渤海海域黄河口凹陷北缘沙河街组优质储层差异及成因

黄河口凹陷北缘沙河街组优质储层成因研究比较薄弱，严重阻碍了该区进一步的勘探和评价。利用铸体薄片、物性、黏土矿物、包裹体、埋藏史等资料，对该区沙一+二段优质储层的成因进行了研究，并定量探讨了不同位置的储层孔隙度演化过程。研究表明:1）研究区沙一+二段发育以扇三角洲砂砾岩为主的储层，西部储层物性差，以特低孔特低渗为主，次生孔隙发育；东部储层物性好，以中孔中—低渗为主，局部具有低孔低渗的特点，原生孔隙发育。2）相近的埋深条件下，花岗岩和中酸性火山岩母岩是优质储层发育的主要母岩类型；扇三角洲前缘水下分流河道中、粗砂岩是优质储层发育的主要沉积相和岩石类型。差异压实作用和胶结作用是研究区不同位置储层物性差异的主要成岩因素，西部储层压实和胶结作用强烈，物性差，而构造裂缝发育区储层物性好；东部储层压实和胶结作用相对较弱，物性整体较好。3）研究区西部储层现今处于中成岩B期，东部刚进入中成岩A2期，成岩演化的趋势具有相似性，但成岩过程和强度具有明显的差异性，油气充注所处的成岩阶段相同，但充注的时期不同；不同位置的储层在各成岩阶段损失和增加孔隙的程度迥异，东部早期经历了长期浅埋藏，压实和胶结程度弱，孔隙损失少，而西部早期经历了快速埋藏，孔隙损失程度高。构造活动造成的差异压实作用和胶结作用是储层物性差异的成岩控制因素，西部早期短期快速埋藏导致的强压实和强胶结是储层致密化的根本原因，且西部储层具有“先致密减孔—再溶蚀增孔、油气充注—致密减孔、油气持续充注”的特点。

Differences and Genesis of High-quality Reservoirs in Es1+2 at the Northern Margin of the Huanghekou Sag,Bohai Sea

Relatively few studies have been conducted on the genesis of the high?quality reservoirs in the Shahejie Formation at the northern margin of the Huanghekou Sag， which has severely hindered further exploration and evaluation in the area. This study examined the genesis of high?quality reservoirs in the Es₁₊₂ in this area using data from thin sections， physical properties， clay minerals， inclusions and burial history， and the evolution of reservoir porosity at different locations is quantitatively discussed. In the study area it was found that （1） reservoirs dominated by fan delta glutenite were developed in the Es₁₊₂. Those in the western area have poor physical properties， being dominated by very low porosity and low permeability. The eastern reservoirs have better physical properties， with mainly mesopores and low permeability， but contain localized zones with both low porosity and low permeability. （2） Granite and medium?acid volcanic parent rock development areas at similar depths were the main parent rock types for high?quality reservoir development. In the fan?delta frontal subaqueous distributary channel， coarse sandstone is the main sedimentary facies and rock type for the development of high?quality reservoirs. Differential compaction and cementation were the main diagenetic influences on reservoir physical properties at various locations in the study area. The intense compaction and cementation in the western area resulted in the poor physical properties， although the structural properties of the fractures are good. Relatively weak compaction and cementation in the eastern area have resulted in favorable physical properties. （3） The reservoirs in the western part of the study area are now at the medium diagenetic stage B of the Mesozoic； those in the east have just entered the medium diagenetic stage A2 phase of the Mesozoic. The diagenetic evolution had similarities， but its process and intensity were evidently different: although the diagenetic stage of oil and gas charging was the same， the filling periods differed. Reservoirs at different locations have different degrees of porosity loss or increase at each diagenetic stage， with the highest degree of porosity loss most evident in the western reservoir. Differential compaction and cementation caused by tectonic activity controlled the reservoir properties. Strong compaction and cementation were the root cause of densification in the western reservoirs， which exhibit the characteristics of dense edge formation.