火山活动影响下的致密砂岩气储层特征及气藏富集主控因素

Main enrichment controlling factors and reservoir characteristics of tight sandstone gas under the influence of volcanic activity

受火山活动影响的致密砂岩气藏是一种特殊的致密气藏。本文以松辽盆地南部德惠断陷为例,综合应用岩芯、分析化验、测井、地震和气藏测试资料,研究火山活动特征、火山活动影响下致密砂岩沉积、储层特征及富集主控因素。在火山作用和火山相分析基础上,研究砂岩储层的沉积、岩性和物性特征,明确扇三角洲前缘为有利储层相带,提出致密砂岩储层划分标准。通过对德惠断陷致密气藏系统研究表明,火山作用对致密砂岩气藏的天然气形成、气藏温压系统、成藏有重要影响。主要表现在四个方面:(1)晚期火山活动形成的火山侵入,增加了地层温度压力,促进了烃源岩生排烃;(2)火山活动影响湖盆沉积充填,控制储层分布,促进优质储层发育,为气藏富集提供了良好储集空间;(3)早中两期火山活动对整个地层起到了"包裹作用",促进了圈闭的形成;(4)火山活动与区域生排烃期次的时空配置好,保证了致密砂岩气成藏和富集。这些认识对致密砂岩气藏的形成与分布研究有重要的借鉴意义。

The tight sandstone gas reservoirs affected by volcanic activity are a special type of tight gas reservoir.Taking the Dehui fault depression in the south of Songliao basin as an example, this paper studies the characteristics of volcanic activity, the deposition of tight sandstone under the influence of volcanic activity, the characteristics of reservoir and the main controlling factors of enrichment by comprehensive application of core analysis, logging, seismic and testing data. Based on the study of volcanism and volcanic facies, sedimentology, lithology and physical characteristics of sandstone reservoirs are studied. It is shown that the fan delta front is the favorable reservoir facies belt, and a classification standard for tight sandstone reservoirare proposed. Based on the analysis of the general characteristics of tight gas reservoir in the Dehui fault depression and the analyses of typical tight sandstone gas reservoir, it is considered that volcanism has an important influence on the formation of natural gas, the temperature pressure system of gas reservoir, and the time of gas reservoir formation. It is mainly manifested in four aspects:(1)In the late stage of volcanic activity, the formation temperature and pressure are increased, and the generation and expulsion of hydrocarbon are promoted;(2)Volcanic activity affects the sedimentary filling of lake basin, controls the distribution of reservoir, promotes the development of high-quality reservoir, and provides a good reservoir space for gas accumulation;(3)The early and middle stages of volcanic activity played a "wrapping role", that promoted the formation of traps;(4)The time space allocation of volcanic activity and regional hydrocarbon generation and expulsion periods is good, which ensures the accumulation and enrichment of tight sandstone gas. These insights are of fundamental significance for studying the formation and distribution of tight sandstone gas reservoirs.