bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Formation Damage of Turkish Southeastern Reservoirs Caused by Drilling Fluids
Authors: Iscan A. Gurkan , Turkse N. V. , Kok Mustafa V. , Strauss Heike 
Published: December 2007

Abstract
One of the major reasons of reservoir formation damage is fines migration during drilling operations. In this paper, three different water-based drilling fluids were used to test permeability reduction ratio with Turkish South Eastern sandstone and limestone core samples using a dynamic drilling fluid circulation system. The drilling fluids were prepared due to API specifications with non-treated bentonite fluid, Polymer-XT and PAC –XC at 11 different differential sticking pressures. The core plugs were saturated with brine after being vaccuumed and initial permeabilities were measured. After the circulation of drilling fluids for two and three hours, return permeabilities were measured from the other end of the cylindrical core plugs. The permeability reduced due to the invasion of the fines particles into the core plugs. The damage ratio concept was used for permeability reduction analysis as the ratio of the difference between final and initial permeability to initial permeability. The limestone core samples gave out the minimum damage ratio with the fluid including PAC-XC at a permeability damage ratio of 32% whereas sandstone core plugs resulted in 46% damage ratio. The highest damage ratio with non-treated bentonite fluid was obtained with sandstone core plug as 78.4 %. The optimum drilling fluid sustaining the least formation damage was determined. An exponential correlation relating damage ratio and filtration pressure was applied to the experimental data. The experimental and correlated results match accurately with each other. The correlation equation was linearized by taking natural logarithms of the both hands sides of the correlating equation. Correlation coefficients for each drilling fluid were determined. High regression coefficients around 0.90 were obtained. This correlation enables the determination of further damage ratios at different filtration pressures for sandstone and limestone core plugs.
Borehole Stability (Geomechanics) Modeling and Drilling Optimization Practices Improve Drilling Curves in Naturally Fractured Shale—A South Argentina Experience
Authors: Fontana Horacio , Paris Martín , Ong Seehong 
Published: December 2007

Abstract
Borehole instability related problems due to massive formation caving in micro-fractured shale resulted in substantial non-productive times (NPT) and accounted for as much as 25% of the total programmed drilling time.
Geomechanics and image log analyses clearly showed the natural/micro fractures were responsible for large cavings. Drilling optimization strategies to mitigate formation caving were focused on:
Reducing mud weight to decrease fluid/pore pressure penetration in fracture planes Use of mud additives to seal-off natural fractures Drilling with downhole motor and stabilizers to minimize lateral vibrations.
Average drilling time prior to implementing these strategies was 14.75 days. The drilling time improved to 8.18 days after the implementation, an improvement of 44.5% with no occurrence of major instability events.
This paper will present a case study from an oilfield in Southern Argentina demonstrating how the assimilation of geomechanics modeling and drilling optimization practices is critical to improving the drilling curves.
Black-Oil Simulations for Three-Component – Three-Phase Flow in Fractured Porous Media
Authors: Geiger S. , Matthäi S. , Niessner J. , Helmig R. 
Published: December 2007

Abstract
Discrete-fracture modeling and simulation of two-phase flow in realistic representations of fractured reservoirs can now be used for the design of IOR and EOR strategies. Thus far, however, discrete fracture simulators fail to include a third compressible gaseous phase. This hinders the investigation of the performance of gas-gravity drainage, water alternating gas injection, and blow-down in fractured reservoirs.
Here we present a new numerical method that expands the capabilities of existing Black-Oil models for three-component – three-phase flow in three ways: (i) It utilizes a finite element - finite volume discretization generalized to unstructured hybrid element meshes. (ii) It employs higher-order accurate representations of the flux terms. (iii) Flash calculations are carried out with an improved equation of state allowing for a more realistic treatment of phase behavior.
We illustrate the robustness of this numerical method in several applications. First, quasi-1D simulations are used to demonstrate grid convergence. Then, 2D discrete fracture models are employed to illustrate the impact of mesh quality on predicted production rates in discrete fracture models. Finally, the proposed method is used to simulate three-component – three-phase flow in a realistic 2D model of fractured limestone mapped in the Bristol Channel, U.K. and a 3D stochastically generated discrete fracture model.
NAF Filtercake Removal Using Microemulsion Technology
Authors: Quintero Lirio , Jones Thomas A. , Clark David E. , Twynam Allan 
Published: December 2007

Abstract
Traditional chemical methods for removal of non-aqueous fluid (NAF) filter cake and internal formation damage use acids, solvents and mutual solvents mixed in clear brine. In some cases, this conventional technology gives good results; but, in other instances, the results can be disappointing.
A new generation of single-phase microemulsion stimulation fluids has been developed for removal of filter cake and formation damage in wells drilled with NAF systems. The development work included the design of microemulsion formulations, determination of the destruction rate of the filter cake with additives that prevent massive completion fluid losses, and evaluation of return permeability for injector and production wells.
The driving mechanism of this technology is to obtain a near-zero free energy state between the novel microemulsion and the NAF filter cake or damaged formation face which promotes incorporation of the oil into the microemulsion and spontaneously reverses the wettability of the filter cake particles, disaggregating them so they are no longer damaging. The laboratory results described in this paper show that the novel microemulsion design delays its spontaneous action long enough to permit well completion operations without experiencing massive losses to the formation. Permeability data obtained demonstrate that this new technology is highly effective for enhanced water-injection and productivity.
Proven Synergistic Approach in Well Cementing Across Thief Zones: East Venezuela
Authors: Tranquini N. , Soto J. , Reveth V. , Prato L. , Williams H. 
Published: December 2007

Abstract
Drilling operations for several operators in East Venezuela are increasing in complexity each year. Many challenges are encountered while drilling across weak formations with considerable variability in lithology and pore pressure. A narrow drilling window between formation pore and fracture pressures has become one of the main concerns for the operator. Primary cement placement faces similar challenges when placed across weak formations.
New producing zones are currently being targeted in deeper sandstone formations and a variety of loss circulation issues are encountered. For example, in the Tacata field, lost circulation is occurring across a series of depleted zones located above the producing zone. In the Orucual field, losses were observed immediately below the producing zone. From the wells observed in this study, losses were observed most frequently under slim-hole conditions and low fracture pressures. In these wells, combinations of demanding well and formation parameters have made it more difficult to achieve successful cement placement. Minimizing losses during cement placement, achieving predicted top of cement (TOC) and reliable zonal isolation are current challenges in East Venezuelan fields.
The need to improve conventional lost circulation approaches during well drilling and cementing was determined by service company and operator field experience and dynamic cement placement simulations. A high performance light weight (HPLW) slurry was recommended along with an engineered fiber material (EFM) to avoid losses by reducing the hydrostatic pressure in the annulus and artificially increasing the fracture pressure of the thief zones during placement.
From several case histories, the synergy between HPLW and EFM approaches resulted in improved zonal isolation, less reservoir damage and cost savings by avoiding remedial cementing and non productive time (NPT).
Trust-Region Approach To Find Constants of Bourgoyne and Young Penetration Rate Model in Khangiran Iranian Gas Field
Authors: Bahari A. , Seyed A. Baradaran 
Published: December 2007

Abstract
Up to now, authors have proposed several drilling rate models. Bourgoyne and Young model represents a general relation between penetration rate and some drilling variables. In this model, there are eight constants, which are dependent to the formation type and must be found from previous drilling data. Bourgoyne and Young recommended multiple regression method to solve these eight unknowns but this method is limited to the number of data points and recommended ranges for drilling parameters. In this research, by writing a computer program, three other mathematical methods were applied on nine wells data of Khangiran gas field to find each formation constants. Results of applied four methods were compared to each other and it was found that trust-region method is the best mathematical method to find Bourgoyne and Young penetration model constants and in many situations, results of other three methods were not meaningful. Since, this method has not limitations of recommended method, it can be applied easily to predict penetration rate when e few data points are present and when drilling parameters are not in the recommended ranges.
Analyzing Transient Pressure From Permanent Downhole Gauges (PDG) Using Wavelet Method
Authors: Shi-Yi Zheng , Xiao-Gang Li 
Published: December 2007

AbstractReservoir pressure monitoring during its production life is to evaluate its performance to ensure the effective extraction of hydrocarbon from the reservoir. Continuous reservoir monitoring offers a window of prospects to increase well productivity, while reducing operating costs through an improved and more accurate well performance. These are achieved through analyzing the long term, real time, dynamic transient pressure obtained from Permanent Down-hole Gauges (PDG), which will provide input and vital information for improving the existing reservoir model for flow simulation.Reservoir monitoring during field development can amplify the understanding of the reservoir depletion, compartmentalization, and efficiency of water injection, also the presence of any flow barriers (such as activated fault). On this basis, reservoir management can be more accurate and realistic.In contrast to the data obtained from the traditional well test such as DST, pressure data from PDG is large in quantity (long term up to six years), noisy, multiple phase flow and multiple rate. The key for the analysis of such data set to extract reservoir information is to develop a technique in handling the data, i.e. to make the data analyzable but not losing the true information contained in the data.This paper presents techniques using wavelet transform method for such purpose. These have been developed recently through an industry sponsored research Project. The procedures include PDG data visualization, de-noising, smoothing and "break point" (due to drop of rate and well shut-in) identification through analyzing field examples provided by the sponsors. After this process, transient pressure data (extracted drawn-down and build up) can then be analyzed using current traditional methods and software. The analysis results such as skin factor and reservoir effective permeability can be evaluated in a time lapse fashion to reveal information about the dynamic changes of the reservoir.
Evaluation of In-Situ Generated Acids for Filter-Cake Cleanup
Authors: Nasr-El-Din H. A. , Al Moajil A. M. , Al-Aamri A. D. 
Published: December 2007

Abstract
Filter cake removal is a difficult task, especially in horizontal and extended reach wells. Water-based drilling fluids consist of xanthan gum as a viscosifier, starch as a fluid-loss control, sized calcium carbonate or salt particles to increase the mud density. Conventional chemical means used to remove filter cake are reactive mineral acids, enzymes, chelating agents, oxidizers, or combinations of these chemicals. Controlling of the reaction rate of the cleaning fluids with the filter cake material is an essential factor that determines the efficiency of filter cake removal.
This study assesses the performance of three acid precursors (esters) that produce organic acids. These precursors produce low-molecular weight organic acids that can dissolve calcium carbonate particles from the filter cake. The rate of hydrolysis of acid precursors can be adjusted to produce a predetermine acid concentration at bottom hole conditions. Enzymes, mainly α-amylase, can be added to these esters to break starch that is present in the filter cake. The slow release of these weak organic acids ensures proper and efficient removal of the filter cake.
Lab studies using static HPHT filter press indicated that the three systems can remove the filter cake efficiently. The rate of hydrolysis was measured for each system, and found to be a function of temperature and type and concentration of the acid precursor. Surface tension measurements conducted for solutions of the three precursors at different temperatures highlighted low surface tension values for the spent acids, which are needed to lift the spent acid following the treatment.
No phase separation or precipitation was observed when the three systems were heated at temperatures up to 250°F. Surface tension measurements indicated that the formic acid system had low surface tension, which will accelerate lifting these fluids from tight formations. Acetic and lactic acid systems had much higher surface tension, and a suitable surfactant will be needed to reduce the surface tension. The kinetic study indicated the very rapid reaction rate of the precursor of formic acid and a moderate reaction rate in the acetic acid system. The reaction rate of the precursor of lactic acid was in between the two systems and more close to the in-situ acetic acid system.
HPHT experiments showed that formic acid system was very efficient at short soaking times at temperatures of 200 and 250°F. The performance of lactic acid was comparable to formic acid when the soaking time was increased from 4 to 6.75 hrs. The efficiency of acetic acid was much lower than the other two acids. Acetic acid will require much longer soaking times.
Development of New Retarder Systems To Mitigate Differential Cement Setting in Long Deep Liners
Authors: Al-Yami A. S. , Al-Arfaj M. K. , Nasr-El-Din H. A. , Jennings S. , Khafaji A. , Al-Ariani M. , Al-Humaidi A. 
Published: December 2007

Abstract
When cementing liners, the cement must develop compressive strength at the top of the liner before drilling is resumed. If drilling is delayed in order to acquire the compressive strength at top of the liner, it can result in excessive delays on cement (WOC) time which can exceed 24 hours. Cement slurries with conventional retarders often achieve acceptable thickening times under dynamic conditions. Sometimes these cement slurries do not produce rapid compressive strength under static conditions. The aim of this study is to develop optimized retarder systems for cements that are exposed to BHST of 400 °F at the bottom of liner (BOL) and 330 °F at the top of the liner (TOL).
More than ten retarders including lignosulfonate, ethylene glycol, and aromatic polymer derivatives were evaluated to provide extended thickening times for extreme high temperature cement slurries, while having minimal effect on sonic strength development. The lab studies included comparison between various retarders and their performances of thickening time, sonic strength development, free water, fluid loss, rheology, and gas migration control.
Two new retarded systems were developed. The first system is used for non-latex cements for wells that do not show indications of gas or fluid flow. The second cement system includes latex and is recommended for cases where there is potential for gas migration. The new retarder systems were effectively applied in the field. The paper will address lab studies that led to the development of new retarders.
Evolutionary Optimization of Oilfield Development
Authors: Túpac Y. J. , Faletti L. , Pacheco M. A. C. , Vellasco M. M. B. R. 
Published: December 2007

Abstract
This work presents the development and evaluation of a hybrid intelligent system to optimize oil fields development. This system employs the following techniques: evolutionary algorithms to optimize the positioning and characteristics of wells in a reservoir; distributed processing to perform simultaneous reservoir simulations; function approximation models as simulator proxies; and quality maps to use some reservoir information to improve the optimization process.
This work represents the first stage in the application of modern methodologies for the analysis of alternatives of oil field development under uncertainties, where no uncertainties are considered. In this sense, the optimization consists in finding wells positioning, type and geometry in a delimited petroleum field, in order to maximize the NPV of alternative, considering some technical constrains as the minimum wells distance and maximum wells trajectory.
The problem approached in this work is considered of up most importance and it is recognized as a complex optimization problem, since the benefit of the option to develop an oil field depends on investments which in turn depend on the alternative chosen. The combination with other aspects makes this problem even more complex, yet properly optimized by Evolutionary Algorithms.
A Pore-Scale Network Modeling Study of Gravitational Effects During Solution Gas Drive: Results From Macroscale Simulations
Authors: Bondino I. , Long J. , McDougall S. R. , Hamon G. 
Published: December 2007

Abstract
Although experimental work for solution gas drive processes is routinely carried out and interpreted for the purpose of defining critical gas saturations and relative permeability data, developing a thorough understanding of the results to facilitate confident application to the field is a hard task. Unfortunately, existing macroscopic models are unable to reproduce or take into account several different features of solution gas drive experiments. For example: (i) the impact of outlet boundary conditions upon the formation of saturation gradients, and (ii) transitions between different flow regimes (disconnected immobile gas, disconnected mobile gas, continuous gas flow) that are characterized by different pore-scale dynamics. These features can be considered using pore-scale modeling techniques. However, such microscopic applications, even in the few cases where they are refined enough to include viscous or gravitational forces, have perhaps their greatest limitation in the number of pores that can be simulated. This consequently makes it virtually impossible to simulate flow regimes that are not capillary dominated at an appropriate physical length scale.
In this work a pore scale network modeling approach is presented which is capable of reproducing gravitational effects during oil depressurization through simulation in samples of macro-scale height. The models used comprise several hundred thousand pore elements. The primary objective is to fully simulate the physical height of routinely used laboratory samples, in this way reproducing the real scale and pressure dependent balance of forces: this allows us to show how the ratio of gravity to capillarity changes in relation to the rates of depletion (bubble densities), the rock, the fluid properties and the scale of the sample, and how this contributes to affect relative permeabilities and critical gas saturations. In particular it is shown that relative permeabilities can be predicted according to the particular flow regime operating during a given experiment (dispersed and/or continuous). Moreover we show that flow is largely determined by the size and density of gas clusters, whether originating from nucleation or from break-up of larger structures during migration. Furthermore, the ways in which different saturation gradients can develop over the length of a sample and the effects of the outlet boundary conditions upon such gradients are explained. The results are compared to available experimental data.
Cryogenic Scanning Electron Microscope Analysis: An Aid to Formation Damage Assessment
Authors: Denniss E. , Patey I. T. M. , Byrne M. 
Published: December 2007

Abstract
In order to evaluate the risk(s) of formation damage from well operations, laboratory core flood tests are commonly performed to closely mimic wellbore conditions. Analysis is required on the core samples in order to identify formation damage mechanism(s) which may be difficult due to the microscopic scale, opacity of rock and fluids. An already established approach of using cryogenic scanning electron microscopy (CryoSEM) at cryogenic conditions would be advantageous to observe the fluids contained within the pores of core samples to help identify formation damage mechanism(s). Other analysis (e.g. X-rays, acoustic velocity, nuclear magnetic resonance imaging) although useful fail to offer the same level of detail. This paper illustrates the method(s) to obtain the required detail by using additional techniques in conjunction with CryoSEM analysis this is referred to as "CryoSEM technique" from here on. In the past ten years CryoSEM has been revived in conjunction with the developed techniques which enables direct imaging of rock, pore space and fluids. Although quite commonly used and referenced in other papers there has never been a comprehensive description of the CryoSEM technique and its current abilities.
This paper describes in detail the CryoSEM technique and outlines some of the core sample preparation techniques and analysis procedures developed. The use of the CryoSEM technique in the description of critical formation damage mechanisms will be described. Examples of the use of CryoSEM as an aid to interpretation of formation damage mechanism(s) will be presented with some case histories with associated of formation damage mechanisms never previously observed will be presented.
The advantages and disadvantages of CryoSEM and other techniques will be discussed and the authors will also present some potential future developments in this area.
The Value of Oil and Gas Price Forecasts
Authors: Jablonowski C. , MacAskie R. 
Published: December 2007

Abstract
This paper develops a decision-analytic model to value commodity price forecasts in the presence of futures markets. The method is applied to a data set on crude oil prices. We find that to be valuable, forecasts must be accurate at predicting both gains and losses, and that there are positive and diminishing marginal returns to forecast value from improvement in key measures of accuracy. We also find that forecast value is specific to user class, and that value is unique to specific users within the class.