| Popis: |
La Ceibita field is located in the Oficina area in the Eastern Venezuela Basin. A total of 63 wells have been drilled, 48 (76%) with "old logs", run prior to 1968, only 15 (24%) have log runs between 1968 and 1982, including modern porosity logs. Production in the studied reservoir began in 1957, and 11 wells have been completed. A gas injection program was implemented in 1960 in order to maintain reservoir pressure. The purpose of the study was to generate a detailed petrophysical model using a methodology based on rock type characterization, integrating core, logs, production data, and, geological and reservoir information, in order to optimize exploitation plans and validate reserves. The petrophysical characterization aimed the definition of rock types, which were classified based on pore throat radius estimated from mercury injection capillary pressure data. Pore throat radii corresponding to a mercury saturation of 45% represented the dominant interconnected pore system. Ranges of rock types from mega to nanno porous were used to define flow units, with pore throat radius being the dominant control on permeability and flow capacity. Due to the lack of modern porosity logs it was necessary to apply a methodology to estimate porosity from the short normal curve, which was related with core porosity. The detailed upscaling from core to log was performed using the relation found between pore throat radius obtained from cores and true formation resistivity from electrical logs in the key well. Once porosity and pore throat radius were known, permeability was estimated from the Pittman R45 equation, which relates pore throat radius with conventional porosity and permeability. Cross sections and maps of rock type distribution were used to observe the lateral rock type variability and allowed to identify the areas with better rock quality. The combination of this information with sedimentary facies maps will help model the reservoir and select prospective areas for development. Detailed reservoir upscaling by matching core and old log data will only be possible through the integration of geological, petrophysical and production data. |
