Generation of hydrocarbons in the burial history of Silurian formations in the Libyan part of the Ghadames Basin

Burial history, temperature variations, and organic matter maturation in the sedimentary rocks in the Ghadames Basin were numerically reconstructed using the GALO system for basin modeling taking into account repeated tectonic (stretching) and thermal activation events in the basin lithosphere. The modeling improved the reconstruction of the thermal history of the basin and hydrocarbon generation potential compared with previous model estimates based on the assumption of a constant temperature gradient during the whole period of basin development. In particular, the results of modeling suggest that the amplitude of Cenozoic erosion was smaller than that proposed in previous studies. The central part of the Ghadames Basin, which was considered in this study, is the western part of the Libyan sector of the basin, which underwent intense subsidence reaching 4000 m already in the Carboniferous. Given the relatively active thermal history of the basin, the modeling suggests high degrees of organic maturity in the source rocks of the Lower Silurian in the modern section of the basin and confirms the high generation potential of liquid and gaseous hydrocarbons in these formations. Significant hydrocarbon generation has occurred there since the Late Carboniferous. On the other hand, the generation potential of the Late Devonian (Frasnian) sequences is limited and strongly dependent on burial depth. The main stage of hydrocarbon generation in these rocks coincided with the Cenozoic thermal activation of the basin lithosphere. In all the areas considered, the oil window overlaps a significant portion of the modern sedimentary section of the Ghadames Basin.     

Thermal history of the Murzuq Basin,Libya, and generation of hydrocarbons in its source rocks

The history of burial, temperature variations, and organic maturation in the sedimentary rocks of the Murzuq Basin in southwestern Libya was numerically reconstructed for eight wells and one pseudowell along northeast-southwest and northwest-southeast profiles across the basin. The reconstruction was performed using the GALO system for basin modeling taking into account that the basin lithosphere underwent repeated tectonic and thermal activation. The modeling allowed us to refine the reconstructions of the thermal history of the basin and assessment of its hydrocarbon potential obtained by previous models, which assumed a constant temperature gradient during the whole period of basin development. The Murzuq Basin is characterized by moderate basement subsidence (2200–2800 m), which would have corresponded in an ordinary basin to immature or early mature organic matter. However, the history of the basin included several periods of extensive uplift and subsidence, which were accompanied by the erosion of the sedimentary cover and thermal activation of the lithosphere. This resulted in variations in organic matter maturity reached in different segments of the basin and a peculiar distribution of the degree of maturation, which is higher at the flanks of the Murzuq Basin compared with the same rocks from deeper buried zones. Our modeling indicated that the rocks of the Tanezzuft Formation could generate significant volumes of liquid hydrocarbons at some areas of the basin, but the situation is strongly dependent on the depth of rock burial and amplitude of erosion of the sedimentary cover at various areas of the basin.     

鄂尔多斯盆地西南地区蓟县系古地温演化历史及岩浆热事件的影响

深层油气成藏机理研究的首要前提是要明确烃源岩的热演化历史,这对区域油气勘探潜力的评价有着重要的指导意义。鄂尔多斯盆地西南缘蓟县系烃源岩在中生代以来的热演化史有何特征,是否受早白垩世岩浆热作用的影响,影响程度如何等问题的不明确,制约着人们对该地区中元古界烃源岩的生烃潜力的认识及进一步勘探开发的思路。通过对安口—铜城地区出露的三叠系、侏罗系及铜城岩体进行磷灰石裂变径迹、磷灰石/锆石(U-Th)/He测试,结合镜质组反射率数据,分别恢复了该地区沉积岩在中三叠世以来和侵入岩在早白垩世以来的冷却历史,结合岩浆岩体的空间分布特征和泥页岩镜质组反射率,估算蓟县系烃源岩古地温。热年代学模拟表明,蓟县系烃源岩自中生代以来先后经历了三叠纪—侏罗纪的正常埋深增温,达到了生烃温度门限,自早白垩世约130～110 Ma开始冷却,其中个别样品表现为自始新世中期至45 Ma微弱加速冷却,中新世晚期至8 Ma以来快速冷却。研究表明,中晚侏罗世是鄂尔多斯盆地西南缘蓟县系生烃的关键时期,烃源岩处于主生油温度范围,之后的早白垩世晚期岩浆侵入事件的热作用范围有限,对蓟县系烃源岩古地温的影响仅发生在局部地区。鄂尔多斯盆地西南缘...     

南海北部珠江口盆地烃源岩成因:阳江凹陷的资源潜力

本文基于最新的三维地震资料和钻井等资料,对阳江凹陷古近系烃源岩的形成条件与资源潜力进行分析和评价.作者从盆地分析入手,明确了走滑拉分的成盆模式有利于烃源岩形成,并首次利用Badlands盆地模拟揭示了阳江凹陷古地貌及沉积发育特征,指出该区属于典型有利于烃源岩的形成和发育的内源沉积;并利用三维地震资料,精细解析其断裂体系...     

永梅坳陷二叠纪煤系的热演化特征与热历史分析

中国东南部海相和近海相地层普遍遭受多次后期复杂岩浆作用的改造,因而,尽管不乏富有机质地层,但热     

莺-琼盆地海相烃源岩特征及高温高压环境有机质热演化

莺歌海盆地与琼东南盆地存在渐新统海岸平原-半封闭浅海相和中新统浅海相两套海相烃源岩。其中,渐新统烃源岩发育于琼东南盆地早第三纪半地堑,存在海岸平原和半封闭浅海两类烃源岩组合。海岸平原含煤烃源岩有机质丰度高,富含陆源有机质,具有很好的生气潜力;半封闭浅海相烃源岩TOC含量总体低于1.0%,但其规模大且存在TOC1.5%的较高丰度段,故亦具有较大的生气能力。中新统海相烃源岩主要分布于莺歌海盆地裂后热沉降形成的中央坳陷,其有机质丰度横向变化比较大,位于中央坳陷带的烃源岩有机质丰度较高,TOC大多在0.40%～2.97%之间,有机质以气型干酪根为主。盆地的高地温为有机质向天然气转化提供了有利的条件,尤其是热流体活动使浅层有机质超前熟化,但地层超压对有机质热演化也有一定的抑制作用。盆地模拟结果显示,莺-琼盆地主要凹陷烃源岩大量生气时间较晚,与圈闭形成期的时空配置好,有利于成藏。     

基于KronosFlow软件对逆冲推覆带构造-热演化的初探

盆地模拟是含油气盆地勘探评价的重要技术方法之一,然而传统的盆地建模2D模拟技术仅适用于拉张型盆地,使得挤压型盆地横向上的热史重建一直是个难题,从而制约了进一步的油气勘探。目前由法国Beicip-Franlab公司设计的KronosFlow软件突破了传统盆模软件对逆冲推覆带、盐构造和泥底辟等复杂构造的局限性,精确控制了横向和垂向上的构造位移,通过跟踪单个网格连续运动形态、恢复侧向变形量以及与TemisFlow软件无缝衔接,实现了对挤压型盆地埋藏史、热史、生排烃史以及油气运聚史的恢复。以塔里木盆地北缘柯坪逆冲推覆带和库车逆冲推覆带为例,利用KronosFlow软件定量反演了新生代以来的构造-热演化历史,并以实测数据约束并验证挤压环境下盆地模拟结果的有效性。柯坪逆冲推覆带的依木干他乌断层在40~30 Ma再次活动,断层附近志留系—泥盆系的温度大于85 ℃,柯坪塔格断层在15~10 Ma活动,断层附近志留系—泥盆系的温度小于70 ℃,寒武系（烃源岩成熟度为1.3%~1.7%）和奥陶系（烃源岩成熟度为0.7%~1.2%）烃源岩热演化程度高,生烃能力强。库车逆冲推覆带侏罗系北段温度介于50~70 ℃,南段温度介于210~230 ℃,盐构造造成地温异常,其中秋里塔格构造带膏盐岩最厚,降温效果最明显。      

Characteristics,differences and main controlling factors of source rocks in the central‐southern South China Sea Basins

The South China Sea is rich in oil and gas resources. With the increasing exploration of oil and gas resources in the northern South China Sea and the increasing demand for energy in the world, The central‐southern South China Sea have become important constituencies for oil and gas resources. The central‐southern basins of South China Sea can be divided into three types of basin groups, namely, the southern basin group (Zengmu Basin, Brunei‐Sabah Basin), the western basin group (Wan'an Basin, Zhong jiannan Basin) and the Central Basin Group (Liyue Basin, Beikang Basin, Nanweixi Basin and Palawan Basin). At present, the degree of exploration is relatively low, and the source rock has not yet formed a understanding of the system. The main source rock development time, source rock characteristics, hydrocarbon generation potential and control factors of each basin group are still unclear, which seriously restricts the exploration of oil and gas. Based on the sedimentary facies distribution and sedimentary filling evolution, combined with the geoche mical characteristics of the source rocks, the source age, organic matter type, hydrocarbon generation potential and main controlling factors of the basins in the central‐southern basins are discussed. By the detailed research on delta scale, provenance system, paleoclimate conditions, ancient vegetation development and hydroca rbon generation parent material, the main controlling factors of hydrocarbon generation potential of source rocks in each basin group are revealed.     

Analysis of the Kodiak Shelf Basin using 1D and 2D fluid flow/compaction models

The Kodiak Shelf Basin is one of the undeveloped basins in Alaska. In surrounding areas, hydrocarbon accumulations have been found. It is of interest to investigate whether there might also be hydrocarbons generated in the Kodiak Shelf Basin. Using both one- and two-dimensional fluid flow/compaction models, together with geological, geophysical and geochemical data from the Kodiak Shelf Basin, we simulate the development with time and depth of sedimentary compaction, porosity, permeability, pressure, palaeoheat flux variation and palaeotemperature variation. We then evaluate quantitatively the maturation of organic matter in the basin. The model results indicate that there was only a low likelihood of hydrocarbon generation in the basin due mainly to the combined effects of a cool palaeothermal history and low organic carbon content.     

Change in the degree of catagenesis and hydrocarbon generation in the sedimentary rocks of the South Sumatra Basin,Indonesia

Temperature and catagenetic history of the South Sumatra Basin in Indonesia is considered by the example of the sedimentary sequence of the Limau graben during its subsidence from the Oligocene to the present time. GALO system for basin modeling was applied for numerical reconstruction of six sedimentary successions in the area of holes Pandan-81, Petanang-1, Tepus-2, Tepus-1, Gambir-1, and Lembak-8 located along the profile cutting across the Limau graben. Modeling suggests significant cooling of the basemen for the last 15–20 Ma from the high initial heat flow of 105 mW/m², which is typical of axial zones of continental rifting, and significant heating of the basin lithosphere during the last 2–5 Ma. Examination of variations in tectonic subsidence of the basin confirms the possible extension of the lithosphere in the Oligocene-Miocene with an amplitude β increasing from 1.12 on the flanks of the Limau graben (Hole Lembak-8) to 1.32 in the central part of the graben (Tepus-1 and 2), Tectonic analysis indicates also the notable thermal activation of the basin in the Pliocene, Pleistocene, and Holocene. This activation is consistent with the high temperature gradient typical of the present-day sedimentary cover of the basin. Numerical modeling of the evolution of the organic matter maturity and hydrocarbon generation by main source formations of the basin confirms good prospects of the inferred source formations (Lemat, Talang Akar, and Gumai) of the South Sumatra basin for the generation of liquid hydrocarbons (HC) in the Limau Graben. It is also demonstrated that the source rocks of the Lemat Formation are ore-generating rocks in the main part of the Limau graben and are gas-generating rocks only in the deepest portions of the graben. The rocks at the base and roof of the Talang Akar Formation could be considered as highly oil-generating rocks, probably except for the upper horizons of the formation in the shallowest portions of the graben (Hole Lembak-8). Oil generation reached peak in the last 5–10 Ma. Modeling showed that intense oil generation by the Gumai Formation may be significant in the most part of the Limau graben and negligible only in the distant flanks of the graben (Hole Lembak-8).     

海拉尔盆地呼和湖凹陷下白垩统烃源岩地球化学特征及热演化史

呼和湖凹陷下白垩统烃源岩生油条件好,油气资源潜力大.利用研究区7口钻井270个热解资料和125个镜质体反射率数据,分析了下白垩统烃源岩地球化学特征及热演化史.下白垩统烃源岩有机质类型主要为Ⅲ-Ⅱ2型干酪根,现今热演化程度具有中间高、四周低的特点.主力烃源岩层南屯组属于中等-好烃源岩,在约128 Ma进入生烃门限,现今处于高成熟-生气阶段.大磨拐河组属于差-中等烃源岩,在约124 Ma进入生烃门限,现今处于中等-低成熟阶段,大磨拐河组二段烃源岩至今未进入生烃高峰.热史模拟表明呼和湖凹陷在伊敏组沉积晚期达到最大古地温,地温演化具有先升高后降低的特点.从南屯组沉积至今,地温梯度先升高到50~55℃/km,后逐渐降低为现今的35.4℃/km.早白垩世以来较高的地温场对油气生成、成藏起控制作用.包裹体均一温度结合热演化史结果表明126~87 Ma（伊敏组沉积时期）应是呼和湖凹陷油气主成藏期.晚白垩世以来盆地发生抬升,温度降低,烃源岩生烃强度减弱.      

下扬子地区热历史与海相烃源岩二次生烃潜力

下扬子地区是中国南方海相油气勘探的优选地区,针对中、古生界海相油气勘探提出了“二次生烃,晚期成藏”的部署思路。通过盆地热史恢复获得热流史,然后正演计算烃源岩成熟度史,再利用实验模拟二次生烃量版,计算区内4套主要海相烃源岩的二次生烃强度。结果表明：(1) 下扬子地区苏北、苏南、皖南地区具有不同的热演化史;(2) 二叠系和下三叠统烃源岩具有好的二次生烃潜力(150～300 mg/g),志留系烃源岩有一定的二次生烃潜力(约为120 mg/g),寒武系烃源岩几乎不具有二次生烃能力;(3) 平面上,苏南、皖南地区的二次生烃条件整体上不利,苏北各凹陷区4套海相烃源岩二次生烃强度明显大于苏南和皖南地区。     

准噶尔盆地石炭系不同类型烃源岩生烃模拟研究

选取不同沉积环境发育的多种类型的烃源岩,通过烃源岩生烃热模拟实验,对比分析不同类型烃源岩的生烃产物、产率特征及生烃演化规律。结果表明,准噶尔盆地石炭系不同沉积环境发育的烃源岩产烃能力差异较大,最大烃产率从高到低依次为:弧间盆地泥岩、弧后盆地泻湖相泥岩、残留洋盆滨浅海相泥岩、沉凝灰岩。烃源岩的产烃率大小受控于其母质与埋藏热演化条件,有机质类型越好,产烃率相对越高;而受火山作用影响越剧烈,产烃率越低。下石炭统广泛发育的弧间、弧后盆地暗色泥质岩类烃源岩具备高产烃率,为有利烃源岩发育区,乌伦古坳陷和滴水泉地区为准噶尔盆地石炭系油气勘探的有利方向。     

滨里海盆地东缘构造演化及油气成藏模式分析

滨里海盆地是中亚地区油气资源最为丰富的沉积盆地之一。本文以油气地质理论为指导,对盆地东缘的构造演化以及其油气成藏组合进行分析,认为乌拉尔造山运动对盆地东缘的构造演化造成了深刻影响。盆地东缘盐上层系的生烃条件较差,主要油气来源应为盐下层系。石炭系碳酸盐岩KT-I层和KT-II层是盆地东缘发育的良好储层。下二叠统盐层为区域性盖层,特别是对盐下油气藏起到了良好的区域封盖效果,盐相关构造圈闭类型发育。不整合面、断层和孔、洞、缝等组成复合的油气输导体系。盆地东缘的油气成藏模式主要为盐下层系的"自生自储型"和"下生上储型"以及盐上层系的"下生上储型"。     

A study of hydrocarbon generation and expulsion of the Nkporo Shales in Anambra Basin,Nigeria

This study is a contribution to our understanding of the hydrocarbon potentials of the Nkporo Shale in the Anambra Basin, Nigeria. The main objective was to simulate the hydrocarbon generation and expulsion in the Nkporo source horizons encountered in Igbariam-1, Iji-1, and Ajire-1 wells drilled in the basin, using the one-dimensional Genesis Zetaware basin modeling software. This software enabled the integration of burial and thermal influences on Nkporo source rocks with kinetic parameters, in order to define the timing of hydrocarbon generation and expulsion in relation to the main structural episodes in the basin. The Nkporo source horizons encountered in Igbariam-1 well (2,650 m) has not expelled hydrocarbons but has a remaining potential of 380 mg/gTOC. Conversely, in Iji-1 well (3,450 m) and Ajire-1 well (3,250 m), the Nkporo source rocks expelled oil of about 110–127 mg/gTOC and gas of about 85–125 mg/gTOC. The time of expulsion was in Eocene–Oligocene (51–30 My) at the rate of 10.5–11.5 mg/gTOC/My. The remaining potentials for Nkporo source rocks in Iji-1 and Ajire-1 wells are 160 and 125 mg/gTOC, respectively. The result shows an increasing trend in maturation, generation, and expulsion of hydrocarbons with increasing depth towards the southwestern part of the basin. This resulted in an increase in the generated hydrocarbon volumes to the south due to (a) increased burial depth and early maturation and (b) changing source lithofacies—more marine. The fault system linking potential reservoirs such as Owelli Sandstone to the source rock suggests a possible migration of the generated hydrocarbons to those reservoirs at that time.     

青藏高原羌塘盆地油气生成特征

本文从沉积、地球化学的角度分析了羌塘盆地的油气生成特征.羌塘盆地的沉积及古地理环境控制了多层系生油岩的形成,但主要为三叠系和侏罗系以海相沉积为主的碳酸盐烃源岩和泥质烃源岩,厚度巨大,有机质丰度高,热演化程度较高,生烃潜力大,构成了羌塘盆地主力烃源岩.综合分析认为盆地南北坳陷连接处的鞍部为含油气远景最有利区.     

Modeling of gas generation from the Alam El-Bueib formation in the Shoushan Basin, northern Western Desert of Egypt

The Shoushan Basin is an important hydrocarbon province in the northern Western Desert, Egypt, but the burial/thermal histories for most of the source rocks in the basin have not been assigned yet. In this study, subsurface samples from selected wells were collected to characterize the source rocks of Alam El-Bueib Formation and to study thermal history in the Shoushan Basin. The Lower Cretaceous Alam El-Bueib Formation is widespread in the Shoushan Basin, which is composed mainly of shales and sandstones with minor carbonate rocks deposited in a marine environment. The gas generative potential of the Lower Cretaceous Alam El-Bueib Formation in the Shoushan Basin was evaluated by Rock–Eval pyrolysis. Most samples contain sufficient type III organic matter to be considered gas prone. Vitrinite reflectance was measured at eight stratigraphic levels (Jurassic–Cretaceous). Vitrinite reflectance profiles show a general increase of vitrinite reflectance with depth. Vitrinite reflectance values of Alam El-Bueib Formation range between 0.70 and 0.87 VRr %, indicating a thermal maturity level sufficient for hydrocarbon generation. Thermal maturity and burial histories models predict that the Alam El-Bueib source rock entered the mid-mature stage for hydrocarbon generation in the Tertiary. These models indicate that the onset of gas generation from the Alam El-Bueib source rock began in the Paleocene (60 Ma), and the maximum volume of gas generation occurred during the Pliocene (3–2 Ma).     

羌塘盆地晚三叠世岩相古地理特征与烃源岩

羌塘盆地晚三叠世古地理格局是研究其沉积演化史和油气资源评价关键基础。通过地层划分对比、沉积相分析、沉积序列等方法,结合最新的地质调查及其研究结果,对羌塘盆地晚三叠世岩相古地理环境进行恢复,并讨论了上三叠统烃源岩基本特征。羌塘盆地晚三叠世受北侧碰撞造山挤压和南侧班公湖—怒江中特提斯洋盆打开双重影响,北羌塘前陆盆地逐渐萎缩消亡,南羌塘则经历走滑作用开始接受沉积。盆地北部的可可西里造山带、东部的岛链状隆起带和中部的中央隆起带为该时期盆地内三个物源区。北部边缘、中央隆起带东部边缘和盆地的中、东部地区,形成滨岸—三角洲相沉积。盆地中西部沉积较稳定的缓坡相碳酸盐岩。南羌塘坳陷的南部,沉积了向上水体逐渐变深的浅海陆棚相沉积物。此时期碳酸盐岩缓坡相区发育的烃源岩,具有高残余有机碳,高成熟度,低残余生烃潜量等基本特征,综合评价属于中等—较好烃源岩,以生气为主。推测多格错仁地区是今后油气勘探的优选目标和首选地区。     

Basin modelling of gas migration and accumulation in volcanic reservoirs in the Xujiaweizi Fault-depression,Songliao Basin

The Xujiaweizi Fault-depression of Songliao Basin has developed typical and widespread volcanic gas reservoirs. We studied the formation process of volcanic gas reservoirs by using basin modelling software and evaluated the influence of volcanic porosity, the 3D spatial and temporal field of the thermal history, and the 3D fault patterns on the basin modelling results. The 1D basin modelling results indicate that hydrocarbon generation of deep layer source rocks has a relay characteristic in time (128–0 Ma) and space (sag and slope zone) in the Xujiaweizi Fault-depression. The 2D basin modelling results show that (i) the distribution of volcanic reservoirs was controlled by the volcanic apparatus, (ii) gas source faults facilitated the vertical migration of natural gas, and (iii) the development of volcanic porosity controlled the lateral migration and accumulation of natural gas in the carrier bed. The 3D basin modelling results demonstrate that JHM, JHC, KSHC, and KSHM (source rocks) started hydrocarbon generation during the late deposition of the Denglouku Formation (113 Ma), the main hydrocarbon expulsion period was during the deposition of the late Quantou Formation (100 Ma), when the largest volcanic gas reservoir was formed; and from 84 Ma to the present (0 Ma), the area of the volcanic gas reservoir has decreased gradually. The insight gained from the basin modelling results of the volcanic gas-bearing system of the Xujiaweizi Fault-depression is that volcanic porosity, the 3D spatial and temporal field of the thermal history, and the 3D fault patterns have important influences on gas reservoir formation history and accumulation location. We are the first to establish different patterns for relations between different volcanic lithofacies porosity and burial depth, and we expect to provide a reference for basin model of other volcanic oil- and gas-bearing systems.     

柴达木盆地石炭系油气调查最新进展

柴达木盆地石炭系是海相油气勘探的新领域,通过对柴达木盆地石炭系油气地质条件进行调查,评价其资源潜力,为该区寻找油气战略接替区提供科学依据。以柴达木盆地石炭系为主要目标,通过调查和研究,首次获得柴达木盆地石炭系油气流,在柴达木盆地古生界海相新层系油气方面取得重要发现;综合区域调查、平衡剖面反演及镜质体反射率等分析,获取柴达木盆地主要构造运动期次;结合盆地模拟技术,重建了石炭系埋藏史,分析了柴达木盆地德令哈坳陷石炭系烃源岩油气地化指标,研究了烃源岩生烃演化史。研究表明:柴达木盆地德令哈坳陷石炭系烃源岩广泛发育,有机质丰度较高,埋深较大,但未发生变质,处于成熟-高成熟阶段;德令哈坳陷石炭系埋藏史主要表现为快速埋藏期、稳定期与强烈抬升剥蚀期,新生代以来沉降史与抬升剥蚀史存在着差异;石炭系烃源岩热演化史主要表现为“存在二次生烃,晚期生烃为主”的特点,主要受该区构造运动控制;柴达木盆地热演化总体表现为缓慢降低的趋势,主要受控于柴达木盆地岩浆热事件与构造活动。调查分析表明,新层系石炭系油气条件良好,资源前景广阔,是柴达木盆地下一步勘探的接替层系。