bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Gas Injection Pressure on the Performance of CO2-Assisted Gravity Drainage Process in Heterogeneous Clastic Reservoirs
Authors: Al-Mudhafar Watheq J. , Rao Dandina N. 
Published: October 2018

Abstract
Many simulation studies have been conducted to investigate the effects of various factors on the Gas-Assisted Gravity Drainage (GAGD) process performance. These factors are controllable to constrain the amount of injected gas and produced oil in the vertical injection and horizontal production wells. One of the most recent simulation studies investigated the effects of six controllable factors: maximum oil production, minimum bottom hole pressure, and maximum water cut in the production wells along with maximum gas injection rate and maximum injection pressure in the injection wells. From that study, it has been concluded that the maximum gas injection pressure in vertical injectors has the highest effect on the performance of GAGD process. In this paper, an extensive simulation study was implemented to further evaluate how is dominant the maximum gas injection pressure to enhance the recovery of bypassed oil through the GAGD process.
Similar to the aforementioned recent study, the current simulation was carried out on the heterogeneous clastic reservoir (main pay) in the South Rumaila oil field, located in Iraq. The EOS-compositional reservoir flow simulation was adopted to evaluate the effectiveness of CO2–GAGD process under different periodic gas injection pressure levels. Design of Experiments and proxy modeling were adopted to obtain the optimal future oil recovery through changing the pressure in an annual basis. Various what–if–scenarios (simulation runs) were created by the Latin Hypercube Sampling and evaluated by the compositional simulation to find the optimal oil recovery. In the optimization process, the purpose was to search for the optimal future oil recovery by optimizing the levels of periodic gas injection pressure. The optimal cumulative oil production, by the end of 10-year prediction period, reached 4.838 MMMSTB of oil production, while the recent optimal GAGD process resulted to obtain 4.6039 MMMSTB of oil production. Therefore, the current optimization approach has led to increasing the oil recovery by 234.1 million barrels.
Lost Time Analysis of Queensland Coal Seam Gas Drilling Data and Where Next for Improvement?
Authors: Rodger Iain , Garnett Andrew 
Published: October 2018

Abstract
Due to the high number of wells required, drilling costs are a significant factor for coal seam gas developments. In order to improve drilling performance (and reduce associated costs) current performance should be analysed to identify areas with potential for improvement. This study makes use of a framework based on the best composite time (BCT) to assess the performance of wells drilled in Queensland, Australia in an example period in 2014-15.
Data recorded by Pason electronic drilling recorders at 970 wells was made available, along with end-of-day reports for 370 of these wells. Scripts written in the Python programming language were implemented to break the 8½ in. drilling stage down into depth sections and automatically generate a best composite time model for each field in the study. Individual well data was compared to this benchmark allowing the drilling performance to be compared to other wells in the same field, and identified removable time was classified as either invisible lost time (ILT) or non-productive time (NPT). In total over 4500 hours, or approximately 49.5% of the total 8½ in. drilling time, was identified as removable time across 828 wells when compared to field specific BCTs.
Causes of ILT and NPT were identified by analysing both numerical data and textual data in daily reports. There is a clear separation in key drilling parametes between the best and worst performing wells. ILT while on bottom correlated with lower recorded RPM, while ILT connecting was associated with extensive reaming and down-hole-cleaning prior to connections, and these are identified as areas which may benefit from data driven optimisation.
An Integrated Methodology for the Unified Optimization of Injection/Production Rates and Surface Waterflooding Pipeline Network Operation Control
Authors: Zhou Xingyuan , Liang Yongtu , Di Pengwei , Xiang Chengcheng , Xin Shengchao , Zhang Haoran 
Published: October 2018

Abstract
As the most commonly used process for the secondary development of oilfields, waterflooding plays a significant role in maintaining reservoir pressure, enhancing oil recovery and achieving high and stable oil production. The previous waterflooding optimization studies usually worked out the optimal injection/production rates but didn't take into account the energy consumed by the surface waterflooding pipeline network system which transfers water from the waterflooding stations to the waterflooding wells. Taking the maximum waterflooding development profit as the objective function, this paper proposes an integrated methodology for the unified optimization of injection/production rates and the operation control of surface waterflooding pipeline network system. The objective function is defined as the oil production income minus the operation cost of the pipeline network. With a given set of injection rates of waterflooding wells, the reservoir numerical simulation is employed to obtain the oil production rates and a mixed integer nonlinear programming (MINLP) model is established for the optimal operation control of the surface waterflooding pipeline network, including the pump schedule of waterflooding stations, flowrate of pipe segments and pressure at each node. A hybrid solving strategy incorporating particle swarm optimization (PSO), linear approximation method, and branch-and-bound algorithm, is proposed for solving the results. The PSO algorithm is adopted to search for the optimal injection rates of waterflooding wells, while the linear approximation method and branch-and-bound algorithm are used for the MINLP model solving. In this study, we took the Daqing waterflooding Oilfield in China as an example. The applicability of the methodology and the stability of the solving strategy are illustrated in detail. It is proved that the proposed methodology could provide the engineers with significant guidelines for the unified optimization of waterflooding process incorporating the reservoir and surface pipeline network.
Application of Low-Carbon, Rodless Artificial Lift in Low-Production, Low-Permeability Oilfields
Authors: Zhu Shijia , Lei Derong , Liu He , Hao Zhongxian , Zhang Lixin 
Published: October 2018

Abstract
The development of a new low-carbon operation mode of artificial lift in high-water-cut oilfields, is significant for reducing energy consumption, improving operation efficiency and lowering production costs of oilfields. The annual electric consumption of the oilfield is increasing year by year. In 2016, the total electric consumption exceeded 35 billion kWh, of which the mechanical production system accounts for 57%.
The rodless artificial lift eliminates the use of the sucker rod, and reduces the installed motor power over 50%. The electric consumption is greatly decreased, while tremendous gain is seen in the system efficiency. Moreover, the application performance is especially good for low-production wells. Under such circumstances, the operation cost of the oilfield declines. The current rodless artificial lift is basically based on two types of pumps, namely submersible plunger pump and submersible direct-drive screw pump.
The submersible plunger pump lifts liquid via vertical reciprocation of the moving body driven by the motor, with daily electric consumption of an individual well decreasing by 46%, from 133.4 kWh to 72.5 kWh. The reduced annual electric cost per well is RMB 14,000, and the annual single-well carbon emission falls by 17.5 tons. As for the submersible direct-drive screw pump, the rotation of the pump is directly motivated by the downhole submersible motor, through which the downhole liquid is elevated to the surface. The daily electric consumption of an individual well decreases by 38.4%, from 224kWh to 138kWh, contributing to the annual electric cost reduction per well of RMB 13,600 and annual carbon emission decline per well of 17.1 tons.
The application of the two types of rodless artificial lift has taken initial shape. The submersible plunger pump has been applied to over 200 wells, and the submersible direct-drive screw pump, over 60 wells. The new low-carbon operation mode of artificial lift is critical for the energy saving, efficiency improvement and consequent cost reduction of oilfields, particularly in cases of the industry downturn triggered by low oil prices.
The Effect of Fines Migration During CO2 Injection Using Pore Scale Characterization
Authors: Othman Faisal , Wang Yamin , Hussain Furqan 
Published: October 2018

Abstract
Recent laboratory studies have shown fines migration induced decrease in rock permeability during CO2 injection. Fines migration is a pore scale phenomenon, yet previous laboratory studies did not conduct comprehensive pore scale characterization. This study utilizes integrated pore scale characterization techniques to study the phenomenon.
We present CO2 injection experiments performed on two Berea sandstone samples. The core samples are characterized using nitrogen permeability, X-ray micro-computed tomography (micro-CT), Scanning Electronic Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS) and Itrax X-ray Fluoresence (XRF) scanning. The core samples were flooded with freshwater, then CO2-saturated water, and finally water-saturated supercritical CO2 (scCO2). To calculate permeability, the pressure difference across the core samples was monitored during these fluid injections. The produced water samples were analysed using Inductively Coupled Plasma-Optical Emission Spectrometry (ICPOES). After the flooding experiment, nitrogen permeability, micro-CT, SEM-EDS and Itrax-XRF scanning was repeated to characterize pore scale damage. Micro-CT image based computations were run to estimate permeability decrease along the core sample length after injection.
Results show dissolution of dolomite and other high density minerals. Mineral dissolution dislodges fines particles which migrate during scCO2 injection. Berea 1 and Berea 2 showed respectively 29% and 13% increase in permeability during CO2-saturated water injection. But after water-saturated scCO2 injection, both Berea 1 and Berea 2 showed 60% decrease in permeability. The permeability damage of the sample can be explained by fines migration and subsequent blockage. SEM-EDS images also show some examples of pore blockage.
Pore Scale Analysis the Formation Dissolution with Capillary Trapping Change for CO2 Injected into Carbonate Reservoir
Authors: Zhang Yihuai , Zhou Yingfang , Lebedev Maxim , Iglauer Stefan 
Published: October 2018

Abstract
CO2 storage in deep reservoir is an efficient way to mitigate climate change. The carbonate reservoir is one of the selected storage sites but which is sensitive to the acidic environment, where the CO2 saturated formation water could be as medium acid in the reservoir condition and hence change the microstructures. However, the capillary trapping mechanism is highly corrected with such microstructures. Thus, fully understand such CO2-water-rock interaction and the related capillary trapping change are very important for the storage security issues. In this paper, we microCT imaged the microstructure change of oolitic limestone sample due to CO2 saturated brine injection, and calculated the capillary pressure based on the fractal theory. We found that the calculated capillary pressure decreased after live brine flooding which indicated a CO2 capillary trapping loss and such calculated capillary pressure change was also highly corrected with the morphology of the dissolved matrix area.
Hydraulic Concentric Tubular Pumping System for Unloading Gas Wells
Authors: Clemens Langbauer , Vita Petr , Gerald Jax , Herbert Hofstätter 
Published: October 2018

Abstract
Conventional artificial lift systems are limited in their application by depth, borehole trajectory and chemistry of the produced media. This paper presents a concentric tubular pumping system, combined with an efficient hydraulic pump to overcome the limitations of existing artificial lift systems and to assure a cost-effective production.
This pumping system consists of a specially designed plunger assembly and barrel combination, which is driven by a hydraulic pressure unit from the surface without any mechanical connection. The hydraulic pump itself can be circulated into and out of the borehole or can be run by slickline, resulting in fast and low-cost operations. The pump is designed to be run as a concentric tubular pumping system with several advantages, especially in enhanced oil recovery and unloading of gas well operations. This new pump type is designed and manufactured in cooperation with the industry and tested at the Montanuniversität Leoben, Austria.
The performance tests have demonstrated the saving potential regarding energy efficiency as well as a reduction in CAPEX and OPEX. The unique design of this pump owns a very low number of moving parts, such no mechanical connection to the surface, and such providing minimal exposure to wear and corrosion. Tests have shown that the pump is very adaptable regarding production rate, which requires just a change in surface hydraulic pressure. Based on experience the concentric tubular pumping system is the best selection for unloading of gas wells to enhance the lifetime of the completions. As a result, of the natural phase separation of liquids and gases, the presented pumping system has shown to be the ideal choice for the usage in all types of wells.
This completely new pump type exceeds the performance of existing artificial lift systems for unloading of gas wells, increases the mean time between failures and reduces the lifting costs essentially. These major issues are most important in times of low gas price.
Optimizing Sand Control Treatments Using Gauge Data
Authors: Jain Samyak , Wassouf Philip , Tibbles Raymond 
Published: October 2018

Abstract
While the importance of pre-job design has always been appreciated, detailed post-job evaluation of gravel pack execution data (both surface and downhole) is equally valuable as it provides a means to learn from past treatments, calibrate models, and improve future designs. Traditionally, post-job analysis has been limited to high-level pack evaluation and failure investigation but has a much wider range of applications in the confirmation of success, better understanding of downhole mechanisms and validation of simulation models. Downhole data analysis techniques can be used to isolate sections of the flow path and develop a more detailed understanding of each stage of the treatment from running in the hole (RIH) to pulling out of the hole (POOH).
Detailed post-job evaluation is often skipped due to the significant effort involved in data handling as well as the lack of a defined workflow and an integrated software tool. This paper provides an overview of the evaluation and calibration of surface and downhole data along with the steps, workflow and tools required to process the data in the easiest and most efficient manner, enabling faster, more detailed and more accurate analysis of operations.
Various case studies are used to demonstrate how post-job evaluation using downhole gauges can be used to efficiently analyse the various stages of the operation including wellbore displacements, reverse and circulating step rate tests and gravel packing operations. A variety of important phenomena are identified and quantified, such as friction pressures, packing mechanisms, fluid displacements, screen plugging and roping, which may otherwise be missed. The paper further illustrates how the defined workflow can maximize the likelihood of success by using post-job evaluation results to better identify and minimize risks during pre-job design stages while reducing the need for excessive safety factors within the operational window.
The analysis workflows introduced here will maximize the value of downhole gauge data and serve as a reference to practicing completion engineers in the efficient processing, analysis and interpretation of post-job data. It can be used to revisit and better understand historical sand control treatments, and continuously improve future treatments.
Rigless Zonal Isolation in High-Permeability and Low-Pressure Sandstone Formations Using an Organically Crosslinked Polymer Sealant: Successful Field Application
Authors: Alshammari Baraa , Rane Nitin , Al Harbi Sultan , Mohammad Safaa , Al-Kinderi Abdullah , Santin Yoann , Matar Khaled 
Published: October 2018

Abstract
This paper describes a rigless and cost-effective field implementation of conformance polymer sealant (CPS) and particulate-CPS (P-CPS) systems used successfully in high-permeability and low-pressure reservoirs for zonal isolation intervention.
The CPS system is an organically crosslinked polymer that is thermally activated to effectively seal the targeted interval. The P-CPS system combines the CPS system with particulates that provide leakoff control to help ensure shallow matrix penetration of the sealant.
The traditional method for zonal isolation consists of rig intervention for cement squeeze, which can be time-consuming and expensive. In high-permeability and low-pressure reservoirs, several unsuccessful attempts can extend the intervention by two or more weeks.
CPS and P-CPS systems provide a predictable and controllable right-angle set time that can help to ensure sealing on the first attempt. These systems do not develop compressive strength, simplifying the cleanup stage by quickly and easily jetting it out of the wellbore with coiled tubing (CT), as opposed to cement that must be drilled/milled out.
This paper describes laboratory evaluations, treatment design methodologies, and two case histories from Kuwait, including one well that produced 1,600 BOPD after reperforations.
Application of Ensemble Variance Analysis in the Development of the Wheatstone Field Startup Strategy
Authors: Flett Matthew , Connell Paul 
Published: October 2018

Abstract
Commencement of initial field production is a unique opportunity to acquire reservoir surveillance information that can inform future reservoir performance. When a field is perturbed from original conditions with first production, there is potential for reservoir property uncertainty reduction by observing pressure measurements at non-producing wells with downhole pressure gauges and comparing the observed signal to a range of simulation model results.
The Wheatstone field, located offshore northwest Australia, has recently commenced production start-up to supply gas to the Wheatstone LNG facility. The operational guidelines required each development well to commence with a single well cleanup flow to the Wheatstone platform. The initial single well cleanup flows of the Wheatstone field allowed scope for the selection of a well flow sequence with observation at non-producing wells.
The recommended sequence of initial cleanup flows was designed with a focus on reducing reservoir uncertainties via the use of Ensemble Variance Analysis (EVA). EVA is a statistical correlation technique which compares the co-variance between two sets of output data with the same set of inputs. For the Wheatstone field well cleanup flow sequence selection, the EVA workflow compared the full field Design of Experiments (DoE) study of field depletion and a series of short early production reservoir simulation DoE studies of the gas field. The co-variance between the two DoE studies was evaluated. The objective of the EVA approach was to determine the startup sequence that would allow for the best opportunity for subsurface uncertainty reduction. This objective was met by ranking multiple cleanup flow sequence scenarios. The key factors considered for sequence selection ranking were the impact on business objectives such as future drilling campaign timing and location of infill wells, as well as insights on reservoir connectivity, gas initially in place and permeability.
The recommended sequence of well cleanup flows uses super-positioning of pressure signal to boost response at observation wells, which improves measurement resolvability. The selected sequence preserves key observation wells for each manifold and reservoir section for as long as possible before those wells were required to be flowed to meet operational requirements. Operational constraints and variations of the startup plan were considered as part of the evaluation.
Improving Outcomes for Oil and Gas Projects Through Better Use of Front End Loading and Decision Analysis
Authors: Newman David , Begg Steve , Welsh Matthew 
Published: October 2018

Abstract
Outcomes for oil and gas projects often fall short of the expectations predicted at project sanction. Appropriate use of Front End Loading (FEL) and Decision Analysis (DA) to achieve high Decision Quality (DQ) should increase the likelihood of achieving better outcomes. However, despite being successful methodologies, research has shown that they are not always applied. The focus of this paper is on how to encourage people to make better use of FEL and DA.
Previous results from this research program have shown two key reasons why FEL and DA are not used more: an over-reliance on ‘experience’ and judgment for decision-making, rather than the use of structured processes; and projects being ‘schedule-driven’, i.e. meeting target dates being the primary objective. This paper focuses on insights from a survey conducted both to answer questions raised by this previous research and test the likely uptake of methods designed to encourage more effective use of FEL and DA/DQ. It shows that there is strong agreement that good FEL leads to better project outcomes, and that the FEL benchmark score is a good indicator of readiness for project sanction. However, perhaps competing with the desire to complete FEL, is the view (of around 2/3 of respondents) that it is important to drive the schedule in order to prevent ‘overworking’ – continued activity that adds little value. All respondents agreed that it is essential: that the decision maker clarifies the frame, scope and criteria for the decision; and to have regular discussions between the decision maker and the project team to bring alignment. However, responses indicated that these only occur in practice around half of the time. Similarly, formal assessments of DQ are made in less than half of key project decisions.
Several novel solutions are proposed for increasing the likelihood of better project outcomes by improving the uptake and use of FEL and DA/DQ. These include: just-in-time training on FEL and DA/DQ; basing performance incentives on achieving high DQ and good FEL; and, developing a simple pragmatic assessment of FEL that can be used in-house. These suggestions were all supported by a majority of survey respondents.