Research On Logging Identification And Evaluation Of Deep Volcanic Reservoirs In Nanpu 5~th Structure

Compared with conventional reservoir, volcanic rock has complicated lithology and physical property, complex pore texture and sharp anisotropism due to volcanic eruption and the latter tectogenesis and diagenesis, favourable reserving space is hard to predicate. So there are mainly three difficulties faced in the petroleum exploration and development: (1) The exact identification of reservoir lithology; (2) Reservoir porosity calculated is more than the real porosity and reservoir effectiveness is poor because of alteration. Commontogether growth of primary and secondary pores and fractures makes the reservoir capacity influencing factors more complicated. (3) Fluid property recognition, many methods of fluid property discrimination in clastic reservoirs are not applicable for volcanic reservoirs.For the volcanic reservoirs of Eogene system of NanPu Sag in Bohai bay Basin, the paper, based on systematical analysis of various data such as logging, well testing, coring and petrophysical experiments, carries out intensive study of lithology identification, reservoir parameter determination and fluid recognition by means of new logging techniques of FMI, ECS, CMR, and DSI. Finally, a complete and useful logging evaluation system of volcanic reservoirs is formed.According to the genetic type and structural property of volcanic rock, a three-stage classification method of"texture"-"component"-"grain size"is adopted to identify the lithology, the volcanic and sedimentary rocks, basic and acid volcanic rocks, volcanic lava, eruptive breccia and volcanic tuff are gradually identified, and finally lithology identification plate of cross-plot and imaging are built up. The frame parameters for each lithology are determined with comprehensive use of core analysis, conventional and ECS logging data on the basis of lithology identification.Log interpretation models are established to calculate reservoir physical parameters. Given the influence of volcanic alteration, this paper evaluates porosity effectiveness by taking advantage of conventional, NMR and FMI logging data. Fluid mobility index and formation anisotropy analysis by DSI are used to evaluate fracture effectiveness, together with formation physical parameters forming a comprehensive evaluation of volcanic reservoirs and thereby determining the criterion of reservoir classification. According to testing and gas surveying data, with the cross plot technique, gas detection by DSI, and the combination of conventional and NMR logging, this paper makes a probe into fluid recognition methods in volcanic reservoirs. The fluid property recognition plates and logging criterion for the classification of gas and water layer are formed, which proved effective in the practical application in the target region.