分散液态烃裂解气资源评价方法

Quantitative Assessment of Pyrolysis Gas Generated by Dispersed Liquid Hydrocarbon

分散液态烃裂解气资源评价涉及五方面内容,可概括为“五步法”的定量评价方法。步骤一：源内和源外液态烃的分配比例和数量研究。模拟实验及实际地质样品统计相结合的研究结果,烃源岩中滞留烃的数量可观,受有机质丰度、类型、演化程度、烃源岩岩性、物性以及与储集层的配置关系等因素影响。总体特征烃源岩排油率变化于20%~80%,以TOC 2%为界,排油率为50%上下;高TOC、类型优质的烃源岩排油率高。步骤二：源外分散液态烃的主要分布、富集区研究。通过数值模拟正演研究液态烃的优势运移通道及分布富集区;同时,通过热成因沥青的数量统计及分布、样品的荧光特征反演研究分散液态烃的分布富集区。步骤三：不同赋存状态液态烃裂解成气的转化率研究。模拟地质条件下碳酸盐岩、泥岩和砂岩中的分散液态烃裂解生气实验,反映碳酸盐岩、泥岩和砂岩对液态烃的裂解均有催化作用,作用强度依次减弱,主生气期对应的Ro值分别为1.2%~3.2%、1.3%~3.4%和1.4%~3.6%;超压抑制液态烃裂解生气,达到相同转化率温度滞后30℃左右。步骤四：研究区含油气系统研究：加强液态烃晚期规模生气和有效成藏的要素和关键时刻的分析。步骤五：分散液态烃裂解气的定量评价以及资源评估。以深层海相天然气成因研究为基础建立的分散液态烃“五步法”定量评价方法,实现了中国深层古老烃源岩源内分散液态烃裂解气、源外分散液态烃裂解气、古油藏裂解气、干酪根降解气的整体、系统评价。

The resource assessment of pyrolysis gas generated by dispersed liquid hydrocarbons involves 5 aspects, which can be summarized as ＂five steps methodology＂. The first step is to study the distribution ratio and amount of liquid hydrocarbon within and out of the source. The results of simulation experiments and statistical analysis on geological samples show that a considerable number of hydrocarbons has been retained in source rocks and is controlled by various factors, including organic matter abundance, type and evolution degree, source rock＇s lithology and source-reservoir allocation. The oil expulsion efficiency of different source rocks generally vary from 20% to 80%, averaging around 50% for source rocks with TOC lower 2%. The source rocks with high TOC generally have high oil expulsion efficiency. The second is to study the distribution of dispersed liquid hydrocarbon and its concentration areas. Forward modeling and inversion method were used to simulate the dominant migration pathway and distribution zones of liquid hydrocarbons. The distribution zones were analyzed through inversion methods including statistics on thermogenic asphalt and fluorescence characteristics of reservoir samples. The third is to study the conversion ratio of pyrolysis gas generated by liquid hydrocarbon of various occurrences. Simulation experiments of gas cracking from dispersive liquid hydrocarbons in carbonate, mudstone and sandstone show that these three minerals had catalytic effect on the cracking process of liquid hydrocarbons, and their effect decreased one by one. During the main gas generation periods, liquid hydrocarbons of the three minerals are 1.2%～3.2%, 1.3%～3.4% and 1.4～3.6% respectively. Overpressure could inhibit the process of gas generation. The experimental results at 200 MPa and 50 MPa show the mixture temperature lag is about 30℃. The fourth is the study of petroleum system in 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. The fifth is quantitative assessment and resource evaluation of pyrolysis gas generated by dispersed liquid hydrocarbon. The quantitative assessment method of ＂five steps＂, which is based on genetic method, has realized the integrated and systematic assessment of pyrolysis gas generated by dispersed liquid hydrocarbon inside and outside the source rocks, by paleo-reservoirs, and degradation gas generated by kerogen.