桂中坳陷泥盆系储层特征及控制因素分析

Reservoir Characteristics and Controlling Factors of Devonian in Guizhong Depression

桂中坳陷泥盆系具独特的"台—盆—丘—槽"沉积体系,沉积储层复杂,目前泥盆系储层研究相对较少。针对此问题,以露头剖面观测资料、室内岩矿鉴定、扫描电镜等分析资料为基础,研究了桂中坳陷泥盆系储层发育特征及其控制因素。研究表明桂中坳陷泥盆系储层岩石类型主要有石英砂岩、礁灰岩、生屑灰岩和白云岩。主要的储集空间类型为原生剩余粒间孔、生物格架孔,以及次生溶孔和白云石晶间孔。研究区下泥盆统石英砂岩的物性相对较好,为裂缝—孔隙型储层;中、上泥盆统碳酸盐岩储层物性总体较差,为低孔低渗型储层,受白云化作用影响可形成物性较好储层。影响储层发育的主要因素为沉积相带及后期的成岩作用,包括白云化作用和溶蚀作用。桂中坳陷北部及东北部的斜坡带为有利储层发育区。

Devonian of Guizhong Depression has the unique ＂platform-basin-hill-slot＂ sedimentary system and the reservoir is complex which was less studied so far. To solve this problem, the characteristics of Devonian reservoirs in the region were studied on the basis of outcrop observations, rock and mineral identification, scanning electron microscopy and other data. Results showed that Devonian reservoir in Guizhong Depression mainly contained quartz sandstone, reef limestone, bioclastic limestone and dolomite. The reservoir space mainly contained the remaining pores between grains, biological pores within the framework, dissolution pores and pores between dolomite crystals. The quartz sandstone of lower Devonian had good physical property, which could be called crack-porosity reservoir. Carbonate reservoir in mid-upper Devonian had poor physical property and was low-porosity and low-permeability one, which could be improved by dolomitization. Major factors affecting reservoir development were sedimentary facies and diagenesis at late stage, including dolomitization and dissolution. The slope belt in northern and northeastern Guizhong Depression was favorable for reservoir.