Wanting to calibrate this new key to diary studies, a simple low-linear regression dating are run-in Matlab eight
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 new comparison between unmodified beam spiders and key-measured clay contents. Black circle Energy promoting better data products, black colored upwards-pointing triangle non-creating better analysis affairs
Occurrence vs GR from the core examples of this new Shurijeh Creation. Black system Gas generating well investigation situations, and black upwards-directing triangle low producing really http://www.datingranking.net/pl/maiotaku-recenzja/ investigation points
Ergo, the values out-of linear gamma ray, potassium, and you may thorium indexes was basically changed, having fun with each of the empirically derived low-linear alter equations introduced from the Larinov , Clavier , Steiber , Dewan , otherwise Bhuyan and you can Passey (all the relationships are listed in Desk 1) to acquire a smaller erroneous quote from Shurijeh clay content
Once the problems of this earlier in the day variations made a comparatively high differences towards the efficiency, it is critical to get an empirical dating towards the clay blogs estimations within this creation. 11.0 app. Shown less than is the obtained non-linear calibration matchmaking to the Shurijeh Formation when it comes to a rational means anywhere between pure gamma ray directory once the separate adjustable together with lab-derived weight per cent clay according to the X-beam diffraction data due to the fact situated adjustable:
Figure 8 shows the partnership out of weight percent clay about XRD size of each other wells and changed absolute gamma beam directory using some other equations along with very consolidated Larionov transform, Clavier mais aussi 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.