【作者】 程付启；

【导师】 金强；

【作者基本信息】 中国石油大学 ， 地质资源与地质工程， 2007， 博士

【摘要】 天然气具有来源广、分子小、流动性强等特点,不同来源的天然气易于向同一圈闭中充注成藏,气藏形成之后天然气又会不停地向外散失。确定多源充注气藏中天然气的来源及混合比例,阐明天然气散失的地球化学行为,是天然气成藏研究亟待解决的科学和实际问题。为此,综合利用天然气地质理论和地球化学方法,开展了天然气藏多源充注与散失过程的示踪研究。天然气藏多源充注示踪,首先要进行成藏条件与天然气特征分析,确定混源气的类型;然后根据天然气生成模拟与采样分析,建立端元气地球化学模型;并根据天然气混合过程及特征,构建混源气混合比例与母质成熟度计算模型;最后利用混源气地化参数确定混合比例及母质成熟度,并进行成藏分析以确定结果的正确性。根据示踪结果,克拉-2气田晚期充注天然气>90%,靖边奥陶系气藏下古油型气占16%~78%,乌参1井天然气70%源自Ⅲ型有机质,卧龙河嘉陵江组天然气中侏罗系泥岩贡献量约60%,丰深1井天然气54%左右源自Ⅰ型有机质,这些结果解决了天然气成藏研究的关键问题。天然气不同组分及同位素分子之间散失速率的差异,是散失过程中天然气组分、同位素分馏的原因。分别以Fick定理和Henry定律为依据,建立了扩散、溶解过程中天然气组分、同位素分馏模型,实现了藏内天然气散失的定量示踪。例如,扩散导致苏里格气田CH4含量降低1.08%、δ13C1增加1.12‰,溶解使威远气田CO2含量降低14.79%、烃类气体含量增加、δ13C1仅增加0.09‰,计算结果有助于追索气源、恢复气藏演化过程等。通过天然气瞬时和累计散失量计算,结合储量和源岩生气史,恢复了天然气的充注过程,实现了充注-散失过程定量反演。柴达木盆地东部生物气以扩散散失为主,充注-散失过程是控制生物气聚集的重要因素,提出的相对散失量可以评价气藏充注-散失过程,相对散失量<0.6有利于天然气聚集,否则不利。通过影响生物气充注、散失的地质因素分析,认为涩北、台南区块最利于生物气聚集,伊台、驼盐、涩-聂、霍达区块次之,南-哑和南部斜坡不利于生物气聚集。更多还原

【Abstract】 Mixed-gases reservoirs in which natural gas came from different source kitchens are prevalent in gas-bearing basins. It is necessary to identify mixed-gases and calculate mixed ratio of its end-member gases for forecasting resources and distribution of natural gas. Losing is inherent in natural gas accumulated in reservoirs. Gas components and isotopic compositions would change when natural gas loses from reservoirs. Investigating geochemistrical characteristics of losing gas is of importance in natural gas exploration.An investigation method of charging mixed-gases in reservoirs was brought forward, which is made up of following steps: 1) analyzing geological conditions and natural gas characteristics, to identify the source-mixed gas and its end-members, 2) adopting geochemistrical data of natural gas produced from laboratories and sampled from gas fields, to find quantitative relationships of identifying parameters of end-member gases and their thermal maturities, 3) establishing quantitatively identification mode of mixed-gases, based on physical change laws of mixing gases, and 4) using the results gained from the above 3 steps, to analyze formation process of mixed-gases reservoir. Some typical mixed-gases reservoirs were investigated by the method. The result shows that more than 90% natural gas in Kela-2 gas field charged in the Kuche period, 16%~78% of natural gas in Jingbian gas field is the Lower Paleozoic oil-type gas, 70% natural gas in Wucan-1 well came from type III organic material, the percentage of natural originated from the Jurassic is 60% in Jialingjiang gas reservoir of Wolonghe gas field, and 54% natural gas in Fengshen-1 well came from type I organic material.Accumulated gas would lose ceaselessly by diffusing through cap rock and (or) dissoluting in formation water. The difference of losing velocities among various gas components/molecules with different isotopes results in fractionations of component and isotopic compositions in natural gas. Based on the Fick law and the Herry law, diffusion and dissolution fractionation modes were established respectively. According to the diffusion fractionation mode, CH4 in Sulige gas field has decreased 1.08 percent, whileδ13C1 increased 0.112 percent because of natural gas losing by diffusing from reservoir. According to the dissolution fractionation mode, CO2 in Weiyuan gas field has decreased 14.79%, while CH4 increased 13.97% because of natural gas losing by dissolving in formation water.With mass of gas losing from and reserved in reservoir now, mass of gas charged into reservoir could be known, and then charge-losing history of natural gas reservoirs could be rebuilt. Biogas in eastern Chaidamu Basin has been losing from reservoirs mainly by diffusing. Distribution and enrichment of biogas in the area are controlled by the charge-losing balance of biogas. After investigating on charge-losing history of biogas reservoirs in eastern Chaidamu, a parameter of gas losing ratio was put forward for evaluating the charge-losing process of natural gas reservoir. According to the biogas losing ratio from reservoirs in eastern Chaidamu, charge-losting process is advantageous in accumulating natural gas when gas losing ratio is less than 0.6, while the process is disadvantageous when the ratio is more than 0.6. According to the geological factors that control charge-losing biogas in reservoirs eastern Chaidamu, geological conditions of Sebei and Tainan sections are most advantageous in accumulating biogas, geological conditions of Yitai, Tuoya, Senie and Huoda less advantageous than that of Sebai and Tainan, and Nanya section disadvantageous in accumulating biogas.更多还原