渤海海域渤中凹陷奥陶系碳酸盐岩成岩作用

渤中凹陷奥陶系碳酸盐岩在沉积后经历了漫长的地质改造,不同成岩作用改造使储层极为复杂,因此识别不同成岩环境对潜山储层预测具有一定意义。通过岩石薄片观察、扫描电镜、阴极发光等分析确定研究区奥陶系碳酸盐岩经历了正常海水成岩环境、大气淡水成岩环境和埋藏成岩环境,储层储集空间以溶蚀作用引起的次生孔隙和裂缝为主,物性中等,储层非均质性强。结合区域构造演化,镜下特征,碳、氧同位素分析及包裹体分析表明虽然在大气淡水成岩环境及埋藏成岩环境下均有溶蚀作用发生,但对该区下古生界碳酸盐岩储层影响最大的是古生代-中生代期间大气淡水环境下的表生岩溶作用,构造运动导致地层抬升遭受长时间风化淋滤从而改善了储层物性,而埋藏环境下溶蚀改造对储层物性改造有限;新近纪期间深埋环境下大规模胶结作用是本区奥陶系储层物性降低的主要因素。 

Diagenesis of the Ordovician Carbonates in Bozhong Depression,Bohai Sea Area

There is long geological reconstruction of Ordovician carbonates in Bozhong Depression after its deposition.Different diagenetic transformation makes reservoir very complex,so identifying the different diagenetic environment has certain significance for the buried hill reservoir prediction.By using normal thin-sections,cast thin-sections,scanning electron microscope and cathodoluminescence,this paper analyses the main diagenetic environment in the research area through the normal seawater,atmospheric freshwater and burial diagenetic environment.The pore types are dominated by secondary pores caused by dissolution and fracture.The reservoir physical properties are characterized by medium reservoir with strongly heterogeneity.The carbon and oxygen isotopic analysis and inclusion analysis of carbonate reservoir,based on the regional tectonic evolution and microscopic characteristics,shows although dissolution may occur in atmospheric freshwater and burial diagenetic environment,the main influential factors were hypergene karstification during the Paleozoic to Mesozoic time.The long time leaching dissolution improves the reservoir physical properties,but the dissolution under burial diagenetic environment can be limited for shaping the reservoir physical properties.The primary factor for lowering the Ordovician reservoir physical properties should be the large scale cementation in deep burial environment during Neocene.