The impact of carbonate cements on the reservoir quaility in the Napo Fm sandstones (Cretaceous Oriente Basin, Ecuador)

The Napo Formation of Lower-Middle Cretaceous age in the Oriente basin, Ecuador, is an important sandstone reservoir. The formation is buried at a depth of 1500 m in the eastern part of the basin and down to 3,100 m in the western part. The sandstones display higher porosity values (av. 20%) than other reservoirs in the region. These sandstones were deposited in fluvial, transitional and marine environments, and they are fine to medium grained quartzarenites and subarkoses. The principal cements are carbonates, quartz overgrowth and kaolin, with scarce amounts of pyrite-pyrrhotite and chlorite. Carbonate cements include: Eogenetic siderite (S1), mesogenetic and post-compactional calcite, Fe-dolomite, ankerite and siderite (S2). Early siderite and chlorite helped to retain porosity by supporting the sandstone framework against compaction. Dissolution of feldspars and carbonate cements are the main mechanism for secondary porosity development during mesodiagenesis. The high intergranular volume (IGV) of the sandstones indicates that cementation is the predominant contributor to porosity loss in the reservoir and that the precipitation of the carbonate cement occurred in early and late diagenetic stages. The stable-isotope composition of the S1 siderite is consistent with precipitation from meteoric waters in fluvial sandstones, and from mixed meteoric and marine waters in transitional sandstones. The low values of some of these carbonate phases reflect the replacement and recristalization from S1 to S2 siderite at deep burial and high temperature. Textural evidence, together with a low Sr content, also suggests that siderite (S1) in fluvial environment is an early cement that precipitated from meteoric waters, near the sediment/water interphase, followed by the generation of calcite with a higher Fe and Mg content. However, due to this higher Mg content, siderite S2 could have precipitated as a result of the thermal descarboxilation of the Mg rich organic matter. The progressive decrease in values in all carbonate cements could be related to the continued precipitation at different temperatures and burial depth

Characterization of asphaltic oil occurrences from the southeastern margin of the Basque-Cantabrian Basin, Spain

A geochemical investigation has been undertaken on biodegraded hydrocarbons in outcropping reservoirs of the south-eastern margin of the Basque-Cantabrian Basin (Álava sector). The aims of the study were the characterization of the geochemical features and biodegradation level of these hydrocarbons, and the evaluation of their resemblance to oils from the Ayoluengo onshore oil field by means of isotopic analyses and gas chromatography-mass spectrometry techniques. Most of the samples lack n-alkanes, isoprenoids, low molecular weight aromatic compounds, steranes, homohopanes, diasteranes and triaromatic steroids, whereas hexacyclic and heptacyclic alkanes appear as key compounds although some structures were not totally elucidated. Thermal maturity has been assessed with several parameters and a calculated-equivalent vitrinite reflectance value of around 0.8% was estimated. In addition, gammacerane content, diasterane-to-sterane ratio and C35 to C34 hopanes ratio suggest that the Álava oil shows were derived from a carbonate rock deposited in a reducing, water-stratified and possibly hypersaline environment. Isotopic signatures and other data confirmed that these hydrocarbons are not genetically related to the oils from Ayoluengo and, consequently, their origin is associated with a yet unknown source rock in the basin

The Impact of carbonate cements on the reservoir quality in the Napo Fm sandstones (Cretaceous Oriente Basin, Ecuador)

The Napo Formation of Lower-Middle Cretaceous age in the Oriente basin, Ecuador, is an important sandstone reservoir. The formation is buried at a depth of 1,500 m in the eastern part of the basin and down to 3,100 m in the western part. The sandstones display higher porosity values (av. 20%) than other reservoirs in the region. These sandstones were deposited in fluvial, transitional and marine environments, and they are fine to medium grained quartzarenites and subarkoses. The principal cements are carbonates, quartz overgrowth and kaolin, with scarce amounts of pyrite-pyrrhotite and chlorite. Carbonate cements include: Eogenetic siderite (S1), mesogenetic and post-compactional calcite, Fe-dolomite, ankerite and siderite (S2). Early siderite and chlorite helped to retain porosity by supporting the sandstone framework against compaction. Dissolution of feldspars and carbonate cements are the main mechanism for secondary porosity development during mesodiagenesis. The high intergranular volume (IGV) of the sandstones indicates that cementation is the predominant contributor to porosity loss in the reservoir and that the precipitation of the carbonate cement occurred in early and late diagenetic stages. The stable-isotope composition of the S1 siderite is consistent with precipitation from meteoric waters in fluvial sandstones, and from mixed meteoric and marine waters in transitional sandstones. The low δ18O‰ values of some of these carbonate phases reflect the replacement and recristalization from S1 to S2 siderite at deep burial and high temperature. Textural evidence, together with a low Sr content, also suggests that siderite (S1) in fluvial environment is an early cement that precipitated from meteoric waters, near the sediment/ water interphase, followed by the generation of calcite with a higher Fe and Mg content. However, due to this higher Mg content, siderite S2 could have precipitated as a result of the thermal descarboxilation of the Mg rich organic matter. The progressive decrease in δ18O values in all carbonate cements could be related to the continued precipitation at different temperatures and burial depth

Who studies whom and who benefits from sociolinguistic research?

Examines the nature of Soviet involvement through arms transfers in Central America and the Caribbean Basin. Soviet policy after Fidel Castro\u27s revolution in Cuba; Success of the 1979 Sandinista revolution in Nicaragua; Overt military buildup in Latin America; Covert arms transfers to Central American insurgents; Impact of the confusing signals from the United States

The bilingual advertising decision

This paper examines the relationship between linguistic plurality and the rationale of advertising decisions. The presence of two or more languages on one market modifies the traditional advertising problem, and in the absence of literature on the subject, a logical first step is to develop a basic model. This paper presents a simple model of sales to different language groups as a function of the level of advertising in each language, language attitudes, incomes, and an advertising response function. It generates a set of hypotheses about the necessary and sufficient conditions for bilingual advertising to become more profitable than advertising in the majority language alone. A few of the model's results are presented in the paper, showing why indifference to language in the public will produce a unilingual commercial environment, or by how much consumers' resistance to dominant language hegemony can increase the range over which bilingual advertising is profitable. This generates policy recommendations about the level of respective group incomes, the efficiency conditions of boycott or goodwill campaigns, and the role of product differentiation and market structure. This model is intended as a benchmark, and several extensions are suggested, in order to adapt the model to specific cases or allow for the inclusion of more complex causal links. In its present form, it shows how integrating information on the existing commercial environment can provide instruments for language planners