bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture Finite Difference Seismic Modelling
Authors: Ferla Maurizio , D'Agosto Claudio 
Published: May 2016

Abstract
The objective of this study is to measure the seismic response of fluid filled fractures, trying to evaluate which acquisition survey parameters can better highlight this feature. The scope of fracture modelling is simulating the presence of a fracture system in the area of interest verifying if it is detectable and describable by a 3D P-wave or PS-wave seismic data, for issues related to operative aspects but also for future support to the drilling activity.
A system of aligned fractures can be described as an effective anisotropic medium when the dominant wavelength is long compared to the fracture scales. In order to model the behavior of seismic waves in fractured media, we can characterize the model with normal and tangential crack compliances, Coates and Schoenberg (1995). The main measurable effects on seismic data are the shear wave splitting and p-wave AVOaz anomalies. Shear-wave splitting due to the alignment of vertical cracks can be recognized by the polarization of the fast split shear-wave, which is usually parallel to the local strike of cracks and can be used to characterize fracture orientation. The time delay between fast and slow shear-waves is closely related to the intensity of crack-inducedanisotropy in the medium (proportional to the fracture density).
The main question to answer is if a 3D multicomponent survey can detect the travel time shift between parallel and perpendicular directions generated by the investigated formation. The second subject is to investigate the potentiality of fluid discrimination with PS waves but also PP waves. Modeled data is generated using elastic anisotropic finite difference code. The analogies between cracks systems and anisotropic media have been analyzed in order to infer interesting considerations about fractures characterization. The anisotropic parameters and the geophysical model have been assumed on the basis of in place data measurements.
The obtained results demonstrated the correlation between the seismic features and the fracture characteristics, such as crack density, fractures orientation, fluid content and AVO anomalies.
Modeling of Spent-Acid Blockage Damage in Stimulated Gas Wells
Authors: Zhang Q. , Zhu D. , Hill A.D. 
Published: May 2016

Abstract
Aqueous fluids introduced by different stimulation treatments cause water blockage in the near-wellbore region of wells. This water blockage acts the same as formation damage when the well is put back on production. One of the examples is when gas wells in carbonate reservoirs are acid-stimulated; the wormholes that propagate into the formations might be surrounded by a region of high water saturation created by the leak off of spent acid. The spent-acid blockage damage could be severe, especially in lower permeability regions where capillary forces are relatively high. This paper presents a model that investigates the spent-acid damage in wormhole region of acid-stimulated gas wells.
The phenomenon of spent-acid blockage was first investigated in the experimental study to identify the problem. A lab-scaled model was then developed to characterize the capillary pressure and relative permeability behavior by matching the results from the model to the experimental observation. We then extended the study to field-scale by approximating the wormhole as a long, slender half-ellipsoid centered in an ellipsoidal flow field. The simulations that focused on the displacement regime of spent acid recovery process were developed. These models were solved numerically to predict pressure behavior and spent acid distributions for the flow-back process.
With the models, we studied the effects of several key factors, such as capillary pressure, relative permeability, and addition of additives, on the efficiency of spent acid recovery. The results show that common additives routinely added to acid systems may aid, or hinder, spent acid recovery, depending primarily on their effects on rock wettability. With the studies performed on the model developed, we provide recommendations for minimizing spent acid damage to gas well productivity.
Anisotropic Waveform Inversion with Well Constraints
Authors: Wang Chao , Yingst David , Leveille Jacques , Bloor Robert 
Published: May 2016

Abstract
The term, "Waveform inversion" (WFI), refers to a collection of techniques that use the information from seismic data to derive high-fidelity earth models for seismic imaging. The attractiveness of WFI lies mainly in its lack of approximations, at least in a theoretical sense, in contrast to other model determination techniques such as semblance or tomography. However, a whole raft of approximations must be made to make the technique viable with today'scomputing technology and restrictions of seismic acquisition. These are collectively referred to as "waveform inversion strategies" and in this paper we mainly discuss regularization and preconditioning strategies. Because the wavefields need to be accurately modeled to represent the kinematics of all the waves during WFI iterations, the effects of anisotropy often help to improve WFI results. In this paper, forward modeling and its adjoint computation are based on acoustic wave equations in vertical transversely isotropic (VTI)media. We introduce a multi-parameter inversion for P-wave velocity and anisotropy parameters. WFI is a highly nonlinear, ill-posed problem. We introduce additional information and turn the unconstrained optimization problem into a constrained optimization problem in order to reduce the ill-posedness. The geophysics of the problem leads to appropriate constraints, such as restriction of model parameters, or information from well logs. In this paper, we use well logs as constraints and solve the problem using the augmented Lagrangian method (ALM), a mathematical method that replaces a constrained optimization problem by a series of unconstrained problems. The ALM with well constraints aims at preserving velocity characteristics from welllogs and providing us with more reliable velocity updates. This paper presents the acoustic anisotropic WFI implementation using ALM with well constraints. It also discusses practical strategies for regularization and preconditioning and their influences on the models that are obtained from WFI. We illustrate these approaches on a 2D synthetic Marmousi example and another application to 3D VSOOBC data from the Green Canyon area of the Gulf of Mexico. From the results, we show that multi-parameter VTI WFI with ALM provides us with more useful and reliable model updates. To further evaluate our WFI results, we also compare offset gathers and RTM images and illustrate their significant improvement susing updated models generated from WFI.
Utilizing Distributed Temperature Sensor Data in Predicting Flow Rates in Multilateral Wells
Authors: Almulla J.M. , Yang C. , Zhu D. 
Published: May 2016

Abstract
The new advancements in well monitoring tools have increased the amount of data that could be retrieved with great accuracy. The new challenge that we are facing today is to maximize the benefits of the large amount of data provided by these tools. One of these benefits is to utilize the continuous stream of data to determine the flow rate in real time of a multilateral well. Temperature and pressure changes are harder to predict in horizontal laterals compared with vertical wells because of the lack of variation in elevation and geothermal gradient. Thus the need of accurate and high precision gauges becomes critical. A theoretical model is developed to predict temperature and pressure in trilateral wells. The model is used as a forward engine in the study and an inversion procedure is then added to interpret the data to flow profiles. The forward model starts from a specified reservoir with a defined well structure. Pressure, temperature and flow rate in the well system are calculated in the mother bore (main hole) and in the laterals. Then we use the inverse model to interpret the flow rate profiles from the temperature and pressure data measured by the downhole sensors. A gradient-based inversion algorithm is used in this work, which is fast and applicable for real-time monitoring of production performance. In the inverse model, the flow profile is calculated until the one that matches the temperature and pressure in the well is identified. The production distribution from each lateral is determined based on this approach.
Examples are presented in the paper. The value of the model approach for production optimization for trilateral wells is illustrated through parametric study.
Integrated Reservoir Management Utilising a Portfolio Approach to Beat the Impact of Delayed Water Injection Projects - Opportunistic Strategic Alignment in North Kuwait
Authors: Chetri H.B. , Al-Ajmi Hussain 
Published: May 2016

Abstract
North Kuwait is blessed with multiple reservoirs stacked, Tuba at the shallowest and Ratawi at the deepest level. Water flood expansion was the key ingredient to provide the short term production assurance for the Asset. Field development activities have been progressing for two of the major stacked reservoirs withlion's share of incremental production (Mauddud & Upper Burgan), assuming that these reservoirs will get the benefit of water injection, to cope up with the enhanced level of production. Unfortunately, the water injection projects have been delayed till the end of 2013, leading to rapid decline in reservoir pressures and erosion in the well performance of the producers (naturally flowing as well as on artificial lift).
A comprehensive review of the portfolio of all reservoirs was made vis-à-vis the drilling/work over activities. Complete history of pressure-production data for last 40years was analyzed using OFM. The output from the reservoir simulation models was analyzed & discussed with multi-disciplinary teams. Aggressive surveillance & data integration plan was made and implemented to identify the focus areas, from where "new" production can be accelerated and / or controlled, adhering to the best reservoir management practice. Isochronal reservoir pressure maps were updated with full fieldstatic bottom hole pressure surveys. Detailed analysis of the RFT/ PLT data was performed to optimize the perforations at layers with high reservoir pressure. New wells from shallower reservoirs were deepened to the reservoirs enjoying the active water drive and accordingly, completed for short term production till the water injection expansion project is commissioned. Integrated reservoir management approach was followed throughout the gamut of field development activities with multi-skill expertize reviewing as peers for smart decisions.
The paper's objective is to share the integrated Reservoir management approach to beat the impact of delayed water injection projects on overall production portfolio, without compromising the technical requirement of voidage replacement ratio for depletion drive reservoirs with best practices approach.
Application of Low Pressure System at Balingian, Sarawak Brownfield; Candidate Selection and BY Field Case Study
Authors: Ismail M Syahezat , Hamza Norashikin 
Published: May 2016

Abstract
Bayan (BY) is a brown field located in Sarawak region with over 25 years of production. Declining trend in field production resulting from rapidly declining reservoir pressure and increasing water production has prompted aggressive production enhancement activities to arrest further decline. Conventional gas lift method has been widely applied across the field and has provided reliable means of artificial lift to sustain production. However, wells with very low reservoir pressure were not able to sustain production even with gas lift due to the back pressure experienced in the production system.
Low Pressure System (LPS) were implemented in two (2) out of four (4) drilling platforms in BY to sustain and increase the field production, reactivate idle wells and to manage the back pressure for the whole production system. Experience gathered from this implementation enable us to improve the candidate selection process and to share potential limitation imposed by the LPS system to operation.
Actual BY LPS performance is shown here to illustrate the proven success in increasing the field production and unlocking some of BY reserves. The change in the production trend of well's producing in current production system and after being tied to LPS will show the total achieved production gain which in BY case amounted to more than 1.5 million barrels in 4 years of operation.
Fundamental Approaches to Dolomitisation and Carbonate Diagenesis in Different Hydrogeological Systems and the Impact on Reservoir Quality Distribution
Authors: Xiao Yitian , Jones Gareth D. , Whitaker Fiona  F. , B Al-Helal Anwar , Stafford Sherry , Gomez-Rivas Enrique , Guidry Sean 
Published: May 2016

Abstract
The accurate prediction of the geometry of subsurface dolomite geobodies, their connectivity, and the distribution of reservoir properties is a fundamental challenge in carbonate reservoir characterization. Reactive Transport Models (RTM) couple geochemical reactions with fluid flow to facilitate both 2D and 3D quantitative, process-based investigations of dolomitization and related carbonate diagenetic reactions. The paper will highlight new results and key conclusions from simulations of dolomitization mechanisms in four different hydro-geological systems:Brine reflux,Mixing zone and sub mixing zone,Geothermal circulation andFault controlled hydrothermal circulation.
Simulations provide new insights on the spatial distribution and dynamic behavior of:Geometry and distribution of dolomite bodies generated by different styles of subsurface fluid flow and their dynamic interactions;Regional versus local controls on dolomite occurrence and connectivity;Sensitivity and hierarchy of geological controlling parameters;Spatial and temporal relationships between dolomitization and associated diagenetic minerals including anhydrite cements and Mississippi Valley Type(MVT) mineralization;Effect of hydrothermal fluid induced dolomite recrystallization and anhydrite dissolution;Criteria to help identify the distribution of reservoir quality including high permeability dolomite "sweet spots".
When integrated with conventional subsurface data and stratigraphic, geochemical, and structural framework, Reactive Transport Models of dolomitization provide fundamental and robust predictive concepts and reservoir quality models for exploration and new / mature field developments. In particular, the state-of-the-art simulations allow the analysis and 3Dvisualization of dolomite body spatial and temporal evolution that can translate into alternative "process-based" well correlation methods and strategies for populating diagenetic bodies and their petrophysical properties in geological models for reservoir flow simulations.
Successful Implementation of Fiber-Laden Fluid for Hydraulic Fracturing of Jurassic Formations in Western Siberia
Authors: Kayumov Rifat , Borisenko Alexey , Levanyuk Olesya , Savelyeva Irina , Emelyanov Sergey 
Published: May 2016

Abstract
The Urnenskoe field is located in the Tyumen region, Western Siberia. The main production target is the J1 formation belonging to the upper Jurassic Vasyugansk suite. Subsurface geology of the Urnenskoe field features the lithological heterogeneity of the J1 formation with high- and low-permeability interlayers and considerable petroleum reserves in upper low-permeability formation intervals. Oil and water have highly different viscosities permitting rapid water breakthrough into the formation.
The first hydraulic fracturing operations were carried out at the Urnenskoe field in 2010. Because there are rich oil saturated zones in the low-permeability upper zone of the reservoir, the properties of the fracturing fluid to transport proppant and its ability to prevent settling during both the pumping and when the fracture is closing are decisive for the well productivity after the fracturing operation. Fracturing fluid with degradable fibers was selected to achieve these properties during hydraulic fracturing. The fibers create a reinforcing net within the fracturing fluid with proppant and mechanically assist the transportation and suspension of the proppant grains. The temperature decomposes the fibers when the fracture is closed. In addition, the fibers allow lowering the polymer concentration in the fracturing fluid, thus enabling control of the fracture vertical growth and decreasing proppant pack damage.
Since there are no all-season roads and it is difficult to approach the Urnenskoe field in the summer, there was no fracturing fleet capable of performing an operation utilizing the fluid with degradable fibers in July 2011. Therefore, 7 conventional fracturing operations were performed; these can be used to compare the effectiveness of conventional fracturing with another 23 operations in which the fibers were used. These operations revealed that the wells in which the fibers were used had a dimensionless productivity index that was 33% higher, and this effect remained stable. Also, for the wells with the fiber application, the average cumulative oil production for 5 months was 2,245tons higher (recalculated for one well). These results confirm the effectiveness of hydraulic fracturing with degradable fibers in the Urnenskoe field. The successful experience of using hydraulic fracturing with degradable fibers at the Urnenskoe field, laboratory tests of the fiber-laden fluid, analysis of well productivity, and particular applications of the technology provide information to guide further optimization. In addition, the technology has been applied in the Jurassic formations of the neighboring Ust-Tegusskoe field, where a considerable productivity gain was achieved compared with the conventional fracturing operations.
Dual Function Reverse Demulsifier and Demulsifier for the Improvement of Polymer Flooding Produced Water Treatment
Authors: Wu Di , Meng Xiangchun , Zhao Fengling , Lin Sen , Jiang Neng , Zhang Shaohui , Qiao Liyan , Song Hui 
Published: May 2016

Abstract
Adding partially hydrolyzed polyacrylamide (HPAM) to flood water for enhanced oil recovery has resulted in some difficulties for treatment and re-injection of produced water at Daqing Oilfield of China: Production of the injected HPAM increased water phase viscosity and emulsification of the produced fluid, leading to more oil carry-over; The state-of-art cationic water clarifiers showed poor compatibility with HPAM containing produced water due to formation of very sticky oily flocs which seriously pollutes bed filters and slop oil recovered in produced water treatment. Throughputs of existent produced water treatment facilities had to be lowered by up to 50% so that the HPAM containing produced water might be treated to re-injection specifications. As an alternative for the state-of-art cationic water clarifier, a nonionic reverse demulsifier and demulsifier consisting of both water soluble and oil soluble active components respectively for water clarification and water-in-oil emulsion breaking, was developed as a water dispersible micro-emulsion mixture. Injected into high water-cut o/w produced fluid prior to the initial oil/water separation, the dual function chemical greatly enhanced flocculation and coalescence of the oil droplets in the reverse crude oil emulsion while maintaining adequate emulsion breaking capability for downstream crude oil dehydration, leading to less oil carry-over and looser emulsion in the influent water of produced water treatment facilities. In one field application, injected at a dosage of 15mg/L into the polymer flooding produced reverse crude oil emulsion upstream of oil/water separation, the dual function chemical reduced the oil content in the influent water of a produced water treatment facility from 2004mg/L to 443mg/L, and lowered the oil content in the effluent water of bed filters from 31mg/L to 4.1mg/L without application of water clarifiers.
Classification and Evaluation of Ultra-Low Permeability Reservoirs in the Changqing Oilfield
Authors: Ran Xinquan , Li Anqi , Zhao Jiyong , Li Shuheng 
Published: May 2016

Abstract
With the rapid development of the world economy, the exploration and development of unconventional oil and gas resources have become a new hot spot. As an important subset of unconventional reservoirs, ultra-low permeability(ULP) reservoirs have been greatly concerned. Studies suggest that the ultra-low permeability reservoir belongs to the typical tight reservoir. The current low-permeability reservoir classification criteria available in the literature cannot meet the actual needs of ultra-low permeability reservoir development. Through researches, reservoir characterization parameters of effective porosity, mainstream throat radius, movable fluid saturation and starting pressure gradient are screened out to build quaternary classification coefficient. A new standard of classification and evaluation of ultra-low permeability reservoirs is established, and ultra-low permeability reservoirs are divided into three categories. Thus it provides a theoretical basis for speeding up the effective development of ultra-low permeability reservoirs.
Since the beginning of the 21st century, the world economy has entered a new cycle of development. The demand for oil and gas resources in the countries soared. Facing the huge demand for energy, productivity construction and production rate are relatively insufficient throughout the world. Unconventional oil and gas resources are beginning to receive more attention. Ultra-low permeability reservoirs, as important unconventional oil and gas reservoirs, have huge potential for exploration and development, but the current classification of reservoir evaluation criteria cannot meet the needs of ultra-low permeability reservoir exploration and development. In order to effectively guide the exploration and development practice of ultra-low permeability reservoirs, it is of great significance to launch researches on ultra-low permeability reservoir characterization parameter system, and to establish a new classification and evaluation criteria.