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.
The fresh assessment between unmodified beam indexes and center-mentioned clay content. Black network Gasoline generating well investigation issues, black up-pointing triangle low-generating well study activities
Density versus GR about key examples of the brand new Shurijeh Development. Black colored network Gas generating better investigation situations, and black colored up-pointing triangle low promoting better investigation issues
For this reason, the costs off linear gamma ray, potassium, and you can thorium spiders have been altered, playing with each of the empirically derived non-linear change equations introduced of the Larinov , Clavier , Steiber , Dewan , or Bhuyan and you may Passey (every matchmaking is placed in Desk 1) to obtain a faster incorrect estimation regarding Shurijeh clay content
Because the mistakes regarding the prior improvement generated a relatively large distinction into the efficiency, you will need to get a keen empirical relationship with the clay stuff estimations inside development. 11.0 software. Found below is the gotten low-linear calibration relationships towards the Shurijeh Creation in the form of a mental means ranging from pure gamma ray list since separate variable plus the research-derived lbs % clay in line with the X-ray diffraction data once the dependent changeable:
Contour 8 reveals the relationship regarding pounds percent clay in the XRD measurements of both wells and you can altered natural gamma beam directory having fun with some other equations together with kody promocyjne chatstep extremely consolidated Larionov transform, 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 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.
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