Vertical Differential Structural Deformation of the Main Strike-slip Fault Zones in the Shunbei Area,Central Tarim Basin:Structural Characteristics,Deformation Mechanisms,and Hydrocarbon Accumulation Significance

Vertical differential structural deformation(VDSD),one of the most significant structural characteristics of strike-slip fault zones(SSFZs)in the Shunbei area,is crucial for understanding deformation in the SSFZ and its hydrocarbon accumulation significance.Based on drilling data and high-precision 3-D seismic data,we analyzed the geometric and kinematic characteristics of the SSFZs in the Shunbei area.Coupled with the stratification of the rock mechanism,the structural deformations of these SSFZs in different formations were differentiated and divided into four deformation layers.According to comprehensive structural interpretations and comparisons,three integrated 3-D structural models could describe the VDSD of these SSFZs.The time-space coupling of the material basis(rock mechanism stratification),changing dynamic conditions(e.g.,changing stress-strain states),and special deformation mechanism of the en echelon normal fault array uniformly controlled the formation of the VDSD in the SSFZs of the Shunbei area.The VDSD of the SSFZs in this area controlled the entire hydrocarbon accumulation process.Multi-stage structural superimposing deformation influenced the hydrocarbon migration,accumulation,distribution,preservation,and secondary adjustments.

Application of Stable Strontium Isotope Geochemistry and Fluid Inclusion Microthermometry to Studies of Dolomitization of the Deeply Buried Cambrian Carbonate Successions in West-Central Tarim Basin, NW China

Detailed petrographic,geochemical(O-C-Sr isotopes)and fluid inclusion studies of the deeply buried Cambrian carbonates in the West-central Tarim Basin revealed three types of crystalline dolomites(fine-crystalline,nonplanar-a(s),dolomite(RD1),fine-to medium-crystalline,planar-e(s)dolomite(RD2),and medium-to coarse-crystalline,nonplanar-a dolomite(RD3)),medium-to coarsecrystalline,nonplanar-a saddle dolomite cement(CD)and early and later-stage calcite cement.The occurrence of RD1 along low-amplitude stylolites points to link with pressure dissolution by which minor Mg ions were likely released for replacive dolomitization during early-to intermediate-burial seawater dolomitization.The increasing crystal sizes of RD2 and RD3 with irregular overgrowth rims suggests intense recrystallization and replacement upon the RD1 or remaining precursor limestones by dolomitizing fluids during late intermediate burial dolomitization.The overlap ofδ^(18)O,δ^(13)C and ^(87)Sr/^(86)Sr values of RD1-RD3 and CD dolomite with coeval seawater values,suggests that the principal dolomitizing fluids that precipitated these dolomites was connate(Cambrian)seawater preserved in the host limestones/dolomites.Their high ^(87)Sr/^(86)Sr ratios suggest influx of radiogenic strontium into the Cambrian seawater.Two regimes of fluid flow are recognized in the study area:firstly,influx of magnesium-rich higher-temperature basinal brines along deep-seated faults/fractures,resulting in cementation by CD dolomite.Secondly,the incursion of meteoric waters,mixing with ascending highertemperature basinal brines,and an increase in Ca^(2+)/Mg^(2+)ratio in the fluids probably results in the precipitation of calcite cement in vugs and fractures.

Thermochemical Sulfate Reduction in the Tazhong District,Tarim Basin,Northeast China:Evidence from Formation Water and Natural Gas Geochemistry

Systematic analyses of the formation water and natural gas geochemistry in the Central Uplift of the Tarim Basin （CUTB） show that gas invasion at the late stage is accompanied by an increase of the contents of HeS and CO2 in natural gas, by the forming of the high total dissolved solids formation water, by an increase of the content of HCO3^-, relative to Cl^-, by an increase of the 2nd family ions （Ca^2＋, Mg^2＋, Sr^2＋ and Ba^2＋） and by a decrease of the content of SO4^2-, relative to Cl^-. The above phenomena can be explained only by way of thermochemicai sulfate reduction （TSR）. TSR often occurs in the transition zone of oil and water and is often described in the following reaction formula： ∑CH＋CaSO4＋H-2O→H2S＋CO2＋CaCO3. （1） Dissolved SO4^2- in the formation water is consumed in the above reaction, when HeS and CO2 are generated, resulting in a decrease of SO4^2- in the formation water and an increase of both HeS and CO2 in the natural gas. If formation water exists, the generated CO2 will go on reacting with the carbonate to form bicarbonate, which can be dissolved in the formation water, thus resulting in the enrichment of Ca^2＋ and HCO3^-. The above reaction can be described by the following equation： CO2＋HeO＋CaCO3→Ca^2＋＋2HCO3^-. The stratigraphic temperatures of the Cambrian and lower Ordovician in CUTB exceeded 120℃, which is the minimum for TSR to occur. At the same time, dolomitization, which might be a direct result of TSR, has been found in both the Cambrian and the lower Ordovician. The above evidence indicates that TSR is in an active reaction, providing a novel way to reevaluate the exploration potentials of natural gas in this district.

Lost circulation material for abnormally high temperature and pressure fractured-vuggy carbonate reservoirs in Tazhong block, Tarim Basin, NW China

To effectively solve the problem of lost circulation and well kick frequently occurring during the drilling of abnormally high temperature and pressure fractured-vuggy reservoirs in the Tazhong block, a rigid particle material, GZD, with high temperature tolerance, high rigidity(> 8 MPa) and low abrasiveness has been selected based on geological characteristics of the theft zones in the reservoirs. Through static pressure sealing experiments, its dosage when used alone and when used in combination with lignin fiber, elastic material SQD-98 and calcium carbonate were optimized, and the formula of a new type(SXM-I) of compound lost circulation material with high temperature tolerance and high strength was formed. Its performance was evaluated by compatibility test, static sealing experiment and sand bed plugging experiment. The test results show that it has good compatibility with drilling fluid used commonly and is able to plug fractures and vugs, the sealed fractures are able to withstand the static pressure of more than 9 MPa and the cumulative leakage is 13.4 mL. The mud filtrate invasion depth is only 2.5 cm in 30 min when the sand bed is made of particles with sizes between 10 mesh and 20 mesh. Overall, with good sealing property and high temperature and high pressure tolerance, the lost circulation material provides strong technical support for the safety drilling in the block.

塔里木盆地塔中隆起中北部地区断裂构造特征及演化

为系统揭示塔里木盆地塔中隆起中北部地区断裂构造特征及其成因演化,通过对该区大连片三维地震工区精细构造解析和相干体等分析,并结合区域动力背景,系统论述了该区的断裂构造类型、几何学特征、差异活动机制及其构造演化过程。研究结果表明,塔中隆起中北部发育了4类7期断裂构造,其中逆冲断裂和走滑断裂尤其发育。平面上北西向弧形逆冲断裂与北东向、北西向及南北向走滑断裂相互交切与耦合;垂向上断裂分层差异活动特征明显,下奥陶统及其以下地层,断裂发育数量多且以线形为主,中奥陶统-中下泥盆统多呈雁列式,上泥盆统-二叠系仅在塔中Ⅱ号断裂带、顺北5号断裂带西南端等地区发育少量断裂。研究区断裂活动受多期、多方向不同性质应力场所控制,经历了极其复杂的演化历史:加里东早期以塔中Ⅱ号断裂带等少量北倾正断层活动为主;加里东中期Ⅰ幕断裂活动强烈,表现为逆冲断裂与走滑断裂协同演化和相互耦合特征,走滑断裂对逆冲断裂的切割或限制作用明显;加里东中期Ⅲ幕断裂活动基本继承了加里东中期Ⅰ幕的构造格局,但在工区北部的顺北4号、5号等断裂带张扭性断裂活动特征显著;加里东晚期-海西早期,部分断裂发生继承性活动且张扭断裂发育范围进一步向南扩大;印支-燕山期,仅有少数断裂发生继承性活动;喜山期该区构造比较稳定,早期形成的复杂断裂构造进入深埋阶段。

塔里木盆地鹰山组白云岩成因与Mg同位素证据

中—下奥陶统鹰山组作为塔里木盆地中央隆起区潜在的重要勘探接替层系,其白云岩成因认识仍不清楚,因此制约了对该区域的进一步勘探。鹰山组由下至上依次发育白云岩、白云质灰岩和灰岩,表明发生了灰岩向白云岩的交代转化过程。交代白云岩的形成需要足够的含镁流体和长期的镁泵输送机制,而新兴的Mg同位素技术在示踪白云石化流体来源和迁移路径方面已经取得良好效果。因此,本研究通过系统采集鹰山组白云岩、白云质灰岩和灰岩,开展岩石学、微量元素、碳氧同位素和Mg同位素测试。实验结果显示,鹰山组发育6类岩石,分别是泥晶-微晶白云岩(D1)、粉晶-细晶白云岩(D2)、颗粒白云岩(D3)、中晶-粗晶白云岩(D4)、白云质灰岩(DL)和灰岩(L)。鹰山组碳酸盐岩的δ^(13)C_(V-PDB)值为-2.10‰~-0.37‰(平均值-1.37‰),δ^(18)O_(V-PDB)值为-7.51‰~-3.54‰(平均值-5.41‰),δ^(26)Mg值为-4.03‰~-1.28‰(平均值-2.55‰)。δ^(26)Mg、Na含量、Sr/Ba、Mn/Fe、δ^(13)C_(V-PDB)、δ^(18)O_(V-PDB)、古盐度(Z)和古温度(T)在垂向上显示出一定的联动性和系统性。通过综合分析与讨论得出以下几点认识:(1)鹰山组δ^(26)Mg值垂向变化趋势与沉积旋回具有密切联系,沉积旋回的顶部为富镁流体源区,旋回界面为流体迁移通道;(2)识别出4种Mg同位素变化趋势与白云石化流体迁移规律,即云灰互层结构(L→DL→D)、准同生白云岩结构(D1→D2)、渗透回流白云岩结构(D1→D2→D3→D4→L)和埋藏白云岩结构(D4→DL/D);(3)鹰山组白云岩形成主要与海平面周期性波动有关,海平面下降时,蒸发作用促使局限水体中富集Mg^(2+),并且富镁流体会沿着下伏高孔高渗的颗粒灰岩垂向迁移至下伏地层,有利于白云石化作用的持续进行,当富镁流体遇到孔隙度不发育的泥晶灰岩时,富镁流体无法进入矿物晶格中,白云石化作用停止。海平面上升时,局限水体转变为开阔水体,海水与富镁流体源区相互混合,降低了流体的白云石化驱动力,致使白云石化作用逐渐减弱,从而发育灰质白云岩和灰岩;(4)除受海平面控制外,深埋藏阶段经历的多期交代、重结晶或热液作用也有利于鹰山组白云岩的形成;(5)白云石化作用对鹰山组沉积储层具有建设性意义,早期白云石化作用有利于孔隙的继承和保存,而晚埋藏和热液白云石化对储层起破坏作用。

Paleostructural geomorphology of the Paleozoic central uplift belt and its constraint on the development of depositional facies in the Tarim Basin

Inclined eastward and consisting of the Hetianhe, Hetianhedong, Tazhong paleouplifts and Bachu paleoslope, the central paleouplift belt in the Tarim Basin was a large composite paleouplift and paleoslope belt with complicated palaeogeomorphic features during the Middle to early Late Ordovician. A number of paleostructural geomorphic elements have been identified in the paleouplift belt and surrounding areas, such as the high uplift belts, the faulted uplift platforms, the marginal slopes and slope break zones flanking the paleouplift belt, the surrounding shelf slopes or low relief ramps, the shelf slope break zones and deep basin plains. They exerted great influence on the development of paleogeography of the basin. The marginal slopes and slope break zones flanking the uplift belt constrained the formation and deposition of the high-energy facies including reefal and shoal deposits during the Late Ordovician, which comprise the major reservoirs of the Lower Paleozoic in the basin. Toward the end of the Ordovician, the Tazhong paleouplift hinged westward and became a westward-dipped nose as the southeastern margin of the basin was strongly compressed and uplifted. The tectono-paleogeomorphic framework of the central northern basin during the Early Silurian and the Late Devonian to Early Carboniferous changed remarkably in topography from the initial low in east and high in west to high in northeast and low in southwest. The major paleogeomorphic elements developed in these periods included the strong eroded uplift high, the uplift marginal slope, the gentle ramp of the depression margin and the depression belt. The sandstones of the lowstand and the early transgressive systems tracts were deposited along the uplift marginal slopes and the gentle ramps of the depressions comprise the prolific reservoirs in the basin. The study indicates that the distribution patterns of the unconformities within the basin are closely related to the paleogeomorphic features and evolution of the paleouplift belt. From the high uplift belt to the depression, we found the composed unconformity belts at the high uplift, the truncated and onlap triangular unconformity belts along the uplift marginal slopes, the minor angular unconformity or discontinuity belts along the transitional zones from the uplift marginal slopes to depression and the conformity belt in the central depression. The truncated and the onlap triangular unconformity belts are the favorable zones for the formation of stratigraphic trap reservoirs.

Salt-related structure and deformation mechanism of the Middle-Lower Cambrian in the middle-west parts of the Central Uplift and adjacent areas of the Tarim Basin

The salt beds of the Middle-Lower Cambrian are widespread in the middle-west parts of the Central Uplift and adjacent areas, the Tarim Basin. This paper presents the results of seismic interpretation and drilling data analysis, which discovered that the salt beds were formed in an old geologic age, deeply buried, with relatively small scaled flowing and gathering and uneven distribution. As the regional detachment layers, the salt sequences considerably control the structural deformation of the up-salt Paleozoic, forming a series of hydrocarbon traps. In due course, the salt beds of the Middle-Lower Cambrian provide excellent cap rocks and trap conditions; thus the value of exploring hydrocabon reservoir in the target strata of the sub-salt Sinian- Cambrian is greatly increased. Research has shown that the salt-related structures of the Middle-Lower Cambrian in the area mainly exist in the form of salt pillow, salt roller, up-salt anticline, salt diapir, assemblage of the salt arch and up-salt fault-block, assemblage of basement fault and salt anticline, assemblage of the basement fault-block and salt dome, assemblage of salt detachment and fault-related fold, and assemblage of basement fault-block, salt arch and up-salt imbricated thrusts. The evolution and deformation mechanisms of the salt-related structures are controlled largely by basement faulting, compressional shortening, plastic flowing and gathering, superstratum gravitation, and up-salt faulting and detaching. They are distributed in rows or belts along basement faults or fault block belts.

The Formation Mechanism and Geological Significance of Fluorite in Ordovician, Central Uplift of Tarim Basin

Based on analysisof karst fracture-vuggy filling mineralogy and geochemical fluorite in hercynian, this paper make further research about formation and significance of fluorite in central uplift of Tarim Basin. It is point out that the development of hercynian fracture-vuggy and filling succession of fracture-cave mineral was under the background of the mingling of low-temperature magma hydrotherm and the brine of upper strata. There are overlap or associate relations between generate of fluorite and buried dissolution or oil-gas migration. It was volume decreased 26.4% after calcite metasomatic by fluorite, this reaction made fluorite engender plentiful intergranular space. It’s created appreciable reservoir space. At same time, hydrotherm carried by fluorite generating could erode adjacent rock though fracture or fissure, forming irregular fracture-cave system, and also accompanied with hydrocarbon migration. The time of hydrocarbon migration and accumulation happened in late hercynian-indosinian is inosculates with the sedimentation time such as fluorite and several hydrothermal mineral.

塔里木盆地塔中低凸起古构造演化与变形特征

通过区域地质和构造地震精细研究,提出了塔里木南缘早古生代板块构造控制塔南—塔中从伸展到挤压盆地演化:寒武纪—早奥陶世板缘拉张控制了塔中北斜坡断陷构造;中奥陶世北昆仑洋盆关闭后塔中前缘隆起;晚奥陶世—晚泥盆世塔中前陆冲断与走滑构造变形。晚奥陶世塔南前陆冲断构造由东南向西北方向传播,形成塘北—塔中南—塔中5号断裂带等弧形断裂体系和塔中低凸起中西段与Ⅰ号断裂带小角度斜交的走滑断裂体系。冲断构造位移的传播受控于两个滑脱层:其一是沿寒武系内部膏盐岩的滑脱,形成弧形冲断构造,终止于塔中南缘断裂带;另一个是沿中地壳韧性变形带的滑脱,形成塔中1号断裂带东端的弧形构造带。塔中1号断裂带东段的构造变形方式主要为向北传播水平位移的断层传播褶皱和向南反向冲断的楔形构造。塔中低凸起的中西段右行走滑构造导致了向东收敛的扫帚状走滑断裂体系的形成,剖面发育花状构造。塔中低凸起的古构造演化与变形特征、构造变形样式、构造变形成因和断裂体系,是克拉通盆地内部叠合盆地深层的主要构造地质特征。

塔里木盆地中部泥盆系东河砂岩成岩作用与储集性能控制因素

根据对岩石的铸体薄片和阴极发光薄片、地层厚度、古地温梯度以及镜质体反射率等资料分析研究认为 :塔中地区东河砂岩经历了压实作用、粘土胶结、石英次生加大、碳酸盐胶结、溶蚀作用、自生高岭石沉淀等多种成岩作用 ,目前已经达到了晚期成岩阶段。这些成岩作用在塔中 4井以东和以西的地区存在较明显的差异 ,西部进入早成岩阶段B期和晚成岩阶段A期的时间较早 ,成岩演化程度较高 ,且具有下部溶蚀上部胶结的分带性 ;而东部则反之。优质储层主要分布于颗粒成分较纯、泥质含量较低、构造位置上长期处于高部位、被油气充注但未被晚期碳酸盐胶结的地区 ,即二叠纪以来长期处于构造高部位的前滨 临滨相带地区。

塔中地区志留系烃类侵位对成岩作用的影响

塔中地区志留系具有较广的沥青分布 ,为研究烃类侵位对矿物成岩作用的影响提供了良好的实例。通过岩矿观察 ,并综合油田水化学、氢氧锶同位素和流体包裹体均一化温度等资料 ,提出该区志留系烃类侵位后因淡水注入而使烃类被氧化 ,所产生的有机酸促进了钾长石、石英等矿物的溶解 ,导致了次生孔隙的发育 ;并为石英次生加大提供所必需的Si的来源。Si的质量转移可能是因浓度梯度而引起的扩散作用进行的。烃类侵位还使成岩介质还原性增强 ,使得胶结物富含还原的 2价铁 ;

塔里木盆地塔中地区下奥陶统白云岩成因

塔里木盆地塔中地区下奥陶统白云岩广泛发育,岩石类型复杂多样,主要包括结晶白云岩、残余颗粒白云岩、残余灰质白云岩、藻云岩、亮边雾心白云岩、环带白云岩及少量膏云岩等结构类型。白云岩交代现象明显,δ18O普遍为中—高负值(-3.2‰～-8.7‰);δ13C值基本为低中负值(-3‰～-0.77‰),Z值大多集中在118～123之间,成岩温度大部分集中于36～51℃范围,属于低温白云岩。白云岩具有低Mg/Ca比值,而Fe/Mn比值变化较大;白云石成分显示高铁白云石和低铁白云石之分;Sr同位素组成(0.708 8～0.709 7)普遍与海水锶同位素组成相当,但也存在个别具有较高的87Sr/86Sr比值(0.710 1～0.710 9)。结合塔中地区奥陶系古地理演变特征,白云岩化类型可划分为准同生期白云石化作用和埋藏白云石化作用。准同生期白云石化作用发生于海底(主要是潮间)成岩环境,主要是在潮坪环境或滩相环境中,其白云岩形成温度较低,具低87Sr/86Sr比值,白云石单矿物具低Fe含量;而埋藏白云岩化存在两种模式,一种为早期浅埋藏过程中的卤水回流模式,其白云岩形成温度亦较低,具高87Sr/86Sr比值,白云石单矿物具高Fe含量;另一类发生于还原性较强晚期埋藏较深的成岩环境,在埋藏阶段白云岩化程度得到进一步加强和调整,其白云岩形成温度较高,白云石捕获的包裹体均一温度较高,盐度较低。

塔里木盆地塔中北坡奥陶系碳酸盐岩岩溶储层的形成机理

塔里木盆地塔中北坡奥陶系碳酸盐岩储层已成为该盆地油气勘探的重要目标之一,目前对于该岩溶储层的溶蚀机制尚存在争议。为此,基于沉积、层序与储层综合研究成果,结合微观分析测试与宏观地震资料分析结果,将该区碳酸盐岩岩溶储层划分为石灰岩溶蚀孔洞型、白云岩孔洞型和硅质岩裂缝孔洞型3种类型,并分别探讨了其形成机理。结果表明:(1)石灰岩溶蚀孔洞型储层纵向上分布在中奥陶通鹰山组上段和一间房组,而白云岩孔洞型储层主要发育在下奥陶统蓬莱坝组和鹰山组下段且厚度较大;(2)石灰岩溶蚀孔洞型储层形成于三级层序界面(低位期)岩溶作用,而白云岩孔洞型储层则主要形成于受三级层序界面岩溶作用控制的深埋藏白云石化作用,两者均分布在三级层序界面之下的高位体系域;(3)该区硅质岩储层的发育明显受断裂控制,是深部热液沿断层对石灰岩改造的结果,硅质岩储层及其热液溶蚀缝洞系统分布在断裂附近。进而推测:塔中北坡奥陶系除了发育上述3种储层类型以外,还发育台地边缘礁滩型储层。

塔里木盆地塔中地区奥陶系碳酸盐岩埋藏溶蚀特征

塔里木盆地塔中地区奥陶系碳酸盐岩发育多种形式的岩溶作用,其中深部及热液埋藏溶蚀是形成有利储层的重要机制之一。钻井岩心、录井等分析化验资料以及宏观地质背景分析表明,塔中地区奥陶系碳酸盐岩主要发育4期埋藏溶蚀,Ⅰ,Ⅱ期溶蚀孔洞基本已被充填,Ⅲ期残留孔隙和Ⅳ期溶蚀孔洞为现今储层的有效储集空间。埋藏溶蚀作用发生的流体介质主要为有机质演化过程中形成的有机酸和二氧化碳,硫化氢可能对晚期储层形成有较大贡献。通过分析前人研究成果,认为岩浆期后热液溶蚀对本区奥陶系储层的改造作用有效,具体的影响和评价还有待进一步深入研究。

适用于塔中区块碳酸盐岩缝洞型异常高温高压储集层的钻井液承压堵漏材料

为了有效地解决塔中区块碳酸盐岩缝洞型异常高温高压储集层在钻完井过程中井漏、溢流频发的问题,在对该区块目标储集层地质特征和漏失情况进行统计分析的基础上,引入抗高温、高承压和研磨性好的刚性堵漏材料GZD,通过静态承压封堵实验对单剂加量及其与木质素纤维、弹性材料SQD-98和碳酸钙的复配加量进行了优化,形成了抗高温、高承压的新型复合堵漏材料SXM-I并通过钻井液配伍性实验、裂缝静态封堵承压实验和岩屑砂床实验对其性能进行了评价。实验结果表明,该新型复合堵漏材料与现场钻井液体系具有较好的配伍性,形成的堵漏钻井液既能封缝又能堵洞,裂缝静态承压9 MPa以上,累计漏失量仅13.4 mL;大孔径岩屑砂床30 min内侵入深度仅为2.5 cm,表现出较好的高温高压封堵性能,为该区块的顺利钻进提供了技术支撑。

塔中16-24井区奥陶系碳酸盐岩古岩溶研究

塔中 16 - 2 4井区奥陶系碳酸盐岩古岩溶主要分为侵蚀面岩溶和深部岩溶。侵蚀面岩溶在垂向上具有良好的分带性 ,自上而下大致可以分为 5个带 :风化壳 (地表岩溶 )、垂直渗流带、季节变化带、水平潜流带和深部缓流带 ,在地质历史上主要发育了 3期。深部岩溶对本区碳酸盐岩储层孔隙发育程度有很大的影响 ,同样也发育了 3期。塔中 16 - 2 4井区奥陶系碳酸盐岩古岩溶的发育受多种因素的影响 ,其中岩性、沉积相、构造、温度和古水系对古岩溶的发育起决定性的作用。

塔里木盆地中部走滑断裂系统分布格局及其成因

塔里木盆地中部(以下简称台盆区)奥陶系碳酸盐岩走滑断裂发育,控储控藏作用明显,但对于走滑断裂的成因机制尚不明晰,制约了该区油气勘探开发的进程。为此,基于三维地震解释成果,结合前人的研究成果及认识,描述了台盆区走滑断裂的总体展布格局,分析了走滑断裂的几何学特征和形成时期,并结合先存构造背景和区域构造应力场探讨了走滑断裂的形成机制,预测了潜在走滑断裂的分布规律。研究结果表明:①台盆区走滑断裂受控于先存构造,在其西南、东南和北部3面挤压应力作用下形成统一的大型走滑断裂系统,形成期为中奥陶世末期;②台盆区走滑断裂整体格局中的FⅠ5断裂最为重要,调节了东、西两侧地块的运动差异,是台盆区东、西部走滑断裂系统的分界线,而FⅠ10、FⅠ17等转换断裂则分解了南北向地层缩减,形成了断裂体系的边界,控制了断裂体系中走滑断裂的发育范围;③台盆区走滑断裂系统整体可以被划分为塔北隆起纯剪断裂体系、塔中凸起左行断裂体系、巴楚凸起右行断裂体系和阿满过渡带转换断裂体系共4个体系。结论认为:①FⅠ5、FⅠ10、FⅠ17等断裂活动强度大,对储层改造及油气疏导作用强,是目前断控区最有利的油气勘探目标;②预测FⅠ5断裂西侧的阿满过渡带可能发育与FⅠ10断裂对称的转换断层,巴楚凸起、塔中凸起西部可能发育北东向走滑断裂,是下一步油气勘探值得关注的对象。

塔中顺西区块奥陶系礁滩复合体裂缝特征及成因

对岩心、薄片、铸体薄片的观察及阴极发光、成像测井的解释结果表明,塔中顺西区块奥陶系良里塔格组礁滩复合体发育复杂的裂缝系统,按其形态可分为垂直裂缝、高角度裂缝和水平裂缝。该裂缝系统在纵向上存在明显的旋回性发育,在成因上具有多期复合叠合的特点。根据其成因,可以分为非构造成因裂缝和构造成因裂缝。根据力学属性,构造成因裂缝又可分为张性裂缝、张剪性裂缝和剪切裂缝。裂缝部分被方解石完全充填或半充填,部分未被充填而呈开启状,其中以未充填或半充填的高角度裂缝较发育,对油气储聚具有重要作用。根据裂缝充填特征和切割关系,结合区域构造演化史,构造成因裂缝可划分为晚加里东期—早海西期、晚海西期—印支期和燕山期—喜山期3个成因期次。裂缝的发育主要受岩石自身力学特性、构造应力场、构造运动、断裂活动及火山作用的控制。