bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupled Hydro Geomechanical Simulation and Analysis of Fault Reactivation: Influence of Fault Geometry
Authors: Asadi M. S. , Rasouli V. , Zhang Y. 
Published: February 2011

Abstract
Fault reactivation is one the unfavourable incidents during drilling and production due to changes in in-situ stresses and reservoir pressure. Only a few studies, in their analysis, have included the effects of fault geometrical properties, in particular length, dip angle and surface geometry, while these are important parameter controlling fault slippage.
In this paper, the significant influence of fracture morphology on the mechanical behaviour of rock masses is explained through virtual coupling of FDM/DEM numerical simulations. It will be shown how changes in fracture roughness and inclination angle lead to different failure mechanisms. DEM numerical simulation of synthetic fractures shearing in a bonded particle model was performed to investigate the effects of surface roughness on the creation of damage zones around the pre-existing fractures as a result of broken bonds between particles. Moreover, the effects of the ratio of shear to normal stresses on fracture sliding will be discussed analytically.
In the second part of this study, synthetic data from a sandstone reservoir was used for a field-scale FDM modelling to analyse fault reactivation and plastic deformation. Our focus is on shear failures close to the fault plane, which intersects the reservoir rock horizon in a field with normal fault stress regime being dominant. Pressures associated with fluid injection were increased until the fault being reactivated, and this was then analytically confirmed with the Mohr-Coulomb failure criterion. Sensitivity analyses were performed to examine the effects of state of in-situ stress, injection pressure, fault inclination angle, and surface properties on the potential of fault reactivation.
The results show that the extent of damage zone along a reactivated fault is highly influenced by fault surface geometry and injection pressure. The higher the inclination angle, the lesser the fault sliding strength. Sensitivity analysis of injection pressure and fault surface properties showed that fault reactivation potential is a function of multiple parameters, but more sensitive to the injection pressure than fault infills properties. It was also observed that the hydrocarbon flow path after fault reactivation is towards the sheared segments of a fault zone, where the permeability was increased. Large displacements were recorded where a large dip angle (here 63º) and a small friction angle (here 10º) were assigned to the fault surface. Distributions of shear strain are clearly heterogeneous along and near fault planes. This suggests that specific fault segments might be prone to experience leakage when others might retain a hydrocarbon column.
Dual Porosity Processes in Coal Seam Reservoirs: The Effect of Heterogeneity of Coal Matrices
Authors: Lu Meng , Connell Luke D. 
Published: February 2011

Abstract
The heterogeneous effect of coal matrices on flow profiles in coal seam reservoirs was discussed in this paper. To this end the flow equations in cleats were formulated to couple with a new fracture (cleat)-matrix transfer function that incorporates the statistical details of the heterogeneity regarding the diverse matrix block's sizes. The resultant flow equations were then described by a set of integral-(partial) differential equations, and we developed a novel quatrature scheme to deal with them. An enhanced-coalbed-methane-recovery (ECBM) problem was taken as an excise example, where the statistical data measured for a coal sample from a literature was used. With this example we discussed the relative errors of the flow profiles that were predicted with and without considering the statistical variances relevant to the heterogeneous effect, respectively. These profiles discussed include the methane production rate, the carbon dioxide injection rate, and the pressure transient response at the bottomehole of the production well. The relative errors for the cleat methane recovery in the field were also examined. It was shown that, for the flowrates and the pressure response at the wells, considerable errors (around 5% to 60%) may be observed when the heterogeneous effect concerned is neglected, especially in earlier times of operations (e.g., 0 to 15 days), whilst large errors (e.g., over 50%) for the cleat methane recovery may still exist in some areas in the subsurface after a much longer time (e.g., 400 days).
Case Study of Improved Oil-In-Place Determination from Petrophysical Evaluation of Resistivity Anisotropy Logging Data in a Malaysian Deepwater Turbidite Field
Authors: Manescu Adrian , Kho Sze-Fong , Ha Kwong-Tak 
Published: February 2011

Abstract
Deep-water turbidites can hold significant amounts of hydrocarbon reserves. One principal element of reserves estimation is accurate hydrocarbon-in-place determination. In this type of reservoir this value is often difficult to obtain as turbidites are primarily composed of thinly bedded shale and sand beds. When shale and sand lamina are below a tool's vertical resolution, petrophysical properties, for example porosity, are averaged across the shale and sand lamina. Also, resistivity measured by conventional induction devices is biased toward the low-resistivity lamina-component, e.g. shale. This creates the classical low-contrast, low-resistivity predicament where quantification of hydrocarbon saturations and net-to-gross is problematic.
Tensor resistivity measurements provide both horizontal and vertical resistivities. The vertical resistivity is more representative of the high-resistivity lamina component, e.g. hydrocarbon-saturated sand. The tensor resistivity measurements are also used to measure large-volume (cubic meters) formation dip and azimuth.
Tensor resistivity and nuclear magnetic resonance data were acquired in this deep-water turbidite field. The data were used to provide a more accurate hydrocarbon–in-place value than was obtainable using conventional resistivity measurements in low- contrast, low-resistivity shaly sand formations and to obtain formation dips and azimuths. A methodology directed at the sand- lamina petrophysical properties was used. Work was performed in a total porosity system, using dry-shale density calculated by comparing nuclear magnetic resonance (NMR) porosity data with the neutron-density porosity in shale.
By comparing the final analysis with core data, it is shown that the integration of tensor resistivity and NMR data accurately computes oil saturations, sand fraction porosity and net sand thickness. There is a large increase in the calculated cumulative hydrocarbon volume over conventional petrophysical approaches due to increased precision and accuracy in the sand-lamina porosity, hydrocarbon saturation, and net sand thickness determination.
The "Extreme Lean Profile" Concept as a Crucial Technology for Multilateral, Long Extended-Reach Wells: The Case History of Cerro Falcone 4 OR
Authors: Burini A. , Poloni R. , Valente P. , Cavallaro G. , Mattioli L. 
Published: February 2011

Abstract
Following the many successful applications of the "Lean Profile" (LP) technique, developed by Eni E&P some ten years ago, a further step towards production maximization with simultaneous increase of operational safety and decrease of the overall drilling cost has been recently achieved with the introduction of the "Extreme Lean Profile" (XLP).
Compared to a conventional profile, the LP has allowed running an additional casing between the 18 ⅝" and 13 ⅜" strings, the XLP introduces a further casing also between the 13 ⅜" and 9 ⅝" strings.
Previous papers have described this new concept. Instead, our main intent herein is to highlight how the use of the XLP can really make the difference for the success of drilling operations when it comes to drill long extended-reach wells.
This is the case of the onshore well Cerro Falcone 4 Or in the Val D’Agri field (Italy), the first ever deviated well being drilled by applying the XLP concept, without which the target could not be reached with the borehole size required for constructing the planned multilateral well.
The need to apply the XLP technology required overcoming many challenges due to the severe operational conditions experienced in drilling previous wells (hard, unhomogeneous and abrasive formations, hole instability, severe vibrations, mud losses).
This paper provides a comprehensive description of the well profile requirements, the associated operational issues, the chosen solutions and the actual challenges encountered during drilling operations. The achieved results are also described.
Based on the success of this XLP application, Eni E&P is considering to further develop this concept of narrow annuli, to insert additional casing strings: for instance a 8 ⅛" casing between the 9 ⅝" and 7" strings and a 5 ¾" casing between the 7" and 4 ½" strings.
Shale Gas Horizontal Production Logging Measurements and Challenges
Authors: Heddleston D. C. , Haggerty M. 
Published: February 2011

Abstract
Traditional shale formations are presently being produced via horizontal well completions. These horizontal wells consist of numerous selectively stimulated stages containing as many as 20 stages spread out across 2000 ft to 9000 ft interval.
The well completions have been stimulated using low technology methods such as high volume water / slick water &amp; sand. The initial production of the well requires a short period of flowback of the injected load water prior to the wells being kicked off with hydrocarbon production. The load water flowback can range from as little as 2% load return as high as 70% returns. Since these types of formations are far from being homogeneous, these horizontal laterals can intersect existing natural fractures or faults in the formation or an aggressive stimulation could induce fractures into existing natural fracture or faulting network.
This paper will showcase horizontal well production logging measurements ideal for this flowing environment in order to deliver a high confidence, representative flow profile.
In addition, deployment techniques &amp; the logging challenges will be discussed to establish the best possible representative flowing environment for measuring these types of well completions.
Permeability Prediction from Wireline Well Logs Using Fuzzy Logic and Discriminant Analysis
Authors: Nashawi I. S. , Malallah A. 
Published: February 2011

Abstract
The goal of this paper is to predict formation permeability from readily available wireline well log data measurements. The proposed method has many advantages. It is cost effective compared to permeability obtained from core analysis, and most importantly it provides a continuous permeability profile throughout a particular formation horizon as opposed to the permeability obtained from well test analysis, which provides an average value for the entire drainage area of the well.
The method presented in this paper delineates a general methodology for permeability prediction from well log data. First, principal components analysis, cluster analysis, and discriminant analysis are consistently used to identify and categorize clusters based on the unique characteristics of well log measurements reflecting reservoir mineralogy, fluid content, and hydraulic properties within the logged interval; then, fuzzy-logic model is applied to each cluster to determine the formation permeability within the specified interval. Actual field data obtained from a highly complex heterogeneous sandstone reservoir are used to demonstrate the applicability and competence of the proposed technique.
Debottlenecking through Heat Integration Case Study: Crude Distillation Unit
Authors: Aseeri Ahmed S. , Amin M. Shahid , Ibrahim Mahmoud S. 
Published: February 2011

Abstract
Heat Integration of process plants leads to better energy conservation. This energy conservation can be utilized for increasing the capacity. In many plants the energy supply is the bottleneck for expansion. In such cases better heat integration can be used to overcome this bottleneck. In this paper we will talk about a case study that was done for debottlenecking a Refinery Crude Distillation Unit (CDU) through heat integration. The energy sources in this case are the furnaces. The maximum heat duty of the furnaces is limited by its design. The conventional solution for such a case is addition of another furnace or replacement by other furnaces of higher capacity.
The unit consists of the crude preheat train Heat Exchanger Network (HEN) in which the heat recovery shall be increased through better integration. The better integration is achieved at two levels, namely the network level and the exchanger level. For retrofit projects the modifications shall be minimal in order to achieve economic feasibility. For this reason the preheat train was divided in three sections depending on the plant layout. The analysis was first done for each section individually followed by the analysis for the whole preheat train, the three sections collectively.
The outcome of this study was a heat-integration-based retrofit design that will give a 20% increase in throughput utilizing the same existing furnaces and hence same energy consumption. This means a 20% more energy-efficient design yielding the saving of about 100 million Btu/hour of fuel gas and an estimated CO2 emissions reduction of 40,000 tons/year. Moreover the capital cost of this proposal is estimated to be 40% less than the traditional solution of adding a new train. Other components of the CDU including columns, vessels, furnace, piping and pumping systems were also analyzed and modified in accordance to the proposed new design.
Performance Assessment of the DC All-Electric Subsea Production Control System
Authors: Abicht Daniel , Braehler Johannes 
Published: February 2011

Abstract
This Paper describes the performance assessment program initiated for the first operating DC All Electric Controls System. An overview of the applied method considering both model and data uncertainties will be provided. Also the experience gained through operation after successful installation and commissioning of the system to date will be addressed.
While presently collecting operational experience subsea, significant data and processing capabilities of the first operating DC All Electric Controls System can be assessed. Key parameters of interest and their context are investigated in a thorough detail. This allows a permanent observation of the state of the system. By means of this approach expert confidence level increases as additional decision support is provided. This systematic condition evaluation is based on a continuous probabilistic investigation which complex physical phenomena tend to impose. Preventive planning of maintenance is enabled and leads to long term cost reduction.
The CameronDC™ system allows continuous condition monitoring which next to several others can be seen as a key enabler for All Electric Subsea Controls Systems. The presented one uses the concept of end to end redundancy, consistently from surface to the subsea actuators. It also employs high voltage DC electrical supplies, providing the advantages of minimized energy losses, and a true environmental friendly design, in line with the zero discharge concept.
Well Productivity Index Degradation - Applied Modeling Workflow
Authors: Saputelli L. , Perez J. , Chacon A. , Lopez C. , Patino J. , Eggenschwiler M. 
Published: February 2011

Abstract
Productivity index (PI) reduction is a recognized phenomenon in oil and gas production to the extent that production becomes uneconomic. Productivity index (PI) decrease may be caused by several factors arising from reservoir, completion, and operational issues. The reservoir-related factors include compaction, fines migration, pressure support and multi-phase fluid flow. The completion-related issues arise from frac-pack geometry and stress-sensitivity of proppant conductivity. Finally, operational issues such as pressure drawdown at the sandface and induced flux (the movement of fluids across the completion) may also play a large role in PI degradation. Understanding the interactions of different parameters controlling the PI behavior and the resultant well performance is paramount for maximizing the ultimate recovery and net-present value or NPV. PI modeling may offer several challenges because it involves non-unique solutions for reservoirs and near-wellbore and well-completion status, in addition to manual data entry subject to human errors, uncertainties in reservoir parameters, and poor quality field data.
This study presents a workflow for modeling well PI degradation for an over-pressured gas/condensate reservoir in deep offshore Gulf of Mexico. An automated procedure was tailored and applied to match production history by adjusting both the reservoir and well completion parameters. Among the reservoir parameters considered were horizontal stresses, rock compressibility, absolute permeability, relative-permeability endpoints and curvature, porosity, stress-sensitive permeability and porosity. The well completion parameters included fracture length, height, width, conductivity, and stress. A "Tabu Scatter Search" optimizer engine (April et al, 2003) selected the optimal values of a set of input parameters to minimize the objective function, i.e. the error between the measured and calculated PI values.
Both reservoir and well completion parameters contributing to PI degradation were identified, and compared to those obtained by alternate methods. The relative and combined contributions of stress-sensitive reservoir compressibility, permeability, porosity, and fracture conductivity all helped understand well performance and guide decisions towards optimum well operating envelope.
Integrated Use of Natural Gas in Rural China
Authors: Economides Michael J. , Wang Xiuli 
Published: February 2011

Abstract
For China to reach a semblance of a developed country's energy profile is perhaps the biggest social and economic challenge of the world today.
China's challenges are formidable and they fall into three categories. The first is to find adequate supply to meet the large current and even larger future demand. China does not have sufficient indigenous resources and will have to import and therefore compete with other countries, such as Europe, for Russian gas. The second is China's energy makeup which is still very primitive (70% of China's energy comes from coal, a share that the West has not seen since the nineteenth century). This affects pollution, emissions, and efficiency. The third is geographical distribution with very large imbalances between the rural and urban populations of China.
Natural gas, which currently accounts for less than 4% of China's energy mix but is in great abundance internationally, must increase at least by an order of magnitude in a fast pace. Natural gas offers the only hope as a pollution-acceptable fuel for power generation and, very importantly, as a motor vehicle fuel. Currently, the Chinese use approximately 35 times less natural gas per capita than that used in Western Europe or the United States. Also we estimate that 80% of the Chinese public has no access to natural gas either directly or indirectly.
With this situation, we offer different forecasts of the energy future and present scenarios for natural gas distribution in China by making use of a navigable river. We take into account existing systems and estimate the required infrastructure to bring minimum natural gas (e.g., 30% of natural gas per capita use in the United States) to 80% of Chinese people.
Optimum Injection Rate of A New Chelate That Can Be Used To Stimulate Carbonate Reservoirs
Authors: Mahmoud M. A , Nasr-El-Din H. A. , De Wolf C. A. , LePage J. N 
Published: February 2011

Abstract
Different chelating agents were used as alternatives for HCl in matrix acidizing to remove near wellbore damage and create wormholes in carbonate formations. Previous studies have demonstrated the use of ethylenediaminetetraacetic acid (EDTA), hydroxy ethylenediaminetetraacetic (HEDTA) and glutamic acid-N,N-diacetic acid (GLDA) as an alternative for HCl to stimulate carbonate reservoirs. The main problem with EDTA and HEDTA is the low biodegradability.
GLDA was introduced as alternative for HCl for stimulating deep carbonate reservoirs at which HCl will cause corrosion and face dissolution problems. In this study calcite cores, 1.5 in. diameter with 6 and 20 in. length were used to determine the optimum conditions where the GLDA can breakthrough the core and form wormholes. GLDA solutions with pH values of 1.7, 3, and 3.8 were used. The optimum conditions of flow rate and pH were determined using the coreflood experiments. CT scan was used to determine the wormholes length and diameter to determine of optimum Damkӧhler number. GLDA was compared with chelates that are used in the oil industry such as EDTA and HEDTA. GLDA also was used to stimulate parallel cores with different permeability ratios (up to 6.25) to assess its ability on diversion.
GLDA was found to be very effective in creating wormholes at pH = 1.7, 3, and 3.8 at different injection rates at temperatures of 180, 250, and 300°F. Increasing the temperature increased the reaction rate and less amount of GLDA was required to breakthrough the core and form wormholes. Unlike HCl and EDTA, there was no face dissolution or washout in the cores even at very low rates. Also, an optimum flow rate and Damkӧhler number were found at which the pore volume required to create wormholes was the minimal. GLDA at pH 1.7 and 3 created wormholes with a small number of pore volumes. Compared with acetic acid the volume of GLDA at pH 3 required to create wormholes was less than that required with acetic acid at the same conditions. GLDA was found to be effective in stimulating parallel cores with different permeabilities.
Reverse Osmosis Compatible Chemical Foamers For Gas Well Deliquification And Production Enhancement
Authors: Willis Martin J. , Conrad Greg A. 
Published: February 2011

Abstract
In times of increasing energy demand the need for more natural gas is greater than ever. To address this demand there are many drilling campaigns of coal seam gas (CSG) wells to supply the new liquefied natural gas (LNG) plants. Typically, within these wells progressive cavity pumps (PCP) are used to unload water to facilitate gas production. The produced water is then commonly processed by reverse osmosis (RO) to provide water suitable for re-use in other industries.
Previously PCPs were the only feasible pumping option, due to the presence of particulates, which is a relatively expensive deliquification method. Nalco has developed an alternative artificial lift method in the form of a liquid chemical foamer. This method offers cost efficient lift that will support initial liquid unloading as well as aid liquid management to maturation, enhancing lifetime production and lowering operating expense. In addition the technology offers secondary benefits for corrosion management, improving potential asset longevity.
The chemical has been demonstrated to perform in typical CSG brines and in the presence of coal fines, however the significant technology breakthrough is the compatibility with the RO membranes. Conventional foamer surfactants are incompatible and compromise safe, efficient unit operation. The laboratory and field data to demonstrate these claims is presented within.
To further enhance the technology offering a total deliquification approach has been developed, combining the chemical with a patented injection system. Appropriate steps have been taken to ensure the chemical is compatible with the injection system hardware and operating conditions, and most importantly benefits from the novel atomizer valve. In comparison to standard injection valves significant gains have been recorded in the field circa. 30%. The process of well selection, hardware installation, chemical treatment and monitoring is detailed within the paper.