bluuebunny/crossref_metadata_2025_split huggingface dataset:
Case Histories of Wellbore Cleanouts Using Near-Neutral Derusting Solution
Authors: Berry S. L. , Boles J. L. 
Published: December 2007

Abstract
Deposition of iron oxidation products, pipe dope and hydrocarbons on the metallic surfaces associated with wells can become significant. Whether the iron compounds come from the producing environment, from mill scale on a new tubing string, or from exposure to the elements during storage of a work string, their presence creates the potential for formation damage if they are dislodged and carried into the reservoir with treating fluids. Acid stimulation treatments, frac packs and gravel packs are reservoir interventions where this transportation of deposits could occur. Traditionally, an acid pickle treatment is performed prior to such treatments to remove the potential contaminants.
Acid pickling, while being effective, presents significant problems with safety, the environment and disposal of acidic fluids that return to the surface only partially spent. An alternative solution has been found using a near-neutral pH fluid to remove iron oxidation products and provide passivation of treated metallic surfaces. The safer acid level of this fluid provides a solution to both the downhole problems and the surface health, safety and environmental issues. Extensive laboratory testing has established the effectiveness of the fluid to removes not only iron oxidation products but also pipe dope and hydrocarbon deposits when used in conjunction with an environmentally friendly solvent. Performance is equal to traditional acidic fluids. Testing also demonstrated that metallic surfaces retained passivity.
This new fluid has now been used in several hundred wells in both the United States and South America. This paper will outline the laboratory results defining its capabilities compared to traditional hydrochloric acid systems. Case histories of usage in the United States and South America for the pre-treatment of downhole tubulars to remove contaminants are presented. The special case history of application to remove oxidation scale in a subsea fuel gas line system off the coast of Brazil is also discussed.
Drag Reduction by Particle Addition in Gas Flows
Authors: Kaminsky Robert D. , Robinson Chris M. , Talley Larry D. 
Published: December 2007

Abstract
The impact of spherical, flake, and fiber microparticle addition on frictional pressure loss in turbulent gas flows was experimentally investigated. Pressures up to 6.6 MPa (955 psig) were studied. Drag reduction (i.e., reduced frictional pressure loss) was clearly observed only at high dosages of &gt;0.01 gsolid/cm3gas,actual. A "lubrication" effect though was evident at lower dosages where relatively minor drag increases occurred despite significant solid loadings. No trends in drag reduction were observed based on Reynolds number or pressure. Larger particles tended to increase frictional losses, especially at moderate dosages.
Interpreting Transient Tests in High-Permeability, Gas-Condensate Reservoirs
Authors: Kabir C. S. , Landa J. L. 
Published: December 2007

Abstract
In gas-condensate reservoirs, interpretation of static and dynamic skin is fraught with uncertainties when analysis is attempted with simple analytic tools. Problems compound when two-phase flow occurs owing to large drawdowns with flowing pressures dipping below the dewpoint pressure. Under this circumstance, static and dynamic skin values are difficult to separate using a single-phase analog.
This paper deals with issues surrounding transient-test interpretation when no discernible condensate bank forms in the well vicinity owing to low drawdown in high-kh reservoirs and low-condensate yields. In particular, we explore why skin values obtained by a single-phase analog cannot be mapped directly onto a two-phase numeric model.
Some of the key findings suggest that both components of skin are significantly lower when evaluated with a numeric model as opposed to its analytic counterpart. In gas-condensate systems, we recommend the use of a numeric model because of its superior ability to handle physics of flow. This is particularly so when long-term performance evaluation is sought.
Simplified Wellbore Flow Modeling in Gas-Condensate Systems
Authors: Kabir C. S. , Hasan A. R. 
Published: December 2007

Abstract
Predicting long-term reservoir performance with realistic wellbore models is fraught with uncertainty owing to the complexity of two-phase flow. That is because even a calibrated two-phase flow model departs from its expected performance trend when changes in flow conditions occur. These inevitable changes include gas/liquid ratio, wellhead pressure, and flowline pressure with time, among others. Influx of water further exacerbates the prediction problem.
This study explores the possibility of using simplified approaches to computing bottomhole pressure (BHP) from wellhead pressure (WHP), measured rates, gravity of producing fluids, and tubular dimensions. BHP computations on three independent data sets comprising 167 gas-condensate well tests suggest that the no-slip homogeneous model applies quite well. Statistical results show that the homogeneous model compares quite favorably with mechanistic two-phase flow models. However, the main advantage of the simplified model is that its recalibration with field data is not required because the gas/oil ratio increases with time, thereby making the model more robust.
Most field datasets suggest random error in BHP calculations; uncertainty in rate measurements appears to be the most probable cause. High-GLR systems can tolerate large errors in rate measurements, but low-GLR wells demand greater accuracy.
Two-Phase Flow Upscaling for Flow in Thin Beds and Implications for Data Acquisition
Authors: Kasap E. 
Published: December 2007

Abstract
Producing from less prolific reservoirs is becoming more feasible because technology is becoming less costly and more robust in detecting and characterizing thinly bedded formations. Some of these reservoirs contain beds having thicknesses on the scale of several inches. Without upscaling, numerical models for field studies with grid block thicknesses on the order of thin-bed dimensions cannot be run. Even with 1% laminations in a medium-sized reservoir, more than two billion grid blocks are required to describe the reservoir heterogeneity. Developing representative multiphase flow parameters such as relative permeability, capillary pressure, and gravity functions for grids used in a field study poses upscaling challenges.
In this study, a sample thin-bed dataset was used to develop proper upscaling techniques for single-phase and multiphase flow conditions to be used in a field study. A near-wellbore simulation model was built, with which fine-scale numerical simulations were conducted and pseudofunctions as apparent relative permeabilities were generated for a sample thinly bedded formation. Several boundary conditions such as near-wellbore radial flow, linear flow, aquifer full-face connection, and aquifer line connection were studied. Back-calculated pseudofunctions were put into representative coarse-scale models to test if they reproduce the original flow responses. Analytical pseudofunctions were also calculated and compared with the numerical pseudofunctions.
From the results of this study we concluded that the back-calculated pseudofunctions from numerical simulations would reproduce fine-scale results for relatively continuous thin beds. Analytical pseudofunctions could robustly reproduce the fine-scale results with significantly less development effort compared to that needed to develop numerical pseudofunctions; however, analytical pseudofunctions can only be applied in simple depositional systems with simple boundary conditions.
Assessing Borehole-Position Uncertainty From Real-Time Measurements in an Earth Model
Authors: Prange Michael D. , Tilke Peter G. , Kaufman Peter S. 
Published: December 2007

Abstract
There has been much interest in improving uncertainty estimates of borehole position. Such estimates are useful in estimating the probability of intersecting a reservoir target, in estimating the probability of colliding with an adjacent borehole, and in avoiding high-risk zones. We describe here a new geometrical model for borehole-position uncertainty that encompasses both systematic and random errors in the borehole-position survey. Furthermore we present a new technology that refines the borehole-uncertainty estimate in real time during the drilling of the well through the use of logging-while-drilling (LWD) measurements (e.g., measurements of formation depth, dip, and azimuth from image logs). This technology uses a Bayesian formulation to update the uncertainty of both the borehole trajectory and the earth model to be consistent with these measurements. The final uncertainty model couples borehole uncertainty with earth-model uncertainty. We use a geosteering field example to demonstrate how both earth-model and borehole-trajectory uncertainties are reduced through this use of real-time measurements.
Cleanup of Water Blocks in Depleted Low-Permeability Reservoirs
Authors: Parekh Bimal , Sharma Mukul M. 
Published: December 2007

Abstract
Poor gas inflow performance is observed in some depleted, low permeability, reservoirs after completion and workover operations. The use of aqueous treatment fluids often results in a 'water block' due to poor recovery of the fluids that have leaked-off. This curtails well deliverability due to reduced relative permeability to gas/oil in the invaded region.
This study analyzes the effect of various factors governing the cleanup of water blocks in fractured and unfractured wells for both gas and oil reservoirs. The effects of drawdown, capillary pressure, relative permeability, and heterogeneity as well as the influence of fracture geometry on well deliverability following some well operations, such as fracturing, have been examined by detailed simulations.
Drawdown, fracture length and shapes of relative permeability curves strongly affect the recovery in productivity. On the other hand, end point relative permeabilities and horizontal well length have an insignificant impact on cleanup. Higher vertical permeabilities favor early recovery of well productivity in 'high perm' layers and delay cleanup of water blocks in 'low perm' layers.
The results suggest the need to lower capillary pressure by reducing interfacial tension and/or altering wettability of the rock surface from strongly water-wet to intermediate-wet. With the correct selection of treatment fluids, proper design of fracture geometry and optimum drawdown applied it is possible to cleanup water blocks more rapidly in depleted low-permeability reservoirs.
Petrozuata - An Application of Multiphase Metering Technology
Authors: Bortolin Luigi , Mehdizadeh Parviz , Stobie Gordon 
Published: December 2007

Abstract
The application of Multiphase Meters (MPM) over the past decade or so has, in the main, been in deployment of meters in small quantities (i.e. ones and twos) and there are few applications where MPM's have been deployed in bulk. Petrozuata in Venezuela is such an operation where 37 MPM's were deployed and have been in use for over 5 years.
This paper describes the facility and the operations where MPM's have been selected, tested and implemented. The paper also describes the difficulties experienced and the operational results from the extensive use of such measurement techniques.
A New Method for Injectivity Impairment Characterization From Well and Coreflood Data
Authors: da Silva M. , Bedrikovetsky P. , Van den Broek W. M. G. T. , Siqueira A. , Serra A. L. 
Published: December 2007

Abstract
The injector impairment due to suspended particles during waterflood project happens in two stages: firstly particles penetrate into a reservoir and are captured by the rock (deep bed filtration); at the second stage, after the reservoir inlet is plugged by particles, the particles build up a filter cake. Prediction of injectivity decline is based on mathematical modelling of deep bed filtration and filter cake formation. The model parameters are determined from either laboratory tests or field data.
The model parameters for deep bed filtration – the filtration and formation damage coefficients – can be determined from laboratory pressure measurements using so-called 3-point pressure method. The method for determination of the critical porosity fraction, which is necessary for calculation of the time of transition from deep bed filtration to filter cake buildup, is not available in the literature.
In the current paper, the 3-point pressure method was used for determination of the critical porosity fraction. The data from 18 laboratory tests were treated, and the correlation between the formation damage coefficient and the critical porosity fraction was obtained. This correlation allows determining of the deep bed filtration and filter cake buildup parameters from either routine coreflood test or well injectivity history.
Proppant Distribution and Flowback in Off-Balance Hydraulic Fractures
Authors: Daneshy A. Ali 
Published: December 2007

Abstract
The vast majority of industrial hydraulic fractures propagate in off-balance mode, where the fracture is not in a single plane, includes many shear fractures and branches, and is shorter and narrower than computed by existing models. Proppant transport, deposition and flowback in these fractures are also substantially different than for single fractures. Presence of shear fractures leads to formation of many randomly distributed tight proppant packs. Many of these are inherently unstable and serve as sources for proppant flowback. But they are also the source for fracture conductivity. Gravity causes formation of proppant beds. These are usually formed at the lower extremities of the fracture. Branches generally trap the proppant and are unlikely sources for flowback. They also add little to productive capacity of the fracture. And, some of the proppant in the fracture is loosely scattered inside it and is free to move when sufficient drag is exerted by fluid flow.
The paper places special emphasis on proppant flowback and shows that the three requirements for its occurrence are motion initiation, motion maintenance and infinite conductivity along the return path. Gravity plays a very important role in this process, as does well completion. Tendency for equilibrium between reservoir fluid velocity and deposited proppant results in gradual decrease and eventually stoppage of proppant return at any given flow rate. This equilibrium can be disrupted by sudden increases in flow rate which then triggers instability and proppant flowback.
Case histories from actual treatments illustrate and re-enforce the findings of the paper.
Well Orientation Effect on Borehole Stability
Authors: Morita Nobuo 
Published: December 2007

Abstract
Using laboratory and field borehole stability data, an empirical correlation of borehole size and stress gradient effects is derived. Using the correlation, the well orientation effect on borehole stability is numerically studied. The study shows that the borehole stability is controlled, under the normal condition, by the largest in-situ stress in the radial borehole direction so that the borehole orientation effect for a horizontal well is not significant if two horizontal stresses are less than the vertical overburden pressure, however, if one horizontal stress is greater than the vertical stress, the orientation significantly affects the borehole stability.
Depth Control: Reconciliation of LWD and Wireline Depths, Standard Practice and an Alternative Simple but Effective Method
Authors: Wilson H. , Lofts J. C. , Page G. C. , Brooks A. G. , Walder D. 
Published: December 2007

Abstract
Depth is one of the most important formation evaluation measurements, but it is also one of the most difficult to define accurately. LWD measurements, which rely on driller's depth, are becoming more prolific and widely used. Wireline measurements, with their independent determination of depth, are still commonplace, while the use of both wireline and LWD measurements together is still largely unavoidable in a full data acquisition program. Reconciliation of depth, including survey error when converting to TVD's, is still one of the key problems faced when evaluating and fully interpreting these data sets.
This paper reviews the current common practices applied to correction and correlation of depth. Generally, these practices are intended to correct all other measured depths to a single definitive depth reference. The extent to which the intended goal is achieved is assessed. The paper also describes an alternative approach which accepts all depths as valid, but assigns uncertainties to each. A real well is used to compare the outcomes for each approach. One conclusion is that correction of drill pipe depths for stretch effects is desirable, and a simple but effective correction method is described.
Command Skills for Drilling and Completion Teams: Managing the Unexpected
Authors: Crichton Margaret T. , Henderson William G. , Thorogood John L. 
Published: December 2007

Abstract
Many drilling and completion teams plan extensively in the office for the operations ahead. Most engineers now accept that successful implementation of the planned operations, especially the transition from planning to operations, needs effective skills such as leadership, communication and teamwork. What it takes to manage unexpected events successfully, especially under pressures such as time (i.e. cost), uncertainty and difficult inter-personal relationships, has until now been less well understood. Analyses have been carried out of how unexpected events are managed in domains such as rail transport, energy production, and the police, prison, and fire services. These analyses have identified that human errors in managing the event have at times actually worsened the situation. In these domains training for effective command skills (decision making, situation assessment, communication, leadership, teamwork) is recognized as essential. Yet in the drilling and completions environment these skills are seldom identified as important, even for routine operations, and formal training is provided only rarely. Experience in dealing with unexpected events is recognized as a good teacher, but learning by trial and error can ‘send in terrific bills’ in terms of stress effects on decision makers and teams. This paper presents findings of a recent research project commissioned and funded by BP Exploration. The research identified the basic social and cognitive skills necessary for effective functioning in Drilling & Completion teams, and especially the command skills for managing unexpected events under pressure of time, risk and uncertainty. The project also developed a toolkit for team performance assessment and potential training interventions applicable not only to routine operations but also to managing unexpected events under pressure.
On Accurate Tracing of Streamlines
Authors: Matringe S. F. , Gerritsen M. G. 
Published: December 2007

Abstract
Because of their efficiency, streamline methods are increasingly used for, amongst others, flow based upscaling, history matching, optimal well placement, and also compositional simulation, for which they show great potential. The accuracy of the streamline solutions depends on several factors including the quality of the pressure solve, the numerical scheme used to propagate solution components along streamlines, the mappings between streamlines and pressure grid, and naturally, the quality of the streamline tracing algorithm.
Using the homogeneous quarter five spot pattern, for which the exact streamline pattern is known analytically, we show that the errors in streamline location, computed arc length and time of flight can be significant, and can negatively affect the simulation results. The tracing errors are caused by the inaccuracy of the fluxes at the edges of the gridblocks, the choice of streamline launching pattern, and the order of flux interpolation used to compute the velocity field. We have investigated the use of the Mixed Hybrid Finite Element method for solving the pressure field that is known to provide more accurate fluxes, and discuss when this method leads to improved tracing results over the traditional finite difference method. We also show that a judicious choice of launch locations leads to lower tracing errors, and present two new methods to improve streamline tracing within grid cells. The first is an Adaptive-Mesh-Refinement-inspired tracing method that provides more accurate tracing where needed. The second method is a higher order variation on Pollock's tracing that uses a second order interpolation of the velocity field. The method is based on the theory of mixed finite element methods and is therefore easily extendable to any type of grids. Both methods proposed are flux conservative and efficient.
Diagnosis of Horizontal Injectors with Distributed Temperature Sensors
Authors: Bui T. D. , Jalali Y. 
Published: December 2007

Abstract
We present an interpretation methodology for analysis of temperature profiles obtained in horizontal injectors with fiber optic distributed temperature sensors. We consider injection as a non-isothermal process, due to the contrast in the temperature of injected fluid and reservoir fluid. We examine the particular case of water injection in an oil-bearing reservoir and analyze a field case with a notable temperature contrast downhole (222 °F reservoir, 100 °F water). We examine the behavior of the wellbore temperature profile during injection, shut-in, and post-shut-in periods, for both short-term and long-term injection (days to months). We present a methodology for estimation of the injectivity profile along the length of the well during short-term injection, and discuss issues associated with interpretation of long-term data. The proposed methodology can be applied to injection testing of producing wells.