准噶尔盆地阜北地区头屯河组砂岩自生绿泥石特征

Characteristics of authigenic chlorite of Toutunhe Formation in the northern region of Fubei,Junggar Basin,China

自生绿泥石是砂岩储层中常见的成岩矿物。为了完善碎屑岩储层黏土矿物研究成果,并对准噶尔盆地阜北地区侏罗系头屯河组油气勘探提供地质依据,通过岩心采样观察、铸体薄片、扫描电镜、X射线衍射、核磁共振等测试分析手段,对阜北地区头屯河组砂岩储层中自生绿泥石胶结物的产状及其对储层物性的影响进行了研究。结果表明:头屯河组砂岩储层常见自生绿泥石胶结,形成于早成岩阶段早期,主要以孔隙衬里式胶结产出。头屯河组自生绿泥石包膜对于提高岩石的机械强度和抗压实能力有限,只有当自生绿泥石环边呈连续分布且有一定厚度时,才能抑制石英的次生加大;在保留更多原生孔隙的同时,也堵塞孔喉,导致储层渗透率降低。头屯河组自生绿泥石薄膜厚度临界值为8μm,当厚度<8μm时,随着自生绿泥石薄膜厚度增大,对压实作用的减缓能力越强,储层物性越好;一旦厚度>8μm,自生绿泥石薄膜厚度与储层物性呈明显负相关,不利于储层发育。

The attitude of authigenic chlorite in the sandstone reservoir of Toutunhe Formation and its effect on the physical property of reservoir is studied by application of drilling core observation, castthin section, X-ray diffraction, scanning electron microscope （SEM） and nuclear magnetic resonancetest analysis. It shows that authigenic chlorites cementation commonly occur as pore lining in theToutunhe Formation of Junggar Basin and form in the early stage of diagenesis. Only when the rimsdistribute continuously with a certain thickness, can they inhibit quartz overgrowth. Thoughauthigenic chlorites preserve more primary pores, they also block the throat as well, resulting inlower permeability of the reservoir. The study shows that the cut-off value of film thickness ofauthigenic chlorite is 8 pm. When film thickness is less than 8 pm, the resistance ability to compactionbecome stronger and the physical property of reservoir becomes better. If the film thickness ofauthigenic chlorite is over 8 j^m, it obviously affects the development of physical property of reservoir.