Geochemical characteristics, forming conditions and resource evaluation of oil-cracking gas as exemplified by the platform area of the Tarim Basin.

Based on the geochemical characteristics of oil-cracking gas and kerogen-cracking gas revealed by simulation experiments and the chemical composition of natural gases in actual gas reservoirs, two kinds of natural gases with different relationships between C/C and C/C, C/C and C/C, C/C and 100×C/(C-C) were identified in the Tarim Basin, and proposed further by the authors. The relationship charts of C/C and C/C, C/C and C/C, C/C and 100×C/(C-C) can be used to effectively distinguish oil-cracking gas from kerogen-cracking gas. Petroleum geological analysis of the oil-cracking gas reservoirs showed that the distribution of oil-cracking gas is mostly related with deep-seated faults or faults with a large fault throw, and the burial depth of paleo-oil reservoir is relatively high; crude oil-cracking gas resources have been evaluated by using both forward and inversion methods. The plots of C/C vs. C/C, C/C vs. C/C, and C/C vs. 100×C/(C-C) were used to distinguish between oil-cracking gas and kerogen-cracking gas, and estimate the mixed ratios of the two kinds of natural gases in the main gas reservoirs of the platform area. [ABSTRACT FROM AUTHOR]