bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation Methods in the Diagnosis and Determination of Surgical Treatment Tactics for Primary Multiple Lung Carcinoid
Authors: Nudnov N. V. , Сhkhikvadze V. D. , Kontorovich D. S.
Published: September 2021

The early and complete diagnosis of lung carcinoid tumors is of great interest in clinical oncology, since this is the basis for the possibility of using options for organ-sparing surgical treatment. According to the 2015 WHO classification, carcinoids belong to the group of neuroendocrine tumors and are divided into two types: a typical carcinoid and an atypical one. Based on the data available in the literature, there are from 0.2 to 2 cases per 100,000 population. The paper considers the possibilities of radiation studies in the early diagnosis of this tumor, as well as those of determining the tactics, type, and scope of surgical treatment.
Comparsion of Liver and Spleen Elastometry Features
Authors: Morozov S. V. , Izranov V. А.
Published: September 2021

The review presents data on the comparison of the features of liver and spleen stiffness measurements and those on the impact of various conditions on the measurement results (the type of a sensor used, food intake, number of measurements, patient position, breathing phase, etc.). Literature has been sought in the PubMed and eLibrary databases. In particular, the liver and spleen stiffness values vary differently at the height of inspiration and expiration. This is due to organ engorgement with a change in intrathoracic and intraabdominal pressures, as well as to a reduction in splenic arterial flow during exhalation. The review gives published data on liver and spleen stiffness values in healthy volunteers. The spleen is a stiffer organ than the liver. The different liver and spleen stiffness is explained by the features of blood supply (the spleen receives the most blood supply from the intensive-flow artery; the liver does from the portal vein). The reasons for increasing the stiffness of these organs in both health and disease are described. Estimation of liver stiffness can be used to diagnose cirrhosis and portal hypertension. That of spleen stiffness can help in the diagnosis of portal hypertension and in the indirect diagnosis of the presence of esophageal varices and the nature of a splenic lesion.
MARTIN HEIDEGGER E O JOVEM LETÃO: OUTRA VEZ A QUESTÃO POLÍTICA
Authors: Martins Filho José Reinaldo F.
Published: September 2021

Neste breve relato biobibliográfico, gostaria de deixar registrada uma relação que, até muito recentemente, permanecia completamente ignorada por mim (e, imagino, também por muitos). De minha parte, sua explicitação levou a pensar como são compostos os nossos próprios itinerários, muitas vezes interrelacionados ao de identidades anônimas, mas cuja influência demonstra-se crucial para a consecução de determinados desfechos, de reviravoltas históricas, como alento ou consequência, mas sempre como amálgama de uma passagem.
Callus Induction from Root Fragments of Falcataria moluccana Plantlets
Authors: Putri Asri , Nurtjahjaningsih ILG , Prihatini Istiana , Nai'em Mohammad , Indrioko Sapto , Rahayu Sri
Published: September 2021

Callus induction of F. moluccana (sengon) was still an obstacle to indirect organogenesis regeneration. The purpose of the study was to determine the callus induction formation from root fragments of F. moluccana plantlets. Primary explants (fragments of roots) were cultivated on MS induction basal media and three concentration combination of PGRs (BAP and NAA): 0.5 ml/l BAP; 0,1 ml/l NAA (single PGR); and combination of 0.5 ml/l BAP + 0.1 ml/l NAA (double PGR). When roots were used as explants, high formation rates of callus (more than 70%) were obtained. Highest formation rates of callus were in NAA added at all clones (12 clones), then BAP added (7 clones) and BAP + NAA added (5 clones). The results indicated that BAP and NAA concentrations used in the media were influence the producing callus and affect the amount of callus produced from roots of sengon. The addition of NAA also gives higher callus proliferation results than the addition of BAP or the addition of a combination of the two hormones. The results indicated that BAP and NAA concentrations used in the media were influence the producing callus and affect the amount of callus produced from roots of sengon.
Faecal Microbial Transplantation in Critically Ill Patients – Structured Review and Perspectives
Authors: Cibulková Ivana , Řehořová Veronika , Hajer Jan , Duska Frantisek
Published: September 2021

The human gut microbiota consists of bacteria, archaea, fungi, and viruses. It is a dynamic ecosystem shaped by several factors, which play an essential role in both healthy and diseased states of humans. A disturbance of the gut microbiota, also termed “dysbiosis,” is associated with increased host susceptibility to a range of diseases. Because of splanchnic ischaemia, exposure to antibiotics, and/or underlying the disease critically ill patients loose 90% of the commensal organisms in their gut within hours after the insult. This is followed by a rapid overgrowth of potentially pathogenic and pro-inflammatory bacteria altering metabolic, immune, and even neurocognitive functions and turning the gut into the driver of systemic inflammation and multiorgan failure. Indeed, restoring healthy microbiota by means of faecal microbiota transplantation (FMT) in the critically ill is an attractive and plausible concept in intensive care. Yet, available data from controlled studies are limited to probiotics and FMT for severe C. difficile infection or severe inflammatory bowel disease. Case series and observational trials generate hypothesis that FMT might be feasible and safe in immunocompromised patients, refractory sepsis, or severe antibiotic-associated diarrhea in ICU. There is a burning need to test these hypotheses in randomized controlled trials powered for determination of patient-centered outcomes.
Twenty-five Years of Geomorphological Evolution in the Gokurakudani Gully (Unzen Volcano): Topography, Subsurface Geophysics and Sediment Analysis
Authors: Gomez Christopher , Shinohara Yoshinori , Tsunetaka Haruka , Hotta Norifumi , Bradak Balazs , Sakai Yuichi
Published: September 2021

In the aftermath of pyroclastic-flow –dominated eruptions, lahars are the main geomorphic agent, but at the decadal scale, different sets of processes take place in the volcanic sediment cascade. At Unzen Volcano, in the Gokurakudani Gully we investigated the geomorphologic evolution and how the topographic change and the sediment change over time is controlling this transition. For this purpose, a combination of LiDAR data, aerial photography and photogrammetry, Ground Penetrating Radar and sediment grain-size analysis was done. The results show chocking zones and zones of enlargement of the gully, partly controlled by pre-eruption topography, but also by the overlapping patterns of the pyroclastic flow deposits of 1990 – 1995. The Ground Penetrating Radar revealed that on top of the typical lahar structure at the bottom of the gully, side-wall collapses were trapping finer sandy sediments formed in relatively low-energy deposition environment. This shows that secondary processes are taking place in the sediment transport process, on top of lahar activity, but also that these temporary dams may be a source of sudden sediment and water release, leading to lahars. Finally, the sediments from the gully walls are being preferentially oozed out of the pyroclastic-flow deposit, meaning that over longer period of time, there may be a lack of fines, increasing permeability and reducing internal pore-pressure needed for lahar triggering. It also poses the important question of how much of a past-event one can understand from outcrops in coarse heterometric material, as the deposit structure can remain, even after loosing part of its fine material.
Content-based Spam Email Detection Using N-gram Machine Learning Approach
Authors: Hossain Syed Md. Minhaz , Sarker Iqbal H.
Published: September 2021

Recently, spam emails have become a significant problem with the expanding usage of the Internet. It is to some extend obvious to filter emails. A spam filter is a system that detects undesired and malicious emails and blocks them from getting into the users' inboxes. Spam filters check emails for something "suspicious" in terms of text, email address, header, attachments, and language. However, we have used different features such as word2vec, word n-grams, character n-grams, and a combination of variable length n-grams for comparative analysis in our proposed approach. Different machine learning models such as support vector machine (SVM), decision tree (DT), logistic regression (LR), and multinomial naïve bayes (MNB) are applied to train the extracted features. We use different evaluation metrics such as precision, recall, f1-score, and accuracy to evaluate the experimental results. Among them, SVM provides 97.6 \% of accuracy, 98.8\% of precision, and 94.9\% of f1-score using a combination of n-gram features.
Potential Targets for Evaluation of Sugarcane Yellow Leaf Virus Resistance in Sugarcane Cultivars: In silico Sugarcane miRNA and Target Network Prediction
Authors: Ashraf Muhammad Aleem , Feng Xiaoyan , Shen Linbo , Zhang Shuzhen
Published: September 2021

The Sugarcane yellow leaf virus (SCYLV) is associated with sugarcane yellow leaf disease (SCYLD) and is considered to be the most economically deleterious emerging pathogen that represents a potential threat and danger to sugarcane cultivation in China. Over the last two decades, high genetic diversity in the SCYLV genotypes was observed worldwide, with a greater chance of YLD incidence for sugarcane injury. SCYLV infection has significantly damaged its economic traits and is responsible for substantial losses in biomass production in sugarcane cultivars. This study aims to identify and comprehensively analyze sugarcane microRNAs (miRNAs) as therapeutic targets against SCYLV using plant miRNA prediction tools. Mature sugarcane miRNAs are retrieved and are used for hybridization of the SCYLV. A total of seven common sugarcane miRNAs were selected based on consensus genomic positions. The biologically significant, top ranked ssp-miR528 was consensually predicted to have a potentially unique hybridization site at nucleotide position 4162 for targeting the ORF5 of the SCYLV genome; this was predicted by all the algorithms used in this study. Then, the miRNA–mRNA regulatory network was generated using the Circos algorithm, which was used to predict novel targets. There are no acceptable commercial SCYLV-resistant sugarcane varieties available at present. Therefore, the predicted biological data offer valuable evidence for the generation of SCYLV-resistant sugarcane plants.
Bioemulsifier-Producing Bacillus subtilis from Railway Soil
Authors: Benoit Thomas
Published: September 2021

A novel enrichment combined with a rapid screening method was employed to isolate bioemulsifying strains of Bacillus subtilis. Among a total of twenty isolates from railway soil at six geographically distant sites, ten produced bioemulsifiers for soybean oil and crude oil. Qualitative drop-collapse assays indicated the bioemulsifiers were surfactants.
The landscape of PDK1 in Breast Cancer
Authors: Wang Na , Fu Jianjiang , Li Zhihua , Jiang Ningni , Chen Yanhong , Peng Juan
Published: September 2021

Given that 3-Phosphoinositide-dependent kinase 1 (PDK1) plays a crucial role in malignant biological behaviors of a wide-range of cancers, we further review the influence of PDK1 in breast cancer (BC). First, we describe the power of PDK1 in cellular behaviors and extensively demonstrate the interacting networks of PDK1 via PI3K-dependent/ PI3K-independent pathway. Then we enlighten the roles of PDK1 in carcinogenesis, growth and survival, metastasis, and chemoresistance in BC cells. More important, we sort the current preclinical or clinical trials of PDK1 targeted therapy in BC and find that even though at present no selective PDK1 inhibitor is available for BC therapy, but the combination trials of PDK1 targeted therapy and other agents have demonstrated some benefit. Thus, there is increasing anticipations that PDK1 targeted therapy will have its space in future therapeutic concepts of BC, and we hope to feature PDK1 in BC to the clinic and bring the new promising to patients for targeted therapies.
Peraturan Hukum Adat Baduy dan Hierarki Menurut Undang Undang yang Berlaku
Authors: Maghfiroh Putri Azzahra
Published: September 2021

The Baduy tribe is located closest to the capital city of the country. This is special to describe, how Baduy maintains its customs and customary laws in the midst of the influence of technological advances and the development of positive Indonesian law which is especially due to its geographical location not far from the metropolitan city, namely Jakarta and its surroundings. Then the purpose of this study also wants to reveal how Baduy customary law regulations and hierarchy according to applicable laws. Baduy is an ethnic indigenous people who still live in Indonesia. The hierarchy or order of laws and regulations in Indonesia refers to the recognition and respect given by the state in Article 18B paragraph (2) of the 1945 Constitution of the Republic of Indonesia, which is not sufficient to protect the rights of the Baduy customary law community plus the weakness of Perda No.32 of 2001 which discuss the customary rights of the Baduy customary community only. The clash of Baduy traditional interests with the government system has made Baduy weaker in terms of representation. The government must immediately draft a law related to the protection of Baduy customary rights and or create a representation mechanism for indigenous peoples.
Perlindungan Hukum bagi Isteri yang Ditelantarkan oleh Suami Ditinjau dari Perspektif Hukum Perdata
Authors: Rohman Roni Saepul , Taun Taun
Published: September 2021

Husbands have absolute rights and obligations in building a household. Vice versa, a wife has the same absolute rights and obligations in managing the household. There are still husbands or wifes who are negligent in carrying out their obligations and even do not carry them out. The Method used in this research is the normative legal research method,which is a study that examines a document, namely various secondary data such as statutory regulations, legal theory, court decisions and legal scholar opinions. The case that often occurs is neglect by husbands against theirs own wifes. There are many factors that cause a husband to abandon his wife and even his own family. However, a wife has the right to sue the husband in court by filing a claim for livelihood, which is a legal remedy that the wife can take to get justice.
Implementasi Pelaksanaan Eksekusi Jaminan Fidusia Berdasarkan Putusan Mahkamah Konstitusi Nomor 18/Puu-Xvii/2019 Tentang Jaminan Fidusia (Studi Pada Koperasi Wahidiyah Ta’Awun Kepanjen Malang)
Authors: Amilatul Siti Nur , Suciati Suciati , Ambarsari Ririen Indria Dian
Published: September 2021

This study want to identify and analyze directly the implementation of the Constitutional Court Decision Number 18 / PUU-XVII / 2019 regarding the Fiduciary Guarantee Execution and to find out how the default settlement procedure in credit agreements in cooperatives with Fiduciary Guarantee and the obstacles faced in the process of executing fiduciary guarantees. This research is the result of field research field research, the formulation of the problem examined is how the fiduciary guarantee execution mechanism in the Constitutional Court decision No.18 / PUU-XVII / 2019 and how the implementation of fiduciary guarantee execution after the MK decision No.18 / PUU-XVII / 2019 at the Wahidiyah Ta'awun Union Kepanjen. Before the issuance of the Decision of the Constitutional Court Number 18 / PUU-XVII / 2019, the execution of guarantees for debtors who have defaulted is regulated under Articles 29 to Article 34 of Law Number 42 of 1999 concerning the Execution of Fiduciary Collateral. After the Constitutional Court Decision, the execution of fiduciary guarantees is carried out by negotiation and mutual agreement of the default, if there is no agreement between the Debtor and the Cooperative Management, then the applicable legal procedure must be carried out, namely a civil lawsuit in court.
Effect of Board Size and Duality on Corporate Social Responsibility: What has Improved in Corporate Governance in Asia?
Authors: Alabdullah Tariq Tawfeeq Yousif , Ahmed Essia Ries , Muneerali Mohammed
Published: September 2021

The aim of this study is to examine the relationship between board size and CEO duality, and corporate social responsibility (CSR). A total of 91 public listed companies from Bursa Malaysia representing the sample of the current study were selected. Secondary data were used and sourced from annual report on the companies. Using descriptive statistics, the existence and the extent of CSR disclosure on Malaysian companies were ascertained. An analysis of the quantitative data was then made using the Partial Least Squares (PLS). The findings from this research show that the role of board size suggest a significant and positive relationship with CSR disclosure. On the other hand, CEO duality on CSR disclosure indicates a negative relationship. This research contributes to the existing literature in terms of the roles of board Size and CEO duality on CSR initiatives. Furthermore, It highlights the necessity of following the new trends in corporate governance field by investigating its mechanisms with the new trendsin financial Industry from Islamic perspective as this might be positively added to the field of corporate governance due to the high significant role for these two fields.
Continuum-Scale Gas Transport Modeling in Organic Nanoporous Media Based on Pore-Scale Density Distributions
Authors: Liu Zizhong , Emami-Meybodi Hamid
Published: September 2021

We present a continuum-scale diffusion-based model informed by pore-scale data for gas transport in organic nanoporous media. A mass transfer and an adsorption model are developed by considering multiple transport and storage mechanisms, including bulk diffusion and Knudsen diffusion for free phase, surface diffusion and multilayer adsorption for sorbed phase. A diffusion-based governing equation is derived based on free phase concentration for the overall mass conservation of free and sorbed phases, carrying a newly-defined effective diffusion coefficient and a capacity factor to account for multilayer adsorption. Diffusion of free and sorbed phases is coupled through a pore-scale simplified local density method based on the modified Peng-Robinson equation of state for confinement effect. The model is first utilized to analyze pore-scale adsorption data from a krypton (Kr) gas adsorption experiment on graphite. Then we implement the model to conduct sensitivity analysis of the effects of pore size on gas transport for Kr-graphite and methane-coal systems. The model is finally used to study Kr diffusion profiles through a coal matrix obtained through X-ray micro-CT imaging. The results show that the sorbed phase occupies most of the pore space in organic nanopores with less than 10 nm due to multilayer adsorption, and surface diffusion contributes significantly to the total mass flux. Therefore, neglecting the volume of sorbed phase and surface diffusion in organic nanoporous rocks may result in considerable errors in the prediction of hydrocarbon production. The comparison between BET-based and Langmuir-based models shows that Langmuir-based models can only match the adsorption isotherm at low pressure and yield lower effective surface diffusion coefficients. Therefore, implementing a Langmuir-based model may be erroneous for an organic-rich reservoir with strong adsorption capacity during the early depletion period when the reservoir pressure is high.
Novel Simulator for Design and Analysis of Matrix Acidizing Jobs with Fluoroboric Acid in Sandstone Reservoirs
Authors: Qamruzzaman Mohammed , Khan Mandeep , Roy Dhirendra Chandra , Raman Ravi
Published: September 2021

Matrix acidizing with fluoroboric acid (HBF4) has gained special attention as not only it provides deeper penetration of in – situ generated hydrofluoric acid, but also stabilizes formation fines by binding them to the pore surface. While numerous mathematical models exist in literature for design and evaluation of conventional mud acid treatments, fewer attempts have been made in developing a lab validated model that can do so for fluoroboric acid treatments.

This paper presents a novel mathematical model that has been developed taking into account the chemical kinetics and equilibrium aspects of important reactions and fluid flow inside the reservoir rock. The solution to the governing equations has been obtained through tools of computational fluid dynamics (CFD). The model has been validated rigorously through use of state-of-the-art core flooding and ion chromatography setups. The resulting simulator can be used to design an optimum fluoroboric acid treatment by analysing the effects of all the important factors including reservoir temperature, formation mineralogy and job execution details like initial acid concentration, pumping rate, job volume and shut-in time post treatment.

Simulation results with the developed model indicate that although penetration of fluoroboric acid is much larger compared to mud acid, its overall effect on skin factor is inferior for temperatures less than 90 °C. Stimulation in such wells should be preferred with mud acid which can be followed by fluoroboric acid for fines stabilization. For temperatures more than 120 °C, stimulation effects of fluoroboric acid become comparable to that of mud acid. Under these conditions, it can be used as an alternate fluid to mud acid to prevent issues of secondary and tertiary precipitation. It is found that major stimulation benefits with fluoroboric acid are realized during pumping and subsequent shutting of well, which is a common practice with fluoroboric acid, has relatively smaller effect on skin factor. Apart from design and evaluation of fluoroboric acid treatments, the simulator can also be used for analyzing mud acid and mud acid followed by fluoroboric acid treatments thus enabling the user to select and design the best suited treatment for a given well.
Mechanisms and Mitigation of 3D Coupled Vibrations in Drilling with PDC Bits
Authors: Chen Shilin , Propes Chris , Lanning Curtis , Dunbar Brad
Published: September 2021

In this paper we present a new type of vibration related to PDC bits in drilling and its mitigation: a vibration coupled in axial, lateral and torsional directions at a high common frequency (3D coupled vibration). The coupled frequency is as high as 400Hz. 3D coupled vibration is a new dysfunction in drilling operation. This type of vibration occurred more often than stick-slip vibration. Evidences reveal that the coupled frequency is an excitation frequency coming from the bottom hole pattern formed in bit/rock interaction. This excitation frequency and its higher order harmonics may excite axial resonance and/or torsional resonance of a BHA. The nature of 3D coupled vibration is more harmful than low frequency stick-slip vibration and high frequency torsional oscillation (HFTO). The correlation between the occurrence of 3D coupled vibration and bit design characteristics is studied. Being different from prior publications, we found the excitation frequency is dependent on bit design and the occurrence of 3D coupled vibration is correlated with bit design characteristics. New design guidlines have been proposed to reduce or to mitigate 3D coupled vibration.
An Innovative Low Cost Well Monitoring Solution: W.A.N.D
Authors: Boero Rollo Jean Grégoire , Ordonez Varela John Richard , Ben Ghzaiel Tayssir , Mouanga Cedric , Luxey Arnaud , Risler Frederic
Published: September 2021

Wireless Autonomous Nano-sensor Device (WAND) system is a disruptive cost-effective micro-system for well monitoring. It allows to realize pressure, temperature, inertial, and magnetic field measurements in harsh conditions; it also offers Bluetooth low-power communication and Wireless charging capabilities.

Analysis’ results of an industrial offshore pilot realized in Congo (a world first in O&G industry in such complex environment), and major improvements implemented after this pilot are reported in this paper. Accomplished advancements comprise hardware and software developments extending operation lifetime, and simplifying on-site utilization.

To date, there is not a commercial solution of this type in the market, the realization of this project is a real innovation allowing practical and low-cost monitoring during well intervention while minimizing the risks associated with standard Rigless intervention. Other applications regarding dry-tree wells on tension-leg platforms (TLP), drilling and completion operations, and pipeline monitoring are being investigated, too.
The Same Drift Monodiameter Completion System in Solving Drilling and Well Infrastructure Challenges
Authors: Godfrey Matthew , Baker Roy
Published: September 2021

The public domain contains many work efforts that document the advantages of expandable drilling and completions systems within the industry (Filippov 1999, Lohoefer 2000). The ability to place a solid steel liner or patch into a well and transform it by cold working to a larger diameter provides an opportunity to drill deeper while maintaining sufficient wellbore diameter. The use of expandable technology has led to the development of a formable and retractable-segmented cone. The cone supports an expandable system capable of passing through the drift of a base casing that can then result in an expansion providing the equivalent drift diameter. The technology allows the placement of additional liner points in a well that can extend liner lengths as well as isolate sections of open hole that were previously impossible to isolate due to wellbore geometry restriction. There are no limitations on the number of open hole patches installed in a given well which are helpful when wells experience multiple drilling hazards. Each patch can pass through a previously installed patch.

The idea of monodiameter expandable liners began in the early 2000s (Dupal 2002, Dean 2003). This paper presents the technical challenges, solutions, and testing of a novel monodiameter system that expands 11-3/4 in. 47 lb/ft pipe which can result in a post-expansion drift diameter of 12-1/4 in. Finite element analysis helped transform the concept from the theoretical system to field execution. The work efforts show the successful testing of the monobore system at surface, and the resulting field trials demonstrate the ability of the technology to fulfil the installation objectives. In addition, the success of the methodology has led to the development of additional monobore system sizes.
Gas Migration in Wellbores During Pressurized Mud Cap Drilling PMCD
Authors: Samdani Ganesh Arunkumar , Rao Sai Sashankh , Gupta Vishwas Paul
Published: September 2021

In PMCD operations, reservoir gas is expected to migrate uphole, and the uncertainty in gas migration rates under downhole conditions leads to challenges in planning logistics and fluid requirements. Estimates of migration velocities based on current methods (e.g. Taylor-bubble correlation) are highly conservative and involves simplifying assumptions. This paper presents a systematic approach to understanding the fundamentals of gas migration in wellbores, relates it to field data, and provides recommendations to improve PMCD design and planning. Our approach includes analysis of PMCD field data, multiphase flow literature and computational flow simulations. The field data on gas migration is used to establish the field-scale parametric effects and observed trends. Multiphase flow literature is used to qualitatively understand some of these parametric effects at downhole conditions. A comparison between multiphase flow literature and field data overwhelmingly demonstrates the gaps in understanding of underlying physics. 3-dimensional multiphase CFD simulations for a representative well geometry and downhole conditions are used to understand gas migration physics at downhole conditions and the reasons for its sensitivity to different conditions.

CFD simulations showed a strong impact of pressure on bubble breakup. As a result, the gas migrates as a slow-moving swarm of smaller bubbles. The formation of smaller bubbles from a given gas volume is a rate dependent process and requires a finite time to reach to an equilibrium/steady-state. The field conditions provide both high downhole pressure and sufficient length-scale for formation of smaller slow-moving bubbles. For the same reason, small scale-experiments are limited in their application for field-scale designs due to use of low pressure and/or insufficient length-scales. The CFD results also compare well with field data in showing ~30% holdup of migrating gas at low migration rates and negligible effect of rotation and wellbore geometry i.e. annulus vs openhole. The extent and rate of disintegration of gas volume (bubble) has a negative correlation with well inclination, liquid viscosity, and surface tension. The rheology and liquid viscosity also affect the ability of liquid to sweep the gas back into the reservoir and therefore it is expected to have an optimum range for a given PMCD application. Use of high viscosity fluids for typical downhole well conditions is counterproductive and results in higher gas migration rates and therefore not recommended. The understanding of downhole physics is expected to improve logistics/storage/ planning/fluid choice and lead to lower gas migration rates and reliable operation. The same approach can be applied to other operations and scenarios where gas migration velocities are a key design factor.
Pressure Interpretations in Acid Fracturing Treatments
Authors: Pandey Vibhas J.
Published: September 2021

Acid fracturing is a preferred method of stimulating low permeability limestone formations throughout the world. The treatment consists of pumping alternating cycles of viscous pad and acid to promote differential etching, thereby creating a conductive acid-etched fracture.

Acid-type, pad and acid volumes, and the injection rates in the designed pump schedule are based on treatment objectives, rock-types and in-situ conditions such as temperatures, in-situ stress, proximity to water-bearing layers, and others. During the acid fracturing treatment, the acid-rock interaction is often marked by signature pressure responses, that are a combined outcome of acid reaction kinetics, responses to changes in fluid viscosity and densities, fluid-frictional drop in narrow hydraulic fractures, and other such parameters. This paper focuses on interpretation of bottomhole pressures during acid fracturing treatment to separate these individual effects and determine the effectiveness of the treatment.

Unlike propped fracturing treatments where most fracturing treatments result in net pressure gain, acid fracturing treatments seldom result in net pressure increase at the end of the treatment because the in-situ stresses are generally relieved during the rock-dissolution and fracture width creation process that results from acid-mineral reactions. Not only is the extent of stress relief evident from the difference in the start and the end of the treatment instantaneous shut-in pressures, the loss of stresses is also apparent during the treatment itself, especially in jobs where the treatment data is constantly monitored and evaluated in real-time. The study reveals that the changes in pressure responses with the onset of acid in the formation can be successfully used to determine the effectiveness of treatment design and can aid in carrying out informed changes during the treatment. Better understanding of these responses can also lead to more effective treatment designs for future jobs.

The interpretation developed in the study can be applied to most of the acid fracturing treatments that are pumped worldwide.
Closing the Gap in Characterizing the Parent Child Effect for Unconventional Reservoirs - A Case of Study in Vaca Muerta Shale Formation
Authors: Lerza Alejandro , Cuervo Sergio , Malhotra Sahil
Published: September 2021

In Shale and Tight, the term "Parent-Child effect" refers to the impact the depleted area and corresponding stress changes originated by the production of a previously drilled well, the "parent", has over the generated hydraulic fracture geometry, conforming initial drainage area and consequent production performance of a new neighbor well, called "child". Such effect might be considered analogous to the no flow boundary created when the drainage areas of two wells meet at a certain distance from them in conventional reservoirs; but, unconventional developments exhibit higher exposure to a more impactful version of this phenomena, given their characteristic tighter well spacing and the effect pressure depletion of the nearby area by the neighbor well has over the child well's hydraulic fracture development.

Due to the importance the Parent-Child effect has for unconventional developments, this study aims first to generally characterize this effect and then quantify its expected specific project impact based on real field data from the Vaca Muerta formation.

To do so, we developed a methodology where fracture and reservoir simulation were applied for calibrating a base model using field observed data such as microseismic, tracers, daily production data and well head pressure measurements. The calibrated model was then coupled with a geomechanical reservoir simulator and used to predict pressure and stress tensor profiles across different depletion times. On these different resulting scenarios, child wells were hydraulically fractured with varying well spacing and completion designs. Finally, the Expected Ultimate Recovery (EUR) impact versus well spacing and the parent´s production time were built for different child´s completion design alternatives, analyzed and contrasted against previously field observed data.

Results obtained from the characterization work suggests the parent child effect is generated by a combination of initial drainage area changes and stress magnitude and direction changes, which are both dependent of the pressure depletion from the parent well. Furthermore, the results show how the well spacing and parent's production timing, as well as parent's and child's completion design, significantly affect the magnitude of the expected parent child effect impact over the child's EUR.
Condensate Recovery from Tight Gas-Condensate Reservoirs using a new Method Based on a Gas-Based Chemical
Authors: Nasieef Abdulelah , Jamiolahmady Mahmoud , Doryanidaryuni Hosein , Restrepo Alejandro , Ocampo Alonso , Chakrabarty Toushar , Seteyeobot Ifeanyi
Published: September 2021

Recovery from gas condensate reservoirs, when the pressure is below dew point pressure (Pdew), is adversely affected by the accumulation of condensate in the near wellbore region. The mitigation of the near-well bore condensate banking is the main purpose of any enhanced recovery method implemented in gas condensate reservoirs.

In this work, a new method was tested to improve condensate recovery by using a chemical that was delivered using hydrocarbon gas as a carrier into a very low permeability and very low porosity reservoir rock. Chemicals are typically injected using liquid carrier solvents. The use of hydrocarbon gas as the carrier provides a remedy to mitigate condensate banking in very low permeability cores by minimizing complications associated with low injectivity and back flow clean-up process requirements of an injected liquid.

The chemical potential was evaluated by recording production data from unsteady-state coreflood experiments. The injection of the chemical with equilibrated gas resulted in condensate saturation to decrease from 19.6% to 6.5%. This decrease was not instantaneous and took some time to occur indicating that the chemical needs time to interact with the resident fluid and rock. The benefit of the method, at the field scale, was also estimated by performing single-well numerical simulations that use relative permeability (kr) data which history matched the measured coreflood production data. The results of these preliminary simulations also showed improved recovery of gas and condensate compared to pure depletion, without chemical, by around 40% for the cases considered.
A Cost-Effective Stimulation Workflow Unlocks New Perspectives for Matrix Acidizing in Openhole Horizontal Tight Carbonate – A Case Study from West Kuwait
Authors: Al-Sabea Salem , Patra Milan , Abu-Eida Abdullah , Al-Azmi Nasser , AlEidi Mohammad , Al-Dousari Mohamad , Al-Qattan Hasan , Salem Abrar , Badrawy Kareem , Peiwu Liu , Enkababian Philippe , Molero Nestor , Pochetnyy Valentin , Baidas Abdullah
Published: September 2021

The Mishrif formation in west Kuwait is a tight carbonate reservoir having low oil mobility. It is fractured and heterogeneous with wide variation in porosity ranging from 10 to 25%, matrix permeability of about 0.1 to 10 md, and 20°API oil. Production tests and geomechanical study results have revealed that productivity is mostly from the high-permeability matrix and critically stressed fracture networks.

Recently, the Mishrif development has been dominated by horizontal wells to maximize reservoir contact and enhance productivity. However, a challenge in such openhole completion is the stimulation strategy requiring effective diversion technology due to the uneven acid distribution along the lateral section. To address those challenges, a novel engineered workflow has been implemented relying on distributed temperature sensing (DTS) to assess the fluid coverage across the openhole section. Results enable identifying high- and low-intake zones, segmenting the uncased section into intervals requiring different levels of stimulation, and making informed decisions regarding diversion requirements.

The intervention was conducted in two stages. Coiled tubing (CT) was the selected fluid conveyance method on the first stage given its capacity for more controlled fluid placement, and high-rate bullheading stimulation was selected for the second stage. During the treatment, multiple challenges were faced, mainly driven by a high-permeability streak identified by the DTS near the heel of the lateral. The CT stimulation procedures were modified on the spot, and measures were taken to minimize the impact on the thief zone, which included a combination of diversion techniques, such as high-pressure jetting, dual injection, and pumping of a near-wellbore nonreactive diverter, which is composed of a customized blend of multimodal particles and degradable fibers to minimize fluid leakoff into the high-intake zone. Likewise, real-time downhole telemetry was crucial throughout the CT stimulation because it allowed the highest injection rate possible below the preset pressure limits, continuous monitoring of downhole dynamics along the intervention, and optimal actuation of the high-pressure jetting tool. Upon completion of the CT stimulation, a second DTS log was carried out to evaluate the fluid coverage and effectiveness of the diversion strategy, enabling further adjustment of the bullhead stimulation program.

This stimulation workflow implemented in west Kuwait represents a cost-effective alternative to stimulate openhole tight carbonates. This study brings new perspectives for treating complex reservoirs in the region, and shares lessons learned for future interventions.
Post Frac Cleanout and Plug Milling Optimization Strategy. Successful Implementation in Extremely Depleted Wells in the Sultanate of Oman
Authors: Nunez Alvaro Javier , Sayapov Ernest , Benchekor Ahmed , Al Husaini Nasser Khalfan , Al Kendi Al Muntaser , Khalil Mohamed Amin , Al Awaisi Asma Ali Salim , Al Kharusi Sharifa Saif
Published: September 2021

Post frac cleanout and milling operations are considered some of the most critical activities that leverage on the operational benefits of coiled tubing. Therefore, they deserve the highest focus on continuous improvement and planning since the associated efficiency gains are often immediately quantifiable. This paper will focus on the improvement and optimization of post frac cleanout and milling strategies in extremely depleted wells in the Sultanate Of Oman. The gains from such optimization helped improve wells delivery and overall performances.

Plug and perf methodology is still the preferred placement method of hydraulic fractures. One of the main challenges in depleted wells is the need for cleanout and plug milling after each stage to avoid risk of CT becoming stuck either differentially due to depletion or mechanically with plug cuttings in case circulation is lost. For years the frac and mill concept was adopted to complete those wells, resulting in frequent delays to frac operations and huge cost impact to the overall project. An efficiency improvement plan was agreed upon to address this particular challenge. A step-by-step strategy improvement plan was developed via in-depth analysis of frac initiation and reservoir characteristics in order to combine together multiple stages of post-frac cleanout and milling activities. This was done through unique software simulations and fluid selection criteria to achieve the lowest possible bottom hole pressure to minimize the losses in addition to the highest possible lifting velocity and best carrying medium conditions. Moreover, the utilization of engineered fluid solutions with foaming agent and foam generator have demonstrated significant added value through enhancement of carrying fluid properties while achieving the lowest possible settling velocity, which in turn lead to the highest possible velocity factor.

After completing the agreed optimization plan, a post frac cleanout with 6-plug milling was performed in a single combined stage instead of multiple individual stages. This improvement reduced the overall frac operation for 6 stages from nearly 30-35 days to 19-20 days. Understanding the field and reservoir pressures in addition to fluid selection for both post frac cleanout and milling operation is crucial to successful implementation of this methodology. This achievement was delivered through a collaboration between many different business units from design to execution and it will help Petroleum Development Oman PDO on the future planning of hydraulic fracturing activity. The completion of the entire wells (well delivery) was achieved in a significantly shorter period of time compared to previous wells; this is reflected on actual cost reduction of more than 20% of total cost/AFE.
Well Cutting Without Explosives with Multiple Cuts on a Single Run
Authors: Ghannam Hanan , Mourani Houssam , Schwanitz Brian Joseph
Published: September 2021

Pipe cutting operations are often a critical part of stuck pipe situations, well interventions and plug and abandon operations which all need to remove cut sections of pipe from the well. Unlike traditional ‘blade’ style e-line cutters, which can jam under pipe compression or explosive pipe cutters, which need to dress-over the jagged cut by the rig, a new electric line mechanical cutter's unique design enables performance even if the pipe is under compression, in tension or is neutral. It can also perform multiple cuts in the same run, while creating a clean and machined cut with tool-entry friendly shape.

This paper will describe the technology of the new generation cutter, present two case histories; one of multiple cuts of stuck drill pipe, per each run in hole, from Germany and one of a critical tubing cut from a subsea well in Nigeria, using electric wireline and tractor conveyed services for many tasks traditionally performed with coiled tubing in highly deviated wells. These "light vs heavy" solutions can often be done off-line from the rig.
Stranger Things 2: Unconventional Deployment Method of High Performance Lightweight Cement Enables Success in Complex Wells
Authors: Shine Joe , Qasmi Urooj , Gbemiga Ilesanmi
Published: September 2021

There are advantages to using high performance lightweight cement when encountering low bottomhole pressures. The most notable are maintaining wellbore stability during cement placement and the isolation of potential flow zones to achieve the wellbore construction objectives. Several complex wells sought these advantages for similar situations. A review of the deployment process for using high performance lightweight cement conventionally, including the quality assurance measures, initially deemed it as not a viable option. As the complex wells needed a technical solution, an unconventional deployment method for high performance lightweight cement enabled its use while simplifying and improving quality assurance; allowing achievement of the isolation requirements.
Manuscript Title: Mechanical and Microstructural Studies of Volcanic Ash Beds in Unconventional Reservoirs
Authors: Acosta Juan C , Curtis Mark E , Sondergeld Carl H , Rai Chandra S
Published: September 2021

Volcanic ash beds are thin layers commonly observed in the Eagle Ford, Niobrara and, Vaca Muerta formations. Because of their differences in composition, sedimentary structures, and diagenetic alteration, they exhibit a significant contrast in mechanical properties with respect to surrounding formation layers. This can impact hydraulic fracturing, affecting fracture propagation and fracture geometry. Quantifying the mechanical properties of ash beds becomes significant; however, it is a challenge with traditional testing methods. Common logging fails to identify the ash beds, and core plug testing is not possible because of their friability.

In this study, nanoindentation was used to measure the mechanical properties (Young's modulus, creep, and anisotropy) in Eagle Ford ash beds, and to determine the contrast with the formation matrix properties. Two separate ash beds of high clay and plagioclase composition were epoxied in an aluminum tray and left for 48 hours curing time. Horizontal and vertical samples of ash beds were acquired and mounted on a metal stub, followed by polishing and broad beam ion milling. Adjacent samples were also prepared for high-resolution Scanning Electron Microscope (SEM) microstructural analysis.

The Young's modulus in ash beds ranged from 12 to 24 GPa, with the horizontal direction Young's modulus being slightly greater than that of the vertical samples. The Young's modulus contrast with adjacent layers was calculated to be 1:2 with clay-rich zones and 1:4 with calcite rich zones. The creep deformation rate was three times higher for ash beds compared to other zones. Using Backus averaging, it was determined that the presence of ash beds can increase the anisotropy in the formation by 15-25%. SEM results showed a variation in microstructure between the ash beds with evidence of diagenetic conversion of rhyolitic material into clays. Key differences between the two ash beds were due to the presence of plagioclase and the occurrence of porosity within kaolinite. Overall porosity varied between the two ash beds and adjacent carbonate layers showing a significant increase in porosity.

Understanding the moduli contrast between adjacent layers can improve the hydraulic fracturing design when ash beds are encountered. In addition, the presence of these beds can lead to proppant embedment and loss in fracture connectivity. These results can be used for improving geomechanical models.