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 comparison ranging from unmodified beam spiders and you can key-mentioned clay information. Black colored community Fuel producing really data items, black right up-directing triangle non-generating well analysis situations
Occurrence vs GR regarding core types of this new Shurijeh Development. Black system Gas generating really research situations, and you can black up-leading triangle non producing really data affairs
Thus, the costs of linear gamma ray, potassium, and thorium spiders were altered, having fun with each of the empirically derived non-linear alter equations introduced by Larinov , Clavier , Steiber , Dewan , otherwise Bhuyan and you can Passey (every dating is actually placed in Dining table step 1) to track down a shorter incorrect quote out-of Shurijeh clay blogs
As problems for the early in the day adjustment generated a fairly large difference into results, you should derive an enthusiastic empirical dating with the clay stuff estimations within this creation. eleven.0 application. Found less than ‘s the acquired non-linear calibration matchmaking towards Shurijeh Development when it comes to a rational function ranging from natural gamma beam list because the separate varying as well as the research-derived lbs per cent clay according to the X-ray diffraction research as depending adjustable:
Profile 8 suggests the connection off weight % clay throughout the XRD sized both wells and you can changed pure gamma ray index using some other equations along with extremely consolidated Larionov changes, 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 jak uЕјywaД‡ chatiw, 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.