bluuebunny/crossref_metadata_2025_split huggingface dataset:
Horizontal Matrix Injector Stimulation in Unconsolidated Sand
Authors: Ekebafe Abraham O. , Tobechukwu Ezeokafor , Skaioye Ololade T. , Raymond Lawani 
Published: July 2019

Abstract
The AX field is located in Deepwater Offshore Nigeria and has been in production for ca.12 years through FPSO with a waterflood scheme providing pressure maintenance and sweep for the reservoirs. Over the years, AX field has moved from the use of deviated frac-pack injectors to horizontal SAS injectors due to significant declining injectivity observed with the deviated injectors.
The switch to horizontal injectors was premised on various studies proposing that horizontal water injectors in deep water are expected to have longer well life due to the larger flow area and ability to inject at lower flow velocities (matrix condition) compared to vertical water injectors. The benefits of going horizontal is further enhanced by keeping the well in Matrix mode for as long as possible before switching into frac mode. However, damage is inevitable afterwards, even for relatively clean injection water. This may be primarily due to various factors, one of which is fines influx into the well during abrupt shut-ins/trips from the FPSO.
AX field started operating horizontal injectors since 2011. On the average, most horiziontal injectors in AX field begin to experience injectvty decline about 1 – 2 yrs after start of injection as was the case with AX9 injector.
AX9 is a horizontal injector providing support to 2 producers in the field. Over the past four years injection had declined from 40 kbwpd to 21 kbwpd at 395 barg IBHP with II of 20 bpd/psi. This drop in the injectivity index led to a production curtailment of ca. 5 kbopd from the supported producers.
From a cross learning opportunity, it was identified that there is higher possibility of success (POS) with stimulating horizontal water injectors while still in matrix mode. Leveraging on this knowledge we decided to attempt stimulating the AX9 well for better performance.
Stimulation was carried out successfully under matrix condition using a deepwater rig in May 2018. Post stimulation, well was ramped up to 43 kbpwd at 330 barg IBHP. Increase of ca. 15 kbwpd with a corresponding 21% drop in BHP. Initial performance shows a four-fold improvement in injectivity index; current injectivity index is 80 – 100 bpd/psi.
The success of the AX9 stimulation has validated early stimulation of injectors while still in matrix mode rather than later when the well would have switched to frac mode. Additionally, the acid recipe has opened opportunities to mitigating injectivity decline in deepwater water injectors.
Macroeconomic, Sectoral and Distributional Impact of Gas Monetization Policy in Nigeria: A CGE Application
Authors: Agiaye Emmanuel 
Published: July 2019

Abstract
The Nigerian gas market experienced growth in recent years due to the gas development policies of the government such as the Nigerian gas master plan. Nevertheless, the gas supply and utilization per capita has barely changed while policy objectives are largely unfulfilled. A new national gas policy 2017 recognized a full-blown energy crises in Nigeria in spite of its abundant gas resources. It thereby aims to increase gas utilization with more contribution to GDP, grow key sectors of the economy and reduce gas flaring to 2 percent. A policy of the magnitude of gas monetization policy a posteriori would have significant positive or negative impacts on macroeconomic, sectoral and distributional indicators. Is gas monetization policy good for all all? Employing the comparative static CGE model, this study carries out evaluation of increased gas supply on the Nigeria economy from 80 percent flare gas reduction and 30 percent reduction in direct tax rate on production. Results show that increased gas supply from flareout have positive influences on economic growth but slowed down with application of production tax incentives. The GDP, real investments, government revenues and sectors experienced growths except agriculture and transport sectors. The drop in average consumer prices encouraged household consumption as well as increased welfare. The study established causal relationship between increased gas utilization and economic growth. Efforts in driving the gas flaredown of monetization policy should be facilitated. The government shall exercise caution to ensure protection of the economy to guarantee proportionate health of the sectors that were negatively impacted such as agriculture and transport.
Successful Application of Capacitance Resistance Modeling to Understand Reservoir Dynamics in Brown Field Waterflood – A Niger Delta Swamp Field Case Study
Authors: Nwogu Ikemefula Cyril , Ayo Asaolu , Asemota Osamuedemen , Ajibade Ozzy 
Published: July 2019

Abstract
Capacitance Resistance Model (CRM) is an analytical tool for estimating reservoir properties and connectivity between producer-injector pairs in an established waterflooded oil reservoir system. The analysis incorporates historical production data, injection rates and available bottom hole pressures. In Swamp Field B (Niger Delta Nigeria), there were concerns of connectivity between producer and injector pairs in the K2 reservoir. CRM analysis was applied to resolve the uncertainty in producer-injector connectivity and provide better understanding of the reservoir flow dynamics.
Understanding the connectivity between existing injectors and producers, to ensure adequate water injection distribution for reservoir voidage balance and pressure maintenance necessitated a geologic and engineering review of existing data.
The results of the study revealed strong inter-well connectivity between active producers and two idle injectors in the reservoir for the period analyzed, corroborating a revised geologic interpretation of the reservoir. The idle injectors were previously left shut-in due to a geologic interpretation of the presence of shale impacting connectivity and performance.
Upon implementing recommendations from the study, an immediate pressure and production response was observed within three months of restoring the two idle injectors. The reactivation of the idle injectors also resulted in $20 MM savings by averting further work on a proposed new water injector.
This paper discusses the application of CRM in understanding producer-injector connectivity and emphasizes the use of digital analytic tools to better understand waterflood performance and address challenges with balancing voidage and maintaining reservoir pressure. It demonstrates the value of CRM technique in brown fields and the multidisciplinary approach adopted. Further application of similar techniques in other waterflood reservoirs within Chevron Nigeria is currently ongoing.
Successful Coiled Tubing Catenary Cement Packer and SAS Installation in a Horizontal Well for Developing Bypassed Reserves: Offshore Niger Delta
Authors: Songa Yannick N. , Ude Henry , Uzodinma Chioma , Enyioko Chigoziem , Ighavini Emmanuel , Haruna Onuh , Ndukauba Godian 
Published: July 2019

Abstract
Rigless coiled tubing (CT) operations with CT operated from a floating anchored vessel are deployed for well intervention operations where crane limitations and deck loading constraint present multiple challenges for accessing the marginal/bypassed pay in offshore locations. This operation involves operating the CT unit with the reel located on the floating vessel and the injector head positioned on the offshore platform. The CT catenary design was successfully deployed for developing behind casing reserves through efficient zonal isolation, cement packer installation, perforations, and sand control.
This paper presents the use of 1.75-in. CT on a 125K unit catenary system in a highly deviated horizontal well (&gt;85°) to develop the shallower reservoir. The well is located on a platform with insufficient deck space and load bearing capacity to accommodate the intervention spread. The through-tubing CT operations involve installation of mechanical isolation plugs, cement retainer (CR)/stinger; tubing punch, cement packer installation, perforation, and stand-alone-screen (SAS) installation. The depleted reservoir interval presents challenges with declining production amidst gas lift support and intermittent production attributed to liquid loading. 152 bbl (2,420 ft) of 15.9-lbm/gal cement packer was installed through CT in the 4 1/2- and 9 5/8-in. casing annulus and 656 ft of cement plug on the CR in the 4 1/2-in. tubing.
The use of 1.75-in. OD CT and catenary system effectively overcame the deck space and load bearing constraint of the platform while the 125K unit was used for improved CT reach and higher injector snub/pull capacity. Post-job shut-in tubing and casing pressures, quantity of cement slurry pumped, and extended flow test have proven the success of the design and procedure implemented. The operation was executed successfully using CT compared to the more expensive option of workover rig options for field redevelopment.
Evaluation of Interfacial Friction Models in Stratified Flow: Gas-Liquid Two-Phase Flow
Authors: Abegunde Mobolaji , Briggs Tobinson , Abam Fidelis , Awolola Tayo 
Published: July 2019

Abstract
This research entails evaluation of existing interfacial friction factor, gas-wall shear stress, and liquid wall shear stress correlations for the prediction of liquid holdup in pipelines. In addition, a statistical analysis was conducted on the predicted and measured flow parameters. Stratified horizontal two-phase flow equation was used in deriving an equation that solves for liquid holdup that is dependent on the interfacial shear stress. The model was implemented in a MATLAB integrated development environment to observe the effect of interfacial friction factors obtained from existing correlations. The results obtained from the comparative study of selected friction factors indicate that some of the correlations show high deviation from experimentally determined values. The largest deviation was observed in the model proposed by Sinai which was because of the condition for which it was originally developed is not suited for horizontal stratified two-phase gas-liquid flow. It was also observed that the correlation of Petalas and Aziz gave the best result and least deviation from the measured values. The performance of each correlation was observed to vary with the assumed values of liquid height. All the correlations gave good predictions at 30% liquid height but performed poorly at 40% liquid height.
Unconventional Approach to Managing Kick During Gas Well Drilling
Authors: Hannah Kpone-Tonwe , Gbenga Maku , Micheal Ike , Khalid Olagunju , Olaniyi Ojo , James Omeke 
Published: July 2019

Abstract
Interruption in drilling operation occurs when drilling bit penetrates permeable gas sand with formation pressure greater than the pressure exerted by the drilling fluid in use. Consequently, due to pressure imbalance, there is an extraneous influx of gas into the wellbore, which would bring the drilling progress to a stop as it is necessary to restore pressure/fluid equilibrium throughout the system to contain the kick.
This study presents a case study where a gas kick was unconventionally managed.
While drilling 8 ½" hole at 11,682 ft, a mud gush shooting up through the rotary table to the stabbing board was observed. In attempt to shut-in the well, an accidental shear of the pipe at the surface occurred with the top of fish at 51 ft and with no means of circulating out the influx from the bottom of the well. Due to the well control issue, the cut pipe could not be reached to mill the top of the fish, prior to engaging same. The well was therefore put under control employing Lubricate and Bleed (LB) approach, which is a well control procedure applied in peculiar cases or situation, this is a method or procedure of removing gas in hole when there is no possible way of circulation. The sheared pipe located at about 52 ft below rotary, the Top Of fish was dressed from 51ft to 52ft and the string was eventually severed at 11460 ft, the rest 222 ft of fish was recovered using Overshot, Burn Shoe and Wash-Over assembly.
With the effective application of the LB approach, the well was restored, and fish recovered within a relatively short period of time such that values weren't eroded.
The approach employed in this study could be applied in a case of accidental shearing of the pipe such that the whole drilling progress is not brought to a total stop. The consequence of not exploring this approach is an additional cost of drilling a sidetrack well or totally abandoning the well. This paper can be used as a training tool to sharpen and build confidence in tackling well control using volumetric bleeding method. As this method is rare, and not simulated for during most well control certification exercises, it will be beneficial to a practicing engineer and can reduce some of the errors that could occur in a rare case of sheared pipe / well control.
A Case Study of Sustained Annulus Pressure Diagnosis in a Newly Drilled High-Pressure Gas Well in SPDC
Authors: Adebayo Adejoke , Daodu Olugbenga , Ezenobi Eric , David Olayinka , Laoye Abiodun , Komolafe Gbenga , Dennar Linda , Nwandu Somtochi , Chidiebere Christabel , Ahmed Suleiman , Uyouko Ime 
Published: July 2019

Abstract
Well integrity is a key focus area in any oil and gas development. There have been several cases of well integrity issues which have resulted in scenarios of blowout, loss of lives, assets, and reputation, including costs spent for clean-up and environmental remediation, amongst others. These and more have made the energy industry put a keen focus to making sure all hydrocarbon production and processing facilities are integral, with newer technologies still being developed to aid the diagnosis of well integrity problems.
Well integrity considerations cut across the entire life cycle of the well, from well conceptualization/planning through to drilling, completion, production and abandonment. This case study presents a high-pressure, high temperature gas well with sustained annulus pressure in the early production phase of the well.
Well X is a gas well completed in an elevated pressure and temperature reservoir on a land terrain. The reservoir is about 13000ftss deep, with a temperature of 219°F and a reservoir pressure of 9300psi. The well was completed, cleaned up and brought to production about a year ago and annular pressures were observed.
This paper details the different approaches used in diagnosing the sustained annular pressures – separating thermal effect from sustained pressure due to leak. It shows the different scenarios of leak paths identified and how these were streamlined.
The paper also highlights the integration of data acquired during the investigation. Some of the data acquired include well annuli pressures, high precision temperature logs, spectral noise logs and electromagnetic corrosion logs.
Egina Deep Water Development Completion Success: One Team Working Together Setting New Performance Standards
Authors: Okpalla C. , Chaloupka V. , Djenani R. , Okengwu V. , Akinniyi T. , Orluwosu B. , Johnson K. 
Published: July 2019

Abstract
A service company was challenged to deliver best-in-class upper and lower completions by leveraging deep water completion experiences throughout West Africa with the operator and service company's global best practices and lessons learned. An operator reduced lower completion times, standalone screens, and openhole gravel packs by 60% between the 1st and 24th well while reducing upper completion times by 40% for the same wells. Well construction durations, including drilling and completion, currently averages 24 days per well, with lower and upper completion operating efficiencies and run reliabilities exceeding 97%.
Machine Learning Application to Permeability Prediction Using Log & Core Measurements: A Realistic Workflow Application for Reservoir Characterization
Authors: Eriavbe Francis E. , Okene Uzoamaka O. 
Published: July 2019

Abstract
The use of Artificial Intelligence continues to grow in popularity within the geosciences in view of ever-growing complexity and magnitude of available subsurface data. This is equally evident by the need for faster and accurate interpretations required to find hydrocarbons in ever more challenging and increasingly complex basins. This drive is made necessary in a continuously evolving and cost conscious petroleum industry business environment.
Advances in computing architecture now easily allows for more common application of machine learning techniques in day to day geoscience workflows. The use of machine learning in permeability prediction is becoming ever more common place as more specialists adopt this technique for modelling and prediction purposes. Typical machine learning techniques include Fuzzy Logic, Artificial Neural Networks (ANN) and Self Organizing Maps (SOM) amongst others which are run both in supervised and unsupervised modes. The described workflow in this paper was carried out using an available commercial standard petrophysical package with ANN built in modules. This paper describes a typical workflow for predicting reservoir permeability based on an integrated workflow utilizing core measurements integrated with available log data.
Permeability is a key rock parameter for understanding fluid flow dynamics and flow rates and its modelling usually poses some unique challenges. Traditionally and statistically, this can be done at a fairly coarse level in cored wells by utilizing Poro-Perm correlations that usually do not capture fine scale variability observed at core scale measurement. These Poro-Perm transforms are subsequently applied on uncored wells to predict permeability. This paper analyses a workflow that aims to utilize a depth-normalized log and core data set trained using an Artificial Neural Network (ANN) module, blind tested on few key cored wells and subsequently used to predict permeability in uncored wells. In conclusion, the recommended workflow will ensure much more realistic and better matching permeability predictions.
Production Enhancement Using Microemulsion Technology in Rona Field
Authors: Akinnurun Yomi , Dagogo-Jack Cyrusba , Okogbue Innocent , Ogweda Mutana , Afoaku Anthony , Dinyelu Tochukwu 
Published: July 2019

Abstract
Productivity impairment has been a reoccurring issue within the life cycle of wells globally. This is consequent on various factors which include near wellbore damage. The cause and extent of near wellbore damage for suspected wells, can be understood by evaluating the inflow performance, alongside a systemic understanding of the asset and identification of exceptions from expected trends. Some of the major deterrents to the remediation of near wellbore damage include, poor selection of candidate wells and improper selection/deployment of the remediation technology. Microemulsion fluids have been successfully deployed to effectively manage the persistent problem of near-wellbore damage in Rona Field. This technical paper describes the steps taken to implement a successful rigless microemulsion stimulation job (matrix stimulation) on two wells in Rona Field, which resulted in total production gain of about 1400 BOPD.
In the course of this work, a structured candidate screening exercise was carried out on the wells and reservoirs in Rona Field, by leveraging embedded analytics in SEPAL well, reservoir and facility management (WRFM) tool to identify wells with impaired productivity due to formation damage. Thereafter, a carefully designed Microemulsion treatment system having an ultra-low interfacial tension, high solvency and compatibility with the formation fluids was formulated and deployed.
The Microemulsion stimulation treatment resulted in approximately 411% and 30% increment in oil rates for RONA-07S and RONA-12S respectively. The lessons learnt, best practices adopted on the execution of the job, together with the operational challenges encountered and how they were resolved will be discussed in this paper.
Developing Deep Learning Continuous Risk Models for Early Adverse Event Prediction in Electronic Health Records: an AKI Case Study
Authors: Tomašev Nenad , Glorot Xavier , Rae Jack W. , Zielinski Michal , Askham Harry , Saraiva Andre , Mottram Anne , Meyer Clemens , Ravuri Suman , Protsyuk Ivan , Connell Alistair , Hughes Cían O. , Karthikesalingam Alan , Cornebise Julien , Montgomery Hugh , Rees Geraint , Laing Chris , Baker Clifton R. , Peterson Kelly , Reeves Ruth , Hassabis Demis , King Dominic , Suleyman Mustafa , Back Trevor , Nielson Christopher , Ledsam Joseph R. , Mohamed Shakir 
Published: July 2019

Abstract
Early detection of patient deterioration is key to unlocking the potential for targeted preventative care and improving patient outcomes. This protocol describes a workflow for developing deep learning continuous risk models for early prediction of future acute adverse events from electronic health records (EHR), taking the prediction of the risk of future acute kidney injury (AKI) as an exemplar. The protocol consists of 34 steps grouped into the following stages: formal problem definition, data processing, model architecture selection, risk calibration and uncertainty, and evaluating model generalisability. For the protocol to be applicable to modelling the future risk of a particular condition, the problem formulation should be clinically and physiologically plausible and there needs to be sufficient associated predictive signal in routinely collected EHR data. Prospective validation is key in evaluating whether retrospective models developed by following the proposed protocol are clinically applicable and useful.
No one accelerometer-based physical activity data collection protocol can fit all research questions
Authors: Bergman Patrick , Hagströmer Maria 
Published: July 2019

Abstract
BACKGROUND Measuring physical activity and sedentary behavior accurately remains a challenge. When describing the uncertainty of mean values or when making group comparisons, minimising Standard Error of the Mean (SEM) is important. The sample size and the number of repeated observations within each subject influence the size of the SEM. In this study we have investigated how different combinations of sample sizes and repeated observations influence the magnitude of the SEM.
METHODS A convenience sample were asked to wear an accelerometer for 28 consecutive days. Based on the within and between subject variances the SEM for the different combinations of sample sizes and number of monitored days was calculated.
RESULTS Fifty subjects (67% women, mean±SD age 41±19 years) were included. The analyses showed, independent of which intensity level of physical activity or how measurement protocol was designed, that the largest reductions in SEM was seen as the sample size were increased. The same magnitude in reductions to SEM was not seen for increasing the number of repeated measurement days within each subject.
CONCLUSION The most effective way of reducing the SEM is to have a large sample size rather than a long observation period within each individual. Even though the importance of reducing the SEM to increase the power of detecting differences between groups is well-known it is seldom considered when developing appropriate protocols for accelerometer based research. Therefore the results presented herein serves to highlight this fact and have the potential to stimulate debate and challenge current best practice recommendations of accelerometer based physical activity research.