Integrative Research Of Fluid Identification On Ultra-low Permeability Reservoir Of Puxi Area

With the development of the exploitation of the western peripheral area of Daqing oil field, it is more and more difficult to use the mothball reserves, so that the exploitation of the low permeability reservoir that representative by Puxi oil field becomes the main exploitation object at present. This kind of oil reservoir keeps more abundant resource, but because of the thin reservoir, bad physical property and unstable development, it is difficult to control the reservoir characteristics and drilling technology, simultaneously, because of the argilliferous, calcareous and thin of the reservoir, multiple types of fluid and complexity of the oil and water relationship, it is difficult to recognize the electric nature of the oil and water and made the low coincidence rate of the interpretation of the oil and water layer. So, in this paper we based on Puxi oil filed developed the fluids identification method and studied the prediction of the potential area of the extra-low permeability reservoir. The contributions of this paper are as follows:1. Developed the deposition nature of the Putaohua oil layer in Puxi oil filed based on the theory of high resolution sequence stratigraphy, separate the Putaohua oli layer into three four-stage sequence(eight systems tracts) Additionally, because of the multiple diversion of river course and crevasse of river channel, there are many secondary cycle geologic record generated by autocyclicity effect, So Putaohua oil layer was separated into eleven layers named PI1-11, where PI1-3is top sandstone group, PI4-6 is middle sandstone group and PI7-11 is underneath sandstone group.2. Based on the above research on sequence stratigraphy, make use of the drill core, mud logging, logging and seismic materials, we do research on the deposit systems of Putaohua oil layer in Puxi oil field, make certain that Putaohua oil layer in Puxi oil field mainly develop delta front intrafacies, main microfacies types are subaqueous distributary channel, lie in distributary channel, mouth bar and sand sheet, because sand body of reservoir distribute discretely, sand body distribute as short strips, moniliformiy and lenses discretely. Sand body connectedness is bad on vertical, heavy clay content. We make certain that this is typically "mud pack sand" deposition type.3. Based on the research of cracks conventional methods such as core observation, image logging, dynamic analysis, we predict the cracks scale effectively mainly by the no-source microseismic. From the result of detection, we can get there are some structure cracks in this reservoir and it is mainly high-angle cracks, the trend is east-north-east. The trend mainly presented the effect and affection of the stress pattern, it is close to the direction of maximum principal stress. Second is north-west- west cracks, it indicates original existence of cracks. The existence of cracks affects the liquid identification of the oil layer, injection strategy and the late development adjustment of the oil field.4. Based on the summary of reservoir logging response that has different kinds of liquid, study on the corresponding logging response mechanism, we think that the low resistance oil layer of Putaohua reservoir was caused by thin layer, high bound water saturation, high shale content, the formation of high resistance water layer is because there is calcium or irreducible oil, so that the resistance become high.5.Develop the study of fluid identification technology of low permeability complex reservoir in view of the problem of the low interpretation coincidence rate. Build up the classification chart method, it is first build up the lithology identification chart of the siltstone, lepto siltstone, calcium tight sandstone, argillaceous siltstone, then according to the different kinds of reservoir, build up the corresponding fluid identification chart, this method improve the identification ability of complex reservoir effectively.We resolved the bottleneck problem restricting Puxi oil-field's development, provided the technique for the big area development of Puxi oil-field via the research in this paper. At the same time, providing reference for the exploitation of the low permeability oil-water layer reservoir like Talaha, Xinzhao , which are in the west in Changyuan of Daqing oil-field.