Trying to calibrate the brand new center so you’re able to log study, a straightforward low-linear regression relationship is actually run in Matlab seven

Trying to calibrate the brand new center so you’re able to log study, a straightforward low-linear regression relationship is actually run in Matlab seven

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 new testing between unmodified ray spiders and you can center-measured clay content. Black community Energy generating better data activities, black right up-leading triangle non-creating well investigation factors

Density compared to GR on center types of this new Shurijeh Creation. Black colored system Energy creating well analysis facts, and you can black upwards-directing triangle low creating better studies points

Hence, the costs out of linear gamma beam, potassium, and you may thorium indexes was in fact modified, playing with each one of the empirically derived low-linear transform equations introduced from the Larinov , Clavier , Steiber , Dewan , or Bhuyan and Passey (all dating was listed in Table step 1) to track down a smaller incorrect estimation regarding Shurijeh clay content

Once the mistakes of the earlier in the day variations made a comparatively highest distinction for the efficiency, you will need to obtain an empirical matchmaking into clay blogs estimations inside creation. 11.0 application. Revealed lower than ‘s the acquired non-linear calibration relationship towards the Shurijeh Development in the form of a mental mode ranging from natural gamma ray list since the independent variable as well as the lab-derived pounds percent clay based on the X-ray diffraction studies as centered changeable:

Profile 8 reveals the partnership regarding pounds % clay on XRD sized each other wells and you can altered absolute gamma ray list using some other equations as well as extremely consolidated Larionov alter, 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.