A Structural Interpretation Model and Restoration of the Mesozoic Proto-basin for the Kuqa Depression,Tarim Basin

A thrust-fold belt consisting of a series of thrusts and buckling folds developed in the Mesozoic and Cenozoic strata within the Kuqa Depression,Tarim Basin.In this study,a structural interpretation model of the Kuqa Depression is established and the Mesozoic proto-basin is reconstructed on the basis of outcrop geology along the basin margin,seismic,well-log and CEMP data.The model is called‘delaminate contractional deformation',which emphasizes the decoupling between the Cenozoic,Mesozoic,pre-Mesozoic and the basin-basement within the Kuqa Depression,but there is no unified detachment.The model has a shortening amount ranging from 12 km to 16 km and the depth involved in contractional deformation ranges from 21 km to 28 km.A prototype of the Mesozoic basin reconstructed by interpretation model is a subbasin superposed on the transitional zone between the uplift at the northern edge of the Tarim Craton and the southern Tianshan orogenic wedge formed in the Hercynian orogeny.Lithospheric thermal and crustal isostatic activity after the Hercynian orogeny maybe the controlling dynamic factors of basin subsidence during the Mesozoic and early Cenozoic,the difference in rock mechanical properties between different levels,craton and orogenic wedge being the major cause of the‘delaminate contractional deformation'during the Himalayan orogeny.

Sedimentary Response of Different Fan Types to the Paleogene-Neogene Basin Transformation in the Kuqa Depression,Tarim Basin,Xinjiang Province

A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain, Kuqa Depression, Tarim Basin, Xinjiang province. Two types of fans occurred in the middle-late Paleogene Kumugeliemu and Suweiyi formations： one alluvial, and the other fan delta deposited in a lacustrine setting. Within the early Neogene Jidike Formation, coastal subaqueous fans developed, probably in a deeper water lacustrine setting. The three types of fans are stacked vertically in outcrop with the sequence in ascending order： bottom alluvial, middle fan-delta, and top suhaqueous. The subaqueous is a typical coarse-fan deposit occurring in the glutinite member of the Jidike Formation in some wells. Laterally, from the foreland to the lacustrine settings, the distribution pattern of sedimentary facies represents the same three fan types sequentially. The spatial distribution of these fans was controlled by the Paleogene-Neogene Basin transformation, and evolution with different types of fans developed in the Kuqa Depression in response. In the Paleogene, the Kuqa Depression was a rift basin where an alluvial fan was deposited in the foreland setting, which, by early Neogene, became a foreland basin when the lake level changed. With any rise in lake level, fan-deltas migrated from lacustrine to foreland settings, whereas when the lake level fell, fan migration was reversed. In the early Neogene, with increasing slope and rising lake level, fans progressed and covered the previous fan-delta and lacustrine mudstone. Eventually, subaqueous fans developed, forming the present spatial configuration of these three fan types.

Kinetic Parameters of Methane Generated from Source Rocks in the Kuqa Depression of Tarim Basin and Their Application

In a thermal simulation experiment of gold tubes of closed-system, calculating with the KINETICS and GOR-ISOTOPE KINETICS software, kinetic parameters of gas generation and methane carbon isotopic fractionation from Triassic-Jurassic hydrocarbon source rocks in the Kuqa depression of Tarim Basin are obtained. The activation energies of methane generated from Jurassic coal, Jurassic mudstone and Triassic mudstone in the Kuqa Depression are 197-268 kJ/mol, 180-260 kJ/mol and 214-289 kJ/mol, respectively, and their frequency factors are 5.265×10^13 s^-1, 9.761×10^11 s^-1 and 2.270×10^14 s^-1. This reflects their differences of hydrocarbon generation behaviors. The kinetic parameters of methane carbon isotopic fractionation are also different in Jurassic coal, Jurassic mudstone and Triassic mudstone, whose average activation energies are 228 kJ/mol, 205 kJ/mol and 231 kJ/mol, respectively. Combined with the geological background, the origin of natural gas in the Yinan-2 gas pool is discussed, and an accumulation model of natural gas is thus established. The Yinan- 2 gas is primarily derived from Jurassic coal-bearing source rocks in the Yangxia Sag. Main gas accumulation time is 5-0 Ma and the corresponding Ro is in the range from 1.25 %-1.95 %. The loss rate of natural gas is 25 %-30 %.

Geochemical analysis of mixed oil in the Ordovician reservoir of the Halahatang Depression,Tarim Basin,China

In this study,12 crude oil samples were collected and analyzed from the Ordovician reservoir in the Halahatang Depression,Tarim Basin,China.Although the density of oil samples varies considerably,based on saturated hydrocarbon gas chromatographic(GC),saturated and aromatic hydrocarbon gas chromatographic-mass spectrometric(GC/MS) and stable carbon isotopic composition analyses,all the samples are interpreted to represent a single oil population with similar characteristics in a source bed or a source kitchen,organic facies and even in oil charge history.The co-existence of a full suite of n-alkanes and acyclic isoprenoids with UCM and 25-norhopanes in the crude oil samples indicates mixing of biodegraded oil with fresher non-biodegraded oil in the Ordovician reservoir.Moreover,according to the conversion diagram of double filling ratios for subsurface mixed crude oils,biodegraded/non-biodegraded oil ratios were determined as in the range from 58/42 to 4/96.Based on oil density and oil mix ratio,the oils can be divided into two groups:Group 1,with specific density>0.88(g/cm3) and oil mix ratio>1,occurring in the north of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines,and Group 2,with specific density<0.88(g/cm3) and oil mix ratio<1,occurring in the south of the pinchout lines.Obviously,Group 2 oils with low densities and being dominated by non-biodegraded oils are better than Group 1 oils with respect to quality.It is suggested that more attention should be paid to the area in the south of the Upper Ordovician Lianglitage and Sangtamu Formation pinchout lines for further exploration.

Dibenzofuran Series in Terrestrial Source Rocks and Crude Oils and Applications to Oil-Source Rock Correlations in the Kuche Depression of Tarim Basin, NW China

Ten series of aromatic hydrocarbon compounds (biphenyl, naphthalene, phenanthrene, anthracene, retene, chrysene, benzoanthracene, dibenzofuran, fluorene, dibenzothiophene) isolated from seven Triassic and Jurassic lacustrine mudstone samples and three swamp coal samples, as well as five crude oil samples collected in the Kuche depression of the Tarim Basin, NW China, have been analysed by GC-MS techniques. It is found that the relative abundances of dibenzofuran series are higher in the three swamp coal samples than those in the lacustrine mudstone samples. Based on the similar relative abundances of dibenzofuran series, especially dibenzofuran compound, in the TICs of aromatic hydrocarbons, crude oils from wells SA3 (K), YTK5 (E, K) and QL1 (E) are thought to have been derived predominantly from the coals of the Lower Jurassic Yangxia Formation or Middle Jurassic Kezilenuer Formation, whereas those from wells YM7 (O) and YH1 (E) were derived mainly from Triassic and Jurassic lacustrine mudstones in the Kuche depression. This is the first report about how to distinguish coal-generated oils from lacustrine mudstone-generated oils in the Kuche depression in terms of the dibenzofuran series. The present paper has enlightening and directive significance for further oil-source rock correlations and oil and/or gas exploration in the Kuche depression of the Tarim Basin.

Genesis of Abnormally High Abundant Rearranged Hopanes in Condensates from the Kuqa Depression, Tarim Basin

Objective The Tarim Basin is China＇s largest ore-bearing interior basin, and contains mainly marine oils. The Kuqa depression, a secondary structural unit within the northem Tarim Basin, is composed of Mesozoic and Cenozoic clastic sedimentary rocks dominated by continental oil. Previous research suggests that the crude oils especially condensates in the Kuqa depression are rich in abnormally high abundant rearranged hopanes. On the basis of 41 condensate samples and five oil samples from the Kuqa depression, this work systematically discussed the relationship between biomarker parameters and rearranged hopanes and deeply investigated the influence of depositional environment, original source,

Formation of the Neoproterozoic Rifting Depression Groups of the Tarim Basin and its Hydrocarbon Potential: Responded to the Initial Opening of the Proto-Tethy Ocean

The largest and superimposed Tarim basin developed on the one of the three bigger craton, Tarim Craton, in China.The early Paleozoic is the heyday of its development and cratonization, and then changes to the different property basin. The reserved sedimentary strata of Neoproterozoicare recognized mainly in the local of outcrops periphery orogenic belts, but drilling core in the basin reveals them seldom. The proto-type of the initial Tarim Basinis always a mystery. The vast desert, hugethickness of sedimentary strata, multiple tectonic movements, and a low quality of deep data are the keys to getting to know him. We comprehensive field outcrops, wells, seismic reflection profiles with higher SNRs and aeromagnetic data, recognized about 20 normal fault-controlled rifting depressions of the Cryogenian and Ediacaran, which scattered throughout the basin, and developed on the Precambrian metamorphic and crystalline basement. The structural framework is clearly different from that of the overlying Phanerozoic. The rifting depressions consist of mainly half grabens, symmetrical troughs and horst-grabens. From the northeast to southwest of the basin, they are divided into three rifting depression groups(RDG)with the WNW, ENE, and NW-trends that are mainly controlled by normal faults. From the Cryogenian to Ediacaran, most of the main inherited faults to active and eventually ceased at the end of the Ediacaran or Early Cambrian, while subsidence centers appeared and migrated eastward along the faults. They formed under the NNESSW oriented and NNW-SSE-oriented extensional paleo-stress fields(relative to the present) during the Neoproterozoic, and were accompanied by clockwise shearing. According to the analysis of the activities of syn-sedimentary faults, filling sediments, magmatic events, and coordination with aeromagnetic anomalies, the tectonic properties of the fault depressions are different and are primarily continental rifts or intra-continental fault-controlled basins. The formation of the rifting depression was associated with the initial opening of the South Altun-West Kunlun Ocean and the South Tianshan Ocean, which were located at the northern and southern margins of the Tarim Block, respectively, in response to the break-up of the Supercontinent Rodinia and the initial opening of the Proto-Tethys Ocean.Inthe RDG developedfluvial, shallow marine and carbonate platform facies, accompanied with multiple phases of magma activities and glaciations during the Cryogenian and Ediacaran. The structural architectures of interfaces between the Neoproterozoic and Cambrian are mainly angular and parallel unconformities in the RDG. Over the parallel unconformities in the RDGs are beneficial for the organic-rich and/or phosphorites of the Yuertus Formation of the Lower Cambrian. The main fault belts of RDGs also controlled the small platform margin and slope break belt of in the Cambrian. The Neoproterozoic and the Lower Cambrian petroleum systems of the basin might be controlled by the RDGs in the initiation of the Tarimcraton.

Tectonic stress field and its effect on hydrocarbon migration and accumulation in Mesozoic and Cenozoic in Kuqa depression, Tarim basin

Through rock acoustic emission experiments and structural deformation analysis, the tectonic stages in Meso-Cenozoic in the Kuqa depression of the Tarim basin are firstly divided. Then, combining with rock magnetic fabric analysis and memory information, the distribution characteristics of tectonic stress field of every tectonic stage are quantificationally resumed. At the same time, according to the distribution relation of tectonic stress field of hydrocarbon for-mation stage by the finite element numerical simulation method and the known hydrocarbon reservoirs, the effects of tectonic stress field on hydrocarbon migration and accumulation are further analyzed. The Kuqa depression has mainly experienced six tectonic movements since Mesozoic. Except that the tectonic stress field of the Early Yanshan stage (208—135 Ma) showed northeast-southwest extensional stress field where the orientation of the maximum prin-cipal compressive stress (s 1) was northwest-southeast, the others were compressive stress field where the orientations of the maximum principal compressive stress (s 1) were near north-south. Along with the closure of the paleo-Tethys ocean, the Kuqa depression in the Indosinian stage (250—208 Ma) was in strong compressive circumstance with apparently big maximum principal stress (s 1) magnitude. Due to the equilibrium adjustment of interior Eurasia, the Kuqa depression in the Early Yanshan stage (208—135 Ma) was in weak extensional circumstance with appar-ently small maximum principal stress (s 1) magnitude. From the Late Yanshan stage (135—65 Ma) on, with a series of collision events occurring at the south edge of Eurasia, the Kuqa depression was in compressive circumstance again in which the maximum principal stress (s 1) magnitude was from small to big in turn. The Late Himalayan stage (2.6—0.7 Ma) was the main tectonic deformation stage with the biggest principal compressive stress (s 1) magnitude. Tectonic stress field plays a dominant role in hydrocarbon formation, it not only forms migration channels and trap structures for hydrocarbon accumulation, but also is the main drive power for hydrocarbon migration vertically along faults.

Geochemical characteristics and accumulation of marine oil and gas around Halahatang depression,Tarim Basin,China

There exists a petroleum system rich of oil and gas around Halahatang depression,where the oil and gas possess obvious local distinctions of properties in different parts.The research proved that the discovered crude oil and natural gas in the region derived mainly from O2+3 source rock,and the differences of its properties were controlled by the oil and gas filling intensity.The comprehensive study result shows the oil and gas reservoirs of the region mainly underwent three important accumulation phases:late Caledonian-Early Hercynian epoch,late Hercynian epoch,and Yanshan-Himalayan epoch. In the first phase,the oil and gas derived mostly from Cambrian source rock,which formed the primary ancient oil reservoirs,then suffered strong degradation and remained a great quantity of pyrobitumen in the high position of Tabei uplift in the present.In the second phase,the O2+3 source rock of Manjia'er depression started its generation of hydrocarbon,which accumulated in the high position of Tabei uplift afterwards,and then biodegradated to heavy oil in the late Hercynian epoch.In the last phase,the O2+3 source rock of southern Halahatang depression and margin of Manjia'er depression started its peak of generating liquid hydrocarbon,which mostly accumulated in the trap formed before the Indo-China and Yanshan epoch,and in somewhere the heavy oil suffered dilutions in various degrees or serious gas invading,to lead to obvious crude oil divergence.

Sequential extraction and compositional analysis of oil-bearing fluid inclusions in reservoir rocks from Kuche Depression, Tarim Basin

The free oils, adsorbed oils and oil-bearing fluid inclusions have been extracted separately and analyzed by GC and GC-MS in reservoir rock samples collected from the Kuche Depression. The results demonstrate that the molecular compositions of oil-bearing fluid inclusions are significantly different from those of the free oils (the current oils). Compared with the current oil, the oil-bearing fluid inclusions are characterized by relatively high values of parameters Pr/nC17 and Ph/nC18, low values of Pr/Ph, hopanes/steranes, C30-diahopane/C30-hopane and Ts/Tm, low content of C29Ts terpane and high maturities as indicated by C29 steranes 20S/(20R+20S). In addition, the oil-bearing fluid inclusions correlate very well with the oils in northern and central Tarim Basin, which were derived from Cambrian-Ordovician marine source rocks. The adsorbed oils appear to be an intermediate type between free oils and oil-bearing fluid inclusions. The above analytical data indicate that there are at least two

Recognition of Aeolian Sandstone of Lower Cretaceous in the Southwest Depression, Tarim Basin and Its Significance

Kezilesu Group of the Lower Cretaceous located along the belt of Wuqia-Wuyitakein the Southwest Depression of Tarim Basin, a sequence as thick as 1000 metres, hadbeen considered as a sediment of lake-shore delta or lake-shore sand barrier by thepredecessors in their conclusions. However, on the basis of detailed field and indoorstudies on Kangsu section of Wuqia County and Wuyitake section of Arctau County,

Structural architecture of Neoproterozoic rifting depression groups in the Tarim Basin and their formation dynamics

The Tarim Basin is the largest, oil-bearing, superimposed basin in the northwest of China. The evolution and tectonic properties of the initial Tarim Basin have been hotly disputed and remain enigmatic. The Neoproterozoic basin is covered by a vast desert and a huge-thickness of sedimentary strata, has experienced multiple tectonic movements, had a low signal to noise ratios(SNRs) of deep seismic reflection data, all of which have posed critical obstacles to research. We analysed four field outcrops, 18 wells distributed throughout the basin, 27 reprocessed seismic reflection profiles with higher SNRs across the basin and many ancillary local 2D and 3D profiles and aeromagnetic data. We found about 20 normal fault-controlled rifting depressions of the Cryogenian and Ediacaran scattered throughout the basin, which developed on the Precambrian metamorphic and crystalline basement. The structural framework is clearly different from that of the overlying Phanerozoic. The rifting depressions consist of mainly half grabens, symmetrical troughs and horst-grabens. From the northeast to southwest of the basin,they are divided into three rifting depression groups with the WNW, ENE, and NW-trends that are mainly controlled by normal faults. The maximum thicknesses of the strata are up to 4100 m. From the Cryogenian to Ediacaran, most of the main inherited faults to active and eventually ceased at the end of the Ediacaran or Early Cambrian, while subsidence centres appeared and migrated eastward along the faults. They revealed that the different parts of the Tarim continental block were in NNE-SSWoriented and NNW-SSE-oriented extensional paleo-stress fields(relative to the present) during the Neoproterozoic, and were accompanied by clockwise shearing. According to the analysis of the activities of syn-sedimentary faults, filling sediments,magmatic events, and coordination with aeromagnetic anomalies, the tectonic properties of the fault depressions are different and are primarily continental rifts or intra-continental fault-controlled basins. The rifting phases mainly occurred from 0.8–0.61 Ga.The formation of the rifting depression was associated with the initial opening of the South Altun-West Kunlun Ocean and the South Tianshan Ocean, which were located at the northern and southern margins of the Tarim Block, respectively, in response to the break-up of the Supercontinent Rodinia and the initial opening of the Proto-Tethys Ocean.

Composition and origin of molecular compounds in the condensate oils of the Dabei gas field, Tarim Basin, NW China

The Dabei gas field in the Kuqa Depression of the Tarim Basin is the most complex and deep continental condensate gas field in China. Comprehensive two-dimensional gas chromatography?time of flight mass spectrometer (GC×GC-TOFMS) analysis was conducted on five condensate oil samples from this field. The results show that the samples have n-alkane series in complete preservation and rich adamantanes. According to the methyladamantane index, the condensate oil is the product of the source rock with vitrinite reflectance (Ro) of 1.3%–1.6%. According to the gas maturity calculated through carbon isotope and vitrinite reflectance, the natural gas is corresponding to Ro of 1.3%–1.7%, reflecting that the natural gas and condensate oil are basically formed during the same period at the high maturity stage of source rock. The Dabei gas field has favorable geological conditions for hydrocarbon accumulation: thick salt rock in the Paleogene acts as a regional high-quality caprock directly overlying the high-quality sandstone reservoir of the Cretaceous, the coal source rocks have high hydrocarbon generation intensity and provide continuous oil and gas, and the subsalt thrust structures develop in rows with rich faults, providing migration pathways for oil and gas migration. These factors together controlled the formation of the Dabei gas field.

Study on sedimentation distribution based on cooperative analysis of geologic-geophysical in less well area: A case study of Suweiyi sandstone in the DB area, Kuqa Depression in Tarim Basin

The Kuqa Depression in Tarim Basin develops fan deltaic,braided river deltaic,and lacustrine sedi-mentation,espeially extensive braided river deltaic sedimentation,in the Cretaceous-Paleogene Sys-tems.However,fine sedimentary pattern of the Kuqa Depression and North Tarim Uplift belt since the Middle Cenozoic still needs to be studied.As a combination zone of the Kuqa Depression and North Tarim Uplift,the sedimentary characteristics of the DB area in the southern margin of the east of the Kuqa depression have been paid more attention.To better understand the sedimentary framework in the Kuqa Depression and North Tarim Uplift in the Mesozoic and Cenozoic,through joint geologic-geophysical study,sedime ntation of sandstone at the bottom of the Paleogene Suweiyi Formation in the DB area and its peripheral area is investigated.Sedimentary facies and sandstone distribution in the area are identified through core observation,component analysis,logging interpretation and seismic inversion.Based on seismic facies analysis,sedimentary facies distribution in the area is delineated.Results show that sandstone at the bottom of the Paleogene Suweiyi Fommation in the DB area and its peripheral area is developed in shore shallow lacustrine beach-bar facies.The beach-bar arenaceous sediments are mainly distnibuted in the southern DB area and the shallow lacustrine mudstone is developed in northern DB area,showing obvious north south di ferentiation charactenistics.

塔里木盆地库车坳陷博孜区块超深层致密砂岩储层裂缝特征及其对油气产能的影响

天然裂缝是深层致密砂岩储层重要的油气运移通道和储集空间,对库车坳陷博孜区块油气产能具有重要意义。利用岩心、薄片、成像测井以及实际生产资料,在明确塔里木盆地库车坳陷博孜区块超深层致密砂岩储层天然裂缝发育特征的基础上,厘定了天然裂缝对油气产能的影响。研究结果表明:库车坳陷博孜区块超深层储层构造裂缝发育,其中主要发育未充填-半充填的高角度剪切缝,局部发育半充填-全充填张性缝,受多期构造运动影响,区内主要发育N-S向和NW-SE向天然裂缝,部分呈近EW向;裂缝是研究区重要的储集空间和渗流通道,通过成像测井资料和试油资料构建了裂缝发育系数和裂缝有效系数用以定量表征裂缝对油气产能的影响,并建立了这两项表征参数和油气产能的定量评价图版,通过验证说明裂缝发育系数和裂缝有效系数可以较好地评价研究区裂缝的有效性,实现了通过裂缝参数对裂缝性储层品质的分类预测。研究成果不仅为研究区油气高效勘探开发提供了地质依据,同时提供了一个致密砂岩储层裂缝对油气产能影响的实例。

塔里木盆地库车坳陷克探1井重大突破与勘探意义

塔里木盆地库车坳陷克拉苏构造带克探1井在白垩系亚格列木组下段砂砾岩获得重大突破,实现了“克拉之下找克拉”的构想,对白垩系深层勘探具有重要意义。通过对克探1井成藏条件、储层特征、构造模型的深入研究,明确了克拉苏构造带侏罗系—三叠系供烃、白垩系亚格列木组裂缝型砂砾岩成储、上覆白垩系舒善河组泥岩成盖的生储盖组合,并建立了“下生上储、垂向输导、立体成藏”新模式。克探1井的成功钻探,证实了克拉苏构造带白垩系巴什基奇克组之下仍具备优越的储盖组合,并且越向深层靠近烃源岩,成藏条件越有利。同时亚格列木组断背斜圈闭成排成带,展示出巨大的勘探潜力,可形成新的天然气战略接替区。

塔里木盆地库车南斜坡托探1井油气勘探重大突破及意义

塔里木盆地库车坳陷南部斜坡带温宿—西秋地区托探1井在寒武系潜山白云岩储层获得重大突破,对库车南斜坡迎烃面多目的层潜山勘探具有重要意义。受制于地质条件复杂,该地区的油气富集规律认识不清、地质结构落实及圈闭刻画难度大,制约了潜山油气勘探。基于构造特征、潜山地层分布、生—储—盖组合、油气输导体系及勘探实践的系统分析,探讨了潜山油气成藏新模式。温宿—西秋地区古生界构造为受前冲断裂沙井子—西秋断裂和反冲断裂乌什南断裂控制的背冲式构造,F1和F2两条次级反冲断裂使得背冲构造复杂化,形成3排古生界潜山构造,每排构造自近断层到远断层区古生界潜山地层由老变新。其中寒武系潜山地层分布范围最广、呈北东东向大面积展布,潜山储层以局限台地颗粒滩相白云岩为主,受多期构造活动、长时期暴露溶蚀叠加改造,裂缝—孔洞型白云岩优质储层规模连片发育。潜山油气藏表现为三叠系黄山街组和侏罗系恰克马克组泥岩联合供烃、裂缝—孔洞型白云岩成储、上覆古近系膏盐岩封盖的生—储—盖组合样式;成藏具有“库车油气远源供烃、不整合面输导、迎烃面构造富集”的特征,主要成藏期在喜马拉雅晚期(4—1Ma)。托探1井的成功钻探,证实了温宿—西秋地区多排多类型潜山巨大的勘探潜力,重新刻画潜山圈闭面积近840km2、石油资源量约2.0×10^(8)t、天然气资源量约590×10^(8)m^(3),有望成为油气增储上产新的战略接替区。

塔里木盆地塔西南坳陷古生界成藏条件特殊性与油气勘探意义

塔里木盆地发育塔北、塔中、塔西南3大古生代古隆起。目前,已在塔北、塔中古隆起及其斜坡部位的古生界发现一系列大中型油气田。塔西南坳陷在古生代发育的古隆起(即塔西南古生代古隆起)面积最大,但近20年来的持续勘探一直未获规模性突破,主要原因是对于其成藏条件的特殊性认识不清。为此,从区域构造演化分析入手,研究了该区烃源岩的成熟度演化史、油气输导条件、沉积储层发育特征,并与塔中、塔北隆起进行对比分析,指出了其成藏条件的特殊性并揭示了油气勘探意义。研究结果表明:①古隆起演化特殊,塔中、塔北古隆起为持续发育的继承性古隆起,塔西南古隆起为迁移性古隆起,具有晚加里东期发育、晚海西期差异性调整、晚喜马拉雅期快速埋藏的演化特征。②烃源岩生烃演化史特殊,受差异性构造演化控制,塔西南坳陷下寒武统烃源岩晚喜马拉雅期以前长期处于古隆起高部位,导致其成熟期相对北部坳陷明显滞后,主力生烃期晚于北部坳陷。③油气输导系统特殊,塔西南坳陷下寒武统烃源岩生成的油气主要沿海西期和喜马拉雅期断裂输导,其期次、性质、规模与塔北、塔中隆起均存在显著差异。④储盖组合特殊,塔北、塔中隆起奥陶系风化壳储层大面积发育。受沉积环境和后期改造条件控制,塔西南古隆起奥陶系风化壳储层整体欠发育,盖层受古隆起分布的控制自西向东分别为志留系、泥盆系和石炭系;而下寒武统肖尔布拉克组白云岩储层发育,储盖组合条件较好。结论认为,4点成藏特殊性控制了塔西南坳陷成藏过程、成藏层系方面的特殊性,并决定了针对塔西南坳陷古生界油气的勘探思路应有别于塔北、塔中隆起,勘探重点应围绕盐下,寻求喜马拉雅期天然气藏的突破。

塔里木盆地博孜——大北地区被动走滑构造特征及其对裂缝发育的控制作用

库车坳陷位于南天山山前,受多期造山作用、基底先存构造与盐构造等因素的影响,构造格局复杂。明确此类复杂构造系统对裂缝发育的控制作用,对天然气勘探开发具有重要意义。基于前人的研究成果,结合最新地震、露头调查、成像与岩心资料等,系统性总结分析了博孜—大北地区构造模式及裂缝分布特征。研究结果表明,新生代以来研究区在天山造山运动与塔里木板块旋转联合控制作用下,构造系统在冲断的基础上发生被动走滑;在多条NEE向逆冲断层控制下,研究区构造体系南北方向上具有显著差异,呈现明显的分带特征;在走滑调节构造控制下,东西方向上走滑与逆冲相互转化,呈现明显的构造分段特征;断层被动走滑是有效缝发育的主控因素,断层走滑扰动应力场控制下的裂缝发育呈现分带特征;断层走滑作用下形成的断-缝系统是提高井产能的关键。此外,探讨了博孜—大北地区被动走滑构造控制下的裂缝发育规律及井产能特征,为裂缝发育机理的进一步研究提供了基础,同时也为此类油气田勘探开发提供一定的参考。