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为适应东部盆地向深层—超深层勘探的需求,通过歧口凹陷沙河街组典型原油的裂解生气模拟实验,采用原油裂解生烃动力学特征研究深层烃类流体相态变化规律。结果表明:原油裂解气生烃动力学可以方便地研究地质条件下原油裂解程度,进而判断地下油气相态的理论深度极限。在固定频率因子A=10~(14)S~(-1)前提下,渤海湾盆地歧口凹陷沙河街组原油裂解成C_1—C_5的活化能分布在250~270kJ/mol之间,平均活化能E_0=255.47kJ/mol,高于海相原油的245kJ/mol(59kCal/mol)。在同等升温速率条件下,其裂解生气路径与西部海相原油存在明显差异。以歧口凹陷地层沉积埋藏史确定的热史路径进行动力计算结果显示,歧口凹陷深层单一液相原油存在的理论深度极限为5 700m,凝析油气存在的理论深度极限为6 700m。结合歧北次凹和滨海具体地质条件进行油气藏相态演变过程分析,结果表明:在实际地质条件下,干酪根的裂解生气和更深部气源的充注气侵,使得原有油藏提前达到极高的气油比,纯液相原油提前消失。油气运移到浅部过程中受温—压条件的变化,导致了油气的分异和相态转换。温度和时间决定的生烃效应是深层油气相态的内因,在具体分析单个油藏相态时,不仅要考虑油气来源、组成、油气成藏过程,尤其还要注意后期构造活动造成的油气调整改造,这些是后期油气相态分异转化的外因。
In order to meet the need of deep-ultra deep exploration in the eastern basin, through the simulation experiments of typical crude oil cracking in the Shahejie Formation in the Qikou Depression, the variation law of the phase state of deep hydrocarbon fluids was studied based on the kinetics of hydrocarbon generation. The results show that the hydrocarbon generation kinetics of crude oil pyrolysis gas can be used to study the extent of crude oil cracking under geological conditions and to determine the theoretical depth limit of the underground hydrocarbon phase. Under the fixed frequency factor of A = 10 ~ (14) S ~ (-1), the activation energy of cracking C_1-C_5 of Shahejie Formation in the Qikou Depression of Bohai Bay Basin ranges from 250 to 270 kJ / mol, with an average activation E_0 = 255.47kJ / mol, which is higher than 245kJ / mol (59kCal / mol) of marine crude oil. Under the same heating rate, there is a significant difference between the cracked gas path and the western marine oil. Based on the thermal history path determined by the sedimentary burial history of Qikou sag, dynamic theoretical calculation shows that the theoretical depth limit of deep single liquid crude oil in Qikou sag is 5 700 m, and the theoretical depth limit of condensate hydrocarbon is 6 700 m. According to the analysis of the evolution process of oil and gas phases, the evolution process of oil and gas phases is analyzed. The results show that under the actual geological conditions, kerogen pyrolysis and gas influx from deeper gas sources make the existing reservoirs advance To achieve high gas-oil ratio, pure liquid crude oil disappear ahead of schedule. The changes of temperature and pressure conditions during the migration of oil and gas into shallow parts lead to the differentiation and phase transition of oil and gas. The hydrocarbon generation effect determined by temperature and time is the internal cause of the deep phase of oil and gas. When analyzing the phase state of a single reservoir, not only the source and composition of the oil and gas, but also the process of oil and gas accumulation should be considered. In particular, Transformation, these are the external causes of late phase oil and gas phase transformation.