I-B Shaly Sand Model: Application to Hydrocarbon Detection

摘要

Hydrocarbon bearing shaly formations can be detected using cation exchange capacity (CEC) shaly sand models. Most CEC shaly sand models still depend on a laboratory measurement of the CEC value. In addition, these models use one value of formation resistivity factor which is a function of the rocks's cementation exponent. Using one formation resistivity factor in shaly sand reservoirs can result in overestimation of the water saturation, which in turn results in overlooking formations with hydrocarbon potential. This paper introduces a new CEC shaly sand model, Ipek-Bassiouni (I-B), that improves the definition of the formation resistivity factor used in shaly sand formations. This model can also calculate the CEC value directly from the well log data. The Ipek-Bassiouni (I-B) Shaly Sand Model considers that an electric current follows two types of paths in shaly sand. One path represents current flow in free water, and another path represents current flow in bound water. The differentiation between these two paths is accomplished by using two different formation resistivity factors in free water and bound water. The two formation resistivity factors are expressed using two cementation exponents for free water and for bound water. The validity of the model was checked using the cation exchange capacity measured from core samples and drill cuttings. Calculated CEC values display a good agreement with the measured CEC values. The estimated water saturations from the model indicate better hydrocarbon detection in the zone of interest.