The development of the Ordovician carbonate karst reservoir in the Tahe Oilfield is intricately linked to paleogeomorphology and the evolution of faults. Clarifying the genetic relationship between faults and karst paleogeomorphology is crucial for understanding reservoir distribution as well as for exploration and development efforts. Using high-precision 3D seismic data for the T74 unconformity in the Tahe main area, this analysis includes detailed geomorphology characterization, fault interpretation through the extraction of seismic attributes, and a description of karst reservoirs based on impedance inversion data. The local geomorphological units, including valleys and dissolution peaks, exhibit a strong correlation with particular faults. The dynamics of thrust faults and NNE strike-slip faults within the study area influence the watershed and geomorphological zoning, directing the flow patterns and distribution of karst water systems. Minor faults and localized fault combinations exert a more significant influence on the formation of local landforms. In the karst period, local faults and fractures resulting from extension are likely to exhibit negative geomorphology under northwest compressive stress. This condition enhances the water conductivity of paleogeomorphology, facilitating karstification and the development of fracture and vug reservoirs. Precise fault interpretation and kinematic dynamic analysis are essential for investigating the genetic mechanisms of karst fractures and cave reservoirs, providing valuable insights for predicting advantageous karst reservoir spaces.

The northward propagation of the Tibetan Plateau has led to the orthogonal N-S shortening in northwestern China, which influenced the topographic formation of the E-W trending Bogda Mountains-southern Junggar Basin coupling system. In this study, we focus on the landscape formation of this coupling system and investigate the effect of the propagating deformation in the periphery of the India-Asia collision zone using topographic analysis and optically stimulated luminescence (OSL) dating of river terraces. Together, the results of the topographic analysis show that the normalized steepness index (ksn) value and the scale of knickpoints decrease from west to east, and there is no significant difference in chi values between two sides of the Bogda Mts. Compiled low-temperature thermochronological data for the Bogda Mts. shows a younging trend from west to east, suggesting that the uplift of the western Bogda Mts. began earlier. The OSL dating for the Dalongkou river terraces, on the northern slope of the Bogda Mts. resulted in ages of the T2, T3, T4 river terraces of 6.2 +/- 1.3 ka, 13.1 +/- 1.7 ka, and 14.2 +/- 2.5 ka, respectively. The incision rate of the Dalongkou River increases upstream from about 1.22 mm/yr near to the southern Junggar Basin, to about 2.1 mm/yr, and to approximately 6.33 mm/yr at the base of Bogda Mts. and reveals an upstream increasing uplift rate. Based on these new data, we propose a model of ongoing late Quaternary folding leading to the upbending of central Bogda Mts., with an inflection point of the fold close to the southern Junggar Basin. Combined with the geomorphological comparison with the eastern North Tianshan landscape, we conclude that the lateral intensity of the tectonic uplift from the North Tianshan to Bogda Mts. has gradually weakened, and the uplift of Bogda Mts. has gradually accelerated since the Quaternary and is controlled by N-S orthogonal shortening caused by the India-Asia collision.

Studying platform margin architecture will help understand mound-shoal reservoir development. Based on the latest drilling practices and geological and geophysical data, the structure types and evolution process of the Cambrian platform margin are studied in the Tarim Basin. The results show that different platform margin structures developed in the northern and southern margin of the Tarim Basin, and underwent different evolution processes. In the north, it was a carbonate ramp with progradational grain shoals from SQ1 to SQ3. From SQ4 to SQ6, it was a rimmed carbonate platform with aggradational mound shoals. In SQ7, it was a karst carbonate platform with big wedge-shaped mound shoals. In the south, no SQ1 sequence occurred in the Cambrian, it was a carbonate ramp with grain shoals from SQ2 to SQ3. From SQ4 to SQ7, it was a weakly rimmed platform with progradational mound shoals. Research shows that the varying tectonic and sea level fluctuations are crucial to the evolution difference of platform margin. In the south, due to the Tanan paleoland at the beginning of the Early Cambrian time, where the SQ1 is missing, the terrain gradient is slight, the carbonate production rate is low, and a progradational platform margin developed. In the north, because it is far from the Tanan paleoland, the carbonate production rate is high, the terrain gradient is large, and an aggradational platform margin developed. At the end of the Cambrian, the Tabei uplift gradually rises, and the SQ7 in the north underwent denudation and karstification, forming a karst platform margin with karst caves. The aggradational and karst platform margin architectures of the SQ6 and SQ7 in the north can form a larger-scale mound-shoal karst reservoir. The progradational ramp platform margin shoals of SQ2 and SQ3 in the south are close to the inherited paleouplift, always toward oil and gas migration, and can form quasicontinuous shoal reservoirs. This study provides a direction for the differential evaluation of carbonate platform marginal mound shoal reservoirs.

Understanding the relationship between faults and underground rivers is crucial for oil and gas exploration. The presence of faults in the Ordovician carbonate rocks plays a significant role in the formation of fracture-cave reservoirs in the Tahe Oilfield that located in Tarim Basin, Northwestern China. In this research, faults analysis and thorough characterization of karst caves and fractures have conducted utilizing the extensive drilling wells and detailed 3D seismic data available in the Tahe area. The results suggest that underground rivers are commonly not found in the higher regions of the paleo-morphology. Multilayer underground rivers are developed in the part of the karst depressions, which is closely related to the nasal structure (anticline on a monoclinic strata) influenced by thrust faults in the center of the study area. The formation and subsequent changes of underground rivers in various ancient watershed are heavily impacted by fault activities. The direction of the watershed and geomorphological zoning, as well as the flow direction of karst water and the water system, are influenced by the activities and tectonic patterns of larger-scale faults. The geometric morphology of the river network system is not strictly limited to larger-sized faults. The activities of small-scale faults, their intensity, the mode of movement and the state of their stress control the development of the local water drainage segments. The morphology of the underground river is influenced by the morphology, fault activities, and the control of the floating diving surface. These factors play a role in shaping and transforming the underground river after its formation. These findings contribute to the study of reservoir connectivity and oil and gas distribution patterns in multi-layered underground river caves.

This study endeavors to formulate a comprehensive methodology for establishing a Geological Knowledge Base (GKB) tailored to fracture-cavity reservoir outcrops within the North Tarim Basin. The acquisition of quantitative geological parameters was accomplished through diverse means such as outcrop observations, thin section studies, unmanned aerial vehicle scanning, and high-resolution cameras. Subsequently, a three-dimensional digital outcrop model was generated, and the parameters were standardized. An assessment of traditional geological knowledge was conducted to delineate the knowledge framework, content, and system of the GKB. The basic parameter knowledge was extracted using multiscale fine characterization techniques, including core statistics, field observations, and microscopic thin section analysis. Key mechanism knowledge was identified by integrating trace elements from filling, isotope geochemical tests, and water-rock simulation experiments. Significant representational knowledge was then extracted by employing various methods such as multiple linear regression, neural network technology, and discriminant classification. Subsequently, an analogy study was performed on the karst fracture-cavity system (KFCS) in both outcrop and underground reservoir settings. The results underscored several key findings: (1) Utilization of a diverse range of techniques, including outcrop observations, core statistics, unmanned aerial vehicle scanning, high-resolution cameras, thin section analysis, and electron scanning imaging, enabled the acquisition and standardization of data. This facilitated effective management and integration of geological parameter data from multiple sources and scales. (2) The GKB for fracture-cavity reservoir outcrops, encompassing basic parameter knowledge, key mechanism knowledge, and significant representational knowledge, provides robust data support and systematic geological insights for the intricate and in-depth examination of the genetic mechanisms of fracture-cavity reservoirs. (3) The developmental characteristics of fracture-cavities in karst outcrops offer effective, efficient, and accurate guidance for fracture-cavity research in underground karst reservoirs. The outlined construction method of the outcrop geological knowledge base is applicable to various fracture-cavity reservoirs in different layers and regions worldwide.

An integration of outcrop observations,as well as data from drilling,logging,and seismic surveys in an oilfield is applied to analyze the filling types and filling cycle assemblages of karst caves associated with paleokarst buried rivers;accordingly,the filling sequences and patterns of the paleokarst buried rivers,as well as the discussion on their petroleum geological implications.The results show that the Ordovician buried-river karst caves with a filling rate of 89.9%in the Tahe oilfield,are predominantly filled with sandy mudstones and collapse breccias.These karst caves host multiple combination cycles featuring coarse-grained lower parts and fine-grained upper parts,which can be classified into polycyclic sedimentary assemblages and polycyclic collapse-sedimentary assemblages for filling.The former is distributed in the karst slope's lower reaches of flat landform,where wells with lost circulation and stringers account for small and high proportions,respectively.In contrast,the latter is situated in the karst slope's upper reaches featuring landform of great drops,where wells with lost circulation are of high proportion together with multiple high-yielding wells.The following conclusions can be reached through analysis:(1)The tortuous spatial structure of buried rivers,combined with their strong runoff transport capacity,facilitate the filling of large amounts of karst detrital materials,resulting in an extremely high filling rate;(2)The seasonal fluctuations in the phreatic surface lead to the formation of cyclic and comparable fillings.This,coupled with water erosion and tectonic activities,gives rise to multi-phase collapses of karst caves.Consequently,polycyclic collapse-sedimentary filling assemblages are formed in the upper reaches,with unfilled spaces developed;(3)The relatively closed underground environment supersaturated with calcium carbonate,results in severe calcareous cementation of fillings,decreasing the intergranular porosity;(4)The unfilled spaces serve as the major targets with potential for oil and gas exploitation.

Based on the seismic, logging, drilling and other data, the distribution, structural types and mound-shoal hydrocarbon accumulation characteristics of platform margins of the Sinian Dengying Formation in the Deyang—Anyue Rift and its periphery were analyzed. Four types of platform margins are developed in the Dengying Formation, i.e., single-stage fault-controlled platform margin, multi-stage fault-controlled platform margin, gentle slope platform margin, and overlapping platform margin. In the Gaoshiti West—Weiyuan East area, single-stage fault controlled platform margins are developed in the Deng 2 Member, which trend in nearly NEE direction and are shielded by faults and mudstones, forming fault-controlled—lithologic traps. In the Lezhi—Penglai area, independent and multi-stage fault controlled platform margins are developed in the Deng 2 Member, which trend in NE direction and are controlled by synsedimentary faults; the mound-shoal complexes are aggraded and built on the hanging walls of the faults, and they are shielded by tight intertidal belts and the Lower Cambrian source rocks in multiple directions, forming fault-controlled—lithologic and other composite traps. In the Weiyuan—Ziyang area, gentle slope platform margins are developed in the Deng 2 Member, which trend in NW direction; the mound-shoal complexes are mostly thin interbeds as continuous bands and shielded by tight intertidal belts in the updip direction, forming lithologic traps. In the Gaoshiti—Moxi—Yanting area, overlapping platform margins are developed in the Deng 2 and Deng 4 members; the mound-shoal complexes are aggraded and overlaid to create platform margin buildup with a huge thickness and sealed by tight intertidal belts and the Lower Cambrian mudstones in the updip direction, forming large-scale lithologic traps on the north slope of the Central Sichuan Paleouplift. To summarize, the mound-shoal complexes on the platform margins in the Dengying Formation in the Penglai—Zhongjiang area, Moxi North—Yanting area and Weiyuan—Ziyang area are large in scale, with estimated resources of 1.58×1012 m3, and they will be the key targets for the future exploration of the Dengying Formation in the Sichuan Basin.

Based on the latest drilling core, thin section, 3D seismic, well logging data as well as exploration results, the sequence stratigraphy and sedimentary microfacies of the Middle—Lower Ordovician carbonates in Gucheng area, and their controlling effects on the development of reservoir were examined by the theories and methods of fine carbonate sedimentology. The results show that the Middle—Lower Ordovician in Gucheng area is a set of typical carbonate ramp deposits, which can be divided into 10 microfacies in 4 subfacies as follows: back ramp, inner shallow ramp, outer shallow ramp, and deep ramp. The back ramp subfacies consists of muddy-dolomitic flat and dolomitic lagoon microfacies; it is dominated by lamellar micrite dolomite tight in lithology. The inner shallow ramp subfacies includes dolomitic shoal and dolomitic flat in shoal top and dolomitic flat between shoals microfacies; it is mainly composed of crystal dolomite with metasomatic residual structure, as well as abundant karst vugs and intercrystalline pores. The crystal dolomite has an average porosity of 4.36%. The outer ramp subfacies includes medium—high and low energy grain shoal and inter-shoal microfacies; it is dominated by sandy limestone, oolitic limestone, and micrite limestone with few pores. The deep ramp subfacies is dominated by low-energy argillaceous deposits, with local presences of storm shoal microfacies. The Lower—Middle Ordovician has six third-order sequences from bottom to top, among which sequence (SQ3) represents the third member of Yingying Formation. The main reservoir has three fourth-order high-frequency sequences. Apparently, the favorable reservoir in the study area is jointly controlled by sedimentary microfacies and high frequency sequence in the carbonate ramp. The former controls the primary pore structure, and the latter controls the intensities of karstification exposure and dolomitization in the penecontemporaneous period. The dolomitic shoals and top dolomitic flats of different stages, superimposed and connected into favorable reservoirs of considerable scale like "platform margin", are favorable exploration facies in the carbonate ramp.

塔河油田上奥陶统覆盖区断裂发育特征显著,对碳酸盐岩岩溶缝洞储层的发育控制明显,分析断裂活动与岩溶缝洞发育之间的关系对储层预测具有重要意义.本文运用蚂蚁追踪数据体、地震拓频数据体、地震绕射波叠后偏移数据体及钻测井等资料,对塔河地区T705-S86区块岩溶斜坡上发育的断裂进行了精细解释,利用平剖面组合样式分析了不同时期断裂的运动学动力学特征,配合缝洞体预测结果明确了断裂活动特征对岩溶缝洞发育的影响,认为断裂活动通过影响古地貌和断裂对地表水的沟通来控制储集体发育厚度进而影响单井油气产量.研究结果表明:研究区构造样式复杂,既有走滑断裂样式也有逆冲断裂样式;岩溶期活动强烈并处于局部张性应力状态的花状构造次级断裂和断背斜顶部的次级断裂利于地表水的下渗,会对岩溶地貌进行改造,产生的局部负向地貌部位有利于岩溶作用沿断裂进行,发育优质储集体.相对于裂缝型储集体,溶洞型储集体厚度多超过120 m,单井累计产量超过5X104t,且产量与厚度具有明显正相关关系,其发育部位和储集体厚度对单井的产能具有较大的影响.溶洞分布集中、缝洞储层厚度较大、缝洞之间的连通性较好并且处于相对的构造高点容易发育优质岩溶缝洞储集体.

Based on a large number of drilling, logging, seismic and production data, the differential structures of karst zone and hydrocarbon distribution in different paleogeomorphic units of the Tahe area, Tarim Basin, are discussed by analyzing the karst drainages and flowing channels. The karst paleogeomorphy of Ordovician in Tahe area is composed of watershed, karst valley and karst basin. The watershed has epikarst zone of 57.8 m thick on average and vadose karst zone of 115.2 m thick on average with dense faults, fractures and medium—small fracture-caves, and 76.5% of wells in this area have cumulative production of more than 5×104 t per well. The karst valleys have epikarst zone, vadose karst zone and runoff karst zone, with an average thickness of 14.6, 26.4 and 132.6 m respectively. In the runoff karst zone, the caves of subsurface river are mostly filled by fine sediment, with a filling rate up to 86.8%, and 84.9% of wells in this area have cumulative production of less than 2×104 t per well. The karst basin has no karst zone, but only fault—karst reservoirs in local fault zones, which are up to 600 m thick and closely developed within 1 km around faults. Different karst landforms have different water flowing pattern, forming different karst zone structures and resulting in differential distribution of oil and gas. The watershed has been on the direction of oil and gas migration, so medium—small sized connected fracture-caves in this area have high filling degree of oil and gas, and most wells in this area have high production. Most caves in subsurface river are filled due to strong sedimentation and transportation of the river, so the subsurface river sediment has low hydrocarbon abundance and more low production oil wells. The faults linking source rock are not only the water channels but also the oil-gas migration pathways, where the karst fractures and caves provide huge reservoir space for oil and gas accumulation.

鄂尔多斯盆地陕北地区长7段蕴藏着丰富的页岩油资源.通过扫描电镜、微米CT、二维FIB-SEM测试等高精度孔隙分析技术手段,结合大量岩心、薄片、测井等资料,对该区长7段多期砂岩叠置型页岩油储层的微观特征进行精细刻画,讨论其主要控制因素.结果 表明:研究区长7段页岩油储层孔隙以微米孔为主,半径为2.0～50 μm,喉道半径为0.3～13 μm,其孔喉为微米—纳米级与微米级喉道连通形成的众多簇状孔喉单元;其孔隙度分布在3.0％～13.0％之间,平均孔隙度为7.0％,渗透率在(0.02～0.30)×103 μm2之间,平均渗透率为0.15×10-3 μm2;其压汞曲线特征表现为排驱压力低、退汞效率高、粗喉道占比高.研究区长7段页岩油储层粒度细、塑性组分含量高、早期压实作用强烈、黏土矿物和碳酸盐胶结强烈是造成其孔隙减孔的主要因素,而溶蚀作用和绿泥石膜的保护作用具有一定的增孔效应.陕北地区长7段页岩油储层与庆城地区类比表明其具有工类页岩油勘探开发的潜力.

将岩溶地质学与地质地球物理资料相结合,对塔河地区奥陶系碳酸盐岩岩溶斜坡分水岭的组成和缝洞结构进行解剖.在岩溶水系划分的基础上,重点分析S48和S74分水岭的结构组成和缝洞发育特征,剖析出断块石林、断槽溶谷和断坡溶丘3个组成部分.结果表明:岩溶期走滑挤压背景下发育的正花状构造(地貌高带)起着分水岭作用,将塔北岩溶斜坡划分成多个岩溶流域;断块石林受断层推举处于分水岭高部位(奥陶系与巴楚组突变接触),其中裂缝和缝洞复合体发育,岩溶储层可达116 m;断槽溶谷为断层切割低部位,除裂缝/缝洞复合体发育外,奥陶系内发育4类驻水洞、槽谷内发育巨型角砾遮挡洞穴以及岩溶期堆积物,岩溶储层厚度可达136 m;断坡溶丘位于分水岭翼部,裂缝和缝洞复合体组成的岩溶储层厚度一般小于50 m.断块石林和断槽溶谷油气富集,62％的油井单井累积产油量超过20×104 t,而断坡溶丘76％的油井单井累积产油量小于10×104 t.

Based on a large number of geological and geophysical data, the formation, fracture-caves types and hydrocarbon distribution of hoodoo-upland on the Ordovician karst slope in the Tahe area, Tarim Basin, are discussed by analyzing faults and strata thickness. The hoodoo-upland was made of high peaks and narrow valleys in the Ordovician karst slope during the Early Hercynian karst period, which were distributed along the NNE positive flower structure and had inherited evolution. The fault-fractures and fracture-vugs complex were extremely developed, with a thickness of 100 m. The cumulative oil production of 60% oil wells was more than 20×104 t per well in the hoodoo-upland, where the residual thickness of the Ordovician Yingshan Formation was greater than karst depressions. Caves formed by the shelter of collapsed breccias were developed in the valleys. They were 1.6 to 13.5 m high, with a filling rate of 51.6%. The positive flower structure under the settings of strike-slip compression controlled the early formation of the hoodoo-upland on the karst slope, resulting in the differences of drainage distribution and karstification. Compared with the water-rich karst valley, the hoodoo-upland with lean water suffered weaker karstification, had thicker residual stratum, and was higher in terrain. In rainy season, the meteoric water flew and corrode along the cracks, forming a complex network of fractures and caves. Combined with inherited uplift and the effective match of the NNE deep faults, oil and gas continuously charged into the reservoir space in the upland, forming the hoodoo fracture-cave reservoir with vertically quasi continuous distribution, high hydrocarbon abundance and high production.

在岩溶缝洞储层精细描述过程中,利用钻井校正地震的方法恢复岩溶末期的岩溶地貌,发现塔河油田奥陶系岩溶区内东西两侧发育由走滑断裂形成的地貌高带(分水岭),其间为一向南开口的喇叭口状洼地,南接岩溶盆地;利用钻井、测井与地震综合解释方法,发现洼地北部较陡(坡度为2.9°左右)、南部较缓(坡度为1.5°),发育由众多支流汇聚的2条岩溶水系,西侧一条在北部以地表河为主,在南部转入地下河,东面一条地表河与地下河交替发育,由3段地表河和2段地下河组成.由于强烈的侵蚀与溶蚀作用,形成了不同规模及充填物的5种地表河,但多数地表河内没有发现河流砂岩充填,只有岩溶湖泥灰岩沉积;而地下河溶洞内充填了大量的砂岩和泥岩,成为重要的油气储层.地表河原本是有砂泥沉积的,当下游发育地下河时,洪水把原有的砂泥岩冲入地下河,形成了溶洞砂泥岩沉积,除少数下游地表河残留砂泥岩外,塔河地区奥陶系岩溶地表河基本不存在砂质储层.

岩溶储层极为复杂、研究难度大,采用注重控制因素和形成过程的岩溶相分析可以提供更可靠的地质依据.通过塔河油田主体区奥陶系岩溶储层精细描述,发现该区在岩溶期的塔北隆起挤压走滑背景下,呈一系列河流—落水洞—岩溶湖形成的峰丘—高地、残丘—谷地、岩溶湖泊—洼地等岩溶相带:形成了S74(NE向)和S48(近SN向)2个带状峰丘—高地,这两个峰丘—高地将研究区与其他岩溶相带系统隔离开来,河流穿过峰丘—高地以瀑布形式进入喇叭口状残丘—谷地,部分河流通过落水洞进入渗流岩溶带和径流岩溶带形成驻水洞和地下河,部分流入下游的岩溶湖泊—洼地.通过分析峰丘—高地和残丘—谷地岩溶相带的断层—裂缝特征、缝洞溶蚀作用、缝洞充填等岩溶相标志,并引入湖南现代岩溶相带形成过程分析,提出了岩溶相带模式,阐明了地表河与地下河及其缝洞储集空间的分布规律.研究结果为碳酸盐岩缝洞型储层预测评价和地质建模提供了岩溶地质依据.

依据大量地质和地球物理资料,从构造形变的角度出发,采用井震结合、层面追踪及三维建模的方法,对塔河油田海西运动早期岩溶地貌的形成过程进行研究.结果 发现,塔河油田古生界可分为2个形变构造层,一个是寒武系—奥陶系形变构造层,呈平缓背斜构造;另一个为石炭系—二叠系形变构造层,呈褶皱链式构造披覆于奥陶系之上.印模法不适用于塔河油田岩溶地貌的恢复,基于现今奥陶系顶面构造形态,建立构造等效圆弧曲线方程,依据不同构造阶段挤压形变压缩率,采用等弧长积分法,有效去除了岩溶期后的构造形变量,恢复了岩溶期地貌形态.海西运动早期,塔河油田奥陶系岩溶地貌北高南低,西倾东翘,其构造幅度为现今构造幅度的70％,具继承性演化特征,2个高耸带状峰丘高地与其间低缓箕状河丘谷地以及南部平坦开阔岩溶湖,共同构成了一个完整、独立的岩溶系统.

为了明确塔河油田海西早期构造演化及其对岩溶缝洞形成与油气运聚的影响,利用最新的叠前深度偏移数据及大量钻井资料,对塔河地区构造特征、水系分布、缝洞类型进行研究.通过层面追踪、精细相干技术,明确了研究区断层发育特征和构造差异演化历程,采用三维雕刻技术,刻画了地下河溶洞及中小型缝洞空间分布,多因素叠合分析认为研究区奥陶系海西早期存在差异抬升,控制着岩溶水系和缝洞分布.研究结果表明:海西早期Ⅰ幕,塔河地区呈南北向隆起,北高南低,鹰山组残余地层南厚北薄;海西早期Ⅱ幕,北西向挤压应力继续作用,构造脊线向东旋转,形成北东向鼻隆,同时鼻隆轴部发育北北东向低角度逆冲断层F3,使研究区发生差异演化;塔河六、七区沿F3断层逆冲抬升形成断鼻型峰丘高地,而塔河十、十二区相对下降,呈相对低缓的岩溶斜坡-洼地;斜坡-洼地区沉积了近200m巴楚组合岩溶角砾砂砾岩层(C1b1),岩溶水系和地下河溶洞广泛发育,油井累产小于1×104 t;峰丘高地区未沉积C1b1段,断裂与缝洞复合体密集发育,油井累产大于20×104t.因此,差异抬升形成的峰丘高地成为了岩溶斜坡上的分水岭,控制着岩溶水系的分布,使地表河与地下河围绕分水岭呈裙带式分布于斜坡-洼地区;峰丘高地与深大断裂发育区成为油气运聚优势区,斜坡-洼地中的深大断裂带可形成油气“甜点”.

尾矿坝不同部位固结状态不同,对其稳定性产生影响.以陕西汉中某尾矿坝为研究对象,运用Geostudio软件中的SLOPE模块,对尾矿坝按固结度分区,并赋予每层不同的干密度进行建模分析,对比不同方案尾矿坝安全系数的变化情况.试验结果表明:固结度逐渐增加比按照完全固结方式建立模型计算得到的安全系数小,更符合实际情况;干密度整体布置偏小的尾矿坝对固结度的变化更敏感.该研究为尾矿坝稳定性分析提供更符合工程实际的计算方法.

Based on drilling, logging, test production and dynamic monitoring data, the control effects of low-amplitude structure on hydrocarbon accumulation and development performance of ultra-low permeability reservoirs were discussed by using the methods of dense well pattern, multi-factor geological modeling, macro and micro analysis and static and dynamic analysis. The results show that the low-amplitude structure always had a significant control and influence on the distribution and accumulation of original hydrocarbon and water and the evolution trend of water flooding performance in ultra-low permeability reservoirs, and it was not only the direction of oil and gas migration, but also a favorable place for relative accumulation of oil and gas. The controlling effect of low-amplitude structure on ultra-low permeability reservoir mainly depended on its tectonic amplitude and scale; the larger the tectonic amplitude and scale, and the higher the tectonic position of the low amplitude structure, the better the reservoir characteristic parameters, oil and gas enrichment degree and development effect, and the larger the spatial scope it controlled and influenced; water cut and oil well output always fluctuated orderly with the height of the low-amplitude structure; the dynamic response of waterflooding was closely related to the relative structural position of the injection and production wells; the injected water always advanced to the low-lying area of the structure first and then moved up to the high-lying area of the structure gradually; with the continuous expansion of the flooded area, part of the oil and gas in the low-lying part of the structure was forced to be distributed to the high part of the structure, resulting in a new oil and gas enrichment, so that the dynamic reserves of oil wells in the high part increased, and the production capacity remained stable.

The influence of pore structure difference on rock electrical characteristics of reservoir and oil reservoir was analyzed taking Triassic Chang 6 reservoir in Block Yanwumao in the middle of Ordos Basin as an example. The relationship between the pore structure difference and the low resistivity oil layer was revealed and demonstrated through core observation, lab experiments, geological research, well log interpretation and trial production etc. The results show that there were two kinds of oil layers in Chang 6 oil layer set, normal oil layer and low resistivity oil layer in the region, corresponding to two types of pore structures, pore type mono-medium and micro-fracture−pore type double-medium; the development of micro-fracture changed greatly the micro-pore structure of the reservoir, and the pore structure difference had an important influence on the rock electrical characteristics of the extra-low permeability sandstone reservoir and oil reservoir; the normal oil layers had obvious characteristics of pore-type mono-medium, and were concentrated in Chang 61, Chang 622 and Chang 623; the low resistivity oil layers had obvious characteristics of micro-fracture−pore type double-medium, which were mainly distributed in Chang 621 and Chang 63. The mud filtrate penetrated deep into the oil layers along the micro-cracks, leading to sharp reduction of resistivity, and thus low resistivity of the oil layer; the low resistivity oil layers had better storage capacity and higher productivity than the normal oil layers.