【作者】 徐国强；

【导师】 沈忠民；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2007， 博士

【摘要】 层序地层学与古岩溶学的交叉学科渗透研究是当前古岩溶研究中的前缘方向，其主要目的是通过建立海（水）平面周期性升降变化下碳酸盐岩内部发生古岩溶与盆地内沉积层序的内在联系，探索层序界面相关古岩溶（包括大型风化壳、侵蚀型层序界面和短期暴露地表的各种层序界面古岩溶）的发育机制、发育分布规律，并建立相关研究方法及预测技术。目前该研究领域刚刚起步，前期研究成果非常少，尤其在地下古岩溶洞穴层研究方面。由于层序界面相关古岩溶是碳酸盐岩大型隐蔽油气藏储层（如塔河油田、普光气田）的主要形成机制，因此，开展该方向研究，对于碳酸盐岩油气藏勘探具有重要理论意义及应用价值。本文在总结前期研究成果基础上，将层序地层学理论引入岩溶洞穴层研究，建立碳酸盐岩陆块内部洞穴层与盆地内同时期形成的沉积层序内部等时层的关系，以等时层作为约束条件，对塔北、塔中、和田地区的洞穴层进行盆地范围内的跨地区的对比研究，为间歇性海平面上升过程中形成的多期次风化壳岩溶洞穴层研究提供对比的理论依据及方法；将洞穴层和洞穴内多旋回“坍塌角砾-暗河沉积层”形成的水动力条件及过程与盆地内海平面升降变化曲线联系在一起，分析海平面升降变化所引起的不同地质条件下的岩溶作用方式与特征，揭示地下深埋洞穴层的成因机制。通过古岩溶洞穴层预测的关键技术攻关研究，建立较为完整的古岩溶洞穴层预测方法技术，并对塔中、和田古隆起洞穴层进行预测，为大型隐蔽油气藏勘探提供决策依据。取得的主要成果如下：1)通过和田、塔中、塔北古隆起大量古地貌研究实践，形成完善的古地貌恢复技术，并将其应用于塔中、和田古隆起早海西期洞穴层对比和预测，较早地得出塔里木盆地在早海西岩溶期发育了下（C-Ⅰ）、中（C-Ⅱ-1，C-Ⅱ-2）、上（C-Ⅲ）3套大型洞穴层的结论；2)将层序地层学理论引入古岩溶洞穴层研究，较为全面地阐述了洞穴层形成演化与海平面升降变化关系，建立了多期次洞穴层与盆地沉积层序的内在联系，提出了洞穴等时层的概念，以及利用等时层进行跨地区对比的方法与原理；3)利用洞穴内沉积物的沉积结构、影响洞穴层形成的内在、外在地质因素方面的证据，论证了3套洞穴层的形成序次。明确指出3套洞穴层主要是在晚泥盆世-早石炭世海平面间歇性上升过程中形成的，每个洞穴层发育期与盆地内沉积层序的高水位海平面稳定期对应，洞穴层序次为下老上新；4)提出了利用洞穴等时层为古洞穴层间接定年方法技术，推断出底部C-Ⅰ洞穴层主要形成于早石炭世东河砂岩沉积期，C-Ⅱ洞穴层形成于早石炭世生屑灰岩段沉积期，C-Ⅲ洞穴层形成于早石炭世下泥岩段上部沉积期。使用McArthur（2002）⁸⁷Sr/⁸⁶Sr定年曲线，通过生屑灰岩等时层定年，C-Ⅱ洞穴层的形成时间大约为358.2ma；5)提出了叠积层序、叠积洞穴概念，建立了海（水）平面快速上升过程中陆块内部潜水面上升迟后带快速向上侵蚀岩溶的成因地质模式，得出巨厚洞穴内的多旋回“坍塌角砾-暗河沉积”组合是海平面快速上升后斜坡内陆区潜流面相对于潜水面迟后上升，在老的洞穴带基础上潜流持续向上侵蚀岩溶的结果；6)通过塔北、塔中、和田这3大古隆起早海西期古岩溶地质条件综合分析及对比研究，得出古隆起形成演化构造背景是控制洞穴层发育分布的主要因素，认为塔北强烈挤压褶皱型整体隆升使得裂缝均匀发育，暴露面积、入出水口间高差、汇水量大，为盆地边缘碳酸盐岩陆块台地式岩溶，可发育很多个纵向叠置的多重大型洞穴系统；塔中地区因为局部发育冲断褶皱而整体隆升幅度小，使得仅局部暴露地表，呈盆地内岛屿式古岩溶，因为岛小而导致的汇水量少是大型洞穴系统不发育的主要因素，局部因裂缝极为发育可形成小型洞穴系统；和田古隆起主要为斜坡背景中通过两翼分期沉降而形成的古隆起，发育盆地边缘斜坡阶地式古岩溶，宽缓构造背景使得暴露区面积、汇水量大，但入出水口间高差小、裂缝欠发育，导致3个洞穴层分地发育而不能纵向叠置；7)利用几何学原理，通过建立一个简化的裂隙空间替代模型，经过公式推导，获得断层裂隙空间的一种定量计算方法：8)结合风化壳岩溶洞穴在不同地质条件下的发育分布规律，将“古地貌恢复技术、古裂缝描述技术、洞穴层跨地区对比技术、“3位一体”洞穴层定位技术整合成一套较为完整的风化壳岩溶洞穴层综合分析预测技术；9)通过和田古隆起油气成藏条件综合分析，得出在和田河气田以南的和田古隆起北部，4500-7500m深度范围内，发育一个面积达4800 km²的C-Ⅰ洞穴层发育带，可能是很好的碳酸盐岩隐蔽圈闭中的油气储层。更多还原

【Abstract】 The interdisciplinary study between Sequence Stratigraphy and Paleokarst is the frontier trend presently. The main objects for this research are to explore the developmental mechanism, distribution pattern of some paleokarst related with sequence boundary (including huge weathering crust, erosion-type sequences boundary and various sequences boundary paleokarst exposed in short-term) through the establishment of the interrelationship between paleokarst occurred in inner carbonate land and depositional sequences in basin under the cycles of sea level change, then to establish method and techniques for predicting cave systems. It is obvious that this study has prominent theory significant and application value for hydrocarbon exploration in carbonate rocks because the sequence boundary associated paleokarst are the main mechanism of carbonate reservoir of huge subtle traps (e.g. Tahe oilfield, Puguang gasfield). At present, however, the study in this field is just at its initial stage, thus the previous results are very few. In this paper, based on the summarization of previous results, it introduced sequence stratigraphy theory into the study of paleokarst cave horizons in order to establish the interrelation of isochronous beds between the cave horizons occurred in inner carbonate land and the depositional sequences which are corresponding to mentioned cave horizons in time in this basin, then taking isochronous beds as a constraint, conducts a correlation study on cave horizons developed on Tabei, Tazhong and Hetian uplifts across different carbonate lands in this basin to provide theory evidences and method for the study of multiple weathering crust karst cave horizons during the time of intermissive rising of sea level; then linking the hydrodynamic conditions and process of cave horizons and inner cave multicyclic combination of "collapsed breccias interbedded with underflow sediments" with the eustatic sea level change curve in this basin to analyze the karstification ways and characteristics under different geological conditions caused by the eustatic sea level change and then to reveal the origin mechanism of the cave horizons deeply buried. By the research of key methods for predicating the underground cave horizons, a series of methods had been obtained and applied into the predication of cave horizons in Hetian and Tazhong paleouplifts in order to provide the foundations for looking for subtle oil and gas pools in these areas. Main results obtained are as following:1) Has formed the perfect technique for restoring the paleogeomorphy through the integrate research and practices. This technique was applied in the prediction of paleokarst on Hetian, Tazhong and Tabei uplifts. Has concluded early that there are three huge cave horizons (the lower one, C-I ; the middle one, C- II; the upper one C-III) were developed during Early Hercynian;2) Has introduced sequence stratigraphy into the study of paleokarst cave horizons, discussed comprehensively the relationship between the development evolution of cave horizons and the eustatic sea level change, and established the interrelationship between multiple cave horizons and depositional sequences in this basin, and introduced the concept of isochronous bed of cave, the method and principle of the correlation of cave horizons in different region by using isochronous beds;3) Has discussed the forming order of three cave horizons by the evidences of depositional configurations in cave deposits, the intrinsic and extrinsic factors of paleokarst. It concluded that they are developed during the time of intermissive rising of sea level in Early Carboniferous, ach one corresponding to the highstands of sea level change cycles, in an order of the lower the older;4) Has advanced an indirect method for dating the cave horizons through their isochronous beds. Has deduced that the cave horizon C-I , C- II and C-III were individually formed during the deposition of Donghe sandstones, Bioclastic limestones and upper part of Lower mudstones of Lower Carboniferous. Using the Sr isotopic fitting curve drawn up by McArthur (2002) for the dating, the age of the bioclastic limestones (the isochronous bed of C- II) is 358.2 ma;5) Has introduced the concepts of aggradational sequences and aggradational caves, and established the hydrodynamic and geological model of the hysteresis rising effect of underflow surface on the inland caused by abrupt rising of sea level, and pointed out that the inner huge cave multicyclic combination of "collapsed breccias interbedded with underflow sediments" is the effect of the rising of underflow surface delayed to the rising of water table in the inland of basin marginal slope, which is caused by abrupt rising of sea level, and the result of upward persistent erosion of underflow based on the older cave zones; 6) Has concluded that the different development and occurrence of cave horizons on Tabei, Tazhong and Hetian paleo-uplifts were mainly controlled by the differences of their tectonic features and evolutional history. In Early Hercynian, the whole Tabei area was folded and uplifted violently, which led to a basin marginal paleokarst terrane with a large exposure area, homogeneous fractures, well water catchment and high water falling between input and output, as a result, a lots of large scale cave systems with multi cave horizons was developed there. Whereas the Tazhong uplift was uplifted softly in this stage, which led to the small exposure area, poor water catchment, island paleokarst terranes in the center part of basin. As a result, it is in lack of large scale cave systems due to the poor water catchment, but small cave systems may be occurred on the zones of well-developed fractures. The Hetian paleo-uplift is a flat uplift evolved from the separated subsidence of the two limbs in different stage, which led to a large basin marginal karst terrane on a flat slope, poor development of fractures, as a result, 3 cave horizons may be developed owing to that the well water catchments, but multi cave horizons could not be occurred vertically due to the flat slope;7) Using area balancing technique and geometrical relationship, a 2-D model to calculate the pore space of fractures associated with fault development have been developed. The equation created for calculating of fault fracture pore space provides a new way and method for the quantitative description of the development of fault fractures.8) Has established a relatively entire method series for predicating the cave horizons by combine the method of resuming the paleo-physiognomy, description of paleo-fractures , transregional correlation of cave horizons and the locating of cave horizons by the " intersection of fracture zone and water table".9) Has concluded that there is an area of the cave horizon C-I occurred on the Maigaiti slope in the south of Hetian River gas field (northern part of Hetian paleouplift), with a depth of 4500～7500m, occupying an area of 60×80 km~2, could be good carbonate reservoir of subtle traps in this area.更多还原