鄂尔多斯盆地上古生界准连续型气藏气源条件

Gas source conditions of quasi-continuous accumulation of the Upper Paleozoic in Ordos Basin

曹青 赵靖舟 付金华 姚泾利 刘新社 赵会涛 侯云东 范立勇

Cao Qing Zhao Jingzhou Fu Jinhua Yao Jingli Liu Xinshe Zhao Huitao Hou Yundong Fan Liyong

通过鄂尔多斯盆地上古生界气源条件的综合分析,确定优质烃源岩是控制致密砂岩大气田形成分布的主要因素,并结合试气结果分析致密砂岩大气田形成的生气强度下限。首先对鄂尔多斯盆地上古生界烃源岩的厚度、有机碳含量和热演化程度等参数进行对比;接着在类比分析的基础上计算求取生气强度,并将其与试气成果结合进行综合分析。气源条件分析结果显示,鄂尔多斯盆地上古生界烃源岩品质好、分布广、热演化程度高,其生气强度介于10×10~40×10 m/km,具有高强度、大范围的供气特点;盆地西部生气强度介于10×10~20×10 m/km,而盆地东部生气强度相对较高,多大于16×10 m/km。综合分析认为:优质烃源岩是形成致密砂岩大气田的主要因素之一,从宏观上控制了鄂尔多斯盆地上古生界致密砂岩储层内气、水的空间分布状态;由于为近距离成藏,其天然气聚集效率高,因此上古生界准连续型致密砂岩气藏的生气强度下限可降低至10×10 m/km左右。

A comprehensive analysis of the Upper Paleozoic gas source conditions in Ordos Basin shows that high quality source rock is the major factor controlling the formation and distribution of large tight sandstone gas field in the study area.The lower limit of gas generation intensity for large tight sandstone gas field is determined based on analysis of gas production test results.A correlation analysis is first performed on the thickness,total organic carbon content () and maturity of the Upper Paleozoic source rocks in Ordos Basin,and gas generation intensity of the sources rocks is then calculated based on the correlation analysis.The calculation results are finally integrated with gas production tests to perform comprehensive analysis.The analysis of gas source conditions indicates that the Upper Paleozoic source rocks are characterized by high quality,wide distribution,high maturity,high intensity of gas generation and wide gas supply.In general,the intensity of gas generation ranges from 10×10 m/km to 40×10 m/km.However,the gas generation intensity is not equilibrium in the whole basin.It ranges from 10×10 m/km to 20×10 m/km in the western basin,whereas,it is more than 16×10 m/kmin most part of eastern basin.In conclusion,high quality source rock is one of the major factors controlling the formation of large tight sandstone gas field,and it also controls the distribution of gas-water contact in the Upper Paleozoic tight sand reservoirs.As gas accumulation is closed to the source rocks and the accumulation efficiency is high,the lower limit of gas-generation intensity can be reduced to about 10×10 m/km for Upper Paleozoic quasi-continuous tight gas accumulation in Ordos Basin.

10.11743/ogg20130502