bluuebunny/crossref_metadata_2025 huggingface dataset:
Decreasing Trends in HIV Testing among Adults in Georgia: Analysis of the 2010-2014 BRFSS Data
Authors: Ansa Benjamin E. , White Sashia , Chung Yunmi , Smith Selina A.
Published: September 2016

Georgia is ranked fifth highest among states for rates of HIV diagnosis. About 4% of persons living with HIV infection in the United States reside in Georgia, and almost 19% of these people do not know their HIV status. The present study examined the trends and associated factors of HIV testing among adults in Georgia between 2010 and 2014 by analyzing data of the Behavioral Risk Factor Surveillance System (BRFSS). A total of 30,791 persons aged ≥18 years were identified who responded to the question “Have you ever been tested for HIV?” Overall, there were 11,543 respondents who had been tested for HIV, with a decrease in percentage from 49.4% in 2010 to 43.7% in 2014 (p<0.001). Factors associated with HIV testing were being black (p<0.001), being younger than 55 years (p<0.001), single (p=0.02), attaining education level above high school (P<0.001), engaging in HIV high-risk behaviors (p<0.001), and not having healthcare coverage (p=0.03). Overall in Georgia, there has been a decline in the temporal trend of HIV testing, and more than half of adults have never been tested for HIV. For reducing HIV transmission in Georgia, enhancing access and utilization of HIV testing should be a public health priority.
Current Research on the Speciation and Determination of Mercury in Different Environmental Matrices Using Various Analytical Instruments
Authors: Suvarapu Lakshmi Narayana , Baek Sung-Ok
Published: September 2016

This paper reviews the current research on the speciation and determination of mercury by various analytical instruments such as, atomic absorption spectrometer (AAS), voltammeter, inductively coupled plasma optical emission spectrometer (ICP-OES), ICP-atomic emission spectrometer (AES), ICP-mass spectrometer (MS), atomic fluorescence spectrometer (AFS), spectrophotometer, spectrofluorometer, and high performance liquid chromatography (HPLC). Approximately 126 research papers on the speciation and determination of mercury by various analytical instruments published in international journals since 2015 are reviewed. All the analytical parameters, such as limit of detection, linearity range, quality assurance and quality control studies, applicability, and interfering ions studies evaluated in the reviewed articles are tabulated. This review find outs the lack of information on speciation studies of mercury in recent years. Another important prediction from this review is authors are not much studied about the concentrations of mercury in the atmosphere.
Using Lagging and Leading Indicators and the Importance of Benchmarking Contractor Performance
Authors: Bibby David
Published: September 2016

Statistics show what gets measured gets done. Measuring and benchmarking contractor performance is a key driver of continual health and safety efforts in the oil and gas industry. Our research, drawn from 15 years of global experience with 450+ Clients and 60,000+ contractors, highlights the key leading and lagging performance indicators used in the oil and gas industry and introduces leading edge methods to identify vital Key Performance Indicators.

Monitoring and benchmarking tools such as collection and tracking of contractor work hours, incident rates, action items, evaluations and written health and safety procedures are all crucial to effective ongoing management of contractor performance. In addition, having a system for contractors to be able to identify potential safety system gaps that may need their attention, can further drive improvements.

Our paper demonstrates some basic data trending and analysis methods plus leading edge methods, including regression and correlation statistical analysis approaches being used in the industry to identify factors that are positively or negatively associated with increased or decreased health and safety performance. Such methods are useful in identifying vital Key Performance Indicators (KPI's) to measure and monitor. Real world analytical examples will be presented and discussed.

Using data driven hiring decisions is a vital part of any prevention plan. Through use of a system for managing and evaluating contractor safety data, Clients have seen significant improvement in their contractors' performance. Case studies of clients who have seen improvement of more than 90% for their contractors' incident rates will be discussed.
New Diblock Copolymers as Fluid Loss Additive for High Temperature Cementing
Authors: Cadix A. , Wilson J. , Phan Ch. , Villafane L. , Gomez J.-R. , Bzducha W. , Feuillette A. , Poix-Davaine C. , Thant K. , Nelson T.
Published: September 2016

Oil well cementing uses a variety of organic additives such as dispersing agents, retarders or fluid loss control additives. The latter, which prevent water from filtering into the formation during cement placement, are generally polymer based and a widely used category of fluid loss control additives are high molecular weight sulfonated copolymers, generally comprising AMPS. The mechanism of action of these polymers has been studied recently and it was demonstrated that adsorption onto the cement surface is key to the achieve product performance. Unfortunately this adsorption yield is limited at elevated temperature. Desorption or limited adsorption is generally observed as temperature increases and as a consequence fluid loss control performance becomes worse. In order to overcome that loss, formulators typically increase loading to regain acceptable performance.

Due to the high molecular weight nature of these AMPS copolymers, the subsequent drawback of increased loading is also an increase in cement slurry viscosity. In addition, as higher density slurries are typically used when downhole temperature increases, the problem is exacerbated and these limitations highlight the need for alternative technologies.

In this study we investigated the use of block copolymers comprising first a strong adsorbing block, then a long second hydrophilic block providing filtration control. This technology has already demonstrated to be very effective in preventing performance losses in presence of competitive formulation additives such as dispersant or retarders (see SPE173758). In addition, in this work, the behavior of such fluid loss additive versus temperature is investigated. Thanks to a systematic methodology evaluating HP/HT filtration cell filtrates, it is possible to quantify fluid loss polymer adsorption. This methodology applies even in the case of complex formulations comprising retarders.

This work focuses on the analysis of the adsorption of diblock copolymers on cement particles versus conditioning temperature and the correlation with actual fluid loss control performance.

Block copolymer fluid loss control performance is demonstrated to be insensitive to temperature from room temperature up to 400°F. In addition, this performance is demonstrated to be directly linked to the adsorption level on cement surface. This adsorption and fluid loss performance has been demonstrated to be robust with respect to the formulation ingredients such as retarders needed to ensure acceptable thickening time for high temperature application.

Diblock copolymers demonstrated outstanding fluid loss control at low doses at elevated temperature with a very minor impact on slurry rheology. Indeed, diblock copolymers with relatively low molecular weight are able to deliver fluid loss performance.
How Many Back Up Prepared For Asphaltene Onset Pressure Measurement Using Costly Collected Single Phase Bottomhole Fluid Samples?
Authors: Yonebayashi Hideharu , Miyagawa Yoshihiro , Ikarashi Masayuki , Watanabe Takumi , Maeda Haruo , Yazawa Nintoku
Published: September 2016

For more accurate understandings of asphaltene flow assurance, nobody doubts the importance of asphaltene onset pressure (AOP) as direct information from live oil. For this purpose, a single phased bottomhole sample (BHS) has been taken as a standard process of the asphaltene flow assurance study even though expensive. This fluid sample is storing the closest information to the most representative in-situ asphaltene condition. Because of costly collected fluid sample, its handling and the examination using such a sample are carefully carried out to avoid unfavorable results and/or waste of sampling cost. However, unexpected experimental difficulties sometimes cause to result failure of AOP detection. In our AOP measuring experience, the latest method: laser light scattering technique (LST) has been applied because of its convenient and no time-consuming procedure. Our measuring equipment consists of the solid detection system (SDS) using LST as main function to judge AOP by power of light transmitted (PLT). In addition to the SDS, the apparatus consists of other measuring functions simultaneously: namely high pressure microscope (HPM) to observe asphaltene particle count and size visually, densitometer and viscometer to investigate the fluid kinetics. In this paper, these measuring functions were demonstrated as quite useful back up options to judge AOP when the SDS PLT results could not decide AOP solely. This demonstration can contribute maximizing data acquisition and use of the costly sample as much as possible. Furthermore, the paper describes that the AOP interpretation based on each kind of measured data would be aligned in order related to asphaltene particle growing condition because detection limits in each measurement were reflected into the AOP interpretation. In summary, the comprehensive interpretation can achieve AOP quality higher, and different measuring types of data basis interpretation would be possibly used as support data in each.
Impact of Improved Neutron-Gamma Density Measurement while Drilling in Formation Evaluation - A Case Study
Authors: Mahiout Said , Belowi Ali , Alqunais Ali , Mohamed Jad Kareem
Published: September 2016

Measurements from pulsed neutron devices have been available via wireline conveyance for more than three decades. Based on recent technology developments, their use has now been expanded to the logging while drilling (LWD) environments. Pulsed neutron generators (PNGs) are electronic devices that produce high energy neutrons without the use of traditional chemical sources. Measurements available for the first time from a commercial PNG-based LWD service include neutron-gamma density (NGD) for bulk density and density porosity.

Extensive testing for neutron-gamma density was conducted in a diverse range of environments. Therefore, NGD was put under a benchmarking process against traditional gamma-gamma density (GGD). Consequently, comparing results from both density measurements will allow us to assess the quality of NGD measurement and its limitations; and ultimately qualifying it. Factors such as the invasion and presence of gas or light hydrocarbons may influence the GGD-NGD comparison.

Results from various field testing of the NGD measurement while drilling that were recorded in a wide range of environmental conditions and formations indicate that in some cases, they require additional work to accurately characterize the measurement for quantitative analysis. Advantages and limitations of this measurement while drilling (NGD) technique will be highlighted and illustrated in the paper.
Optimizing a Unique New Generation LWD Technology for Petrophysical Evaluation, Well-Placement, Geological Mapping and Completion Design-Carbonate Reservoir Case Study
Authors: Lutfallah Mustafa , Hibler A. Patrick , Mishra Ashish , Babayeju Oludiran , Hassan El-Saied , Al-Buqshi Mustafa , Al Mubarak Mustafa Ahmad
Published: September 2016

The task of drilling and completing horizontal development wells in carbonate reservoirs can prove to be quite difficult, especially in the well placement and completion design stages. These stages of well construction can be particularly challenging when the reservoir is characterized by natural fracture systems which can result in drilling fluid losses, or when drilling with narrow TVD targets. The utilization of high resolution borehole images to optimize petrophysical evaluation, well placement, and completion design becomes a necessity for reservoir evaluation team. This paper will present a case study of how this new LWD technology optimized well placement, and completion design.

During the pre-job planning stage, numerous scenarios are considered to assist in determining which "bundle" of logging technology is best suited to achieve the objectives of drilling the well. Optimizing logging design specifications required to meet the objectives may not be a simple job. For instance, placing the lateral near the roof of the reservoir while getting resistivity measurements that are least affected by overlying beds would seem to be irreconcilable. Similarly, acquiring high quality resolution image data in the event of borehole deterioration associated with total drilling fluid losses is a difficult task to achieve.

In this case study, the technology is shown to successfully "geo-steer" within a single thin layer of the reservoir and achieved a 100% net-to-gross while simultaneously placing the wellbore near the roof. The real-time high resolution image was of sufficient quality used to identify sub-seismic faults, natural conductive fractures, karst dissolution features, healed fractures and drilling induced fractures as the well was being drilled.

Once the well was drilled to the planned total depth, the high resolution image data could be used for the completion design, thereby saving the time, expense, and risk of an additional logging run using pipe-conveyed wireline logging tools. In addition to the completion design, high confidence dip data were used to update the geological models, fracture porosity and aperture were computed from the images and the shallow focused resistivity measurements were used for more accurate saturation calculations.
Scaling Deposition Behavior in Sieve Tubes of Produced Water Filter in Polymer Flooding
Authors: Wang Zhihua , Li Jiexun , Yu Xueying , Wang Mingxin , Le Xinpeng , Yu Tianyu
Published: September 2016

A green field development might face many challenges such as water source shortage, wastewater accumulation, discharging pollution, and purifying effect. The polymer flooding produced water (PFPW) with complex characteristics would lead to scaling deposition behavior, and the sediment compaction even appears in sieve tubes when filtering. Overall consideration of prevention and removal to scale in sieve tubes is an effective method to address the challenges. An investigation of produced water scaling and depositing in sieve tubes of sand filter in Daqing Oilfield was recently carried out, and a laboratory test was performed for characterizing the properties of scaling sediments. The scaling deposition behavior occurring in sieve tubes was identified and simulated, and the mechanism was discussed. The methods of scale prevention and removal were screened in consideration of operational feasibility and economical justification, and then the field practice effect was presented and assessed.

The results show that the filter of disposing PFPW is mainly destroyed by the pressure locking which originates from the occurrence of scaling deposition in water collecting sieve tubes. The sediments are accumulated with sulphides, carbonate scale, silicate scale, dirty oil and degradable polymer. The deposition in sieve tubes is affected by the residual polymer in a great degree. The major impact of temperature threshold value is facilitating under-deposit corrosion. It is beneficial for the scaling deposition prevention by utilizing the anti-wear ceramics materials to replace carbon steel. The acid pickling operation could realize the effective removal to scale by integrating the dispersing, stripping, dissolving, deactivating, flushing, carrying and discharging mechanisms, and the acid fluid system is screened with which primary solvent is 10% hydrochloric acid. Furthermore, the field practice case indicates that the oil and suspended solids content of purified water reduced by 21.71% and 26.58%, respectively, the water consumption in backwashing process was multiplied, and the accumulation of sediments dropped by more than 50% in same running period. This study is significant to the understanding of scaling behavior in enhanced oil recovery (EOR) surface facilities, and it is also beneficial to provide an auxiliary technology of disposing PFPW.
Quantifying Anisotropy for Completion Optimization in Shale Using Dipole Sonic Logging
Authors: Kinoshita Toshihiro , Wago Toshimichi , Tohda Masahide , Sakiyama Naoki , Kajikawa Yohei , Endo Takeshi , Bammi Sachin , Wells Peter , Velez Edgar , Shigekane Akito , Wada Yuichiro
Published: September 2016

The quantification of anisotropy in horizontal wells, common in shale reservoirs, with dipole sonic featuring a unique through-the-bit conveyance is presented. Anisotropy and fracture evaluation with multipole sonic logging provides essential information for designing completions and optimizing perforation performance. Multiple case studies demonstrate the contribution of measurements for optimized completion quality and increased production.

The small-diameter logging tool can be conveyed through the drillstring using mud pump flow to deliver the tool out through a specialized bit to the open borehole. The formation survey is conducted in memory mode while the drillpipe is tripped out of the hole. Based on intensive numerical modeling, the tool structure has been optimized to sufficiently suppress the tool-borne acoustic waves and allow measurements in fast formations. The tool is designed to be well-centralized in horizontal and highly deviated wells to ensure robust cross-dipole measurements for the estimation of anisotropic stress and orientation.

The tool characterization in reference formations with known characteristics indicates that the logging tool response is in agreement with the model predictions; therefore, the tool presence effect can be fully compensated for in the processing as a function of borehole size, formation and mud properties. More than 100 field jobs have verified high-quality, cross-dipole measurements in unconventional horizontal and high-angle wells, from 4 1/2-in. to 8 3/4-in. borehole. Detailed analysis of the measured data confirmed that the tool is well-centralized in real logging conditions of horizontal wells. It was also confirmed that the transmitters generating monopole and dipole waves provide sufficiently wide frequency band excitation to extract information from the borehole signal. Case studies show that anisotropy ranging from 3% to 40% was extracted reliably as later verified with other measurements. Incorporating the anisotropy of the rock into the horizontal stress estimation enabled the operator to optimize engineered completions. The substantially greater confidence in the accuracy and reliability of the completion directly impacted the perforation efficiency and ultimately the well production.

The new tool is an enabler for quantifying anisotropy with cross-dipole as well as fracture analysis with Stoneley to evaluate horizontal and high-angle wells with minimal cost, leveraging a unique low-risk and driller-friendly conveyance system. It can easily be included into existing drilling and tripping plans.
Ensemble-Based Assisted History Matching With Rigorous Uncertainty Quantification Applied to a Naturally Fractured Carbonate Reservoir
Authors: Maucec Marko , De Matos Ravanelli Fabio M. , Lyngra Stig , Zhang Shu J. , Alramadhan Aymen A. , Abdelhamid Osama A. , Al-Garni Saad A.
Published: September 2016

This paper presents an ensemble-based computer Assisted History Matching (AHM) of a real life carbonate oil field. The field-level reservoir pressures were matched with a fine-scale Dual-Porosity DualPermeability (DPDP) model spanning a long production history under primarily peripheral water injection pressure support.

The well-level AHM workflow presented was validated with a DPDP high-resolution sector model of a fracture dominated carbonate reservoir. This sector model was ~17 million active grid cells with no application of simulation grid upscaling. The AHM workflow integrates probabilistic Bayesian inference using Ensemble Smoother with Multiple Data Assimilation (ES-MDA), which simultaneously assimilates the data and generates maximum a-posteriori updates of reservoir model parameters in a variance- minimizing update scheme. A detailed uncertainty matrix was built with ensemble of sensitivity scenarios, based on varying free water level, corresponding matrix porosity and the initial water saturation combined with geostatistical realizations of dynamic permeability derived from dynamic PLT logs and fracture characterization, where the varied parameters were the variogram attributes in terms of correlation length and geometric anisotropy.

Five data assimilation iterations with ES-MDA method were required to achieve acceptable convergence and minimization of objective function, defined as a joint misfit of well-level static pressures and watercut for the key producing wells. Practical DPDP model simulation times were achieved through utilization of Massive Parallel Processing technology.

This study presents the first ensemble-based approach to integrated reservoir modeling for a mature oil field with the objective to deliver geologically-constrained history matched models with better predictive value for production optimization and forecasting.
An Investigation on Propagation Mechanisms of Steam Chamber during Expanding Solvent SAGP ES-SAGP in Thin Heavy Oil Reservoirs
Authors: Pang Zhanxi , Wang Lei , Lv Xiaocong , Liu Yongge , Wu Guanghuan , Wei Tao
Published: September 2016

Steam assisted steam drainage (SAGD) or steam and gas push (SAGP) is commercially utilized to recover bitumen from oil sands. It produces higher oil rate and ultimate recovery than the other thermal recovery methods. But for thin heavy oil reservoirs, the recovery is lower resulting from larger heat losses through cap-rock and poorer oil mobility under reservoir conditions. A new EOR method, ES-SAGP, is introduced to develop this kind of reservoir. That is to say, non-condensate gas and vaporizable solvent is injected with steam into steam chamber during SAGD. The scaled 3D physical simulation was employed to examine the effectiveness of ES-SAGP and analyze propagation mechanisms of steam chamber. Under the same experimental conditions, a contrast analysis about the expanding characteristics of steam chamber, the swept efficiency of steam chamber and the ultimate oil recovery were carried out between SAGP and ES-SAGP. The experimental results shows that the steam chamber gradually becomes an ellipse shape during SAGP; However, during ES-SAGP, non-condensate gas and vaporizable solvent gather at reservoir top to decrease heat losses, and oil viscosity near condensate layer of steam chamber is largely decreased both by hot steam and solvent, which makes the boundary of steam chamber vertical and gradually become a shape of similar rectangle. During ES-SAGP in thin reservoir, the expanding processes of steam chamber can be divided three stages including ascent stage, horizontal expanding stage and decline stage. During the ascent stage of steam chamber, the needed time is shorter than SAGP. The stages of horizontal expanding and decline consume more time during injecting nitrogen, solvent and steam to enlarge cross-section area of steam chamber bottom. When the instantaneous oil-steam ratio is lower than 0.1, the swept efficiency of steam chamber is over 75% and the ultimate oil recovery is 45.7%, which is 7.4% higher than SAGP. Therefore, during ES-SAGP, not only the volume of steam chamber is largely enlarged, but also the swept efficiency and the ultimate oil recovery are remarkably improved.
Workover Operations Optimized in Tubingless Water Injectors through Comprehensive Analysis of Rigless Well Securement Practices
Authors: Al-Hajri Nasser M. , Al-Subaie Fehead M. , Al-Ajmi Mohammed D.
Published: September 2016

This paper will present the results of a dedicated analysis, which includes 56 case studies with the purpose of optimizing workover operations by assessing rigless well securement practices. The scope of work is concentrated on the evaluation of two industry-known plugs, utilized to secure tubingless water injectors. The two plugs were cast iron bridge plugs and high expansion slim plugs capped with cement. The main areas of study were as follows: rigless deployment, durability and reliability, removal during workover operations, and economic feasibility.

The rigless deployment of each plug was contrasted with regards to testing requirements, setting time, and capping with cement requirements. The reliability of each plug was scrutinized by reviewing 24 wells secured under cross flow dynamic conditions which is one of the most challenging aspects of securing tubingless water injectors. This dedicated review was aimed at ensuring safety of the well and the subsequent workover, preventing environmental impacts, and making proper conclusions with regards to plug reliability.

The milling performance of each plug was analyzed using three criteria: 1) plug milling time 2) plug chasing to plug-back total depth (PBTD) 3) number of additional trips required to mill the plug completely. Based on the plugs performances during workover operations, the relevant cost statistics were generated.

Additionally, an economic feasibility study was performed, bearing in mind the cost environments associated with workover rigs. The specifications of the plugs under study and corresponding pressure ratings were taken into consideration in this work. The development of this paper is aimed at reviewing current practices through available statistical and engineering tools, and to ultimately enhance the operational process and improve its quality.
Well Performance Calculations for Artificial Lift Screening
Authors: Kefford P. A. , Gaurav M.
Published: September 2016

Having the means to efficiently evaluate different forms of artificial lift early in the planning cycle significantly improves the ability to influence other planning decisions (well count, well design, facility capacities etc.) and to realise the potential upsides made available by new artificial lift technologies. Artificial lift screening involves evaluating multiple criteria including rate, well design, cost, reliability, environmental impact, flow assurance, solids handling, operability etc. This paper focusses on a fit-for-purpose methodology to evaluate well production performance for a wide range of artificial lift techniques including Electric Submersible Pumps, Gas Lift, Sucker Rod Pumps, Progressing Cavity Pumps, Jet Pumps, Hydraulic Submersible Pumps and Hydraulic Piston Pumps. The five important attributes of the methodology presented are: Consistency: To ensure a fair comparison is made when evaluating each lift technique, the same assumptions about reservoir performance, fluid properties, multi-phase flow behaviour, geomechanics etc. are used.Auditability: Later in the development planning process, decisions and assumptions will inevitably change, and it is important that there is a proper audit trail regarding how artificial lift screening had been performed to help understand the potential impact of these changes.Efficiency: Early in the field planning cycle, many alternative well counts, well designs and facility configurations will be under evaluation, and assumptions about reservoir and fluid properties will be changing as new data become available. It is therefore important that the artificial lift screening method can be readily applied to accommodate the many scenarios.Technical Rigour: While detailed artificial lift design is not required (or desired) at the screening stage, it is important that the screening methodology applies a fit-for-purpose level of technical rigour to ensure reliable results are achieved and opportunities are not missed through the misapplication of various industry ‘rules of thumb’.Vendor Independence: While sufficient industry research is required to understand the available technologies and new innovations, the screening process should be independent of any particular equipment vendor to prevent any undue bias.

The well performance calculations use a nodal analysis approach to develop inflow and outflow curves at the depth of the artificial lift equipment. Then, using knowledge of the fundamental operating principals of the artificial lift techniques, calculations are performed to determine the range of production rates achievable based on constraints including power, flow capacity and gas handling ability.

The paper will also present a range of real field cases where these screening calculations have been applied to deep water subsea, onshore conventional and coalbed methane (CBM) developments.
Modeling of Wormhole Propagation During Matrix Acidizing of Carbonate Reservoirs by Organic Acids and Chelating Agents
Authors: Akanni Olatokunbo O. , Nasr-El-Din Hisham A.
Published: September 2016

Numerous carbonate matrix acidizing models have been developed to study the flow and reaction of Hydrochloric acid (HCl) in calcite, but there is a significant gap in the literature for models built to investigate wormhole propagation by alternative acidizing fluids such as organic acids and chelants. In this work, a model is developed to study wormhole propagation by these alternative fluids, using the two-scale carbonate acidizing model approach with Navier-Stokes formulation for fluid-flow description.

The reaction kinetics used for acetic acid (HAc) in the model is modified to account for the slight dissociation of the weak acid in aqueous solution and a fractional order of reaction. The output from the model is compared with available experimental data in the literature for qualitative and quantitative validation. This study extends the linear first-order reaction kinetics used for HCl in previous two-scale models for the chelating agents ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), with updated dissolution rate constants and dispersion coefficients, and the output compared with experimental data for qualitative validation.

The acid efficiency curves generated from the model for acetic acid compares qualitatively and quantitatively with reported experimental data, and the numerical simulations show that a higher amount of acid will be required to reach breakthrough for acetic acid than for HCl, as expected. The model output for the chelating agents does not match quantitatively with experimental data, but the qualitative trend can be observed from the numerical simulation results. The updated reaction kinetics for acetic acid is extendable to formic acid, which is the other commonly used organic acid in carbonate matrix acidizing, to obtain an equally dependable model output. However, a more complex reaction kinetics will be required to model the multi-step chemistry that occurs in the dissolution of carbonate by chelating agents.

The model developed in this study accurately captures the wormholing phenomena by acetic acid, and it can also be used to predict optimum injection rates for organic acids. The simulation results also show that the model, based on Navier-Stokes momemtum formulation, is computationally less expensive than previous models with the Darcy-Brinkman formulation, and simulations at very high injection rates with this model require less computational time than models developed with the Darcy formulation.
Mismanagement of Oil and Gas Rents in "Oil and Gas Rich Countries": Lessons for Ghana's Nascent Industry – Case Study: Norway and Angola
Authors: Opong Riverson , Klaas Olga , Benson Lamidi Abdul-Latif
Published: September 2016

Oil wealth can either be a curse or a blessing. However with prudent management oil wealth becomes a primary source for economic transformation. The purpose of this research is to investigate the management of oil revenue in some oil rich countries specifically Angola, Nigeria and Norway and draw some lessons for Ghana's nascent oil industry. These factors were identified in the main work and later categorised under three variables namely; stability, dependency and corruption. Using a qualitative study approach, the effects of these factors on the four countries being studied were analysed using the assessments of working papers by the World Bank, CIDCM and the Corruption Perception Index by the Transparency International. The study revealed that the main cause of mismanagement of oil revenue in Nigeria and Angola was the overdependence of the economies of both countries on their oil revenue, diminishing the effectiveness of good governance in both countries. Norway, on the other hand was successful in managing their resources because of good governance, strengthening their long and stable democracy. It concluded that, though the right policies have been put in place to regulate Ghana's petroleum industry, the judiciary system must be empowered to effectively enforce these policies, and the Government must look at investing its oil rent in sustainable developments. This will help the country in achieving their positive targets and not go down the same lane as the other unsuccessful countries in managing their oil revenue.
First Dual Zone Drillstem Test With Acoustic Telemetry Using Multiple Retrievable Packers for Single Trip Testing of Two Independent Reservoirs
Authors: Dolciani Gregory , Tiwari Shrikant , Adewuya Opeyemi , Mousa Ali , Osaimi Falah , Al-Gannas Musab , Gill Harmohan , Martin Adam , Azhar Sheikh Saqib , Zeller Vince
Published: September 2016

Although the main objectives of drillstem testing (DST) have remained largely unchanged over the years, operators are continuously seeking a means of improving operational efficiency (time/cost savings) while maintaining the highest level of operational standards, with safety and the environment being paramount. This paper presents a case history of the first retrievable dual packer testing string used to independently test two reservoirs in a single trip (toolstring conveyance into and out of the hole), which enhances operational efficiency.

This case history is from an offshore exploratory well in Saudi Arabia in which a dual retrievable packer test string was deployed with a real-time telemetry system to successfully test two independent reservoirs in a single trip. Throughout the operation, real-time telemetry data above and below each packer enabled real-time understanding of the operational process and provided assurance of equipment/process integrity before proceeding with the next sequence of well testing operations. In this manner, operations were safely performed step-by-step, ensuring that the well test objectives and zonal isolation were met to determine the individual reservoir evaluation integrity.

With the application of acoustic telemetry technology, the ability to acoustically communicate with and control downhole tools in real time is achieved. Communication to and from the downhole tools also provides the status of the downhole equipment in real time. In addition, knowledge gained from the real-time data enhances the ability of the operators to perform well tests with reduced uncertainties. The early availability of reservoir knowledge enables operational efficiencies, ensuring that test objectives are met, and may reduce the overall test period and significantly reduce well testing costs. The direct result of eliminating multiple trips is that operational efficiency is achieved, enabling the operator to save time and money without compromising data quality or health, safety, and environment standards.

This case history represents a milestone for the industry, demonstrating the successful deployment of multizone testing, and serves as a stepping stone for even greater efficiencies by using real-time telemetry technology. This paper also discusses lessons learned and plans for additional well testing process efficiencies, enhanced with well application selection and DST toolstring acoustic control devices and technology.
Influencing Factors of the Microstructure and Macroscopic Performance of Foamed Cement
Authors: Pang Xueyu , Singh John P. , Jimenez Walmy Cuello , Prince Aaron C.
Published: September 2016

Foamed cement has provided zonal isolation in oil and gas wells since the 1980s. However, the lack of an experimental technique that fully characterizes foamed cement properties is limiting its application. This study uses X-ray microcomputed tomography (micro-CT) to elucidate relationships between the foaming process, foamed cement microstructure or morphology, and macroscopic performance of the material’s mechanical properties.

During this study, foamed cement slurries were prepared using a traditional multiblade laboratory blender to investigate the influencing factors on foamed cement properties. The influences of shear rate, mixing energy, surfactant concentration, and base cement slurry composition on the properties of set foamed cement were specifically studied. A MACS® multiple analysis cement system was also used to study the gas pressure and blender geometry effect on test results. Approximately 25 foamed cement slurries with foam qualities (FQs) ranging from 20 to 80% were produced. The microstructure and macroscopic performance of the foamed cement were quantified using micro-CT analysis and uniaxial compression tests.

Test results indicate there is an important mixing energy threshold value that needs to be supplied to produce stable foamed cement. The maximum achievable FQ is determined by the shear rate during the foaming process. Once the minimum qualifications for obtaining stable foamed cement and a target FQ are met, a further increase in mixing energy or shear rate has little effect on the foamed cement microstructure or macroscopic performance. However, excessive mixing energy supplied at a high shear rate can lead to a higher initial slurry temperature, a less homogenous microstructure, and relatively poor mechanical properties after the foamed cement has set. The primary determining factors of the foamed cement microstructure are FQ and gas pressure. In samples generated using the multiblade laboratory blender at atmospheric conditions, the median gas bubble size increased significantly from 116 µm at 20% FQ to 1400 µm at 80% FQ. The median gas bubble size in the 20% FQ samples generated using the MACS device decreased significantly when gas pressure increased from 133 µm at atmospheric pressure to 39 µm at 1,000 psig.
Production Pressure Drawdown Management for Fractured Horizontal Wells in Shale Gas Formations
Authors: Mirani Ankit , Marongiu-Porcu Matteo , Wang HanYi , Enkababian Philippe
Published: September 2016

The development of unconventional shale gas formations in North America with horizontal multifractured wells is mature enough to identify production malpractices and abnormal productivity declines generally observed within 18 to 24 months of initial production. The primary objective of this study is to address all known causes of these productivity declines and to develop a fully coupled geomechanical-flow simulation model to simulate these production conditions.

This model mimics the impact of depletion-induced in-situ stress variations on short-term and long-term productivity by taking into account several phenomena, such as stress-dependent matrix and natural fracture permeability as well as reduction in hydraulic fracture conductivity due to proppant crushing, deformation, embedment, and fracture-face creep. Matrix permeability evolutions, considering the conflicting effects of non-Darcy flow, and compaction, have also been accounted for in this model. Numerical solutions for simplified hydraulic fracture planar geometries are then obtained using a finite element method (FEM) scheme.

A synthetic case was defined to investigate the effects of each individual phenomenon on short-term and long-term production. Results show that the combined effects of permeability alterations in matrix and natural fractures as well as conductivity losses in hydraulic fractures may result in substantial gas cumulative production loss. The model also reproduces familiar field-observed trends, with lower long-term production corresponding to higher and higher drawdowns. This behavior is attributed to the stress-dependent evolution of reservoir permeability and hydraulic fracture conductivity. The results conclude that ignoring impacts of any of the above phenomena results in overestimation of ultimate recovery. Furthermore, it is shown that proper management of pressure drawdown and the penalty for lower initial production rates in unconventional shale gas reservoirs can yield substantially higher ultimate recovery.

The model is fully versatile and allows modeling and characterization of all profoundly different (on a petrophysical level) shale gas formations as well as proppant materials utilized for the stimulation treatments. This integrated model can be used for optimization of key parameters during the hydraulic fracture design, for fine-tuning production history matching, and, especially, as a predictive tool for pressure drawdown management.
ROP Optimization Using Artificial Intelligence Techniques with Statistical Regression Coupling
Authors: Mantha B. , Samuel R.
Published: September 2016

Predictive data-driven analytics has driven massive interest, primarily because of its successful implementation in several industries. Data-driven modeling and its application to predict downhole environment will prove to be the future of drilling operations, as they hold the potential to optimize highly complex drilling operations. In general, rate of penetration (ROP) optimization involves adjustment of the weight on bit (WOB) and rotary speed (RPM) for efficient drilling. ROP follows a complex relationship with several other parameters such as formation properties, mud properties, mud hydraulics, borehole deviation as well as the size/type of bit.

Traditional regression analysis models have limitations and have limited accuracy while attempting to describe the dependence of one observed quantity on another observed quantity. On the other hand, the artificial intelligence methods face drawbacks trying to understand the physics behind the operations. To ensure the physical and technical feasibility of the prediction, coupling conditions between the two have been developed for the ROP optimization.

In this study, a new model based on statistical regression and artificial neural networks (ANNs) was designed to predict ROP using field data gathered from the North Sea Horizontal Wells. Exploratory analysis was performed to find correlations between variables, followed by measurement of predictor importance to infer relative contributions and weights of inputs. Cross-validation was employed to prevent overtraining of models. Several models such as Step-Wise regression, neural networks (NN, KNN), support vector regression (SVR), classification regression trees (CART), were applied for prediction. Ensemble methods such as Random Forests (RF) and Boosting helped increase accuracy and reduce errors. The algorithm designed was further tested on other wells and was shown to predict with significant accuracy. This proves that several parameters need to be comprehensively considered while optimizing the ROP. Since the algorithm presented here doesn't depend on a single model but rather several predictor models, it can be effectively employed independent of location or formation.
How to Develop a Well Specific Blowout Contingency Plan that Covers Engineering Analysis of the Deployment, Installation, and Soft Shut-In of a Subsea Capping Operation
Authors: Oskarsen Ray T. , Emilsen Morten H. , Paknejad Amir S. , Cargol Mike , See Kwee Choong
Published: September 2016

Post Macondo, industry publications have discussed the equipment, connections, and interfaces needed for capping and containing a blowing subsea well, but they give little insight into developing a well-specific subsea-capping contingency plan. The planning process described here, which has been used successfully on multiple projects and source-control drills, involves assessing the feasibility of deploying a capping stack from a floating vessel, the weight and stability of the capping stack to overcome the force of the blowout jet, and dynamic flow simulations of closing the capping stack outlets without loss of well integrity. This process not only assesses the feasibility, complexity, and risk exposure of the capping operation, but may also justify further planning, studies, or expenditure.
Advanced Inflow Control Device in Horizontal Well Extends Economic Field Life: A Case Study and Technological Overview
Authors: Jalan Shiv Narayan , Kotecha Rohit Kumar , Gazi Naz H. , Al-Sabea Salem , Bu-Qurais Abdullah , Al-Azmi Mohammad Saad , Al-Houti Naser
Published: September 2016

The Passive Inflow Control Device enhances the well productivity and recovery by removing Heel to Toe effect in a homogeneous reservoir and allowing production optimization along the entire horizontal section in case of heterogeneous reservoir. But these ICDs have their own limitations in controlling the high water producing zones in horizontal wells. The introduction of Sliding Sleeve Technology in horizontal wells has added a greater value to ICDs by further controlling water production from undesired zones. The new Advanced Inflow Control Device with sliding sleeve approach is built upon the usefulness of sliding sleeve technology in horizontal wells. This rigless technology can be used to maximize oil production from horizontal wells, save huge rig workover cost and extend the economic life. This paper describes a case study in Greater Burgan Field showing the challenges encountered while drilling the horizontal well and benefits associated with the integration of the passive Inflow Control Devices (ICD) with Sliding Sleeves in complex horizontal wells. After the well was put on production, Production Logging Tool (PLT) was run to identify the high water producing compartments and accordingly plan was made to close these ICDs by mechanically shifting the sliding sleeves. Pre and post DTS survey clearly confirmed the successful closure of high water producing ICDs. Several flow tests were done before and after shifting the sliding sleeves to monitor the reduction in water cut.

A complete case study is presented to permit the readers to know the benefits of using sliding sleeves along with ICDs in horizontal wells and thus improve the hydrocarbon recovery. Leveraged knowledge from this pilot has provided an insight into the capabilities of sliding sleeve type of ICDs.