藏北羌塘盆地羌资5井二叠系碳酸盐岩储层特征及影响因素

Permian carbonate reservoirs from the Qiangzi-5 well in the Qiangtang Basin, northern Xizang: Characteristics and influencing factors

关键词:  羌塘盆地  二叠系  羌资5井  碳酸盐岩储层  影响因素

Key words:  Qiangtang Basin  Permian  Qiangzi-5 well  carbonate reservoirs  influencing factor

摘要:

羌资5井位于藏北羌塘盆地,该井钻遇二叠系龙格组及展金组。储层主要是龙格组及展金组中的碳酸盐岩,其主要岩性是微晶灰岩、粒屑灰岩、生物屑灰岩、角砾灰岩以及粉/细晶白云岩。储集空间主要为孔隙,另发育裂缝。孔隙可分为粒间孔、粒间溶孔、粒内溶孔、晶间孔及晶间溶孔、沿缝合线发育的溶孔;裂缝可分为构造缝、压溶缝和溶蚀缝。物性数据显示,孔隙度变化范围在0.3%~2.3%,平均值为1.31%;渗透率变化范围在(0.0034~0.0062)×10^-3μm²,平均值为0.0044×10^-3μm²,储层评价为差。影响碳酸盐岩储集物性的因素主要是成岩作用和构造作用。有利成岩作用主要是压溶作用、溶蚀作用、白云石化作用;不利的影响因素是压实作用、胶结作用、重结晶作用、硅化作用等。

Abstract:

The Qiangzi-5 well drilled into the Permian Longge and Zhanjin Formations is located in the Qiangtang Basin, northern Xizang. Lithologically, the carbonate rocks as the reservoir rocks are dominantly made up of micritic limestones, grainstones, bioclastic limestones, brecciola and silty or fine-grained dolostones. The pores as main reservoir spaces contain intergranular pores, intergranular solution openings, intragranular solution openings, intercrystal pores and intercrystal solution openings and other solution openings generated along the stylolites. The fissures are assembled by the structural fissures, pressure solution fissures and dissolved fissures. The porosities vary between 0.3% and 2.3%, with an average of 1.31%. The permeabilities range from 0.0034×10^-3 μm² to 0.0062×10^-3 μm², with an average of 0.0044×10^-3 μm². The diagenesis and tectonism are believed to be the main influencing factors for the porosities and permeabilities of the carbonate reservoirs. The constructive diagenesis encompasses the pressure solution, dissolution, dolomitization and tectonism while the destructive diagenesis includes compaction, cementation, recrystallization and silicification.