bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reservoir Management for Fields Sharing Common Aquifer: A Case Study from North African Sandstone Reservoirs El-Sharara Fields A, H and M NC-115, Libya
Authors: Mohammed K. , Elbekshi A. , Ghnia S. , Al_lottai O. , Naas A. , Izaguirre G. L. E. , Fanjul J. P. , Grinberg M. , Mustieles F. J. , Montes G. 
Published: December 2007

Abstract
The El Sharara A, H and M fields lie in the centre and eastern part of Block NC-115, some 50 km west of the town of Ubari in SW Libya (Figure 1). The producing reservoirs are Ordovician Mamuniyat and Hawaz formations. Those fields form a 3-way dip structure with a fault closure to the east against the Tanezzuft shale.
The Mamuniyat sequences are the main reservoir in the A, M, West-H and North H-Fields. This reservoir is characterised by coarsening up-ward parasequences consisting of fine, medium to coarse-grained sandstones. The East-H field is producing from Hawaz reservoir. This reservoir comprises fine to medium grained, locally argillaceous sandstones.
The main drive mechanism is weak water drive. Initially, the oil is highly undersaturated. Moreover, the oil has high API and low GOR.
The fields have been on production since late 1996, and are produced through facilities shared with other fields in the area. The four producing reservoirs are the Mamuniyat A-Field, Mamuniyat M-Field, Mamuniyat H-West, and the Hawaz H- East. A total of 71 wells have been drilled in the producing area (Figure 2).
Before the H and M field came on stream a decline in pressure was observed while producing only from A-Field.
The main objectives of this study is a broad understanding of the nature of the intercommunication of those fields through an integrated regional reservoir engineering study and consequently optimize the field development and depletion plans.
This paper sets a framework for an integrated reservoir study and also demonstrates the benefits of a regional study to optimize the reservoir performance by considering the global approach instead of treating each field individually.
The El-Sharara fields are under a pressure maintenance project using water injection to support the weak natural drive. This study has set the guidelines for optimizing the water injection rates and areal distribution through understanding the strength of the aquifer and estimating the energy needed to arrest the decline in pressure of these reservoirs.
An Assessment of Seabed Impacts of Synthetic-Based Drilling-Mud Cuttings in the Gulf of Mexico
Authors: Neff J. M. , Hart A. D. , Ray J. P. , Limia J. M. , Purcell T. W. 
Published: December 2007

Abstract
The Gulf of Mexico Comprehensive Synthetic Based Muds Monitoring Program used a combination of physical, chemical, and biological measurements to survey fourteen drill sites on the continental shelf and continental slope of the Gulf of Mexico where cuttings generated during drilling with synthetic based drilling muds (SBM) had been discharged. The three continental shelf and three continental slope sites selected for more intensive investigation are the focus of this paper. The objective of the program was to document the distribution of cuttings in drill site sediments and to characterize the areal and temporal extent of chemical and biological changes due to cuttings discharges. None of the drill sites had large cuttings piles such as have been observed in the North Sea. Chemical and physical measurements in sediments collected during two surveys one year apart at a subset of eight of the drill sites showed that deposition of discharged SBM cuttings solids was limited to a radius of less than about 250 m from the discharge location. Mean synthetic based fluid chemical (SBF) concentrations in near-field sediments decreased during the year between sampling surveys. Benthic ecology parameters were measured at the three continental shelf discharge sites and sediment toxicity to amphipods was measured at the three continental shelf and three continental slope discharge sites. The benthic community within 250 m of the site with the highest SBF concentrations in sediments had reduced benthic faunal abundance and diversity. Benthic communities were only slightly disturbed at the other two sites. Amphipod survival exceeded 75% in sediments collected within 250 m of most of the drill sites on the continental shelf and slope, indicating that most SBM cuttings-contaminated sediments, even those close to the drill sites, were not toxic. A sediment quality triad (SQT) analysis, used to characterize the impacts of drilling discharges on sediment quality at the three continental shelf sites, identified a gradient of decreasing disturbance with distance in sediments collected within 250 m of the drill sites compared to sediments &gt; 3000 m away. There was strong evidence that chemical and ecological recovery of sediments near SBM cuttings discharges was progressing during the year between the sampling surveys.
An Effective Hydrajet-Fracturing Implementation Using Coiled Tubing and Annular Stimulation Fluid Delivery
Authors: Surjaatmadja J. B. , East L. E. , Luna J. B. , Hernandez J. O. E. 
Published: December 2007

Abstract
The use of coiled tubing (CT) in fracturing was uncommon until a few years ago. Its applications have usually been limited to small jobs, and in reality, CT stimulation treatments have often been limited to acid placement treatments. With the inception of hydrajet fracturing technology, the use of CT has become more popular. Historically, CT fracturing methods were limited to placement of small fractures in the formation, and in some acidizing situations, near-wellbore damage-bypass methods.
CT technology has progressed until now it is used to place large fractures, some reaching over 600-ft half-lengths. Obviously, in most formations, such fracture sizes would not be possible with fluid delivery originating from the CT alone, so the use of the annulus to deliver the primary fracturing fluid becomes vital. This paper discusses the knowledge gained from recent field applications that have used this new annular path hydrajet-fracturing technology. Unique features of this technology are presented. Added benefits, such as the ability to deliver large proppant volumes, will be a focal point of this paper.
Case studies involving placement of multi-fracture treatments in three wells treated with this procedure will be discussed. Production improvements experienced in these wells will also be presented.
A Framework for Uncertainty Quantification and Technical-to-Business Integration for Improved Investment Decision-Making
Authors: Bos C. F. M. 
Published: December 2007

AbstractTo support the E&P investment decision-making process we use computer models extensively. This paper discusses in a conceptual way the potential merits of moving much more than what is currently being practised into the direction of "fully probabilistic" and "fully holistic" modeling, initially at the cost of model precision. In our opinion, the currently prevailing paradigm of maximum model precision (i.e. more physics, more grid blocks, more detail) may severely limit the optimization of the E&P decision-making process. Evidence for this statement is obtained when analyzing why the average of production and cashflow forecasts generally fails to coincide with the truth, as revealed in time: high-precision models on average result in biased forecasts and, hence, often lead to sub-optimal decisions or missed opportunities.To explain our approach, we introduce two postulates, discuss three modeling dimensions and link this to the business process of decision-making. The first postulate, when modeling the E&P value chain for investment decision-making, is that all uncertainties having a potential material effect on the model outcomes must be quantified within a comprehensive, internally consistent framework, and be taken into account when making E&P investment decisions. The second postulate is that, when trading-off the degree of "model precision" vs. the degree of uncertainty modeling and/or the degree of holistic value chain modeling, the latter two are more important than the former, especially when uncertainties are large. Initially therefore, reduced-physics or "approximate" models may be used, enabling a more comprehensive decision analysis. After having thus optimized the decisions, the sensivity (or "robustness") of the optimal decision to model precision should be tested. Multi-tiered decision-making, real options and an extended definition of "value" are also discussed within the framework's context.
Probabilistic Discharge Forecasting For Improved Asset Investment Decision Support
Authors: Jannink J. W. , Bos C. F. M. 
Published: December 2007

AbstractIn this paper we present a new way of integrating discharge forecast uncertainties in asset investment decision-making. The approach can be useful in the face of uncertainties with respect to future government regulations and in the face of uncertainties in the environmental implications of a given development. We present a hypothetical case study on how an oil company could optimize its investment decision-making by comprehensively risking the various regulatory scenarios and combining these with capex and opex items of mitigating measures on the one hand, and financial penalties for exceeding certain tolerance limits on the other hand. Decision trees are used as decision-making framework. The proposed methodology is fully probabilistic in the sense that it models both discrete uncertainties (scenarios, or possible events beyond one's control) and continuous uncertainties (i.e. probability density functions of uncertain input parameters). The Monte-Carlo sampling process generates a statistical population for the production, discharge and cash flow time-series curves, and ascertains that the full information is propagated to each investment alternative at the decision nodes of the tree. For each alternative decision, the risk of exceeding discharge tolerance limits is directly calculated and translated into the financial risk of having to pay a levy.The results of the simulated decision process with two types of financial government instruments indicate that probabilistic discharge forecasting can support both governments and asset managers. Governments can quantify prior to roll-out the chance that a certain policy will have the desired impact. Asset managers can use probabilistic emissions forecasting to optimize the asset's value by improving their decisions on mitigation facilities and operational policy. The hypothetical case study, assuming realistic developments in regulatory measures, indicates that an asset manager with an assignment to optimize net present value, will choose not to make any upfront investments in discharge mitigation facilities, resulting in less potential for future environmental protection. As a result of discounting, the long-term benefits do not sufficiently compensate the early investment.
K12-B A Test Site for Co2 Storage and Enhanced Gas Recovery
Authors: van der Meer L. G. H. , Kreft E. , Geel C. , Hartman J. 
Published: December 2007

Abstract
As part of the Dutch Climate Policy on the implementation of the Kyoto protocol, the Netherlands government is currently investigating to what extent CO2 sequestration in the deep subsurface could help reduce CO2 emissions. On 7 February 2002 the Dutch Minister of Economic Affairs introduced a new policy to promote feasibility studies into CO2 storage in the subsurface (The CRUST program).
Gaz de France Production Netherlands B.V. (GPN) is currently producing natural gas from the Dutch North Sea continental shelf. As one of the players in the Dutch gas supply market, GPN supports the idea of injecting CO2 into depleted gas fields in order to reduce CO2 emissions into the atmosphere.
The gas produced at one of GPN's platforms, the K12-B platform, contains a relatively high proportion of CO2. This CO2 is at present separated from the produced natural gas and released into the atmosphere. Preliminary assessment shows that it may be relatively easy to re-inject this CO2 into the Rotliegend gas reservoir. The reservoir is located at a depth of some 3800 meters; with a hydrostatic pressure regime and a formation temperature of 132 °C. Hence GPN's K12-B platform offers a good opportunity to study the technical conditions of CO2 injection at greater depths including the behavior of the gas reservoir itself. Developing the CO2- injection demonstration facility at the K12-B platform will increase our understanding of the benefits and drawbacks of this technique.
This paper reports on the results of the phase 1 and 2 studies of the ORC project - Offshore Re-injection of CO2. Phase 1 included a desk feasibility study into the possibility of underground CO2 injection at the K12-B platform. Phase 2 comprises of actual demonstration of the concept of underground storage. Some results of the early CO2 injection tests ar1 reported.
Quantifying Bypassed Oil in the Vicinity of Discontinuous Shales during Gravity Dominated Flow
Authors: Muggeridge A. H. , Jackson M. D. , Agbehi O. , Al-Shuraiqi H. , Grattoni C. A. 
Published: December 2007

Abstract
Gravity-stable, miscible gas injection is a common oil recovery technique throughout the world. In homogeneous environments recovery efficiencies may be more than 90%. However the influence of heterogeneity on the sweep efficiency in these recovery schemes is not well understood. For example most clastic reservoirs contain ‘discontinuous’ shales that cannot be correlated between wells. Several numerical studies have suggested that these may cause significant bypassing of oil during waterflooding or gas injection. However flow experiments and detailed simulation of viscous dominated displacements, without gravity, indicate that very little oil is bypassed1.
In this paper, we investigate flow patterns around discontinuous shales during vertical, gravity-influenced miscible gas injection in well-characterised bead-pack experiments at three flow-rates corresponding to unstable, partly stable and completely stable flow regimes. We examine the volume of oil bypassed and whether viscous fingering is reduced by gravity or altered by the presence of a discontinuous shale. The results are compared to the predictions of detailed simulation. We find that, during miscible displacements, an isolated shale causes negligible bypassing. However, during adverse mobility ratio displacements, the simulation program erroneously predicts significant bypassing of oil both upstream and downstream of the shale at high and intermediate flow-rates.
The Effect of Cross-Bedding Laminations on the Efficiency of Gas/Oil Multi-Contact Miscible Displacements
Authors: Al-Wahaibi Y. M. , Muggeridge A. H. , Grattoni C. A. 
Published: December 2007

Abstract
Many oil fields produce from fluvial sands where cross bedding lamination is one of the most common type of small-scale heterogeneity. To our knowledge, there are no published studies on the effects of cross-bedding laminations on multi-contact miscible (MCM) displacement processes and how they might alter the development of miscibility during oil recovery by gas displacement. This work aims to remedy this deficiency. A particular objective was to quantify the accuracy of compositional simulation when modelling sub-miscible displacements in these systems.
A series of well-characterized laboratory experiments in a two-dimensional, cross-bedded beadpack were carried out. A two-phase three-component (IPA/water/cyclohexene) liquid system, that exhibits an upper critical point at ambient conditions, was used as the fluid model. First contact miscible (FCM), immiscible and MCM displacement experiments were performed in the model laminated media. They were then simulated using a commercial compositional simulator with a single set of EOS parameters and without using history matching (the relative permeabilities as a function of IFT were obtained independently from displacement experiments in homogeneous packs).
The produced oil and gas in the experiments were found not to be in compositional equilibrium. This was observed both in homogeneous and heterogeneous packs. As a result the oil recoveries and gas cut predicted by compositional simulation for MCM displacements in laminated media differed significantly from the experimental results, although an excellent match was obtained for the FCM and immiscible displacements. The use of alpha factors, derived from MCM experiments in a homogeneous pack gave a much-improved prediction of experimental results for both condensing and vaporizing gas drives in both homogeneous and cross-bedded porous media.
Successful Peripheral Miscible Gas Injection in RKF Field, Berkine Basin, Algeria – Field Case History
Authors: Cubillos H. , Stright D. , Navarro J. M. 
Published: December 2007

AbstractThe paper discusses the discovery, development, and operation of a miscible gas cycling project in a highly undersaturated, volatile oil TAGI reservoir in center of the Berkine Basin, Algeria. Miscible gas injection was initially considered to be high risk and marginally economic; however, with a flexible development plan and careful reservoir management carried out by an integrated team of surface and subsurface disciplines, a successful project was implemented.In RKF field, a significant portion of the oil-in-place is in the oil-water transition zone, permeability is low, clay content is high, the oil contains asphaltenes, the formation water is salt-saturated, and the fluvial stratigraphy is complex. Design of a successful gas injection project was particularly challenging under these conditions.The RKF project demonstrates the importance of acquiring dynamic data early in the appraisal phase tracers and extensive data acquisition was critical to project optimisation and for solving operational `problems such as salt and asphaltene precipitation, minimisation of downtime, maximising liquid recoveries, and balancing of reservoir pressure throughout the field. Integrating all surface and subsurface engineering data, on a continuous basis, with the evolving geological and geophysical interpretations was critical to project success.
A Semi-Analytical Model for Productivity Testing of Multiple Wells
Authors: Fokker P. A. , Brouwer G. K. , Verga F. , Ferrero D. 
Published: December 2007

Abstract
This paper presents a new, semi-analytical method for calculation of the productivity of vertical, horizontal or multilateral wells draining either gas or oil reservoirs. Well interference effects and the presence of natural or induced fractures are accounted for.
The method is based on an earlier derived productivity prediction tool in which now moving pressure boundaries have been implemented to account for time dependence. The semi-steady-state pressure equations are solved using combinations of exact solutions around the well in an infinite reservoir and additional solutions to the Laplace equation are introduced to approximate the boundary conditions. The pressures and rates for all the flowing wells are solved in a single step for each required value of the time. Both numerical and analytical approaches have been used to validate the new method. The validity of the moving-boundary approach for the transient well behaviour has been checked against analytical results, whereas a numerical method has been employed to analyse the multi-well response in homogeneous, isotropic reservoirs.
Finally, the new method has been applied to real production test data. Both single-well and multi-well production tests performed in different types of reservoirs have been analysed with satisfactory results.
Drilling With Success: BHA Optimization for Coiled-Tubing Drilling in Harsh Environment
Authors: Maehs J. , Law A. , Pruitt R. , Weihe A. , Kiesl C. 
Published: December 2007

Abstract
Today's drilling environments require a CTD bottom hole assembly (BHA) be designed to perform in harsh environment. These include drilling in Underbalanced conditions (UB), challenging formations and high temperatures. This paper details findings from Coiled Tubing Drilling (CTD) operations in Alaska, Algeria and Sharjah.
These challenging operations required a complex CTD BHA that should be capable of withstanding temperatures in excess of 150°C (300° F), severe vibrations, over-speeding of motors, high-performance positive displacement motors (PDM's), nitrogen intrusion in BHA and PDM elastomer as well as many other challenges.
As a result, the CTD BHA was engineered to meet these various challenges. For example, in order to reduce (or better manage) BHA dynamics under extreme vibration levels, a multi-axis vibration sensor was used to optimize the BHA with weight and flexible bars. This permitted the driller to monitor vibration levels in real-time and adjust drilling procedures and parameters (WOB, mud flow, use of circulating sub, etc.) to reduce excessive vibrations. The BHA also had to address telemetry issues and, on the Sharjah nitrogen-drilled wells, an E-line CTD BHA was employed as it was the only way to transmit MWD/LWD data in the multiphase mud flow.
The paper will also describe some of the special BHA features like multi-cycle circulating sub use, ECD/pressure management, high-speed motor use and more. And the results of these efforts will be documented with performance and vibration graph comparison.
In the previous two years, drilling processes on the Sharjah and Alaska wells were significantly improved for increased footage per day and lower overall well costs. As a result, these projects have been recognized as economic successes and the findings from these wells can be applied to optimize the drill string and drilling parameters for enhanced performance in other challenging environments.
Large Diameter Coiled Tubing Becomes Available Safely Offshore Through a Newly Developed Spoolable Connector: Case Histories and Field Implementation
Authors: Link L. , Laun L. , Nesvik K. T. , Boge H. 
Published: December 2007

Abstract
Coiled Tubing operations in the North Sea are regularly challenged by crane lift capacity limitations when attempting to bring coiled tubing reels onboard. Very often the crane capacity or weather conditions determine the CT size to be used for the application, leading to operations conducted with less then the optimum CT size. The Norwegian sector generally has larger capacity cranes but most operations regularly involve the use of large OD coiled tubing (2.375" or 2.875"). The lengths required can cause logistical problems due to the lifting weights of the CT reels used. Current methods utilised for keeping weights as low as possible involve using so called split reel systems and thin-walled high strength parallel CT strings (i.e. constant wall thickness). While these weight reducing measures have proven themselves for many years now in the Norwegian sector, they can not resolve equipment weight issues in all cases. The joining of 2 or more separate strings together offshore by installing butt welds has been standard practice in the UK sector for many years now, mainly involving CT sizes of up to 1.75". In the Norwegian sector, butt-weld failures have occurred when using larger CT sizes and operators have been seeking a viable option to butt-welding, especially for larger OD CT.
In response to a direct request by the BJ Services North Sea operations departments, BJ Services Coiled Tubing Research & Engineering group in Calgary, Canada have developed and commercialised a LCF (Low Cycle Fatigue) Spoolable Connector to replace offshore butt-welding and resolve weight issues associated with heavy CT reels.