深部超压储层发育机制及控制因素——以准噶尔盆地永进油田为例

随着油气勘探向深层-超深层领域推进,针对深层有利储层发育规律的研究至关重要。准噶尔盆地永进油田西山窑组埋深大,储层致密,超压强度大,但含油层段物性明显较好,超压流体与物性演化过程存在复杂的相关性。为此,以准噶尔盆地永进油田西山窑组的成岩、物性、压力及油气充注过程等成藏关键要素的演化过程及其时空匹配关系为核心,开展有利储层形成机制研究。结果表明,研究区目的层高孔带的形成与低岩屑含量、早期超压充注、成岩抑制、水力破裂及次生溶蚀5类作用有关。其相互作用机制为:相对于高岩屑含量砂岩,低岩屑含量砂岩压实程度弱,原生孔保存较好,早期超压含烃流体优先充注原生高孔带,超压进一步延缓原生高孔带压实,受烃类流体充注及绿泥石薄膜等成岩抑制作用,高孔含油段的孔隙度基本保持不变;强超压同时形成水力裂缝,进一步改善了储层渗透性;依赖于原生孔和水力裂缝提供的流体活动场所和空间,原生孔保存较好或裂缝较发育层段次生溶蚀增孔也较显著,总保孔量约为7%。

Development mechanism and controlling factors of deep overpressured reservoir:A case study of Yongjin Oilfield in Junggar Basin

As the hydrocarbon exploration advances into the deep and ultra-deep reservoirs,it is important to study the development rules of the favorable reservoirs in deep layers.The Xishanyao Formation of Yongjin Oilfield in Junggar Basin has a large burial depth,tight matrix,and it is overpressured.However,the properties of the oil-bearing intervals are favorable,and the overpressured fluid has complex correlation with the evolution of formation properties.Therefore,the attentions are focused on the evolution of key factors such as diagenesis,formation properties,pressure and oil-gas filling and their time-space matching of Xishanyao Formation in Yongjin Oilfield,to study the development mechanism of favorable reservoirs.The results show that the formation of high porosity zone is related to five factors including,low debris content,early overpressure filling,diagenesis inhibition,hydraulic fracturing,and secondary dissolution.The interaction mechanism is that the sand body with the low debris content is weakly compacted,in which the primary pores are well preserved,and the early overpressured hydrocarbon bearing fluid is preferentially injected into the primary high porosity zone to make its compaction delay comparing with sandstone with the high debris content.Due to the inhibition of hydrocarbon fluid filling and chlorite film,the porosity of the high-porosity oil-bearing section has remained basically unchanged,and the hydraulic fracture is formed at the same time by strong overpressure,which further improves the permeability of the reservoir.Depending on the fluid activity space provided by the primary pore and hydraulic fractures,the secondary dissolution pores of the primary poreswell preserved or the fracture developed section are well developed.The total remaining porosity is about 7%.