The Geomechanics of CO2 Storage in Deep Sedimentary Formations

This paper provides a review of the geomechanics and modeling of geomechanics associated with geologic carbon storage (GCS), focusing on storage in deep sedimentary formations, in particular saline aquifers. The paper first introduces the concept of storage in deep sedimentary formations, the geomechanical processes and issues related with such an operation, and the relevant geomechanical modeling tools. This is followed by a more detailed review of geomechanical aspects, including reservoir stress-strain and microseismicity, well integrity, caprock sealing performance, and the potential for fault reactivation and notable (felt) seismic events. Geomechanical observations at current GCS field deployments, mainly at the In Salah CO2 storage project in Algeria, are also integrated into the review. The In Salah project, with its injection into a relatively thin, low-permeability sandstone is an excellent analogue to the saline aquifers that might be used for large scale GCS in parts of Northwest Europe, the U.S. Midwest, and China. Some of the lessons learned at In Salah related to geomechanics are discussed, including how monitoring of geomechanical responses is used for detecting subsurface geomechanical changes and tracking fluid movements, and how such monitoring and geomechanical analyses have led to preventative changes in the injection parameters. Recently, the importance of geomechanics has become more widely recognized among GCS stakeholders, especially with respect to the potential for triggering notable (felt) seismic events and how such events could impact the long-term integrity of a CO{sub 2} repository (as well as how it could impact the public perception of GCS). As described in the paper, to date, no notable seismic event has been reported from any of the current CO{sub 2} storage projects, although some unfelt microseismic activities have been detected by geophones. However, potential future commercial GCS operations from large power plants will require injection at a much larger scale. For such largescale injections, a staged, learn-as-you-go approach is recommended, involving a gradual increase of injection rates combined with continuous monitoring of geomechanical changes, as well as siting beneath a multiple layered overburden for multiple flow barrier protection, should an unexpected deep fault reactivation occur

Barite equilibrium in marine sediments from the entire IODP porewater composition data base

ACTInternational audienc

Le raid des 7 bornes: leçons d’une traversée est/ouest du sud de la Guyane.

National audienceLa région de la frontière terrestre entre Guyane française et Brésil, souvent désignée sous le nom de « monts Tumuc-Humac », a longtemps attiré l’attention des explorateurs, puis des aventuriers, en raison des difficultés d’accès mais aussi en raison de son association avec la légende de l’Eldorado. Pourtant, en raison des difficultés d’accès, la traversée est-ouest de ce que certains ont présenté comme un « massif », voire une« cordillère » n’a quasiment jamais été entreprise avant le XXe siècle. Nous présentons dans ce texte les résultats d’une expédition, menée en 2015, qui a suivi dans son intégralité la frontière terrestre entre la Guyane française et le Brésil, réalisant donc ce trajet : « le raid des 7 bornes ». En plus de sa dimension logistique et sportive, le raid se voulait une reconnaissance géographique, permettant de replacer la frontière dans soncontexte historique et géographique et apportant des éléments pour l’étude des formations végétales ou du peuplement ancien. Bien que tous les résultats ne soient pas encore disponibles, ce texte vise à présenter l’opération et la manière dont elle a été réalisée, ainsi que ses principaux enseignements. Nous présentons donc dans un premier temps le contexte de l’exploration du sud de la Guyane et des « monts Tumuc-Humac » depuis le XVIIIe siècle. Nous décrivons ensuite l’expédition telle qu’elle était conçue et la manière dont elle s’est déroulée, en zone coeur du Parc amazonien de Guyane. Nous livrons ensuite les principaux résultats disponibles à ce jour

Giant submarine collapse of a carbonate platform at the Turonian-Coniacian transition : the Ayabacas Formation, southern Peru

The Ayabacas Formation of southern Peru is an impressive unit formed by the giant submarine collapse of the mid-Cretaceous carbonate platform of the western Peru back-arc basin (WPBAB), near the Turonian-Coniacian transition (similar to 90-89 Ma). It extends along the southwestern edge of the Cordillera Oriental and throughout the Altiplano and Cordillera Occidental over > 80 000 km(2) in map view, and represents a volume of displaced sediments of > 10 000 km(3). The collapse occurred down the basin slope, i.e. toward the SW. Six zones are characterised on the basis of deformational facies, and a seventh corresponds to the northeastern 'stable' area (Zone 0). Zones 1-3 display increasing fragmentation from NE to SW, and are composed of limestone rafts and sheets embedded in a matrix of mainly red, partly calcareous and locally sandy, mudstones to siltstones. In contrast, in Zones 4 and 5 the unit consists only of displaced and stacked limestone masses forming a 'sedimentary thrust and fold system', with sizes increasing to the southwest. In Zone 6, the upper part of the limestone succession consists of rafts and sheets stacked over the regularly bedded lower part. The triggering of this extremely large mass wasting clearly ensued from slope creation, oversteepening and seismicity produced by extensional tectonic activity, as demonstrated by the observation of synsedimentary normal faults and related thickness variations. Other factors, such as pore pressure increases or lithification contrasts probably facilitated sliding. The key role of tectonics is strengthened by the specific relationships between the basin and collapse histories and two major fault systems that cross the study area. The Ayabacas collapse occurred at a turning point in the Central Andean evolution. Before the event, the back-arc basin had been essentially marine and deepened to the west, with little volcanic activity taking place at the arc. After the event, the back-arc was occupied by continental to near-continental environments, and was bounded to the southwest by a massive volcanic arc shedding debris and tuffs into the basin

Analogue modelling of fault reactivation : tectonic inversion and oblique remobilisation of grabens

Journal of Structural Geology, v. 24, n. 11, p. 1741-1752, 2002. http://dx.doi.org/10.1016/S0191-8141(01)00129-8International audienc

Analogue modelling of reverse fault reactivation in strike-slip and transpressive regimes: Application to the Giudicarie fault system, Italian Eastern Alps

Sandbox analogue models were used to study the reactivation of a reverse fault in strike-slip and transpressive regimes, for comparison with the evolution of the Giudicarie fault system in the Central Eastern Alps. The Giudicarie system is interpreted as resulting from Late Miocene sinistral transpressive reactivation of an older, Late Oligocene reverse fault. The 'old' reverse fault was reproduced as a pre-cut dilatant surface obtained by pulling a stiff metal wire through the model sand layer. The position of the pre-existing fault with respect to the base plate fault accommodating the strike-slip and transpressive faulting phase controlled the extent and geometry of reactivation. The clearest reactivation in a pure strike-slip regime was achieved in experiments where the basal strike-slip fault was immediately below the pre-existing fault plane. This strong reactivation involved lateral extrusion and lateral stepping of secondary faults from the basal fault to the pre-existing reverse fault. In the case of transpression, the most spectacular reactivation was achieved for a convergence angle of 10°. Strongly asymmetric structures developed on either side of the pre-cut dilatant zone. The analogue experiments reproduced very closely the structural features of the Giudicarie fault system, supporting a model involving a twofold tectonic evolution for the Giudicarie fault system, with later reactivation in sinistral transpression of an older reverse fault. © 2003 Elsevier Ltd. All rights reserved

Treatment of leishmaniasis in the Oyapock basin (French Guiana) : a KAP survey and analysis of the evolution of phytotherapy knowledge amongst Wayapi Indians

Ethnopharmacological relevance: Cutaneous leishmaniasis is a neglected disease with a high incidence in French Guiana, mainly in the middle and upper Oyapock basin, where Amerindian and some Brazilian people live. The main goals of this work were (i) to assess the knowledge about leishmaniasis in the different populations of the middle and upper Oyapock basin, (ii) to study the therapeutic strategies adopted by people affected by leishmaniasis and (iii) to document the use of phytotherapeutic remedies for leishmaniasis. Knowledge, attitudes and practices (K.A.P.) related to this disease and its treatments have been studied according to cultural group and geographical settlement. Within the Wayapi group, the evolution of the knowledge of phytoremedies over the last 20 years has been characterised by literature-based comparisons. Materials and methods: A total of 144 questionnaires were administered in all the villages of the upper Oyapock and Camopi basins. Correspondence analyses were used for multivariate analysis. Plant species were identified at the Cayenne Herbarium (CAY). Results: The biomedical concept of leishmaniasis correlates well with the Teko and Wayapi concepts of kalasapa and kalasapau. Although the vector of this disease was not correctly identified, the most commonly cited aetiology (74.5%) was vector-borne, and related epidemiological schemes correlate well with the one encountered in French Guiana. Theoretically and practically, health centres were the most commonly used resource for diagnostic in instances of leishmaniasis infection (65.9%), independently of the patient's cultural group, along with the use of pharmaceutical drugs (85.3%). Pharmaceuticals were commonly utilised despite the frequent (51.5%) use of phytotherapeutic remedies, alone or in combination with drugs. The most cited medicinal plant species for the treatment of leishmaniasis included Eleutherine bulbosa (Mill.) Urb. (Iridaceae, cited 14 times), Euterpe oleracea Mart. (Arecaceae, 9), Cecropia obtusa Trecul (Cecropiaceae, 8), Jatropha curcas L (Euphorbiaceae, 7), Ceiba pentandra (L) Gaertn. (Bombacaceae, 6) and Carica papaya L (Caricaceae, 6). Multiple correspondence analyses demonstrated that the species used in leishmaniasis remedies are more prone to vary by the user's place of residence than by their cultural origin, which indicates that exchange of knowledge about leishmaniasis remedies has occurred across different cultural groups. Literature-based comparisons between the remedies for leishmaniasis used by the Wayapi during the 1980s showed a striking evolution, both in terms of diversity of species and number of plants used. The large number of species shared with other Guianese groups argues for intercultural exchange and may explain the majority (57.1%) of the newly used species highlighted in our study. Conclusions: Leishmaniasis is a well-known disease in the studied area. Phytotherapeutic treatments are still in use, although they are not the main source of remedies, and should undergo pharmacological studies to evaluate their potential therapeutic value