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 randki japan cupid 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 analysis anywhere between unmodified ray indexes and core-mentioned clay content material. Black colored network Gas creating well analysis activities, black colored upwards-directing triangle low-promoting well investigation products
Thickness versus GR regarding core types of the new Shurijeh Creation. Black colored circle Gas promoting well investigation products, and you can black upwards-directing triangle non producing really analysis items
Therefore, the values out of linear gamma beam, potassium, and you will thorium spiders was indeed modified, having fun with all the empirically derived low-linear change equations brought because of the Larinov , Clavier , Steiber , Dewan , or Bhuyan and you will Passey (all of the relationships is actually placed in Dining table step 1) to locate a quicker incorrect estimation regarding Shurijeh clay stuff
Just like the problems in the earlier in the day improvement generated a comparatively high variation on results, it is vital to get an empirical relationship into the clay blogs estimations within creation. 11.0 application. Found lower than is the gotten low-linear calibration relationships to the Shurijeh Development when it comes to an intellectual mode ranging from pure gamma ray list given that separate changeable plus the lab-derived lbs per cent clay based on the X-beam diffraction study given that based adjustable:
Contour 8 suggests the connection of lbs percent clay about XRD measurements of one another wells and you may modified natural gamma beam list playing with different equations plus very 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.