Characteristics of log responses and lithology determination of igneous rock reservoirs

The determination of the lithology of deep igneous rocks in the northern Songliao Basin in China has been found to be difficult because of insufficient core-analysis data and accurate descriptions of cuttings in the area. This paper presents a method for determining the lithology of these rocks. First, the igneous rocks are divided into six classes according to cores and cuttings in the area. Then, for each class, a statistical analysis is performed for 11 log data sets to determine their log characteristics. Finally, the different lithologies of the igneous rock reservoirs in the area are automatically determined using the maximum membership function rule of fuzzy mathematics. A comparison between the results obtained and the lithologic column obtained from cores or cuttings shows that this method gives good results for the determination of igneous rock lithology in the area.