The Fractured Carbonate Identification And Quantitative Evaluation

In the distribution of the world’s oil and gas fields, carbonate reservoir occupies a very important position, The oil and gas fields of the carbonate reservoir layer often offer large and high output, and also easy to form large oil and gas fields, many of the world’s major oil and gas fields are developed in carbonate rock reservoir, according to previous statistics, The reserves of oil and gas which have been found in carbonate reservoirs are nearly half of the world’s total reserves of oil and gas and the production accounted for more than60%of the global output, The seven well whose daily output reaches more than10000t are mainly developed in carbonate rocks, in China, we also found some large or medium-sized gas fields, such as the Ordovician oil and gas reservoirs, Sichuan gas field, large and medium-sized gas fields are also found in the Ordos Basin carbonate strata.The reservoir lithology of Puguang gas field is mainly carbonate, the main difficulties are as follows:(1) the carbonate reservoir lithology is complex,so the general conventional logging data is difficult to distinguish between different lithologies.(2)the identification of cracks, as the logging response characteristics of fractured reservoirs do not have strong regularity, it is difficult to accurately identify them using conventional logging curve.(3) the determination of the parameters of the reservoir characterization, because the study area are reef dual media reservoir, the spatial structure of reservoir is very complex,the logging response characteristics is not obvious, it is difficult to calculate the heterogeneity parameters of the reservoir.This article disputes the Puguang carbonate regional characteristics,gives qualitative identification and quantitative description of the cracks, and finally forms a interpretation software which is suitable for the Puguang fracture identification and quantitative description. Here is the main research methods:(1) on the basis of the geological characteristics of the Puguang gas field, cores and thin data analysis has been used for the analysis of lithology and lithological characteristics of the area, then recognizes the carbonate diagenesis, the reservoir physical properties of the region and electricity and other basic geological features. In addition, we makes in-depth study of the fracture development in the region on the basis of the analysis of the crack occurrence and the filling of the Puguang gas field,in the end,we also make a systemly statistics of these cracks.(2) the conventional logging response analysis and imaging logging response analysis of all these wells,using the reconstructed curve to predict fracture development, the establishment of a comprehensive probabilistic fracture identification model based on multi-feature fusion,analysis4non-fractured factors (A:The elimination of the impact of borehole collapse; B:the elimination of the effects of high porosity; C:the elimination of argillaceous impact; D:the elimination of the impact of the dense layer) and we further improve the crack qualitative recognition. The cracks qualitative identification rate finally reaches80%.(3) Human-computer interaction has been used to extract fracture parameters from the imaging logging (fracture length, fracture density, fracture apparent porosity).Using multiple linear curve fitting between the fracture parameters extracted from the imaging data and the well’s conventional curve, and then we get the non-imaging wells fracture parameters.(4) Establish a suitable software for the qualitative identification and quantitative description of the cracks in Puguang.