准噶尔盆地石南地区中侏罗-下白垩统储层成岩作用研究

Diagenesis of Middle Jurassic-Lower Cretaceous Reservoirs in Shinan Area,Junggar Basin

通过岩心观察、铸体薄片、X射线衍射和扫描电镜等方法,对准噶尔盆地石南地区中侏罗—下白垩统西山窑组(J_2x)、头屯河组(J_2t)和清水河组(K_1q)储层的成岩作用特征和成岩演化序列进行了研究,并总结了研究区成岩作用对储层孔渗的影响。结果表明:中侏罗—下白垩统储层以细砂岩、中细砂岩、中砂岩为主,成分成熟度较低,结构成熟度中等。储层孔渗相关性较好,喉道以中喉道为主,部分为细喉;整体上属于中孔中低渗储层。储集空间类型主要是原生孔隙,溶蚀形成的次生孔隙所占比重很小。通过对储层成岩作用特征和孔隙类型组合分析可知,石南地区中侏罗—下白垩统储层主要处于早成岩阶段A期—早成岩阶段B期,储集岩的成岩作用序列大致为:绿泥石薄膜和早期的方解石胶结→岩屑和长石的溶解→早期高岭石和硅质胶结→次生石英加大和晚期高岭石→晚期铁方解石和铁白云石;而压实作用则贯穿整个埋藏成岩过程。研究区储层主要经历了压实、胶结、溶蚀等成岩作用;其中导致研究区储层孔隙损失的最主要原因是压实作用,其次为胶结作用,而溶蚀作用对储层孔隙增生的贡献量有限。

Based on the core observation, thin sections, SEM and X ray diffraction combined with the reservoir properties analysis, the relationship between diagenesis and porosity evolution of middle Jurassic lower Cretaceous reservoirs （Xishanyao Formation （J2 a） , Toutunhe Formation （J2t） and Qingshuihe Formation （Klq）） in Shinan area, Junggar basin have been researched in this paper. The results show that these reservoirs are mainly consist of fine sandstone, mid fine grained sandstone and medium sandstone, with low composition maturity and medium structural maturity. The correlation of pore and permeability is good, and the throat is dominated by middle throat, with part of fine throat. These reservoirs belong to middle and low permeability reservoir on the whole. The reservoirs porosities are primarily composed of primary porosity, and the second porosity caused by dissolution is very rare. The Middle Jurassic Lower Cretaceous reset volts primarily are formed in A period of early diagenesis and t3 period of early diagenesis, accord ing to the diagenetic characteristics and pore assemblage in Shinan area. The diagenetic sequence of the reservoirs primarily is chlorite precipitation and early calcite cementation, feldspar and lithic dissolu tion, early kaolin and siliceous cementation, secondary kaolinite precipitation and quartz overgrowth, late ankerite and ferro calcite cementation. The result shows that the compaction was occurred through the whole burial diagenetic process, and the middle Jurassic-lower Cretaceous reservoirs have mainly underg one a series of diagenesis, such as compaction, cementation and dissolution. The compaction is the main cause leading to the reduction of the reservoirs porosity, which followed by the cementation, with limited contribution of dissolution to reservoir pore increase.