bluuebunny/crossref_metadata_2025_split huggingface dataset:
BHA Design Algorithm for Extended Reach Wells
Authors: Agawani Mamdouh M. , Rahman Sheik S. , Maidla Eric E. 
Published: December 2007

Abstract
A design criterion is developed to select the optimum bottomhole rotary assembly configuration (drill collar size and stabilizer positions). This allows maximum correction in the hole inclination by changing the weight on the bit while drilling a section of a hole. A computer algorithm is written in FORTRAN code to optimize the bottomhole assembly configuration. This algorithm can be used with any BHA model that calculates forces at the bit under static or dynamic conditions. A case study is presented to explain the design algorithm.

Introduction
Directional wells are usually kicked off from vertical by some type of bent sub/bent housing and downhole motor. When the hole inclination becomes sufficiently high, drilling may resume with a steerable system or a rotating system.
In conventional rotary systems a packed-hole assembly uses a sufficient number of stabilizers so that no significant change in hole angle occurs. Likewise, proper stabilizer positioning can increase the hole angle via the fulcrum principle, or it can decrease via the pendulum principle (1985). Conventional rotary systems are normally designed to drill holes with a constant rate of change of inclination. However, discrepancies between prediction and field results frequently occur. Therefore, experience and knowledge are necessary tools in the selection of such a drilling system.
Steerable systems are widely used in drilling horizontal and extended reach wells. This is mainly because, drilling direction can be changed in a more controllable way to follow a predetermined trajectory without the need of changing the assembly. The bottomhole configuration of steerable systems, however, creates major torque and drag problems while drilling highly deviated wells in the sliding mode. It becomes difficult to have even torque distribution on the bit which is essential to control tool-face. High drag can limits the ability of maintenance of a constant weight on the bit. This reduces penetration rate and makes it hard to control tool-face as the reaction torque at the bit varies. Furthermore, drag can limit the total horizontal displacement.
FLEX: An Object-Oriented Reservoir Simulator
Authors: Verma Santosh , Aziz Khalid 
Published: December 2007

Abstract
This paper describes the design of FLEX, an object-oriented, flexible grid, black-oil reservoir simulator. An object-oriented decomposition of a reservoir simulator helps in dealing with the complexity of this problem. This approach is particularly useful because of the difficulties associated with generation and use of flexible grid geometries (like Voronoi, median, boundary adapting grids, etc.).
The entire problem is divided into subsystems like geometry, gridnodes, gridnode connectivity, grid, reservoir fluid flow, and matrix. Each of these subsystems have objects which are closely related. The dependency of these subsystems is established. A detailed analysis of each subsystem leads to identifying the classes, which are a set of objects having similar behavior. Attributes and behavior of the classes are assigned. After establishing relationships between the classes, they are arranged into hierarchies. About one hundred major classes have been identified and designed to achieve the desired behavior from FLEX. The programming language used is C++.
Inverse Methods and Advanced Statistics in Well-Test Interpretation
Authors: Domski P.S. , Roberts R.M. , Avis J.D. 
Published: December 2007

Abstract
A new approach to quantifying parameter uncertainty has been implemented in the numerical welltest simulator GTFM. The method incorporates inverse techniques, advanced statistical analysis, and probabilistic techniques. The approach is holistic in that it accounts for uncertainty introduced at all stages of the testing and analysis procedure. The methodology expands upon accepted methods by giving greater emphasis to model assumption diagnostics and parameter uncertainty.

Approach
Model assumption diagnostics are used to distinguish between competing flow models. Candidate flow models are evaluated based on the distribution of residuals between the measured data and the model response. A flow model is accepted if its residuals are normally distributed and discarded if the residuals deviate from the normal distribution.
Typically, parameter uncertainty from pressure-transient tests is analyzed using a discrete sensitivity analysis in which a single parameter is varied while keeping all other parameters constant. More recently, inverse techniques have focused on the estimation of confidence intervals which put bounds on the values of fitting parameters. This approach is limited by the assumption that there are no correlations among fitting parameters. and that non-fitting parameters are known perfectly.
For our new probabilistic-based approach, joint-confidence regions are calculated to quantify the fitting-parameter uncertainty resulting from parameter correlation. For non-fitting parameters. distributions are assigned, sampled using a Latin Hypercube sampling routine, and an inverse procedure performed for each set of sampled parameters. This process results in a distribution of joint-confidence regions for the fitting parameters (Fig. 1), which in turn is an expression of uncertainty in the non-fitting parameters. The new approach also makes it possible to graphically display the correlations between fitting and non-fitting parameters for sampled populations.
Forward simulations using parameter combinations from Figure 1 result in virtually no change in the goodness-of-fit of the simulations to the data (Fig. 2). This approach to quantifying parameter uncertainty differs from other approaches in that the simulated fit shows no degradation within the parameters uncertainty range because correlations between parameters is not neglected.

Conclusions
Uncertainty in fitting-parameter values can result from uncertainty in the conceptual flow model, data noise, correlations among fitting parameters, and correlations among fitting parameters and imperfectly known nonfitting parameters.
P. 267
Mathematical Model for Immiscible Displacement Honouring Hysteresis
Authors: Bedrikovetsky P. , Marchesin D. , Ballin P. R. 
Published: December 2007

Abstract
To describe two-phase displacement with hysteresis we use the Buckley-Leverett model with the imbibition, drainage and scanning fractional flows. Mathematical theory for the initial-boundary non-self-similar problems is developed. Structure of solutions is presented together with the physical interpretation of phenomena.
Analytical solutions for the injection of the water slug with the gas drive and for the sequential injection of water and gas slugs with the water drive are obtained. The solutions show that the hysteresis decreases the gas flux in the case where the drainage relative permeability is lower than the imbibition one, which is a positive effect for the WAG injection.
Environmental Performance Indicators With Emphasis On ISO Development And Application In Oil Industry
Authors: Refsnes Karin , Kjelaas Anton G. 
Published: December 2007

Abstract
A set of preliminary specific environmental indicators reflecting significant environmental aspects for the company has been developed. The choice of final indicators will be based upon the company's own priorities and interpretation of stakeholders interests and environmental impacts. The selected indicators are relative whereever possible. Indicators are identified mainly in the operational area and the management area. Some indicators are also proposed within the external impact area. Indicators in the operational area focus on emissions to air (CO2, NOx, VOC, CH4), energy, discharges to sea from drilling, production and pipelines, waste generation, accidental releases and disposal of platform installations.
Characterization and Flow Modeling of a Heterogeneous Carbonate Reservoir in Daleel Field, Oman
Authors: Abbaszadeh Maghsood , Koide Naoki , Murahashi Yoya 
Published: December 2007

Abstract
This paper presents applications of deterministic and geostatistical reservoir characterization methods to the heterogeneous carbonates of the upper Shuaiba formation in Daleel field, Oman. High resolution reservoir descriptions based on the integration of logs, core, pressure transient tests, geology and seismic data are constructed; and properly upscaled for use in reservoir simulation models in history matching of field performance data. Deterministic descriptions utilize three and six layer models to assess the impact of layering heterogeneity on reservoir performance. Conditional geostatistical methods of SGSIM and SISIM with and without explicit modeling of geology generate fine-scale realizations of porosity and hydraulic flow units, which are then used to construct permeability and initial water saturation distributions. Permeability heterogeneity is upscaled to coarse-scale simulation gridblocks by an improved upscaling method based on an upstream-weighted interblock transmissibility algorithm.
The study shows that detailed and concise reservoir descriptions result in history matches that are more consistent with a variety of measured data. Generally, geostatistical techniques combined with geology and proper upscaling of permeability heterogeneity yield best results without artificial alterations in various fluid and rock properties. Although acceptable history matches could be obtained with less detailed reservoir descriptions, these required modifications to fluid and rock data beyond reasonable ranges, illustrating the need for detailed reservoir characterization.
An Integrated Study of the "S" Structure: A Case Study in Offshore Abu Dhabi, UAE
Authors: Lyon T. A. , Azer S. R 
Published: December 2007

Abstract
This paper is a case study of the S structure and is drawn from an integrated study involving interpretation of a 3D survey acquired in 1992. The S structure, located offshore Abu Dhabi, is a relatively low relief feature discovered in 1970. To-date nine wells have been drilled on the structure. The major oil reservoirs are in the Thamama (Lower Cretaceous) and Arab (Upper Jurassic) litho-stratigraphic units. The prime reason for acquisition of the 3D seismic was to better quantify the structural uncertainties. The results of the study have been used to plan future drilling locations and estimate their likely impact on uncertainty reduction.
The low relief of this structure makes depth conversion an important issue. Layer cake and single layer depth conversions were evaluated. The velocity models for the overburden were determined using a combination of well data and stacking velocities. The uncertainty in velocity determination has been estimated in order to allow the generation of minimum and maximum structural cases.
Paleo-stfucture maps were generated in order to study the evolution of the S structure. The paleo-reconstructions were derived from a combination of the 3D seismic, 2D seismic and the available well control in the sub-regional area. A detailed geological layering scheme derived from core analysis, thin sections and log correlation was integrated with the structural interpretation via geocellular modeling software.
The integrated model was used for sensitivity analysis, volumetrics and visualizing the reservoir description.
Seismostratigraphic Interpretation of Lower Thamama/Hahshan in SE Abu Dhabi
Authors: Landmesser P. , Saydam A. S. 
Published: December 2007

Abstract
Seimostratigraphy, areal distribution, and depositional environment of the Early Cretaceous age Lower Thamama/Habshan carbonate depositional sequences in the SE part of Onshore Abu Dhabi were studied using seismic, VSP, and well log data. Sequence boundaries were determined from the seismic data by extracting wavelets and establishing accurate correlations between the wells and the seismic data. The Global Eustatic sea-level curve and seismostratigraphic concepts were utilised to define four depositional sequences in Lower Thamama/Habshan, and predict their environment of deposition and lithology.
Water Shut-Off Case History Using Through – Tubing Bridge Plugs; October Field, Nubia Formation, Gulf of Suez, Egypt
Authors: Borling D. C. , Powers B. S. , Ramadan N. 
Published: December 2007

Abstract
Through-tubing bridge plug (TTBP) water shut-off (WSO) workovers in the October Field have resulted in an average incremental initial production increase of 2500 bopd per job. Average water cut (WC) was reduced from 55% to 16%. Seventy-eight WSO workovers have been completed since December 1991. Technical and economic success approach 90%. Just under $4.8 million dollars has been spent for an average cost of $61,500 per job. Costs paid out in less than two days using a normalized $13 per barrel crude price. Based on results achieved during the past 4.5 years, these WSO workovers establish the October Field as a notable and on-going case history for lower zone water control.
Water production from the October Field has gradually increased during the past decade. As a result, steeper production declines and gas lift operational problems developed. Based on reservoir characteristics, lower zone water was isolated using TTBP's conveyed by way of portable mast electric line units. A dump bailer was used to place a 14 foot cement cap over the TTBP to provide a permanent pressure seal. After a 24-hour shut in cement cure period, wells were almost always returned to production at a significantly higher oil rate and dramatically reduced WC. The cost of a rigless TTBP WSO workover is much less than conventional rig deployed WSO work which averaged over $500,000 per job. Prior to December 1991, rig WSO's were the only method used in the October Field. Hence, rigless WSO workovers have become vital for cost control. Rigless WSO work has also become a useful reservoir management tool for maximizing oil production and minimizing water production thereby conserving reservoir energy and optimizing lift gas.
Accuracy of SORw and SORg Monitoring in a Middle East Carbonate Reservoir
Authors: wiltgen Nick , Al-Merikhi Sultan , Al-Othman Ibrahim 
Published: December 2007

Abstract
Accurate knowledge of oil saturation and its distribution is essential for any reservoir being considered for redevelopment or for secondary and tertiary operations. Determination of oil saturation forms the only rational basis for prediction of recoverable oil reserves and it is critical in the selection, design and economic evaluation of an oil-recovery process.
As technology advances, more of this oil will come within our reach. However, it is essential that we understand the reservoir involved so that proper, economically viable technology can be applied. Thus, the importance of residual oil saturation (SOR) which in turn is the basis for the estimation of remaining oil-inplace.
Five techniques to determine remaining oil saturation are currently used. They are coring, logging, chemical tracers, reservoir engineering studies and pressure transient tests. Normally, two or more of these methods are used together and the data evaluated as a whole since each technique has its own advantages and limitations. When evaluated together, a clear understanding of the total reservoir can be obtained.
Conventional logging tools and procedures have been used extensively for many years for determination of reservoir and fluid properties. Although SOR determinations normally require a higher degree of accuracy than is commonly achieved by conventional logging methods, the incentive to use logs for SOR measurements remains high. They are often cheaper and easier to use than is the case for other methods which are currently available for measuring SOR.
Oil Lift Curves Automation
Authors: Alkhatib Fatime 
Published: December 2007

Abstract
An automated tool that facilitates the utilization of oil lift curves (well head flowing pressure versus rate) is essential in order to obtain consistent and accurate lift results efficiently in E&P companies.
This paper describes the method used for implementing such a tool and how it integrates with other related information systems and software packages. It explains how these techniques can be applied in some reservoir and production areas to achieve the best well performance and make future predictions.
The theory employed in generating lift curves is based on locating the intersection between a well's Inflow Performance Relationship (IPR) and a Vertical Flow Performance (VFP) curve. It returns the flow rate and Bottom Hole Pressure (BHP).
IPR depends on reservoir pressure and a well's productivity index.
The VFP curve is generated from ECLIPSE or PROSPER analysis software package at specified values of the well's tubing head pressure, water fraction, gas fraction and artificial lift quantity.

Background
The business cycle starts when the daily oil allowables for all Well/Strings are defined at the beginning of each month by the Reservoir Section and sent to the Production Section. Consequently, the corresponding daily required well head flowing pressures (WHFPs) are manually derived at the office from the latest available Lift Curves initially generated by the Reservoir section. After the implementation of the derived WHFPs at the Field's site, the measured WHFP for each well/string is introduced to the oil allocation business process. The corresponding daily well/string estimated oil rates are also manually obtained from the same Lift Curves. At the end of the month, measured WHFPs and estimated oil rates are sent to the Reservoir Section. Data is revised and finalized by referring to the latest available lift curves in order to use, it in calculating the daily allocated oil rates. Lift Curves are updated by both parties from Production Flow Test Results to fit within the latest test points. On the other side they are used by Well Testing Section as a measure for accepting or rejecting Production Flow Tests. This depends on the location of the oil rate Vs WHFP point measured by the test, if it lies within the general trend of the latest Lift Curve or not.
P. 648
Resistivity Measurement in Anisotropic Horizontal Carbonate Wells
Authors: Al-Riyami A. , Boyd D. , Dajani N. 
Published: December 2007

Abstract
Conventional resistivity tools run in horizontal wells give misleading readings in highly anisotropic formations. These tools are designed to read beyond the invaded zone to obtain true resistivity of the formation. While this design feature is an advantage in vertical or deviated wells, it leads to errors in anisotropic horizontal wells where the tools are affected by neighboring layers. Conventional shallow resistivity measurements would not give true formation resistivity because of mud filtrate invasion.
In horizontal injector wells with zones of actual water saturation exceeding 60%, logging with conventional resistivity tools resulted in calculated water saturation of less than 30%. Production testing of the formation and changing casing setting depths are parts of the consequences of the unexpected low water saturation. Four different resistivity tools were ran in a well to investigate their relative responses.
The logging while drilling Geosteering Tool (GST*) was used for the first time in the Middle East to determine Rt of a horizontal well. The tool is shallow reading with the resistivity measurement located at the bit to minimize the effect of invasion. This resulted in a realistic water saturation of 70 – 80% compared to 20 – 30% obtained from conventional tools. Model simulation of the readings of both conventional tools and GST confirmed the field measurements.
For drill pipe conveyed application in horizontal wells, the Azimuthal Resistivity Imager (ARI*) provides 12 directional readings around the tool. Eliminating the adversely affected directional values allows proper Rt determination.
The paper will compare the results of the Azimuthal Resistivity Imager, Geosteering Tool, RESISTIVITY AT BIT and conventional tools. Modeling demonstrates the different response of electrical tools in the vertical versus horizontal plane. The paper will highlight the advantages and limitations of each resistivity tool particularly in horizontal anisotropic carbonates.
Classic and High-tech Tools for Improving Reservoir Behaviour Understanding – Example from an Offshore Abu Dhabi Field (UAE)
Authors: Lapointe Philippe , Bellorini Jean , Petricola Mario , Mahmoud Akbar 
Published: December 2007

Abstract
In order to improve oil recovery from the main oil producing reservoir of an offshore Abu Dhabi field, two gas injection pilots have been tested. To explain their relative performances, a combination of classic tools (cores, electrical logs) and high-tech tools (DSI, FMI, CT-Scan) as well as 3D seismic have been used to further investigate the reservoir anisotropy in one of the pilot area.
The logs indicate the presence of a fracture system. The full comprehensive core versus log calibration allows to extend the results found to the non cored intervals. The combination of the classic and high-tech tools leads to a better understanding of reservoir behaviour and heterogeneities.
Improvement of Wellbore Injection Profiles In Stratified Reservoir Using Polymer Treatment
Authors: El-Hadidi S. , Dabbouk C. , Falade G.K. , Al-Ansari F. 
Published: December 2007

Abstract
The main focus of this paper is the applications of polymer treatment in controlling injectivity profiles and the improvement of the conformance of the near-wellbore injection profiles. Reservoir high permeability zones causing distortions of water injection profiles at the wellbore, and the possible existence of layer barriers were identified using conventional investigation tools such as Open Hole Logs, Production Logging Tools, Formation Micro Scanners.
A polymer screening procedure was put in place so that appropriate polymer formulations for use as agents for reducing fluid mobility in the high permeability zones at the wellbore can be identified. The use of these polymer formulations facilitated the improvement of near-wellbore conformance of injectivity profiles.
The success or failure of field application or the polymer treatment program was ascertained by using a monitoring program which combined the application of the Production Logging Tools with well test analyses.

Introduction
The presence of high permeability streaks and fractures is a common occurrence in stratified carbonate reservoirs. If these reservoirs are subjected to patterned waterflooding operations, it is not uncommon for the highly permeable zones to accept most if not all of the water injected. This tends to distort the injectivity profile at the wellbore and raises the possibility of an eventual poor reservoir coverage and sweep efficiency. Therefore, a successful water-flood project necessarily demands a clear understanding of reservoir characteristics with a view to identifying the incidence of high permeability streaks, channels, and layer barriers so that adequate remedial actions that can reduce their adverse effects of water-flood performance can be put in place. One of such remedial actions which have gained prominence in the recent past, is the use of Polymer1,2,3 and Non-polymer4,5 agent in injection/Production wellbore profile modification.
In this paper, we present the screening, monitoring and evaluation procedures for a successful application of a cross-linked polymer formulation on water injection wells in order to improve the wellbore conformance of injectivity profiles.