Modelling Study Of Ultra-low Permeability Reservoir In The Ordos Basin

Low permeability reservoir gets a very important position and will get a higher and higher proportion in the future. With the direction of modern sedimentology theory and high resolution sequence stratigraphy, this study adopts various kinds of means to characterize the reservoir property and heterogeneity of ultra-low permeability reservoir in light of the core, outcrop, log and test data synthetically, and gets 3D reservoir models by the means of isochronal faces-restrained stochastic modeling, providing geological bases for the following adjustment of exploitation project.The dissertation takes well blocks zhuang 9 and zhuang 40 whose permeability are below 1×10– 3um2 of XiFeng oilfield in the Ordos basin for instances. Integrated with background of areal geology and electrofacies analysis, according to outcrop observation, core description and so on, it shows that the chang-8 oil layer of zhuang-9 block belongs to braided river-delta, while the chang-6 oil layer of zhuang-40 block belongs to turbidities fan. The high resolution sequence stratigraphic framework of study area is built and the spreading and evolution regularity of sedimentary microfacies in the framework is well studied.The core of this dissertation is to study the ultra-low permeability reservoir property and heterogeneity of study area from macroscopic and microscopic features synthetically. It is also one of the main innovative achievements. Macroscopically, it is emphasized that outcrop and logging data are analysed synthetically. From the observation and measurement of outcrop, the inner-architecture patterns of distributary channels and mid-fan channels are established, the characterization and distribution of main sand body are both made clear roundly, providing essential data for the 3D modeling. Microcosmically, comprehensive application of core observation and reservoir test data is highlighted. The reservoir of study area characterizes with small pores and micro throats, the sendimental environment and base level change are main affecting factors of heterogeneity and interlayer distribution. In the sand bodies of underwater distributary channels and braided channels of low accommodation, their reservoir property and connectivity are relatively good, which are main product layers of study area's ultra-low permeability reservoir.The information of horizontal wells is well used in the 3D modeling, enhancing the precision of 3D modeling. Correlation between horizontal well and vertical well provides some more data to establish the 3-D structural model, while lithology description of horizontal well provides new means to evaluate geological model. variogram function fitting of attribute parameters of horizontal well provides an important referrence in attributes modeling.Finally, on the basis of comprehensive geology study, utilizing software Petrel, adopting sequential indicator stochastic simulation method to delineating sedimentary microfacies. Adopting sequential Gaussian simulation method, we get the porosity model and the permeability model. In addition, this dissertation also do some study on fractal theory to predict the inter-well attributes and grey comprehensive appraisal models to evaluate reservoir.