bluuebunny/crossref_metadata_2025 huggingface dataset:
Creep and Rupture of Graphite-Epoxy Composites
Authors: Soliman F. Y.
Published: January 2012

Long-term loading can have a significant effect on the performance of aerospace composite structures. The size of this effect depends on the type of composite used, the fiber orientation within a particular composite, and the imposed stress and temperature levels. Test data for graphite-epoxy composite under undirectional state of stress and controlled temperature environment are presented. The behavior of specimens of different lamina orientation tested under identical conditions was compared. The stress situation and temperature level are the most influential parameters on the creep deformation of the material, being greatest where the reinforcing fibers are not aligned in the direction of the load application. A relation between time to rupture, temperature, and stress level was shown and compared to other composite systems. The results show the detrimental effects of stress level, time, and temperature on the strength and deformation. Based on these data, the behavior under long-term loading could be extrapolated from reasonably short-time tests composite materials, fiber composites,
Tungsten Alloy Fiber Reinforced Nickel Base Alloy Composites for High-Temperature Turbojet Engine Applications
Authors: Petrasek D. W. , Signorelli R. A.
Published: January 2012

The potential of tungsten-2 percent thoria, 218 tungsten, and tungsten-1 percent thoria wire reinforced nickel-base superalloy composites for turbine bucket applications was evaluated based on stress-rupture strength, oxidation, and impact resistance. The results indicate that refractory metal alloy fiber-superalloy composites have potential for turbine bucket use based on the properties measured. Composites were produced having stress-rupture properties superior to conventional cast superalloys at use temperatures of 2000 and 2200 F. The 100 and 1000-h stress-rupture strength of the composite at 2000 F was 49,000 and 37,000 psi, respectively. A few thousands of an inch of matrix or cladding material was found to be sufficient to protect the fibers from oxidation at 2000 F for times up to 300 h. At 300 F and above the impact resistance of the composite compares favorably with that of superalloys.
Structural Evaluation of Long Boron Composite Columns
Authors: Goodman J. W. , Gliksman J. A.
Published: January 2012

Boron filament-epoxy composite tubes were evaluated for use as long column members in a spacecraft. Struts, 8 ft long and 3.2 in. in diameter, were designed, fabricated, and tested. After evaluation of test results, three-ply and four-ply laminates were selected to satisfy design load requirements of 5000 and 7000 lb., respectively. These designs were 33 and 45 percent lighter than 6061-T6 aluminum tubes with the same column design load. Effects of eccentricities were considered for column design as well as theoretical Euler buckling and local crippling failure loads.
Fracture Processes in Fiber Composite Materials
Authors: Tetelman A. S.
Published: January 2012

The process of fracture in homogeneous and anisotropic composite materials involves three steps : (1) the initiation of a microcrack, (2) the stable growth of this microcrack under increasing load, out to macrocrack size, and (3) the unstable propagation of this crack at a critical stress level. The conditions for each of these processes are reviewed for homogeneous materials and then discussed in detail for fiber composite materials. The conditions for fracture initiation by fiber cracking depend primarily on the length and diameter of the fiber, their perfection, the fiber modulus, the test temperature, and the degree of interaction of the fiber with the surrounding matrix. Matrix and interface strength depend primarily on temperature, strain rate, and interfacial void content (for resin matrices). Unless the matrix is extremely strain-rate sensitive, premature fiber fracture does not lead to instability, and the composite strength is determined primarily by the average fiber strength. Several mechanisms for increasing the matrix toughness are discussed. The toughness associated with unstable, longitudinal crack propagation in composites then is considered in terms of fiber content, matrix toughness, interfacial bond strength, and matrix shear strength. It is shown that in certain composites the toughness decreases with increasing fiber content, and consequently maximum load carrying capacity is achieved at a particular fiber content Vf*, that increases with decreasing crack length. In other systems, particularly those containing cold-drawn metal fibers, both toughness and ultimate strength increase with fiber content.
An Exploratory Study on Assessment of Gingival Biotype and Crown Dimensions as Predictors for Implant Esthetics Comparing Caucasian and Indian Subjects
Authors: Patil Ratnadeep , van Brakel Ralph , Mahesh Kavita , de Putter Cornelius , Cune Marco S.
Published: January 2012

Gingival biotype and crown dimensions may be important predictors for the esthetic outcome of surgical procedures. However, the visual distinction between “thick” and “thin” biotype may not be a suitable predictive parameter of surgical outcome. Intraoral photographs of 73 Indian and Dutch subjects were matched with respect to age and gender and were used to determine the gingival biotype (subjective assessment) and crown dimensions (objective assessment). Intraobserver and interobserver agreement was determined for subjective measurements (Cohen's kappa), and the error of the method was calculated for the objective measurements (Dahlberg formula). Intraobserver agreement for the subjective assessment of gingival biotype was adequate (κ = 0.49–0.60), but interobserver agreement was poor (κ = 0.10), whereas the error of the method for objective assessment of crown dimensions was small. The mean crown width-length angle is smaller in Dutch as compared to Indian subjects in this sample (P < .05). Crown dimensions may be a more quantitative approach and could become a future norm to predict outcomes of implant restorative and surgical procedures, bearing in mind that cross-cultural differences may be present.
Dental Implants: Early Versus Standard Two-Stage Loading (Animal Study)
Authors: Rismanchian Mansour , Bajoghli Farshad , Gholamreza Tabakhian , Razavi Mohamad
Published: January 2012

Direct bone formation on the implant surface is a treatment goal in implant dentistry. It was always thought that a healing period of 3 months for the lower jaw and 5–6 months for the upper jaw was required for osseointegration to occur. Recent studies, however, show that with the early loading protocol, osseointegration is possible as well. The goal of this study was to evaluate clinical, histologic, and histomorphometric parameters of implants with early loading protocols and implants that did not undergo the early loading protocol. In this experimental study, the first to the fourth premolar teeth were extracted from the lower jaws of 3 dogs. After a healing period of 3 months, 12 BioHorizons internal implants 4.5 × 10.5 mm were placed in the mandible of the dogs. The implant stability quotient (ISQ) was recorded. After 3 weeks, half of the implants were exposed, and after recording ISQ, polycarbonate crowns were placed on them and occlusion was adjusted so that there was no contact in centric occlusion and no lateral movement with the opposing teeth. After 3 months, the ISQs were recorded for all the implants. Bleeding upon probing and pocket depths were measured for the early loading implants. All the implants were removed using a trephine bur, and cross-sections of 150 μm were prepared, from which the bone implant contact (BIC) and the type of bone around them were obtained. Statistical analysis was conducted with independent t test, paired t test, and repeated analysis of variance. The BIC for the early loaded group was 46.17% ± 12.89%, and for the unloaded group was 44.4% ± 10.45%. This difference was not statistically significant (P = .811). The ISQ for the implants in the early loaded group (before they were removed) was 71 ± 7.35 and that of the unloaded group was 66.75 ± 11.86 .These differences were statistically insignificant. With regard to the result of this study, and the fact that the 2 groups showed no statistically significant differences in a number of major aspects, such as BIC and ISQ, it seems possible to load implants with an earlier than usual protocol with no adverse effects on implant success. It is necessary, however, to follow certain protocols for this type of loading.
Osseointegrated Dental Implants in Growing Children: A Literature Review
Authors: Mankani Nivedita , Chowdhary Ramesh , Patil Brijesh A. , Nagaraj E. , Madalli Poornima
Published: January 2012

Edentulism is usually associated with the aging patient. However, total or partial tooth loss also affects young individuals, mainly as a result of trauma, decay, anodontia, or congenital and acquired jaw defects involving the alveolar processes. For elderly patients, the use of oral implants has become an accepted treatment modality for edentulism, and most of today's knowledge regarding implants is based on such practice. There has been hesitation to perform implant therapy for growing children; hence, few children to date have been provided with implant-supported construction. Consequently, little is known about the outcome of the osseointegration procedure in young patients, and until now, only a limited number of case presentations have been reported. This article reviews the current literature to discuss the use of dental implants in growing patients and the influence of maxillary and mandibular skeletal and dental growth on the stability of those implants. The literature review was performed through Science Direct, Wileys Blackwell Synergy, PubMed, Google, Embase, Medknow publications, and Springer for references published from 1963 to 2011. It is recommended to wait for the completion of dental and skeletal growth, except for severe cases of ectodermal dysplasia.
The Possibility of Replacing OBMs with Emulsified Glycol Mud Systems in Drilling Low-Pressure Zones of Iranian Oilfields
Authors: Chegny Sajjad Jafary , Tahmasbi K. , Arsanjani Niloofar
Published: January 2012

With increased concerns over the environmental issues regarding the use of oil-based mud (OBM)s, drilling companies in Iran are moving towards implementing less harmful water-based fluids. Due to low toxicity to the environment, effective shale inhibition and considerable cost savings, water-based glycol muds have the highest prospects as alternatives to OBMs in Iranian oilfields. However, designing water-based muds for drilling low-pressure shales may involve a compromise between mud weight optimization and overall environmental and economic advantages offered by these systems.

The present study will focus on optimizing the weight of a glycol mud by emulsifying oil in the system and comparing its performance, environmental compatibility and cost with OBMs used in drilling low-pressure zones in Iranian oilfields. Properties of glycol solutions in the presence of oil were also evaluated.

An emulsified glycol mud and an OBM with densities of 60 PCF were prepared and compared for their rheology and shale recovery. The shale recovery tests were conducted using shale samples from Maroon oilfield. Possible effects of contamination on the performance of the system were also studied. The glycol system was then treated to recover its diesel content.

Overall, the laboratory data were convincing. With very low filtration rates, the emulsified glycol system is a candidate to replace OBMs in reservoir sections. Shale recoveries were comparable to those of OBMs. Compared with a similar OBM, considerable cost savings can be made and the system is more environmentally friendly. However, rheology was more difficult to control and the system was susceptible to contamination.
Casing Failures in Cyclic Steam Injection Wells
Authors: Wu Jiang , Knauss Martin E. , Kritzler Torsten
Published: January 2012

Casing failure rate is high in steam injection wells and especially in cyclic steam injection wells. The high casing failure rate in such wells is related to the high casing temperature elevation from steam injection. Casing failures varies from casing ID restriction (including buckling and/or collapse) to casing parted (including leak and/or hole). This paper presents a modeling and analysis on casing temperature elevation, casing thermal stress/strain, and casing failure mechanisms in steam injection wells, with comparing with previous casing failure field-data from a Chevron steam injection project. It shows that high thermal axial compressive stress/strain can cause casing hot-yield and is attributed to casing ID restriction (including buckling and/or collapse), and high thermal axial compressive-tensile stress/strain alternation in cyclic steam injection can cause casing fatigue and is attributed to casing parted (including leak and/or hole).

Casing strain-based design seems needed for steam injection wells to take into consideration of casing hot- yield due to high thermal axial compressive stress/strain and casing thermal axial compressive-tensile stress/strain alternation on cyclic steam injection operation. Casing hot-yield and fatigue analysis approach presented in this paper may be used on casing strain-base design for steam injection wells to reduce casing failures, with selecting proper casing grade and weight to reduce casing hot-yield and casing fatigue.
Determination of Recovery Factor in the Bakken Formation, Mountrail County, ND
Authors: Clark Aaron J.
Published: January 2012

An accurate value for recovery factor in the Bakken shale is needed for estimation of ultimate recovery. Published estimates of recovery factor in the North Dakota region of the Bakken vary greatly and examination of historical production from this region reveals that very few published recovery factor estimates are accurate. In this paper, recovery factor for the Bakken shale in Mountrail County, ND, was determined using three different methods. The first method involved review of the literature and an examination of recovery factors historically used by companies operating in the area. The second method was based on material balance, while the third method was based on decline curve analysis. Results from all three methods were integrated and indicate that the most likely value for recovery factor in the Bakken shale is approximately 7%. In the absence of more definitive performance data, these results can be used by companies to estimate ultimate recovery and to help make investment and development decisions in the Bakken shale.
Horizontal Well Placement and Completion Optimisation in Carbonate Reservoirs
Authors: Leung E.. , Nukhaev M.. , Gottumukkala V.. , Samosir H.. , El-Fattah M. Abd , Ogunsanwo O.. , Gonzalez A..
Published: January 2012

Horizontal wells provide increased reservoir contact than conventional vertical wells but present another set of production challenges particularly with respect to imbalanced fluid inflow along the wellbore. This paper will describe the importance of wellbore and reservoir characterization, modelling and practical operational experiences to maximize recovery in a carbonate environment using logging while drilling (LWD) measurements to design reliable and effective completion equipment to manage production. Due to the fractured nature of carbonates and high heterogeneity contrast with the matrix, it is imperative to balance inflow and delay the production of more mobile fluids through the installation of passive inflow control devices (ICD) and swellable packers. Near wellbore steady state and numerical reservoir simulation is particularly important for preliminary design and justification of completion technology. The latter can indicate regions of by-passed oil and areas of high water saturation providing horizontal well infill opportunities. The analysis of real time LWD is essential for well placement but also the characterization of the near wellbore to identify areas of high fracture density and where fluid losses have occurred, to design an appropriate completion tally to maximize production. The availability of adjustable ICDs at the wellsite offers the opportunity to perform this task to fine tune the lower completion design before running in hole. The modelling workflow and operational procedures of optimizing well placement and ICD completion design will be described through carbonate field installations.
Pilon Field After 70 Years - Challenge, Strategy and Economic Viability To Continue Developing A Mature Heavy Oil Field Through Available Technologies, Geoscientist and Engineering Practices
Authors: Balza B.A.
Published: January 2012

Over the last 15 years, operators in the oil industry have used new technologies and field strategies, which have brought opportunities for maximizing the Net Present Value. For example, through drilling drainholes or revisiting existing wells, using MWD-LWD techniques for having a better control hitting the target, and Concentric Coiled Tubing practices for cleaning wells up, additional production is gained. This practice has been demonstrated by Lagoven, S. A. in Pilon Field, when it was subsidiary of PDVSA, drilling 69 reentries, horizontal lateral bore of 1200 feet, from 1993 to 1998, with an exceptional performance of the drilled formations for the medium radius application.

How revitalize Pilón Field through drilling new drainholes and also cleaning up potential wells, which essentially are plugged by sand, was the focus of this project. The actual contribution of the field is just over 14,000 BPD and after making part of the reservoir management processes others 19,000 BPD have been projected in the short term through 44 new wells intervention. That process implicated to understand their geological setting checking the geocellular model, recovery mechanism, past reservoir performance and recent fluid flow patterns, wellbore diagram and integrity, allowing to make a prediction of production for the further 10 years.

In addition, economic considerations were carried out considering not only well intervention but also surface facilities in order to deal with the high volume of unwanted fluids. Eventually, sensitivity analyses were done demonstrating that the worse scenario is having oil price lower than $17/bbl. On the other hand, the critical point would be availability of rigs and CCT unit in the market.
Utilizing Lase Drilling: A Step Forward in Environment Protection
Authors: Jegarluei S. Ghadami , Moazeni A. R. , Habibi E.
Published: January 2012

In the recent decades using laser in drilling operations was limited and unreliable in some extent because of the problems in its way and some limitations in its using. These problems cause some uncertainties in using laser and lots of defiance could be seen in front of this technology. But it can be remembered when the idea of replacing cable tool drilling with rotary table drilling was proposed by some researchers there was such kind of resistance. But persisting in their idea caused a revolution in drilling technology by these technology introducers. Drilling mud is one of the basic materials which is used in drilling industry while drilling a well. Also water based mud is less dangerous in aspect of environmental damage but it is unavoidable using oil based mud in shaly formations. Using laser instead of available drilling technologies can replace air with common drilling fluids and reduce environmental damages considerably. Also it can reduce non-productive time due to omission of drill pipe, increasing penetration rate and reducing specific energy significantly. In these paper advantages of laser drilling would be considered in comparison with conventional drilling methods. Also role of laser drilling in reduction formation damage and environmental damage in one of Iranian south west formations would be notified.
Synthesis of Wax Inhibitor and Assessment of Squeeze Technique Application for Malaysian Waxy Crude
Authors: Halim N. , Ali S. , Nadeem M. , Abdul Hamid P. , Mohd Tan I.
Published: January 2012

Highly paraffinic (or waxy) crude oil can cause significant problems in the pipelines due to wax–oil gel blockage resulting from the precipitation of the wax components. Once blockage of the pipeline occurs and flow ceases, the pipeline flow cannot be restarted with the original steady state operating pressure but instead requires significantly higher pressures to restart the flow. Due to this, it is important to maintain the oil at a temperature above its natural pour point.

The incorporation of chemical products known as wax inhibitors and pour point depressant (PPD) reduce the pour point and viscosity of oil. This paper introduces an indigenously synthesized wax inhibitor from the hydrophobically modified polybetaines (zwitterionic) family for treating waxy crude A located in Peninsular Malaysia. The synthesized wax inhibitor had been evaluated as flow improver, crystal modifier and pour point depressant.

The wax inhibitor coded CRODDA-AA, works efficiently since it can reduce the pour point of waxy crude A by 12°C and the viscosity about half of the original value at 1000 ppm concentration, as well as lowering the yield stress by 8 Pa at 51°C. In order to assess the use of the CRODDA-AA wax inhibitor for squeeze applications, a core flood study was conducted to determine its adsorption capability onto formation. A formation damage study was also conducted to ensure that there is no formation damage coupled with the injection of wax inhibitor. It was found that wax inhibitor CRODDA-AA can be retained in the formation up to 88.5% without significant formation damage. As a next step, it is planned to run the core flood and wax inhibitor release tests to refine the design of squeeze treatment.
Study on Gas Channeling Characteristics and Suppression Methods in CO2 Flooding for Low Permeability Reservoirs
Authors: Wang Rui , Lv ChengYuan , Lun Zengmin , Yue Xiangan , Zhao Renbao , Wang Haitao
Published: January 2012

This paper shows the close relation between the displacement effects and reservoir properties in CO2 flooding for low permeability reservoirs. Low permeability reservoirs are characterized by tight matrix, strong heterogeneity and developed fractures. With the increase of CO2 injection rate, the CO2 viscous fingering gets worse in low permeability homogeneous reservoirs. While for low permeability heterogeneous reservoirs, the increase in displacement differential pressure contributes to the enhanced oil recovery in less permeable layers. The moderate increase in effective pressure is conductive to improveing the oil recovery in matrix. The displacement effect and CO2 channeling can be improved through the adjustment of injection-production parameters in CO2 flooding. Additionally, the interaction among CO2, oil and brine can improve the water-oil viscosity ratio. The gas viscous fingering can be weakened. The temporary performance of oil-water emulsion band formed in carbonate water can plug high permeability layers, and the production capacity of low permeability layers can be enhanced. The compound gel system in the sour environment of CO2 can plug large gas-channeling paths, restrict gas channeling and enlarge the sweep efficiency.
Mechanical Earth Model (MEM): An Integrated Study in Low-Fracture-Gradient and Depleted Fields to Improved Cementation (Case Study)
Authors: Sondang Jaka , Irawan Gondo , Sehang Andry , Permana Dian , Wibowo Satrio , Wisanti Lia
Published: January 2012

A depleted reservoir in the Tapian Timur field in South Kalimantan, Indonesia, is located at 1,400-mTVD with a 400-psi formation pressure. Drilling through it presents potential threats to operations, including lost circulation during drilling and cementing and borehole instability. Two wells previously drilled and completed in the area suffered long NPT due to stuck pipe and bad cement bond quality. Even though the field has been explored and developed for 43 years, a thorough study of the reservoir characteristics was never done. Improper knowledge of a reservoir like this one cause’s unnecessary lost time during drilling and poor zonal isolation of the target zone, can potentially jeopardize the economic feasibility of a project.

For this reservoir, a geomechanical study was applied, and a mechanical earth model (MEM) was built. The model utilized multidisciplinary data across the field (drilling and logging data, core, pressure history) to evaluate wellbore stability and improve drilling practices. The MEM study provided key recommendations for the drilling process and cementing operation. Decisions made based on the study include changes in casing point, mud-weight optimization, and utilization of high-performance lightweight slurry with fiber.

A subsequent well drilled in the area applying the recommendation from the study was drilled and completed faster. Cement bond logs from the section also indicated excellent zonal isolation across the reservoir. The recommendations from the study are currently integrated into the standard operation procedures.
Novel Gauge Extension Optimizes Conventional Drill Bits for Superior Performance with Rotary Steerable Systems
Authors: Stroud Daryl , Lines Liam , Barton Steven , Sanchez Hector
Published: January 2012

Bit gauge length has been a hot topic for several years, particularly when assessing optimal length for rotary steerable systems (RSS). Discussion has not just been about the length; aspects such as geometry, tapering, width, cutting elements, have all complicated the matter further, as well as the fact that different RSS tools require different configurations for optimal balance between steerability, stability, durability, and drillability.

This paper describes a joint engineering approach in identifying gauge configurations for the latest generation of RSS that utilizes point-the-bit technology. The project included systematic testing at a purpose-built, full-size drilling test facility. This has enabled a direct comparison of the directional response, hole quality and drill string vibration to be made for the various gauge configurations tested.

The testing included use of a novel gauge extension stabilizer. This unique stabilizer provides a method of extending the gauge length of the bit on the rig floor, giving a wider variety of bit selection choices for specific applications. The gauge geometry of the stabilizer provides a 360 º continuous circumferential contact with the borehole, thus providing improved borehole quality and reducing vibration.

Field trials proved that the addition of a gauge extender to a short gauge bit can dramatically improve hole quality when used with point-the-bit RSS. The closer gauge hole significantly reduced the severity of downhole vibration and backward whirl. Concerns over lack of steerability, in conjunction with high levels of stick slip and torque, proved unfounded.

This study proves that a short gauge, short length bit, when combined with a gauge extender, can be a suitable replacement for a long gauge bit; affording the improved lateral stability required by the RSS whilst allowing operators the freedom to select a widely available short gauge bit with the correct cutting structure.
An Improvised Method for Determining Reservoir Rock Porosity Cut-off with Support of Laboratory Mercury Injection Data
Authors: Widarsono Bambang
Published: January 2012

Porosity cut-off is a major key parameter in evaluation of reservoir dimensions. Through the use of this parameter formation rocks regarded as ‘reservoir(s)’ are distinguished from ‘non-reservoir’ ones. This makes determination of this parameter to have a direct impact on estimations of reservoir volumes and in turn volumes of hydrocarbon accumulation. Error in the determination may influence commerciality of the hydrocarbon accumulation. Traditionally, determination of porosity cut-off values is made through relationship between rock porosity and permeability. Although some suggested the use of supporting data such as clay volume and porosity types or computational methods such as artificial neural network, this method is often regarded as unsatisfactory due to different intrinsic features between the two. Relationship between rock pore throat size – obtained from mercury injection on core samples – and permeability is on the other hand more direct in nature. This study actually attempts to integrate this more theoretically consistent relationship into the old porosity – permeability relationship. The integration is essentially made through multi-variable regression analysis using data from eight (4 sandstone and 4 limestone) oil and gas fields in Indonesia. Results from the study have shown significant improvement in porosity – permeability relationship resulting in more reliable porosity cut-off estimates. The method, which procedure is presented in this article is hoped to have helped petrophysicists in reducing and overcoming high uncertainties in estimating porosity cutoff.
Optimal Use of Flow-Diverting Joint in Underbalanced Gas Drilling
Authors: Guo Boyun , Zhang Zongren , Gao Deli
Published: January 2012

Use of natural gas and nitrogen as drilling fluids has been considered as an innovative technique for drilling hard formations, loss of circulation formations, coal bed methane zones, and low-permeability gas reservoirs to improve drilling performance and reduce formation damage. Drilling complications have been reported owing to the use of high-gas injection rate required for hole cleaning. These complications include hole washout, hole deviation, and ice-balling (frozen) of bit. This paper reports a new technique to solve the problems associated with the use of high-gas injection rate. It involves using a new type of flow-diverting joint (FDJ) at the shoulder of drill collar to partially bypass gas flow into the annulus between the drill pipe and open hole. This technique allows for the use of high-gas injection rate to carry drill cuttings while reducing the gas flow rate through the drill bit. As a result, the gas velocity in the drill collar-open hole annulus is maintained at a safe level to avoid hole washout. The reduced flow rate through bit also minimizes wellbore enlargement at bottom hole, which reduces the tendency of hole deviation. In addition, the reduced gas flow rate through bit minimizes the Joule-Thomson cooling effect at bit which is believed to be responsible for ice-balling of bit. This paper presents a method for selecting the optimal FDJ port size based on system configurations. It optimizes the distribution of the injected gas flow between the lower and upper annular sections. Calculation procedure is described and a design example is illustrated with a computer program output. Sensitivity analyses with the computer program show that the FDJ to bit-nozzle area ratio is directly proportional to the annulus area ratio, and the bypassed flow rate fraction remains constant as drilling progresses.
Smart EOR Screening, Breaching the Gap between Analytical and Numerical Evaluations
Authors: Moreno Jaime , Gurpinar Omer , Liu Yunlong
Published: January 2012

Hydrocarbon’s exploration is reaching global frontiers pressuring for near and long term solutions to increase oil production from the existing assets. Field development drivers are shifting towards maintaining a high production plateau while effectively sweeping the reservoir hydrocarbon to maximize recovery. Enhanced oil recovery offers a substantial alternative to improve recovery of green and mature fields by means of enhancing pore level sweeping in the reservoir.

While the principles of EOR schemes are not new; field implementation has been scarce and, as a consequence the physics governing the displacement process have not been completely understood. Highly heterogeneous reservoirs in particular pose a challenge for EOR. Geological features influence the EOR agent advancement and their influence needs to be considered on the early stages of EOR screening. A successful EOR selection requires a detailed understanding of the reservoir governing forces together with the reservoir architecture to maximize reservoir conformance.

This paper focuses on these issues by proposing a new methodology to aid the EOR selection, addressing the influence of vertical and lateral heterogeneity at the early stages of the screening and providing guidance to maximize contacted oil in the reservoir by reconciling the reservoir driving forces and geological architecture. A comprehensive analysis of the present and past reservoir conditions is used to determine the EOR best suited for the reservoir; data mining, optimized numerical and analytical simulations are used to further substantiate the decision and help mitigate uncertainties by incorporating present and past EOR experience during the selection process.
Optimization of Hole Cleaning and Cutting Removal in Vertical, Deviated and Horizontal Wells
Authors: Mohammadsalehi M. , Malekzadeh N.
Published: January 2012

As measured depths and displacements in horizontal and extended-reach (ERD) wells increase, good hole cleaning and cuttings removal is essential to avoid associated problems with poor hole cleaning like pipe sticking, abnormal torque and drag, drop in ROP and etc. So far, some methods and models have been developed that can assist in finding the minimum flow rate required to efficient removal of the cuttings during drilling operation. One of them is Larsen’s model that predicts minimum flow rate for cuttings removal from 55 to 90 degrees of inclination. Another model, Moore’s correlation, is used to find the slip velocity of the cuttings in vertical wells (0 degree inclination). This paper presents a detailed combination of Larsen’s model and Moore’s correlation to predict and calculate the minimum flow rate for cuttings removal for all range of inclinations namely from 0° to 90°. The resultant flow rate is compared with flow rate that maximizes the bit horsepower or bit jet impact force (optimized flow rate). If the flow rate for cuttings removal is less than the optimized flow rate, the latter is selected. But if the flow rate for cuttings removal is higher than the optimized flow rate, then drilling fluid rheological properties should be changed until the optimized flow rate becomes higher than the flow rate for cuttings removal. This procedure gurantees achievement both optimized drilling hydraulics and good hole cleaning. To illustrate the usability of this approach whitin all inclination ranges, three points in vertical, deviated and horizontal parts of a horizontal well are chosen and the optimization procedure performed and presented.
Greener EOR: Employing Cogeneration to Improve the Energy Efficiency of Thermal EOR projects
Authors: Welch Mike
Published: January 2012

Thermal EOR technologies such as Cyclic Steam Stimulation, Steam Assisted Gravity Drainage and Steam Flood can be extremely energy intensive, requiring the combustion of fossil fuels to produce the steam required, with the resulting emissions of carbon dioxide and other pollutants. Newer technologies such as Solvent Extraction may also require the injected medium to be heated to maximise oil recovery from the reservoir.

EOR projects tend to generate the heat and power required in separate facilities, with the electricity often being supplied from a remote central generation facility. In many cases it may be possible to integrate a cogeneration plant into the EOR process. Using a single facility, a locally available fuel can provide both the power and heat required for the project, therefore optimising global energy efficiency and achieving very high overall fuel efficiencies, usually in excess of 75%, while helping to reduce the global CO2 footprint of the Oil & Gas industry. In most cases the heat produced by a Cogeneration plant is a byproduct of electricity production, but it is also possible to utilise waste heat or waste gases from some processes to produce useful energy.

There are numerous different ways to configure a Cogeneration plant depending on the type of fuel available and the ratio between power and heat required by the project. This paper will examine some of the different Cogeneration configurations and fuel options using Gas or Steam Turbines, or a combination of both, that could be applied to a thermal EOR project.

Gas Turbine combustion can also play a significant role in the overall environmental as well as economic benefits of cogeneration in an EOR facility. The use of a wide range of fuels requiring little or no pre-treatment in a Dry Low Emissions combustion system reduces on-site energy consumption and helps reduce emissions to atmosphere of pollutants such as NOx.
Innovative In-situ Reservoir Stress Test Helped to Manage and Optimize Water Disposal under Fracturing Conditions in South Oman
Authors: Msallati S. El , Hammad K. , Priyandoko P. , Cig Koksal
Published: January 2012

One of the major fields in the South of the Sultanate of Oman produces oil at 94% average BSW. All produced water is disposed of without treatment into the same aquifer. The disposed water is injected under fracing conditions and takes place more than 200 m below the lower shale (cap rock) in the sandstone (Fig.1). However the failure of the field’s cap rock could result in oil deferment and the contamination of the overlying aquifer; therefore rigorous risk management is strongly required. Figure 1Depth view of the formations in the field. Green arrows show the mini-frac depths.

Several in-situ stress testing (mini-frac) stations were conducted in the field focusing on lower shale and sandstone formations to evaluate the risk of breaking the cap rock and above formations associated with the water disposal. However this was very challenging using the normal ways of testing; hence the stress testing application was conducted with an oil based viscous fluid. The viscous fluid allowed accomplishing the objectives in higher permeability and shale zones. The oil based viscous fluid facilitates initiation of a fracture in highly permeable sandstone formations and reduces the osmosis and plastic behavior effects in shale zones.

The viscous fluid stress testing provides the results required to update the numerical models for each formation by obtaining minimum stress and fracture initiation, propagation, and closure pressures (frac gradients). Moreover the test results will help to build models that can predict fracture growth while injecting water.

This paper will discuss in detail the viscous fluid stress test and how the results can be used to understand the reservoir behavior. Realistic injection forecasts were made possible using commercial fracture simulation software and some analytical and diagnostic methods based on pressure survey and injection volumes history.
Application of CO2 Miscible Flooding on Gao 89-1 Low Permeability Reservoir
Authors: Qin Li Chun , Hailong Li , Yin Xiao Qian
Published: January 2012

Based on a laboratory study, reservoir simulation and pilot test are presented in this paper for CO2 miscible flooding in low permeability with thin interbedded reservoir. At beginning, reservoir description of Gao 89–1 is sited, which gives a full view of three-dimensional geological model of the field. Swelling test has been done to examine the variation of oil volume and viscosity with increase of the pressure. Slim tube test has also been conducted to determine the minimum miscibility pressure. It shows that it is much lower than the formation pressure, which can be implemented readily in the field. And long core flooding experiment has also been carried out to make a comparison of the displacement efficient between water flooding and CO2 miscible flooding. Composition modeling with CMG simulation software is applied to optimizing the flooding parameters and formula selection for Gao 89–1 reservoir. With further studies going on, pilot test has been carried out. And the result shows that the oil production rate is increased from 31 tons to 42 tons with five wells as experimental subjects. This paper demonstrates the application of CO2 miscible displacement technique in low permeability reservoir development and exhibits the advantages and prospects of this technique.
Dare to CHOP: Resources Development Cost Holistic Optimization
Authors: Chan Keng Seng , Chong Danny , Othman Mohamad B
Published: January 2012

Cost of hydrocarbon resources development in Malaysia is escalating. Typical overall unit development costs are now ranging from 30 to 50 $/Bbl. With this trend of cost escalating, marginal fields or remaining reserves from brown fields may not be economically developed.

This presentation is first to demonstrate effective cost saving by reducing well count with case studies in thin oil-rim and compartmentalized reservoirs in Malaysia. It then illustrates the feasibility of further reducing the well construction cost by changing the well design culture and production strategy. This entails designing slimmer holes and having monobore well completion design for gas reservoirs, the application of ICD and ICV for enhance commingle production from multilayer reservoirs rather than the designing conventional but complex multiple-strings completion wells. Significant cost saving can also be achieved by improving drilling and completion efficiency. The idea of setting up minimum performance standards for drilling and completion and the resultant well construction cost will also be discussed.

Cost of constructing conventional offshore surface structure to support the reservoir production is relatively 3 to 5 folds the cost of the associated well construction. For marginal fields, an idea of developing smaller FPSO but with the capability of coiled tubing drilling and completion will also be presented.

This presentation is the herald urging a paradigm change of the way we were in developing our resources and encourages cost saving as an integrated engineering effort involving reservoir engineering, well design engineering, well drilling and completion engineering, and production facilities engineering.
Wellbore Stability Analyses for HPHT Wells Using a Fully Coupled Thermo-Poroelastic Model
Authors: Wu Bailin , Wu Bisheng , Zhang Xi , Jeffrey R. G.
Published: January 2012

A significant portion of non productive time can be attributed to wellbore instability during drilling, in particular for high pressure and high temperature (HPHT) wells. Drilling introduces changes to stresses, formation pore pressure and temperature in the vicinity of a wellbore. These changes are fully coupled and interact with one another. Such coupling effects are often ignored in the conventional approach to wellbore stability analysis. A thermo-poroelastic 2D model recently developed at CSIRO considers the full coupling effect on wellbore stability.

This paper presents a study that uses this newly developed model to analyze the wellbore stability for a HPHT well drilled in the South China Sea. The study well encountered HPHT condition in the 8.5" hole section with a formation pore pressure gradient up to 1.95 SG and temperature up to 155 °C. The objective of the study was to gain a better understanding of the transient pore pressure and temperature effects on wellbore stability shortly after drilling, and to evaluate if conventional uncoupled wellbore stability models are adequate for HPHT wells. The main conclusions from this study are a) coupling effect caused by changes in stresses, formation pore pressure and temperature cannot be ignored for HPHT wells in low permeability formations, such as shales; and b) conventional uncoupled wellbore stability models are inadequate in deriving a reliable mud weight window for HPHT wells in early times for low permeability formations drilled underbalanced, but are adequate for formations with permeability in the orders of microdarcies or higher.
Enhancing Oil Recovery through Application of Ultrasonic Assisted Waterflooding
Authors: Mohammadian Erfan , Shirazi Mohammad Amin , Idris Ahmad Kamal
Published: January 2012

When oil production declines due to low displacement efficiency and/or adverse mobility ratio, enhanced oil recovery methods are required to improve the production. Application of high frequency sound waves (also known as ultrasonic waves) as an unconventional enhanced oil recovery method has been point of interest for some decades. However, despite number of researches on the applications of ultrasonic waves, the influencing mechanisms are not fully comprehended. The aim of this research is to experimentally investigate the effects of ultrasonic waves on recovery of waterflooding and to discuss the mechanisms involved in this process. Series of straight and ultrasonic stimulated waterflooding experiments were conducted on a long unconsolidated sand pack and the oil recovery was measured at the end of the experiments. Kerosene and vaseline were used as non wet phase in the system. In addition to that, a series of supplementary experiments were conducted using ultrasonic bath in order to enhance the understanding about contributing mechanisms. The recovery of waterflooding increased by 2–16% was observed as a result of ultrasonic stimulation. Emulsification and viscosity reduction were identified as main mechanisms affecting improvement of oil recovery by waterflooding. The results of this research are expected to enhance the insight about the mechanisms involved in application of high frequency waves and contribute in wider application of this method for enhanced oil recovery purposes.
A Practical Compositional Method for Simulation of CO2 Flooding in Porous and Fractured Petroleum Reservoirs
Authors: Di Yuan , Wu Yu-Shu , Ju Binshan , Qin Jishun , Song Xinmin
Published: January 2012

CO2 flooding is one of the most effective and used methods for enhanced oil recovery (EOR) approaches. The number of CO2 flooding projects has increased rapidly in China and around the world. Compositional simulation is required for evaluating CO2 flooding in EOR operations, especially for miscible or nearly miscible flooding when black-oil simulation is no longer adequate. The simulation method proposed here is a multi-dimensional, three-phase, and compositional modeling approach, which is applicable to both porous and fractured reservoirs. In the model formulation, a generalized multi-continuum approach is adopted to handle flow and transport in naturally fractured reservoirs and the mass flux of each mass component is contributed by advection and diffusion processes. In addition, precipitation of heavy oil components and absorption of CO2 on the solid grains are modeled based on reversible linear or nonlinear isotherms. The governing partial differential equations for conservation of each component are discretized using a finite volume method and the resulting discrete equations are solved fully implicitly by Newton-Raphson iteration. The equation of state (EOS) by Soave-Redlich-Kwong is used to calculate the physical properties of fluids. Research has shown that the flash calculations with EOS in compositional simulation are computationally intensive and may not be reliable at near critical conditions. Therefore, a K-value based approach, improved by Almehaideb et al. (2002), is used for partitioning of oil components and CO2 between oil and CO2 phases. In addition, the laboratory measured oil and CO2 phase compositional data can be used alternatively to account for compositional effect in this model. Two numerical examples are presented to show that the proposed modeling method is efficient for simulation of CO2 flooding processes in EOR operations.