bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitigating Oil Bypassed in Fractured Cores During CO2 Flooding Using WAG and Polymer Gel Injections
Authors: Chakravarthy D. , Muralidaharan V. , Putra E. , Hidayati D. T. , Schechter D. S. 
Published: December 2007

Abstract
Fractured reservoirs have always been considered as poor candidates for enhanced oil recovery. The fractures provide a pathway for injected fluids to channel through directly from injection to production wells. The interaction between these fractures and the reservoir rock matrix often determines the degree of bypassing during injection of CO2. The use of CO2 as a displacing agent through these reservoirs aggravates the problems of low sweep efficiency due to its high mobility. The microscopic displacement efficiency of CO2 is very high, but the overall displacement efficiency is often hindered by its high mobility that is largely the results of viscosity and density contrasts between the CO2 phase and the reservoir oil and brine phases. In this study, we performed CO2 injection experiments with different injection rates and utilized X-ray CT to determine the saturation distribution along the core and measure oil bypassed during CO2 process in fractured cores. We improved the CO2 sweep efficiency by controlling the CO2 mobility in the fracture. Water viscosified with a polymer was injected directly into the fracture, to divert CO2 flow into the matrix and delay breakthrough. Although the breakthrough time reduced considerably, water "leak off" into the matrix was very high. To counter this problem, a cross-linked gel was used in the fracture for conformance control. The gel was found to overcome "leak off’ problems and effectively divert CO2 flow into the matrix. This experimental results increase the understanding of fluid flow and conformance control methods in fractured reservoirs.
Numerical Simulation of the Storage of Pure CO2 and CO2-H2S Gas Mixtures in Deep Saline Aquifers
Authors: Ozah R. C. , Lakshminarasimhan S. , Pope G. A. , Sepehrnoori K. , Bryant S. L. 
Published: December 2007

AbstractWe have studied strategies for maximizing several phenomena beneficial to large-scale subsurface storage of waste gases such as CO2 and H2S. Numerical simulations using a compositional reservoir simulator were carried out for 10,000 years to understand the flow and long-term storage potential of pure CO2 and CO2-H2S mixtures in deep saline aquifers. Hysteresis in the relative permeability curve results in substantial volumes of gas trapping. Aquifer characteristics such as heterogeneity, dip angle and vertical to horizontal permeability ratio were varied to determine their effect on storage potential and injectivity of a CO2-H2S gas mixture. The opportunity for escape of the gases from the aquifer can be minimized by careful design of injection strategies. One such strategy is to use horizontal wells low in the formation so that all of the injected gases are trapped, dissolved or precipitated before they reach geological seals and/or faults. This allows significantly larger volumes of waste gases to be stored in a given aquifer. Preferential solubility of the H2S in brine reduces the distance H2S travels relative to CO2. Simulations with local grid refinement show that fingering due to buoyancy is mitigated by natural heterogeneity in the aquifer petrophysical properties. Thus the amount of gas trapping observed in coarse-grid simulations is likely to be a reasonable estimate of what can be obtained in the field. Three-dimensional simulations of coupled flow and reactive transport showed that the amount of CO2 sequestered as minerals was small relative to gas trapping and dissolution into brine. However, the mineralization further reduces the already small amount of mobile gas over long periods of time.
Stochastic Modeling of Fluvial Reservoirs: The YACS Approach
Authors: Alapetite J. , Leflon B. , Gringarten E. , Mallet J. -L. 
Published: December 2007

Abstract
This paper describes a novel approach to model fluvial reservoirs. The core of the method lies in the association of a fairway or river bed with the channels to be simulated. A potential field is defined within the fairway. Specifying a transfer function to map this potential field to thickness results in a generating a channel inside the fairway. A residual component is stochastically simulated and added to the potential field creating sinuosity and realistic channel geometries. The degree of deformation is controlled and allows the creation of channels with high sinuosity including oxbows. Conditioning to well data is obtained by applying the inverse transfer function at the data location to derive thickness values which will constrain the simulation of residuals. Fairways are positioned so that all data are taken in account; they can be stochastic if unknown or explicitly entered if identified on seismic data.
The method allows simulating channels which honor both exactly hard well data and channel proportions, following arbitrary shapes guided by fairways. The algorithm is based on sequential algorithms which guarantee convergence and speed; there is no iteration or optimization loop. This new approach can simulate channel, levees, and also lobes; channels can have multiple branches and conditioning a single channel (branch) to multiple wells is also possible.
Horizontal Screen Failures in Unconsolidated, High-Permeability Sandstone Reservoirs: Reversing the Trend
Authors: Arukhe J. , Uchendu C. , Nwoke L. 
Published: December 2007

AbstractHorizontal screen failures can be serious, resulting in expensive remedial operations including early abandonment, in the extreme case.Globally, screen failures in horizontal wells completed in loose unconsolidated sandstone reservoirs have become common. Consequently, from completion and longevity perspectives, a high percentage of horizontal wells have not achieved the desired result: sand-free, high sustained-productivity producers. Individual companies have performed studies in this direction, and some are still ongoing. From preliminary data available, however, it has been possible to observe trends and determine the failure mechanisms.Failure categories highlighted in this paper include wells with significant impaired productions or those completely plugged, representing an overall failure rate of almost 20%. This paper suggests several levels of screen failure: screen collapse or complete plugging, partially plugged screens (poor performing wells) and those producing unacceptable amounts of sand. Other failures include improper installation and economic failures where fixing the problem is possible but costly. Some wells exhibited ‘’early mortality’’, producing sand at production onset.The study further categorized possible causes of screen failures into three major areas: ➣Screen plugging caused by high-pressure drops across screens, hot spots of localized production, fines and dirty sand.➣Incorrect procedures, materials or equipment selection including trouble installing the screens, corrosion in low spots due to standing acid, generalized corrosion from acids, improper cleanup, ineffective mud removal, ineffective sand control, inappropriate screen selection and erosion.➣Poor reservoir understanding in the areas of grain size distribution, sanding up due to water production, open annular areas due to higher than expected rock strength.This paper reviews various applications of soft rock completions in horizontal service, along with benefits and shortfalls. The performance characteristics of the various screens relative to each other from the perspective of flow capacity, plugging and erosion resistance are examined. Recommendations based on ‘’best practices’’ being adopted to combat screen failure problems in high permeability reservoirs are also showcased.
Gulf of Mexico Shelf Deep Ultra-HP/HT Completions—Current Technology Gaps
Authors: Hahn D. , Atkins M. , Russell J. , Pearson B. 
Published: December 2007

Abstract
Numerous operating companies are pursuing new and much deeper geologic horizons on the Gulf of Mexico continental shelf. This is a logical expansion of a geographic area with a very mature and well established surface infrastructure. However, as the well depths increase, the wellbore construction and well production operations become much more challenging because ultra-high pressures and high temperatures - HPHT (e.g. 25,000+psi and 450+°F) will then need to be handled and/or managed. The industry is probably able to safely drill these more extreme wells but there are some significant well completion technology gaps that require design and development. The most cost efficient approach to bridge these gaps may be for several companies to collaboratively share in the costs to develop the appropriate equipment for these applications.
This paper demonstrates the need to enhance the industry's capability to actually begin production from these deep ultra HPHT wellbores. The numerous areas that require increased completion capability will be presented in this paper. The production tubulars (casing and tubing) will be a major cost driver as designs will need to address temperature deration of strength, geometric complexity to achieve adequate bore and clearances, corrosion and environmental cracking. Risk analyses and testing will dictate metallurgy, pressure containment, connection capability under compression and bending, and benefits and reliability of cementing. Production packers, subsurface safety valves, and flow control nipples/plugs appear to be the nearest to implementation, but some design and qualification issues still need to be resolved. Current perforating technologies are reaching their limits at temperatures exceeding 450°F, thus require significant attention in their specific application and a quality assurance/quality control (QA/QC) program. The major hurtle for fully rated completion blowout preventors (BOP's) and trees will be the need to redesign the valve stem sealing mechanisms. Finally, both intervention and contingency possibilities, like slickline, pumping services, stimulation, snubbing, etc., are important situations that require additional enhancements to currently available technologies.
Diverse Application of Unique High-Performance Water-Based-Mud Technology in the Middle East
Authors: Al-Ansari A. , Yadav K. , Anderson D. , Leaper R. , Dye W. , Hansen N. 
Published: December 2007

Abstract
A high performance water based mud (HPWBM) system has been used successfully to address a combination of drilling challenges faced in the Middle East. Drilling problems encountered in the area typically include shale instability through pressure transmission effects, swelling clay-stone, bit balling, drill-string accretion, differential sticking over tight gas permeable sands and down-hole losses.
All these challenges can be very difficult to overcome with conventional water based mud (WBM) systems and can prove very expensive in terms of lost mud, lost down-hole tools, non performance rig time, side-tracks or ultimate failure to meet well or section objectives.
The HPWBM system was introduced to provide considerable improvement in WBM performance and also provide an environmentally benign alternative to oil based muds (OBM) while emulating OBM drilling performance attributes. Recent applications in the Middle East have proved that the HPWBM system can be applied as an alternative to OBM, successfully achieving the objectives of the sections while providing drilling performance comparative to OBM.
This paper discusses the technical features of the HPWBM system, gives an outline of previous applications and presents detailed case histories of the more diverse applications of the system and its components in wells in the Middle East, while comparing performance to offsets drilled with conventional WBM and OBM.
An Alternate Approach: Utilizing New PDC Technology for Drilling Deep LNG Wells Delivers Significant Savings for Major Operator in Oman
Authors: Teasdale P. , Riley N. , Mackinnon P. 
Published: December 2007

Abstract
A major operator has been drilling deep liquefied natural gas (LNG) wells for several years in central Oman. These wells are typically drilled vertically, featuring a complex geological sequence, that provides a significant challenge to bit performance.
Historically these wells have been drilled in 90 days with Tungsten Carbide Insert (TCI) bits on packed rotary assemblies down to the 9 5/8" casing shoe and Impregnated bits on turbine assemblies with occasional TCI runs in the 8 3/8" section.
A detailed study of the LNG wells focused on drilling performance in each of the three hole sizes in a typical well profile. The findings suggested that the introduction of new PDC technology was viable over much of the intervals and that significant savings in terms of time and cost could be achieved.
This paper reviews the findings of the study subsequent recommendations and the application of advanced PDC technology and stable PDC bit designs. The resulting improved performance is demonstrated by examples shown from two separate fields in central Oman where significant savings were achieved in terms of both rig time and cost per meter.
The collaboration between the Operator, rig contractor, bit vendor and other service companies was necessary to provide the platform for a successful operation.
Next Generation Parallel Computing for Large-Scale Reservoir Simulation
Authors: Fjerstad P. A. , Sikandar A. S. , Cao H. , Liu J. , Da Sie W. 
Published: December 2007

Abstract
This paper describes application of Project INTERSECT, a next generation highly scalable reservoir simulator on real large scale field models. High resolution reservoir simulation is required to better define and describe fluid flow and enable improved field development and tactical operational planning. Massively parallel computing techniques overcome limitations of problem size and space resolution. This paper demonstrates that large-scale simulation models can be performed on commodity hardware taking advantage of evolution in multicpu hardware architecture and software engineering. This allows both geologists and reservoir engineers to include more realistic geologic and engineering detail for better and more reliable production optimization.
Intense computer simulation is essential for effective reservoir management. The advances in reservoir characterization techniques and the industry drive towards the ‘smart oilfield’ with rapid model updates will require more efficient model processing to achieve timely field operational decisions. Parallel reservoir simulators have the potential to solve larger, more realistic problems than previously possible. The size and application of reservoir simulation problems have been limited by the availability of computing hardware, reservoir simulation architecture and of solution methods for solving large-scale heterogeneous problems. The next generation reservoir simulator demonstrates that key modeling challenges has been overcome by a software architecture and capability to model more realistic subsurface and surface models.
Applications of the new reservoir simulator illustrates how typical reservoir engineering options such as local grid refinement, local grid coarsening, multilateral wells and aquifer modeling affect the overall parallel performance and scalability using highly heterogeneous large-scale models. Application of new modeling techniques highlight increased accuracy of modeling results and more reliable field development planning and reservoir management decisions.
Dynamic Underbalanced Perforating System Increases Productivity and Reduces Cost in East Kalimantan Gas Field: A Case Study
Authors: Minto D. , Falxa P. , Manalu D. , Simatupang M. , Behrmann L. A. , Kusumadjaja A. 
Published: December 2007

Abstract
New gas wells at Tunu field in East Kalimantan are normally perforated using the extreme underbalanced (EUB) technique, in which a large static pressure differential between the wellbore and formation, or initial underbalance, is set before the gun is fired. This requires an operation to unload wellbore liquid, a wireline operation to set an anchoring tool, and several slickline operations to run and retrieve the gun string. The required degree of underbalance depends primarily on rock properties such as permeability, porosity, and strength.
A new approach produces a well dynamic underbalance (the transient underbalance just after creating the perforation cavity). By basing the job design on the properties of the reservoir, wellbore, and gun string, the technique consistently minimizes perforation damage and thus maximizes productivity. This technique is based on recent single-shot perforating experiments that show that it is the maximum dynamic underbalance—not the initial underbalance—that governs perforation cleanup. The wellbore pressure was found to vary considerably during the first half-second after the charges were detonated. This variation in wellbore pressure can be manipulated to give a large dynamic underbalance.
Perforating with the new technique and electric wireline was performed on 10 wells in the field. Software that considered wellbore geometry, fluid, gun-string selection, and reservoir properties was used to design a specific gun-string configuration and to predict the productivity increase contributed by the underbalance. The jobs were performed smoothly with significant cost savings compared to conventional EUB operations and yielded an increased productivity. Details of the perforating jobs with the new technique will be described, including a cost reduction of approximately 40% and a significant production increase. Testing revealed an average skin value for four wells of −0.29, versus the average skin of 4.73 from 35 conventional EUB perforating jobs executed during the multi-year interval from 2000 to 2004.
Kuwait Oil Company Sets Drilling Record Completing the Zubair Section in One Run
Authors: Al-Saeedi M. J. , Al-Mutairi B. , Al-Ajmi H. S. , Sharma M. , Swadi M. , Tyagi S. 
Published: December 2007

Abstract
Drilling deep exploratory wells in Kuwait presents a number of distinctive challenges. The 16" hole section is particularly demanding because it must be drilled through hard interbedded formations including the Zubair sandstone, Ratawi shale, Ratawi limestone, Minagish limestone/dolomitic limestone, Makhul limestone/shale and Hith anhydrite.1
Historically, 16" roller cone bits were used to drill the float equipment and several hundred feet of Zubair in order to get the stabilizers out of the casing. Several such wells have been drilled in North Kuwait with the best case requiring three PDC bits to complete the section subsequent to the roller cone run. The main challenge has been the highly abrasive Zubair formation with UCS in the 12,000–15,000 psi range.
Traditionally, drilling abrasive formations with PDC has been challenging even in smaller hole sizes (8-1/2" etc).2 However, as hole size increases torque response is magnified increasing vibration issues. In this application, vibration is further amplified by variations in formation hardness. These factors make efficiently drilling the Zubair with PDC a serious challenge. The operator required new PDC bit and cutter technology.
A team was assembled that analyzed PDC technology using numerical models, laboratory and field tests. Engineers focused on the bit frame/cutting structure, and cutter design. Cutters diamond table properties were evaluated in an effort to increase durability and wear resistance. The result is a tougher, more abrasion-resistant cutter capable of maintaining an efficient edge in the hard/abrasive Zubair sand.
Patented depth-of-cut control (DOCC) technology provided smoother, more stable drilling through the interbedded formations. By limiting the unnecessary depth-of-cut of PDC cutters, the amount of torque generated can be effectively controlled. Penetration is managed by adjusting cutter exposure from the bit body and providing a load-bearing surface. Laboratory testing proved how DOCC technology maintains bit aggressiveness needed and limits reactive torque as more weight is applied or as softer formations are encountered. The threshold for bearing engagement is precisely adjusted for each application. This minimized vibration when transitioning between formations while optimizing the ROP advantage of a PDC bit.
Utilizing the new bit design, the operator drilled the entire Zubair 16" interval in a single run for the first time and was able to cut drilling costs by eliminating several trips for new bits and the up-front expense of the extra downhole tools. The authors will discuss how the new technology cut costs and increased drilling efficiencies.
Subsurface Buoy Configuration for Rigid Risers in Ultradeep Water
Authors: Franciss R. 
Published: December 2007

Abstract
The Exploration and Production Department of Petrobras asked the R&D Center the development of a production system for 1800 m water depth, in Campos Basin, which would allow the installation of Steel Caterany Risers (SCR) in the starboard side of a production platform. The subsurface buoy concept was chosen as one of the alternatives. This concept has being developed since the preliminary studies conducted in the first phase of JIP Deepstar.
This concept has an advantage of uncoupling the movements of the platform from the risers, reducing the loads due to the risers in the platform and allowing the installation of this system before the installation of the production vessel, anticipating the production of the field.
This article shows the main characteristics of the buoy, its sizes, results of structural analyses and installation procedures for a buoy which sustains 14 SCR and 5 umbilicals in one side and 14 flexible jumpers and the same 5 umblicals in the opposite side.
This concept was tested in two model test tanks, where it was verified that this concept is feasible. Also, information related to a field trial with a prototype installed in Brazilian waters will be presented.
Technological Challenges for the Development of Ultradeep Water Fields
Authors: Saliés J. B. 
Published: December 2007

Abstract
The paper will present the main drives that PETROBRAS has to overcome the challenge of producing in water depth up to 3000m. It presents also the PROCAP-3000, the in-house Technological Program on Ultra-Deepwater Exploitation System, and its main projects developed to be able to achieve the goals. The paper presents in adition the major challenges in the following areas: anchoring, drilling equipment, risers, boosting, and subsea equipment. The main projects of each area will be discussed, the main results presented and the challenges pointed. Petrobras technical staff believes that the above technical areas and the chosen projects, to be presented, play a key-hole in ultra-deepwater production, not only in Brazil, but also all over the word in deepwater developments.