摘要
本文在野外观察描述基础上,系统分析了库车坳陷致密砂岩-膏泥岩储盖组合内断裂变形机制,研究表明:断裂在膏泥岩内变形机制取决于埋藏深度决定的脆塑性,膏泥岩在浅埋条件下处于脆性变形阶段,形成断层泥充填的贯通型断裂,垂向封闭能力很差;膏泥岩在较深埋条件下处于脆-塑性变形阶段,形成涂抹型断裂带,伴随断距增加,涂抹逐渐失去连续性,连续的膏岩涂抹形成有效封闭,一旦失去连续性,油气将穿越盖层垂向散失;膏泥岩在深埋条件下处于塑性变形阶段,膏泥岩限制断裂穿层。因此,塑性膏泥岩和脆-塑性膏泥岩在涂抹连续情况下,能够形成有效封闭。断裂变形时储层已经致密化,抬升作用和储层超压导致断裂变形机制以破裂为主,断层核为断层角砾岩,破碎带发育大量裂缝,为油气垂向运移通道,侧向封闭依靠岩性对接。这种岩性对接封闭导致天然气聚集模式具有3个典型特征:一是天然气紧邻区域性盖层分布,即天然气层之上为区域性盖层;二是区域性盖层与储层对接形成有效封闭,因此天然气主要分布在气源断裂上升盘;三是烃柱高度取决于断距大小,圈闭范围内最小断距决定烃柱高度和气-水界面分布。
On the basis of the field observation and description,this article systematically analyzed the deformation mechanism of fractures in tight sandstone-gypsum mudstone reservoir-caprock combinations in the Kuqa Depression.The results show that the deformation of faults in gypsum mudstone depends on the brittle-plastic characteristics which are controlled by burial depth.The gypsum mudstone under shallow burial depths is in brittle deformation phase and can form through-going faults filled with mud,resulting in fault gouge with poor vertical sealing capacity.While the gypsum mudstone under deep burial depth is in brittle-plastic deformation phase and can form the smearing-type fault zones and smearing gradually loses continuity with increased throw.Continuous gypsum rock smearing can form effective sealing.Once continuity missing,hydrocarbon will disperse vertically through the cap rocks;the fractures cannot go through the strata because the gypsum mudstone under deep burial conditions is in the plastic deformation phase.Therefore,both plastic and brittle-plastic gypsum mudstone can form effective sealing ability under the condition of continuous smearing.Fault deformation results in reservoirs densification;uplifting and reservoir overpressure lead to the rupture-dominated deformation mechanism,with fault cores consisting of faulting breccia and lots of fractures in faulting zones,forming vertical migration pathways for hydrocarbon.The lateral sealing ability relies on lithology juxtaposition.Such lithology juxtaposition results in the three typical characteristics of the gas accumulation mode.Firstly,the distribution of gas is close to the regional caprock,i.e.the regional caprock directly overlies the gas reservoir.Secondly,the juxtaposition of regional caprock and reservoir forms an effective trap,so the gas is hosted mainly in the uplifted wall of gas source faults.Thirdly,the hydrocarbon column height depends on the size of throw and the minimum throw within the range of the trap determines the height of hydroc
出处
《地质学报》
EI
CAS
CSCD
北大核心
2016年第3期521-533,共13页
Acta Geologica Sinica
基金
国家重大科技专项(编号2011ZX05003-001)
国家“973”项目(编号2012CB723102)
国家自然科学基金(编号41272151)
中国石油科技创新基金(编号2012D-5006-0107)
黑龙江省杰出青年科学基金(编号JC201304)资助的成果
关键词
膏泥岩
断裂带结构
封闭性
岩性对接
脆塑性变形
gypsum mudstone
structure of fault zone
sealing ability
lithology juxtaposition
brittle-plastic deformation
