The Formation Mechanism And Quantitative Evaluating On The Low Resistivity Oil Bed Of The Southern Songliao Basin

With increasing of the exploration difficulty, it is important to seek the subtle and unconventional pool in the petroleum exploration and development fields, the low resistivity pool is one of the most important targets. It is very necessary to deeply realize and quantitatively evaluate the low resistivity oil bed with expediting of the exploration step. This study object has important theoretical significance and practical value in the petroliferous basin. In this paper, based on the widely studying the basic data on low resistivity reservoir bed, the author selects six representative regions (Dalaoyefu, Daqingzijing, Haituozi, Sifangtuozi, Hongang and Daanbei) and assimilates many data, such as well logging integrated interpretation figure ,core comprehensive map, analysis report of physical properties, production test of geology report, reserves report and so on., then selects five low resistivity beds (Dalaoyefu (K1qn1) , Daqingzijing (K1y1, K1q2+3), Haituozi (K1y2+3), Sifangtuozi (K1qn3)) in Dalaoyefu, Daqingzijing, Haituozi and Sifangtuozi regions and tests more 60 blocks of core samples, illuminates the geologic background on formation of the low resistivity reserve, analyzes and correlates lithology composition, physical properties, electrical property, microscopic pore structure and hydro-character between normal and low resistivity reservoir bed. Based on these studies, this paper anatomizes the formation mechanism of low resistivity reservoir bed. From assay of core, researching the result of the petrophysical test and utilizing the NMR data, builds the high precision and quantification logging interpretation model and the practical electrical property correction chart in the condition of sandstone and mudstone thin interbed. Combines the capillary analysis data, firstly builds the reservoir bed parameter interpretation model under the condition of unknown T2cutofb successfully decreases the interpretation error derived from T2 cutoff fluctuating. This paper designs semi-quantitative and quantitative methods, which can identify low resistivity oil-bed and water-bed. The main achievement and realization as follows:1. The low resistivity oil bed is relatively low resistivity oil bed in the southern Songliao basin, so the oil-bearing formation whose resistivity increase rate resistivity of oil bed vs resistivity of water-bed under the condition of similar physical properties less than or equal to 3 is defined as the low resistivity oil bed.2. The low resistivity reservoir bed is located in the sedimentary microfacies of the fan delta frontal (or delta) subfacies, such as river mouth bar, distal bar, sheet sand and so on, whose lithology compositions is fine aleurolite, pelitic siltstone and silty mudstone. This lithology composition character and the potential microscopic pore structure character, hydro-character in the pore consist of are necessary geologic background during the formation of the low resistivity reservoir.3. The main lithology of low resistivity reservoir is siltstone, the pelitic content is higher, the mineral component maturity of rock skeleton is lower, which includes quartz, feldspar and detritus, the feldspar content is higher than that of quartz. The cementing matter is calcic and pelitic; the clay mineral component is main illite and illite/smectite mixed layer. In general the carbonate content is low in reservoir, but some parts are high, the pyrite content is low (<4%).4. The low resistivity reservoir pore structure is complex and distributes double peak character, the heterogeneity degree is strong, the maximum effective pore and throat radius is small and the variation interval is big.5. The conducive reservoir belongs to range from middle porosity to low porosity and from low permeability to especial low permeability, the porosity variation range is from 10 percent to 20 percent and the permeability is less than 1-100X 10-3u m2, at the same time, the bound water saturation variation range is from 17 percent to 35 percent. High bound water saturation i...