郑家—王庄地区沙一段粘土矿物特征及对储层敏感性影响

CHARACTERISTICS OF CLAY MINERALS AND THEIR EFFECTS ON FORMATION SENSITIVITY IN SHA-1 MEMBER IN ZHENGJIA-WANGZHUANG AREA

东营凹陷郑家—王庄地区沙一段砂岩储集层中蕴藏大量稠油油藏,但开发过程中粘土矿物的敏感性严重制约了该油类藏的有效开发。定向X射线衍射分析结果表明,本区沙一段砂岩储层中粘土矿物组成类型为伊/蒙无序间层矿物(S/I)、高岭石、伊利石和绿泥石,其中以伊/蒙无序间层矿物的相对含量居多。这就决定了研究区储层敏感性以水敏性为主,其余敏感性无或较弱。据定向X射线衍射谱图上S/I主峰d值大小,进一步识别出钙型S/I、钠型S/I及钙钠过渡型S/I。扫描电镜观察表明,S/I具有丝状、网状和蜂窝状三种形态,且大都包裹在岩石骨架颗粒的表面作为孔隙衬里而存在。阳离子交换容量和膨胀率研究结果显示,二者与样品中S/I含量和层间阳离子类型相关。膨胀率和阳离子交换量与S/I含量都呈较好的正相关关系。在S/I中蒙皂石层含量相当的情况下,钠型S/I的膨胀率和阳离子交换量值偏大,钙型偏小,钙钠过渡型居中。此外,粘土总量以及S/I产状对储层损害也有较大的影响。

Sandstone reservoirs in Sha-1 Member in the Zhengjia-Wangzhuang area and Dongying Sag are abundant in heavy oil. However, the formation sensitivity caused by day minerals restricts efficient oil exploration heavily. X-ray diffraction （XRD） analysis showed clay minerals in the sandstone reservoir include randoraly interstratified illite/rnontmorinonites （S/I）, kaolinite, illite and chlorite in which the quantity of randomly interstratified illite/montmorillonites is much greater than that of others. Because of this, water sensitivity is the main form of reservoir sensitivity, and the other four reservoir sensitivity forms are rare or can cause little formation damage. Furthermore, calcium type, natrium type and their mixture type of S/I have been identified according to the d values of main peaks on the XRD. Scanning electron microscope observation revealed that S/I exhibits three morphological habits： silk, meshwork and beehive, and occurs as covering on framework grain surface and pere＇s liner. Measurement of the cation exchange capability （CEC） and swell capability of samples in fresh water indicated that they have correlations with the relative quantity and cations in interlayers of S/I. Swell capability and CEC have positive linear correlations with the relative quantity of S/I. Swell capability and CEC of the mixture type are more than those of calcium type, but less than those natrium type. In addition, the total amount of clay in sandstone reservoirs and the occurrence of S/I also have great effects on formation damage.