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Well logging is the practice of making a detailed record of the geologic formations penetrated by the well. The key purpose of well logging is to obtain petrophysical properties of reservoirs such as porosity, permeability, hydrocarbon saturation etc., for hydrocarbon exploration. Logs also tell us about the fluids in the pores of the reservoir rocks. Petrophysical parameters such as effective porosity (Φ), water saturation (Sw), formation water resistivity (Rw), hydrocarbon saturation
(So) and formation resistivity (Rt) is evaluated by using the well log data. In the present study, an attempt has been conducted to describe the application of various open-hole logging tools such as gamma ray, sonic, resistivity and calliper logging tools to determine the petrophysical properties of Lake Beds. The present study portrays the interpretation of well log data using the open hole logs in parts of Rukwa Basin. Well log analysis has revealed a range of formation water resistivity (Rw) of 0.0032 Ω-m throughout the well indicating the presence of water-bearing sands in the Lake Beds. Based on Logs (GR log mostly) the Lake Beds were zoned into
6 zones; named A, B, C, D, E, & F in Galula.1
The six zones are identified by using logs at the depth of (7.8 - 256) m, (256 – 354.8) m, (354.8 –
461.5) m, (461.5 – 554.1) m,(554.1- 702.5) m, & (720.5 – 959.2) with average shale volume of
(27% - 46.1%), average porosity (10.6% - 17.5%), average water saturation of (22.2% - 33.6%) and average permeability of (0.34mD – 8.6mD) .
In both wells Ivuna.1 and Galula.1 the Lake Beds succession in Rukwa basin revealed through this study to have promising porosity for Gas accumulation. However, these zones are found in a very shallow depth with low permeability. |
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