中非Muglad盆地Sufyan凹陷现今地层残余结构特征与成因

盆地(或凹陷)结构是由盆地构造与沉积演化决定的,因此分析恢复中非Muglad盆地Sufyan凹陷构造与沉积演化过程对于认识该凹陷现今残余结构具有重要的作用。本文通过对该凹陷现今结构特征描述、地层不整合面识别与剥蚀量恢复以及构造沉降和沉积充填历史恢复,并结合区域构造演化分析,对该凹陷现今结构几何学特征、运动学过程与动力学成因及控油作用进行了研究。结果表明:Sufyan凹陷现今地层剖面主要由第一裂谷作用旋回的沉积构成。该旋回期地层约占凹陷现今沉积地层厚度的79%～81%。凹陷现今残余结构主要受三期裂谷作用差异演化控制,而受晚白垩世挤压剥蚀(厚度介于0～360m之间)的影响较小。造成凹陷三期裂谷旋回差异演化的主要原因是三期伸展应力来源、大小、方向的差异。诱发凹陷第一裂谷旋回期的应力主要来源于由中非剪切带的剪切应力转换的伸展应力。第二裂谷旋回期,中非剪切带运动方向由右旋逐渐转为左旋,造成该凹陷位置的伸展应力场减弱,并逐渐转为挤压状态,使得该演化阶段早期沉积的地层(Darfur群)后期发生反转剥蚀减薄。在该凹陷第三裂谷旋回期,东非裂谷成为非洲大陆新的构造活动区域。受此影响,中非剪切带活动逐渐停止,而红海裂谷张开产生伸展应力场与该凹陷长轴近平行,造成第三期断坳旋回在该凹陷几乎不发育,最终使该凹陷现今早断早衰型残余结构得以形成。该结构控油作用主要体现在主力成藏组合与油气优势运移方向方面。早衰型结构造成了Sufyan凹陷中组合和上组合成藏条件不佳,其下组合Abu Gabra(简称AG,下同)组自生自储自盖型成藏组合为该凹陷的主力成藏组合。挤压反转造成中部构造带形成构造高部位,成为了凹陷油气二次运移的主要指向,是凹陷油气勘探的有利区带。     

东濮凹陷盐湖相原油氮/氧化合物分布特征及其应用

东濮凹陷盐湖相原油中杂原子化合物研究薄弱。采用高分辨率质谱技术、结合色谱-质谱,对东濮凹陷盐湖相、淡水湖相原油、烃源岩中的含氮、氧化合物进行了检测。结果表明,原油中含有丰富的氮、氧化合物, N₁、O₁和O₂占绝对优势;随成熟度增加,N₁和O₁类化合物相对丰度增加、O₂类化合物相对丰度降低、氮/氧化合物的缩合度增加、烷基侧链碳数范围降低,提出了多项氮、氧化合物的成熟度辅助识别指标,建立了DBE₁₅/DBE₉-N₁和DBE₁₅⁺/DBE₁₄^--N₁与折算镜质体反射率之间的定量关系式。通过对氮、氧化合物的油-油、油-岩对比,认为东濮凹陷盐湖相原油主要来自成熟烃源岩。基于高分辨率质谱的氮、氧化合物具有重要的成熟度评价、油源对比、油气运移示踪的应用前景。     

准噶尔盆地玛18井区百口泉组基准面旋回及其对砂体的控制

三叠系百口泉组是新疆油田的主要储集层之一。应用高分辨率层序地层学基准面旋回原理,依据4 口井的岩芯资 料、122 口井的录井、测井等资料,对准噶尔盆地玛湖西斜坡玛18 井区百口泉组各级次基准面旋回界面进行了系统分析, 将百口泉组划分为1 个长期基准面旋回的上升半旋回、3 个中期基准面旋回和18 个短期基准面旋回层序。百口泉组下部发 育扇三角洲前缘亚相,上部发育前扇三角洲亚相。基准面旋回内砂体特征研究表明：百口泉组底部,可容纳空间增长速率 与沉积物供给通量的比值远远小于1 （A/S≤1）,水下分流河道砂体大面积连片展布,主要以进积的切叠式为主;百口泉组 中部,随着基准面上升,A/S 增加,砂体以接触式分布;百口泉组上部,河水动力减弱,河道砂体进一步向后退积,发育 远砂坝砂体,砂体以孤立式分布为特征。长期旋回的早中期发育水下分流河道砂体形成了主要的岩性储集砂体;末期湖侵 作用形成的湖泛泥岩为油气圈闭提供了良好的盖层。     

Orbital cyclicity in sedimentary sequence and climatic indications of C-O isotopes from Lower Cretaceous in Qingxi Sag,Jiuquan Basin,NW China

Sedimentary deposits of the Lower Cretaceous Xiagou Formation form the most significant potential hydrocarbon reservoirs in the Qingxi Sag, Jiuquan Basin(NW China). Zircon U-Pb ages of the dated basalts at the top of the Xiagou Formation give an isochron age of 115.6 Ma, and the sedimentation interval of the Xiagou Formation was speculated to range from about 125/124 Ma to 115 Ma based on paleontological research and stratigraphic correlation analysis. Here we use GR logging data as a palaeoenvironmental and palaeoclimatic proxy to conduct a detailed cyclostratigraphic study of five selected wells. Power spectra, evolutionary fast Fourier transformation and wavelet analysis all reveal significant sedimentary cycles in the Xiagou Formation. The ratios of cycle wavelengths in these stratigraphic units are 33.82 m : 7.91 m : 3.06 m : 1.79 m, which is similar to the ratio of orbital targets of 20 : 5 : 2 : 1. The ratio of 20 : 5 : 2 : 1 is interpreted as Milankovitch cycles of 405 kyr long eccentricity,100 kyr short eccentricity, 37 kyr obliquity, and 22 kyr precession cycles respectively. A high-resolution astronomical time scale is constructed by tuning the stratigraphy into target curves of orbital cycles respectively. Based on the astronomical time scale, the absolute ages of 55 samples were estimated,which are used for subsequent stable carbon and oxygen isotope stratigraphy analysis. The analysis results of the five studied wells in the Qingxi Sag indicate:(1) a negative trend of δ~(13)C values upwards in the Xiagou Formation, and(2) negative δ~(18)O values with a positive trend upwards. Both relatively heavy values and pronounced covariances of δ~(13)C values and δ~(18)O values indicate an arid-evaporationcontrolled climate during the sedimentary period of the Lower Cretaceous Xiagou Formation, Qingxi Sag, Jiuquan Basin. Moreover, positive covariances of SQK_1g_(2+3) indicate extremely high temperature, and negative covariances of SQK_1g_1 indicate a relatively low temperature.     

Discovery of Hesigewula Sag on the western margin of Da Hinggan Mountains in China and its significance in petroleum geology

With Songliao Basin in northeast China entering the middle-late stage of the exploration and development of oil and gas resources, it is urgent to open up new areas for oil and gas exploration on the periphery of the basin. Five sedimentary sags have been discovered in the western margin of the Da Hinggan Mountains through high-precision gravity, magnetic, and electrical prospecting engineering. According to the conditions of the 5 sags such as buried depth, area, and the scale of source rock, Hesigewula Sag was preferentially selected to deploy two-dimensional seismic prospecting and drilling. As a result, the stratigraphic distribution and structure of Hesigewula Sag were preliminarily ascertained, the main sedimentary facies developed in Aershan Formation-Tengger Formation of the Lower Cretaceous was summarized, and the assessment parameters of source rock of Hesigewula Sag were obtained. According to the research results, the Hesigewula Sag can be divided into 3 second-order tectonic units including the western bulge, the central sag, and the eastern bulge respectively, and the sag was formed mainly subject to the west fractures. Three sedimentary facies including fan delta facies, braided river delta facies, and lacustrine facies have been identified in the Aershan Formation-Tengger Formation of the sag. The source rock in the first member and second member of Tengger Formation in the sag features high abundance of organic matter, meeting the standards of good source rocks. The kerogen of the source rock is mainly of type II₁ – II₂. The organic matter in the source rock is characterized by low maturity and it entered the evolution stage of low maturity from the second member of Tengger Formation. Furthermore, Hesigewula Sag bears a strong similarity to other petroliferous sags in Erlian Basin in structure, sedimentation, source rock, and other characteristics. Therefore, it can be preliminarily determined that Hesigewula Sag boasts great potential for oil and gas resources.     

东濮凹陷古近系沙河街组震积岩的认识及意义

通过对东濮凹陷北部古近系沙河街组的大量岩心观察和区域沉积-构造演化的分析,认为原地形 成的震积岩普遍发育,以独具特色的软沉积物同生变形构造为主,主要有液化砂岩脉、火焰构造、枕状构造、 球-枕构造、假结核、泄水构造、液化卷曲变形构造、液化水压破裂构造和粒序断层等,并综合出原地形成的 震积岩软沉积物同生变形构造的垂向序列,自下而上依次为液化砂岩脉段、液化角砾岩段、液化卷曲变形段、 震塌岩段以及液化均一层段,而球-枕构造和液化砂岩脉的形成主要与厚层泥岩夹砂岩有关,在震积序列的各 部位均可出现。在东濮凹陷古近系沙河街组中识别出液化角砾岩、震褶岩、震塌岩 ３种类型的震积岩。震积岩 的识别,为长期以来人们对东濮凹陷古近系沙河街组砂体沉积的 “ 重力流”与 “ 牵引流”以及相应盐岩成因的 “ 深水成盐”与 “ 浅水成盐”的争论,从岩石学特征方面提供了一些肯定或否定的证据,使这些问题逐渐趋于 明朗化。另外,震积岩是潜在的有利储集体,可能为东濮凹陷的勘探开发提供一个新的方向。     

塔木察格盆地南贝尔凹陷塔Ⅱ油层组火山碎屑岩储层特征研究

蒙古国塔木察格盆地南贝尔凹陷下白垩统塔Ⅱ油层组的主要岩石类型为岩屑长石砂岩和凝灰质砂岩,其储层物性、成岩作用特征与正常沉积岩相比具有独特性。应用偏光显微镜、扫描电镜及X射线衍射分析等测试手段,对研究区储集层的岩石学特征、物性特征、成岩作用及演化等进行了详细研究。结果表明:粒间孔、杂基间微孔、粒间溶孔等是塔木察格盆地南贝尔凹陷塔Ⅱ油层组的主要孔隙类型;塔Ⅱ油层组储层成岩阶段以中成岩阶段A期为主,压实作用和胶结作用是造成储层孔隙度降低的主要因素,长石和凝灰质物质的溶蚀溶解作用有利于次生孔隙的形成。     

琼东南盆地北礁凹陷梅山组顶部丘形反射特征及成因分析

南海琼东南盆地北礁凹陷中中新统梅山组顶部丘形反射目前引起广泛关注,前人推测为生物礁、重力蠕动与底流叠加成因、等深积丘等。本文通过钻井资料、二维、三维地震资料精细刻画丘形反射（残丘）和丘间水道特征及其成因。残丘及水道在北礁凸起不发育,在边缘斜坡中部和高地较发育,且有向高地两边规模减小趋势,不具对称性,残丘和水道呈平行-亚平行近E-W向展布,局部有合并分叉现象,与北礁凸起走向呈一小角度;丘宽562~1 223 m,丘高29~87 m,丘长10 km左右,存在丘翼削蚀,水道底蚀现象。地震属性分析表明三维工区西南部残丘间水道由砂泥岩互层充填,形成长条形强振幅,而残丘为中-低振幅;地震、钻井资料分析表明丘形反射（残丘）由钙质泥岩和泥岩组成,属于半深海沉积,且残丘内部波阻抗为5.0×106~6.5×106kg/m3·m/s,低于火山岩、灰岩波阻抗,属于砂泥岩地层范畴;根据梅山组下段水道由西向东强振幅变弱、分叉、前积反射和海山附近底流（等深流）沉积剥蚀特征综合判定底流古流向自西向东,根据海山两翼地震反射特征推测底流可追溯至晚中新世早期（11.6 Ma BP）,综合分析认为,研究区中中新统梅山组丘形反射是晚中新世早期底流切割梅山组地层形成的残丘。     

Three-dimensional forward stratigraphic modelling of the gravel-to mud-rich fan-delta in the slope system of Zhanhua Sag,Bohai Bay Basin,China

An important hydrocarbon reservoir is hosted by the third member of the Shahejie Formation (Es₃) in the Zhanhua Sag, Bohai Bay Basin. Seismic stratal slices reveal different characteristics of channels and fan-delta lobes between the south (slope break belt) and southwest (gentle slope) areas combined with lithology, wire-line logs and three-dimensional (3-D) seismic data in the southern slope of Zhanhua Sag. And an excellent analogue has been provided for understanding various key depositional evolution of fan-deltas in the slope system (from base to top: Es₃^L, Es₃^M and Es₃^U). The Sedsim, a three-dimensional stratigraphic forward modelling programme, is applied to simulate the evolution of fan-deltas in the southern slope break systems and southwestern gentle slope systems of the Zhanhua Sag by considering a number of key processes and parameters affecting the fan-deltaic deposition from 43 Ma to 38.2 Ma. Modelling results indicate that depositional types and scales evolved from the thickest medium-scale gravel- or sand-rich fan deltas (43 Ma ∼41.4 Ma, Es₃^L) to the thinnest small-scale mud-rich fan deltas and lacustrine mud (41.4 Ma ∼39.8 Ma, Es₃^M), and lastly to less thicker larger-scale mixed sand-mud fan deltas (39.8 Ma ∼38.2 Ma, Es₃^U). The types of slope system, sediment supply and lake-level change are three controlling factors for determining the source-to-sink architecture of the gravel-to mud-rich fan-deltas and sediment-dispersal characteristics. This study has demonstrated that the process-based modelling approach can be effectively used to simulate complex geological environments and quantify controlling factors.     

Present temperature field and Cenozoic thermal history in the Dongpu depression,Bohai Bay Basin,North China

The Dongpu depression is located in the southern Bohai Bay Basin, North China, and it has abundant oil and gas reserves. There has been no systematic documentation of this depression's temperature field and thermal history. In this article, the present geothermal gradient and heat flow were calculated for 68 wells on the basis of 892 formation-testing data from 523 wells. Moreover, the Cenozoic thermal history was reconstructed using 466 vitrinite reflectance data from 105 wells. The results show that the Dongpu depression is characterized by a medium-temperature field between stable and active tectonic areas, with an average geothermal gradient of 34.8 °C/km and an average heat flow of 66.8 mW/m². The temperature field in the Dongpu depression is significantly controlled by the Changyuan, Huanghe, and Lanliao basement faults and thin lithosphere thickness. The geothermal gradient twice experienced high peaks. One peak was during the Shahejie 3 Formation depositional period, ranging from 45 °C/km to 48 °C/km, and the second peak was in the middle and late of the Dongying Formation depositional period, ranging from 39 °C/km to 40 °C/km, revealing that the Dongpu depression experienced two strong tectonic rifts during the geothermal gradient high peak periods. The geothermal gradient began to decrease from the Neogene, and the geothermal gradient is 31–34 °C/km at the present day. In addition, these results reveal that source rock thermal evolution is controlled by the paleo temperature field of the Dongying Formation depositional period in the Dongpu depression. This study may provide a geothermal basis for deep oil and gas resource evaluation in the Dongpu depression.