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The tendency to identify leaking zones is essential tool in trap assessment. Faults play an important role in creation of hydrocarbon traps. For volumetric analysis of a field to be meaningful, it is essential to analyze the faults contributing to the accumulation of hydrocarbons in a trap. These faults may be sealing or act as conduit to fluid flow. Analysis of trap is therefore carried out with the aim to reduce the uncertainties associated with hydrocarbon exploration and exploitation in Niger-Delta using "Covenant" field as a case study. The aim of the study is achieved using three dimensional seismic and well log data. Three reservoirs were mapped on the field while the fault supporting the identified trap was analyzed via throw, shale volume, shale gouge ratio, and hydrocarbon column heights attributes. The volume of shale model shows the presence of shale and sandstone formations in the fault plane. The fault-horizon's intersection (throw) model reveals that the horizons were not too deviated from where the maximum fault's displacement was noticed. The estimated shale gouge ratio of the fault on the analyzed trap reveals that the shallow sand horizon is supported by moderate sealing plane while that of mid and deep sand horizons are supported by proper sealing fault plane. The hydrocarbon column height model reveals a column height of 120m supports the shallow sand horizon while column heights È 180m support the mid and deep sand horizons respectively. It was inferred that despite the three horizons are supported by sealing fault zone, leakage still occurs at shallow sand horizon which correspond to a moderately sealed plane from SGR. [ABSTRACT FROM AUTHOR]

Hydrocarbon reservoir pressure depletion leads to stress changes inside the reservoir and ground deformation which is registered at the surface as subsidence. As reservoirs are often overlain by layers of rocksalt (or other evaporites), which are materials that flow so as to relax stresses inside them, there is the potential for time-varying surface subsidence. This work focuses on understanding the macroscopic mechanisms that lead to rocksalt flow-induced ground displacements. A Finite Element Model is used for this purpose in which the rocksalt layer is represented by a viscoelastic Maxwell material. Two distinct mechanisms that lead to displacement are observed. These are active during different stages of the deformation and have different timescales associated with them. An important observation is that the timescale for deformation that is measured at the ground surface is not equal to the timescale for deformation of a viscoelastic material element, but can be many times larger than that. The sensitivity of the response to the thickness and location of the rocksalt layer is also presented. Conclusions are drawn which allow for the relative importance of the presence of the rocksalt layer to be assessed and for a framework for understanding time-dependent subsidence above producing hydrocarbon reservoirs to be developed. Finally the changes in stress distribution around a producing reservoir are also briefly discussed. [ABSTRACT FROM AUTHOR]

In hydrocarbon reservoirs, fluid types can often vary from dry gas to volatile oil in the same column. Because of varying and unknown invasion patterns and inexact clay-volume estimations, fluid-types differentiation on the basis of conventional logs is not always conclusive. A case study is presented by use of advanced nuclear-magnetic-resonance (NMR) techniques in conjunction with advanced downhole-fluid-analysis (DFA) measurements and focused sampling from wireline formation testers (WFTs) to accurately assess the hydrocarbon-type variations. The saturation-profiling data from an NMR diffusion-based tool provides fluid-typing information in a continuous depth log. This approach can be limited by invasion. On the other hand, formation testers allow taking in-situ measurements of the virgin fluids beyond the invaded zone, but at discrete depths only. Thus, the two measurements ideally complement each other. In this case study, NMR saturation profiling was acquired over a series of channelized reservoirs. There is a transition from a water zone to an oil zone, and then to a rich-gas reservoir, indicated by both the DFA and the NMR measurements. Above the rich gas, is a dry-gas interval that is conclusively in a separate compartment. Diffusion-based NMR identifies the fluid type in a series of thin reservoirs above this main section, in which no samples were taken. NMR and DFA both detect compositional gradients, invisible to conventional logs. The work presented in this paper demonstrates how the integration of measurements from various tools can lead to a better understanding of fluid types and distribution. [ABSTRACT FROM AUTHOR]

Rajahmundry Traps has been under geo-scientific investigations for over half a century; yet sketchy information is available on morphology and internal architecture of lavas. This study bridges this gap by describing the morphology of lava pile of Duddukuru area following Hawaiian scheme that relates a lava-type with a particular emplacement style. The lowest flow (Flow 1) at Duddukuru, overlying an infra-trappean bed is a thick pahoehoe sheet lobe with intermittent basal hummocky, P-type pahoehoe lobes representing slow, sub-aerial emplacement of lava parcels. Some of them also have cherty intercalations and morphology suggestive of possible interaction of lava with water or water-laden sediments. Hummocky lobes were over-ridden by subaerial emplacement of voluminous sheet lava, which developed multi-tier columnar joints probably due to inundation of lava-surface by water. Inter-trappean sediments were deposited above Flow 1 in the ensuing period of volcanic quiescence. The eruptive history of Duddukuru ended with sub-aerial outpouring of two consecutive a'a flows (Flows 2 and 3) separated by a thin red bole horizon. As pahoehoe lavas are known to travel long distances due to emplacement through thermally efficient mechanism of endogenous inflation and insulated melt transport whereas a'a lavas, in contrast, are cooling-limited flows which rarely attain lengths covered by pahoehoe lavas; it is probable that the pahoehoe and a'a flows of Duddukuru have not traveled comparable distances. A'a flows of Rajahmundry Traps traveling from far-off vents are, therefore, more unlikely despite temporal and chemical similarity of this lava-pile with upper parts of Western Deccan Basalt Group. [ABSTRACT FROM AUTHOR]

Abstract: The fold-and-thrust belt in the northwestern margin of the Junggar Basin is composed of the northern monocline belt, the middle syncline belt, the Ke-Wu thrust belt, and the frontal slope belt, and is divided into the upper and lower structural layers in vertical. The upper structural layer precedes the lower one in terms of thrust sequence. Inferred from the restoration of unconformities, the motion of thrust faults started in late Triassic, activated in succession in Jurassic, and stopped in Cretaceous. The footwall venture exploration should aim at “cap brim” traps, especially in the triangular region, where the Dazhuluogou tear fault and Ke-Wu thrust belt intersect and the exploration horizon imbeds moderately, and then aim at the deep anticline traps in duplex structures when obtaining the essential data of deep geology and the velocity data. [Copyright &y& Elsevier]

The area comprising the NE Nile Delta and adjacent northern Sinai is an important hydrocarbon province in Egypt, but the origin of the hydrocarbons and their migration is not fully understood. In this paper, we evaluate organic source facies and assess the results of basin modelling in order to improve our understanding of the regional petroleum system. Organic-geochemical and petrographic analyses of 800 rock samples ranging in age from Early Jurassic to Pleistocene were used in this study. Most of the samples studied had moderate to high TOC contents, and kerogen was a mixture of Types II and III with a wide range of petroleum generation potentials from very poor to very good. Thermal and burial history models indicate that the source rocks entered the early-mature/mature stage in very recent times (Pleistocene to Recent). The top of the oil window ranges in depth from 1,800 m to 4,500 m, whereas the bottom of the oil window was not reached by most of the studied wells. In combination with numerical modelling results, structure contour maps for key horizons reveal possible migration trends and prospective areas. We tentatively identify prospective targets for hydrocarbon exploration, both in the Tertiary sequence and in the Cretaceous succession, especially where carbonate build-ups are present. [ABSTRACT FROM AUTHOR]

We propose a decision-making approach for optimizing the profitability of hydrocarbon reservoirs. The proposed approach addresses the overwhelming complexity of the overall optimization problem by suggesting an oilfield operations hierarchy that entails different time scales. We discuss system identification, optimization, and control that are appropriate at various levels of the hierarchy and capitalize on the abilities of permanently instrumented and remotely actuated fields. Optimization is performed in real-time and is based on feedback. We provide details on real-time identification of hybrid models and their use at the scheduling and supervisory control levels. Case studies using field-calibrated simulation data demonstrate the applicability and value of the proposed approach. Directions for future development are given. [ABSTRACT FROM AUTHOR]

Abstract: This article introduces a methodology for integrating geochemical data in reservoir simulations to improve hydrocarbon reservoir models. The method exploits routine measurements of naturally existing inorganic ion concentration in hydrocarbon reservoir production wells, and uses the ions as non-partitioning water tracers. The methodology is demonstrated on a North Sea field case, using the field''s reservoir model, together with geochemical information (SO4 2−, Mg2+, K+, Ba2+, Sr2+, Ca2+ and Cl− concentrations) from the field''s producers. Based on the dataset, some of the ions are shown to behave almost as ideal seawater tracers, i.e. without sorption to the matrix, ion exchange with the matrix or scale formation with other ions in the formation water. Moreover, the dataset shows that ion concentrations in pure formation water vary according to formation. This information can be used to allocate produced water to specific water-producing zones in commingled production. Based on an evaluation of the available data, one inorganic component, SO4 2−, is used as a natural seawater tracer. Introducing SO4 2− as a natural tracer in a tracer simulation has revealed a potential for improvements of the reservoir model. By tracking the injected seawater it was possible to identify underestimated fault lengths in the reservoir model. The demonstration confirms that geochemical data are valuable additional information for reservoir characterization, and shows that integration of geochemical data into reservoir simulation procedures can improve reservoir simulation models. [Copyright &y& Elsevier]

Clastic reservoirs saturated with heavy oils have been observed to exhibit a marked relationship between velocity of propagation of acoustic waves and changes introduced by certain kinds of enhanced oil recovery procedures, including heating of the reservoir. This observation forms the basis for a method of monitoring the changes which occur in the reservoir when these enhanced oil recovery (EOR) procedures are used. New developments in diffraction tomographic imaging allow accurate, high-resolution images to be obtained in hydrocarbon reservoirs, clearly delineating the zones affected by these enhanced oil recovery procedures. When both compressional and shear wave data can be obtained, additional physical parameters such as Poissons ratio can be reconstructed. [ABSTRACT FROM AUTHOR]