TShale is the most common lithology encountered in drilling for oil and gas. Shale formations often cause bit performance and wellbore stability problems. This paper introduces a cation exchange capacity model for perfect shale based on Waxman-Smits' shaly sand petrophysical model. The validity of the model is checked against measured cation exchange capacity. The determination of cation exchange capacity using this modified model and common log data has shown potential for identifying ineffective drilling in shale. Data collected under controlled conditions is needed, however, to optimize the proposed approach. Knowing the location and the characteristics of these shales allows for corrective actions either during drilling, if LWD data is used, or on future offset wells.
展开▼
