where I _{diary denotes the total natural gamma ray/potassium/thorium reading in the zone of interest, A minute 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 studies where Th/You proportion was utilized to identify this 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 fresh new gamma ray craft on the formation is not entirely associated to the clay nutrients. For this reason, whilst pure gamma beam logs are often a knowledgeable evidence of your own clay posts, they need to be used in combination with caution [ten, 11]. The fresh new errors on quote off clay content out-of wireline logs will be less, when they calibrated resistant to the mineralogy investigation obtained from cores. Several studies lead a great correlations amongst the research-derived clay material as well as the opinions determined in the modified sheer gamma ray record and its spectral areas analysis because the others failed to help this reality. Particularly, Heslop debated your modified pure gamma beam record provide a great correlations on X-beam diffraction study. Johnson and you can Linke , according to research by the cation change capacity data during the Mackensie delta urban area, determined that brand new changed sheer gamma ray means does deliver the reliable clay content material. In lieu of, Causey discovered that the altered pure gamma beam journal are the absolute most perfect clay indicator inside the studies, although it performed overestimate this new clay content material when compared to brand new research investigation. Jurado confirmed the changed absolute gamma ray and its particular spectral areas research are useful and productive tools regarding the personality/measurement of your clay nutrition, due to their large and reduced readings regarding shale and you may clean zones, correspondingly. Most other some research has already been achieved using the consolidation off new laboratory, plus the diary-derived clay mineral values on subsurface structures [18, 31,29,thirty-two,33,34].

The fresh thorium to help you uranium (Th/U) ratio varies on sedimentary processes and datingranking.net/pl/be2-recenzja/ you will issues together with for the depositional environment; ergo, it can be utilized to acknowledge the fresh new environments and operations

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].