bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimized Nuclear Logging for Fast Drilling
Authors: Helgesen T. B. , Jonsbråten F. , Pepper C. F. 
Published: December 2007

Abstract
Slow data acquisition rates have generally not been a problem for LWD due to moderate logging speeds while drilling. With the recent advances in drilling technology, high logging speeds impact the log quality and, in particular, the nuclear logs. When a detector passes a longer interval of rock for each acquisition period, its vertical resolution is degraded. For azimuthally sectored data, this is even more of an issue, as bedding features within a sample period get blurred.
The objective of the study is to develop a methodology to optimize LWD data acquisition, enabling the E&P company to drill faster and meet its data acquisition objectives.
This paper describes analytical simulations and field tests performed to optimize data acquisition for fast drilling in the Norwegian North Sea. Optimization of data acquisition is described as addressing the trade-off between low data density with accurate measurements versus high data density with less accurate measurements.
Based on nuclear logs acquired in adjacent wells, bed contrasts were defined for zones of interest. Modeling was done to define the minimum acquisition time needed to detect the defined contrasts. Telemetry was designed with adequate resolution for geo-steering, thus saving bandwidth. The impact on memory data accuracy caused by faster acquisition rates was modeled to check feasibility. Field tests were performed to validate the modeling results.
Real-time telemetry accuracy proved adequate and the improved data density provided better definition of bedding features versus standard setup. Memory data contained better vertical resolution, further enhancing bedding features, while maintaining the required accuracy. Understanding all end users' specific data quality requirements is key to an acceptable compromise.
Applying this methodology in the planning phase for other wells ensures all stake holders' needs are considered, and aids the overall understanding of LWD acquisition limitations and highlights the possibilities.
Analysis of MWD Pressure Data During Turbulent Flow and Modeling Implications
Authors: Jachnik R. P. , May R. 
Published: December 2007

Abstract
During the drilling of deviated wells it has been recognized that the drill string can be in some eccentric condition and that this has an effect on annular pressure loss. Previous attempts to quantify how much of the drill string and to what degree of eccentricity it is in within various hole sections have often relied on general assumptions such as fully or partly eccentric. This paper describes a method to more accurately quantify the amount of eccentricity throughout each hole section by use of torque and drag modeling and derivation of a side force plot. This details whether pipe is lying on the side of the borehole (top or bottom) or is crossing over from one side to the other. The pipe body is assumed to be stiff between each tool joint. A simple geometric relationship between drill pipe tool joints and pipe body defines the eccentricity. The length per hole section and geometric eccentricity can then be used either in calculating pressure loss more accurately while in laminar flow or by use of empirical factors to calculate pressure loss during turbulent flow should this be a requirement.
Field data was obtained at the end of a horizontal well drilled in the Norwegian North Sea and input into two propreitary modeling packages. One, a finite element program confirmed the suitability of using the side force plot data derived from Torque and Drag modeling. Hydraulic pressure loss calculations with the second program confirmed the overprediction of annular pressure loss by 20% in this field example if eccentricity is not considered. Using the determined eccentricity and an equation in the literature that applies a factor to concentric pressure loss values it was possible to calculate annular pressure loss values that were within 3% of the measured MWD values.
A Facies-Based Approach to Distribution of Petrophysical Properties in an Aeolian Sandstone Reservoir, Unayzah Formation, Saudi Arabia
Authors: Raba’a A. S. , Heine C. 
Published: December 2007

Abstract
Defining and distributing petrophysical reservoir property within a simulation ready geocellular model is an industrywide dilemma; the result of which has a large business impact on reservoir management decisions. The objective of this study is to develop porosity-to-permeability transforms, multiphase relative permeability and capillary pressure curves for each distinct depositional facies. The key to this process is the ability to recognize each of the four eolian facies and demonstrate that even at deep formation; the original depositional facies controls the petrophysical properties.
Through core and image-log studies, the geologist divided the reservoir into the four distinct depositional facies that comprise a "wet" eolian depositional system: dune, sand sheet, paleosol, and playa. Each facies was distributed proportionately by zone (vertically) and by region (area) in a 3D geocellular model using an object based modeling technique and a wet eolian depositional model. The dune facies is the best reservoir unit followed by sand sheet; together the dune and sand sheet comprise a high proportion of the reservoir gross thickness. Conventional and special core analysis measurements were conducted on hundreds of core samples from three gas wells. The core data were thoroughly evaluated for pertophysical properties, and then grouped by depositional facies. Porosity-to-permeability transforms, multiphase dynamic relative permeability and capillary pressure were derived for each facies. The reservoir properties were then geostatistically distributed within each facies object using the facies and zone specific transforms.
Results showed a quantifiable porosity-to-permeability transform, and corresponding capillary pressure and condensate-gas relative permeability for each depositional facies in the reservoir. This paper shows that by grouping the reservoir into recognizable depositional faceis has significantly enhanced the distribution of reservoir and fluid properties, which were incorporated into a compositional model. This will result in a dependable fluid-flow model that will support investment, reservoir development and reservoir management decisions.
Applying Downhole Fluid Analysis and Wireline-Formation-Testing Techniques in Reservoir Management and Well Completion—Case Studies
Authors: Khalil M. , Maamari K. K. , Jackson R. R. , Cig K. 
Published: December 2007

Abstract
The Gharif and Al Khlata Formations form significant reservoirs in north-central Oman. The reservoirs are multilayered, heterogeneous and highly variable in terms of geometry, connectivity, permeability and fluid properties. Newly drilled wells often show differential pressure depletion between layers, which helps assess lateral and vertical reservoir continuity. However such complexity and reservoir heterogeneity means that conventional pressure-depth plot and pressure gradient analysis of wireline pressure data is not easy, and identification of in-situ fluid density changes can be difficult.
A significant part of formation evaluation within these reservoirs has required the application of downhole fluid analysis (DFA) and fluid identification using a pumpout wireline formation tester. The primary objectives being to obtain a measurement of formation pressures, identification of the formation fluids, capture fluid samples and determination of fluid mobility. Such information is important input for both reservoir management purposes and in optimizing the well completion strategy.
We discuss testing techniques using a modular wireline formation tester equipped with a dual packer and/or probe modules, and latest generation optical fluid analyzers. The tests usually comprise of extended pumpout, drawdown and buildup periods, during which oil-based mud filtrate contamination, and fluid composition are monitored in-situ in real time. The techniques applied include in-situ characterization of reservoir fluid type and composition, gasoil-ratio (GOR), and the use and application of fluorescence measurements.
In this contribution we compare and demonstrate the utilization of data from wireline downhole formation fluid analysis and formation tests, and also their practical application in reservoir management.. The field examples described are from wells mainly drilled with oil-based mud. We present some case studies and discuss how the results from tests conducted in different flow units in individual wells, and arealy across the field in multiple wells, have been used in reservoir management and well completion.
A Comparative Study of Recent Robust Deconvolution Algorithms for Well-Test and Production-Data Analysis
Authors: Cinar M. , Ilk D. , Onur M. , Valko P. P , Blasingame T. A. 
Published: December 2007

Abstract
In this work, we provide a comparative study of recently proposed deconvolution algorithms which were designed to function in the presence of reasonable levels of noise in both the rate and pressure input data. The algorithms considered for comparison are those presented by von Schroeter et al.1,2Levitan,3,4 and Ilk et al.5,6 These works offer robust solution algorithms to the long-standing deconvolution problem and make deconvolution a viable tool to well-test and production data analysis. However, there exists no comparative study revealing and discussing specific features associated with the use of each algorithm in a unified manner. We have independently reproduced the von Schroeter et al. and Levitan algorithms to assess the specific advantages and limitations of each method (as well as the Ilk et al. method), and we provide a comparative study of these algorithms using synthetic and field case examples.
Our results identify the key issues regarding the successful and practical application of each algorithm. In addition, we show that with proper care and attention in applying these methods, deconvolution can be used as an important tool for the analysis and interpretation of variable rate/pressure reservoir performance data.
Characterization of Commingled Reservoir Properties with Production Logs
Authors: Poe B. D. , Atwood W. K. , Kohring J. , Brook K. 
Published: December 2007

Abstract
This paper presents the results of an investigation concerning the development of a reliable and accurate technique for establishing the stabilized deliverability performance of multi-layer commingled systems using multirate production log measurements. Both linear and non-linear systems are addressed in this paper, providing a basis for the analysis of reservoirs exhibiting Darcy and non-Darcy flow, respectively.
Extension of the conventional Selective Inflow Performance analysis is also presented in this paper to obtain estimates of the formation and well completion properties such as effective permeability, radial flow steady state damage /stimulation skin effect, and non-Darcy flow coefficient. In the specific case where the deliverability performance of a vertically fractured well is considered, estimates of the effective fracture half-length and average fracture conductivity may be derived from the analysis. In cases where the multirate deliverability tests are performed under boundary dominated flow conditions, conventional deliverability analysis techniques may also be employed to derive estimates of the reservoir drainage area in addition to the well and reservoir parameters that can be obtained in a transient flow analysis. Applications of the analyses reported in this paper demonstrate the use of the analyses to evaluate the inflow performance measurements of commingled multi-layer reservoirs obtained using multi-rate production logs.
Development of a Novel Delivery System for Ultralightweight Proppants in Conventional Fracturing Treatments
Authors: Ward B. , Beall B. , Cawiezel K. , Wheeler R. 
Published: December 2007

Abstract
With increased utilization of ultra-lightweight proppants, several operational challenges have been encountered. Blending and measurement challenges arise from the relative closeness of the specific gravity of ultra-lightweight proppants to the base fluid, rendering conventional measurement systems inadequate. The use of these ultra-lightweight proppants in slickwater fracturing is further complicated operationally because of the low proppant concentrations used; it is not uncommon to begin as low as 0.5 ppg added1.
The solution to this problem utilizes a pumpable carrier fluid to suspend the ultra-lightweight proppant (ULWP). The concentrated proppant slurry can be prepared at the district and transported to location where it can be pumped "as is", diluted with water or linear gel, or pumped as a foam2. This concept was developed from a previous project that involved offshore and remote location gravel and frac packs. This paper details the development, field testing, and job success of a new generation of ultra-lightweight proppants, utilizing this novel delivery concept in conventional fracturing treatments. This technology will allow companies to conduct fracturing operations with minimal equipment and manpower, and enable hydraulic fracturing to be conducted in small and/or remote locations. It will also allow an increased number of fracturing treatments to be completed in areas where equipment utilization is at a maximum and additional frac fleets are needed.
Geosteering Diagnosis: A New Approach to Monitor the Well Position within a 3D Geological Model
Authors: Thevoux-Chabuel H. , Fejerskov M. 
Published: December 2007

Abstract
With the increasing demand for more efficient drilling operations, the oil industry is searching for new ways of utilizing all data available while drilling. The integration of the realtime drilling information with data from offset wells and the reservoir model is considered of high value for accurate wellbore placement and geosteering.
This paper introduces an original methodology to better understand and analyze the well position within the subsurface and to warn the end user when predefined geological and drilling events are appearing or prognosed ahead of the drill bit. The concept is called Geosteering Diagnosis.
We identify a monitored trajectory as composed of a real-time and a project-ahead section. The bit and the MWD/LWD sensors are monitored objects attached to the trajectory. A number of targeted objects (i.e. horizons, contacts, faults, targets, planned and previous drilled wells trajectories, well and grid properties) are accessible from the 3D geological model. Rules can be defined based on the relationship between the monitored objects and any targeted objects. Various thresholds are used to identify events at the time of the drilling and alarms can be triggered on specific cases.
The Geosteering Diagnosis is applied to a production well in the North Sea. The rules are used to monitor drilling against the predefined geological model. They provide quantitative information, which can be used to either update the geological model, or take actions regarding the course of the well.
Design and Field Testing of a Truly Novel Diverting Agent
Authors: Glasbergen G. , Todd B. , Van Domelen M. , Glover M. 
Published: December 2007

Abstract
The success of all oilfield chemical treatments is dependent upon fluid placement efficiency. In acid-stimulation treatments, the acid should be placed so that all potentially productive intervals accept a sufficient portion of the total acid volume. The same is true for scale-inhibitor squeeze treatments. It is critical for the inhibitor to be distributed as uniformly as possible over the interval of interest.
Various diversion techniques are available to assist in alteration of the injection profile during matrix treatments. Likewise, several computer design programs are available to advise on appropriate diversion techniques and allow numerical simulation of the diversion process and efficiency. Rarely are placement models validated in the field.
Recently, a joint project was initiated to develop a novel fluid-diversion process. This project resulted in a particulate-diversion agent that has several advantages over traditional particulate diverters. Advantages include little or no environmental impact, negligible solubility at surface conditions, controlled permeability of the filter cake or perforation pack, upper temperature limit significantly higher than traditional diverting agents (excluding salt), compatibility with nearly all treatment fluids, diverter degradation at bottomhole conditions to eliminate post-treatment removal, and excellent regained permeability.
The chemical development is not the only unique and novel aspect of this joint development. An extensive field trial was conducted, incorporating multiple step-rate tests, fluid-efficiency tests, treatment-pressure matching, pressure-buildup tests, temperature surveys, and injection profiles. These tests were performed in a 226°F sandstone reservoir at approximately 11,900 ft MD. Testing was performed (1) before diversion, (2) during injection of the diverter, (3) immediately after diverter placement, and (4) finally 1-2 days later to confirm diverter degradation. The pressure-matching techniques used in this study would not be unique in proppantfracturing applications; however, the application to matrix stimulation and chemical placement techniques using both pressure matches and injection profile matches are unique and novel processes.
Navigating and Imaging in Complex Geology with Azimuthal Propagation Resistivity while Drilling
Authors: Bell C. , Hampson J. , Eadsforth P. , Chemali R. , Helgesen T. , Meyer H. , Peveto C. , Poppitt A. , Randall R. , Signorelli J. , Wang T. 
Published: December 2007

Abstract
Reservoir navigation with LWD resistivity has traditionally relied on matching real time measurements with ideal logs. Reservoir navigation engineers initially build one or more resistivity models including all expected resistivity boundaries such as oil-water contact, reservoir to cap rock interface, faults and unconformities. Then, during drilling, they direct the well and update the earth model by matching actual measurements with forward response model data.
Because common LWD resistivity sensors cannot differentiate between an oil-water contact approaching from below and a shale lens approaching from above or from the side, the reservoir navigation engineer fills in the missing information through expertise and local knowledge. In case of complex geology however, such as reservoirs with tilted or rotated fault blocks, multiple fluid contact levels, cross-stratification and shale intrusions, navigation becomes much more challenging and the risk of getting geologically lost is high. In recent years imaging LWD tools were introduced to help reduce the azimuthal uncertainty but they were limited to a few inches in lateral investigation.
A new azimuthally sensitive propagation resistivity tool was recently tested for reservoir navigation and formation imaging in some of the more complex reservoirs of the North Sea. In cases where standard omni directional tool responses would lead to ambiguous interpretations, the azimuthally sensitive tool provided the basis for clear geosteering advice. A new imaging algorithm helped visualize approaching beds much like modern imaging devices, but with a depth of investigation reaching several feet into the formation. At fault crossings, the azimuthally sensitive signal helped recognize the relative movement of the formations on either side of the fault. In other instances where the well was run immediately below the cap rock, deep looking azimuthal propagation anticipated the intersection by several hundred feet. Also, analysis of the detailed deep electrical images brought a more complete understanding of the subsurface.
New Closed-Loop Control System Reduces Risk in Intervention Operations
Authors: McNicol J. , McGurk M. , Pittman G. , Heisig G. , Donadieu B. , Hood J. 
Published: December 2007

Abstract
During well construction activities, measurement-whiledrilling (MWD) technology is applied to transmit sophisticated spatial and petrophysical data from downhole to surface. Used with advanced well construction tools such as rotary steerable systems, MWD technology has enabled complex, even tortuous, well profiles to be created and placed in the reservoir with great precision. However, even on these sophisticated and expensive wells, any well intervention operation process is still controlled using traditional surface-read data such as revolutions per minute (RPM), hook load, torque, etc.
The ability to transmit and use downhole intervention process data in addition to surface-acquired data presents significant potential for intervention process optimization, since modern data acquisition technology close to the tool can provide not only more accurate data, but also important additional parameters not available at the surface. Examples of value-adding downhole intervention process data are bore pressure, annular pressure, weight-on-tool, tension-on-tool, torque-on-tool, RPM, workstring bending and dynamic diagnostics. Additional intervention process information on intervention hydraulics or workstring friction can be obtained by feeding existing engineering algorithms with surface- and downhole-acquired data.
This paper discusses the available downhole well intervention process data and demonstrates by a number of case studies the risk reduction value of viewing these parameters in real time. Furthermore, the paper discusses factors constraining the use of the technology and gives an outlook on future developments in well intervention process optimization utilizing real-time downhole data.
Analyzing Underperformance of Tortuous Horizontal Wells: Validation with Field Data
Authors: Kerem M. , Proot M. , Oudeman P. 
Published: December 2007

Abstract
This paper presents the results of a project, which was initiated for analyzing the inflow performance and inflow distribution of one smart and two problematic conventional, long and tortuous horizontal wells in Brunei.
Following a detailed hydraulic analysis of these wells, a good match with the field measurements was obtained. Simulation results show that the problems in the conventional wells were not as severe as those interpreted from the measurements of distributed temperature sensing systems (DTS). It is also demonstrated that the compartmentalized completion with inflow control valves (ICV) in the smart well has added value, as the well would not be producing from the half of the reservoir section without the smart completion.
Reliability Evolution of Permanent Downhole Gauges for Campos Basin Sub Sea Wells: A 10-Year Case Study
Authors: Frota H. M. , Destro W. 
Published: December 2007

Abstract
This work is related to the reliability engineering, specifically, to the analysis of data lifetime and to the failure modeling of Permanent Downhole Gauges (PDG) in 12 oilfields in Campos Basin, Brazil. The area of failure modeling in association with these systems lifetime is the focus of this study.
The importance relies on the application of a methodology as an alternative to reduce the subjectivity in evaluating the reliability and cost / benefit performance of permanent downhole pressure and temperature gauge systems. This methodology also permits the comparison among the components performance from several manufacturers and service companies. Based on these findings, recommendations have been made to achieve reliability improvements from design stage to service operation.