Logging Evaluation Of Fractured Reservoirs

The fractured reservoirs are the reservoirs whose major reservoir space and influent tunnel is composed of the fractures and dissolved caves, dissolved pores connected by fractures. As long as fractures grow well, tight sandstone, tight carbonatite, claystone, igneous rock and metamorphic rock can become fractured reservoirs. To evaluate fracture distribution and extension well is key to explore fractured reservoirs successfully.For many years, fracture Identification , stress sensitivity and productivity of natural fractures have not been resolved as a problem during exploring and exploiting fractured reservoirs. In this paper, these problems have been researched basing on logging data.By calculating and analyzing rock strength of fractured formation, the strong character can be found evidently. The rock strength at fractured formation is low, especially at low-angle fractured formation. Basing on Grey theory, using logging and rock strength , fractures can be identified well,, especially for low-angle fracture.The model of stress sensitivity of fracture has been established and an approach evaluating the critical pore pressure for holding rock shrink rapidly has been presented. By analyzing some samples, the conclusion has been drawn as the following: at the same stress field, the larger the fracture aperture and permeability is, the stronger the stress-sensitivity of rock fractures is.Productivity Index is chosen to evaluate productivity. The result show that skin factor and permeability have more effects on produtivity. Because fracture permeability is affected, productivity was effect by stress sensitivity too. Moreover, the stronger the stress sensitivity of natural fractures is, the more effects there are. This conclusion can interpret that the productivity decreases rapidly at initial stage of production.By a series of analysis and research, the applied field of logging has been widen. At the same time, all the conclusions show that cheap, data continuum and information abundant logging can be used in the oil and gas exploit fields.