bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proppant Placement Using Alternate-Slug Fracturing
Authors: Malhotra Sahil , Lehman Eric R. , Sharma Mukul M. 
Published: June 2014

Summary
New fracturing techniques, such as hybrid fracturing (Sharma et al. 2004), reverse-hybrid fracturing (Liu et al. 2007), and channel (HiWAY) fracturing (Gillard et al. 2010), have been deployed over the past few years to effectively place proppant in fractures. The goal of these methods is to increase the conductivity in the proppant pack, providing highly conductive paths for hydrocarbons to flow from the reservoir to the wellbore. This paper presents an experimental study on proppant placement by use of a new method of fracturing, referred to as alternate-slug fracturing. The method involves an alternate injection of low-viscosity and high-viscosity fluids, with proppant carried by the low-viscosity fluid. Alternate-slug fracturing ensures a deeper placement of proppant through two primary mechanisms: (i) proppant transport in viscous fingers, formed by the low-viscosity fluid, and (ii) an increase in drag force in the polymer slug, leading to better entrainment and displacement of any proppant banks that may have formed. Both these effects lead to longer propped-fracture length and better vertical placement of proppant in the fracture. In addition, the method offers lower polymer costs, lower pumping horsepower, smaller fracture widths, better control of fluid leakoff, less risk of tip screenouts, and less gel damage compared with conventional gel fracture treatments.
Experiments are conducted in simulated fractures (slot cells) with fluids of different viscosity, with proppant being carried by the low-viscosity fluid. It is shown that viscous fingers of low-viscosity fluid and viscous sweeps by the high-viscosity fluid lead to a deeper placement of proppant. Experiments are also conducted to demonstrate slickwater fracturing, hybrid fracturing, and reverse-hybrid fracturing. Comparison shows that alternate-slug fracturing leads to the deepest and most-uniform placement of proppant inside the fracture. Experiments are also conducted to study the mixing of fluids over a wide range of viscosity ratios. Data are presented to show that the finger velocities and mixing-zone velocities increase with viscosity ratio up to viscosity ratios of approximately 350. However, at higher viscosity ratios, the velocities plateau, signifying no further effect of viscosity contrast on the growth of fingers and mixing zone. The data are an integral part of design calculations for alternate-slug-fracturing treatments.
Some Phenomena Pertinent to Velocity Logging
Authors: Wyllie M.R.J. , Gardner G.H.F. , Gregory A.R. 
Published: June 2014

Abstract
The main experimental facts relating to an understanding and interpretation of the Continuous Velocity Log are reviewed. Experience shows that the velocity through liquid-saturated rocks primarily depends on porosity, and that the "time-average" formula can be relied on to give the dependence within about 5 per cent. An exception occurs in the case of shallow unconsolidated sands. Data are given for the dilatational and shear velocities through dry rocks under a high confining stress. It is argued that a correction made for pressure increase or porosity reduction with depth in the interpretation of a velocity log is unwarranted because of the many uncertain parameters involved.
The application of Biot's theory is discussed, and illustrated with a numerical example. If tile dilatational and shear velocity in the dry material are known, then the change in velocity on saturating the material with any inert fluid is explicitly expressed in terms of the density and compressibility of the fluid. However, since the dry velocities of rocks in the ground are not known, and their correlation with porosity is small, the practical use of Biot's theory is very limited. As a didactic tool it achieves its greatest usefulness.

Introduction
The introduction of the Continuous Velocity Log (CVL) as a routine logging device is a significant technical feat, but even more remarkable has been its wide acceptance as a tool to solve problems in correlation and to determine the porosities of subsurface beds. Indeed in the latter regard it has been recently described as the best wireline tool now available for the evaluation of porosity. While this statement seems to ignore definite drawbacks in the use of CVL data to calculate porosities, world-wide experience in the interpretation of CVL data by the so-called "time-average" technique has shown it to be extraordinarily successful.
The primary intention in this paper is to review the major experimental facts which must be considered when interpreting CVL data. A secondary purpose is to show how some of these data can be explained by modification of the classic theory of wave motion in continuous matter. The third aim, but by no means the least important one, is to remark on some of the misconceptions which appear to have crept into current interpretation procedures and to emphasize where experimental and theoretical lacunae exist.
Engineering Cementing Solution for Hutubi Underground-Gas-Storage Project
Authors: Zhang X.. , Taoutaou S.. , Guo Y.. , An Y.. , Zhong S.. , Wang Y.. 
Published: June 2014

Summary
Underground gas storage (UGS) is an important segment in China's gas market. Because of the supply-and-demand misbalance of natural gas, the gas in underground storage is made available during the peak winter season. In the west of China, the Hutubi dry-gas field is to be used for UGS with a storage capacity of 4.5 × 109 m3. A total of 37 wells will be drilled with 30 natural-gas-injection/-withdrawal wells, five observation wells, and two water-injection wells. UGS relies on proper wellbore construction and the sealing function of the caprock. The selection of the type of cement is crucial to having a healthy well that will last to meet the gas-storage need of 30 years under high-intensity injection. The gas injection and withdrawal will induce different stresses on the cement sheath and may destroy the seal by either debonding (microannulus) or cracking; an effective cement system is required to prevent the leakage of the gas and flow through the caprock. A specialized cement technology was identified as a solution to UGS and was deployed successfully in the Hutubi field with good results. The cement selected had to meet the pressure and temperature challenges associated with UGS, and a methodology was established to qualify the new sealant. Case histories of three wells illustrate the steps taken in cementing UGS wells in the field.
Novel High-Efficiency Boron Crosslinkers for Low-Polymer-Loading Fracturing Fluids
Authors: Legemah Magnus , Guerin Michael , Sun Hong , Qu Qi 
Published: June 2014

Summary
Boron-based crosslinkers are used commonly to increase viscosity and to improve fluid-loss control and proppant transportability of guar and its derivative fluids. Boron crosslinkers are usually preferred because of their ability to reheal after shearing and their favorable environmental properties. More-efficient crosslinkers capable of crosslinking fluids with reduced polymer loading have always been of great interest, to reduce both the formation and the proppant-pack damage from polymer residues and to reduce overall fluid cost, especially with the reduced availability and higher cost of guar.
Recently, we reported in paper SPE 140817 (Sun and Qu 2011( the synthesis of polyaminoboronates, bulky compounds containing multiple boron sites and capable of interacting with multiple polysaccharide strands to form more complex crosslinking networks at lower polymer loadings than conventional guar fluids. However, to improve the marketability and acceptance of the product, a lower-cost combination of raw materials is sought. In addition, a delaying mechanism to improve the control of the fluid-viscosity buildup can make the product fit into broader applications.
A readily available polyamine was used as the base scaffold, and boron was incorporated by means of intermediate borate formed in the condensation reaction between boric acid and ethylene glycol to replace volatile and highly flammable trimethylborate. New chemistry was developed to produce more-controlled crosslinking. The resulting compound exhibited desired adjustable delay characteristics.
This paper shows the effect of a series of new crosslinkers in terms of delay properties. The testing results of fluids with a 20%-lower polymer loading, crosslinked with the new crosslinker, are reported and compared with those of conventional fluids. Analysis and discussion of the chemistry, crosslinker performance, and economics are presented.
Formation Evaluation with the Wireline Tester - Merits and Shortcomings
Authors: Milburn J.D. , Howell J.C. 
Published: June 2014

Abstract
The wireline formation tester has proved to be a valuable tool for formation evaluation, but some tests still lead to misleading interpretations while others are inconclusive. Longer flow periods and more tests are generally required for evaluation of low-permeability sands. No particular advantages or disadvantages were found for tools with large, small and/or segregated chambers.
The methods of interpretation presently in use have proved to be quite accurate; however, care must be exercised to determine that the conditions required for use of these methods are satisfied and that the tool functions properly. Errors in the measurement or recording of recoveries have probably resulted in many misleading interpretations; simply stating all volumes in the same units would speed interpretation and be helpful in recognizing errors.
A single chart for interpretation of formation test recoveries from all sizes of chambers is presented. The surface pressure is helpful in the detection of a leaky seal, but it should not be used to correct for losses caused by leaks. Water resistivity data may be misleading when used to predict whether a zone would produce water and hydrocarbons or water alone.
The wireline formation tester is a dependable tool for obtaining pressure measurements; however, the estimation of formation permeability from pressure build-up has been found to be qualitative at best.

Introduction
The wireline formation tester was introduced to the industry in 1955 by the Schlumberger Well Surveying Corp. It proved so successful that thousands of tests have been run to date and most logging companies now offer this service. It is a valuable addition to the array of wireline tools currently being used for formation evaluation and is the only one, other than the side-wall sampler, that obtains physical evidence of formation contents.
Uncertainty-Based Approach for Predicting the Operating Window in UBO Well Design
Authors: Udegbunam J.E.. E. , Fjelde K.K.. K. , Arild Ø.. , Ford E.. , Lohne H.P.. P. 
Published: June 2014

SummaryUnderbalanced operations (UBO) are carried out to bypass drilling challenges that could be difficult to resolve by use of conventional drilling techniques. Steady-state multiphase-flow models are used to construct underbalanced-drilling operational windows. These advanced software models are deterministically formulated. It is known that some of the model input parameters, such as the multiphase-flow parameters, friction factors, and reservoir productivity, are subject to uncertainties. Failures to capture these variabilities may introduce some error in the model prediction, resulting in poor well planning and implementation.The purpose of this work is to implement probabilistic modeling of underbalanced drilling by use of a simple steady-state two-phase model. Both predefined uncertain and fixed factors serve as inputs to a pre-existing deterministic model. By applying Monte Carlo simulations, the model predicts outputs that follow a statistical distribution. A sensitivity analysis is conducted to determine the input factor that is most responsible for the uncertainty in the predicted bottomhole pressure (BHP).The results demonstrate that uncertainty modeling can improve underbalanced-drilling design and operations. A more realistic operational window is obtained, ensuring that underbalanced condition is maintained throughout the target section.With a better understanding of uncertainties and the corresponding impacts, well planners can make better decisions regarding well design criteria and safe operational conditions, and avoid huge economic consequences.
Experimental and Modeling Study of Salt Precipitation During Injection of CO2 Contaminated With H2S Into Depleted Gas Fields in the Northeast of the Netherlands
Authors: Bolourinejad P.. , Herber R.. 
Published: June 2014

Summary
Depleted gas fields are among the most probable candidates for subsurface storage of carbon dioxide (CO2). With proven reservoir and qualified seal, these fields have retained gas over geological time scales. However, unlike methane, injection of CO2 changes the pH of the brine because of the formation of carbonic acid. Subsequent dissolution/precipitation of minerals changes the porosity/permeability of reservoir and caprock. Thus, for adequate, safe, and effective CO2 storage, the subsurface system needs to be fully understood. An important aspect for subsurface storage of CO2 is purity of this gas, which influences risk and cost of the process. To investigate the effects of CO2 plus impurities in a real case example, we have carried out medium-term (30-day) laboratory experiments (300 bar, 100°C) on reservoir and caprock core samples from gas fields in the northeast of the Netherlands. In addition, we attempted to determine the maximum allowable concentration of one of the possible impurities in the CO2 stream [hydrogen sulfide (H2S)] in these fields.
The injected gases—CO2, CO2+100 ppm H2S, and CO2+5,000 ppm H2S—were reacting with core samples and brine (81 g/L Na+, 173 g/L Cl−, 22 g/L Ca2+, 23 g/L Mg2+, 1.5 g/L K+, and 0.2 g/L SO42−). Before and after the experiments, the core samples were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) for mineralogical variations. The permeability of the samples was also measured. After the experiments, dissolution of feldspars, carbonates, and kaolinite was observed as expected. In addition, we observed fresh precipitation of kaolinite. However, two significant results were obtained when adding H2S to the CO2 stream. First, we observed precipitation of sulfate minerals (anhydrite and pyrite). This differs from results after pure CO2 injection, where dissolution of anhydrite was dominant in the samples. Second, severe salt precipitation took place in the presence of H2S. This is mainly caused by the nucleation of anhydrite and pyrite, which enabled halite precipitation, and to a lesser degree by the higher solubility of H2S in water and higher water content of the gas phase in the presence of H2S. This was confirmed by the use of CMG-GEM (CMG 2011) modeling software.
The precipitation of halite, anhydrite, and pyrite affects the permeability of the samples in different ways. After pure CO2 and CO2+100 ppm H2S injection, permeability of the reservoir samples increased by 10–30% and ≤3%, respectively. In caprock samples, permeability increased by a factor of 3–10 and 1.3, respectively. However, after addition of 5,000 ppm H2S, the permeability of all samples decreased significantly. In the case of CO2+100 ppm H2S, halite, anhydrite, and pyrite precipitation did balance mineral dissolution, causing minimal variation in the permeability of samples.
Standardising HSE Training Through Delphi
Authors: Tamburro Roberta , Forzan Andrea 
Published: June 2014

Abstract
Training is a vital instrument for developing proactive and responsible HSE behaviours. This is why Saipem decided to adopt a method for standardising HSE courses and to share this within the entire Saipem world through the Delphi Project and Portal.
Delphi addresses dispersion and unevenness in HSE training by providing a continuously updated and well-defined list of courses as well as the four guiding (for the trainers) documents per course: a) Specification containing course contents, duration and purpose; b) PowerPoint Presentation of a course (which may also include a video); c) Trainer Manual which stresses a thematic focus and interactivity through role plays; d) Entry Test and Final Test.
Delphi Portal is open to any Saipem employee seeking information on how to manage or attend a HSE course. Course participants can also download training materials and receive updates on activities planned. In short, a top-down approach is supplemented by the bottom-up attitude which drives the development of Delphi.
With course materials prepared beforehand, the Delphi Portal has helped to optimise quality, time and costs of the trainings provided. Contents, materials and knowledge bases, all of which were previously developed and applied locally, are now shared via the Delphi Portal and are an integral part of the company’s global HSE heritage.
Only by sharing knowledge is possible to improve HSE awareness and performance, and only by training employees in a way that will prevent accidents and pollution while at the same time boosting health is possible to ensure highest product quality and profitability.
A New Guideline Document for Temporary Refuge Testing
Authors: Stewart Cameron , Sheikh Shahmeen , Robinson Chris 
Published: June 2014

Abstract
A Temporary Refuge (TR) provides an important component of safety on an offshore platform and most offshore safety cases attribute high availability and survivability of the TR as a key component in establishing an acceptable risk profile for the installation. The UK Health and Safety Executive (HSE) defines the TR as: "a place where personnel can muster safely in an emergency, monitor and assess the developing situation, and either take control action or initiate evacuation".
The Energy Institute (EI) Process Safety Committee (PSC) recently identified that there was no standard testing procedure available to offshore operators which would allow a uniform approach to TR testing and validation. Different operators and test organisations have different testing methods and validation standards which they apply to determine whether a TR provides appropriate protection. The EI therefore commissioned MMI Engineering Ltd (MMI) to help a dedicated PSC Sub-group write a new guideline for the TR integrity testing.
In writing the guideline the group has liaised with a number of offshore operators and test organisations, and reviewed similar guidance documents which are currently used internationally and in related industries (e.g. building services). From this a testing procedure was developed which brings together the best current practices and is bespoke to TRs in an offshore environment; this forms the core of the new guidance
Unintended Consequences of a Promising Safety Management Leading Indicator
Authors: Veley Carl D. 
Published: June 2014

AbstractSeveral companies operating in the North Sea and elsewhere have utilized a metric based on a corrective action classification system. Historically, that metric was developed by this author (Veley, 2002) and it initially appeared to be a valuable leading indicator for management purposes. It is a semi-quantitative indication of the strength of corrective actions, and that should be directly linked to the likelihood of problems recurring; the stronger the corrective action the less likely the accident is to repeat. However, after trial applications it became clear that when this metric was used to define performance goals it had unanticipated consequences that cumulatively and insidiously caused more damage than the accidents it was intended to prevent. This paper will discuss those unintended consequences and explain why, in common situations, permanent corrective actions can produce harm, while temporary actions produce improvements. Category Matching is an upgrade of that original metric and eliminates harmful unintended consequences of corrective action classifications used alone.
The Governance Of Acceptability
Authors: Muscio Giuseppe 
Published: June 2014

Abstract
The Tempa Rossa oil field is located in the heart of Basilicata, an agricultural region in the south of Italy, which inhabitants belong to a rural culture set in its ways. The project area lies in the middle of three protected areas (national and regional parks), with consequent challenges in terms of biodiversity conservation and environment protection.
To ensure acceptability of Tempa Rossa project, Total E&P Italia - as a responsible operator of an O&G project - considered that structuring the internal governance of all processes impacting the stakeholders and the territory is a key success factor. More specifically, Total E&P Italia considered necessary to implement an internal process for updating and sharing the activities in real time, in order to prevent and manage problems linked to the social and environmental impact on different stakeholders.
To achieve such objectives, Total E&P Italia set up two internal committees. The Acceptability Technical Group (ATG) ensures that Total E&P Italia guidelines and policies are applied in operational activities and identifies and anticipates potential environmental/social issues in such activities. This is the forum for the representatives of the different Total E&P Italia departments, to discuss and find concrete solutions to the identified problems in order to avoid/reduce "non technical risks" (i.e. suspension of operations, lawsuits, etc.). The mitigation measures plan set in place by the ATG is submitted to the second committee (ASC) for validation. The ASC (Acceptability Steering Committee) is the main internal body in charge of decision-making on environmental/social matters, where strategies are defined and decisions on actions/measures proposed by ATG are taken.
Pttep Health Risk Exposure Score, the HRA Improving Process
Authors: Dusadi-isariyavong Asadang , Thongpradit Amornrat 
Published: June 2014

Abstract
PTT Exploration and Production Public Company Limited (PTTEP), the E&P Company of Thailand has applied the principle of Health Risk Assessment (HRA) to all the operating assets since 2006 by using the Risk Assessment Matrix (RAM) as a tool for risk assessment. The RAM applies the 5 scaled health hazard rating and either 5 scaled occupational exposure limits (OEL), or 5 scaled Frequency of Occurrences (FO), in case hazards are not quantitatively measurable, to define the level of risk into 3 levels. The FO is graded according to how often the condition has been known within the E&P industry. When applied to health condition, the FO could be arbitrary and may not provide the accurate assessment.
In 2012 PTTEP has developed the Health Risk Exposure Score (HRES) system which can replace the FO and OEL in the RAM. The HRES comprises the number of exposed persons, the frequency and exposed duration, the industrial hygiene results, proper occupational health trainings, and the availability of PPE/existing control. Each item is weighed and calculated by three points scale. The result is averaged and distributed into 5 ranges to replace the FO and OEL in RAM.
The HRES is tested against the conventional HRA done within PTTEP in 2012. The result showed significant difference of risk assessment level between the two methods, while the HRES provides more objective assessment and requires less specialist’s opinion in HRA process. Thus the HRA process and finding can become standardized among the PTTEP operating assets.
The PTTEP HRA improving process via the application of HRES will be implemented in both domestic and international assets. The more user friendly software to support the process of HRA is being developed. Then the result of HRA and the feedback from HRA team will be collected for further study as continuous PTTEP HRA process improvement.