摘要
鄂尔多斯盆地姬塬地区长8储层中长石含量较高,且普遍存在长石溶蚀现象,对致密储层物性的改善具有重要意义。在对长8致密储层特征的研究基础上,利用高温高压流体—岩石相互作用模拟实验,并结合偏光显微镜、扫描电镜(SEM)和X-射线衍射(XRD)等分析技术,模拟研究区长8储层岩石样品与有机酸的相互作用,分析了溶蚀作用类型及其特征,并解释了相关溶蚀作用机理,定量计算了溶蚀作用对储层孔隙度的影响。为使模拟实验更接近实际地质情况,流体采用0.15mol/L、pH=2.65的乙酸溶液,模拟温度为87～103℃,模拟压力为24.70～30.18MPa。研究表明:长8储层主要岩石孔隙类型为原生粒间孔和长石溶蚀孔,其中长石溶蚀孔较发育,占总孔隙的39%左右,计算得其视溶蚀率为37.8%～50.0%,呈中等溶蚀程度;长石类和碳酸盐类矿物在酸性条件下均能发生不同程度的溶蚀,碳酸盐类矿物的相对溶蚀率整体大于长石类矿物的相对溶蚀率;在95℃左右时矿物的溶蚀作用最为明显,依据地温梯度计算其对应的埋藏深度约为2 370～2 710m,该深度可能是长8储层中有利储层的主要分布区域;溶蚀作用导致长8致密储层的孔隙度增加约3.57%～3.69%,其平均孔隙度增加3.63%,溶蚀作用是研究区长8储层孔隙度增加的关键成岩作用类型,是储层"甜点"发育的主要控制因素。
Chang 8 reservoir in Jiyuan area of Ordos Basin holds characteristics of high feldspar content and common feldspar dissolution phenomenon,which is important to improve the physical properties of tight reservoirs.On the basis of identifying the basic characteristics of Chang 8 tight reservoir,utilizing the simulation experiment of fluid-rock interaction with high temperature and high pressure,combined with polarized microscope and scanning electron microscope(SEM)and X-ray diffraction(XRD)analysis techniques,this paper simulates the interaction between Chang 8 reservoir rock samples and organic acid,analyzes the types and characteristics of dissolution,explains the dissolution mechanism and quantitatively calculates the influence of dissolution on porosity of reservoir.In order to make the simulation experiment more close to the actual geological conditions,0.15 mol/L acetic acid solution with pH=2.65 is used as reaction fluid.The simulation temperature range is set to 87-103℃and the simulated pressure range is set to 24.70-30.18 MPa.The research result shows that intergranular pores and feldspar dissolved pores are the main pore types,of which the feldspar dissolved pores are more developed and accounts for 39% of the total porosity.The apparent solution ratio is 37.8%to 50.0% with moderate degree of dissolution.In addition,carbonate minerals can also be dissolved under acidic condition.The relative solution ratio of carbonate minerals generally exceeds feldspar.The dissolution degree is strongest at about 95℃and the burial depth is about 2 370-2 710 m by the geothermal gradient calculation,which should be the main distribution area of favorable reservoir of Chang 8.Overall,dissolution is the main diagenesis types to improve the porosity and result in the 3.57%-3.69%increase of porosityin tight reservoirs of Chang 8.Therefore,it is also the main controlling factor for the development of"dessert"in Chang 8 tight reservoir of western Jiyuan area.
作者
李树同
姚宜同
乔华伟
惠潇
程党性
张文选
牟炜卫
Li Shu-tong;Yao Yi-tong;Qiao Hua-wei;Hui Xiao;Cheng Dang-xing;Zhang Wen-xuan;Mou Wei-wei(Key Laboratory of Petroleum Resources ,Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics,Chinese Academy of Sciences,Lanzhou 730000,China;Instztute of Sedimentary Geology,Chengdu University of Technology ,Chengdu 610059,China;The Third Oil Production Plant of Changqing Oil Fzeld Company ,Petrochina ,Yinchuan 750006,China;Exploration and Development Research Institutzon ,Changqing Oilfield Company ,Xi'an 710021 ,China;University of Chinese Academy of Sciences ,Beijing 100049,China)
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2018年第12期1727-1738,共12页
Natural Gas Geoscience
基金
国家自然科学基金面上项目(编号:41772142)
中国科学院兰州油气资源研究中心"十三五"创新基金(编号:135CCJJ20160510)联合资助
