洛伊地区三叠系上统致密砂岩储层孔隙特征及物性影响因素

Characteristics of pore evolution and its influencing factors of petrophysical properties of tight sandstone reservoir in Upper Triassic, Luoyi District

通过岩心观察、薄片鉴定和扫描电镜分析手段,对洛伊地区三叠系上统储层孔隙特征及物性影响因素进行分析。研究结果表明:研究区岩石类型主要为岩屑砂岩、长石岩屑砂岩及岩屑长石砂岩,砂岩成分成熟度与结构成熟度普遍较低。储层主要发育溶蚀孔、残余粒间孔及微裂缝3种孔隙类型,孔隙吼道分布较不均匀,半径普遍较小,孔喉结构为微孔细吼型。三叠系上统储层孔渗较低,非均质性较强,大多数样品的渗透率低于0.1×10-3μm2,属低孔特低渗储层。储层特征主要受沉积及成岩作用的控制,三角洲前缘水下分流河道砂体为该区主要的储集砂体。成岩作用过程中胶结作用及压实作用是研究区储层原生孔隙度损失的主要原因,压实作用减孔量达到25.94%,溶蚀作用及交代作用对储层孔渗有较好的建设作用,构造作用所形成的微裂缝为流体运移提供良好的通道,提高了储层的渗流能力。

On the basis of core observation, slices arbitration and SEM observation, the porosity characteristics and influential factors of Upper Triassic in Luoyi District were analyzed. The results show that the main rocks of the study area are lithic sandstone, feldspathic lithic sandstone and debris-feldspar with medium compositional maturity and lower structure maturity. The pore space of reservoir mainly includes dissolved pore, intergranular pore and micro-crack, the pore throat radius is relatively lesser, and the distribution of pore throat is asymmetrical. The pore configurations are tiny pore and thin throat. The porosity and permeability of the reservoir is lows, and the micro heterogeneity of pore configuration is high. The permeability of most samples is lower than 0.1×10-3 μm2 and the reservoir belongs to low porosity and ultra-low permeability oil reservoir. The characteristics of the reservoir are mainly controlled by sedimentation and diagenesis. The sand body of underwater distributary channel of the delta is the main reservoir sands. The main reasons for the damage of the primary porosity are agglutination and compaction during the diagenesis, and the compaction reduces 25.94% of the primary porosity. Dissolution and metasomatism improve the porosity and permeability of sandstone to some extent. The micro-cracks formed on tectonism provide good channels for the migration of fluid, which also improves the ability of seepage of the reservoir bed.