Alberdi-Genolet M.,Geosignals |
Cavallaro A.,YPF SA Direccion de Tecnologia Argentina |
Hernandez N.,YPFSA |
Hernandez N.,PlusPetrol |
And 2 more authors.
Marine and Petroleum Geology | Year: 2013
Heavy-medium oils (14.5-27.9°API) in a studied field of Malargüe area in the Neuquén Basin, Argentina have associated gas that produces between 0 and 4000 ppm H2S and 0.6-103 kg H2S/day. Being able to discriminate between biological and inorganic H2S sources is essential to the oil field's economy. H2S associated with anaerobic bacteria sulfate reduction (BSR) might be mitigated using biocompetitive technologies or bactericides, whereas abiotic H2S from geological sources can be controlled only by sequestration in surface facilities and oil field management if the H2S distribution in different oil pay-zones, field compartments and origin are well known.The isotopic signatures of the H2S (δ34S) range between +2.3 and +7.8‰, which suggests magmatic sources. Laccoliths in the Malargüe area, associated with Tertiary magmatic events were mapped out many decades ago. Petrographic descriptions of igneous samples are consistent with andesitic magmas that bore sulfur-bearing fluids, which are considered the principal source of H2S. Associated hydrothermal fluids, as recorded by secondary minerals, induced rapid TSR (thermochemical sulfate reduction) reactions as documented by mineral phases seen in SEM. Most of the H2S Neuquén Basin has been linked to BSR (bacterial sulfate reduction), however we document a geological origin for the H2S, which is tied to magmatic events.Organic geochemistry and fluid inclusion data allow for an early local generation of hydrocarbons linked to burial followed by a second pulse of light hydrocarbons, gas and H2S associated with the magmatic event. Water geochemistry and the lithology of oil pay-zones are used to predict the distribution of H2S in each well. Wells with less than 20 ppm of H2S are linked to meteoric waters and siliciclastic pay-zones. © 2012 Elsevier Ltd.
Levina M.,University of Texas at Austin |
Horton B.K.,University of Texas at Austin |
Fuentes F.,PlusPetrol |
Stockli D.F.,University of Texas at Austin
Tectonics | Year: 2014
Andean retroarc compression associated with subduction and shallowing of the oceanic Nazca plate resulted in thin-skinned thrusting that partitioned and uplifted Cenozoic foreland basin fill in the Precordillera of west-central Argentina. Evolution of the central segment of the Precordillera fold-thrust belt is informed by new analyses of clastic nonmarine deposits now preserved in three intermontane regions between major east directed thrust faults. We focus on uppermost Oligocene-Miocene basin fill in the axial to frontal Precordillera at 31-32° S along the Río San Juan (Albarracín and Pachaco sections) and the flank of one of the leading thrust structures (Talacasto section). The three successions record hinterland construction of the Frontal Cordillera, regional arc volcanism, and initial exhumation of Precordillera thrust sheets. Provenance changes recorded by detrital zircon U-Pb age populations suggest that initial shortening in the Frontal Cordillera coincided with an early Miocene shift from eolian to fluvial accumulation in the adjacent foreland basin. Upward coarsening of fluvial deposits and increased proportions of Paleozoic clasts reflect cratonward (eastward) advance of deformation into the Precordillera and resultant structural fragmentation of the foreland basin into isolated intermontane segments. Apatite (U-Th)/He thermochronometry of basin fill constrains to 12-9Ma the most probable age of uplift-induced exhumation and cooling of Precordillera thrust sheets. This apparent pulse of exhumation is evident in each succession, suggestive of rapid, large-scale exhumation by synchronous thrusting above a single décollement linking major structures of the Precordillera. © 2014. American Geophysical Union.
Weiss J.R.,University of Hawaii at Manoa |
Brooks B.A.,U.S. Geological Survey |
Arrowsmith J.R.,Arizona State University |
Journal of Geophysical Research B: Solid Earth | Year: 2015
New observations from an active orogenic wedge help link the seismotectonic behavior of individual faults to wedge deformation rates and patterns over multiple timescales. We provide the first detailed constraints on the distribution and timing of deformation at the front of the Andean orogenic wedge in southern Bolivia, where a recent study suggests that great (Mw > 8) earthquakes could rupture the master fault underlying the wedge. We use stratigraphic relationships across fault-related folds and elastic dislocation modeling of seismic reflection horizons to obtain probabilistic estimates of wedge-front fault ages and slip rates. Our analyses reveal that at least half of the previously determined GPS-based wedge-loading and Quaternary whole-wedge shortening rates are absorbed across a 20-40 km wide wedge-front zone consisting of 1-4 en echelon and partially to fully overlapping faults and folds associated with blind thrust faults. The difference between our slip rates and the geodetic/geologic observations combined with evidence for activity across internal wedge structures supports the notion that nonsteady state mass balance conditions coupled with elevated erosional efficiency result in distributed wedge deformation. The orogenic wedge in southern Bolivia behaves in a similar fashion to the Taiwanese and Himalayan ranges; slip accumulates at downdip locations along the master fault and is released incrementally by earthquakes that rupture the wedge-front fault zone. The faults and folds comprising this zone pose a major source of seismic hazard. Accumulating slip is also released in the wedge interior and older, internal wedge faults must be considered in any future assessment of regional earthquake risk. ©2015. American Geophysical Union. All Rights Reserved.
Osorio J.G.,PlusPetrol |
47th US Rock Mechanics / Geomechanics Symposium 2013 | Year: 2013
This paper investigates the qualitative correlation between microseismicity and the geomechanics attributes affecting the hydraulic fracturing performance in Vaca Muerta formation - LJE and PSO blocks - in Neuquén, Argentina. The paper includes typical results from ID geomechanics models in the area, a short description of the microseismic setup, and qualitative correlation between microseismic occurrence and some geomechanics attributes such as stresses, brittleness, rock strength and elastic properties. Results show that: fracture growing follows complex and asymmetric patterns; the high-pressure/high-stress behavior in the lower part of Vaca Muerta, where TOC is at maximum, causes stress anisotropy and impacts formation brittleness unfavorably; low pore pressure and stresses and high stress anisotropy favor fracture complexity; low values of cohesion, tensile strength and Poisson's ratio and high values of Young's modulus correlate with microseismic occurrence. Copyright 2013 ARMA, American Rock Mechanics Association.
Maschio L.,PlusPetrol |
Society of Petroleum Engineers - 5th SPE International Conference on Oilfield Corrosion 2010 | Year: 2010
The San Martin field is east from Lima, in the heart of the Peruvian tropical forest (see Fig 1). It is home to one of the most important non-associated natural gas reserves in Latin America, a vital resource for the energy needs of the country. Tubing integrity in San Martin area has been a concern and a subject of continuous control due to the wells high gas rate, difficult logistic and economic importance. Multi-finger caliper logs were run in all the wells in San Martin field to control and assess tubing condition and integrity. Although the wells produced with low carbon dioxide (CO2) and water content, and no solids, preliminary reviews of the logs showed that only the wells with the highest production rate have wear signs of material loss. This paper recap an extensive investigation performed in all the wells in the San Martin area. In this document logs reports, calculation as well as the ASCII files revision and quality controls are shown. Subsequently, a synopsis of the wear mechanism, its trends, the variables that control it and the extent of the problem using a novel internal processing of the raw caliper data are discussed. Finally, a set of recommendations to reduce the wear effect is presented. Understanding the wear mechanism and documenting the lesson learnt are paramount not only to improve the operations in the San Martin field, but also to use this knowledge to improve the decision-making and management of the upcoming field completions in the same area. Copyright 2010, Society of Petroleum Engineers.