*autor a quien debe ser dirigida la correspondencia.Recibido Jul. 06, 2009; Aceptado Ago. 11, 2009; Versión Final recibida Nov. 13, 2009 RESUMEN El objetivo de esta investigación es estimar los factores de emisión (FE) que permitan valorar la cantidad de material particulado de las vías pavimentadas y no pavimentadas de la ciudad de Mexicali, Baja California, México. Se empleó el modelo AP-42 de la US EPA, bajo un diseño estadístico al azar, correspondiente a 60 sitios de muestreo en un mapa georeferenciado con proyección UTM 11 Norte. Se obtuvieron los valores de carga y porcentaje de sedimento menor a 75 µm en laboratorio, velocidad y número de vehículos, en campo. La estimación de los FE corresponden a 0.92 Kg. PM 10 /VKT y 0.73 Kg. PM 2.5 /VKT en vías pavimentadas y 2.33 Kg. PM 10 /VKT y 0.58 Kg. PM 2.5 /VKT en vías no pavimentadas, respectivamente. El valor de FE propio determina la cantidad de material particulado a suspenderse y la relación de los factores de emisión (PM 10 y PM 2.5 ) en ambas vías indica que es necesario hacer mantenimiento y control de flujo de vehículos. Palabras clave: factor de emisión, vía urbana, sedimento en vía, material particuladoEstimation of PM 10 and PM 2.5 Emission Factors, in City Roadways of Mexicali, Baja California, Mexico ABSTRACTThe objective of this research was to estimate the emission factors (EF) for evaluating the amount of particulate matter from paved and unpaved roads in the city of Mexicali, Baja California, Mexico. The model used was AP-42 of the U.S. EPA, under a random statistical design, corresponding to 60 sampling sites in a georeferenced map UTM 11 North projection. Load values were obtained and percent of sediment less than 75 µm in the laboratory, speed and number of vehicles in the field. The estimated FE correspond to 0.92 kg PM 10 /VKT and 0.73 kg PM 2.5 / VKT on paved road and 2.33 kg PM 10 /VKT and 0.58 kg PM 2.5 / VKT on unpaved roads, respectively. The value of FE determines the amount of particulate matter to be suspended and the relation of the emission factors (PM 10 and PM 2.5 ) in both roadways indicate that maintenance and control of vehicle flux may be needed.

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Chihuido de la Sierra Negra field is the main Repsol-YPF SA oilfield. It is located in the northeastern margin of Neuquén Basin. Main reservoir units are aeolian sandstones from Lower Troncoso Member (HuitrÍn Formation, Aptian) and Avilé Member (Agrio Formation, Hauterivian), with more than 1,000 MM stb oil in place. In 1993 oil was discovered in a thick basic intrusive body intruded pulling apart evaporitic rocks from Upper Troncoso Member (Aptian). The starting of the oilfield development was disappointing due to difficulties in locating wells with the 2D seismic that was available at that moment and the low production rates. 3D-survey acquisition, identification of fracture zones and drilling of horizontal wells increased dramatically the production rates. In this moment the field is under development, producing 12,000 bl/d with 11 wells. This article discusses technical ideas, which have contributed the successful development of a nonconventional reservoir. Introduction Chihuido de la Sierra Negra Field is the main Repsol-YPF SA oilfield, located in the northwestern margin of Neuquén Basin. (Fig.N° 1) Main and traditional reservoir units are aeolian sandstones from Lower Troncoso Member (Huitr n Formation, Aptian) and Avilé Member (Agrio Formation, Hauterivian). (Fig.N° 2) In 1993 the first productive exploration well from an igneous rock intruded in the Upper Troncoso Member was drilled in the Chihuido de la Sierra Negra Area. The reservoir is a low permeability fractured andesite. Production rates from appraisal wells were disappointing but production flowrates from recent development wells have increased dramatically, compared with earlier ones. Maximum well production rate is 3,500bbl/d, it has to be noted that the average for oilfields in the Area is 200bbl/d. The interpretation of the 3D seismic acquisition in 1996 generated key ideas for the successful development of this nontraditional reservoir. Good reservoir conditions were associated with intense fractured zones related to steep sides of the laccolith, generated during the emplacement stage and reactivated later. Dip, azimuth and coherence attribute maps highlight the presence of fractured zones. (Fig. N° 3) This structural pattern matches with fracture orientation obtained by wellbore image log tools. Reservoir description. The igneous body has a laccolithic shape: flat bottom, steep sides and a broadly convex top, with a maximum thickness of 300 m in the central zone as it can be seen in 3D view.(Fig.N.4) It is possible to see the sharp edges of the igneous body and the relationship between them and productive wells. The extension of this body is about 1100 Ha. It is intruded in the evaporitic rocks (halite) of Upper Troncoso Member, at a main depth of 900m. Anhidrite and claystones from Rayoso Member are the seal for this accumulation. Relationship with Member La Tosca limestone is not always concordant as it can be seen in this cross-section. (Fig.N° 5) At this moment it is not possible to say if the reservoir is a single igneous body or several ones. The upper part of the laccolith, according to core description and Gamma Ray logs is a fenoandesite, with 15 millions year age. This andesitic top is more fractured than the rest. Gamma Ray logs allow discriminating in two different zones, which lithological composition is being studied at this moment. This different zones may be due to differential cooling of a single body or several igneous rocks intruded at different times. The feeder zone is in the Cerro Bayo Volcano, 4 km to the south. This laccolithic intrusion has generated a four-way dip closure structure in M.La Tosca limestone. (Fig.N° 6). In this structural map it is possible to see main fracture systems, rossettes obtained processing image logs, and horizontal wells trajectories interesecting the fractures.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractChihuido de la Sierra