bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-scale Gas Transport in Shales with Local Kerogen Heterogeneities
Authors: Akkutlu I. Yucel , Fathi Ebrahim 
Published: October 2011

Abstract
Based on micro and meso-scale investigations, a new mathematical formulation is introduced in detail to investigate multiscale gas transport phenomena in organic-rich shale core plugs. The formulation includes dual porosity continua, where shale permeability is associated with inorganic matrix having relatively large irregularly-shaped pores and fractures, whereas molecular phenomena (diffusion and nonlinear sorption) are with the kerogen pores. Kerogen is considered as a nanoporous organic material finely-dispersed within the inorganic matrix. The formulation is used to model and history-match gas permeation measurements in the laboratory using shale core plugs. The results indicate significance of molecular transport and strong transient effects due to gas/solid interactions within the kerogen. In the second part of the paper, we present a novel multi-scale perturbation approach to quantify the overall impact of local porosity fluctuations associated with a spatially nonuniform kerogen distribution on the adsorption and transport in shale gas reservoirs. Adopting weak-noise and mean-field approximation, the approach applies a stochastic upscaling technique to the mathematical formulation developed earlier for the laboratory. It allows us to investigate local kerogen heterogeneity effects in spectral (Fourier-Laplace) domain and to obtain an upscaled "macroscopic" model, which consists of the local heterogeneity effects in real time-space domain. The new upscaled formulation is compared with the previous homogeneous case numerically using finite-difference approximations to initial/boundary value problems simulating the matrix gas release. We show that macro-transport and macro-kinetics effects of kerogen heterogeneity are nontrivial and impact cumulative gas recovery. The work is important and timely for development of new-generation shale gas reservoir flow simulators and it can be used in the laboratory for organic-rich gas shale characterization.
Using Industrial Remotely Operated Vehicles in Stand-by Time for Deep-water Biodiversity Assessment: A Case Study From Offshore Nigeria
Authors: Jones Daniel , Mrabure Charles , Gates Andrew 
Published: October 2011

Abstract
Description
There is very limited information available on the deep water biodiversity offshore Nigeria. Detailed information on seabed communities is vital for effective environmental management of offshore drilling disturbance but collection of environmental data usually require a dedicated research vessel and associated high costs. We present an approach to environmental survey that uses remotely operated vehicles (ROVs), already in place on survey/supply boats, during stand-by time in drilling operations for low-cost and high-quality operations.
Application
Spatially-referenced ROV video surveys were performed following a stratified random design. These, combined with targeted ROV sample collections (of biological specimens, sediment and rock), enabled an accurate quantitative census of biological patterns. Oceanographic data were collected with self-contained data-logging conductivity, temperature and depth sensors attached to the ROV.
Results, Observations, and Conclusions
ROV survey showed that the seabed environment offshore Nigeria (750-1350m water depth) was extremely diverse, containing several habitats from sedimentary plains to steep rocky slopes. The visible seabed fauna were generally abundant (0.3 animals m-2) and diverse (&gt;69 species). Faunal communities varied in density and composition across the habitat and depth range. Many species were previously described; however, surveys revealed several potential new species and ROV traps captured a confirmed new species of amphipod crustacean. Sediment samples collected provide valuable pre-drilling baseline data, which will allow assessment of the extent and magnitude of future environmental disturbance from operations. Temporally replicated temperature and salinity depth profiles captured the thermocline's seasonal movement in much greater detail than previous observations.
Significance of Subject Matter
The significance of this biodiversity assessment includes:
Data collected provided a suite of high-resolution baseline measurements which are invaluable for future impact assessment. Use of ROVs during stand-by time enabled rapid low cost data collection. Approach facilitates initial environmental evaluation and longer-term monitoring of hydrocarbon exploration and production areas. Results increase the knowledge of the environmental conditions of deepwater offshore Nigeria and indeed West Africa. This survey provided important information on offshore biodiversity to the Nigerian Regulatory Authorities (Federal Ministry of Environment and Department of Petroleum Resources) thus enhanced regulatory support for the drilling project.
An Alternative to Streamlines for Flow Diagnostics on Structured and Unstructured Grids
Authors: Shahvali M. , Mallison B. , Wei K. , Gross H. 
Published: October 2011

Abstract
Streamline-based methods can be used as effective post-processing tools for assessing flow patterns and well allocation factors in reservoir simulation. This type of diagnostic information can be useful for a number of applications including visualization, model ranking, upscaling validation and optimization of well placement or injection allocation. In this paper, we investigate finite volume methods as an alternative to streamlines for obtaining flow diagnostic information. Given a computed flux field, we solve the stationary transport equations for tracer and time of flight using either single-point upstream weighting or a truly multi-dimensional upstream weighting scheme. We use tracer solutions to partition the reservoir into volumes associated with injector-producer pairs and to calculate fluxes (well allocation factors) associated with each volume. The heterogeneity of the reservoir is assessed by using time of flight to construct flow capacity-storage capacity (F-Φ) diagrams which can be used to estimate sweep efficiency. We compare the results of our approach with streamline-based calculations for several numerical examples and we demonstrate that finite volume methods are a viable alternative. The primary advantages of finite volume methods are applicability to unstructured grids and ease of implementation for general purpose simulation formulations. The main disadvantage is numerical diffusion, but we show that a multidimensional upstream weighting scheme is able to reduce these errors.
How to Constantly Deliver 100% Packing Efficiency in Openhole Gravel Packs: A Field Study in Colombia
Authors: Trujillo Hernando , Tengono Jose Aldemar , Rubiano John , Castaño Ricardo , Beltran Alexander , Ortiz Everardo , Navarro Claudia , Florez Darwin , Lopez Nicolas 
Published: October 2011

Abstract
Although the application of openhole gravel packs has been well documented, only a few cases using this type of completion in openhole intervals greater than 800 ft in length have been implemented in Latin American land wells. Recent field studies involving openhole gravel packs in long intervals were carried out in the Ocelote field in the Llanos basin of Colombia. The operating company of the field is Hocol S.A., (subsidiary of Ecopetrol) and after many trials and the use of various service providers and tools, the final customized methodology and equipment of one particular service company were selected and implemented for the openhole completion campaign of the entire field.
The wells completed previously in this field were thoroughly analyzed. Because of operational and design issues, pack efficiency in one well was greater than 90%; however, in all of the other wells, only 50% pack efficiency was achieved. This analysis covers the reason why pack efficiency was consistently low in the first three wells, steps taken to correct them, and new service company to guarantee 100% pack efficiency in the subsequent openhole gravel packs, and the new tool designs implemented to solve the existing issues that guaranteed the successful gravel-pack operation in the remaining wells in the campaign. The step-by-step methodology chosen and implemented in the design of each job are presented, including the type and gravel pack material and selection of the correct gravel-pack tools to mitigate potential problems and the selection of the appropriate screens impacting the final outcome.
Finally, data from the subsequent wells that were gravel packed using the new methodology are presented, including the tools used and the technology used to consistently achieve 100% pack efficiency in all of the remaining wells in the field. Conclusions are presented, in addition to individual well performance comparisons.
Experiments and Model Assessment on High-Viscosity Oil/Water Inclined Pipe Flows
Authors: Sridhar Siddesh , Zhang Hong-Quan , Sarica Cem , Pereyra Eduardo 
Published: October 2011

Abstract
An experimental study has been conducted to investigate high-viscosity oil/water flow in inclined pipes. The pipe inside diameter (ID) is 50.8 mm and pipe inclination angles are −2°, 0°, 5° and 10° from horizontal. The fluids are a mineral oil with a viscosity range of 0.2 – 1.1 Pas corresponding to temperatures 60 –100 °F and filtered tap water. Tulsa city natural gas was used to pressurize the facility to 250 (+20) psig. Superficial oil velocity ranged from 0.1 to 1 m/s and superficial water velocity ranged from 0.1 to 0.5 m/s. Experimental measurements obtained are pressure gradient and water holdup. Pipe viscometer was used to obtain live oil viscosity measurements. Flow patterns were observed through a sapphire window and recorded with a high speed video system. The experimental measurements and observations are used to compare with mechanistic model predictions to identify the deficiencies in the models.
3D Multiphase Streamline-Based Method for Interpretation of Formation-Tester Measurements Acquired in Vertical and Deviated Wells
Authors: Hadibeik Hamid , Pour Rohollah A. , Torres-Verdín Carlos , Sepehrnoori Kamy , Shabro Vahid 
Published: October 2011

Abstract
Complex heterogeneous reservoirs penetrated by deviated wells pose significant challenges when modeling and interpreting packer- and probe-type formation-tester measurements. This paper introduces a streamline-based method specifically designed for near-wellbore fluid-flow modeling in vertical and deviated wells. The primary application of the method is for efficient simulation and automatic history matching of formation-tester measurements in the presence of invasion and variable petrophysical and geometrical properties. Based on the spatial distribution of pressure calculated with a previously validated near-wellbore finite-difference model (FDM), the method traces streamlines from the reservoir into fluid sampling probes. The calculated spatial distribution of pressure is input to the streamline-based method to propagate the spatial distribution of water saturation. Subsequently, the calculated spatial distribution of water saturation is input to the FDM to update the spatial distribution of pressure. Streamlines are then recalculated and this repeated pressure-saturation procedure continues until reaching the desired final simulation time.
The combined FDM and streamline-based method utilize full-tensor permeability to couple wellbore-reservoir systems during fluid sampling in horizontal and deviated wells. It is shown that the spatial rendering of streamlines permits rapid assessment of the time evolution of fluid saturation near the sampling probe. We successfully test the streamline-based method in the dynamic simulation of fluid contamination into conventional and focused-type probes operating in vertical, horizontal, and deviated wells for the case of multiphase, immiscible fluid-flow in heterogeneous formations. The method implements successive streamline and FDM time steps adaptively to decrease computational time by a factor of four while achieving less than 5% relative difference in the simulation of fluid production measurements when compared to FDM results.
For formation testing in deviated wells, the streamline-based method permits more rapid appraisal of anisotropy, bedboundary, and complex geometrical effects on fluid-sampling times than conventional 3D fluid-flow simulators. It also quantifies the sensitivity of measurements to variations of permeability, invaded zones, anisotropy, and well deviation. Our simulations indicate that fluid sampling in deviated wells subject to mud-filtrate contamination requires adequate positioning of the probe around the perimeter of the wellbore to secure the fasted cleanup possible.
Integration of Dynamic Modeling of ICD Completion Design and Well Placement Technology: A Case Study of GOM Shelf Reservoir
Authors: Sharma A. , Kok J. C. , Neuschaefer R. , Han S. Y. , Bieltz T. , Obvintsev A. , Riegler P. 
Published: October 2011

Abstract
High water production is a major issue in horizontal oil wells, especially in longer laterals, because of the high drawdown from the heel to toe. In addition, the presence of heterogeneity along the lateral section can lead to uneven sweep of hydrocarbons which can result in poor recovery. To control the water production and achieve better sweep efficiency, ICDs have been introduced which balance fluid flux along the producing horizontal well.
This paper discusses the feasibility and results of using integrated technologies such as ICDs along with rotary steerable drilling systems (RSS) and azimuthal logging while drilling well placement technology to achieve higher reservoir sweep efficiency. This case study is focused on a Gulf of Mexico (GoM) shelf horizontal well which was completed with prepacked screens. The well was sanded in and plugged after five years of high water production. A saturation log was run in the offset well which granted the viability to revisit this reservoir. Consequently, a new offset horizontal well was proposed and drilled next to the existing well to sweep out remaining reserves.
For the new offset well, full field dynamic simulations were performed to evaluate attic placement methodology and optimization of Inflow Control Devices (ICDs) into the integrated design. The results illustrate that attic horizontal well placement is feasible using integrated drilling with ICD technology to maximize the sweep efficiency.
Understanding and Handling Residual Risks
Authors: Zhao J. 
Published: October 2011

Abstract
Risk management and risk analysis techniques have been widely discussed and utilized in many energy firms. They are pro-active tools giving decision-makers forewarnings and scientific predictions. However, a less well known concept in the arena of risk management is worth elaborating. Residual risk, a terminology not common to most people in our industry, is rarely mentioned and discussed in the literature; it still remains a poorly understood notion. It often is confused with the Secondary Risk, and easily mistaken for missed risks in risk identification process. Depicted as" leftovers", residual risks are often neglected in risk management process as many regard such risks are well covered under ALARP (as low as reasonably possible). Moreover, residual risks are often deliberately eliminated from stochastic modelling process as many risk analysts reckon that extreme cases, beyond" normal" 80% confidence range, are not worth considering. In reality when unpleasant events occur the real culprit is more often than not either rare event driven risk or residual risk that caught people off guard.
The treatment of residual risks requires both diligent prudence and well thought-through risk taking. Failure Model Effect Analysis (FMEA) is often deployed to assess the severity of such risks, hence helping management better understand the devastation in case they occur." Normally ranged" risks would often be handled by scientific manner and decisions are relatively easy, however, there isn't a clear path to handle residual risks, as it is not a pure mathematical exercise but demands strong incorporation of psychological judgement as well. The paper challenges decision makers to appreciate true implications of residual risks, and what they are about to bring to their businesses. The author, through the illustration of examples, proposes a residual risk handling process that combines qualitative risk assessment, psychology of risk taking and Monte Carlo simulation techniques. The process mainly applies to early phase project development and business case fruition process where large uncertainties may easily affect decision-makers, but it is also applicable to project execution phase.
Key words: Residual Risk, Risk-taking, Psychology
Review of a Stratigraphic Reservoir Exploration Proven by Production: A Case Study
Authors: Ling Yun , Guo Xiangyu , Gao Jun , Sun Desheng , Lin Jixiang 
Published: October 2011

Abstract
The limitation of conventional seismic resolution (such as 1/4 wavelength) made thin bed reservoir exploration a difficult task. But with recent developments in oil and gas exploration, thin bed reservoirs are now becoming a common topic, especially in predicting the remaining oil in mature oilfields. For successful thin bed reservoir exploration, it is very important to overcome the conventional resolution limitations. In 2003, we began research on a thin bed lithologic reservoir in the Tarim basin, Northwest China. Based on the relative reservoir information preserved processing result and with the application of relative spatial resolution concepts based on isochronous geologic interfaces, prediction of a thin bed lithologic trap and oil-water contact was made. Production of this reservoir has since proven the prediction.
Incremental Recoveries in the Field of Large Scale High Viscous-Elastic Fluid Flooding are Double that of Conventional Polymer Flooding
Authors: Demin Wang , Gang Wang , Huifen Xia , Shuren Yang , Wenxiang Wu 
Published: October 2011

Abstract
By conventional mechanism, polymer flooding decreases the Mobility Ratio and increases the Sweep Efficiency and Recovery of the reservoir, but does not increase the Displacement Efficiency (ED).
However, from new understanding of the mechanism that driving fluid elasticity can increase the ED, Daqing Oil Field started 2 field pilot tests of high elasticity fluid flooding in year 2002, the actual recoveries are all more than 21%OOIP above that of water flooding, with incremental recoveries about double that of conventional polymer flooding (viscosity at 40~60 cp). Due to the very good results, in the recent 3 years, Daqing has rapidly expanded high viscous-elastic fluid flooding to more than 5000 wells. From the results of 1000 wells that have used this EOR method for a sufficient time to predict the results from field data, all will attain an incremental recovery of more than 20%OOIP; the other wells, according to numerical simulation, are performing as expected.
Some new knowledge on the mechanism of viscous-elasticity of the driving fluid mobilizing residual oil is also presented.
Field experience shows the difficulties in solving the problems of producing, pumping, gathering and treating produced fluid from high viscous-elastic floods are about the same as that of conventional polymer floods and much easier to solve than alkaline-surfactant-polymer (ASP) floods.
The field results also show that the economics (costs per ton of produce oil) of this EOR method is about the same as conventional polymer flooding.
In Daqing, very large scale high elasticity flooding is taking the place of conventional polymer flooding and ASP flooding to further increase the field recovery from 42% OOIP for water flooding to above 60%OOIP for high elastic fluid flooding. More than 2000 wells are converted to this method per year.
This is a very promising new EOR method that could be used by itself or in conjunction with other Chemical EOR methods to significantly increase the recovery of many types of oil-fields.
Considerations for Field Implementation of Microbial Enhanced Oil Recovery
Authors: Jackson Scott C. , Fisher John , Alsop Albert , Fallon Robert 
Published: October 2011

Abstract
For the last 6 years DuPont with different partners has done extensive fundamental research into the application of Microbial Enhanced Oil Recovery technology (MEOR).
We have demonstrated two mechanisms that have shown in the lab, more than a 10% increase in the recovery factor.
Increased sweep efficiency by plugging of high permeable zones thereby forcing water to produce oil from previously unswept parts of the reservoir. Reduced oil / rock surface tension resulting in lower residual oil saturation.
This paper describes the key laboratory tests and preliminary field data used to evaluate these two mechanisms.
Our approach has been to inoculate the reservoir with a microbe that under the optimal nutrient conditions will expressed the needed function -- bioplugging or reduced oil saturation. The microbe and the nutrients are tailored to the conditions of each reservoir thus giving MEOR the greatest chance for success. This paper presents challenges that were raised as a result of extensive lab work that are relevant to the implementation of MEOR on a field level.
Our ongoing research has provided many insights into the appropriate application of microbial EOR. The unique aspects of each production area, the nature of the oil, the water, the formation matrix, and the background microbial population and their complex interactions must all be assessed when considering the potential application of microbial EOR. The amount of work described for assessing potential MEOR mechanisms is extensive. However, this process has been streamlined and we have been able to assess new target reservoirs for potential MEOR treatments in about 6 months.
We believe that Microbially Enhanced Oil Recovery has the potential to improve the recovery of oil with the potential for very low capital investment and a much smaller environmental footprint compared to other EOR techniques.
Field Application of Very High Volume ESP Lift Systems for Shale Gas Fracture Water Supply in Horn River, Canada
Authors: Coppola Geoffrey C , Chachula Ryan C 
Published: October 2011

Abstract
Unconventional shale gas plays are emerging and undergoing rapid development at an alarming rate across North America. One of the most challenging dynamics of the Horn River, British Columbia, Canada shale play has been the increasing number of fracture stimulations required per horizontal wellbore. Of critical importance is the massive volume of water required to supply the 24/7 fracturing operations. In an effort to eliminate the reliance on surface waters, Encana engaged in a novel approach to produce high volumes of sour waters from a relatively unknown under-pressurized saline aquifer. The challenge was designin7g an appropriate high volume lift system capable of producing and achieving volumes of up to 8,500 m3/d/wellbore while addressing unknown fluid inflows, fluid transmissibility & re-charge, and reservoir fluid chemistry characteristics.
Electric submersible pumps (ESPs) have proved to be a successful and reliable artificial lift system for production of high volumes of fluid for many decades. This paper describes the steps undertaken by Encana in designing, piloting and successful field implementation of full scale high volume sour water lift ESP systems. These systems have demonstrated significant potential to alleviate the high costs, production withdrawal limitations and environmental impact of delivering large volumes of fracture supply waters in a remote Northerly region. Modifications to the wellbore completion architecture, equipment design and techniques to optimize pumping operations and water distribution from the field trials are presented.