Prediction of Water Saturation for Tight Sandstone Reservoirs by Using Array Dielectric Logging ADL

Conventional hydrocarbon saturation estimation methods based on porosity and resistivity curves cannot be well used in our target formations due to the difficulty of the determination of necessary input parameters. The formation water resistivity was heavily affected by the various salinity. The water salinity was considered to have little effect to the delectric constant, especially for the delectric constants measured with frequency higher than 200 MHz. In this study, we proposed a new model to predict water saturation from the array delectric logging (ADL) data in the Chang 8 Formation of Penyang region, west Ordos Basin, west China. This model was similar with the classic Archie's equation in form, whereas the involved parameters were much easily to be determined. Based on the lab delectric constant measurements of 6 typical core samples, we determined the input parameters in this new model. Meanwhile, considering the effect of pore structure to delectric measurements, a model of calculating various mε from porosity was established. By using the proposed model, we processed several wells with which the ADL data was acquired, the consecutive water saturation curves were calculated. Comparisons of predicted water saturation with irreducible water saturation, core derived results and the drill stem test (DST) data illustrate that this model was reliable. The advantage of this model was that it can be used to precisely calculate water saturation in any formations with various formation water salinity, whereas the conventional methods lost their role.