黏土矿物高温热变及对储层孔隙结构的影响

The Influence of Thermal Alteration of Clay Minerals on Pore Sturcture

金家油田沙一段稠油油藏储层黏土矿物主要为钙基蒙脱石,含量高且具膨胀性,导致储层具强水敏性,制约油藏热采开发,因此需要对黏土矿物高温热变特征进行研究,明确其对储层孔隙结构影响方式。高压釜高温物模实验后样品晶间距、溶质分析、X衍射、扫描电镜等资料分析表明:在100℃以上的高温条件下,随温度升高,蒙脱石晶间距减小,膨胀性减弱,对储层孔隙结构的危害不大;蒙脱石及其他成岩矿物高温条件下发生溶蚀、转化形成新的矿物颗粒充填改造大、中孔喉,变成微、小孔喉,导致储层孔隙结构变差。以此,明确了高温条件下影响储层孔隙结构的关键因素是钙基蒙脱石及其它成岩矿物转化形成新的矿物颗粒造成的堵塞而非其膨胀性。

The high clay content and the expansion of clay mineral consisting mainly of calcium montmorillonite in 1st Member Shahejie Formation in Jinjia Oilfield cause strong water sensitivity,which restrict the thermal recovery,so,the study for thermal alteration of clay mineral is needed to make clear how to effect on the pore structure. The experiments include the crystal axial range of test sample,analysis of aqueous solutes,X-ray diffraction,SEM and oil-bearing thin section after the tests in high temperature in autoclave show that under the condition of high temperature above 100 ℃,with temperature rising,montmorillonite crystal spacing is reduced and the dilatability is decreased,which is little harm to pore structure; the corrosion and conversion to form new mineral grain of montmorillonite and other diagenetic minerals under the condition of high temperature filling large and medium pore throat into micro-pore throat lead to deterioration of pore structure. Through the understanding,it is clear that the key factors affecting the pore structure of the reservoir is blockage of the new mineral particles transformed by calcium montmorillonite and other diagenetic mineral under high temperature condition rather than its expansion.