东海西湖凹陷平湖组Ⅲ型干酪根暗色泥岩生排烃模拟

为更真实地刻画烃源岩生排烃过程及为油气资源定量评价提供合理的关键参数，对东海陆架盆地西湖凹陷始新统平湖组Ⅲ型干酪根暗色泥岩开展了半开放体系下热压生排烃模拟实验研究。模拟结果显示，该暗色泥岩的生排烃过程主要包括初期缓慢生油阶段（R_o=0.5%~0.7%）、早期快速生排油阶段（R_o=0.7%~1.0%）、中期油裂解气阶段（R_o=1.0%~1.5%）、后期主生气阶段（R_o=1.5%~2.3%）及晚期生干气阶段（R_o>2.3%）。该烃源岩的排油门限（R_o）约为0.7%，其生气范围较宽（R_o=1.0%~3.0%），且在高—过热演化阶段仍具备较强的生气能力，是以生气为主的气源岩。通过对实验结果和样品生排烃特征的研究，建立了一套西湖凹陷平湖组Ⅲ型暗色泥岩生气与生排油过程及潜力评价的数学模型，可用于该区资源量计算。与封闭体系的高温高压黄金管热模拟实验相比，半开放体系下烃源岩热压生排烃模拟实验的累计产油率更高，也更接近实际地质情况，据此评价可使西湖凹陷具有更大的油气资源量。

Simulation of hydrocarbon generation and expulsion for the dark mudstone with Type-Ⅲ kerogen in the Pinghu Formation of Xihu Sag in East China Sea Shelf Basin

In order to finely describe the hydrocarbon generation and expulsion process of source rocks and provide reasonable key parameters for quantitative evaluation of oil and gas resources, we carried out a simulation research under semi-open system on hydrocarbon generation and expulsion for the dark mudstone with Type-Ⅲ kerogen in the Eocene Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin.The results show that the process of hydrocarbon generation and expulsion can be divided into five stages as follows, 1) R_o=0.5%-0.7%, when oil was generated slowly without expulsion; 2) R_o=0.7%-1.0%, when oil was generated and expelled rapidly; 3) R_o=1.0%-1.5%, when oil began to be cracked into hydrocarbon gas; 4) R_o=1.5%-2.3%, when gas generation predominated; and 5) R_o>2.3%, when only dry gas was generated.Oil expulsion threshold (R_o) of the source rock of this type is about 0.7% (R_o=0.7%), having a wide gas-window of R_o=1.0%-3.0%.So it can maintain relatively strong gas generation ability at high-and over-mature stages, belonging to gas-prone source rock.Following the study on experimental results and the characteristics of hydrocarbon generation and expulsion in samples, we established a set of mathematical models for the evaluation of the process and potential of gas generation and oil generation and expulsion of the dark mudstone with Type-Ⅲ kerogen in the study area.Compared with the thermal simulation experiment in a closed system, the cumulative yield of oil in the semi-open system is higher and closer to that under actual geological conditions.Accordingly, we may conclude that more oil and gas resources may exist in the Xihu Sag.