186 research outputs found
Estimate of a spatially variable reservoir compressibility by assimilation of ground surface displacement data
Abstract.
Fluid extraction from producing hydrocarbon reservoirs can cause anthropogenic land subsidence. In
this work, a 3-D finite-element (FE) geomechanical model is used to predict the land surface displacements above
a gas field where displacement observations are available. An ensemble-based data assimilation (DA) algorithm
is implemented that incorporates these observations into the response of the FE geomechanical model, thus re-
ducing the uncertainty on the geomechanical parameters of the sedimentary basin embedding the reservoir. The
calibration focuses on the uniaxial vertical compressibility
c
M
, which is often the geomechanical parameter to
which the model response is most sensitive. The partition of the reservoir into blocks delimited by faults moti-
vates the assumption of a heterogeneous spatial distribution of
c
M
within the reservoir. A preliminary synthetic
test case is here used to evaluate the effectiveness of the DA algorithm in reducing the parameter uncertainty
associated with a heterogeneous
c
M
distribution. A significant improvement in matching the observed data is
obtained with respect to the case in which a homogeneous
c
M
is hypothesized. These preliminary results are
quite encouraging and call for the application of the procedure to real gas fields
Monitoring and Modeling Farmland Productivity Along the Venice Coastland, Italy
AbstractThe southern portion of the Venice coastland is a very precarious environment and salt contamination of land and groundwater is a severe problem that is seriously impacting the farmland productivity. Geophysical surveys, lab testing and continuous monitoring of hydrological parameters together with crop yield distribution were performed and acquired from 2010 to 2012 in a 21ha basin cultivated with maize crop and representative of the area. The dataset is here used to set-up a numerical model of soil moisture dynamics coupled with plant transpiration, photosynthesis and growth. The hydraulic model is linked to the atmosphere by the calculation of the stomatal conductance which is optimized for maximum carbon gain. The model is applied to the field site to understand the impact of land elevation, soil heterogeneities, and seawater contamination on land productivity
New scenarios in secondary hyperparathyroidism: etelcalcetide. Position paper of working group on CKD-MBD of the Italian Society of Nephrology
Bone mineral abnormalities (defined as Chronic Kidney Disease Mineral Bone Disorder; CKD-MBD) are prevalent and associated with a substantial risk burden and poor prognosis in CKD population. Several lines of evidence support the notion that a large proportion of patients receiving maintenance dialysis experience a suboptimal biochemical control of CKD-MBD. Although no study has ever demonstrated conclusively that CKD-MBD control is associated with improved survival, an expanding therapeutic armamentarium is available to correct bone mineral abnormalities. In this position paper of Lombardy Nephrologists, a summary of the state of art of CKD-MBD as well as a summary of the unmet clinical needs will be provided. Furthermore, this position paper will focus on the potential and drawbacks of a new injectable calcimimetic, etelcalcetide, a drug available in Italy since few months ago
New scenarios in secondary hyperparathyroidism: etelcalcetide. Position paper of working group on CKD-MBD of the Italian Society of Nephrology
Bone mineral abnormalities (defined as Chronic Kidney Disease Mineral Bone Disorder; CKD-MBD) are prevalent and associated with a substantial risk burden and poor prognosis in CKD population. Several lines of evidence support the notion that a large proportion of patients receiving maintenance dialysis experience a suboptimal biochemical control of CKD-MBD. Although no study has ever demonstrated conclusively that CKD-MBD control is associated with improved survival, an expanding therapeutic armamentarium is available to correct bone mineral abnormalities. In this position paper of Lombardy Nephrologists, a summary of the state of art of CKD-MBD as well as a summary of the unmet clinical needs will be provided. Furthermore, this position paper will focus on the potential and drawbacks of a new injectable calcimimetic, etelcalcetide, a drug available in Italy since few months ago
Delayed subsidence of the Dead Sea shore due to hydro-meteorological changes
Many studies show the sensitivity of our environment to manmade changes, especially the anthropogenic impact on atmospheric and hydrological processes. The effect on Solid Earth processes such as subsidence is less straightforward. Subsidence is usually slow and relates to the interplay of complex hydro-mechanical processes, thus making relations to atmospheric changes difficult to observe. In the Dead Sea (DS) region, however, climatic forcing is strong and over-use of fresh water is massive. An observation period of 3 years was thus sufficient to link the high evaporation (97 cm/year) and the subsequent drop of the Dead Sea lake level (− 110 cm/year), with high subsidence rates of the Earth’s surface (− 15 cm/year). Applying innovative Global Navigation Satellite System (GNSS) techniques, we are able to resolve this subsidence of the “Solid Earth” even on a monthly basis and show that it behaves synchronous to atmospheric and hydrological changes with a time lag of two months. We show that the amplitude and fluctuation period of ground deformation is related to poro-elastic hydro-mechanical soil response to lake level changes. This provides, to our knowledge, a first direct link between shore subsidence, lake-level drop and evaporation
On the importance of the heterogeneity assumption in the characterization of reservoir geomechanical properties
The geomechanical analysis of a highly compartmentalized reservoir is performed to simulate
the seafloor subsidence due to gas production. The available observations over the hydrocarbon
reservoir consist of bathymetric surveys carried out before and at the end of a 10-yr
production life. The main goal is the calibration of the reservoir compressibility cM, that is,
the main geomechanical parameter controlling the surface response. Two conceptual models
are considered: in one (i) cM varies only with the depth and the vertical effective stress
(heterogeneity due to lithostratigraphic variability); in another (ii) cM varies also in the horizontal
plane, that is, it is spatially distributed within the reservoir stratigraphic units. The latter
hypothesis accounts for a possible partitioning of the reservoir due to the presence of sealing
faults and thrusts that suggests the idea of a block heterogeneous system with the number of
reservoir blocks equal to the number of uncertain parameters. The method applied here relies
on an ensemble-based data assimilation (DA) algorithm (i.e. the ensemble smoother, ES),
which incorporates the information from the bathymetric measurements into the geomechanical
model response to infer and reduce the uncertainty of the parameter cM. The outcome from
conceptual model (i) indicates that DA is effective in reducing the cM uncertainty. However,
the maximum settlement still remains underestimated, while the areal extent of the subsidence
bowl is overestimated. We demonstrate that the selection of the heterogeneous conceptual
model (ii) allows to reproduce much better the observations thus removing a clear bias of
the model structure. DA allows significantly reducing the cM uncertainty in the five blocks
(out of the seven) characterized by large volume and large pressure decline. Conversely, the
assimilation of land displacements only partially constrains the prior cM uncertainty in the
reservoir blocks marginally contributing to the cumulative seafloor subsidence, that is, blocks
with low pressure
Período de inanição de noctuídeos-praga.
Com intuito de compreender como a estratégia de desseca antecipada com o uso de herbicidas pode desfavorecer a multiplicação desses lepidópteros supracitados, pela redução ou ausência de alimento, desenvolvemos o presente trabalho. Desta forma, o objetivo do estudo foi avaliar o período que S. frugiperda e H. armigera sobrevivem na ausência total de alimento
- …