bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heavy Oil Waterflood Application of Capacitance Resistance Models
Authors: Zhang Tiantian , IZGEC Omer , Sayarpour Morteza 
Published: October 2018

Abstract
The capacitance-resistance model (CRM) is an analytical tool that uses only injection and production rate to quantify interwell connectivity and response time during a waterflood. It has been widely used in conventional waterfloods for reservoir characterization, performance evaluation and optimization. Heavy oil waterfloods introduce challenges to the application of CRM due to the high mobility ratio and its rapid variation as a function of waterflood maturity. Using conceptual reservoir models and sensitivity studies, we provide guidelines for application of CRM in heavy oil waterfloods. We illustrate our approach in two heavy oil fields under waterflood.
In heavy oil waterfloods, it is observed that interwell connectivity and response time varied over time, especially right before and after water breakthrough. The magnitude of CRM parameter variation is a function of viscosity ratio between water and oil, flood maturity, and contrast of flow and storage capacity of the flow units. Case studies of heavy oil watetrflood (one mature, one immature) showed that CRM can be used for waterflood analysis, and forecasting. In the immature flood with one injector and two producers and high permeability contrast, the most extreme variation of CRM parameters was observed. In the pattern flood where injected fluid was distributed relatively evenly among producers and breakthrough had already occurred, the CRM parameters tended to be constant over time. We showed that with frequent analysis (window approach) CRM can be efficiently used in heavy oil waterfloods,
Applications of Progressive-Recursive Self-Organizing Maps Algorithm in Guiding Reservoir History Matching
Authors: Al-Turki Ali A. , Al-Dossary Mubarak N. , Al-Ghamdi Amell A. , Al-Harbi Badr M. 
Published: October 2018

Abstract
Reservoir model history matching is a complex, time-consuming, and resource intensive process that needs to be carried out carefully for building reliable predictive tools to manage Oil & Gas assets. Reservoir models encompass detailed geological description representing subsurface heterogeneities that influence its dynamics. To intelligently manage and preserve the complexity of the reservoir models, an artificial intelligence, Progressive-Recursive Self-Organizing Maps (PR-SOM), algorithm was developed. PR-SOM is an unsupervised artificial intelligence neural network algorithm that classifies the reservoir grid cells into progressive reservoir parameters to identify similarly adjoining regions. The algorithm explores and identifies model geo-bodies with similarities and dissimilarities in a progressive and recursive manner. This allows history matching to be conducted on much smaller subsets of the reservoir model of similar geological features.
In this work, an artificial intelligence (AI) algorithm was applied, first, to guide the reservoir-wide history match processes. Next, the algorithm was applied to fine-tune well performance using information form well testing and historical data. The algorithm uses both static properties (permeability, rock quality indices, porosity, flow zonation … etc.) and dynamic properties (pressure or saturation) to construct similarities matrix. The results show that the clusters’s growth is progressive, controlled and quality assured by accounting for the controlling reservoir parameters. The number of mapped regions (clusters) is determined by optimizing the similarity matrix recursively. The quality of the global reservoir history match shows the effectiveness of the algorithm, better quality matching for historical production data, and fewer iterations (i.e. less simulation runs). The process is repeated to calibrate the reservoir model near wellbores by limiting the AI algorithm to only the drainage regions seen from well tests and historical data.
The results show that employed AI-guided history matching revealed similarities and dissimilarities in the reservoir model. That not only enhance field and well match, but also allowed us to maintain the heterogeneity contrasts inherited from the Earth model. The advanced algorithm was successfully used to assess the extent of geological heterogeneity and its impact on reservoir dynamics, to enhance history match quality, minimize human interaction, and to reduce computational requirements.
Extended Reach U-Shape Re-Entry Drilling in Shallow Depleted Fractured Reservoirs in Congo Offshore Oldest Oilfield
Authors: Tony Chembou Mike , Bruno Valeri , Loïs Crevoisier de , Michel Akue , Vincent Rodet , Gabriele Ghia , Achille Mouamba , Ali Lazzem 
Published: October 2018

Abstract
Congo has been an oil producing country since the 70's, it is in this context of aging oilfield and low oil price environment that a redevelopment project was launched to give a second life to a shallow, depleted, mature, offshore oilfield with viscous oil (22° API) in a cost-effective manner.
The solution selected was to drill "U-shape" side tracks (inclination at TD 115deg) from the original boreholes on an existing platform (60m WD). The objective was to create a second drainage area of up to 500m, ~200m away from the original producing zone. Five re-entries U-shape wells were delivered with measured to vertical depth ratios up to 2.5 in shallow heavily depleted reservoirs (270m TVD). The team selected innovative and low cost techniques to overcome many challenges, from high DLS in unconsolidated formations using simple mud motor BHA, to running 4-1/2" liner up to 115deg inclination and implementing a thixotropic mixed metal oxide mud system to mitigate losses.
The project has been successful both from a budget and production standpoint.
A Method for Improving the Evaluation of Elemental Concentration in Neutron-Induced Gamma-Ray Spectroscopy Logging
Authors: Liu Juntao , Liu Shucai , Yuan Chao , Zhang Feng , Yan Huizhong , Miao Bin , Li Hu 
Published: October 2018

Abstract
The determination of elemental concentrations, mineralogy and lithology is essential for the evaluation of unconventional plays. Several instruments utilizing D-T generator and gamma ray detectors have been developed to determine elemental weight fractions. The measured gamma ray energy spectrum can be approximated by a linear combination of the standard spectra of individual elements. Each geochemical well logging instrument has its unique set of elemental standards, which can be obtained by experimental approaches. The variations of the shapes of elemental standards are not considered under different conditions and it affects the accuracy of the elemental concentrations.
A decomposition of measured spectrum is carried out based on the elemental standard spectra to determine the relative elemental yields, which represent the contribution of gamma rays emitted by each element to the measured spectrum. Then the elemental yields can be converted to elemental weight fractions by using oxide closure model. The standard gamma ray spectra of individual elements are calculated by using Monte Carlo numerical simulation. The responses of standard spectra under different conditions such as different borehole sizes and drilling mud types, are simulated. The reasons for the change of the standard spectra shape are analyzed. A model based on gamma ray attenuation is introduced to compensate for the effects of logging conditions on the changes of standard spectra.
The simulation results show that variation of logging conditions have impacts on the shapes of the standard libraries. Therefore, if only one set of fixed standard spectra is utilized in processing measured spectra, the accuracy of elemental concentrations is affected. To address this problem, a model for compensating for the variations of the shapes of standard spectra is proposed. A field example of pulsed neutron spectroscopy logging is illustrated to validate the proposed method and results show that the agreement between computed elemental weight fractions and core analysis values is improved.
In the processing of geochemical logging data, changes in the shapes of the standard spectra were not considered. One set of fixed elemental standards are always utilized. In our study, a specific Monte Carlo simulation code is used to study the changes of elemental standards due to the variation of logging conditions and a method is proposed to improve the accuracy of elemental concentration measured by geochemical well logging.
Collapse and Bending Analysis of Slotted Liners by 3D FEM under Various Reservoir Conditions
Authors: Liu Xiaoda , Morita Nobuo 
Published: October 2018

Abstract
The goal of the research is to study the structural integrity and slot width change of slotted liners by 3D finite element analysis and experimental study. Slotted liners are widely used because of the abilities to ensure wellbore integrity and sand control. During installation and operations, the slotted liners have to be strong enough to hold axial loads and radial compression to prevent excessive buckling and deformation of slots. Experiments were designed to select the grades of materials, diameter/thickness of pipes, and slot pattern. Finite element models were developed to predict the integrity of slotted liners and acceptable slot width changes. The study considered slotted liner design and analyzed how much material grades, casing/tubing dimension and slot patterns affect the risk of slotted liner failure.
The Importance of Clean Off-Plane Perforations in All Phases of a Deepwater Well and Its Productivity Impact
Authors: Mahadev Karthik A.V. , Haldipur Prashant , Tinker Steven J. , Stewart Carlos , Roy Alistair M. 
Published: October 2018

Abstract
High permeability reservoirs in Deepwater Gulf of Mexico have been completed with fracpacks resulting in high production rate wells. The initial production rates for these wells range from 3 mbd to almost 40 mbd; and these rates can be sustained over extended periods of time (several years). Most of these developments in the Gulf of Mexico require sand control with cased hole fracpacks as the preferred completion technique. In addition to providing reliable sand control, fracpacks result in relatively low skin by bypassing near wellbore damage. Over the past few years, operators have focused on reducing skin and improving the production from these wells; leading to a more detailed analysis of fracpack performance. This paper will demonstrate that in high permeability reservoirs, production from the off-plane perforations is as important as production from the fracture. It examines the theoretical basis of the contribution of off-plane perforations to total flow and demonstrates the adverse effect on this contribution due to damage from drilling fluids and solids, cementing spacers and solids, fluid loss materials, perforating debris, wellbore debris, and crosslinked gel. Several case histories are analyzed to evaluate and quantify these effects and to show that the lower the conductivity contrast between the (high permeability) reservoir and the fracture, the higher the production benefit that can be realized by effectively cleaning the off-plane perforations.
Lessons Learned from In-well Fiber-optic DAS/DTS Deployment
Authors: Sanni Modiu , Hveding Frode , Kokal Sunil , Zefzafy Ibrahim 
Published: October 2018

Abstract
Fiber-optic sensing technology has gradually become one of the pervasive tools in the monitoring and surveillance toolkit for reservoir and production engineers. Traditionally, sensing with fiber optic technology in the form of distributed temperature sensing (DTS) or distributed acoustic sensing (DAS), and most recently distributed strain sensing (DSS) and distributed chemical sensing (DCS), were done with the fiber being permanently clamped either behind the casing or production tubing. Clamping the fiber behind tubing or casing is sometimes beleaguered with operational challenges that often lead to rendering the fiber partially damaged or inoperable. The emergence of the composite carbon-rod (CR) system that can be easily deployed in and out of a well, similarly to wireline logging, has made it possible to sense any well without prior fiber-optic installation.
In this paper, we present the lessons learned from the first well where we deployed in-well fiber-optic DAS/DTS. The DAS/DTS sensing was done in a few vertical oil producer wells and water injector wells without prior fiber-optic installation. The key objectives of the tests were to (1) investigate any well integrity across the entire length of each well, (2) assess production and injection flow profile across the perforations and behind casing, which hitherto was not possible with conventional production logging tool (PLT) tool, and (3) investigate the possibility of using the combination of distributed acoustic survey and distributed temperature survey for quantitative production flow analysis.
This paper reviews the complete design and implementation of the in-well fiber-optic deployment, field operational issues, analyses, and interpretation of the sensing results. The combination of DAS/DTS data showed no well integrity related issues. The sensing data surprisingly pinpointed a few geological features such as cooling shallow aquifers that hitherto had not been noticed. The combination of different pulse widths during shut-in and production/injection cycles helped to refine the resolution of the flow profile from the production and injection zones.
Post-Combustion CO2 WAG Pilot in a Mature Field: Model Calibration and Optimization
Authors: Olalotiti-Lawal Feyi , Onishi Tsubasa , Datta-Gupta Akhil , Fujita Yusuke , Watanabe Daiki , Hagiwara Kenji 
Published: October 2018

Abstract
We present a detailed history matching and process optimization of a CO2 WAG pilot at the West Ranch Field, Texas. The Petra Nova, a 50/50 joint venture between NRG and JX Nippon, operates a commercial scale post-combustion carbon capture facility at NRG's WA Parish generating station southwest of Houston. The industrially sourced CO2 is utilized for EOR in the West Ranch field, which is operated by Hilcorp Energy. A CO2 pilot was conducted to examine the potential for tertiary oil recovery by pattern-scale CO2 flooding and to better understand how pattern flooding will work in the fluvial geology of the reservoir. This paper discusses detailed modeling and history matching of the CO2 EOR pilot at the West Ranch field to understand the CO2 plume movement and optimize the flood design parameters.
For history matching the CO2 WAG pilot, we started by initializing the pilot sector model and imposing multiphase boundary fluxes generated from full-field compositional simulation. The pilot model calibration followed a hierarchical two-step approach. First, we performed a large-scale update of the model permeability distribution by integrating bottomhole pressure and multiphase production data. Next, streamline-based local updates were used to further calibrate the permeability field to match CO2 breakthrough times at the producers. Sensitivity studies were conducted using the calibrated pilot model to evaluate the effects of WAG ratio, CO2 Pore Volume Injected (PVI), number of WAG cycles and Voidage Replacement Ratio (VRR) on the oil recovery efficiency and CO2 utilization factor. Finally, we carried out a multiobjective optimization of the CO2 WAG process based on the influential operational parameters. With this strategy, multiple scenarios that consider the trade-off between the oil recovery efficiency and CO2 utilization factor were generated.
The history matched models capture the major trends observed in the producing Gas-Oil Ratio (GOR), oil production rate and CO2 mole fraction history at the wells. The updated models were independently validated in two ways. First, the models showed good agreement with reservoir saturation logs at two observation wells. Second, the models reproduced the CO2 recovery as a fraction of the injected CO2. These results imply that the history matched models are able to adequately capture the CO2 sweep profile in the pilot area. Sensitivity studies indicate CO2PVI and VRR (Voidage Replacement Ratio) as dominant parameters impacting oil recovery efficiency. The VRR and WAG ratio play a significant role in determining the CO2 utilization factor. A set of optimal operational parameters that utilize these decision variables was generated using a Design of Experiments (DOE) based multiobjective optimization workflow. This work presents, for the first time, modeling and optimization of a field-scale post-combustion CO2 WAG process.
Streamline Tracing and Applications in Naturally Fractured Reservoirs Using Embedded Discrete Fracture Models
Authors: Chen Hongquan , Onishi Tsubasa , Olalotiti-Lawal Feyisayo , Datta-Gupta Akhil 
Published: October 2018

Abstract
The streamline based technology has proven to be effective for various subsurface flow and transport modeling problems including reservoir simulation, model calibration and optimization. For naturally fractured systems, current streamline models are well suited for dual porosity single permeability systems because streamlines need to be traced only for the fracture system. However, complications arise for dual porosity dual permeability (DPDP) systems because streamlines need to be traced for both fracture and matrix systems. Also, the streamlines in the two systems may interact. We present a robust streamline tracing framework for use in the DPDP models via an embedded discrete fracture model (EDFM) framework.
The EDFM models utilize irregular gridding and non-neighbor connections to explicitly represent the discrete facture network. Our strategy is based on a boundary layer method that can be used to honor the fluxes at the matrix-fracture interface during streamline tracing. We generalize our previously proposed streamline tracing algorithms for local grid refinements (LGR) and faulted systems to discrete fracture network models where a fracture gridblock in EDFM is treated as a boundary layer for flux continuity and streamline tracing. The proposed method is benchmarked with a semi-analytical solution and a series of numerical examples encompassing different levels of geologic and geometrical complexity to illustrate the accuracy and robustness of the approach. Visualization of streamlines in complex fracture networks provide flow diagnostics such as sweep efficiency and connectivity of wells and fractures. The streamlines are then utilized to develop a workflow for rate allocation optimization for waterflood in naturally fractured reservoirs. We utilized a streamline-based gradient free algorithm whereby both injection and production rates are adjusted under realistic operational constraints. This approach only requires a few forward simulations and therefore offers significant advantages in terms of computational efficiency. It is confirmed that the optimized schedule provides improvements in oil recovery and sweep efficiency compared to the base scenario with uniform injection and production rates.
The uniqueness of this work is the robust streamline tracing algorithm in the EDFM using a novel boundary layer based approach for flux continuity. The proposed approach is simple and easy to implement and can be coupled with commercial simulators for field scale applications.
A Conceptual Structure to Evaluate Wells Producing Fractured Rocks of the Permian Basin
Authors: Raghavan Rajagopal , Chen Chih-Cheng 
Published: October 2018

Abstract
Pressure- and rate-time data at wells producing the Wolfcamp shale are evaluated by a model based on a framework using subdiffusive concepts. Quantitative measures to estimate heterogeneities in the fracture- and matrix-systems are provided. Multiple transfer mechanisms and complex structures govern the dynamic performance of the reservoir. Long-term depletion is governed by the matrix system; our evaluations indicate that excellent coverage is obtained in draining the lateral extents of the reservoir rock. As a physics-based model is used to evaluate responses, the suggested procedures are both extendable and scalable.
Compositional and Geomechanical Effects in Huff-n-Puff Gas Injection IOR in Tight Oil Reservoirs
Authors: Gala Deepen , Sharma Mukul 
Published: October 2018

Abstract
Lab experiments, field pilots and numerical modeling focusing on fluid flow aspects have indicated that gas injection in tight oil reservoirs is technically feasible. Several operators have conducted pilot tests in the Eagleford and Bakken shales for a Huff-n-Puff IOR strategy with mixed results. Our objective in this work was to study the impact of geomechanical effects, such as permeability changes and opening and closure of fractures during injection and production, on such huff-n-puff processes. We developed a fully coupled geomechanical compositional reservoir simulator to model Huff-n-Puff gas injection for improving liquid recovery in tight oil reservoirs. The simulator solves component mass balances, a suitable equation of state and pressure equations which are coupled with rock deformation and calculates stress changes due to both poroelastic (pressure changes) and mechanical (fracture opening and closing) effects. The phase behavior of the injected gas with a specified composition (which is different from the in-situ reservoir fluid) is accounted for using phase stability and flash calculation algorithms.
We present results from simulations using representative rock and fluid data from an unconventional reservoir and observe the following trends using our simulation studies: (a) Selection of the gas injection rate is very important in order to achieve a substantial pressure increase during the injection period. (b) Geomechanical effects, permeability decrease during increasing effective stress and permeability increase during decreasing effective stress has a significant impact on overall oil recovery. (c) Huff-n-Puff IOR will be more successful in certain reservoirs than in others depending on the composition of the reservoir fluid, saturation pressure, producing GOR and geomechanical reservoir rock properties. Our simulation results provide operators with significant new insights on the design of gas injection IOR processes. It is shown that geomechanical effects during huff-n-puff cycles have a significant impact on oil recovery, particularly if natural fractures and planes of weakness are present. Specifically, several design questions can be answered such as (a) gas injection rates and volumes (b) impact of injection fluid and reservoir fluid composition (c) selection of candidate reservoirs (d) impact of operating bottomhole temperature and pressure.