Reservoir Logging Evaluation Of Chang6Oil-bearing Formation In Qiaojiawa Area, Jingbian

Low porosity and low permeability reservoir is one of the most important research objects in terms of oil-gas exploration, development and production increase. Although researchers studing on the filed have got some results and established some theoretical model, it is still not enough in well logging evaluation of oil-gas reservoirs. There are so many factors, such as the complex pore structure of low porosity and low permeability reservoirs, the great variability in formation water salinity, the complex logging responses with low resistivity oil layer coexists and high resistivity water layer, etc, which seriously impede the recognition and assessment of low porosity and low permeability reservoirs and produce great difficulties for the rapid construction of large production.Qiaojiawa oilfield, a typical low porosity and low permeability reservoir, is in Jingbian county, north of Ordos Basin. Taking chang62reservoir in this oilfield as the research object, setting out from the geological characteristics of the low porosity and low permeability reservoir, aiming at the difficulties of lithology recognition, log response complex for different fluid, this paper focuses on the research of four-property relationship of reservoirs through the comprehensive analysis on various basic geological data, logging information, laboratory analysis data and production information, then comprehensively apply technical methods such as single-well-overlapping technique, multi-well cross-plot method and oil saturation quantitative logging interpretation model, to complete chang6logging evaluation on hydrocarbon reservoir, finally obtain the following conclusions and understandings:(1) The sedimentary subfacies of Chang62in Qiaojiawa oilfield is delta plain sedimentary, sedimentary microfacies mainly includes distributary channel, flooding plain, natural levee and crevasse splay. The rock types here are mainly gray, off-white feldspar sandstone. Clay minerals mostly are chlorite cementation, the reservoir rock developed intergranular dissolved pore and intragranular dissolved pore, there are some microfractures in the area.(2) The study based on the "core calibration"and"four-property" relationship shows that, the natural gamma ray, acoustic time and resistivity curve of electrical curves are sensitive to reservoir lithology, physical properties and oil content. Acoustic time-resistivity curve overlay method of Single well can identify oil in the reservoirs effectively. Acoustic time-resistivity curve cross plot of multi-well crossplot technique can effectively identify the oil layer, oil-water layer, water layer and dry layer.(3) Establish oil saturation quantitative interpretation model according to Archie formula method to identify oiliness quantitatively in the reservoirs, then use high pressure mercury injection method("J" function method) and oil-water phase permeability method to check, and the results are consistent. The analysis to the plane contrast between actual oil production and logging interpretation of oil saturation, ultimately prove that the logging interpretation model meet the interpretation accuracy requirements.