where I _{journal denotes the total natural gamma ray/potassium/thorium reading in the zone of interest, A min shows the average natural gamma ray/potassium/thorium response of the clean (clay free) zone, A maximum indicates the average natural gamma ray/potassium/thorium response of the pure clay zone .}

There are many knowledge where in fact the Th/You ratio was utilized to understand new depositional environment [39, 40]

However, some variations of the above-mentioned parameters can induce large effects on the log responses, so that the linear equation, called gamma ray index (I_A in Table 1 when A is the gamma ray log readings), gives an overestimate of the clay contents in the reservoirs. Thus, the linear gamma ray index should be modified using one of the empirically derived non-linear calibration equations such as those introduced by Larinov , Clavier , Steiber , Dewan , or Bhuyan and Passey (Table 1). These transforms are all in the non-linear form except for that of Bhuyan and Passey , which is developed based on the assumption that the estimation of weight percent clay can be modified by multiplying the gamma ray/potassium/thorium index by an empirical correction factor, i.e., C. This factor is basically determined from the weight percent clay content of average shale adjacent to the zone of interest , and commonly ranges from 50 to 70 [10, 13, 14]. Accordingly, the rock can be differentiated as clean, if the calculated clay content is less than 10%; shaly sand if it ranged from 10 to 33% and if it is more than 33%, it is considered to be shale .

The latest gamma beam passion regarding the development is not entirely related into the clay nutritional elements. Ergo, although the natural gamma ray logs are usually an educated symptoms of your clay articles, they need to be used with warning [10, 11]. The new problems regarding the quote out-of clay posts off wireline logs are going to be shorter, if they are calibrated resistant to the mineralogy analysis extracted from cores. Multiple training introduced a great correlations between your research-derived clay material as well as the thinking computed on the changed pure gamma beam record and its spectral portion study just like the anyone else failed to assistance this particular fact. Such as for example, Heslop argued that altered sheer gamma beam log bring an excellent correlations to your X-ray diffraction analysis. Johnson and you can Linke , according to research by the cation replace strength research during the Mackensie delta town, determined that the changed pure gamma ray means do supply the reliable clay contents. As opposed to, Causey discovered the changed absolute gamma beam journal was the absolute most direct clay indication within his investigation, although it did overestimate the fresh clay information when compared to new lab study. Jurado affirmed your altered sheer gamma ray as well as spectral parts studies are useful and energetic tools about identity/measurement of the clay nutrients, for their higher and low readings from chatroulette the shale and you will brush areas, correspondingly. Almost every other certain research has been accomplished by using the integration away from this new lab, while the record-derived clay nutrient beliefs in the subsurface structures [18, 30,29,thirty-two,33,34].

The fresh thorium to help you uranium (Th/U) ratio may vary with the sedimentary process and you will factors along with into depositional ecosystem; for this reason, it can be utilized to recognize this new surroundings and processes

The potassium and thorium concentrations are not only linked to the clay content, but also to the changes in the weathering regime of sediments in the source lands [35,36,37]. The Th/U ratios in the sedimentary rocks range from less than 0.02 to more than 21 . This ratio in the continental, oxidizing environment, weathered soils are above 7, while the most marine deposits, gray and green shales, and graywackes have ratios that are > 2 and < 7. However, in marine black shales and phosphates, it reaches below 2 . Schlumberger has developed several cross-plots to estimate the clay mineralogy in the subsurface formations in the absence of laboratory data. Many authors used them to recognize different clay minerals types [18, 20, 42, 43].