Attempting to calibrate the new center so you’re able to log study, a straightforward low-linear regression relationships are run in Matlab eight

Attempting to calibrate the new center so you’re able to log study, a straightforward low-linear regression relationships are run in Matlab eight

Table 4 summarizes the pertinent well data babel 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 brand new evaluation anywhere between unmodified beam spiders and center-mentioned clay articles. Black colored circle Gas producing really studies activities, black colored right up-directing triangle non-producing better research things

Occurrence versus GR from the center types of the newest Shurijeh Formation. Black system Gasoline generating well data circumstances, and you will black colored upwards-directing triangle non generating well investigation facts

Thus, the values out of linear gamma beam, potassium, and you may thorium spiders was indeed modified, having fun with each of the empirically derived non-linear transform equations lead from the Larinov , Clavier , Steiber , Dewan , otherwise Bhuyan and you will Passey (all the matchmaking is actually listed in Desk step one) to acquire a less incorrect quote away from Shurijeh clay content

While the mistakes of earlier in the day variations generated a fairly highest differences for the overall performance, it is critical to obtain a keen empirical dating toward clay stuff estimations within this development. eleven.0 software. Revealed lower than is the received non-linear calibration matchmaking on the Shurijeh Creation in the way of an intellectual means between natural gamma ray index just like the independent variable together with laboratory-derived lbs % clay according to the X-beam diffraction analysis as built changeable:

Contour 8 suggests the partnership out of pounds per cent clay on XRD size of one another wells and changed sheer gamma ray directory playing with more equations together with extremely consolidated Larionov change, 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.

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