珠江口盆地陆丰凹陷深部储层原生孔隙特征及发育机制

Characteristics and Development Mechanism of Primary Pores in Deep Burial Reservoirs in Lufeng Sag,Pearl River Mouth Basin

为了揭示珠江口盆地陆丰凹陷深部储层特征与成因机制,基于储层发育的沉积环境、异常高压、地温梯度和油气充注对储层抗压实能力的影响开展了系统研究。结果表明:陆丰凹陷埋深超过4000 m的古近系储层仍以原生孔隙为主,储层矿物成分主要为石英砂岩,整体表现为低—中渗储层。辫状河三角洲水下分流河道具有稳定的水流作用,长距离的搬运使得岩石粒度分布较为均一,杂基体积分数少,这些是原生孔隙发育的有利条件;泥岩欠压实形成的异常高压传递至砂岩储层中,可以有效地降低压实作用对孔隙空间的破坏;低地温梯度下岩石的塑性程度和延展性相对较弱,从而减缓岩石的压实速率;此外,文昌组4段烃源岩生成的油气进入储层后占据储集空间,有效抑制了后期压实与胶结作用对储层孔隙的破坏。在4种控制因素的耦合控制作用下,陆丰凹陷深部储层原生孔隙普遍发育。

In order to reveal the characteristics and genesis mechanism of the deep reservoir in Lufeng sag of Pearl River Mouth basin,this study systematically analyzed the influence of sedimentary environment,abnormal pressure,geothermal gradient,and hydrocarbons charging on the anti-compaction ability of reservoir.The results show that the Paleogene reservoirs with a buried depth of more than 4000 m in Lufeng sag are still featured by primary pores.The mineral composition of the reservoir is mainly quartz sandstone,and the overall performance is low-medium permeability reservoir.The underwater distributary channel of braided river delta has stable flow action.The long distance transport makes the grain size distribution of rock more uniform and the integral number of mixed matrix less,which are favorable conditions for the development of primary pores.The abnormal pressure formed by mudstone undercompaction transferred to sandstone reservoir can effectively reduce the damage of compaction to pore space.The plasticity and ductility of rock are relatively weak under low geothermal gradient,which slows down the compaction rate of rock.In addition,the oil and gas generated from the source rocks of the fourth member of Wenchang Formation occupied the reservoir space after entering the reservoir,which effectively inhibited the damage of the later compaction and cementation to the reservoir pores.Under the coupling control of four controlling factors,the primary pores of deep reservoir in Lufeng sag are widely developed.