Various xenoliths have been found in lavas of the 1763 ("La Montagnola"), 2001, and 2002-03 eruptions at Mt. Etna whose petrographic evidence and mineral chemistry exclude a mantle origin and clearly point to a cognate nature. Consequently, cognate xenoliths might represent a proxy to infer the nature of the high-velocity body (HVB) imaged beneath the volcano by seismic tomography. Petrography allows us to group the cognate xenoliths as follows: i) gabbros with amphibole and amphibole-bearing mela-gabbros, ii) olivine-bearing leuco-gabbros, iii) leuco-gabbros with amphibole, and iv) Plg-rich leuco gabbros. Geobarometry estimates the crystallization pressure of the cognate xenoliths between 1.9 and 4.1 kbar. The bulk density of the cognate xenoliths varies from 2.6 to 3.0 g/cm 3 . P wave velocities (V P ), calculated in relation to xenolith density, range from 4.9 to 6.1 km/s. The integration of mineralogical, compositional, geobarometric data, and density-dependent V P with recent literature data on 3D V P seismic tomography enabled us to formulate the first hypothesis about the nature of the HVB which, in the depth range of 3-13 km b.s.l., is likely made of intrusive gabbroic rocks. These are believed to have formed at the "solidification front", a marginal zone that encompasses a deep region (>5 km b.s.l.) of Mt. Etna's plumbing system, within which magma crystallization takes place. The intrusive rocks were afterwards fragmented and transported as cognate xenoliths by the volatile-rich and fast-ascending magmas of the 1763 "La Montagnola", 2001 and 2002-03 eruptions.
Karachaganak field is one of the largest accumulations of gas-condensate in the world. Located in the northern Pre-Caspian Basin (Kazakhstan), the field is a Permo-Carboniferous isolated carbonate platform with a hydrocarbon column of about 1500 m. In production since 1985, the actual development focuses the oil rim with gas injection implemented, since 2004, in a confined area of the Platform Interior. Various future development scenarios are now being considered to more fully develop the reservoir, and some of the recovery processes being modeled require an improved understanding of the internal reservoir architecture. In fact the internal reservoir architecture is rather complex, affected by the initial development of aggrading mounds followed by progradation (consisting most likely in a clinoform geometry) passing to cyclic, grain-dominated platform interior sediments. The resulting reservoir quality is quite heterogeneous with low porosity but locally high productivity when affected by micro-fractures and vugs. In this context a deep analysis has been performed considering the location of additional injection in different areas/regions of the field evaluating the possible risks and the uncertainties affecting the liquid recoveries. Nine different areas characterised by specific geological/dynamic behaviour have been investigated. Moreover considering the Prograding area, alternative models were built in order to address the possible impact of Clinoforms on the flow patterns. The final analysis, which takes into consideration the possible liquid recovery and the relevant knowledge and complexity of the different areas, provided an improved view to optimize the future injection. In fact, the Cyclic Platform, where injection has been already implemented, appears to be the best candidate; other areas, although affected by a certain degree of uncertainty, also seem promising from the recovery point of view, while some other regions, characterised by high compartmentalisation, appear to be less interesting.
Karachaganak Field is an isolated carbonate bank consisting of Carboniferous to Lower Permian carbonate deposits located in the northern margin of the Pre-Caspian Basin of Kazakhstan. Discovered in 1979, it represents one of the largest gas and condensate reservoirs in the world and has been in production since 1985. This paper focuses on the different modeling methods applied to Late Visean sequence to try to improve the reservoir model reliability. In fact although this interval is relatively thin, it is mostly located inside the Oil Rim interval, so that it strongly impacts the present development phase which is focused on maximizing liquid recovery. This peculiar stratigraphic interval represents the highstand section of the Late Visean sequence and records the initial settling of micro-biohermal deposits constituted by in situ bryozoans, microbial boundstone, cementstone, all facies interlayered with crinoidal limestones. Due to its reduced thickness, there is a minimal contribution of the seismic sequence stratigraphy interpretation to understand the internal structure and geometry of this sequence. Despite its complexity, the Late Visean was initially modeled as a unique "undifferentiated body" characterised by the whole petrophysical data without discriminating the different depositional facies. Now, thanks to new core and analogue data, there is enough information to attempt to model this stratigraphic interval with a more detailed approach, trying to both reconstruct the 3D Facies distribution and utilize the relevant Reservoir Properties. Therefore two additional simulation methods have been tested: Object-Based Modeling and Multiple-Point Statistics Facies Modeling. Thanks to the long historical production, all these alternative scenarios have been compared to the initial SGS approach using the HM as benchmark to evaluate the best methodology to be applied.
Karachaganak field, brought on stream in 1985, is one of the largest accumulations of gas-condensate in the world. Located in the northern Pre-Caspian Basin (Kazakhstan), the field is a Permo-Carboniferous isolated carbonate platform, with a hydrocarbon column of about 1500 m.The current development focuses the oil rim with gas injection in a confined area of the Platform Interior implemented since 2004. Among the future development scenarios under consideration, an increase of gas injection in different areas of the field was evaluated with the scope of maximizing liquid recovery and keeping the production plateau. The internal reservoir architecture is indeed very complex: an initial development of aggrading mounds is followed by prograding clinoforms passing to cyclic, grain-dominated platform interior sediments. The resulting reservoir quality is quite heterogeneous, with low porosity, but locally high productivity when affected by micro-fractures and vugs. The analysis was performed considering both incremental volumes of injected gas and the uncertainties affecting the reservoir to obtain a ranking which takes into account additional liquid recoveries and relevant risks. Eventually, the analysis led to a proxy function which, through a mean-variance optimization approach, was used to estimate the most favourable gas injection configurations, reaching the best compromise between recovery and uncertainty.In conclusion, the analysis highlighted pros and cons for each reservoir area, offering a better view to optimize the future development. The depositional region where the injection was already implemented appears to be a good candidate; other areas, although affected by a certain degree of uncertainty, are also promising from the recovery point of view, while some other regions, characterized by high compartmentalization, seem to be less interesting.
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