Table 4 summarizes the pertinent well data used for calculation of the gamma ray, potassium, and the thorium indexes. Their comparison with the actual measured clay content from the XRD analysis (Fig. 5) showed that the unmodified gamma ray, potassium, thorium indexes calculated from the linear Eq. (1) provided wide overestimation of the Shurijeh clay content, which leads eventually to the misestimating of the original hydrocarbon in place and reserves. According to the Shurijeh age (Early Cretaceous), Larinov calibration for highly consolidated formations was used and based on the data in Fig. 6, ? sh in Dewan equation which is corresponding to the highest gamma ray reading considered to be 2.75 g/cc units. The C factor in the Bhuyan–Passey modification was considered to be 60 for the Shurijeh Formation after measuring the clay contents of reference adjacent shale in many surface samples. The estimated clay content from modified gamma ray, potassium, and thorium indexes are given in Table 5.
This new testing anywhere between unmodified beam indexes and you may center-counted clay articles. Black colored network Fuel generating well study issues, black upwards-leading triangle low-producing well studies facts
Occurrence against GR regarding center samples of the new Shurijeh Formation. Black community Gas producing better analysis activities, and black colored up-pointing triangle low producing well study issues
For this reason, the values regarding linear gamma beam, potassium, and thorium indexes was indeed altered, playing with all the empirically derived low-linear alter equations produced because of the Larinov , Clavier , Steiber , Dewan , or Bhuyan and you will Passey (all of the relationships was listed in Table step one) to find a quicker erroneous estimation from Shurijeh clay content
Once the errors of this prior modifications produced a fairly higher huge difference into efficiency, it is important to get an enthusiastic empirical dating towards clay blogs estimations inside development. eleven.0 software. Found below is the obtained low-linear calibration dating to the Shurijeh Creation in the way of an intellectual function anywhere between natural gamma beam index due to the fact independent adjustable together with lab-derived lbs percent clay in accordance with the X-beam diffraction studies as situated changeable:
Figure 8 reveals the connection out of lbs percent clay on the XRD sized one another wells and you can changed absolute gamma ray list using additional equations also highly consolidated Larionov change, Clavier et al
The natural gamma ray index was chosen for running the regression analysis due to the stronger correlation coefficient in compare to the potassium or thorium indexes, with the core clay contents in both wells. The unique feature of new equation is to calculate the clay content of less than 100% with a given IGR of 1.0, while all other previous modifications give clay content of 100% for such IGR value. The assumption used in developing the non-linear relationships was based on the fact that the entire radioactivity is not due to the clay minerals only. The goodness of agreement and the reliability of the regression equation were then both verified by a correlation coefficient of 0.992 upon application on some other core samples from another wells drilled in the Shurijeh Formation. It is clear from the data in Fig. 7 that the core data, verify both the very low and the medium range of clay contents, estimated from the non-linear empirical relationship. The average percent relative error was also minimized adventist singles to 11.4%. Due to the statistical bias of comparing data samples with very different sizes and variances (76 samples versus 11 samples), the error cannot be reduced further. , Steiber, Dewan, Bhuyan–Passey and the empirical transforms. The clay content was also estimated from the potassium and thorium indexes using the empirical non-linear calibration (Table 5) and a comparison of average percent relative errors for different equations has been shown in Fig. 9.
