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Fernandez-Ibanez F.,Geomechanics International Inc. | Perez-Pena J.V.,University of Granada | Azor A.,University of Granada | Soto J.I.,University of Granada | Azanon J.M.,University of Granada
Geology | Year: 2010

Fluvial piracy in the Guadix-Baza basin (southeast Spain) promoted erosion of a high volume of sediments during the late Quaternary, after the former internal drainage of this basin changed to external due to headward erosion by the Guadalquivir River. As a response to load release, this basin underwent uplift, which, in turn, enhanced fluvial incision and erosional processes. Differential erosion within the Guadix-Baza basin resulted in dissimilar isostatic rebound. We numerically model the lithospheric response to sediment unloading and show a total rising of 15 m in the Guadix subbasin compared to 2 m in the Baza subbasin. This differential uplift is likely to have been accommodated along the Baza normal fault, which has been active throughout the Quaternary. Modeling results suggest that ~13% of the total Quaternary fault throw directly arises from the differential isostatic readjustment between subbasins. This example is one of the first estimates of fault slip partitioning between tectonic and isostatic effects due to unloading driven by river incision. © 2010 Geological Society of America.

Soto J.I.,University of Granada | Fernandez-Ibanez F.,Geomechanics International Inc. | Talukder A.R.,CSIRO
Leading Edge | Year: 2012

This contribution is intended to show some of the most recent, eventually active, shale structures developed in the northwestern margin of the Alboran Sea in the western Mediterranean. Most marine geophysical data used for this study are from surveys conducted by ConocoPhillips in 2000 and 2001 in the Alboran Sea. This company explored the western sector of this basin, both in Spanish and Moroccan waters. It acquired a comprehensive data set, including a complete mosaic of sea-floor multibeam bathymetry with the associated sub-bottom high-resolution profiles, and a dense network of 2D multichannel seismic reflection profiles. These surveys provide a significant amount of new marine geophysical data, which increase the previous knowledge of the structure and characteristics of the westernmost Mediterranean region. © 2012 Society of Exploration Geophysicists.

Perdona P.,Pontifical Catholic University of Rio de Janeiro | Rabe C.,Geomechanics International Inc.
Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010 | Year: 2010

Steam Assisted Gravity Drainage (SAGD) is one of the technologies selected to economically increase the recovery factor from the very large accumulations of heavy oil found in the Orinoco Belt,Venezuela. This paper presents a geomechanical laboratory and field campaign to obtain the rock properties, estimate the in-situ stresses, and to evaluate the pore-pressure in a field located in the giant Orinoco Belt. This study was crucial to build the geomechanical model of the studied area. © 2010 Taylor & Francis Group.

Barton C.,Geomechanics International Inc. | Moos D.,Geomechanics International Inc.
AAPG Memoir | Year: 2010

A field-specific geomechanical model serves as a platform for dramatically reducing costs and increasing production over the life of a field. The information contained in a geomechanical model makes it possible to assess exploration risk associated with fault-seal breach caused by fault slip. Using model-specific stress, pore pressure, and rock properties information, drilling engineers can provide recommendations for efficient well design and placement to reduce adverse events such as stuck pipe and lost circulation. A geomechanical model also makes it possible to design completions to avoid or manage solids production and to extend the productive life of wells. In addition, the effects of reservoir depletion and injection can be predicted to enable optimal exploitation that avoids excessive reservoir damage, casing collapse, and hazards related to leakage of produced or injected fluids. The essential contribution of wellbore image technologies to these exploration and production challenges is illustrated through recent case studies that apply wellbore imaging technologies to the detection, access, and recovery of hydrocarbons. Future reservoir development and management practice will demand an increased use of imaging techniques to ensure successful production in risky drilling environments, reduce the costs associated with drilling, and increase the economic lifetime of mature reservoirs. Copyright © 2010 by The American Association of Petroleum Geologists.

Holland M.,RWTH Aachen | Holland M.,Geomechanics International Inc. | Urai J.L.,RWTH Aachen
Journal of Structural Geology | Year: 2010

We studied a special type of zebra carbonate in limestones of an overpressure cell exhumed from at 5. km depth, in outcrops on Jabal Shams, Oman Mountains. The rocks show anastomosing patterns of regularly spaced calcite veins in dark gray, fine-grained carbonate; microscopic observations reveal these as dense bundles of much finer veinlets, typically 10-50 μm thick. The vein bundles are up to 5. mm thick, they contain multiple sub-parallel arrays of host rock fragments embedded in the coarse-grained vein calcite. We interpret these structures as the result of numerous mechanically effective crack and reseal events together with strong growth competition or crystallization from sparse nucleation sites. Cementation produced mechanically strong veins so that new fractures were localized along the vein/rock interface or within the matrix itself. We present simple conceptional models relating the mechanical strength of the vein and the morphology of the resulting vein network. © 2009 Elsevier Ltd.

Trautwein-Bruns U.,RWTH Aachen | Schulze K.C.,Geomechanics International Inc. | Becker S.,RWTH Aachen | Kukla P.A.,RWTH Aachen | Urai J.L.,RWTH Aachen
Tectonophysics | Year: 2010

In 2004 the 2544. m deep RWTH-1 well was drilled in the city centre of Aachen to supply geothermal heat for the heating and cooling of the new student service centre "SuperC" of RWTH Aachen University. Aachen is located in a complex geologic and tectonic position at the northern margin of the Variscan deformation front at the borders between the Brabant Massif, the Hohes Venn/Eifel areas and the presently active rift zone of the Lower Rhine Embayment, where existing data on in situ stress show complex changes over short distances. The borehole offers a unique opportunity to study varying stress regimes in this area of complex geodynamic evolution.This study of the in situ stresses is based on the observation of compressive borehole breakouts and drilling-induced tensile fractures in electrical and acoustic image logs. The borehole failure analysis shows that the maximum horizontal stress trends SE-NW which is in accordance with the general West European stress trend. Stress magnitudes modelled in accordance to the Mohr-Coulomb Theory of Sliding Friction indicate minimum and maximum horizontal stress gradients of 0.019. MPa/m and 0.038. MPa/m, respectively. The occurrence of drilling-induced tensile failure and the calculated in situ stress magnitudes are consistent with a model of strike-slip deformation.The observed strike-slip faulting regime supports the extension of the Brabant Shear Zone proposed by Ahorner (1975) into the Aachen city area, where it joins the major normal faulting set of the Roer Valley Graben zone. This intersection of the inherited Variscan deformation grain and the Cenozoic deformation resulting in recent strike-slip and normal faulting activity proves the tectonically different deformation responses over a short distance between the long-lived Brabant Massif and the Cenozoic Rhine Rift System. © 2010 Elsevier B.V.

van Gent H.W.,RWTH Aachen | Holland M.,RWTH Aachen | Holland M.,Geomechanics International Inc. | Urai J.L.,RWTH Aachen | Loosveld R.,Royal Dutch Shell
Journal of Structural Geology | Year: 2010

We present analogue models of the formation of dilatant normal faults and fractures in carbonate fault zones, using cohesive hemihydrate powder (CaSO4·H2O). The evolution of these dilatant fault zones involves a range of processes such as fragmentation, gravity-driven breccia transport and the formation of dilatant jogs. To allow scaling to natural prototypes, extensive material characterisation was done. This showed that tensile strength and cohesion depend on the state of compaction, whereas the friction angle remains approximately constant. In our models, tensile strength of the hemihydrate increases with depth from 9 to 50. Pa, while cohesion increases from 40 to 250. Pa. We studied homogeneous and layered material sequences, using sand as a relatively weak layer and hemihydrate/graphite mixtures as a slightly stronger layer. Deformation was analyzed by time-lapse photography and Particle Image Velocimetry (PIV) to calculate the evolution of the displacement field. With PIV the initial, predominantly elastic deformation and progressive localization of deformation are observed in detail. We observed near-vertical opening-mode fractures near the surface. With increasing depth, dilational shear faults were dominant, with releasing jogs forming at fault-dip variations. A transition to non-dilatant shear faults was observed near the bottom of the model. In models with mechanical stratigraphy, fault zones are more complex. The inferred stress states and strengths in different parts of the model agree with the observed transitions in the mode of deformation. © 2009 Elsevier Ltd.

Rabe C.,Geomechanics International Inc. | Ortiz-Ramirez J.,PEMEX
Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010 | Year: 2010

Hydraulic fracture stimulation to increase the hydrocarbon production in heterogeneous and thin turbidite reservoirs such as those found in Chicontepec Paleocanyon Sandstone (Mexico) depends on the formation properties like rock properties, stress state, pore-pressure, flow quality properties and formation heterogeneity. This paper presents a laboratory campaign (petrographical and mechanical), well-logs campaign (petrophysical and images) and field measurements (pressure measurement and leakoff) to build the geomechanical model of the studied area. The main purpose of this paper is to describe a methodology to evaluate the impact of geomechanics in the fracture design optimization in Soledad Field, Chicontepec Basin. © 2010 Taylor & Francis Group.

Rabe C.,Geomechanics International Inc. | Ortiz-Ramirez J.,PEMEX
44th US Rock Mechanics Symposium - 5th US/Canada Rock Mechanics Symposium | Year: 2010

This paper presents a developed methodology integrating geomechanics, reservoir engineering and completion design to optimize the hydraulic fracture in horizontal wells in the Soledad Field, Chicontepec Basin. The impact of geomechanics model, fracture design as well as the fluid flow due to oil production was analyzed. Prediction of forecast oil production considering the impact of stress state and fracture shape and its propagation were considered in the technical and economical perspectives based on expected oil production. Impact of pore pressure to re-fracturing operations is also presented. In this paper we discuss the impact of geomechanics in the completion strategy to optimize production in the studied area. Copyright 2010 ARMA, American Rock Mechanics Association.

A method of simulating water-hammer waves in a borehole is used to estimate formation parameters such as porosity and permeability, and to design completion strings. The simulation method uses a model that has a plurality of layers, at least one of the layers includes radial layering.

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