bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Drilling Performance in Troublesome Environment
Authors: Russell K. A. , Cockburn C. , MacLure R. , Crawford A. , Davison M. , Jolley S. J. , Kazi M. , Koster M. , McGrath B. 
Published: December 2007

Abstract
This paper describes an example of drilling hazard mitigation. It demonstrates how a completely fresh approach, involving geomechanical analysis, planning of a new revised well trajectory, and real-time well monitoring, can reduce non-productive time and cost, and mitigate against unplanned terminal events.
Recent drilling operations in a mature field in the North Sea were severely disrupted by wellbore deterioration, stuck pipe, and lost circulation incidents. A complex geological sequence of tilted fault blocks and partially depleted reservoir sands made well trajectory and wellbore stability planning difficult. After two unsuccessful sidetrack attempts, an integrated operator-contractor team performed a detailed audit of the drilling problems and built a geomechanical earth model to evaluate drilling hazards and develop strategies to mitigate any further wellbore instability. Well objectives were re-evaluated and a new approach to the drilling process was developed. The key was simplification of the well path. The operational solution featured management of drilling hazards through a real-time risk-mitigation process. Additional engineers at the wellsite managed drilling parameters, continuously monitored cavings, cuttings, and drill fluids, and analyzed drilling mechanics and logging while drilling (LWD) log data for indications of impending problems. A Web-based real-time data-transfer system was used to deliver data to the onshore drilling and subsurface teams. These methods, combined with advanced communication techniques, enabled tight control of drilling parameters and trajectory, and enhanced collaborative understanding within the multi-disiplinary team. The third sidetrack was completed without incident, within time, and under budget.
Seismic Scale Sand Injectites in the North Sea
Authors: Cheret T. , Carrillat A. 
Published: December 2007

Abstract
In recent years, there has been increased interest in sandstone injectite geological features in the North Sea. They are interpreted as post-depositional features, and are characterized by chaotically distributed, unconsolidated, remobilized sands mostly in the Paleocene and Eocene formations. Porosity, when, present is often high. On seismic sections, they appear as dykes crosscutting the surrounding reflectors and as sills with short lateral extent. Until recently, they have not been considered as potential targets for hydrocarbon production for several reasons: -In some cases, they were thought to be processing artifacts.-They are often difficult to image seismically as their thickness is considered beyond the resolution of conventional seismic data and there is generally a low acoustic impedance contrast between the sand and the overlying shale.-Because they have not been imaged on seismic data, they have often been neglected in favor of deeper targets.-They have often been considered drilling hazards, as they could be over-pressured.
In this paper, we review three case studies from three different areas in the North Sea: Area 1: Block G34_12 east of Kvitebjoern field, Area 2: Central North Sea, and Area 3: Grane field. In these three areas, we show sandstone injectite features, each having different seismic characteristics: for example, geometry, thickness, and acoustic impedance contrast. We demonstrate that in each case, the injectite can be imaged and visualized as a single object or geobody.
Miscible Gas Injection in Undersaturated Gas-Oil Systems
Authors: Hoier L. , Cheng N. , Whitson C. H. 
Published: December 2007

SummaryThis paper discusses miscible gas injection in reservoir fluid systems exhibiting compositional variation with depth characterized by an undersaturated "critical" transition from gas to oil, where all fluid properties exhibit a continuous variation with depth.In an undersaturated gas-oil fluid system all fluids throughout the reservoir are initially first-contact miscible with their neighboring fluids. This implies that full-pressure maintenance, gravity-stable updip gas injection will lead to miscible displacement throughout the reservoir, even for down-dip fluids which are not miscible with the injection gas. The pressure maintenance required is to avoid depletion below initial saturation pressure throughout the reservoir, i.e. maintaining a single-phase fluid system. Compositional reservoir simulation studies have been used to verify this behavior for one-dimensional (1D) flow.Similar results were originally suggested by Hoier and Whitson1. In this paper we study the same mechanism for non-ideal reservoir systems characterized by (1) partial pressure maintenance where reservoir pressures locally drop below initial saturation pressure and two phases form prior to injection gas arrival; and (2) two-dimensional (2D) flow in reservoirs with heterogeneities and strong layer-property contrasts. Both situations may have a negative impact on oil recovery compared with full-pressure maintenance and gravity-stable miscible displacement with expected near-100% recovery.1D and 2D compositional simulations are used based on the reservoir characteristics of a field with an undersaturated gas-oil fluid system – Smorbukk South Field, located in the Norwegian Sea. This field produces rich gas condensate and volatile oil through an undersaturated gas-oil transition from two main geological layers. We present five years of production history with pressure maintenance by gas injection.
REACH is Real: The Proposed Reach System and its Effect on a Service Company
Authors: Killaars Janine 
Published: December 2007

Abstract
Guided by the white paper, "Strategy for a Future Chemical Policy,1 in October 2003, the European Commission drafted a new regulatory framework for chemicals known as the Registration, Evaluation and Authorisation of Chemicals (REACH) policy.
REACH is an integrated system that requires all substances produced or imported in quantities above one ton per year to be registered in the European Union (EU). The adoption of REACH will divert the burden of proof for putting safe chemicals on the market from the public authorities to industry.
The formal REACH proposal is expected to be presented for legislation in December 2005. If adopted, an 11-year transition (phase in) period will be implemented in three stages, determined by production volume and chemical hazard. A new European Agency will act as the central point in the REACH system.
This paper describes the proposed REACH system and its potential impact on an oilfield service company, both as an importer and downstream user of chemicals. The following topics will be discussed: Effects of REACH on producers/importersEffects of REACH on downstream usersImpact assessment of the REACH regulation on a service company as a case study
Advancements in Electromagnetic Propagation Logging
Authors: Wharton Russell P. , Hazen Gary A. , Rau Rama N. , Best David L 
Published: December 2007

ABSTRACT
The basic theory upon which the microwave Electromagnetic Propagation Tool (EPT) has been founded is reviewed, and the measurement technique is discussed in terms of a functional block diagram. Two methods of interpreting the propagating wave's measured phase and attenuation are reviewed. Specific log examples which distinguish between hydrocarbon and water-bearing zones in several lithologies are presented.
Stochastic-Aided Design and Bayesian Updating: New Tools to Use Expert Knowledge in Quantitative Models That Incorporate Uncertainty
Authors: Galli Alain , Armstrong Margaret , Mattos Portella Ricardo Cunha , de Souza Olinto Gomes , Yokota Honorio Kouki 
Published: December 2007

AbstractIn this paper we propose to use a new stochastic methodology for constructing reservoirs models that combines ideas coming from the pilot point method and dual kriging. Using this approach, specialists can directly build models of surfaces that reflect their knowledge of the field and honour available well data and can be based on information like seismic that is generally available at that step. They can also incorporate a range of uncertainty on specific parts of the surface. As well as being flexible and easy to apply, this method provides a consistent framework for measuring the effect of additional information.The method has been tested on a Brazilian gas reservoir (that has modified for confidentiality reasons) where two wells had been drilled and two more were planned. In addition we used a Bayesian approach to incorporate geological ideas about the maximum and minimum extent of sand bodies. Production profiles were modelled using response surface analysis where the plateau length and the decline rate depend on parameters like the size of reserves and the average permeability but still have residual uncertainty. One of the key results obtained was the quantitative impact of drilling a new well on the reservoir. These are used as input in a companion paper in which real option and Bayesian methodology are combined to evaluate the economic value of drilling two wells, and to select the best development scenario.
Successful Implementation of Resurgent Relative Permeability Modifier (RPM) Technology in Well Treatments Requires Realistic Expectations
Authors: Kalfayan Leonard J. , Dawson Jeffery C. 
Published: December 2007

Abstract
Industry interest in relative permeability modifier (RPM) treatments for water control is revived. However, as in the past, a majority of the treatments are applied to wells with extremely high water cuts (95% and greater) – with the unrealistic expectation that use of such agents will substantially reduce percent water cut or even prevent (shut off) unwanted water flow altogether.
Recent field experience with newly-developed RPM-based treatments is leading to clearer definition of the proper applications necessary to overcome the existing barriers to success which include, but are not limited to, treatment penetration depth, treatment placement, formation permeability and wettability characteristics, pre- and post-treatment reservoir fluid flow mechanisms, and a history of skepticism.
With these aspects in mind, this paper points to the largely unrecognized economic benefits that can be realized through creative and strategic deployment of low-risk or risk-reducing RPM-based technologies in multi-well scenarios. Examples include oil and gas producer matrix treatments, especially in high permeability and clean sands.
A New Skin Factor Model for Gravel-Packed Completions
Authors: Furui K. , Zhu D. , Hill A. D. 
Published: December 2007

Abstract
Gravel packing is widely used in well completions to prevent sand production. An efficient gravel pack completion retains formation sand without creating significant additional pressure drop through the completion itself. To predict gravel-packed well performance, a completion model that calculates pressure drop for a gravel pack completion is necessary. In this paper, a theoretical turbulence skin factor model for cased-hole gravel-packed wells is presented that can be used to determine the effects of the gravel pack on well performance. The overall pressure drop through the gravel pack completion is divided into three parts; the pressure drop through the gravel between the casing and the screen, which is usually small and can be neglected; the pressure drop occurring through gravel in the perforation tunnels penetrating through the casing and cement and out into the formation; and the pressure drop outside the casing caused by flow converging to the perforations. This study is focused on the latter two pressure drops. Based on extensive 3D finite element simulation studies, the flow field in and around a gravel pack completion is approximated by a series of linear, radial, and hemispherical flow geometries, and the Forchheimer equation is then integrated along a simplified flowpath to obtain the pressure drop both inside and outside of the casing.
The FEM simulation results show that the flow geometry of a cased, perforated, and gravel packed well greatly depends on the ratio of the formation permeability to the permeability of the gravel in the perforation tunnels. As the perforation tunnel permeability approaches the formation permeability, the flow geometry near the perforation through the casing is no longer linear but spherical as if there is no perforation in the formation. As a result, the conventional model of flow in the gravel packed perforations may give inaccurate results under these conditions. The new skin factor model accounts for the transition from linear to spherical flow as a function of the ratio of the formation to perforation tunnel permeabilities. This model also includes permeability damage in a perforation tunnel that significantly increases rate dependent (turbulent) skin effects. We used the model to determine the gravel pack conditions needed to insure that gravel pack skin factor is low and to minimize the effects of turbulence in the gravel pack in high rate wells. Guidelines for gravel permeability are presented based on these results.
The Effect of Cementation on Static and Dynamic Properties in Jauf and Unayzah Formations at Saudi Arabia
Authors: Al-Tahini A. M. , Sondergeld C. H. , Rai C. S. 
Published: December 2007

Abstract
The variability in mechanical properties measured on sandstones from the Jauf and Unayzah formations in Saudi Arabia is observed to be dependent on cementation. Static and dynamic measurements from triaxial testing data, measured acoustic velocities, and examination of core in thin section were used to relate the detailed microstructure and cementation to differences between static and dynamic moduli. The differences between static and dynamic moduli have numerous origins and vary from formation to formation. Properly converting from dynamic (log based) to static moduli is crucial for proper well stimulation analysis and design.
Elastic moduli and velocities (compressional and shear) were measured on sixty-five plugs from five different wells encountered through Jauf and Unayzah formations. Simple models based on moduli-porosity relations failed to adequately explain our observations. We used thin section analysis to evaluate the influence of cementation on the static-dynamic moduli differences. Forty-seven samples were selected for thin section analysis and fifteen representative samples were point counted to characterize and quantify cementation.
Cements in these two formations have variable composition and habits; both affect the moduli and acoustic velocities. It is not sufficient to know that cements exist; it is also necessary to know where the cement occurs. Pure quartz overgrowths cement plays a major role in increasing the moduli and velocities while clay cement plays a minor role. Simple functions suffice to describe the effect of these cements on velocity and the difference between static and dynamic moduli. Effective quartz overgrowth index was defined to quantify the effect of different type of cements. The difference between the static and dynamic moduli is reduced to a value of 2% to 15% when effective quartz overgrowth index is in the range of 16% to 26%. On the other hand, the difference increases to about 80% when high clay cements are present and the percentage of quartz overgrowth index less than 2%. Understanding these often ignored microstructural contributions, helps to understand the variation in moduli and allows for the design of more effective hydraulic fracturing treatments in the Jauf and Unayzah formations.
Field Applications of Low Molecular-Weight Polymer Activated with an Organic Crosslinker for Water Conformance in South Mexico
Authors: Ortiz Polo Roger P. , Monroy Rafael Rodriguez , Toledo Nelson , Dalrymple E. Dwyann , Eoff Larry , Everett Don 
Published: December 2007

Abstract
One of the major challenges faced in the Mexico South region is water management. Water in the oil stream results in extra disposal costs, scale buildup, reduced oil production, and eventually well shut-in (with associated workover costs). Consequently, producing zones are often abandoned in an attempt to avoid water contact, even when the intervals still retain large volumes of recoverable hydrocarbons.
Although natural fractures have a positive effect on oil flow, they also include a negative water or gas flow caused by coning effects or conductive streaks between the producing hydrocarbon zone and intervals above or below. If these zones are water producers, they soon impact the productivity of the hydrocarbon zone. An additional problem must be addressed as well: early water breakthrough caused by edge water flowing through faults, natural fractures, etc. Depending on the desired objective, placement techniques vary. However, placement techniques generally can be divided into two types: those involving a workover rig and those that are rig-less.
This paper will discuss case histories from southern Mexico that have used a low molecular-weight polymer, activated with an organic crosslinker. The candidate selection process, general job designs, laboratory testing results, etc. performed for water-reduction treatments in this area will be presented. These cases include depleted, highly fractured reservoirs.
Petroelastic Modelling as Key Element of 4D History Matching: A Field Example
Authors: Falcone Gioia , Gosselin Olivier , Maire Flavien , Marrauld Jean , Zhakupov Mansur 
Published: December 2007

Abstract
4D (or time-lapse) seismic is sensitive to changes in reservoir pressure and saturation. It allows monitoring of a reservoir during production, helps define areas of unswept hydrocarbons, and aids planning of infill drilling or pressure support solutions.
By improving the reservoir model, 4D reservoir monitoring can improve the accuracy of reserves evaluation and help with the optimisation of reservoir management.
This paper describes the preliminary work carried out as part of an ongoing project on 4D reservoir monitoring. The ultimate aim of the project is to history match a field flow model using both production and 4D seismic data.
The proposed approach, based on the integration of a reliable petroelastic model (PEM) with a dynamic flow simulator, uses an iterative, gradient-based optimisation method to adjust the initial reservoir parameters.
This paper focuses on the assessment of the impact of petroelastic modelling within the framework of 4D quantitative history matching. It shows the results of the procedure that was followed to validate the PEM for the Girassol field in offshore Angola. It addresses the problems of scale usually encountered within a 4D workflow. It also illustrates the results of the sensitivity analysis carried out on the acoustic properties predicted by the PEM when applied to the dynamic flow simulator.
In view of the application of the full 4D history matching loop to the field example, possible ways of determining the acoustic parameters and the areas of the reservoir that are most sensitive to 4D effects were assessed and are presented herein.
This paper highlights the importance of deriving a reliable PEM when dealing with 4D reservoir monitoring and suggests a way forward for integration with computer-aided history matching processes using both production and seismic data.
Managing Maintenance Expenditures with an Integrated Decision Analysis and Portfolio Approach
Authors: Mitchell James C. 
Published: December 2007

Abstract
Energy corporations with large scale operations, like major pipeline systems, refineries and oil fields are faced with high operating & maintenance costs in order to ensure reliable, safe operations. Often maintenance programs are justified by custom, safety or environmental hazard, or a requirement to comply with a current code.
The challenge is to be able to control spending on operations and maintenance while maintaining reliable and safe operations that meet regulatory codes and environmental standards. We advocate an integrated decision management and portfolio approach to analyze the risks of reducing or discontinuing a practice, or conversely, increasing maintenance spending where necessary.
With a traditional approach it is difficult for management to manage costs when risks are not quantified, often overstated or are not known.
Our approach integrates elements of decision analysis and portfolio preference. By developing a simplified model that captures the key areas of risk and benefits each maintenance element is assessed on a consistent basis. Using a portfolio approach to roll-up the program it is easy to identify the most productive projects as well as the projects that should be modified, delayed or dropped. The method also identifies underfunding e.g. where there are higher risks than the corporate risk tolerance allows.
The application of the process within a large transcontinental pipeline system resulted in an initial savings of 20% and ongoing savings of 50% from the original baseline that translated into hundreds of millions of dollars of sustained value.
Geared Turbodrilling Applications and Case Histories in the North Sea
Authors: Seale R. , Beaton T. , Strang G. , Salomons G. , Van Den Bos M. 
Published: December 2007

Abstract
In the late 1800s, the drilling industry recognized the inherent benefits promised by downhole drive systems. Turbodrills, and later, positive displacement motors (PDMs), were introduced to capitalize on these benefits. Both Turbodrills and PDMs convert hydraulic energy in the drilling fluid into mechanical power at the bit. With a Turbodrill, this power conversion is accomplished through the use of turbine blades, and with a PDM, it is accomplished through a seal between an eccentrically rotating steel rotor and an elastomer stator. While there are many benefits to the use of turbine blades to create mechanical power from hydraulic power, their superior efficiency at relatively high output speeds stands out. The rotational speed generated at the bit is not ideal for certain applications, however. The industry recognized this situation in the 1920s, and the development of the geared Turbodrill was initiated. By including reduction gearing in a Turbodrill, high rotating speeds generated by the turbine can be converted into lower RPM and higher torque at the bit.
For decades, there have been attempts to develop a successful geared Turbodrill. Until recently, these efforts have realized little success. Design work performed with the latest software technology and modern materials have now resulted in a very successful, high power, high torque geared Turbodrill. With the new possibility of decreasing output RPM, and increasing the available torque, the range of applications in which Turbodrills perform favorably is significantly expanded. The focus of this paper will be to identify applications in which the deployment of a gear reduced Turbodrill will be advantageous.
This paper will also analyze three recent North Sea case histories, in which geared Turbodrills, together with PDC bits, were run successfully to drill a 12-1/4" hole section through the upper Cretaceous chalk down to the upper Permian Zechstein formation. One of these cases involved running the new geared Turbodrill (NGT) with a rotary steerable system. Analysis of these runs will detail proposed versus actual drilling curves including an in-depth discussion on all parameters encountered during drilling.