Effect of CO_(2)flooding in an oil reservoir with strong bottom-water drive in the Tahe Oilfield,Tarim Basin,Northwest China

The dissolution and diffusion of CO_(2)in oil and water and its displacement mechanism were investigated by laboratory experiment and numerical simulation for Block 9 in the Tahe oilfield,a sandstone oil reservoir with strong bottom-water drive in Tarim Basin,Northwest China.Such parameters were analyzed as solubility ratio of CO_(2)in oil,gas and water,interfacial tension,in-situ oil viscosity distribution,remaining oil saturation distribution,and oil compositions.The results show that CO_(2)flooding could control water coning and increase oil production.In the early stage of the injection process,CO_(2)expanded vertically due to gravity differentiation,and extended laterally under the action of strong bottom water in the intermediate and late stages.The CO_(2)got enriched and extended at the oil-water interface,forming a high interfacial tension zone,which inhibited the coning of bottom water to some extent.A miscible region with low interfacial tension formed at the gas injection front,which reduced the in-situ oil viscosity by about 50%.The numerical simulation results show that enhanced oil recovery(EOR)is estimated at 5.72%and the oil exchange ratio of CO_(2)is 0.17 t/t.

Origin, hydrocarbon accumulation and oil-gas enrichment of fault-karst carbonate reservoirs: A case study of Ordovician carbonate reservoirs in South Tahe area of Halahatang oilfield, Tarim Basin

Based on comprehensive analysis of tectonic and fault evolution, core, well logging, seismic, drilling, and production data, the reservoir space characteristic, distribution, origin of fault-karst carbonate reservoir in Yueman block of South Tahe area, Halahatang oilfield, Tarim Basin, were studied systematically. And the regular pattern of hydrocarbon accumulation and enrichment was analyzed systematically based on development practice of the reservoirs. The results show that fault-karst carbonate reservoirs are distributed in the form of "body by body" discontinuously, heterogeneously and irregularly, which are controlled by the development of faults. Three formation models of fault-karst carbonate reservoirs, namely, the models controlled by the main deep-large fault, the secondary fault and the secondary internal fault, are built. The hydrocarbon accumulation and enrichment of fault-karst carbonate reservoirs is controlled by the spatiotemporal matching relation between hydrocarbon generation period and fault activity, and the size and segmentation of fault. The study results can effectively guide the well deployment and help the efficient development of fault-karst carbonate reservoirs of South Tahe area, Halahatang oilfield.

Architecture characterization of Ordovician fault-controlled paleokarst carbonate reservoirs in Tuoputai,Tahe oilfield,Tarim Basin,NW China

Based on outcrop,core,logging,seismic and production data,and the formation of fault-controlled karst reservoirs,the types and characterization of Ordovician fault-controlled karst reservoir architectures in the Tuoputai area of the Tahe oilfield are studied.According to the concept of genetic geologic body,the fault-controlled karst reservoir is divided into architecture elements of four levels,the strike-slip fault impact zone is the level-1 architecture element,the fault-controlled karst reservoir the level-2 architecture element,the fracture-cave zone(which can be further subdivided into dissolution cave,dissolution pore and vug,and fracture zones)inside the fault-controlled karst reservoir the level-3 architecture element,and fillings inside caves is the level-4 architecture element(which can be further divided based on the filling degree and lithologic types of the fillings).Specific characterization techniques have been optimized according to the characteristics of various architecture elements.The zone impacted by strike-slip fault is characterized by seismic coherence and artificial interpretation.Under the constraint of zone impacted by strike-slip fault,fault likelihood(FL)property is used to characterize the outline of fault-controlled karst reservoir.Under the constraint of fault-controlled karst reservoir outline,the internal structures are divided based on seismic texture attribute.Finally,the cavern filling pattern is interpreted based on drilling and logging data.The fault-controlled karst reservoirs can be interpreted in 3-dimensional space by architecture element levels,and the characterization technology combining log and seismic data for fault-controlled karst reservoir has been worked out,which has complemented the development theory and technologies for this kind of reservoirs in the Tahe oilfield.

Burial Dissolution of Ordovician Granule Limestone in the Tahe Oilfield of the Tarim Basin,NW China,and Its Geological Significance

With a comprehensive study on the petrology, geology and geochemistry of some Ordovician granule limestone samples in the Tahe Oiifieid of the Tarim Basin, two stages of burial dissolution were put forward as an in-source dissolution and out-source dissolution based on macro-microcosmic petrology and geochemistry features. The main differences in the two stages are in the origin and moving pass of acid fluids. Geochemical evidence indicates that burial dissolution fluids might be ingredients of organic acids, CO2 and H2S associated with organic matter maturation and hydrocarbon decomposition, and the in-source fluid came from organic matter in the granule limestone itself, but the out-source was mainly from other argillaceous carbonate rocks far away. So, the forming of a burial dissolution reservoir resulted from both in-source and the out-source dissolutions. The granule limestone firstly formed unattached pinholes under in-source dissolution in situ, and afterwards suffered wider dissolution with out-source fluids moving along unconformities, seams, faults and associate fissures. The second stage was much more important, and the mineral composition in the stratum and heat convection of the fluid were also important in forming favorable reservoirs.

Types of Karst-fractured and Porous Reservoirs in China's Carbonates and the Nature of the Tahe Oilfield in the Tarim Basin

Almost all the oil and gas reservoirs developed in marine sedimentary strata of China have undergone processes of multi-phase reservoir formation and later modification. The irregular reservoirs are classified into three types as the Naxi, Tahe and Renqiu ones, increasing successively in the development degree of karstificated pores and fissures and the connection degree of independent reservoirs. In these reservoirs, the unity in the fluid feature, pressure and oil-gas-water interface also increases successively from the Naxi to the Renqiu type. The main body of Ordovician reservoirs of the Tahe Oilfield in the Tarim Basin is a network pool rather than a stratified, massive, stratigraphically-unconformed or weathering-crust one. The fluid nature of oil, gas and water, the interface positions and the pressures, as well as the dynamic conditions of fluids within the reservoirs during the production are all different from those in stratified or massive oil and gas reservoirs. Carbonates in the Akekule uplift and the Tahe Oilfield are assemblages of various types of reservoirs, which have an overall oil-bearing potential and obvious uneven distribution. Testing and producing tests are the major means to evaluate this type of reservoirs and acid fracturing improvement is a key link in petroleum exploration and development.

Differential structure of Ordovician karst zone and hydrocarbon enrichment in paleogeomorphic units in Tahe area,Tarim Basin,NW China

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 5×10^(4) 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 2×10^(4) 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.

Hydrocarbon Inclusion Characteristics in the Cambrian-Ordovician Carbonates of the TS2 Well:Implication for Deep Hydrocarbon Exploration in the Tahe Oilfield,Tarim Basin,Northwest China

Going deep has been the strategy for the sustainable development of the Tahe Oilfield.Following the TS1 well in block 1,which revealed excellent combinations of hydrocarbon generation,migration and accumulation in the deeper parts of the Tarim Basin,the TS2 well was drilled to learn more about the prospectivity in the deeper parts of the main blocks of the Tahe Oilfield.Seventeen core samples were collected to perform fluid inclusion studies,including petrography,fluorescence microspectrometry,and microthermometry.The results show that the deeper parts of the Tahe Oilfield have a good hydrocarbon potential.The Cambrian source rocks can supply sufficient oil for not only the Cambrian reservoirs,but also for the Lower Ordovician reservoirs.The CambrianOrdovician carbonates reservoirs experienced at least three oil charging events and one late gas charging event.Oil accumulations formed in the early stage of basin evolution were likely destroyed in the late stage with deep burial,tectonic movements,or invasion of hydrothermal fluids.Therefore,the deep hydrocarbon exploration of the Tahe Oilfield,even the whole Tarim Basin,should focus on gas accumulations,although oil accumulations,especially in Cambrian reservoirs,cannot be neglected.

Formation of hoodoo-upland on Ordovician karst slope and its significance in petroleum geology in Tahe area,Tarim Basin,NW China

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 20×10^(4) 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.

Reservoir characterization of the Odovician oil and gas pools in the Tahe Oilfield, Tarim Basin, Northwest China

About 88. 1% of the proven reserves in the Tahe Oilfield in the Tarim Basin of Northwest China are trapped in Ordovician carbonate reservoirs. These reservoirs are formed by unconnected and interconnected networks of karstic porosity forming a heterogeneous and complex reservoir system. Oil, water and gas characteristics vary significantly in different portions of the Ordovician reservoir. There is no uniform oil/water contact in the field, adding to its complexity.An acid fracture treatment is beneficial in 76% of the wells, stimulating nonproductive wells and enhancing production in other wells by fracturing into unconnected reservoirs and enhancing flow pathways with acid. Acid fracture treatments should be a standard procedure for developing this and similar oil fields.

Positive carbon isotope excursions:global correlation and genesis in the Middle-Upper Ordovician in the northern Tarim Basin,Northwest China

Stable carbon isotope ratio （δ13Ccarb） analysis has been widely applied to the study of the inter-conti- nental or global marine carbonate correlation. Large-scale Cambrian-Ordovician carbonate platforms were developed in the Tarim Basin. But research on fluctuation character- istics and global correlation of δ13Ccarb is still weak. Based on conodont biostratigraphy and whole-rock δ13Ccarb data in the Tahe oil-gas field of the northern Tarim Basin, the global correlation and genesis of positive carbon isotope excursions in the Darriwilian--Early Katian was exam- ined. Three positive excursions were identified in the Tahe oil-gas field including the middle Darriwilian carbon iso- tope excursion （MDICE）, the Guttenberg carbon isotope excursion （GICE）, and a positive excursion within the Pygodus anserinus conodont zone which is named the Early Sandbian carbon isotope excursion （ESICE） in this paper. Furthermore, these positive excursions had no direct relation with sea level fluctuations. MDICE and GICE could be globally correlated. The Middle-Upper Ordovi- cian Saergan Formation source rocks of the Kalpin outcrops were in accordance with the geological time of MDICE and ESICE. GICE had close relationship with the source rock of the Lianglitag Formation in the basin.Massive organic carbon burial was an important factor controlling the genesis of these positive excursions.

Dynamic simulation of differential accumulation history of deep marine oil and gas in superimposed basin:A case study of Lower Paleozoic petroleum system of Tahe Oilfield,Tarim Basin,NW China

According to the complex differential accumulation history of deep marine oil and gas in superimposed basins,the Lower Paleozoic petroleum system in Tahe Oilfield of Tarim Basin is selected as a typical case,and the process of hydrocarbon generation and expulsion,migration and accumulation,adjustment and transformation of deep oil and gas is restored by means of reservoine-forming dynamics simulation.The thermal evolution history of the Lower Cambrian source rocks in Tahe Oilfield reflects the obvious differences in hydrocarbon generation and expulsion process and intensity in different tectonic zones,which is the main reason controlling the differences in deep oil and gas phases.The complex transport system composed of strike-slip fault and unconformity,etc.controlled early migration and accumulation and late adjustment of deep oil and gas,while the Middle Cambrian gypsum-salt rock in inner carbonate platform prevented vertical migration and accumulation of deep oil and gas,resulting in an obvious"fault-controlled"feature of deep oil and gas,in which the low potential area superimposed by the NE-strike-slip fault zone and deep oil and gas migration was conducive to accumulation,and it is mainly beaded along the strike-slip fault zone in the northeast direction.The dynamic simulation of reservoir formation reveals that the spatio-temporal configuration of"source-fault-fracture-gypsum-preservation"controls the differential accumulation of deep oil and gas in Tahe Oilfield.The Ordovician has experienced the accumulation history of multiple periods of charging,vertical migration and accumulation,and lateral adjustment and transformation,and deep oil and gas have always been in the dynamic equilibrium of migration,accumulation and escape.The statistics of residual oil and gas show that the deep stratum of Tahe Oilfield still has exploration and development potential in the Ordovician Yingshan Formation and Penglaiba Formation,and the Middle and Upper Cambrian ultra-deep stratum has a certain oil and gas resource prospect.This study provides a reference for the dynamic quantitative evaluation of deep oil and gas in the Tarim Basin,and also provides a reference for the study of reservoir formation and evolution in carbonate reservoir of paleo-craton basin.

塔里木盆地北部奥陶系海相碳酸盐岩断溶体油藏成因类型及特征再认识

前人提出的“断溶体”油藏概念,现已成为海相碳酸盐岩油气藏勘探开发的新目标、新类型。但断溶体油藏与传统的风化壳型喀斯特油藏有显著差别,断溶体储集体类型、结构特点也存在差异。研究断溶体溶蚀作用和构造破裂作用的差异性,将断溶体划分为过溶蚀残留型、破碎+强溶蚀型和强破碎+弱溶蚀型3种类型。研究表明不同成因类型的断溶体油藏,其溶蚀程度、缝洞规模、累产油量、地层能量和缝洞间连通性差异明显。过溶蚀残留型油藏的分布受风化壳不整合面及断裂带的纵向溶蚀作用控制。破碎+强溶蚀型及强破碎+弱溶蚀型油藏的形成和分布与不整合面的发育和构造位置关系不大,主要受溶蚀断裂带“破碎+溶蚀程度”控制,在溶蚀断裂带核部发育规模较大的洞穴,向两侧逐步发育裂缝-孔洞型、裂缝型储层。

塔里木盆地塔河油田塔深5井震旦系原油地球化学特征及地质意义

塔深5(TS5)井于2021年完钻,井深9 017 m,是目前亚洲第一深井,同时也是塔里木盆地台盆区第一口在8 780~8 840 m的上震旦统白云岩段获得油气突破的钻井,也是继轮探1井寒武系盐下突破后,超深层白云岩领域的又一重大发现。为了探究其油气成因,分别对TS5井震旦系凝析油和上部奥陶系重质油,及其邻区寒武系挥发油和奥陶系凝析油进行了有机地球化学特征对比。结果表明,TS5井震旦系凝析油和白云岩储层氯仿抽提物的正构烷烃系列均分布完整,指示了其生烃母质形成于强还原环境;其与奥陶系正常油-超重质油和雅克拉地区凝析油总体具有相似的生物标志化合物和碳同位素分布特征,反映均具有相似的油源;其等效镜质体反射率(Rc)值为1.7%,成熟度高于奥陶系重质油、寒武系挥发油,与邻区凝析油相当,处于高成熟阶段。综合生物标志化合物和碳同位素证据,推测TS5井震旦系油气源来自下寒武统玉尔吐斯组,其与上覆玉尔吐斯组泥页岩构成良好的储盖组合,喜马拉雅晚期来自周边较低部位玉尔吐斯组生成的高成熟凝析油气,沿斜坡运移至震旦系白云岩构造圈闭内形成了一定规模的凝析气藏。TS5井震旦系油气突破,发现了新的含油气层系,丰富了超深层油气成藏过程,为塔里木盆地超深层勘探指明了新的探索方向。

塔里木盆地塔河北部“过溶蚀残留型”断溶体发育特征及其成因

为了研究塔里木盆地塔河北部强剥蚀区海西早期古岩溶洞穴发育特征,用古地貌恢复、岩溶水系统分析、测井-岩心洞穴识别和地震属性刻画等方法进行了YQ5井区的洞穴类型样式识别、缝洞结构刻画和洞穴成因演化研究。研究结果表明:YQ5井区在塔河油田Ⅱ号和Ⅲ号古岩溶台地北部的地势平缓区,总体为多期次岩溶叠加改造后的残留地貌,主要发育幅差较小的溶峰洼地、溶丘洼地和溶丘平原,南部发育NE向展布的峰丛垄脊沟谷。与塔河油田主体区及斜坡区不同,YQ5井区地下和地表水系的流向与地貌趋势不一致,岩溶水系统遭受构造作用破坏,导致补给、径流和排泄的岩溶水循环过程不完整。YQ5井区主要发育暗河型洞穴和“过溶蚀残留型”断溶体。暗河型洞穴充填较为严重,洞穴的有效储集空间受到破坏,影响油气开发效果。岩溶台地的构造抬升造成区域侵蚀基准面的下降,顺走滑断裂的垂向侵蚀作用有利于“过溶蚀残留型”断溶体的持续发育和保存,油气开发效果好。“过溶蚀残留型”断溶体的发育主控因素为走滑断裂、地层剥蚀强度和负向地貌。与塔河古岩溶台地演化过程一致,YQ5井区的岩溶演化经历深切曲流期、岩溶改造期和下渗断溶期3个阶段。暗河型洞穴被持续改造破坏,断溶体则持续建造。

塔河油田良里塔格组迷宫型岩溶洞穴系统发育特征

为了明确塔河油田上奥陶统良里塔格组迷宫型岩溶洞穴系统的样式和结构,利用古地貌恢复、古水系刻画、测井地层对比、构造断裂解析、地震属性刻画等方法,进行了塔河油田11区的古水文地貌恢复、岩溶层组格架构建、岩溶洞穴识别和成因模式分析。结果表明:塔河油田南部加里东运动中期Ⅱ幕古地貌西北高、东南低,发育北北西—南南东向树枝状地表深切沟谷,良里塔格组发育近水平状分布、闭合管道结构及溶蚀强度较高的迷宫型岩溶洞穴系统;良里塔格组岩溶洞穴系统与澳大利亚Judbarra地区Bullita洞穴系统成因相似,属于典型的表生岩溶扩散下渗型迷宫型岩溶洞穴系统;上奥陶统恰尔巴克组泥岩段为隔水层,控制了良里塔格组迷宫型岩溶洞穴系统的侧向溶蚀作用;沟通地表水系的断裂为岩溶水主要下渗溶蚀通道,随着区域基准面下降,岩溶水沿断裂下渗进入中奥陶统,中奥陶统一间房组形成断溶体。塔河油田加里东运动中期Ⅱ幕表生岩溶“双层”迷宫型岩溶洞穴系统的认识对上奥陶统油藏开发具有重要意义。

叠合盆地深层海相油气差异富集历史的动态模拟——以塔河油田下古生界含油气系统为例

以塔里木盆地塔河油田下古生界含油气系统为例,针对叠合盆地深层海相油气复杂的差异富集历史,采用成藏动力学模拟方法进行深层油气的生排烃、运聚和调整改造的历史恢复。研究表明:①塔河油田下寒武统烃源岩的热演化史反映出不同构造带的生排烃过程及其强度具有明显不同,是导致深层油气相态差异的主要原因。②走滑断裂和不整合面等构成的复合输导体系控制深层油气早期运移聚集和后期调整,中寒武统台内膏盐岩阻止深层油气的垂向运聚,致使深层油气呈现明显的“断控”特征,其中北东向走滑断裂带和深层油气运移低势区叠加有利于汇聚成藏,且主要沿北东向走滑断裂带呈串珠状分布。③成藏动态模拟揭示“源-断-缝-膏-保”时空配置控制塔河深层油气的差异富集,奥陶系经历多期充注、垂向运聚、侧向调整改造的成藏历史,深层油气一直处于运移聚集和逸散的动态平衡中。④油气残留量统计显示塔河油田深层奥陶系鹰山组和蓬莱坝组仍具有较好的勘探开发潜力,超深层中上寒武统具有一定的油气资源前景。研究为塔里木盆地深层油气的动态定量评价提供了参考依据,也可以为古老克拉通盆地碳酸盐岩相关油气成藏演化的研究提供借鉴。

Bioturbation enhanced petrophysical properties in the Ordovician carbonate reservoir of the Tahe oilfield,Tarim Basin,NW China

Bioturbation plays an important role in enhancing the reservoir capacity of tight reservoirs.This study aims to understand the alteration mechanism and effects of bioturbation on oil and gas reservoirs,to clarify the key control factors and constraints influencing the production of bioturbation.The petrophysical characteristics of bioturbation and host sediments in carbonate rocks,such as mineral composition,pore spaces,porosity and permeability,were studied based on the detailed observation and description of the Ordovician cores from the Tahe oilfield.The effect of bioturbation on petrophysical properties of carbonate rocks were carefully analyzed.The results show:(1)Two types of bioturbation,Thalassinoides-like burrows and Planolites-like burrows,mainly occur in the Ordovician cores of the Tahe oilfield,ranging from the Lower-Middle Ordovician Yingshan Formation to the Middle Ordovician Yijianfang Formation.The burrow-fills are mainly composed of dolomite with subhedral and euhedral crystals.The host sediments mainly consist of micrite.(2)The pores in the host sediments are poorly developed and are incapable of forming effective reservoir spaces.However,well-developed intercrystalline pores among dolomites and microfractures in bioturbated sediments with better connectivity can form effective pore spaces.The results of porosity and permeability show that the host sediments without bioturbation are characterized by poor porosity and permeability.However,with the increase of bioturbation intensity,the porosity of the bioturbated sediments firstly increases and then decreases,whereas the permeability increases all the time.(3)Multiple burrows overprinted in the Ordovician carbonate rocks,forming a large-scale bioturbated carbonate rocks with lateral continuity and vertical connectivity,due to the suitable sedimentary setting,ecological conditions,favorable spatiotemporal sediment matching,and abundant organism-substrate interaction.Subsequently,diagenesis(particularly dolomitization and dissolution)has played a positive role in altering the rock fabric and improving the petrophysical properties of bioturbated carbonates.

碳酸盐岩岩溶古河道发育特征与成因演化:以塔里木盆地塔河油田12区中——下奥陶统为例

为了明确塔里木盆地塔河油田12区中—下奥陶统顶面古河道的成因,利用地震剖面分析、地震属性提取等技术,结合钻井资料刻画了古地貌、古水系发育特征,定量描述古河道的河曲特征,并基于现代岩溶理论建立了古河道成因演化模式。结果表明:中—下奥陶统顶面古河道为“深切河曲”古岩溶地貌,深切河曲特征表现为河谷主要呈“V”字形,两侧河谷坡岸对称,谷壁陡峭,发育由于截弯取直形成的离堆山、天生桥等标志性地貌;中—下奥陶统顶面古河道发育“高弯曲率”河曲形态,深切河曲的单个河曲弯曲率C值都在2.20以上,平均值为4.27,SN向河曲带弯曲率C值为1.87,EW向河曲带的弯曲率C值为2.38;塔河油田12区中—下奥陶统顶面深切河曲经历志留系沉积期、自由河曲期、深切河曲期等3个演化阶段,其成因与华力西早期运动构造作用关系密切。

塔里木盆地塔河油田S80走滑断裂发育特征及其对奥陶系储层的控制作用

综合运用岩心资料、测井资料、单井漏失段宽度和漏失量数据,利用高精度三维地震数据,结合多层相干属性开展塔里木盆地塔河地区S80走滑断裂带精细解析,厘定了其空间展布特征、活动强度特性及活动期次,探讨了S80走滑断裂对奥陶系储层的控制作用。研究结果表明:①S80走滑断裂带沿走向可分为西带、中带和东带,3个分带整体具有纵向上由寒武系至奥陶系叠接段数量显著增多、段长和段宽明显增加的特点,平面上由SW向NE张扭段规模减小、压扭段规模增强、平移段逐渐消失。具有“中带断裂活动强、两侧断裂活动弱”的特征。②S80走滑断裂带活动主要经历了加里东中期、加里东晚期—海西早期、海西晚期和印支期—喜马拉雅早期4个阶段。加里东中期和加里东晚期—海西早期为主要活动期。为“前两期左行,后两期右行”的走滑性质。③围绕S80走滑断裂带发育洞穴型、复合型(裂缝-孔洞型、孔洞-裂缝型)以及裂缝型3类储层。溶蚀孔洞的发育与走滑断裂分段性活动密切相关,活动性强的压扭段、平移段及活动性弱的张扭段主干断裂周缘是溶蚀孔洞发育的有利部位。④中奥陶统一间房组压扭段裂缝线密度高,中奥陶统一间房组至中-下奥陶统鹰山组纵向上裂缝线密度显著降低,溶蚀能力局限性大。中奥陶统一间房组张扭段裂缝线密度适中,中奥陶统一间房组至中-下奥陶统鹰山组在纵向上裂缝均较发育,溶蚀孔洞数量和规模相对更大,为储层的有利发育区。

塔河油田岩溶峡谷区伏流坍塌型古暗河缝洞系统

为研究塔河油田中—下奥陶统古岩溶发育特征,通过恢复海西运动早期古地貌和古水系,划分了岩溶峡谷区洞穴类型,构建了塔河油田岩溶峡谷区伏流坍塌型缝洞成因演化模式。研究结果表明:研究区发育海西运动早期古岩溶作用,岩溶古地貌总体北东高南西低,微地貌以低幅度溶丘、溶峰和洼地的组合为主,古水系主要为峡谷明流、伏流、暗河与干谷的组合;主干水系具有南段深切曲流峡谷、中段峡谷和北段伏流-天窗的分段结构,分支水系为树枝状暗河网络;伏流坍塌型地下河洞穴可识别,划分为暗河型、伏流型、顺河潜流型和穿洞型4种类型;研究区古暗河系统发育演化可分自由曲流型、伏流-深切曲流型和坍塌天窗伏流型。