bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of the Stability of Inclined Wells
Authors: Garrouch Ali A. , Ebrahim Abdullah S. 
Published: December 2007

Abstract
The need for wellbore stability analysis during the planning stage of drilling is rising due to the economic considerations, and because of the increasing use of highly-deviated, extended-reach, and horizontal wells. Wellbore instability can cause lost circulation when tensile failure occurs, and can cause caving and hole closure when collapse failure occurs.
This paper presents the method and results of wellbore stability analysis for three common reservoir lithologies consisting of a consolidated sandstone, a shaly sandstone, and a limestone formation. The effect of stress anisotropy on the mechanical stability of wellbores is evaluated while varying the inclination angle from 0 to 90°, for both the Mohr-Coulomb and the Drucker-Prager failure criteria.
The selected failure criterion, and the in-situ rock stress regime are found to have significant effects on the safe drilling fluid density required to maintain wellbore integrity. According to some field examples, the Drucker-Prager failure criterion appears to systematically mimic rock conditions more realistically than the Mohr-Coulomb failure criterion. The simulated consolidated sandstone formation is found more stable with lesser drilling fluid density, at any inclination angle, than the simulated shaly sandstone formation. The simulated limestone formation is even more stable than the consolidated sandstone at all inclination angles since it requires lighter fluid density to prevent wellbore collapse. For all these rock types, the higher the deviation angle (from vertical), the higher the drilling fluid density needed for maintaining wellbore integrity. For the depth and rock conditions simulated, both consolidated and shaly sands are unstable in a strike-slip stress regime, but stable in an extensional stress regime. The simulated limestone formation was found stable in both stress regimes. However, in an extensional stress regime, the limestone formation required lighter fluid density to maintain wellbore integrity than in a strike-slip stress regime.
This study provides a valuable insight into the influence of inherent factors such as the in-situ stress regime, pore pressure, and formation properties, and conditionally variable factors such as wellbore directions and inclination angle on wellbore stability. Results of this investigation can be used to improve the management of wellbore integrity, thereby increasing drilling efficiency and reducing drilling costs.
Application of a Concentrated Oxidizing Breaker Preflush in High-Permeability Frac-Pac Treatments
Authors: Park E. I. , Bennett Scott , Powell Ron , Procyk A. D. , Griffin D. E. 
Published: December 2007

Abstract
A major operator has used a novel approach to improve the performance of stimulation fluids in high-permeability, deepwater completions. A concentrated breaker solution is pumped into the formation before the introduction of crosslinked gel. This breaker solution improves cleanup of fractured and non-fractured perforations during high-permeability fracturing operations. This technique was developed because laboratory testing indicated that conventional breakers can be consumed by sediments, resulting in less than optimal gel breaks. This observation, when combined with the knowledge that whole crosslinked gel leakoff occurs in high-permeability formations, makes it necessary to pre-treat the near-wellbore region with a sacrificial concentrated breaker.
This paper includes studies on core materials with specific mineral compositions to determine the effectiveness of the concentrated breaker technique. Interaction between fracturing-fluid breakers and formation materials has been investigated at temperatures between 120° and 225°F. Core-flow experiments measuring the amount of active breaker present in the fluid exiting the core have also been performed with both enzyme and oxidizing breakers, and retained breaker activity of enzyme and conventional oxidizing breakers was compared.
Enzyme stability is affected by the presence of minerals as well as the formulation of the stimulation fluid. A comparative study performed at 175°F showed that breaker activity decreases as temperature increases for both a conventional oxidizing breaker as well as a stable, high-temperature oxidizing breaker. However, at 225°F the stable, high-temperature oxidizing breaker maintained some activity upon exiting the core.
This paper highlights three successful applications of the concentrated breaker solution in the Gulf of Mexico (GOM). These successes are compared to performance from offset wells, providing a benchmark for identifying the benefits of this new process.
Acidizing Carbonate Reservoirs: Numerical Modelling of Wormhole Propagation and Comparison to Experiments
Authors: Golfier F. , Bazin B. , Zarcone C. , Lernormand R. , Lasseux D. , Quintard M. 
Published: December 2007

Abstract
Many acidizing treatments in carbonate reservoirs do not produce expected increase of productivity, especially in the case of open-hole horizontal wells. This is due to the poor modelling of near well-bore mechanisms. This paper describes a new 2D numerical simulator which features a better description of the physics and which is validated on experimental data.
The numerical simulator presents the coupled mechanisms of flow and dissolution at the origin of the wormhole instability. The macroscopic dissolution equation is derived from a volume averaging of the advection/diffusion and reaction equations written at the pore scale. The flow description is based on Darcy-Brinkman equation which accounts for Darcy's flow in the matrix and Stokes flow in the wormhole.
Two series of experimental results are used for the validation: acidizing experiments with carbonate cores previously published by IFP and other investigators and new model experiments. These experiments consist in injecting under-saturated salt water into a porous medium made of salt. The dissolution instability, channel development and wormhole propagation are recorded by a video camera.
The results predicted by the numerical model reproduce most of the observations in salt and carbonate: 1) the effect of the flow rate on the dissolution regime, i.e. compact, wormholing or uniform behaviour; 2) transitions from wormholing to ramified which slow down the wormhole propagation rate; 3) the effect of the injection conditions on the wormhole propagation rate, the optimum flow rate and the maximum distance of wormhole penetration. Optimum conditions for wormhole propagation are deduced.
The model is built to provide relations on wormhole propagation rate depending on the reservoir properties and the injection conditions. These relations will then be integrated in a near well-bore simulator coupled to a reservoir simulator for a better design of the acidizing treatments in carbonates.
Corresponding Author: Mrs Brigitte Bazin, IFP.
Hydroxyaminocarboxylic Acids Produce Superior Formulations for Matrix Stimulation of Carbonates
Authors: Frenier W. W. , Fredd C. N. , Chang F. 
Published: December 2007

Abstract
In this paper, we will describe the development and testing of hydroxyaminocarboxylic acid chelating agents (HACA) as components of matrix acidizing formulations for stimulating carbonate formations. The pioneering work of Fredd and Fogler1 demonstrated that organic acids and chelating agents have unique attributes that lend themselves to efficient production of wormholes in many acidizing situations. We have applied the techniques for determining transport and reaction kinetics to stimulation fluids containing the hydroxy amino chelating agents. Linear core flood tests were used to study wormhole formation. Rotating disk tests with marble samples were employed to elucidate the kinetics and mechanisms of the dissolution processes over a temperature range of 20 °C to &gt; 100 °C (65 to &gt;200 °F).
Both HACA chemicals studied, that is, hydroxyethylethylenediaminetriacetic acid (HEDTA) and hydroxyethyliminodiacetic acid (HEIDA) produced wormholes in limestone cores when tested at 150 °F. However the efficiency and capacities differ. Because these chemicals have high solubility in the acidic pH range, it was possible to test acidic (&lt; pH 3.5) formulations. These solutions have properties of both mineral acids and complexing agents. The rotating disk tests allowed us to measure the diffusion coefficients as well as the surface reaction rate coefficients, at different temperatures. These parameters were used to determine the efficiency of wormhole formation as a function of temperature, by an overall reaction rate vs. pump rate relationship; i.e., the Damköhler number.
Screenless Completions: The Development, Application and Field Validation of a Simplified Model for Improved Reliability of Fracturing for Sand Control Treatments
Authors: Guinot Frédéric , Zhao Jun , James Simon , Emmanuel d'Huteau 
Published: December 2007

Abstract
The successful application of fracturing for sand control has been reported from many different areas. Several explanations have been advocated for these successes such as "re-stressing" the wellbore, creation of a "halo effect" around the wellbore and maintaining the bottom hole pressure above a critical level to prevent perforation collapse. The latter approach has led to complex models predicting the conditions of perforation failure.
However, once the perforations have collapsed, the production of formation sand is governed by the transport of the sand from the perforation tunnels. Frequently, decreasing the production rate stops sand production, indicating that there is a critical flow rate below which sand cannot be transported into the wellbore. In this study, we present the development, application and field validation of a spreadsheet tool to improve the reliability of fracturing for sand control treatments.
A universal curve was generated from numerical simulations, showing that the percentage of the total flow through the perforations not connected to the fracture was a function of the formation and fracture properties and was independent of the reservoir fluid properties. The generation of a universal curve eliminates the need to use a reservoir simulator and allowed the development of a tool to aid the design of fracturing for sand control treatments. The spreadsheet tool has been validated with data from successful fracturing for sand control treatments.
Achieving High Rate Completions with Innovative Thru-Tubing Sand Control
Authors: Bell Thomas A. , Martch William E. , Morrison Dan W. 
Published: December 2007

Abstract
An improved through-tubing sand control technique was utilized recently to enhance reservoir recovery and improve life-cycle economics. This coiled tubing-conveyed method uses several technical innovations that improve the reliability of the vent screen sand control completion. The innovations can be shown to: (1) improve the rate at which reserves can be recovered; (2) improve completion efficiency; (3) reduce mechanical risk; (4) reduce completion costs; (5) extend the economic life of the well; and (6) control fines migration.
Thermogelf Project: An Efficient In-Situ Insulation Method to Enhance Production
Authors: Kuperus Eddy , Beauquin Jean-Louis , Jansen Bernard 
Published: December 2007

Abstract
Besides curing wax, hydrate or viscous flow problems, thermal insulation should also improve lift performance and producing time of wells and risers, since it helps to reduce by various ways the liquid content in a gaseous column of production. "Thermogelf" project objectives were to prove benefits of thermal insulation on well performance and to test one specific method to set a super insulation (an aerogel) in a producing well, avoiding a work-over. Thus, a silica aerogel has been processed into a self-killing gas well in the Netherlands, in autumn 1999. Although the process was not completed, because not so fast as expected, this field trial enhanced significantly the well production, and produced a decisive experience to improve the implementation method. Therefore, this project demonstrated that "Thermolift" methods could be lucrative on numerous mature and new fields, and aerogel processing in the annulus of wells should be next developed as a relevant technology.
Measurement of the Mechanical Properties of Filtercakes
Authors: Cerasi P. , Ladva H. K. , Bradbury A. J. , Soga K. 
Published: December 2007

Abstract
In order to improve drilling mud design to cater for specific well situations, a more comprehensive knowledge and understanding of filter cake failure is needed. This paper describes experimental techniques aimed at directly probing the mechanical properties of filter cakes, without having to take into account artefacts due to fluid flow in the substrate. The use of rheometers allows us to determine shear yield stress and dynamic shear modulii of cakes grown on filter paper. A new scraping technique measures the strength and moisture profiles of typical filter cakes with a 0.1 mm resolution. This technique also allows us to probe the adhesion between the filter cake and its rock substrate. In addition, μdometer drained consolidation and unloading of a filter cake give us compression parameters useful for Cam Clay modelling. These independent measurements give similar results as to the elastic modulus of different filter cakes, showing an order of magnitude difference between water based and oil based cakes. We find that these standard cakes behave predominantly as purely elastic materials, with a sharp transition into plastic flow, allowing for the determination of a well-defined yield stress. The effect of solids loading on a given type of mud is also studied.
The Relative Importance of Solids and Filtrate Invasion on the Flow Initiation Pressure
Authors: Roy Rana S. , Sharma Mukul M. 
Published: December 2007

Abstract
Studies conducted earlier indicate the importance of solids invasion on determining the magnitude of Flow Initiation Pressure (FIP). Other studies have shown that relative permeability effects can play an important role in determining the FIP. In this paper we clearly identify the conditions under which solids invasion and relative permeability effects can play important roles.
Experiments are conducted with brine saturated cores and cores containing a residual brine saturation. FIP measured by flowing back with brine and with oil are reported. For low permeability rocks and small mobility ratios, relative permeability effects appear to play a dominant role. For higher permeability rocks (&gt;100 md) and large mobility ratios, solids invasion becomes increasingly significant. A key difference between these two components of FIP is that while relative permeability effects will dissipate with time, internal filter cakes may not.
A model to calculate the FIP is presented which allows us to evaluate the relative magnitude of the pressure drop caused by relative permeability effects versus that caused by solids invasion. The results of this study clearly show that both solids invasion and filtrate invasion can play an important role in determining the FIP. In addition factors such as the relative mobility of water and oil and the depth of invasion of solids are important parameters. A method is presented that allows us to estimate FIP values in the field based on static filtration tests conducted on cores.
Modelling of Near-Wellbore Damage Removal by Natural Cleanup in Horizontal Open Hole Completed Wells
Authors: Ding Y. , Longeron D. , Renard G. , Audibert A. 
Published: December 2007

Abstract
Formation damage in horizontal wells, often open hole completed, is a critical point for oil fields developed in deep offshore where acceptable development costs are based upon a limited number of highly productive wells. This paper describes a simplified numerical approach to model filter cakes removal by natural cleanup when the well is put under a drawdown pressure difference. A flow simulator taking into account the near well permeability variation has been developed using cylindrical grid with very small gridblocks around the well. Laboratory data obtained on sandstones damaged with an oil-based mud have been used as input data to model filter cakes removal by natural cleanup. The purpose of this modelling is to optimize the applied drawdown pressure to study the variation of well productivities as a function of the pressure drawdown to get the best possible well performance preventing sand production problems in poorly consolidated formations.
Effects of Non-uniform Skin Distribution on Horizontal Well Inflow Performance
Authors: Permadi P. , Wibowo W. 
Published: December 2007

Abstract
Formation damage around a horizontal wellbore has been a long-standing problem. The damage zone is expected to be a cone-like shape, extending from the heel end to the toe. This situation leads to a difficulty in studying the inflow performance. In fact, previous studies assumed clean and homogeneous formations and ignored any skin factor in predicting pressure drops along a horizontal wellbore, critical rate, and water breakthrough time.
The present study is focused on investigating influx and flowing pressure distribution along a horizontal wellbore in the presence of non-uniform formation damage. The relevance with the inflow performance is also discussed. Modified wellbore hydraulics correlations coupled with a reservoir inflow equation are used to accommodate this effort. Calculations are performed for different skin distribution, damage severity quality, and wellbore diameters.
Results obtained show that non-uniform skin causes reduced influx rate toward the heel end. The undamaged well reveals an opposite trend as expected. For a given total production rate, the influx rate at some portions of the wellbore increases as the formation damage gets heavier, as well as for smaller wellbore diameter, resulting in greater pressure drops. Thus, the presence of non-uniform skin promotes an increase in pressure gradients within the wellbore. The changes in pressure losses are more sensitive to the level of damage severity in smaller wellbore diameter. Such a study has not been previously reported in the literature.
Overall, this investigation improves our knowledge to better understand flow behavior in a horizontal wellbore. The paper presents information to be considered in predicting the inflow performance and also provides a guide for deciding or optimizing a horizontal well completion strategy.
Static and Dynamic Evaluation of Calcium Carbonate Scale Formation and Inhibition
Authors: Kohler N. , Courbin G. , Ropital F. 
Published: December 2007

Abstract
Calcium carbonate scale formation is a major drawback in oil or gas production wells, in geothermal processing equipments and in industrial cooling water installations. In most cases it reduces the overall fluid flow rate, induces formation or production damage and may lead to a shutdown of exploiting operations.
Various chemical inhibitors have been proposed to inhibit scale deposits. A major challenge is the evaluation of their action in near real operating conditions. Usually effectiveness is evaluated by the analysis of residual scale inhibitor in brines.
A novel approach is here proposed which uses an electrochemical technique to accelerate scale formation. Measurements on an electrode immersed in the tested water include as a function of time the decrease of the incident current (chronoamperometry) and the simultaneous increase of the weight recorded by a microbalance (chronoelectro-gravimetry) as a consequence of the progressive electrode surface coverage by scale deposit. By using a specific experimental device it is possible to follow and visualize in situ scale deposition or inhibition on a metallic surface under near-real hydrodynamic flow conditions.
A New Biopolymer-Free, Low Solids, High Density Reservoir Drilling Fluid
Authors: Horton Robert L. , Dobson James W. , Tresco Kim O. , Knox Dave A. , Green Taylor C. , Foxenberg William E. 
Published: December 2007

Abstract
A new reservoir drilling fluid system utilizes a nonbiopolymer, acid- or enzyme-soluble polymer that serves both as viscosifier and fluid-loss additive when combined with activated magnesium oxide and a divalent-cation-based brine. The new fluid shows a unique shear-thinning rheological profile featuring relatively low, high-shear-rate viscosity along with relatively high, low-shear-rate viscosity. This behavior is highly unusual in high-density, brine-based reservoir drilling fluids. A result of this behavior is that effective hole cleaning is provided without generating excessive high-shear-rate viscosities that lead to disproportionate equivalent circulating densities. The new fluid system is based on the higher density, divalent-cation-containing brines (utilizing CaCl2, CaBr2, CaCl2 / CaBr2, ZnBr2 / CaBr2 and ZnBr2 /CaBr2 / CaCl2) in the 11.5 to 17.5 lb/gal density range. The total amount of the sized CaCO3 bridging particles is kept relatively low, 13 to 35 lb/bbl, so that thin, chemically removable filter cakes are produced. The size distribution of these bridging particles is designed according to the ideal packing sequence for optimizing sealing and producing a minimally invading (well productivity enhancing) fluid.
Filtrate Invasion, Barite "Sag" and Grain Crushing by Cutter Impact -- Experimental Wellbore Damage
Authors: Crossley R. , Essone J-Y. Essiane , Wubben Ton , Graas G. van 
Published: December 2007

Abstract
Barite "sag" is known to reduce drilling performance. This experimental study, which used full scale coring bits on large sandstone blocks, shows that the recrushed barite and cuttings can be smeared on the borehole wall to create a low permeability coating. In at least one mud type this coating may be difficult to remove. Drilling fluids are often tailored to block anticipated pore throat distributions with components that can be removed during clean up. In these experiments the grains lining the wellbore were shattered by cutter impacts to a depth of up to 2 mm. This changed the pore throat size distributions in this thin zone, and crushed grain debris was a major component blocking pore throats in this zone. If these factors apply in the subsurface, then drilling fluid may not behave as planned during spurt loss, and successfull clean up may prove more difficult than anticipated. Depth of filtrate invasion is known to be controlled in part by formation permeability, by degree of static mud weight overpressure and by drilling fluid perfomance. In this study, the duration of dynamic interactions between bit, rock and mud is an additional control on filtrate invasion. This suggests that petrophysical analyses of log responses should not ignore ROP.