珠江口盆地番禺4洼文昌组储层特征及主控因素

RESERVOIR CHARACTERISTICS AND MAIN CONTROLLING FACTORS OF WENCHANG FORMATION IN PANYU-4 DEPRESSION, PEARL RIVER MOUTH BASIN

珠江口盆地番禺4洼古近系文昌组碎屑岩储层埋深普遍大于3 100 m,储层物性较差且非均质性强,制约油气高效勘探。综合利用岩心观察、铸体薄片鉴定、扫描电镜、物性测试、压汞测试等分析手段,对番禺4洼文昌组开展岩石学特征、成岩作用及储层主控因素研究。文昌组整体为一套中—特低孔隙度(平均孔隙度为6.5%)、超低—低渗透率(平均渗透率为1.9×10^(-3)μm^(2))储层。通过孔隙演化分析,分选差的砂岩储层初始孔隙仅为33.6%,压实作用所导致的孔隙损失率均大于50%,认为压实作用和差分选是导致该区储层原生孔隙较不发育的共同主控因素。但从物性条件和储集空间来看,各井之间又存在差异,存在3种个性化影响因素,分别为:(1)长石的不完全溶蚀作用;(2)高岭石的伊利石化作用;(3)母岩、岩石类型和泥质含量。

The burial depth of the clastic reservoir of Paleogene Wenchang Formation in Panyu-4 Depression of Pearl River Mouth Basin is generally greater than 3 100 m, and the reservoir has a poor physical property and strong heterogeneity, which restricted the efficient oil and gas exploration. By means of core observation, casting thin section identification, scanning electron microscopy analysis, physical property test and mercury injection test, the petrology characteristics, diagenesis and main controlling factors of the Wenchang Formation in Panyu-4 depression are studied. The results show that Wenchang Formation is a set of medium-ultra-low porosity(average porosity is 6.5%) and ultra-low permeability(average permeability is 1.9×10^(-3)μm^(2)) reservoirs. According to the pore evolution analysis, the initial porosity of a poorly sorted sandstone reservoir is only 33.6%, and the pore loss rate caused by compaction is greater than 50%, indicating that compaction and differential sorting are the main controlling factors leading to the poor development of reservoir primary pores in this area. However, from the perspective of physical conditions and reservoir space, there are differences among wells, and there are three personalized influencing factors:(1) Incomplete dissolution of feldspar;(2) Illitization of kaolinite(3) Parent rock, rock type and argillaceous content.