, as recently as nine months, many operators in the SW Canute area were forced to utilize a drilling program comprised solely of roller cones due to the shallow arrival of the Granite Wash and the inability of standard PDC technology and operating parameters to drill this formation. This paper will document how a major operator in the area utilized the concept of aggressive high WOB/low RPM drilling parameters, typically reserved for roller cone bits, coupled with innovative PDC bit frames designed to increase the load/cutter ratio, and new cutter technology to replace the typical 6–8 roller cones required to drill to 10,700ft with just two PDC's thereby realizing an approximate cost savings of $201,000.
Development Approach Appraisal: An Effective Way To Evaluate Employees' Performance
Authors: AbouHeif Moustafa
Published: December 2007

There are two prevalent approaches to performance appraisal; the traditional approach and the developmental approach.

The traditional approach is primarily concerned with the overall organization and is involved with past performance rather than being forward looking through the use of setting objectives or goals. It is usually tied to the employees' salary review. Dealing with salary generally overwhelmed and blocked creative, meaningful, or comprehensive consideration of performance goals.

The developmental approach to performance appraisal is more related to employees as individuals and it is forward looking through the use of goal setting. This approach is concerned with the use of performance appraisal as a contributor to employee motivation, development, and human resources planning. Besides its traditional purposes, the developmental approach performance appraisal has the following extra goals:

Provide employees with the opportunity to formally indicate the direction and level of their ambition; Show organizational interest in employee development, which was cited to help the enterprise retain ambitious, capable employees instead of losing the employees to competitors; Provide a structure for communications between employees and management to help clarify expectations of the employee by management and the employee; and Provide satisfaction and encouragement to the employee who is trying to perform well.

This paper presents our new approach towards performance appraisals - the Developmental Approach.

Shifting from the subjective - traditional - past performance evaluation, towards the objective -developmental - stretching performance evaluation was mandatory to the progress of our organization. Although this cultural change was not an easy task, the outcomes were very encouraging and positively reflecting at all our business aspects.
Pressure Transient Behavior of Horizontal and Slant Wells Intersecting a High-Permeability Layer
Authors: Gill Harmohan , Al-Zayer Rayed , Issaka Mohammed Ben
Published: December 2007

This paper describes numerical simulation studies designed to investigate the behavior of horizontal wells that intersect high permeability layers sandwiched between two lower permeability layers. The paper investigates the pressure transient behavior of 1) purely horizontal wells drilled in the middle layer and 2) slant horizontal wells that intersect all three layers, as the permeability of the high permeability layer is varied.

A previous paper1 focused on late time interference effects and radial composite behavior caused by a limited high permeability layer. This study focuses on the early time dual permeability effect and its impact on recognition of conventional horizontal well diagnostic derivative slopes.

The horizontal well simulations show a dual permeability effect as the contrast between the high permeability layer and the adjacent layers is increased. The vertical radial flow regime is seldom visible and masked by wellbore storage effects. Interestingly, what is observed however, is a plateau (or sometimes valley) caused by the dual permeability effect followed by a transition to horizontal radial flow regime. This may be explained as a combined effect of recharge and linear flow in the lower permeability layers. The plateau (or a valley) caused by the dual permeability effect, can easily be confused as representing the vertical radial regime. Similarly, the transitional data prior to horizontal radial flow, which includes the dual permeability effects, can be incorrectly analyzed and lead to misleading results.

This paper will demonstrate the increased complexity of the pressure transient behavior when the well is slanted through all layers while intersecting the high permeability layer.
Experimental Study of Hydraulic Fracturing in Sand as a Function of Stress and Fluid Rheology
Authors: de Pater C. J. , Dong Y.
Published: December 2007

We present an experimental and numerical study of the mechanism of hydraulic fracturing in unconsolidated rocks. We performed hydraulic fracturing experiments on loose sand samples under various confining pressures. We have developed a large biaxial set up in which cylindrical sand samples of dimensions 0.4×0.51 m can be tested under confining stress up to 40 MPa. We prepare a sand sample by pouring the sand into the sample vessel, which is filled with water to obtain a fully saturated sample. There is a borehole (injection system) with an open section in the middle of the vessel. The open section is closed during the sample preparation. After compacting the sample and applying the confining pressures, the injection system is opened and fluid is injected.

For modeling of the injection process we used a distinct element model in which we incorporated fluid flow that is coupled to the flow of the grains.

The injection tests resulted in either infiltration or generating fractures. Injecting viscous Newtonian fluid and cross-linked gel yielded in most cases only infiltration and wellbore expansion. Clear fractures were induced when injecting cross-linked gel with quartz flour and bentonite mud. Tests were run at a stress level between 0.2 and 20 MPa. At high confining stress we observed a strong tendency for shear fracturing during fracture initiation. The fracture initiation pressure was about 2.5-3.5 times the confining pressure. The stress level had a strong influence on the ratio of initiation pressure to confining stress. Also, it appeared that much higher pressures were obtained on dense sand samples, compared with less compacted sand.
Determination of Free Water Levels in Low-Permeability Chalk Reservoirs From Logged Saturations
Authors: Bech N. , Frykman P. , Vejbæk O. V.
Published: December 2007

The present paper describes a technique for determination of the free water level (FWL) in low-permeability chalk reservoirs along slanted or horizontal wells from logged saturations and porosities. The calculation is done by utilizing existing empirical correlations for drainage and imbibition capillary pressure curves. For each logged saturation and corresponding porosity the FWL is determined so that the calculated saturation equals the logged value. The method takes into account possible imbibition, which results in a FWL that is shallower than the original paleo FWL.

The method has been applied to field data from the North Sea and it is shown that it can capture a tilting water level along a horizontal well.
Application of Enhanced Ultrasonic Measurements for Cement and Casing Evaluation
Authors: Morris C. , Sabbagh L. , Wydrinski R. , Hupp J. , van Kuijk R. , Froelich B.
Published: December 2007

The hydraulic isolation of the wellbore casing and cement is critical for the completion of production and injection wells. Zonal isolation prevents the production of fluids from non-completion intervals, contamination of ground water by fluids in the wellbore, and allows conformance control of injected fluids. Current acoustic evaluation techniques may be limited by the acoustic properties of the material behind casing and by the inability to see beyond the cemented region near the casing. A new ultrasonic imaging tool has been developed to address these limitations.

The new imager tool combines the classical pulse-echo technique with a new ultrasonic technique that provides temporally compact echoes arising from propagation along the casing and also reflections at the cement-formation interface. Processing these signals yields unprecedented characterization of the cased-hole environment in terms of the nature and acoustic velocity of the material immediately behind casing, the position of the casing within the borehole, and the geometrical shape of the borehole.5

In order to provide answers to the casing/cement evaluation questions, a field study was performed to evaluate the results provided by both sonic and this new ultrasonic tool in the different cement materials, drilling fluids, and casing sizes. Field examples are presented to illustrate the actual response of the new ultrasonic tool to these various completion environments including wells cemented with conventional and lightweight cement. The results demonstrate enhanced cement evaluation for all cement types and a significant reduction in the uncertainty in making a squeeze or no-squeeze decision. The new cement evaluation tool implements both the traditional pulse-echo technique and the new flexural wave concept. The flexural mode enables deep imaging of the cement sheath up to the cement-formation interface. In addition, the measurement of the borehole geometrical shape makes it possible to evaluation double casing string conditions for potential damage.
Fracturing Previously Bypassed Highly Laminated Tight Gas Sands: A Production Optimization Case Study in South Texas
Authors: Fairhurst D. L. , Semmelbeck M. E. , Reynolds B. W. , Indriati S. , Lewis J. W. , Ellis A. C. , Deupree W. E. , von Plonski J. K.
Published: December 2007

Highly laminated tight gas sand sequences remain prolific targets worldwide and have often been bypassed using standard petrophysical analysis and simple porosity cut-off technique. The problem becomes more acute in marginal tight gas reservoirs. The high cost of hydraulic fracturing increases the need for an effective and useable petrophysical model for an accurate productivity indication of the target interval. The pressure to avoid non-economical completions continues to leave hydrocarbons bypassed. Using recent advances in logging technology and production optimization modeling, the thinly laminated gas bearing permeable sands can be discerned from clay dispersed in silt and sand. A true net height can now be obtained. Through production optimization modeling, it is possible to assess the economic viability of completing and stimulating highly laminated interval. In this paper, we will show a case study from a South Texas tight gas sand field. Several wells were evaluated using micro-resistivity imaging. From this an enhanced high-resolution petrophysical analysis was created. This image-enhanced evaluation of reservoir properties was combined with production modeling. The production performance was simulated for each interval and used for recommendations on completion strategies. Additional pay intervals, normally bypassed, were perforated and hydraulically stimulated. We compared production data from offset wells that used standard petrophysical analysis to the results of the newer wells with the high-resolution analysis. The results indicated that actual field production increased and paid out the increased fracture stimulation cost. Production logs acquired across entire intervals confirmed that portions of the field produced from horizons that were previously bypassed. This process is useful for any highly laminated tight gas sand sequence and is of widespread applicability. Previously bypassed intervals can now be assessed and completed effectively and economically. This process will further add to the reserve base of tight gas.
A New Technique to Determine Horizontal and Vertical Permeabilities from the Time-Delayed Response of a Vertical Interference Test
Authors: Sheng James J.
Published: December 2007

Vertical and horizontal permeabilities are important parameters for designing well completion and predicting well performance. In the past, to determine the permeabilities from a vertical interference test, some investigators proposed correlations or type curves based on simplified point source solutions. However, it is impossible for these correlations or type curves to cover the variety of scenarios found in the real world. In the recent years, people start to use regression analysis to match the responses at the source interval and the observation point. With regression analysis, we face the problem of non-unique solutions. Sometimes, an estimated permeability is outside a reasonable range when analyzing noisy data from real tests.

In a wireline vertical interference test, we perform a drawdown test followed by a buildup test. Because of the delay of response, the pressure at the observation probe continues to drop for some time during the buildup period at the source interval. The maximum pressure drop at the observation probe with regard to the maximum pressure drop in the source interval is time-delayed. Using this time delay and the maximum pressure drop at the observation probe, we developed a new technique to estimate vertical and horizontal permeabilities based on the line source solutions. We have also worked out a novel numerical scheme. The new technique is compared with the previous methods and shows its superiority in accuracy. In addition, our technique can be used in any situation with different test configurations. Application issues in real testing conditions are discussed. Finally, two field tests are analyzed using this technique. Previously, these tests could not be analyzed to determine vertical permeability using published methods because of the poor data quality.
A New Tool To Evaluate the Feasibility of Petroleum Exploration Projects Using a Combination of Deterministic and Probabilistic Methods
Authors: Siddiqui Mohammed , Al-Yateem Karam , Al-Thawadi Abdulla
Published: December 2007

In this paper we have presented a new tool to evaluate the feasibility of an exploration and production project. An exploration and production project can be evaluated for feasibility using deterministic methods or probabilistic methods. These two methods vary chiefly in the way they manage uncertainty in the input parameters of the decision model. Deterministic methods neglect the changes in the input parameters with time, but focus on estimating the probabilities of the different outcomes possible at each stage in the decision model. A classical tool of the deterministic method is the decision tree. Probabilistic methods assume that a quantity to be estimated (e.g. reserves) can never be accurately determined. Rather it presents the possible number as a distribution. A typical tool in decsion making using probablitics methods is the Monte Carlo simulation. Each of these two methods, probabalistic and deterministic have thier own advantages and limitations. Our paper discusses combining the benefits of decision trees and Monte Carlo simulation. The new tool combines the simplicity of the deterministic approach and yet takes care of uncertainty in the manner of the probabilistic method. The result obtained by the deterministic method is fed into the probabilistic model as in input. The probability function for each input parameter in the probabilistic method is defined. Other input constraints and limitations are imposed and the model is simulated. The resulting output is analyzed and the associated risk or uncertainty for each output parameter is quantified. The output of the probabilistic model is fed back into the decision tree and the optimum decision is determined. The overall uncertainty in each decision outcome is determined by combining the individual uncertainties. The various options available in the project execution are compared using the new tool and the best project is selected on the basis of the highest return on investment or lowest risk. The advantages of the new tool as compared to using only deterministic or probabilistic methods are also demonstrated.
Protecting Industrial Process Control, Automation, and SCADA Systems From Cyber Threats
Authors: Lowe J. , Lasky J. , Gilbert D. , Sheil K.
Published: December 2007

Industrial process control, automation and SCADA systems are at risk from cyber threats such as hackers, viruses and worms. These mission and safety critical systems are at risk because of the increased use of standard IT technologies such as Windows, TCP/IP, web technologies and wireless. These technologies have introduced security risks into the control and operations environments and need to be managed effectively.

Security incidents in control systems have increased significantly over recent years and hackers are starting to focus on these systems. A recent hacker conference focussed on attacking control systems and used such systems in a hacking competition. Such security incidents could have serious health, safety, environmental and reputation implications. These risks need to be effectively managed. This paper will provide an overview of the risks, summary of recent incident trends and guidance on how to manage these risks.

Organisations reliant on process control, automation and SCADA systems need to review the security protection of their systems and implement effective protection measures and response processes.

This paper highlights recent trends in industrial cyber security incidents oultlines an framework for organizations to manage these risks

These risks are relevant to all organisations which reply on industrial process control, automation and SCADA systems for the safe and reliable operation of their plant. The consequences of security incidents in these systems could have serious health, safety, environmental and reputation implications.
Solid Tubular Expansion in Horizontal Wells
Authors: Pervez T. , Seibi A. C. , Al-Hiddabi S. A. , Al-Jahwari F. K. , Qamar S. Z. , Marketz F.
Published: December 2007

The expansion process subjects a solid tubular to large plastic deformations leading to variations in tubular thickness and length, which may result in premature and unexpected failures under normal operations. Simulation work, laboratory tests, and field trials proved the viability of tubular expansion downhole and field engineers have gained enough knowledge in handling this process. However, tubular expansion in open hole of horizontal sections still presents another challenge to researchers and field engineers due to gravity and drag between the seal and the formation. The present work, therefore, presents simulation results of tubular expansion under various field conditions. In this study a typical tubular size of 57.15 mm outer diameter and 6.35 mm wall thickness is used with two different elastomer seals, 5 mm and 7 mm thick placed at equal spacing of 20 cm. It is found that the drawing force increases as the mandrel angle, expansion ratio, and friction coefficient increase. A typical expansion simulation showed that the drawing force required for expansion using a rotating mandrel is 15% less than that of non-rotating mandrel having same configuration. However, tubular thickness reduction is found to increase by 47% for a rotating mandrel as compared to a non-rotating one, which may affect the post-expansion tubular performance. The tubular wall thickness decreases as the mandrel angle, expansion ratio, and friction coefficient increase.
Detecting and Analysing Fractures in the Subsurface: The Critical Steps in Modeling Fractured Carbonate Reservoir
Authors: Elsaid Mohamed Elhami , Al-Jafri Ghassan M. , Mercado Gary , Sugawara Yuki
Published: December 2007

In Abu Dhabi Offshore areas, the development of Lower Cretaceous fractures carbonate reservoir is a challenge that can be achieved using fracture characterization modelling approach.

Generally, open fractures are part of the main factor controlling the permeability and connectivity of different reservoir flow units within the system; consequently the identification, description and classification of these fractures in such carbonates are essential to effective fracture modelling, formation evaluation, well placement and planning.

Identifying fracture network properties require all available data to be synthesized for such predictive modelling. The first step to establish a reliable predictive model of fractures is to collect the proper data in a consistent and systematic manner from core, image logs, outcrops, rock mechanics and dynamic data including mud losses, flow meter logs, well tests and production data such as gross rates, initial PI and water cut. Since image logs are usually limited in number, it is necessary to use open hole logs to extrapolate findings to wells with no image logs. One of the main steps in fractured reservoir characterization is to interpolate fracture attributes between wells using seismic data.

The next step is to identify the geologic controls (drivers) that have a great impact on the intensity and spatial distribution of fractures such as structure, thickness, lithology, composition and texture, faults and curvature. Nonlinear regression tools are used to rank and correlate the multitude of geological drivers. The selected drivers are used to predict the fracture intensity and generate field scale fracture attribute maps.

The final step in fractured reservoir modelling is to generate a discrete fracture network (DFN) model which determines the number of fractures in each grid block based on the value of the fractures intensity and to output the parameters to a reservoir simulator and compare the simulation results with known well behaviour and field production data.
Strain-Based Design of Tubulars for Extreme Service Wells
Authors: Nowinka J. , Kaiser T. , Lepper B.
Published: December 2007

This paper presents a framework for strain-based design of tubular strings in extreme-temperature or high-pressure high-temperature (HPHT) wells. The relevant concepts are illustrated by examples from analytical and experimental investigation of a casing material considered for use in thermally stimulated wells operated by Shell Canada Limited in Western Canada. Much of this framework is also relevant to other applications where deformation-driven loading mechanisms are present.

Strain-based design utilizes material capacity beyond its elastic range to overcome a number of economic and technical hurdles encountered in conventional load-based designs. It has been used successfully in field applications where plastic deformations occur, e.g. thermal wells and pipelines. However, current industry standards for material selection have their origins in load-based design. More sophisticated material characterization tools are required for strain-based designs, in which post-yield material properties govern much of the system response.

This paper describes application of strain-based concepts to design of casing strings under combined loading where some load components are deformation-controlled. The paper emphasizes the need to address strain localization, high-strain cyclic plastic loading, strain-rate-dependent strength, and associated stress relaxation effects.

Strain-based design is most effective if relevant and reliable post-yield material properties are available. Experimental investigation of a candidate material considered for Shell Canada's thermal wells consisted of a series of custom-designed coupon-scale tests. The tests were conducted to acquire data describing the post-yield material response to monotonic and cyclic loading at temperatures ranging from 20°C to 350°C.

Conclusions of this paper summarize findings of the executed material evaluation program, outline options to minimize strain localization impacts, and provide recommendations for strain-based designs of well completion tubulars. Following these recommendations should result in higher reliability and more cost effective wells in completion programs utilizing strain-based strategies for design of extreme service wells.
Self-Healing Cement—Novel Technology to Achieve Leak-Free Wells
Authors: Cavanagh P. , Johnson C. R. , LeRoy-Delage S. , DeBruijn G. , Cooper I. , Guillot D. , Bulte H. , Dargaud B.
Published: December 2007

There is a very large number of wells worldwide that leak or have sustained casing pressure (SCP). In Central Europe and the Middle East there are hundreds of wells with reports of trapped pressure that cannot be bled off. In the US and Canada there are thousands of wells leaking to surface, which may or may not be discharged to the atmosphere. Furthermore, 25% of all wells in the Gulf of Mexico have measurable sustained casing pressure. Additionally, remedial work fixing issues relating to cement failure has been estimated to be more than $50M a year in the US alone.

Throughout the lifecycle of a well, planned cycle or operational changes can contribute to unknown damage to the cement sheath integrity that is hard to identify or locate, including the generation of a microannulus. Within flow paths, hydrocarbons can either migrate to surface, or become trapped below the wellhead leading to pressure build-up. Typical events occur during cementing, while perforating or stimulating, throughout the subsequent production, and even after abandonment. These can easily create this loss of cement integrity.

This paper describes a novel isolation system that is activated only when a cement integrity problem occurs. The system will automatically and rapidly form a complete hydraulic barrier by swelling in the presence of hydrocarbon flow. Once activated, it will seal the damaged zone, and will even be able to be activated again, should further damage occur again during production or abandonment. The system has properties equivalent to conventional cement systems, and requires no modifications to standard surface equipment.

High pressure static and dynamic laboratory tests highlight the ability of the system to rapidly shut off gas flows within 30 minutes. Field tests have also highlighted the robustness of the system, with a number of wells currently using the system remaining leak-free.
More Ultradeepwater Drilling Problems
Authors: Shaughnessy John , Daugherty William , Graff Rick , Durkee Todd
Published: December 2007

A 1999 SPE/IADC paper (52782) identified and documented solutions to a number of drilling problems encountered in Ultra-deepwater drilling. Since that time the industry has pushed the water depth record beyond 10,000' of water and drilling depths below 32,000'. A number of new problems have occurred in the last 8 years that have been caused by mechanical failures (equipment stressed to its limits) or human error. In the Gulf of Mexico recent drilling has encountered problems drilling salt and tar that the industry had not previously experienced. Three operators active in deepwater GOM have collaborated on this paper to document problems under the assumption that understanding what can go wrong is the best way to avoid problems.
Adjoint-Based Well-Placement Optimization Under Production Constraints
Authors: Handels M. , Zandvliet M. J. , Brouwer D. R. , Jansen J. D.
Published: December 2007

Determining the optimal location of wells with the aid of an automated search algorithm can significantly increase a project's Net Present Value (NPV) as modeled in a reservoir simulator. This paper has two main contributions: first to determine the effect of production constraints on optimal well locations, and second to determine optimal well locations using a gradient-based optimization method. Our approach is based on the concept of surrounding the wells whose locations have to be optimized by so-called pseudo-wells. These pseudo-wells produce or inject at a very low rate, and thus have a negligible influence on the overall flow throughout the reservoir. The gradients of NPV over the lifespan of the reservoir with respect to flow rates in pseudo-wells are computed using an adjoint model. These are subsequently used to approximate ‘improving directions’, i.e. directions in which to move the wells to achieve an increased NPV, based on which improving well positions can be determined. The main advantage over previous approaches, such as finite difference or stochastic perturbation methods, is that the method computes improving directions for all wells in only one forward and one backward (adjoint) simulation. The process is repeated until no further improvements are obtained. The method is illustrated by two waterflooding examples. In the first the location of a single injector is optimized to maximize NPV. Starting from four different initial injector locations the algorithm converges to four similar local optima. The second example involves optimization of the locations of 9 producers and 4 injectors. Starting from two different initial well configurations we obtain nearly the same (local) optimum.
Further Development, Field Testing, and Application of the Wellbore Strengthening Technique for Drilling Operations
Authors: Fuh Giin-Fa , Beardmore Dave , Morita Nobuo
Published: December 2007

The currently popular concept and practice on "Wellbore Strengthening" for drilling applications was originated in part from our earlier SPE papers on "A New Approach to Preventing Lost Circulation While Drilling"1 and "Theory of Lost Circulation Pressure".2 Based on our theory and earlier test results, a significant increase in formation fracture resistance could be achieved due to fracture sealing or plugging mechanism induced by a particle "screen-out" effect resulting from the drilling fluid loaded with an adequate amount of narrowly-sized granular materials. We have shown in both our laboratory and field tests that such an increase in formation fracture resistance is particularly valuable in helping the following well operations: 1) drill through depleted zones without losing fluid even when a much higher mud weight (than the normal fracture gradient) is used; 2) strengthen the weaker formations that usually require additional casing strings for protection; 3) avoid lost circulation during cementing operations as the strengthening operation also improves the strength of the cement sheath; and 4) drill high-angle well sections with high mud weights that would normally not be possible due to low formation fracture gradients, etc.

We have recently conducted several Wellbore Strengthening treatments using a special type of lost circulation material, in terms of particle size range and loading density, for increased formation fracture resistance (or increased apparent fracture gradient) during normal drilling operations. A wide variety of wellbore problems encountered have been addressed by this technique. Using several field case examples, this paper will provide a review and discussion of the theory, potential, and limits of the wellbore strengthening technique. Lessons learned from our field treatments will also be discussed along with precautions for optimum drilling applications.
Floatation of 10¾-in. Liner—A Method Used to Reach Beyond 10 km
Authors: Eck-Olsen Johan , Haugom Rune , Løklingholm Geir , Sletten Håkon
Published: December 2007

The requirement to drill longer wells to reach reserves on the boundaries of the Statoil operated Gullfaks Field required new solutions and techniques. The planning of the 10 km+ long well A-32 C presented a challenge where floatation technology was required. The 4660 m (15285 ft) long 10 3/4" liner was successfully floated to section TD at 7721 m (25324 ft) on May 9th 2006.

The Gullfaks well A-32 C, named Gulltopp, is the longest well planned from an offshore installation with a planned TD at 10+ km. The simulation in the planning phase indicated it would be very difficult or impossible to run the 5 km 10 ¾" liner to TD with conventional methods due to drag and buckling. The floatation method was selected for the 10 ¾" liner to overcome drag and buckling problems. Simulation showed using floatation and running the liner fully evacuated with air, gave substantial reduction in torque and drag.

This solution required development of new equipment with special floats to withstand more than 360 bar (5200 psi) differential pressure. Snubbing slips were used to secure the liner during running. It took more than one year to plan and prepare this well. The paper describes the planning and obstacles met to achieve this challenging goal of drilling the Gullfaks well A-32 C – Gulltopp.
Coiled Tubing Re-Entry Whipstocks: The Next Evolutionary Step in Drilling Practices for Mature-Field Development
Authors: Garfield Garry , Mackenzie Gordon
Published: December 2007

Creating a sidetrack out of the main wellbore has become a more common oilfield drilling practice particularly in the revitalization of mature fields. In the past, re-entry applications have used a sidetrack philosophy governed by threaded tubular drilling conveyance; however, from the standpoint of a coiled tubing methodology, the practice of sidetracking a well may still be seen by some as being in its infancy with the practice not gaining real acceptance until the early to mid 1990s. It was a natural desire to be able to exploit the inherent advantages of coiled tubing and marry it to the practice of being able to perform a sidetrack. The main advantages for the operator community to utilize coiled tubing includes improved safety primarily from a pipe handling perspective, faster trip times, under-balanced capability, reduced operational footprint and environmental impact, and achieved economic returns. The paper will discuss in detail an overview of utilizing a whipstock system with the conveyance method of coiled tubing in order to create a casing / liner window. The overview will also discuss general practices, tool selection criteria, and provide case history demonstration of each. The case histories demonstrated will be representative of placement of the whipstock with both electric wireline and coiled tubing with actual window milling being performed with coiled tubing workover motors. The case histories will encompass monobore applications, through tubing re-entry environments, fluid operations, and under balanced nitrogen driven applications demonstrating how coiled tubing re-entry can economically rejuvenate mature fields.
Improvements in Operations Using a High Efficiency Jackup
Authors: Hart Gordon , Ramsing Allan
Published: December 2007

The paper presents the operational experiences gained in using a high efficiency ultra large jack up rig in operations offshore Norway for ConocoPhillips at the Ekofisk Field.

The rig features a new concept in cantilever skidding called x-y. It is also rigged with a quadruple derrick with dual standbuilding capability and space for casing racking.

The dual pipe handling, offline activity features have during recent drilling programmes saved as much as 25% to 30% on earlier offset wells drilled with more conventional units.

Contracts have been made according to which these rigs have been paid standard rates only, and recovery of the additional investment has been made possible by built-in incentive agreements.
A 200°C, 35,000-psi HP/HT MWD Tool: Development Program, Architecture, Mission Profile, and Prototype Testing Results to Date
Authors: Mayes J. C. , Boling B. E. , Mootoo D. M. , O'Keefe Meghan , Gwilliam W. J.
Published: December 2007

Military electronics and sensors with hermetic packages specified to 125°C have been the mainstay of the industry for many years. Oilfield service companies have long designed these components into downhole tools that operate in environments up to 175°C, but for significantly reduced periods of time. However, new development of hermetic military electronics has all but ceased, forced from the marketplace by less demanding, lower temperature consumer applications such as cell phones, portable computers, and personal data assistants (PDAs). Unfortunately, downhole tools designed with consumer electronics face substantially reduced life at higher temperatures. Therefore, oilfield service companies must employ innovative solutions and rigorous environmental qualification to ensure maximum reliability. At the same time the desire for additional services in ever more extreme environments is growing. This paper describes the development program, tool architecture, mission profile, and prototype testing results to date of a retrievable, reseatable measurement-while-drilling (MWD) tool specifically designed to operate at temperatures up to 200°C and pressures up to 35,000 psi.
Extreme Drilling Environment Forces Evolution of Rotary Steerable Systems and Rotary Steerable Bit Technology
Authors: Cox Bronwyn , Romo Louis , Champion Brett , Maung Osman , Card Kirk , Barton Steve
Published: December 2007

Wells drilled in the Tuscaloosa Trend located near Baton Rouge have long been recognized for the extreme nature of the High-Pressure / High-Temperature (HP/HT) operating environment and potential for well control problems1. The current focal point, however concerns drilling the highly abrasive formations contained within the intermediate and drilling liner sections to depths of ± 20,000-ft. These sections have been a major cause of bit, directional tool and drill string failures. The directional complexity of the wells has increased exponentially in recent years due to surface location constraints and reservoir compartmentalization. New drills are therefore primarily directional in order to penetrate multiple stacked targets, fault-out depletion; which would otherwise result in drilling differentials in excess of 13,000 pounds per square inch (psi) and adhere to regulatory constraints imposed upon building surface locations in certain areas.

Directional control in the intermediate hole section is challenging as it requires drilling through the abrasive and damaging Wilcox formation and still risks the wellbore drifting out of the target. However, below the intermediate section we encounter significant directional tool constraints as in situ temperatures range from 300-°F to 400-°F. Poor directional response, low penetration rates as well as increased motor failures due to stator deterioration have traditionally resulted in long and costly sections. The impact of conducting directional operations in the intermediate or drilling liner hole sections has resulted in an incremental spend of up to $3.0MM on some wells and a 30-day to 45-day delay in first production.

This paper focuses on the improvements which have been achieved over a 5-year period due to the implementation of Powered Rotary Steerable Systems (PRSS) coupled with Rotary Steerable Bit Technology. The step-change in performance has been evidenced by reduction in days per 10,000-ft (D/10K) drilled from 86-D/10K to 55-D/10K. The improved time to first production has been attributed to the systematic learning and the successes of several office based, well site and third party teams.