Oil & Gas Geology ›› 2011, Vol. 32 ›› Issue (2): 245-250.doi: 10.11743/ogg20110212
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Abstract: As low resistivity reservoirs have similar resistivity as water layers, it is difficult to differentiate water layers from low resistivity reservoirs, and to determine oilwater contacts by using conventional logging data. Experimental study on relationship between full waterbearing conductivity (Co) and solution conductivity (Cw) with samples from lowresistivity layers and nonlowresistivity layers shows that the additional conductivity contributed by clay minerals is the main factor leading to the low resistivity of the second unit of the Triassic in Jilake area. When this type of lowresistivity reservoirs is penetrated, anions on clay surface may absorb cations in the solution. The cations absorbed to clay surface in turn may further impede the migration of anions in the solution, resulting in ion retention in the low resistivity reservoirs and charge shielding. The negative difference of SP log of the lowresistivity layers decreases in comparison with the nonlowresistivity layers. A quasispontaneous curve (SPrt) of nonlowresistivity layers is then created and compared with the SP curve to identify lowresistivity layers. This method has been successfully applied to recognize the lowresistivity reservoirs in the study area.
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URL: http://ogg.pepris.com/EN/10.11743/ogg20110212
http://ogg.pepris.com/EN/Y2011/V32/I2/245