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Attempting to calibrate the fresh core to log analysis, a simple low-linear regression dating is run in Matlab eight

Attempting to calibrate the fresh core to log analysis, a simple low-linear regression dating is 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 fresh new testing ranging from unmodified beam spiders and key-measured clay contents. Black system Gasoline promoting better analysis things, black colored upwards-pointing triangle low-creating really analysis products

Occurrence compared to GR regarding the core types of the fresh new Shurijeh Creation. Black circle Fuel promoting well studies affairs, and black colored upwards-leading triangle non producing well study points

Ergo, the prices away from linear gamma beam, potassium, and you may thorium indexes have been modified, using all the empirically derived non-linear transform equations introduced from the Larinov , Clavier , Steiber , Dewan , otherwise Bhuyan and Passey (the relationship was placed in Dining table 1) to locate a reduced incorrect quote off Shurijeh clay posts

Because the mistakes of past modifications generated a somewhat high difference on the performance, it is vital to derive an enthusiastic empirical dating on the clay content estimations within this development. eleven.0 software. Shown below is the obtained non-linear calibration relationships towards the Shurijeh Development in the way of an intellectual mode ranging from absolute gamma ray index due to the fact separate variable plus the research-derived lbs per cent clay according to the X-beam diffraction data due to the fact centered adjustable:

Shape 8 reveals the connection from pounds % clay on the XRD measurements of one another wells and you will modified natural gamma ray list playing with other equations as well as highly consolidated Larionov changes, 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 muddy matches zaloguj siД™ 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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