1,721,015 research outputs found
Constitutive rock equation in the Upper Adriatic basin from in situ compaction measurements, 1999 ASME Mechanics and Material Conference
No full textR.C. Batra and E.G. Henneke (eds), Virginia Tech. Press, Blacksburg, V
Under-relaxed iterations for coupled finite element solution to gas and water dynamics in depleted reservoirs
No full textCan gas withdrawal from Chioggia Mare field affect the stability of the Venetian littoral?
No full textResidual land subsidence over depleted gas fields in the Northern Adriatic basin, Environ. Eng. & Geosciences, V(4), 389-405, 1999.
No full textAn original nonlinear three-dimensional finite element model is developed to predict the residual land subsidence adjacent to depleted gas fields, as a delayed response from an active aquifer which may keep on compacting for a long time after the field abandonment. The pore pressure recovery within the reservoir and the depletion of the lateral/bottom aquifer are simulated by a subsurface flow model coupled with the equation of state of the residual gas repressurized by the ground water which floods the field. The resulting pore pressure distribution is used as input data in a pore-elastic structural model of land subsidence. The modeling approach is nonlinear because of both the dynamic coupling between the flux from the aquifer and the reservoir gas pressure response, and the dependence of the porous medium elastic properties on the effective intergranular stress and the loading/unloading conditions. The model is applied to the 3,000 m deep gas reservoir of Dosso degli Angeli, one of the major fields in the Northern Adriatic sedimentary basin, made of three major gas pools. Representative basin-scale mechanical parameters have been obtained from laboratory triaxial and oedometric tests, density logs, and recent measurements of in situ compaction by the use of radioactive markers. In 1992, at the end of 21 year production life the maximum pore pressure drawdown in the depleted pools approached 300 kg/cm(2). The largest land settlement from the modeling simulation turns out to be 31 cm, in good agreement with the available leveling records. Numerical predictions suggest that a residual land sinking of about 10 cm is yet to be expected in 2042, i.e., 50 years after the field abandonment, close to the areas of Porto Garibaldi and Casal Borsetti a few kilometers south and north of the field, respectively, namely between two and three times the subsidence experienced by those areas during the field development. Gas pressure recovery in 2042 ranges from 50 to 130 km/cm(2) according to gas pool, and with the cone of depression still expanding toward the far outer boundary of the adjacent aquifer
Statistical analysis of in situ compaction measurements for anthropogenic land subsidence prediction in the Northern Adriatic basin
No full textS.J. Lippard et al (eds), Tapir Press, Trondhei
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Anthropogenic Venice uplift by seawater pumping into a heterogeneous aquifer system
No full textIn recent years, a project of anthropogenic Venice uplift caused by seawater injection into a 600–850 m deep brackish aquifer underlying the lagoon has been advanced. While an extensive data set based on marker measurements from a number of gas‐producing wells of the northern Adriatic is available for a realistic evaluation of the geomechanical properties of the injected geologic formation, permeability data are very scarce and sparse throughout the area. Previous finite element (FE) predictions relying on a uniform hydraulic conductivity K as derived from pumping tests suggest that a flat uplift of the city is produced over 10 years from the inception of injection. However, it is well‐known and widely recognized that in natural porous media very seldom K exhibits an even spatial distribution. In this study, a random distribution is then assumed to address the influence of a variable K on the uniformity of the city uplift. To limit the otherwise prohibitive computational burden, the study is performed relative to the pilot project designed to raise a reduced area at the margin of the lagoon. Monte Carlo groundwater flow simulations are performed using a FE discretization of the injected aquifer system based upon a hydraulic conductivity distribution characterized by a lognormal, stationary random process. The resulting pore overpressure is then implemented into a deterministic FE geomechanical model. A sensitivity analysis is performed to account for the uncertainty on the stochastic process, reflected by both the log K variance s2 and the correlation length l over the ranges 0.2–1.0 and 20–1000 m, respectively, which are quite plausible for normally consolidated sedimentary formations such as the Northern Adriatic basin. The cumulative distribution function (CDF) of the ground surface uplift, uz, and its horizontal gradient, rz, are computed and used to evaluate the probability for rz to be larger than a few significant threshold values as discussed later. It is shown that, even within the most pessimistic scenario (i.e., s2 = 1.0 and l = 1000 m), the maximum rz is comparable, namely of the same order, with the one obtained from the deterministic case and (1) 2–3 times smaller than the rz caused in the city by groundwater withdrawal in the nearby industrial area over the 1960s (10 × 10−5), (2) 1 order of magnitude less than the maximum bound as indicated in the literature for the safety of multifloor masonry buildings (50 × 10−5), and (3) about 20 times smaller than the maximum rz values that the city is currently experiencing (100 × 10−5). The results highlight the strong effect exerted by the overburden in smoothing the uneven expansion of the injected heterogeneous formation
Land subsidence spreading factor in the Northern Adriatic gas fields, Italy
No full textThe land subsidence spreading factor provides a useful straightforward indication on how much of a gas/oil reservoir compaction induced by field development migrates to ground surface with a possible adverse impact on the stability of low-lying coastal areas. This factor depends primarily on the ratio between the depth of burial and a representative horizontal dimension of the reservoir. However, an important influence is also exerted by the active bottom/lateral aquifer hydraulically connected to the field (called “waterdrive” in reservoir engineering) that may undergo an extensive depressurization also after the field abandonment, thus contributing to enhance the overall land settlement. In the Northern Adriatic basin, Italy, is evaluated using a nonlinear finite element model of three representative gas reservoirs (Chioggia Mare, Dorotea, and Dosso degli Angeli) surrounded by important bottom/lateral aquifers in the interval depth between 1000 and 3300 m. Results show that may easily approach and even exceed one for the deepest field as well, contrary to the prediction of land subsidence based on the compaction of the gas-bearing formations alone, that can thus be largely underestimated
Arthroscopic rotator cuff repair by bony tunnels. A preliminary study
No full textThe classic open technique for rotator cuff repair is performed by passing non absorbable sutures in the tendon and through bony tunnels, tied on lateral surface of the greater tuberosity. This procedure has been performed at our institution by arthroscopic means employing the Acufex® guide for the T-fix® instrumentation and the Acufex® suture-punch with dedicated sutures. The technique is described in detail. From December 1998 to May 1999 eleven cases were treated with this technique as an alternative to the reinsertion with absorbable anchors. In the same period 53 reinsertions of the rotator cuff with anchors were performed. The two groups were compared. The mean follow-up was 13.6 months (range, 12 to 16 months). The average post-operative Constant score was 83 points (range, 65 to 97 points) for the patients which had trans-osseous sutures and 84 points (range, 63 to 95 points) for those treated with anchors. No statistical difference was observed between the two groups. No failure of the trans-osseous tunnels manifested. The only post-operative complication concerned a transitory stiffness of the shoulder presenting once in the first group and in four cases in the second group. Its cause was identified in a lack of passive motion in the early post-operative weeks. The proposed technique gave satisfactory early results, comparable to those achieved with the anchors technique. For these reasons the trans-osseous sutures technique revealed to be a valid alternative in arthroscopic surgery of the rotator cuff tears
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