bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanosilicas as Accelerators in Oilwell Cementing at Low Temperatures
Authors: Pang Xueyu , Boul Peter J. , Jimenez Walmy Cuello 
Published: June 2014

Summary
Accelerators are important cementing additives in deepwater wells where low temperatures can lengthen the wait-on-cement (WOC) time, potentially increasing the cost of operations. The cement-set accelerators traditionally used for shortening WOC times are inorganic salts, such as calcium chloride (CaCl2). These accelerators are known to have the potentially negative side effect of increasing the set-cement permeability. Nanosilicas, on the other hand, can be advantageous compared with conventional cement-set accelerators because they reduce the permeability and increase the mechanical strength of cement-based materials. For this reason, nanosilicas are known to be particularly good candidates as replacement materials for traditional salt accelerators.
This study investigates the feasibility of the use of different sizes and aspect ratios of nanosilicas as cement hydration accelerators under low-temperature conditions of 59°F (15°C). The nanosilica activities are herein defined through their comparative advantages with respect to traditional accelerators, as well as through the advantages and disadvantages of the different nanosilicas resulting from their various sizes and shapes. Although hydration of oilwell cement is known to be accelerated by the addition of nanosilica, the effects of nanosilica particle shape on cement hydration kinetics has not been previously investigated. The isothermal calorimetry experiments conducted in this study reveal that just as smaller nanosilica particle sizes increase the cement-set acceleration, so do higher nanosilica aspect ratios.
The effects of slurry density on the relative merits of CaCl2 and nanosilicas are also investigated. In regular-weight slurries, the effectiveness of nanosilica acceleration appears to be weaker than that of CaCl2, especially during early ages (≤ 3 days). In lightweight slurries, the effectiveness of nanosilica acceleration can be much stronger than that of CaCl2, especially when mid- to long-term properties (≥ 2 days) are considered. Smaller particle sizes and higher aspect ratios enhance the acceleration effect of nanosilicas. The compressive-strength development of lightweight oilwell cements with and without accelerators was also investigated. Lightweight cements accelerated with nanosilica displayed 7-day compressive strengths up to 136% higher than those accelerated with CaCl2.
Case Study of Weak Signals and Confirmation Bias in Drilling Operations
Authors: Thorogood J. L. , Crichton M. T. , Bahamondes A. 
Published: June 2014

Abstract
The paper presents a case study of the circumstances leading up to a situation where a supposedly vertical well ended up at 14° before the deviation was detected and a correction could be made. This case study illustrates how a relatively routine activity could end up off the plan, and also highlights the impact of weak signals and confirmation bias on the situation.
Process safety has become a focus of attention, with much work done to ensure that organisations are educated and trained in the techniques necessary to avoid catastrophic incidents. Human error has come under the spotlight and "human factors", including non-technical skills, are being included into training programmes, such as well control. However, the language around human factors, and the psychological terms used, such as "cognitive bias", "chronic unease" and "weak signals" are abstract and unfamiliar to the drilling community.
Furthermore, limiting human factors training to well control suggests that non-technical skills are only required during abnormal events. Yet, as this case study will show, developing these skills in general brings benefits in avoiding what might be regarded as "normal" non-productive time incidents.
By describing a real and very recent wells incident, the paper shows how the same set of circumstances can be investigated from several different perspectives and how different conclusions about root cause can be drawn depending on the agenda of the investigator. There is no doubt that no single perspective fully explains what happened in this incident, and why, but traditionally there is little evidence of a human factors perspective being adopted during incident investigations beyond the use of the label of ‘human error’.
The paper will show how, without the benefit of hindsight, the rig team made a perfectly reasonable set of decisions under the circumstances with which they thought they were being confronted. There was evidence in some of the data to suggest that the well was deviating from the vertical, but there were competing pressures on the team for them to disregard the warnings.
While there are certain obvious procedural and technical lessons to be drawn from the event, deeper lessons relate to the difficulties associated with overcoming the tendency to see what is expected and the central role played by leaders to support and commit to the time and cost of precautionary actions.
It is hoped that the paper will encourage the drilling community to look beyond the apparent interpretations of an event to consider why it was that otherwise sensible people did what they did. There are many incidents of this type from which the community can learn at relatively low cost, particularly focusing on the human factors aspects. Yet, the learning from these incidents, and the training to avoid them will, ultimately, develop the skills that will be instrumental in helping teams identify and react to conditions that might otherwise develop into a catastrophe.
Application of In-House Prepared Nanoparticles as Filtration Control Additive to Reduce Formation Damage
Authors: Contreras Oscar , Hareland Geir , Husein Maen , Nygaard Runar , Alsaba Mortadha 
Published: June 2014

Abstract
Nanoparticles (NPs) are currently being studied as a drilling fluid additives especially for application in very low-permeability formations such as shales. Application for conventional permeable rocks is still a subject of discussion. In this work, successful application of in-house prepared iron-based nanoparticles (NP1) and calcium-based nanoparticles (NP2) to reduce filtration loss in conventional permeable media has been experimentally quantified for oil-based mud (OBM) utilizing the high-pressure high-temperature (HPHT) filter press at 500 psi and 250°F. Ceramic discs were used as the filtration medium in this application to test the performance of the NPs and glide graphite as a conventional lost circulation material (LCM) for porous media. These experiments were carried out in the presence of graphite at low and high concentrations. Filtration reduction trends were observed and a reduction up to 76% was achieved. API filter press was also used to investigate the behavior of NPs and graphite under low pressure and temperature conditions (LPLT). NP1 and NP2 at the two graphite concentrations showed a reduction up to 100%.
NP1 gave higher reduction especially at low concentrations under HPHT conditions, while NP2 yielded significant reduction at high concentration under HPHT. These trends were reversed under LPLT, giving a new insight on NPs performance under different pressure and temperature conditions. At HPHT and LPLT, the effect of graphite as a filtrate reduction agent is less significant as the NPs concentration increases. High graphite level had a positive effect on filtration reduction in combination with NP1 at HPHT and LPLT. This was not the case for the blends containing NP2 at HPHT. The effect of NPs and graphite was tested individually showing a different performance compared to the combination of them. Impact of NPs and graphite on rheology was also quantified allowing identification of the more sensitive parameters in the blends. It is concluded from this study that blends containing NPs and graphite can be successfully implemented in OBM to minimize formation damage in porous media.
Using Water to Control Water in Underbalanced Drilling With Nitrogen
Authors: Guo Boyun , Zhang Hui , Feng Yin 
Published: June 2014

Abstract
Underbalanced drilling (UBD) has been recognized as an effective technique for reducing formation damage and finding new discoveries of oil and gas reserves in Southwestern China. However, the excess production of formation water in UBD has hindered the application of this technology in several other regions. The rate of formation water production increases with the gas injection rate that decreases bottom hole pressure. Adding water to the injected nitrogen stream can moderate bottom hole pressure and thus mitigate the water production problem. Optimizing nitrogen and water injection rates to depress formation water production requires accurate prediction of water influx from the formations under various drilling conditions. Currently there is no rigorous method that can be used to perform such a task with adequate accuracy. This paper helps fills the gap.
The NODAL analysis technique traditionaly employed in oil and gas production forecast was introduced to UBD in this work to predict water influx rate and optimize nitrogen gas and liquid injection rates. This paper presents analytical models and solution procedure that are necessary for performing NODAL analysis in nitrogen-UBD design. Inflow performance relationship (IPR) is established on the basis of horizontal well productivity models. The outflow performance relationship (OPR) is constructed using a close-form analytical solution for gas-water-solid 3-phase flow in annular space. It was found that the NODAL analysis technique was able to predict water influx rate with drilling time and thus cumulative water production under the nitrogen-UBD conditions in Sichuan, China. This paper provides drilling engineers a practical method for controlling formation water production in UBD operstions.
External Filter Cake Buildup in Dynamic Filtration: Mechanisms and Key Factors
Authors: Kalantariasl Azim , Zeinijahromi Abbas , Bedrikovetsky Pavel 
Published: June 2014

Abstract
The external filter cake build-up with its final stabilization has been widely reported for waterflooding in oilfields, drilling, produced water re-injection and disposal of produced water in aquifers. The brief overview of the models for cake formation and stabilization is presented. We derive the mechanical equilibrium equation for stabilized cake accounting for electrostatic force and for varying permeate force factor. The main empirical parameter of the model, highly affecting the stabilized cake prediction is the lever arm ratio for the particle on the cake surface. The lever arm ratio was calculated from laboratory cross-flow filtration experiments and from well injectivity data. It was also determined from Hertz's theory for the elastic particle deformation on the solid cake surface. Good agreement between the results validates the developed mechanical equilibrium model with the lever arm ratio determined from the elastic particle deformation theory.
Experimental Determination of the Effect of Pressure on Fluid Loss for Several Fracturing Fluids
Authors: Sanchez Reyes J. , Hutchins R. D. , Parris M. D. 
Published: June 2014

Abstract
Recent studies have offered evidence of unique shear viscosity loss of borate crosslinked fracturing fluids when exposed to hydrostatic pressures, such as those encountered during deep water hydraulic fracturing. This phenomenon can have important implications for proppant transport and for the resulting fracture geometry that needs to be accounted for in fracture design. Another important aspect for fracture design is the fluid loss. Since crosslinked fluids have superior fluid loss characteristics compared to linear polymers, the question arises as to whether fluid loss of borate-crosslinked formulations is also affected by pressure. Fluid loss is a fundamental property in hydraulic fracturing treatments and may dictate the attainable fracture geometry and the retained conductivity. Prior knowledge of fluid loss is also important for designing special additives to overcome the effect of excessive fluid loss.
This experimental study was designed to determine the pressure effect on linear guar and both borate and zirconium-crosslinked polymers. The concept of melt point utilized for the viscosity dependence was incorporated to select fluids. A unique high pressure, high temperature fluid loss apparatus was developed for the experimental testing. Test parameters varied from 160 to 260°F, 1000 to 9000 psi and 0.1 to 10 mD sandstone cores. Spurt and fluid loss coefficients were determined and compared to determine the pressure effect.
The results indicate that fluid loss behavior of fluids comprising borate-crosslinked guar is susceptible to moderate pressure effects. In particular, spurt losses increased with pressure, whereas fluid loss coefficients were independent of pressure. The increase in spurt loss with pressure was more pronounced as the permeability of the core sample increased. Conversely, the fluid loss behavior for linear guar or derivatized guar crosslinked with zirconium was not influenced by pressure. The implications of these findings for hydraulic fracturing applications are also discussed.
Laboratory Evaluation of Formaton Damage Impact of Drill-In Fluid Lubricants in a Low-Permeability Sandstone Gas Reservor
Authors: Osode Peter , Otaibi Msalli , Bataweel Mohammed , Ammari Saleh , Himes Ron 
Published: June 2014

Abstract
Conventional lubricant products composed of different surfactant materials are required in water-based mud for drilling highly deviated and horizontal pay zone sections due to their lubricity associated with torque reduction and better penetration rate. Drill-in fluid (DIF) filtrate-induced formation damage in low-permeability gas reservoirs as a result of water blockage and reduced relative permeability to gas can be significant in view of the high capillary pressure associated with small pore throats. Formation damage risk assessment of the drilling lubricants utilization was therefore considered critical for a low-permeability gas reservoir development project.
Lubricant product evaluation experiments were designed to provide the production impairment potential measurements using Berea and Unayzah sandstone cores with a laboratory formulated DIF and base brine containing 3-4% lubricant by volume and to confirm fluid compatibility with divalent salt (CaCl2) brine. Fluid compatibility and emulsion risk was investigated using mineral oil as the representative formation hydrocarbon fluid. Core flood and dynamic filtration tests were carried out at an estimated bottom-hole temperature of 250 °F and pressure of 1,000 psi for the high-temperature reservoirs while the compatibility tests were carried out at room temperature. Filter cake removal tests were also performed by using high pressure, high-temperature filter press equipment and synthetic disks to determine filter cake removal efficiency with acid brine breaker fluid.
The obtained results from the laboratory study were integrated to evaluate and rank the lubricants based on their assessed formation damage risk. The test results showed that both lubricant return permeability and compatibility tests were important in selecting the best performance lubricant.
This paper discusses the experimental analysis of the formation damage potential of 12 commercially available water-based mud (WBM) lubricants. It also provides an insight into the formation damage (FD) impact of the drilling fluid lubricants on gas reservoir deliverability.
Pressure Pulse Generated by Valve Closure: Can It Cause Damage?
Authors: Zazovsky A. , Tetenov E. V. , Zaki K. S. , Norman W. D. 
Published: June 2014

Abstract
This paper takes a novel approach towards designing and managing the architecture and operating protocol of injection/production system. The shut-in valve positioning and timing of valve closure control the amplitude and frequency of pressure waves generated during shutdowns. The proposed approach provides the means for mitigating the negative impact of water hammer on the integrity of the near wellbore region and provides an idea of the intensity of any cross-flow issues. It is based on a comprehensive model that examines the fast wellbore transients (water hammer) generated by routine or emergency shutdown of injector or producer wells, which can also cause interaction with a near wellbore region of reservoir. The modeling handles the coupling of the conventional transient pipe flow hydraulics with the transient reservoir flow. The decompression wave created by shutting down an injector interacts with the near wellbore region that induces a transient flow back from the reservoir which creates a risk of mechanical damage by dislodging and transporting material with the fluid movement and even result in sand production. The compression wave created by shutting down a producer may induce repeated injection pulses. In both producing and injection cases, multiple cross-flow phenomena can be triggered between formation layers and wells interconnected within the injection or production system. The analyses of these transient phenomena help to potentially quantify the mechanical damage, which may be induced in near wellbore reservoir region, and assess the potential damage risk associated with produced solids.
Selectively Shutting Off Gas in Naturally Fractured Carbonate Reservoirs
Authors: Lozada Miguel , Torres Marcos , Gonzalez Marcela , Garcia Benjamin , Cortes Miguel , Milne Arthur , Miquilena Emilio , Perez Juan M. 
Published: June 2014

Abstract
In the Mexico marine region, gas breakthrough is common in naturally fractured carbonate oil reservoirs. Increasing the gas production reduces crude oil production, and eventually the wells become uneconomic and are shut-in in spite of the remaining recoverable reserves. A typical example is the Akal field, a large fractured 300-to 1000-m thick carbonate reservoir whose permeability varies between 0.3 and 5 darcy. The gas-oil contact zone moves by as much as 8 m/month as the natural gas and nitrogen gas from gas injection moves through the natural fractures and invades the oil zone. This condition results in production decline, reservoir pressure decrease, and oil remaining in the matrix.
Efforts to selectively shutoff the gas have been unsuccessful due to the low-reservoir pressure and high-permeability contrast. When pumping water-based fluids, the increased hydrostatic pressure causes the treating fluid to travel down the natural fractures and away from the gas cap. This condition led to abandoning the gas-invaded intervals and recompleting lower in the reservoir, leaving some recoverable reserves.
To selectively shutoff gas entry in fractured reservoirs, a stable foam-delayed crosslinked fluid was proposed for use by service company. The fluid with a high-foam quality (FQ) and low density rides over the crude and into the natural fractures/fissures, communicating with the gas cap. Once set, the fluid creates an impermeable seal with high-extrusion resistance.
The stable foamed fluid has been successfully used to selectively shutoff unwanted gas production in wells that have been, in some cases, shut-in for several years due to excessively high gas/oil ratios (GOR). Following the treatment, the oil production was restored to the same level as prior to the gas breakthrough.
The success of the initial campaign demonstrated that it is possible to restore the production levels of shut-in wells and recover otherwise lost reserves. This result has a very significant positive impact on the economics of operating the field. The current plan is to extend the use of the technique to other fields.
Filtering Out More Information from Laboratory Screen and Gravel Pack Tests
Authors: Fischer C. C. , Constien V. G. , Vining C. M. 
Published: June 2014

Abstract
Laboratory performance test methods for evaluation of the performance of screens and screens with gravel or frac packs have been relatively unchanged for several years. The small scale sand retention tests generally separate into two types depending on whether the tests are run at constant flow rate or constant draw down pressure. The data from the tests depends upon the laboratory running the tests and what information the client uses in the completion design. More useful information can be obtained by a more complete analysis of the formation material to determine bridging or fines migration tendencies based on ideal packing theory and pore size openings of the formation, gravel and or screen.
Attempts have been made at developing screen performance master curves based on formation particle size and screen opening as well as prediction of screen performance using analytical modeling techniques. Typically, formation samples used in lab testing have particle size distribution (PSD) by laser diffraction or for larger size distributions, conventional sieve stacks. Currently, the PSD information is used to relate the performance of the screens or gravel packs by relating the screen or gravel pack performance to the formation d10, d50 or d50/UC. Often this leads to good correlations for solids production and retained permeability. However, some formation distributions do not easily fall in to predictive performance curves. Often these formations have very small median sizes and are highly nonuniform.
Additional analysis of test data can answer questions such as whether solids production is at the interface of the screen or gravel pack or if fines will migrate through the formation material to continue to produce solids.
This paper will illustrate additional information that can be obtained from small scale tests.
Enhanced Water Flooding Sweep Efficiency by Induced Formation Damage in Layer-Cake Reservoirs
Authors: Zeinijahromi Abbas , Bedrikovetsky Pavel 
Published: June 2014

Abstract
Water channeling through high permeable layers during water flooding results in poor sweep efficiency. There are high costs involved in chemical methods of controlling mobility. Many laboratory studies evidence that injection of water with low salt concentration leads to significant decrease in the core permeability. In this paper the possibility of applying induced fines migration as an enhance oil recovery technique was investigated by modeling of the process. It was shown that the system of equations for water injection with induced formation damage is equivalent to polymer-flooding. It enabled applying polymer option of Eclipse black-oil simulator to model low salinity water flooding with induced formation damage. Investigation of the effect of induced formation damage on sweep efficiency during high salinity and low salinity water flood were the main aims of this study. Eclipse polymer flood model was used to model water injection with induced formation damage in a two layer cake reservoir. Analysis of modeling results showed that induced formation damage was favorable to sweep efficiency. Displacement of oil with low salinity water with induced formation damage resulted in up to 19% extra oil recovery. The sensitivity study showed that improved sweep during low salinity water injection was sensitive to heterogeneity, permeability reduction value, and slug volume. Introducing the permeability dependency of formation damage coefficient reduces IOR effects of induced formation damage during low salinity water flooding if compared with the case of constant formation damage coefficient. Several water flood scenarios with injecting different volume of low salinity water were modeled in order to determine the optimum low salinity slug volume. It was shown that injection of 0.5 PVI of fresh water with high salinity water drive results in similar incremental recovery if compared with continuous injection of low salinity water.