Log-Derived Cation Exchange Capacity of Shaly Sands: Application to Hydrocarbon Detection

Abstract

Hydrocarbon bearing shaly formations can be detected using cation exchange capacity (CEC) shaly sand models. Most CEC shaly sand models still depend on the laboratory measurement of 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 reservoir 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, lpekBassiouni (I-B) model that improve 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.Ipek-Bassiouni (I-B) Shaly Sand Model considers that electric current follows two type of path in shaly sand. One path represents current flow in free water and another path in bound water. The differentiation between these two paths is accomplished by using two different formation resistivity factors in free water and in bound water. The two formation resistivity factors are expressed using two cementation exponents for free water and bound water as well.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 a better hydrocarbon potential in the zone of interest.

Estimation of an Equivalent Shaliness Parameter Using Resistivity and Spectroscopy Logs: A Total Expansible Clay Approach

“…Modern shaly sand conductivity models can be grouped as follows: mono formation factor CEC models (Waxman and Smits, 1968;Juhasz, 1981;Clavier et al, 1984;Bassiouni, 1985, 1987;Lau and Bassiouni, 1989); dual formation factor CEC models (Ipek and Bassiouni, 2002;Kurniawan and Bassiouni, 2007); electrochemical models (Revil and Glover, 1997;Revil et al, 1998); and effective medium theory (EMT) models (Bruggeman, 1935;Hanai, 1960;Sen et al, 1981;Bussian, 1983;Myers, 1989;Sharma, 1990, 1992;Berg, 1996Berg, , 2007Johnson and Poeter, 2005). Whilst proponents of all models generally agree that the effective conductance of the clay mineral is a function of the counter-ion concentration, their arguments differ in the way the counter-ions are transported at low salinities.…”

Diagnosis of Ineffective Drilling Using Cation Exchange Capacity of Shaly Formations

“…In the case of real-time detection using MWD, the cation exchange capacity can be calculated from the perfect shale model (2) or the Ipek-Bassiouni (I-B) Shaly Sand Model (4) . …”

“…For this run, the cation exchange capacities are calculated using the Ipek-Bassiouni Shaly Sand Model (4) . For this run, the cation exchange capacities are calculated using the Ipek-Bassiouni Shaly Sand Model (4) .…”

“…In the application of this method, the cation exchange capacity can be estimated from log data using either the Ipek-Bassiouni (4) Shaly Sand Model or perfect shale (2) model.…”

Artificial neural networks workflow and its application in the petroleum industry

“…There are many methods available in the industry to calculate the water saturation; these include petrophysical evaluation models [7][8][9]. However, all these methods have many limitations and, more importantly, the input parameters to these models are often not readily available [10][11][12]. In particular, the presence of shales (low permeability layers) in the formation makes saturation prediction problematic using wireline log data.…”