塔里木盆地巴楚-塔中地区寒武系盐下白云岩储层成岩作用及物性特征

塔里木盆地巴楚-塔中地区盐下白云岩有效储层空间非均质性较强，储层分布不仅受颗粒滩、生物礁等高能沉积相带影响，成岩改造作用成岩改造作用也相当显著。通过对巴楚-塔中地区井下样品的显微观测、地化分析及测井资料配套解释，详细刻画了盐下白云岩特征，进一步认识了成岩改造过程及其对白云岩储集体的制约机制。结果表明，下寒武统盐下白云岩主要为泥粉晶白云岩、颗粒云岩、微生物白云岩和细晶白云岩，储集体主体呈现出早期经历过大气淡水成岩改造作用，中期孔隙度保持，晚期储集物性进一步改善的演化趋势；盐下白云岩优质储层是适中白云石化作用、上覆膏盐岩层对下伏层段的遮挡作用，以及后期热流体溶蚀改造作用共同叠加的结果；构造-热流体对储层的改造在垂向上分为5个成岩作用带，即热流体矿物发育带、热流体角砾化作用带、裂缝发育带、溶蚀作用带和热流体白云石胶结带，其中溶蚀作用带对储层建设作用最强，其次为裂缝发育带。

Diagenesis and physical properties of subsalt dolomite reservoirs of the Cambrian,Bachu-Tazhong areas,Tarim Basin

The effective subsalt dolomite reservoirs in the Tarim Basin are characterized by great spatial heterogeneity.The reservoir distribution therein is under the influence of both high-energy sedimentary facies belts such as grain shoal and organic reef facies, and diagenetic modification.To further understand the restriction mechanism of diagenetic modification on dolomite reservoirs, we thoroughly described the subsalt dolomite characteristics through microscopic observation, geochemical analysis and logging data interpretation of drilling core samples taken from Bachu-Tazhong areas.The results indicate that the Lower Cambrian subsalt dolomites are dominated by micrite dolomite, grain dolomite, microorganism dolomite and fine-crystalline dolomite.The reservoirs mainly evolved from early-stage diagenetic modification by meteoric water, middle-stage porosity preservation, to continuous improvement of reservoir properties at later stages.The high-quality subsalt dolomite reservoirs are the combined products of proper dolomitization, shielding effect of the overlying gypsolytes on the underlying intervals, and dissolution by thermal fluids in the later periods.Vertically, there are five diagenetic zones in the reservoir under tectonic-hydrothermal modification:hydrothermal mineral developing zone, hydrothermal brecciation zone, fracture developing zone, dissolution zone, and hydrothermal dolomite zone of cementation.Among them, the dissolution zone is the most significant contributor to reservoir improvement, followed by the fracture developing zone.