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 newest assessment ranging from unmodified ray indexes and key-measured clay content material. Black community Gas generating well analysis things, black colored upwards-pointing triangle low-producing really analysis affairs
Thickness vs GR from the center examples of the brand new Shurijeh Formation. Black circle Fuel producing well analysis factors, and you will black colored upwards-pointing triangle non promoting better study situations
Ergo, the values regarding linear gamma ray, potassium, and thorium spiders were changed, having fun with all the empirically derived non-linear change equations lead by Larinov , Clavier , Steiber , Dewan , or Bhuyan and you can Passey (all the dating is actually placed in Desk 1) to get a quicker erroneous estimate out-of Shurijeh clay content
Given that mistakes from the previous changes made a comparatively large distinction with the efficiency, it is essential to obtain an enthusiastic empirical matchmaking into the clay content estimations within this creation. 11.0 app. Revealed lower than is the gotten low-linear calibration relationship to the Shurijeh Creation in the way of a rational form ranging from sheer gamma ray index while the separate adjustable additionally the lab-derived lbs percent clay in line with the X-ray diffraction studies as the oriented adjustable:
Contour 8 reveals the partnership away from pounds % clay regarding the XRD size of both wells and altered absolute gamma beam directory playing with other equations in addition to very 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 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 http://www.datingranking.net/pl/good-grief-recenzja 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.
