bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Reservoir Inflow With Pulsed Neutron Logs Under Subcriticai Flow Conditions
Authors: Poe B. D. , Butsch R. J. 
Published: December 2007

Abstract
This paper presents some recent developments in a production logging technique that utilizes Pulsed Neutron log measurements for the evaluation of the formation inflow into a wellbore, of which one or more of the completed intervals may be located in the annulus between the casing and tubing strings above the end of the tubing. Of particular importance in this work is the capability of determining the formation inflow profile in the well in cases where the well outflow velocity is less than that required to continuously transport and unload liquids from the well. Sub-critical velocities are commonly encountered in low productivity gas wells that produce liquids, whether they are produced directly from the formation and/or condensed well fluids, water and hydrocarbons.
This paper presents a sub-critical velocity analysis that has been implemented in a Pulsed Neutron production logging technique in order to have the capability to reliably evaluate the formation inflow into wells in which the velocities are so low that no other production logging methodology is possible. Coupled with the numerical modeling of the Pulsed Neutron production log evaluation, test pit measurements of the annular flow water velocities with the Pulsed Neutron logging technique have been reliably and accurately measured to as low as 3 ft/min (0.05 ft/s).
Stability Analysis of Deviated Boreholes Using the Mogi-Coulomb Failure Criterion, With Applications to Some Oil and Gas Reservoirs
Authors: Al-Ajmi A. M. , Zimmerman R. W. 
Published: December 2007

Abstract
Borehole collapse is the commonly encountered wellbore stability problem during drilling. The precursor of such borehole failure can be often eliminated by a proper determination of the critical mud pressure. Recently, Al-Ajmi and Zimmerman developed a new 3D analytical model to estimate the mud pressure required to avoid shear failure (i.e., borehole collapse) at the wall of arbitrary oriented boreholes. This had been achieved by using linear elasticity theory to calculate the stresses around the borehole, in conjunction with the fully-polyaxial Mogi-Coulomb criterion to predict failure. The developed model has been used to study the behaviour of the collapse pressure under different in situ stress regimes. We have found that the optimum drilling trajectory is directly related to the principal in situ stresses. Accordingly, we have developed a new analytical solution to optimize well path. The stability model has been applied to several field cases, and the new model in each case is consistent with the field experience. It has been concluded that the optimum wellbore profile can be ensured by employing the developed analytical stability model.
Simulation of Nitrogen Injection into Naturally Fractured Reservoirs Based on Uncertain Properties and Proper Matrix Grid Resolution
Authors: Vicencio O. A. , Sepehrnoori K. 
Published: December 2007

Abstract
This paper addresses a study of nitrogen injection in naturally fractured reservoirs based on uncertain properties that impact the nitrogen distribution and the oil recovery under gravity drainage mechanism. This research focuses on sensitivity studies based on matrix block sizes and capillary continuity to access their impact on the gravity drainage mechanism. In addition, a study of the matrix grid resolution was performed to investigate the effects of vertical and horizontal subgridding on matrix oil recovery.
This study is a continuation of a research which considered a simulation of nitrogen injection through different scenarios by using the same conceptual model with isotropic and anisotropic matrix blocks, the injection of different gases and the construction of a thermal compositional case study to determine the variations of temperature that mainly occur in the gas cap.
ECLIPSE commercial simulator with compositional formulation and dual porosity option was used for the field simulation case studies. Simulation results considering variations in matrix block sizes with same shape factor indicated that gravity drainage mechanism depends not only on matrix block size but also on reservoir depth and nitrogen arrival time. For all cases studies, highest oil recovery was obtained for slabs with biggest matrix block height.
Furthermore, our sensitivity studies for capillary continuity were performed using several fracture apertures considering block size with 10 ft height. Simulation results indicated that oil recovery is affected by a factor that range from 1 to 2.2 by considering fracture apertures between 10 to 300 microns. Since fracture aperture histogram for the reservoir under study averaged 250 microns; discontinuity capillarity is a good approximation for the reservoir under study. Our simulation results suggest that for a naturally fractured reservoir study is necessary to reduce uncertainty of fracture apertures because it strongly impacts the oil recovery.
Subsequently, we investigate the effects of matrix subgridding in vertical and horizontal directions on total oil production by using a stack conceptual model of two matrix blocks surrounded by fractures. The matrix and fracture systems were divided into a number of Cartesian sub-grids and we used the compositional single porosity model of ECLIPSE 300 to perform our simulation runs.
Simulation results indicated that oil recovery for a grid refinement case study using 3×3×68 gridblocks was higher by a factor of 1.124 than the base case using 3×3×5 gridblocks. In addition, the total oil production for the case using 9×9×68 gridblocks was higher by a factor of 1.09 in comparison with the case using 3×3×5 gridblocks. Based on our simulation results; we concluded that subgridding is specially important when we have gravity drainage as the main oil recovery mechanism.
New Representative Curves for Gas Lift Optimization
Authors: Salazar-Mendoza R. 
Published: December 2007

Abstract
The typical GLR sensitivity curves for gas-lift design and optimization are obtained for a constant wellhead pressure when the system sensitivity study is for a single well system and for a first-stage separator pressure or fixed pressure when the system sensitivity study is for a complete surface production network modeling.
In this paper a production analysis for a six gas-lifted wells system with a new representative curves for gas-lift optimization is presented. These new representative curves were obtained for the complete surface production network modeling that links the well models with the surface network model. Two cases are analyzed: 1) All the six wells are operating and flowing simultaneously and 2) Only one well is operating and flowing alone. The representative curves for each case analyzed were compared with the typical GLR sensitivity curves. The results show that the representative curves are in a better agreement with the profile of measured data.
Overbalanced Perforating Yields Negative Skin Values in Layered Reservoir
Authors: Pizzolante Italo , Grinham Steve , Xiang Tian , Lian Jihong , Khong Chee Kin , Behrmann L. A. , Mason Steve 
Published: December 2007

Abstract
China National Offshore Oil Corporation (CNOOC), Chevron, and ENI, the field operator, are partners in the development of the HZ oil and gas fields, operating as the CACT Operators Group (CACT) in the South China Sea. The HZ fields are stacked, thin, high-permeability sandstone reservoirs interlayered with low-permeability layers. The shallower layers generally have better permeability and were developed first while the deeper, lower-permeability reservoirs have been developed more recently.
The lower-permeability reservoirs are generally of lower porosity and higher compressive strength. Drilling-mud-filtrate invasion also tends to be deeper. Deep-penetration perforating charges are required to perforate past the damaged zone. Experience indicates that underbalance perforation provides better productivity compared to overbalance perforation.
Although conventional underbalance perforation can be performed using pipe-conveyed or tubing-conveyed perforation (TCP), depth uncertainties and the time requirement for TCP service in thin reservoir zones makes wireline-conveyed perforation an attractive method. However, where multiple zones must be perforated, the conventional wireline approach can only perforate the first zone underbalance (with the completion fluid weighted accordingly) while subsequent zones could only be perforated balanced at best.
A new perforating system, designed to generate a large dynamic underbalance with a static overbalance, was used to perforate new wells for the development project to maximize well productivity per well expenditure.
A multilayer production evaluation of one of the wells perforated with the dynamic underbalance method produced a zero skin value in the 9-md layer and a −0.97 skin value in the 1600-md layer. Conventional underbalanced perforation, employing multiple wireline runs, could not achieve these low skin values over this wide range of permeabilities.
Organically Crosslinked Polymer System for Water Reduction Treatments in Mexico
Authors: Vasquez J. , Jurado I. , Santillan A. , Hernandez R. 
Published: December 2007

Abstract
This paper presents the application of an organically crosslinked polymer (OCP) system, a system widely used in the oil industry for water shutoff applications. The OCP system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneimine (PEI). To date, about 100 jobs have been performed with this system in Mexico to address conformance problems such as: Water coning/cresting.High-permeability streaks.Gravel pack isolation.Fracture shutoff.Casing leak repair.
This paper presents an overview of case histories that used OCP in various regions of Mexico for a wide variety of applications. In particular, a case history of an offshore well treated with the OCP is presented. A direct comparison of the application of the OCP with conventional cement squeeze treatments is presented to illustrate the advantage of having a deep matrix penetration for a more efficient water shutoff. In addition, data presented in this paper indicate the development of a retarder that allows the upper placement temperature of the OCP system to be raised to at least 350°F. The upper placement temperature of the system originally was ~260°F.
A Multiple-Continuum Approach for Modeling Multiphase Flow in Naturally Fractured Vuggy Petroleum Reservoirs
Authors: Wu Yu-Shu , Qin Guan , Ewing Richard E. , Efendiev Yalchin , Kang Zhijiang , Ren Yulin 
Published: December 2007

Abstract
The existence of vugs or cavities in naturally fractured reservoirs has long been observed. Even though these vugs can be largely attributed to reserves of oil, natural gas, and groundwater, few investigations of vuggy fractured reservoirs have been conducted. In this paper, a new multiple-continuum conceptual model is developed, based on geological data and observations of core samples from carbonate formations in China, to investigate multiphase flow behavior in such vuggy fractured reservoirs. The conceptual model has been implemented into a three-dimensional, three-phase reservoir simulator with a generalized multiple-continuum modeling approach. The conceptual model considers vuggy fractured rock as a triple- or multiple-continuum medium, consisting of (1) highly permeable fractures, (2) low-permeability rock matrix, and (3) various-sized vugs. The matrix system may contain a large number of small or isolated cavities (of centimeters or millimeters in diameter), whereas vugs are larger cavities, with sizes from centimeters to meters in diameter, indirectly connected to fractures through small fractures or microfractures. Similar to the conventional double-porosity model, the fracture continuum is responsible for the occurrence of global flow, while vuggy and matrix continua, providing storage space, are locally connected to each other (and interacting with globally connecting fractures). For practical application of the multi-continuum concept in reservoir simulation, we propose a novel upscaling method for computing equivalent gridblock permeabilities of coarse blocks containing large isolated vugs, in which the local problems consisting of Darcy and Stokes flows are solved. In addition, we describe an efficient boundary condition for accurate computation of upscaled permeabilities. In the numerical implementation, a control-volume, integral finite-difference method is used for spatial discretization, and a first-order finite-difference scheme is adapted for temporal discretization of governing flow equations in each continuum. The resulting discrete nonlinear equations are solved fully implicitly by Newton iteration. The numerical scheme is verified and applied to simulate water-oil flow through the fractured vuggy reservoirs of the Tahe Oil Field in China.
Percussion Drilling: From Laboratory Tests to Dynamic Modeling
Authors: Han Gang , Bruno Mike 
Published: December 2007

Abstract
Percussion drilling has long been considered an effective approach to breaking rock in the civil and mining industries. A large number of air hammers were introduced to oil and gas industries in the 1980′s. However, limited fundamental understandings of the physical mechanisms involved in percussion drilling hinder its acceptance and applications.
In a 2-year research effort, fundamental rock physics are investigated through a series of lab tests, including single impact tests and full-scale hammer drilling tests. For each impact test, three impacts are sequentially loaded at the same rock location to investigate rock response to repetitive loadings. Besides crater depth and width, the displacement and force in the rod and the force in the rock are recorded at 100K Hz frequency. For hammer drilling tests, an industrial fluid hammer is used to drill Berea sandstone and Mancos shale under both underbalanced and overbalanced conditions. The bottom hole pressure varies from 3.5MPa to 20.7MPa while pore pressure is controlled separately, varying from 0MPa to 24.2MPa. During these tests, Rate of Penetration is recorded continuously from one pressure condition to another. Cuttings are then screened, collected, and analyzed.
The lab data are then used to calibrate a 3D drilling simulator developed specifically for percussion drilling. First a strain-softening rock material model is derived from matching rock stress-strain curves in a series of rock mechanical tests. Then a stress history is specified as loading conditions based on the stress and displacement data recorded in the impact rod. With appropriate material model and boundary conditions, both rock displacement and indentation geometries are well matched. Further, the simulation reveals in detail how rock becomes defragmented when receives impact. These developments improve the fundamental understandings of rock physics involved in hammer drilling. The 3D drilling simulator can also be applied to investigate rock breakage and optimize operations in field.
The Effect of Well Trajectory on Horizontal Well Performance
Authors: Bond A. , Zhu D. , Kamkom R. 
Published: December 2007

Abstract
Horizontal wells provide extended contact with the reservoir, and have unique advantages over vertical wells in many applications. As nominally horizontal wells get longer and follow more complicated trajectories, wellbore hydrodynamics becomes an important issue on well performance. In this paper, we will discuss a problem in horizontal wells - the elevation change in well trajectory and its effect on well performance. In general, a horizontal wellbore is never perfectly horizontal. The inclination angle could be a result of drilling control, or sometimes could be designed on purpose for an extremely anisotropic formation. When vertical permeability is much smaller than horizontal permeability, an undulating wellbore may be favorable to overcome the low vertical permeability. Undulation in wellbore trajectory will change the inflow distribution along the wellbore, and therefore change the wellbore performance. When two-phase flow is involved, especially gas-liquid flow, the pressure distribution in the wellbore may cause flow problems, such as trapping gas because of accumulated liquid at low spots. We use a simple analytical model to examine the flow conditions for inclined or undulated horizontal wells. The reservoir inflow is interactively coupled with the wellbore flow, and the pressure and flow rate distribution are predicted by the model.
The model then is used to analyze the development plan for the Cosmopolitan field in Alaska. The field has stress-dependent permeability, and the vertical permeability is much lower than the horizontal permeability. The results of the model explain the effect of wellbore trajectory on well performance of horizontal wells, and justify the benefits of undulating wellbores in horizontal well development in this low vertical permeability reservoir. The study showed that undulating wells in the Cosmopolitan field can help to improve well productivity.
Lasers: The Next Bit
Authors: Pooniwala Shahvir 
Published: December 2007

Abstract
Since the early twentieth century rotary drilling has revolutionized the procedure of extraction of crude oil replacing conventional methods like cable tool drilling. However with the advent of new technology it is time to look at future alternative, more efficient drilling methods.
This paper acts as an eye opener to the feasibility of using laser drilling over modern currently used drilling techniques.
The design and operation of a new laser-mechanical bit is put forth by the medium of this paper. This innovative bit shows probability of reducing rig time and increasing efficiency in drilling.
The possible changes to be implemented in the present day drill string due to incorporation of this new bit is accounted for and an analysis of the possible advantages and disadvantages of this bit if implemented is also highlighted.
Smart-Well Completion Utilizes Natural Reservoir Energy to Produce High-Water-Cut and Low-Productivity-Index Well in Abqaiq Field
Authors: Al-Otaibi Nashi M. , Al-Gamber Abdulwafi A. , Konopczynski Michael , Jacob Suresh 
Published: December 2007

Abstract
Innovations and smart well technology applications have helped overcome the challenges of complex and mature fields such as the Abqaiq field. This paper presents the application of smart well technology in utilizing "free energy" from an overlying gas cap to produce high water-cut and low productivity wells completed in underlying reservoirs.
The smart well completion was implemented in Abqaiq field to naturally gas lift an intermittent well (a well which cannot continuously flow to the surface), completed in the low permeability Hanifa reservoir. The well is drilled through the gas cap having 40 ft of gas column in the upper section of Arab-D reservoir. In this application, the smart well completion consists of a surface controlled, hydraulically operated downhole choke valve that regulates the gas inflow from the gas cap into the production tubing. This application eliminates the need for artificial lift infrastructure at the surface and operational expenditures. Using gas cap energy basically is providing free energy. This paper discusses selection criteria of smart well application to naturally lift an oil producer by utilizing energy from an overlying gas cap, completion & operation experiences and production optimization. Results show the applicability of natural gas-lift dependent upon standoff (with respect to the initial gas-oil and water-oil contacts) and target production rate. The paper addresses design considerations for natural gas-lift applications and report the operational experience gained in the Abqaiq field with gas-cap gas-lift applications.
Tubing Buckling—The State of the Art
Authors: Mitchell R. F. 
Published: December 2007

Abstract
Almost unique in engineering analysis is the problem of tubing buckling in wellbores. In general, structures loaded above their critical load fail catastrophically. Yet, both tubing and drillstrings are commonly operated above the critical load. These tubing strings do not fail because the wellbore provides the necessary support for "post-buckling" equilibrium.
The two fundamental questions about tubing buckling are:
What is the critical load?
What is the post-buckled configuration?
The critical load tells us if the tubing will buckle. Euler solved the problem for "short" columns, but these results rarely have application in a wellbore, because the pipes are usually very long1. The first stability criterion which considered the stabilizing effect of weight on long pipes in inclined wellbores was developed by Paslay and Dawson2.
The post-buckled configuration tells us about tubing movement, bending stresses, contact forces, and axial load distributions. The original buckling analysis by Lubinski and Woods3 proposed a helical configuration in a vertical wellbore, and used the method of virtual work to determine a specific constant pitch for that helix, as a function of the axial force and bending stiffness.
These two works set the following themes for further analysis of tubing buckling:
What is the critical buckling load in curved, three dimensional wellbores? How does torque affect the critical buckling load? How do tapered strings affect the critical buckling load? What is the buckling configuration in inclined wellbores? How do the boundary conditions affect the configuration? How do tapered strings buckle? How does torque affect the buckling configuration? What effect does friction play in tubing buckling?
Many of these questions have been, at least, partly answered in the three decades since the original papers were published. This paper will examine the technical fundamentals of the tubing buckling problem, summarize the most useful new results from these papers, and discuss the remaining challenges in tubing buckling analysis.
Oil and Gas Industry Partnership With Government to Improve Cybersecurity
Authors: Aubuchon Tom , Susanto Ivan , Peterson Brian T. 
Published: December 2007

Abstract
The Oil & Gas industry faces common challenges in securing its process control systems. These SCADA and DCS systems are critical to the industry because they control the operations of oil fields, pipelines and refineries. These systems are also critical to a nation's infrastructure and are essential to its national security, public safety, economic well-being and way of life. Within a critical infrastructure environment, addressing security is a shared problem that needs to be addressed collaboratively. Until now, little progress had been made to address this issue from an industry-wide standpoint.
Linking Oil & Gas Industry to Improve Cyber Security (LOGIIC) is a partnership of the Oil & Gas industry with the U.S. Department of Homeland Security (DHS). This partnership brings together the best resources from participating industry members, government, and the research community. The LOGIIC correlation project represents the first time a public-private collaborative model has been implemented to address a critical Oil & Gas industry research and development issue in cyber security. This partnership resulted in innovative improvements being made to cyber security on process control networks.
This paper describes the LOGIIC model and explains how industries can work together with government and process control system and security technology vendors to address common challenges. Details of the project are discussed, including: how the testbed was created; what attack scenarios were developed and implemented; and how actual process control activities were simulated in a lab environment. It also describes the lessons learned from the partnership and our future plans to collaborate with government on cyber security issues.
NOTE: Substantial portions of this paper are from various LOGIIC documents and presentations. Some images and portions of this paper have already been presented at LOGIIC meetings and other related conferences, and may be included in future presentations or publications.