摘要
库车坳陷前陆区白垩系发育特低物性、强非均质性和高稳产砂岩储层,溶蚀作用显著,但成因机制尚不是很明确。利用高温高压热模拟实验还原了目的层在成岩演化过程中1种表生流体和2种埋藏流体环境下溶蚀作用差异,揭示了成岩矿物演化过程及储集空间结构变化特征。结果表明,表生成岩期大气淡水淋滤弱酸性流体环境(CO_2饱和溶液,p CO_2=1 MPa)溶蚀作用最为显著,长石类矿物发生明显溶蚀,石英和黏土矿物相对难溶,Na^+、Ca^(2+)和K^+等离子析出明显,Si^(4+)和Al^(3+)析出较少,样品表面沉淀出较多的疑似多边形石英和铝硅酸类矿物;成岩晚期油气充注酸性流体环境(乙酸溶液,2 m L/L)溶蚀作用其次,易于溶解白云石、石膏和长石类矿物,Ca^(2+)、Mg^(2+)、Na^+和Si^(4+)等离子析出明显,样品表面无沉淀;成岩早—中期碱性流体环境(Na HCO_3溶液,p H=7.46、HCO_3^-=0.6 mol/L)溶蚀作用相对较弱,石英、长石和部分黏土矿物均发生了不同程度的溶蚀,且随着温度、压力的增加,溶蚀作用程度增加。综合分析表明:表生流体是研究区砂岩储层溶蚀孔隙发育的关键因素,其次为有机酸和碱性埋藏流体。这一认识能够丰富致密砂岩储层孔隙成岩演化理论,为下一步寻找规模储层发育区和气田有效开发提供理论支撑。
The sandstone reservoirs in the Kuqa foreland area of Tarim Basin have the characteristics of very low physical properties,strong heterogeneity and high-stable production,in which the dissolution of reservoir rocks is significant,but their formation mechanism is not very clear by far.A series of thermal simulation experiments under high temperature and high pressure were performed to restitute the dissolution effects of target layers in addition of one epidiagenetic fluid and two kinds of burial fluids for a better understanding of the diagenetic process,and then to realize the diagenetic evolution of minerals and spatial changes of reservoir structures.In the epidiagenetic stage,there was weak acidic fluid environments leached by atmospheric fresh water and replaced with saturated CO 2 solution(p CO 2=1 MPa)in the experiment.The results showed that the dissolution was very significant and feldspar minerals emerged significant dissolution,while the quartz and clay minerals were relatively insoluble.Na+,Ca 2+and K+were separated out more obviously with Si 4+and Al 3+less.Many suspected polygonal quartz and aluminosilicate minerals have precipitated on the sample surface.The dissolution was secondary in the acidic environment(instead by acetic acid solution,2 mL/L)formed by hydrocarbons filling in the later diagenetic stage and dolomite,gypsum and feldspar minerals were easily to be dissolved.Ca 2+,Mg 2+,Na+and Si 4+were separated out apparently without precipitation.The dissolution is relatively weak in NaHCO 3 solution(pH=7.46,HCO-3=0.6 mol/L)which is instead of the alkaline environment of early-middle diagenetic stage and the dissolution of quartz,feldspar and clay minerals appeared in different degrees which increase with the increase of temperatures and pressures.Comprehensive analysis showed that superficial fluid was the key factor for dissolved pore development of sandstone reservoirs in the study area,followed by organic acid and alkaline buried fluid.This understanding not only enriches the theory of poro
作者
曾庆鲁
张荣虎
王力宝
赵继龙
佘敏
ZENG QingLu;ZHANG RongHu;WANG LiBao;ZHAO JiLong;SHE Min(PetroChina Hangzhou Research Institute of Geology,Hangzhou 310023,China;Key Laboratory of Carbonate Reservoir,CNPC,Hangzhou 310023,China)
出处
《沉积学报》
CAS
CSCD
北大核心
2018年第5期946-956,共11页
Acta Sedimentologica Sinica
基金
国家科技重大专项(2016ZX05003-001
2017ZX05001-002)
National Science and Technology Major Project
No.2016ZX05003-001
2017ZX05001-002
关键词
库车坳陷
白垩系
致密砂岩储层
溶蚀作用
实验模拟
Kuqa depression
Cretaceous
tight sand reservoir
dissolution
experimental simulation
