bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Strength of Reservoir Materials: Key Information for Sand Prediction
Authors: Zhang Jiaxiang , Rai Chandra S. , Sondergeld Carl H. 
Published: December 2007

Abstract
The mechanical strength of a reservoir formation is the most crucial information required for predicting sand production and recommending sand control completion. The only reliable technique, so far, to obtain the formation strength quantitatively is to perform laboratory tests on core samples. The laboratory tests require substantial volumes of cores which, in most cases, are not available. In this study, we present a new method to avoid this restriction. The significance of this approach is its simplicity and efficiency in constructing a reliable mechanical failure envelope. The key results of this study, based on measurements on a variety of sandstones, are:
Sandstone formations are characterized by a single normalized failure envelope. This universal curve makes it possible to construct the failure envelope for a sandstone formation from the knowledge of critical pressure. There exists a correlation between the critical pressure and the compressional wave velocity (at equivalent depth of burial). The failure envelope for a sandstone formation can then be constructed simply from compressional wave velocities. These velocities are generally accessible from conventional logging data.
P. 291
Three-Dimensional Stress Analysis of a Wellbore With Perforations and a Fracture
Authors: Papanastasiou P. , Zervos A. 
Published: December 2007

Abstract
This study presents results of large scale 3-D elastic analysis of a wellbore with perforations. Both vertical and horizontal wellbores with perforations at different orientations are considered. The extra stresses imposed by a propped fracture at the unfractured perforations are also evaluated. A propped fracture results in increase of the compressive stress around the perforations which is higher in the perforations closer to the fracture and increases with propped width. The increase of compressive stress is much higher at the top/lower faces of perforations which is already less than the existing compressive stress at the lateral faces of the perforations. The results are also discussed in relation to the problem of hydraulic fracture initiation.
P. 347
The Skin Factor as a Rock Mechanics Diagnostic Tool
Authors: Santarelli F.J. , Tronvoll J.T. , Skomedal E. , Bratli R.K. 
Published: December 2007

Abstract
The paper presents a series of well tests performed on various North Sea weak reservoirs and will show how the skin factors measured can be interpreted in terms of sand production. In particular, the results presented show that sand production results in abnormally low skins independently of what the perforation conditions were in terms of under or over balance.
First, a series of tests were performed on injectors after a very limited amount of back production for clean up. Such tests were injection tests followed by clean up and a very good correlation existed between skin factor and under balance conditions. However, after important sand production, the wells were tested again under injection and all showed very low skin factors. Second a series of four production tests were performed on a well shot over balance and the evolution is clearly one of decreasing skin factor indicating sand production. Third, for a given field, all tests performed with a total draw down - i.e. draw down plus depletion - superior to 70 bars show an extremely low skin as the other show high skins. The balance conditions for such wells were very diverse. Fourth, it will be shown how on wells producing sand, the stimulation of the levels that produce sand leads to dramatic flow concentrations from very limited intervals and various PLT results will be presented.
The practical consequences of such results will then be presented and three essential aspects will be dealt with.
The perforation balance policy will be discussed in the light of the results presented above. The use of well test as a systematic mean to predict sand production will be outlined. Finally, it will be shown that test interpretation techniques ought to be refined to achieve a bigger understanding of the results in terms of description of the near wellbore area.
P. 375
Hydraulic Fracture-Initiation in Deviated or Horizontal Openhole Wellbores
Authors: Deeg Wolfgang E.J. 
Published: December 2007

Abstract
It is well known that a, hydraulic fracture preferentially extends in a plane perpendicular to the least principal in-situ formation stress. However, it is not generally recognized that in an openhole completion, the hydraulic fracture will only initiate perpendicular to the least principal formation stress if the well's axis is aligned with the preferred fracture plane throughout the treatment interval, If the well intersects the preferred fracture plane, a hydraulic fracture initiated in an openhole section will intersect both the borehole and the preferred fracture plane.
As the fracture extends away from the well, it turns, realigning itself with the preferred fracture plane. In the immediate vicinity of the wellbore, this turning results in tortuosity and a reduced fracture width, which can lead to premature screenouts or a choke effect during production. The most severe case of this occurrence is in an openhole completion in a well drilled perpendicular to the preferred fracture plane, where a hydraulic fracture initiates longitudinally but rapidly realigns itself with the preferred fracture plane normal to the borehole. Once realigned, the fracture grows back toward the well. As a result, both longitudinal and transverse fractures are present at the wellbore.
Extensive calculations detailing the orientation of the initial fracture relative to the wellbore and the preferred fracture plane are presented for all borehole deviations relative to the preferred fracture plane and the maximum formation-stress direction. Results of laboratory investigations of fracture initiation and propagation from openhole, deviated wellbores are summarized and compared to analytical predictions. The effects of wellbore diameter on fracture orientation and the potential for link-up of multiple fractures are also discussed.
P. 391
The Role of Geomechanics in Reservoir Simulation
Authors: Gutierrex M. , Lewis R.W. 
Published: December 2007

Abstract
The paper presents a discussion on the issues related to the interaction between geomechanics and reservoir simulation in deformable hydrocarbon reservoirs. Geomechanics is important in order to account for rock deformations due to pore pressure and temperature changes resulting from production and fluid injection. Rock deformation can affect the permeability and pore compressibility of the rock. In turn, the pore pressures will be vary due to changes in the pore volume. Geomechanics is also required in order to account for the effect of the non-pay rock surrounding the reservoir on the overall reservoir compressibility and the loads transmitted to the reservoir by the weight of the overburden rock.
The paper gives the formulation and finite element discretization of Biot's equations for multi-phase fluid flow in deformable porous media. Based on this formulation, it is argued that geomechanical response and multi-phase fluid flow are fully-coupled processes in that pore pressure changes affect rock mechanical response and vice-versa, and that the two processes occur simultaneously. By contrasting Biot's equations and its discretization to the corresponding multiphase fluid flow equations used in reservoir simulations, it is shown that reservoir simulators neglect or simplify important geomechanical aspects that can have impact on reservoir productivity. This is attributed to the fact that the only rock mechanical parameter involved in reservoir simulations is pore compressibility. This parameter is not sufficient in representing aspects of rock behaviour such as stress path dependency and dilatancy, which require a full constitutive relation. Furthermore, the pore pressure changes due to the applied loads from the non-pay rock cannot be accounted for by simply adjusting the pore compressibility. Example problems are shown in order to illustrate the value of coupling geomechanics to reservoir simulators. Finally, the practical benefits of using coupled geomechanics and reservoir simulations are discussed.
P. 439
"Coupled" Stress/Fluid/Thermal Multi-Phase Reservoir Simulation Studies Incorporating Rock Mechanics
Authors: Koutsabeloulis N.C. , Hope S.A. 
Published: December 2007

Abstract
Both the mechanical and hydraulic behavior of black oil reservoirs is dominated simultaneously by the properties of the intact' rock and the discontinuities within such masses. When inter-connected, these discontinuities define individual blocks that may become unstable, when subjected to pressure and/or thermal gradients. Studies involving coupled stress, thermal and flow modeling, in reservoir engineering, using both mechanical and hydraulic properties for the rock fabric and incorporating the stress magnitude and its directionality, have demonstrated the concept that preferred directionality during waterflooding is stress related and progressive in time. 2-D and 3-D field applications illustrate that reservoirs are both reactive' and dynamic in nature and substantial changes to both the hydraulic and mechanical constitutive behavior are taking place during waterflooding operations.
P. 449
Strain Hardening and Extensional Failure in High Porosity Chalk
Authors: Risnes R. , Garpestad O.J. , Gilje M. , Oland L.T. , Ovesen M. , Vargervik E. 
Published: December 2007

Abstract
The problem of strain hardening has been approached by preparing series of similar cylindrical chalk samples front outcrop material. The samples in each series could then be given a certain degree of deformation beyond the elastic limit. Afterwards the samples could be tested in standard triaxial tests at different confining pressures in order to determine the resulting yield envelope. Such experiments were performed both under compressional and extensional conditions.
Under compressional conditions the preceding loading resulted in a corresponding stretching of the elastic region as expected. But this apparent strengthening was not strengthening in a general sense. The material cohesion was greatly reduced (like the tensile strength). Under extensional conditions there was little or no effect of previous straining of the samples. It is therefore proposed to replace the words strain hardening by compressional hardening, to indicate that hardening is only hardening towards further compression.
The results from the extension tests defined one single failure line, irrespectively of previous straining, saturation fluid and chalk type. Assuming that the Mohr Coulomb criterion gives a valid description of failure in chalk, it is shown that this failure line corresponds to a critical state line for extension.
Failure criteria like Drucker Prager that are symmetric around the hydrostatic axis in stress space, cannot give a complete description of chalk behaviour.
A general criterion that includes intermediate stress and reflects both compressional and extensional failure, must have more like a convex triangular cross section with the hydrostatic axis in stress space, like the Lade's criterion.
P. 475
Water/Chalk (or Collapsible Soil) Interaction: Part II. Results of Tests Performed In Laboratory On Lixhe Chalk to Calibrate Water/Chalk Models
Authors: Schroeder Ch. , Bois A-P. , Maury V. , Halle G. 
Published: December 2007

Abstract
Ekofisk, Valhall and other North Sea reservoirs are made of water sensitive rocks such as pure high porosity chalk. Production of these fields implying water-flooding leads in several cases to compaction and subsidence.
In order to perform reliable predictions of compaction and subsidence when water-flooding such reservoirs, it is necessary to take into account not only the deformations that come from depletion in the compressible reservoir rocks but also to include additional deformations induced by water saturation (WS) increase.
These additional deformations may eventually be determined by performing water-injection (WI) tests in laboratory.
This paper presents additional tests that have been performed in laboratory in order to understand the mechanical behavior of chalk at the water-front.
It shows the existence of a degree of WS above which chalks mechanically behaves as if it is fully saturated, while chalk with a lower WS looks stronger than if the degree is higher. Greater the WS is, smaller the consolidation pressure Pc0.
Moreover, the deformations induced by water-flooding happen in two steps:
– the first one happens as soon as chalk get into contact with water and is instantaneous. – the second is delayed and looks more like creep as it happens after chalk gets in contact with water.
Observations and tests results are interpreted thanks to Piau's model.
P. 505
Applying Journey Management in the Service Sector
Authors: Corrigan Mark , Regnault Philippe 
Published: December 2007

Abstract
Driving is today the most dangerous activity facing a Schlumberger oilfield employee. In 1997, driving accidents were at the origin of 79% of the total Schlumberger work related oilfield fatalities. In order to address this risk, a comprehensive journey management system is being implemented, which targets not just driving techniques but rather the whole process of getting to and from worksites.
The process starts with a management review of the actual necessity of the trip and explores means of trip minimisation. Once committed, it continues with the assignment of qualified personnel and equipment appropriate to the task. On the hardware side, standards are set for vehicles which now not only include widely accepted devices such as seat belts and rollover protection, but include goals for fitting all vehicles with electronic monitoring systems. Road statistics have however proven that hardware alone will not be sufficient and a rigorous driver qualification process, followed by an extensive driver education program have been put in place. Programs include Defensive Driving courses, commentary drives, use of seat belt convincers, proactive application of data obtained from vehicle monitoring systems and, in the near future, the use of driving simulators.
Procedures have been established to ensure the subsequent journey is properly planned with potential risks evaluated and crews fully briefed. The route is clearly defined and rest stops planned.
Finally, and perhaps most importantly, the success of this initiative is no different to any other, in that it depends on clear management leadership and commitment.
Reversible Invert Emulsion Drilling Fluids - A Quantum Leap in Technology
Authors: Patel Arvind D. 
Published: December 2007

Abstract
A novel, invert emulsion fluid useful in the drilling, completion, and workover of subterranean wells has been invented. The new invert emulsion drilling fluid can readily and reversibly be converted from an invert, i.e., water-in-oil emulsion, to a regular, i.e., oil-in-water emulsion, and back to the original invert emulsion using an acid-base chemical switch.
The surfactants used in the reversible invert emulsion fluids are strong invert emulsifiers in the presence of lime. However, the same surfactants become regular emuisifiers in the presence of water-soluble acid. The reversible emulsion property of these surfactants allows the drilling fluid to be changed from an invert emulsion to a regular emulsion at different stages of the drilling/completion operation. During the drilling stage, the drilling fluid can be an invert emulsion achieving all the performance benefits associated with oil-based muds (OBM's). During the completion stage and afterwards, the emulsion can be reversed by adding water-soluble acid, thus providing excellent filtercake cleanups, improved production in an openhole completion, better cementing, and efficient cuttings cleanup and waste minimization.
The reversible system is simple and easy to run without any exotic changes in current operations or other additives than those commonly used in OBM's. The reversible drilling flu id is versatile and relatively inexpensive and versatile, especially as compared to new, exotic fluids on the market today. The reversible feature allows the mud to achieve performance, production, minimal environmental impact, and cost control.
The paper discusses the overall impact of reversible invert emulsion technology in meeting the environmental and functional requirements of drilling operations. The laboratory data show that this system can provide drilling performance similar to OBM's at various oil/water (O/W) ratios, mud weights, and in the presence of commonly encountered contaminants. This paper compares the new reversible fluids with previous state-of the-art invert emulsion drilling fluids. These new stable, reversible invert emulsion drilling fluids can readily be reversed to regular emulsions using inorganic acids such as hydrochloric acid or organic acids such as citric acid.
The paper discusses the application of reversible emulsion technology on efficient removal of filtercake and improved production in openhole horizontal well completions. The environmental impacts of this system on washing and disposal of drilled cuttings are discussed.
P. 55
Case History on Planning, Drilling and Completing the World Record ERW-XJ 24-3-A14
Authors: Jiang Zhang Ming 
Published: December 2007

Abstract
In recent years, extended reach drilling technology has been successfully used to develop marginal offshore oilfields in other part of the world. This encouraged the field operator Phillips China Inc and its partners China Offshore Oil Nanhai East Corp and Pecten Orient Oil Co. in South China Sea to apply this technology to develop a marginal field named XJ 24-1 which is located about 8 km from an existing platform – XJ 24-3. The XJ 24-1 field was discovered in late 1985. Attempts have been made to jointly develop it with existing fields by either unmanned satellite platform or subsea completion but these concepts were uneconomical due to the size of the field. The feasibility of the project was questionable from inception since the XJ 24-3-A14 well was a unique operation and limited resources were available in South East Asia. Through the team's dedication and perseverance, this project was completed on time and below budget and even exceeded some forecasts on reaching targets. This well was drilled and completed by June 10, 1997 in a total of 101 days reaching a TD at 9,238 m MD with 8,063 m of horizontal displacement.
World records set on this well were: Longest horizontal displacement (8,063 m)Deepest real time transmission of the MWD/LWD data (9,106m)
A series of new technologies specifically developed for extended reach wells have been successfully applied on this well. This paper describes the case history on planning, drilling and completing the world record extended reach well.
The Impact of Compression Forces on Casing String Designs and Connectors
Authors: Jellison Michael J. , Brock James N. 
Published: December 2007

Abstract
The effect of down hole axial compression forces on casing string designs and connectors is a major concern to engineers designing high temperature, high pressure (HTHP), extended reach and horizontal wells. Widespread concern regarding the significance of compression loads on casing string design is relatively recent. For decades engineers were either not aware that high compression loads may occur or were not concerned about the effect of compression on the casing.
This paper discusses the sources of axial compression forces in straight and directional wells. Methods to analyze casing subjected to compression and bending loading are presented including the effect of compression and bending on the von Mises Equivalent (VME) stress state of the pipe.
Connector selection for casing applications where high axial compression loads are anticipated is critical. Compression ratings for API casing connectors have never been addressed in API standards. The paper offers methods to evaluate API connectors for applications with significant compression loading. Compression ratings for premium casing connectors are generally available, but the justification for these ratings varies substantially from one manufacturer to another and the basis for the compression ratings may not be well documented. The paper discusses compression rating methods for various premium connector configurations including threaded and coupled, flush and near flush. Desirable and undesirable premium connector features that relate to compression capacity are reviewed. Results from compression testing of premium connectors are also presented.
The paper benefits engineers involved in the design of casing strings for applications with high compression and bending loading.
P. 137
Optimization of Drilling Parameters with the Performance of Multilobe Positive Displacement Motor (PDM)
Authors: Samuel G. Robello , Miska Stefan 
Published: December 2007

Abstract
Recent increase in application of coiled tubing for horizontal wells and in particular underbalanced drilling triggered the necessity of a powerful downhole motor. More often downhole motor stalling and motor replacement is a problem when using with coiled tubing drilling system. To enhance the technology and make the system effective, optimization of drilling parameters is essentially required. The frequent motor replacement during the operation incrementally increases the operating cost despite deriving potential benefits from coiled tubing drilling. The key to improved coiled tubing drilling system is a unified system approach that encompasses motor and bit. This paper presents an analytical study on the optimization of motor performance and drilling parameters. A new simple test called wear-off test is defined to establish an operating window. The practical usefulness of the theory, backed by the fundamental and optimal analysis for roller cone and diamond bits, is demonstrated with numerical examples.
P. 149
Underbalance Drilling Technique Improves Drilling Performance - A Field Case History
Authors: Cunha J.C. , Rosa Fabio S.N. 
Published: December 2007

Abstract
This paper describes the project and execution of a well using Underbalance Drilling (UBD) technique in South Brazil. Due to very hard formation in the intermediary section of the well and a very damage-sensitive reservoir, the use of UBD was considered mandatory for this field. New equipment were specially designed for use in the well including a liquid-gas separator and a new manifold. Since nitrogenated fluid was used as drilling fluid, a membrane was used to on-site generation of nitrogen. The article gives field data obtained in the well and also shows comparison between the results obtained with UBD and conventional drilling. A description of the advantages, problems and shortcomings of the technique also is included in the paper.
P. 213
Reduce Torque, Drag and Wear - Material Selection for Centralizers Used in Highly Inclined and Horizontal Wells
Authors: Kinzel Holger , Colvard R.L. 
Published: December 2007

Abstract
Centralizers for highly inclined and horizontal wells have to fulfill several requirements. Their main task is to provide adequate standoff. Additionally, centralizers have to facilitate casing and liner running and should allow pipe rotation. While bow-type centralizers normally are made of steel, various other alloy materials have been introduced for rigid type centralizers, including aluminium and zinc-aluminium alloys. Investigations have shown, however, that steel is a preferred material also for rigid type centralizers. Friction factors under all mud-wetting conditions of steel versus formations and pipe surface as well as the wear rate are low compared to other materials.
This paper describes the details of the investigations and describes two steel centralizers specifically designed for use in highly inclined and horizontal wells.
P. 217