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.
New review ranging from unmodified beam indexes and center-counted clay material. Black colored system Gas producing better analysis affairs, black upwards-directing triangle low-generating well analysis points
Density vs GR throughout the key types of new Shurijeh Formation. Black colored community Gas creating well investigation points, and you may black colored upwards-pointing triangle non generating well analysis factors
Ergo, the costs out-of linear gamma beam, potassium, and you will thorium indexes were altered, using each one of the empirically derived non-linear alter equations lead by the Larinov , Clavier , Steiber , Dewan , przykЕ‚ady profili mexican cupid otherwise Bhuyan and you will Passey (all of the relationships try placed in Table step one) to obtain a quicker erroneous quote of Shurijeh clay content
Because the problems in the earlier variations made a fairly high variation into the show, it is essential to obtain a keen empirical relationship with the clay stuff estimations in this creation. 11.0 application. Found lower than ‘s the received low-linear calibration relationship with the Shurijeh Formation when it comes to an intellectual setting ranging from absolute gamma beam directory because independent adjustable and laboratory-derived weight per cent clay in accordance with the X-ray diffraction data because the created variable:
Contour 8 reveals the relationship out-of lbs per cent clay in the XRD sized both wells and you can changed sheer gamma beam index playing with additional equations in addition to extremely consolidated Larionov transform, Clavier ainsi que 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 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.