四川盆地震旦系灯影组白云岩储层的孔隙填充性质

四川盆地震旦系灯影组是四川盆地外围油气勘探的重要潜在储层。该组储层发育良好。在储层孔隙和溶洞中可以看到导致孔隙减少的多种充填物。本文以四川盆地震旦系灯影组储层的孔隙填充为研究对象。通过岩片分析、阴极发光、微量元素和包裹体测温等方法，详细研究了孔隙填充的类型和特征。研究表明，充填物包括白云岩充填物、硅质石英充填物和沥青充填物。其中，白云岩充填物可分为葡萄状白云岩充填物、叶状白云岩充填物、细-中晶白云岩充填物和粗晶白云岩充填物。50%-80%的孔隙由葡萄状白云岩充填物填充，孔隙可以部分填充；0%-20%的孔隙由叶状白云岩充填物填充；20%-80%的孔隙由细-中晶白云岩充填物填充；20%-80%的孔隙由粗晶白云岩充填物填充。1%-5%的次生孔隙通常由硅质石英填充，孔隙可以部分填充。沥青充填通常发生在上述充填之后，残余孔隙常被沥青半充填，使原有孔隙和孔喉变得更小，降低了储层的有效孔隙度和渗透率。因此，这是一种具有破坏性的成岩作用。孔隙充填使储层的次生孔隙度明显降低，不利于灯影组的形成和保存。

关键词

孔隙充填；储层；灯影组；四川盆地

作为四川盆地最古老的储层，震旦系灯影组一直是四川盆地油气勘探的重点。自1960年以来，威远震旦系灯影组的油气勘探取得了突破性进展。威远、高石梯、磨溪等地区的震旦系灯影组相继发现了多个大型气藏，表明震旦系灯影组具有广阔的勘探前景。由于埋藏条件深、构造转换剧烈、成岩环境多变、成岩作用复杂，震旦系灯影组的演化程度较高。对震旦系灯影组的研究主要集中在四川盆地中部震旦系灯影组的沉积环境、储层特征、表生岩溶、成岩阶段等方向。然而，有关灯影组次生孔隙充填的研究相对较少。王兴志等人认为四川盆地灯影组孔隙填充发育良好，填充物以白云岩为主，硅质石英较少。其存在的阶段不同、结构各异。不同时期、不同构造的化学充填物在地球化学特征上存在明显差，次生孔隙的充填程度和沉积环境（成岩环境）也不尽相同。不同专家学者对白云岩和石英充填物的存在阶段及各阶段的先后关系进行了深入研究。

四川盆地是近年来震旦系灯影组勘探的重要地区。但是有关盆地北部震旦系灯影组的研究还比较滞后。以往研究表明，四川盆地震旦系灯影组的储层发育良好。在灯影组二段和四段中，溶孔的发育程度不同，但溶孔中可见大量化学充填物。这些充填物在一定程度上降低了有效孔隙度和渗透率。然而，这些孔隙填充的类型和特征目前尚不清楚。因此，本文选取了四川盆地的多口井和震旦系灯影组的露头作为研究对象。本文从储层孔隙填充的特征出发，以确定充填时期，为四川盆地灯影组的储层孔隙演化研究提供参考，同时有助于分析储层成因。

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Fig. 1. Tectonic setting of Sichuan basin, the location of wells and outcrops and structure section of rocks in the Dengying Formation

图 1.四川盆地的构造环境、灯影组的油气井和露头位置以及岩石的结构剖面

Fig. 2. Macrophotographs and microphotographs of botryoidal structure in the Sinian Dengying Formation in Sichuan basin. a. Dolomite with botryoidal structure, well Tianxing 1, 2759.62 m, z₂dy²; b. Botryoidal structure, well Z6, 3769.25 m, z₂dy²; c. The botryoidal structure developed along the layer, Xianfeng outcrop, z₂dy²; d. Micritic algal dolomite, the cave is filled by botryoidal structure, well Moxi 11, 5496.40–5496.48 m, cross polarized light; e. Sparry dolarenite, the pores between the grains are filled by botryoidal structure, well GK1, 5409 m, polarized light; f. Grain-bounded dolomite, the karren is semi-filled by botryoidal structure, well Gaoshi 2, 5368.88–5368.97 m, polarized light

图 2.四川盆地震旦系灯影组葡萄状构造的宏观照片和微观照片。a. 葡萄状白云岩，天星1井，12759.62米，灯影组2段；b. 葡萄状构造，Z6井，3769.25米；灯影组2段c. 沿地层发育的葡萄状构造，先锋露头，灯影组2段；d. 泥晶白云岩，洞穴内充填有葡萄状构造，磨溪11井，5496.40-5496.48米，交叉偏振光；e. 亮晶白云岩，粒间孔隙由葡萄状构造充填，GK1井，5409米，偏振光；f. 颗粒白云岩，溶洞被葡萄状构造半充填，高石2井，5368.88-5368.97米，偏振光

Fig. 3. Microphotographs of pore-filling finely-medium crystalline dolomite of burial stage in Sinian Dengying Formation in Sichuan basin. a. Silty dolomite, the karstic caves were filled by finely-medium crystalline dolomite, Nanjiang Shatan, the top of z₂dy², polarized light; b. Grain-bounded dolomite, the caves were filled by finely-medium crystalline dolomite and bitumen, well Moxi 8, 5106.93 m, polarized light

图3. 四川盆地震旦系灯影组埋藏期细-中晶白云岩孔隙充填的微观照片。a.粉砂质白云岩，溶洞被细-中晶白云岩充填，南江沙滩，灯影组四段顶层，偏振光；b. 颗粒白云岩，洞穴被细-中晶白云岩和沥青充填，磨溪8井，5106.93米，偏振光

Fig. 4. Macrophotographs and microphotographs of the pore-filling coarse crystalline dolomite of burial stage in Sinian Dengying Formation in Sichuan basin. a. The cave was filled by coarse crystalline dolomite, Xianfeng outcrop, z₂dy²; b. The cave in the crystalline dolomite was semi-filled by crystalline dolomite, well Moxi 9, 5440.25–5440.34 m, z₂dy²; c. Karren in the silty crystalline dolomite was filled by two periods of sparry dolomite, the first phase is silty-finely crystalline dolomite, the second phase is coarse crystalline dolomite, and the two are dissolved and unconformable contact, Gucheng, z₂dy², polarized light; d. The cathode luminescence of photo c, silty-finely crystalline dolomite of the first period is dark brown, coarse crystalline of the second period is red, and the growing edge is bright red, (CL)

图4. 四川盆地震旦系灯影组埋藏期粗晶白云岩充填孔隙的宏观照片和微观照片。a. 粗晶白云岩充填洞穴，先锋露头，灯影组2段；b. 结晶白云岩半充填洞穴，磨溪9井，5440.25–5440.34米，灯影组2段；c. 两相亮晶白云岩的充填粉砂质白云岩溶洞，第一个相为粉砂质-细晶白云岩，第二个相为粗晶白云岩，二者呈溶蚀、不整合接触，固城，灯影组四段，偏振光；d. 图片c的阴极发光，第一个相的粉砂质-细晶白云岩呈深褐色，第二个相的粗晶体呈红色，生长边缘呈亮红（CL）

Fig. 5. Temperature measurement characteristics of coarse crystalline dolomite and quartz filling inclusions in Dengying Formation in Sichuan basin. a. Coarse crystalline and saddle dolomite inclusions and corresponding homogenization temperature in dissolution caves; b. Homogenization temperature histogram of coarse crystalline and saddle dolomite inclusions, D2 represents coarse crystalline dolomite; c. Late quartz filling inclusions and homogenization temperature; d. Homogenization temperature histogram of late quartz filling inclusions, Q1 represents late quartz

图5. 四川盆地灯影组粗晶白云岩和石英充填包裹体的测温特征。a. 溶洞中的粗晶和鞍状白云岩包裹体以及相应的均一温度；b. 粗晶和鞍状白云岩包裹体的均一温度直方图，D2代表粗晶白云岩；c. 后期石英充填包裹体和均一温度；d. 晚期石英充填包裹体的均一温度直方图，Q1代表晚期石英

Fig. 6. Macrophotographs and microphotographs of pore-filling Siliceous quartzs in the Sinian Dengying Formation in Sichuan basin. a. Grey-brown algal dolomite, the cave was semi-filled by siliceous quartzs and crystalline dolomite, well Moxi 8, 5425.64–5425.72 m; b. Grey-brown algal dolomite, the cave was semi-filled by siliceous quartzs and crystalline dolomite, well Z6, 3712.32 m, z₂dy² ; c. Micritic algal dolomite, the caves were filled by subhedral-euhedral quartzs, well GK1, 5410.18 m, polarized light; d. Pore-filling quartzs in seam and dissolution pores, well Moxi 11, 5141.44–5141.55 m, cross polarized light

图6. 四川盆地震旦系灯影组硅质石英孔隙填充的宏观照片和微观照片。a. 灰褐色藻屑白云岩，硅质石英和结晶白云岩半充填洞穴，磨溪8井，5425.64–5425.72 米；b. 灰褐色藻屑白云岩，硅质石英和结晶白云岩充填洞穴，Z6井，3712.21米，灯影组3段；c. 泥藻晶白云岩，被半自形-自形石英充填洞穴，GK1井，5410.18米，偏振光；d. 缝隙和溶孔中的石英填充孔隙，磨溪11井，5141.44–5141.55 米，交叉偏正光

Fig. 7. Macrophotographs and microphotographs of the pore-filling bitumens in the Dengying Formation in the Sichuan basin. a. The caves were filled by bitumens, well Moxi 9, 5046.15–2046.31 m; b. Algal-bounded dolomite, dissolution pores which were developed between algal-bounded framework were semi-filled by bitumens, HJB-1A, the top of z₂dy²; c. Dolarenite, residual corrosion holes were nearly full filled by bitumens, well Moxi 8, 5155.52 m, polarized light; d. The porefilling bitumens, well Anping 1, 5062 m, polarized light

图7.四川盆地灯影组沥青充填孔隙的宏观照片和微观照片。a. 沥青充填洞穴，磨溪9井，95046.15-2046.31米；b. 藻粘结白云岩，藻粘结之间发育的溶解孔隙被沥青半填充，HJB-1A，灯影组4段顶层；c. 白云岩，剩余腐蚀孔几乎被沥青填满，磨溪8井，85155.52米，偏振光；d.沥青填充孔隙，安平1井，15062米，偏振光

Table 1. Results of electron probe analysis of dolomite cements in the karren of Dengying Formation

表1.灯影组岩溶中白云岩胶结物的电子探针分析结果

Table 2. The characteristics of pore fillings in Dengying Formation in Sichuan Basin

表 2.四川盆地灯影组孔隙填充特征