Shiyou shiyan dizhi (May 2021)
A calculation method for the efficiency of hydrocarbon expulsion based on parameter-diagram of source rock pyrolysis
Abstract
The efficiency of hydrocarbon expulsion acts as a key geological factor for the study of hydrocarbon expulsion of conventional oil and gas, also, it indicates the enrichment degree of unconventional oil and/or gas. Based on the method of recovering the original hydrocarbon generation potential, a method according to pyrolysis chart was proposed in this paper. A classic diagram for classifying organic matter types based on hydrogen index (IH) and maximum pyrolysis peak temperature (Tmax) was introduced in this study. The dividing line of organic matter type and the maturity trend line were evenly interpolated and gridded. The IH and Tmax data were plotted into the chart, and then traced to the left along the type line to the intersection point of maturity line Ro=0.2% as the original value of hydrocarbon generation index, thus, the hydrocarbon expulsion efficiency can be calculated. Based on the results of 66 source rock samples from the well BYHF1 of Biyang Sag, the relationship between hydrocarbon expulsion efficiency and characteristics of organic matter (ATM) was studied. In addition, the correlation between hydrocarbon expulsion efficiency and shale oil enrichment degree was studied. The results indicated that the hydrocarbon expulsion efficiency and ATM characteristics of organic matter obtained by the pyrolysis chart method were more regular than those obtained by the artificial assignment method, and it had a higher consistency with the enrichment degree of shale oil (OSI). The calculation process and results will not to be negative value or hydrocarbon expulsion efficiency greater than 100%. Therefore, it is reasonable and feasible to calculate hydrocarbon expulsion efficiency by the pyrolysis chart method, which is a complement to the original hydrocarbon generation potential recovery method.
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