TIDAL MICROFACIES OF NAPO FORMATION OF HORM-NANTU OILFIELD, ORIENTE BASIN, ECUADOR

By synthetically utilizing varieties of data such as core, well logging, mud logging, and seismology, and summarizing sedimentary characteristics of rocks developed in different environments and specific responses of well logging curves to all kinds of sedimentary units, we identify and divide microfacies in tidal flat environments on the basis of single sand bodies, and then sedimentary pattern of tidal flat is established. At the same time, by use of seismic attributes and inversion technique to help estimate the strike of tidal channels and expanding range, the distribution features of single sand body microfacies of the research area are obtained in the condition of limited well data. The result indicates that LU and M1 formations of Horm-Nantu Oilfield grossly belong to tidal flat depositional systems. M1 was made of two cycles of tide from down to up, with two larger scale major channels developed in the lower part along the NE-SW direction, and with one tidal channel developed in another tidal cycle in a mixed flat surrounding. The granularity of the whole LU formation becomes coarse from down to up, with tidal channel sand bodies developed for both LU-4 and LU-3 with large thickness and good physical properties, and is stretching a long distance from land to sea. Coarse-grained tidal channel sediment was deposited for the LU-2 small layer, with a large area of mud material and vertically developing typical progradation sequences of marine regression. No tidal channel sediment was found in LU-1 sand body and the coarse sediment is almost the sand flat sediment.