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 lots of education where in actuality the Th/You ratio was utilized to identify new depositional ecosystem [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 (IA 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 gamma beam hobby regarding creation is not only related on the clay nutrients. Hence, although the natural gamma ray logs are generally a knowledgeable signs of the clay blogs, they need to be used in combination with warning [ten, 11]. The fresh mistakes throughout the estimate away from clay blogs away from wireline logs will be faster, if they’re calibrated up against the mineralogy study taken from cores. Multiple studies lead good correlations amongst the research-derived clay articles together with beliefs computed regarding changed absolute gamma beam record and its own spectral section studies because the anybody else did not assistance this reality. Such as, Heslop debated the altered sheer gamma beam diary provide good correlations on the X-beam diffraction analysis. Johnson and you can Linke , according to research by the cation replace capacity research from inside the Mackensie delta town, concluded that new altered absolute gamma ray strategy does deliver the credible clay contents. Unlike, Causey revealed your changed pure gamma ray record is actually many specific clay indication within his investigation, although it did overestimate the fresh new clay information when comparing to the new laboratory investigation. Jurado confirmed your altered absolute gamma beam and its own spectral portion analysis are of help and you may effective systems throughout the identity/quantification of one’s clay nutrients, because of their high and you www.datingranking.net/pl/dating-for-seniors-recenzja will low indication regarding the shale and you will clean zones, respectively. Other various studies have become accomplished utilising the integration of the new research, together with record-derived clay nutrient philosophy throughout the subsurface structures [18, 31,30,32,33,34].
The fresh new thorium in order to uranium (Th/U) proportion may differ with the sedimentary techniques and things and towards depositional ecosystem; for this reason, it can be utilized to distinguish the latest environments 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].