Quantitative assessment of cracking gas generated by dispersed liquid hydrocarbon

Abstract

The resource assessment of cracking gas generated by dispersed liquid hydrocarbons involves 5 aspects. Firstly, the study on the distribution ratio and amount of liquid hydrocarbon within and out of the source rock, the oil expulsion efficiency of different source rocks varied from 20% to 80%, and the data is less than 50% for source rocks with TOC lower 2% and more than 50% for those with high TOC (higher than 2%), which means that the source rocks with high organic matter abundance and excellent type will have high oil expulsion efficiency. Secondly, the dominant migration pathway and distribution zone of the liquid hydrocarbons were conducted by numerical modeling while the distribution zone could also be tested through inversion method including statistics on thermogenic bitumen and fluorescence characteristics of reservoir samples. Thirdly, the conversion ratio of cracking gas generated by liquid hydrocarbon of various occurrences should be known. The main gas generation periods of liquid hydrocarbon mixed with carbonate, mudstone and sandstone are 1.2%-3.2%, 1.3%-3.4% and 1.4%-3.6% respectively. Moreover, overpressure could inhibit the process of gas generation. The mixture temperature lag is about 30°C while comparing the experimental results of 200Mpa and 50Mpa. Fourthly, the study of petroleum system of the studied area, especially the analysis of key factors and critical moments for the late scale formation and accumulation of natural gas of the liquid hydrocarbon cracking gas. Fifthly, quantitative assessment and resource evaluation of cracking gas generated by dispersed liquid hydrocarbon. The quantitative assessment method of “five steps”, which is based on genetic method, realized the integrated and systematic assessment of cracking gas generated by dispersed liquid hydrocarbon inside and outside the source rock, by paleo-reservoirs, and degradation gas generated by kerogen.