FRACTURE RESERVOIR CHARACTERIZATION BY FIBER-OPTIC DISTRIBUTED TEMPERATURE LOG
One of the important features of the fiber-optic distributed temperature log is its ability to acquire continuous, instantaneous and simultaneous temperature profile along the entire wellbore. Series of successive temperature profiles sampled every one minute or so enable to analyze transient temperature phenomena, which may pertain to important reservoir properties. For example, when change of rate occurred to the fluid flow such as due to water injection, the temperature profile over the section exhibits transient phenomena associated with the fluid flow. The characteristics of the phenomena depend on several factors including the flow profile which itself exhibits transient nature depending on fluid compressibility, permeability and reservoir extent, the original temperature profile, the temperature of injected fluid and that of the reservoir fluid flowing into the wellbore, the degree of rate alteration, well geometry, flow regime and etc.
Distributed Acoustic Sensing Technology for Seismic Exploration in Magmatic Geothermal Areas
Seismic methods are a cornerstone for the exploration of the subsurface. In comparison to seismic surveys at the surface, downhole measurements can help to gather more detailed information about rock properties as well as potential fluid pathways within geothermal reservoirs. Temperatures within geothermal wells, especially in magmatic environments, however, often exceed the temperature limitation of conventional seismic sensors. One way to overcome the lack of seismic downhole data for geothermal exploration is the application of the novel fiber optic distributed acoustic sensing (DAS) technology. For DAS, an optical fiber is used as seismic sensor. Lowering a fiber optic cable into a well, dynamic vibrations can be measured along the entire fiber with a high spatial resolution. As all electronics can be operated at the surface, the temperature tolerance for the measurement set-up, is defined by the operating temperature range of the fiber optic cable. Special optical fibers can be operated at temperatures up to several hundred degrees centigrade, therefore, closing the gap between the operating temperature limit of conventional seismic sensors and the requirements for a downhole application within geothermal wells. In this paper, the requirements for an installation of a fiber optic cable within a high-temperature well will be discussed, DAS data will be compared to conventional geophone data, and the benefit of applying the DAS technology for seismic exploration within the framework of the Iceland Deep Drilling Project (IDDP) will be outlined.
Geological, mineralogical and chemical characterization of Devonian kaolinite-bearing sediments for further applications in the ceramic (tiles) industry in La Paz, Bolivia
Clay minerals are widely distributed in Bolivia; among them, illitic clays are most common in the Altiplano where they are mined for use in the ceramic industry that has been growing in the last few years. In addition to illitic sediments, kaolinitic sediments have been recently discovered in sedimentary units in the Bolivian Altiplano. Residual ball clay occurrences in Devonian sedimentary units were studied as part of this work. Geological mapping and geophysical studies (ERT and GPR) were done for better understanding the origin of the deposits and were part of a preliminary study of the mineral potential to define the relationship with the host rock. Chemical and mineralogical techniques such as X-Ray Diffraction, Scanning Electron Microscopy and Inductively Coupled Plasma analyses were performed in samples from the studied area to verify the presence of kaolinite. Atterberg limits and behaviour of the raw material in ceramic specimens supported by chemical analyses show that this material is suitable for manufacturing tile ceramics. This study provides fundamental knowledge for deposit exploitation and future generation of an alternative source of employment for the inhabitants of Micaya.