Integrated Reservior Prediction Of Paleozoic Clastic Rock In Southwest Tahe Area

On the basis of previous work, an interdisciplinary research of sedimentology, petrography and exploration geophysics is utilized to characterize the reservoir of Paleozoic clastic rocks in Southwest Tahe oil play of Tarim basin northwest China. Four scales of information from thin sections, core, well logs and 3-D seismic data are analyzed by means of a variety of techniques and tools to construct the reservoir model that can illustrate the dimensional architecture of the reservoir rocks in different angles of point-line-surface. The results of reservoir prediction provide a substantial foundation for further exploration and development in Paleozoic clasitc pools of Tahe Oilfield. The main conclusion are showed as follows.The depositional facies and prospect sandbodies are systematically analyzed based on examinations of core and microscopic thin sections, grainsize statistics, log curves and 3-D seismic data. The depositional patterns of three research target intervals in Tahe area are inferred from above analysis. The Lower Sand-mud Member of Lower Carboniferous Bachu Formation belongs to proximate barrier-island and strand plain facies in which prospect reservoir consists of beach microfacies. Upper Devonian Donghetang Formation are composed of fluvially dominated delta and strand plain system and the prospect reservoir facies is mouth bar and subaqueous distributary channels. Lower Silurian Kepingtage Formation are deposited under tidal flat environment without barrier island and its prospect facies for reservoir is tidal channel microfacies.The por-permability, porous types and structures are intensively analysized. The main pore types are remained intergranular pores and innergranular dissolved pores . The development and evolution of pores are mainly subject to sedimentary environment and diageneses . Beach sandstone in lower Bachu Formation and Donghe sandstone are the best reservoirs in this area. Secondly the tidal channel sandstones of Kepingtage Formation still possess somewhat storage capability. Most of clastic rocks deposited under hypopycnal flows of Lower Bachu Formation are outside of the por-perm conditions of reservoirs.All log curves were processed for environmental correction and standardization before calculating shale volume, porosity, and water saturate that are usually used in pool evaluation and constrain seismic inversion. A great deal of seismic attributes are extracted, Three of them are found to be sensitive to depositional facies and reservoirs distribution. They are RMS-Amplitude , Slope of Reflection Strength and Wave classification . A relationship between these seismic attributes and thickness and content of sandstone reservoirs are constructed by means of cross plot techniques.Based on impedance inversion , the relationship between impedance and porosity , volume of shale and so on are established with geological statistics method. Inversion on natural gamma-ray , spontaneous-potential (SP) , porosity and oil saturation were made to predict effective reservoir distribution . All of research above are integrated finally with well test and structural map to outline favorable exploration target and traps.All in all , traditional geological methods are combined closely with advanced geophysical techniques to predict reservoir distribution, and it comes to a satisfied result in exploration and production of Tahe area.