North slope transition zone of Songnan-Baodao sag in Qiongdongnan Basin and its control on medium and large gas fields,South China Sea

Based on analysis of newly collected 3D seismic and drilled well data,the geological structure and fault system of Baodao sag have been systematically examined to figure out characteristics of the transition fault terrace belt and its control on the formation of natural gas reservoirs.The research results show that the Baodao sag has the northern fault terrace belt,central depression belt and southern slope belt developed,among them,the northern fault terrace belt consists of multiple transition fault terrace belts such as Baodao B,A and C from west to east which control the source rocks,traps,reservoirs,oil and gas migration and hydrocarbon enrichment in the Baodao sag.The activity of the main fault of the transition belt in the sedimentary period of Yacheng Formation in the Early Oligocene controlled the hydrocarbon generation kitchen and hydrocarbon generation potential.From west to east,getting closer to the provenance,the transition belt increased in activity strength,thickness of source rock and scale of delta,and had multiple hydrocarbon generation depressions developed.The main fault had local compression under the background of tension and torsion,giving rise to composite traps under the background of large nose structure,and the Baodao A and Baodao C traps to the east are larger than Baodao B trap.Multiple fault terraces controlled the material source input from the uplift area to form large delta sand bodies,and the synthetic transition belt of the west and middle sections and the gentle slope of the east section of the F12 fault in the Baodao A transition belt controlled the input of two major material sources,giving rise to a number of delta lobes in the west and east branches.The large structural ridge formed under the control of the main fault close to the hydrocarbon generation center allows efficient migration and accumulation of oil and gas.The combination mode and active time of the main faults matched well with the natural gas charging period,resulting in the hydrocarbon gas enrichment.Baodao A transition belt is adjacent to Baodao 27,25 and 21 lows,where large braided river delta deposits supplied by Shenhu uplift provenance develop,and it is characterized by large structural ridges allowing high efficient hydrocarbon accumulation,parallel combination of main faults and early cessation of faulting activity,so it is a favorable area for hydrocarbon gas accumulation.Thick high-quality gas reservoirs have been revealed through drilling,leading to the discovery of the first large-scale gas field in Baodo 21-1 of Baodao sag.This discovery also confirms that the north transition zone of Songnan-Baodao sag has good reservoir forming conditions,and the transition fault terrace belt has great exploration potential eastward.

Technological progress and development directions of PetroChina overseas oil and gas field production

This study reviews the development history of PetroChina’s overseas oil and gas field development technologies, summarizes the characteristic technologies developed, and puts forward the development goals and technological development directions of overseas business to overcome the challenges met in overseas oil and gas production. In the course of PetroChina’s overseas oil and gas field production practice of more than 20 years, a series of characteristic technologies suitable for overseas oil and gas fields have been created by combining the domestic mature oil and gas field production technologies with the features of overseas oil and gas reservoirs, represented by the technology for high-speed development and stabilizing oil production and controlling water rise for overseas sandstone oilfields, high efficiency development technology for large carbonate oil and gas reservoirs and foamy oil depletion development technology in use of horizontal wells for extra-heavy oil reservoirs. Based on in-depth analysis of the challenges faced by overseas oil and gas development and technological requirements, combined with the development trends of oil and gas development technologies in China and abroad, overseas oil and gas development technologies in the future are put forward, including artificial intelligence reservoir prediction and 3 D geological modeling, secondary development and enhanced oil recovery(EOR) of overseas sandstone oilfields after high speed development, water and gas injection to improve oil recovery in overseas carbonate oil and gas reservoirs, economic and effective development of overseas unconventional oil and gas reservoirs, efficient development of marine deep-water oil and gas reservoirs. The following goals are expected to be achieved: keep the enhanced oil recovery(EOR) technology for high water-cut sandstone oilfield at international advanced level, and make the development technology for carbonate oil and gas reservoirs reach the international advanced level, and the development technologies for unconventional and marine deep-water oil and gas reservoirs catch up the level of international leading oil companies quickly.

Geological characteristics of large gas provinces and large gas fields in China

Based on the examination of the global researches on oil and gas provinces and large gas fields and the analysis of the features,attributes and distribution of large gas provinces and gas fields,this paper puts forward three indicators of determining large oil and gas provinces:spatial indicator,reservoir-forming indicator and resource indicator.It classifies the gas accumulated areas and large gas provinces in China and analyzes the controlling factors on the distribution of large gas provinces and large gas fields:the lateral distribution is mainly controlled by high-energy sedimentary facies and constructive diagenetic facies,palaeo-highs and their periclinal zones,deep faults,etc,and the vertical distribution is mainly controlled by unconformities,series of evaporates and deep low-velocity highly-conductive beds,etc.It also reveals the main geological characteristics of large gas provinces and large gas fields in China.Large gas fields in four-type basins have their own characteristics and onland large gas fields are dominantly developed in foreland basins and craton basins;there are three types of gas sources,of which,coal is the main source with high gas generating intensity and varying origins;reservoir rocks of the large gas fields(provinces)are of various types and dominated generally by low-middle permeability and porosity pore-type reservoirs;structural traps and litho-stratigraphic traps coexist in Chinese large gas fields and form dense high abundance and large-area low and middle-abundance large gas fields;most of the large gas fields have late hydrocarbon-generation peaks and reservoir formation,and experienced the process of multiple-stage charging and late finalization; large gas provinces(fields)have good sealing and preservation conditions,and evaporates seals are largely developed in large and extra-large gas fields.This paper intends to shed light on the exploration and development of large gas fields(provinces)through analyzing their geological characteristics.

Sichuan super gas basin in southwest China

A sedimentary basin is classified as a super basin when its cumulative production exceeds 5 billion barrels of oil equivalent(6.82×10^(8) t of oil or 7931.66×10^(8) m^(3) of gas)and its remaining recoverable resources are at least 5 billion barrels of oil equivalent.By the end of 2019,the total output of oil and gas in Sichuan Basin had been 6569×10^(8) m^(3),the ratio of gas to oil was 80:1,and the total remaining recoverable resources reached 136404×10^(8) m^(3),which makes it as a second-tier super basin.Because the output is mainly gas,it is a super gas basin.The reason why the Sichuan Basin is a super gas basin is that it has four advantages:(1)The advantage of gas source rocks:it has the most gas source rocks(9 sets)among all the basins in China.(2)The advantage of resource quantity:it has the most total remaining recoverable resources among all the basins in China(136404×10^(8) m^(3)).(3)The advantage of large gas fields:it has the most large gas fields(27)among all the basins in China.(4)The advantage of total production:by the end of 2019,the total gas production had been 6487.8×10^(8) m^(3),which ranked the first among all the basins in China.There are four major breakthroughs in natural gas exploration in Sichuan Basin:(1)Breakthrough in shale gas:shale gas was firstly found in the Ordovician Wufeng-Silurian Longmaxi formations in China.(2)Breakthrough in tight sandstone gas:the Triassic Xu2 Member gas reservoir in Zhongba gas field is the first high recovery tight sandstone gas reservoir in China.(3)Breakthrough in giant carbonate gas fields.(4)Breakthrough in ultra-deep gas reservoir.These breakthroughs have led to important progress in different basins across the country.Super basins are classified according to three criteria:accumulative oil and gas production,remaining recoverable resources,tectonic attributes of the basin and the proportion of oil and gas in accumulative oil and gas production.

南海东部富砂砾型大中型油气田发现与启示——以珠江口盆地惠州26洼古近系恩平组为例

基于珠江口盆地惠州凹陷油气勘探实践,通过烃源岩地球化学指标测定、储集体发育形貌恢复及镜下岩矿表征、圈闭封盖指标实测比对、原油生物标志化合物提取、凝析气成因判别及成藏条件解剖,系统分析惠州26洼古近系恩平组油气资源潜力、大型砂砾岩优质储集层发育特性、断裂圈闭有效性及油气运聚成藏模式,总结南海东部古近系富砂砾型大中型油气田的形成条件及勘探方向。研究表明:(1)洼内古近系文昌组发育“面积广、厚度大”的半深湖—深湖亚相优质烃源岩,具有“早期大量生油、晚期大量排气”的典型倾油型烃源岩排烃特征,为恩平组油气成藏提供了充足的物质基础;(2)洼内断裂陡坡带与转换带联合控制下近源规模性砂砾岩体储集层非均质性强,具有“有利相带-颗粒组分-微裂缝”三元分级控储特性,等粒、低泥质(含量小于5%)、高含量长石组分及近断裂组合的(水下)分流河道有利于甜点储集层发育;(3)稳定湖泛泥岩封盖下的走滑增压型圈闭是油气保存的必备条件,斜交主应力的北东及近东西向断裂控圈效果最优;(4)优质烃源岩-断裂输导/封堵-砂砾岩储集层时空配置共同控制油气富集程度,自上而下划分为低充满带、过渡带和高充满带3个油气聚集单元,且近增压型通源断裂带河道主体区利于规模性油气富集。研究成果为珠江口盆地恩平组规模性富砂砾型油气藏勘探指明了新方向,并实现了油气勘探重大突破。

Characteristics and accumulation mode of large-scale Sinian-Cambrian gas reservoirs in the Gaoshiti-Moxi region, Sichuan Basin

The Sinian-Cambrian formations of the Sichuan Basin have favorable hydrocarbon accumulation conditions,but the exploration for large-scale gas fields is quite challenging due to old strata and multiple tectonic movements.Since the Weiyuan Sinian large gas field was found in 1964,the largest monoblock gas field(Anyue Gasfield)was discovered in the Cambrian Longwangmiao Formation of the Moxi region in 2013 with proven gas reserves of 440.1×109 m3.Total proven,probable and possible reserves exceed one trillion cubic meters in the Sinian Dengying Formation and the Cambrian Longwangmiao Formation of the Gaoshiti-Moxi region.The natural gas components,light hydrocarbons,reservoir bitumen abundance and other evidences prove that the dry natural gas was mainly derived from oil-cracking,with methane(a content of 82.65%-97.35%),ethane(a content of 0.01%-0.29%),nitrogen(a content of 0.44%-6.13%),helium(a content of 0.01%-0.06%),and hydrogen sulphide(0.62-61.11 g/m^(3)).Gas reservoir pressure increases gradually from the Sinian normal pressure(a pressure coefficient of 1.07-1.13)to high pressure(a pressure coefficient of 1.53-1.70)in the Cambrian Longwangmiao Formation.The temperature of the gas reservoir is 137.5-163 ℃.Gas reservoir traps are divided into three categories:tectonic type,tectonic-formation type and tectonic-lithologic type.The large-scale enrichment of the Sinian-Cambrian natural gas results from effective configuration of the large stable inherited palaeo-uplift during the Tongwan tectonic movement,wide distribution of ancient source rocks,high-quality reservoirs with vast pore-cavity,crude oil cracking of large palaeo-reservoirs and favorable preservation conditions.According to the palaeo-structure pattern prior to crude oil cracking of the palaeo-reservoirs,and bitumen abundance as well as the distribution characteristics of current gas reservoirs,the accumulation patterns of the cracking gas reservoir can be classified into three types:accumulation type,semi-accumulation and semi-dispersion type,and dispersion type.This understanding will play an important role in guiding the exploration of the Sinian-Cambrian natural gas exploration in the Sichuan Basin.

中国中、低丰度大油气田基本特征及形成条件

近年中国陆上发现的一批中、低丰度大型油气田具有低孔渗、小油(气)柱、低储量丰度和规模大等特点。中、低丰度油气藏大面积成藏的有利条件是:大型敞流湖盆腹地发育大型牵引流成因砂体,与烃源岩呈"三明治"结构大面积间互,为成藏奠定了基础;小油气柱、常压—低压系统降低成藏对盖层质量的要求;储集体内部非均质性强烈,气藏整体连通性差,降低了气体逸散能量,保证油气在包括地质条件相对劣质区的大范围成藏;抬升卸载环境导致气源岩解吸面状排烃,有利于晚期大面积成藏。研究表明,中国陆上大型坳陷盆地向斜区具有发现大型岩性油气藏的良好前景,这一认识已在鄂尔多斯、松辽和四川盆地向斜区油气勘探中发挥了指导作用,推动油气储量大幅度增长,未来仍有良好发展潜力。

中国大中型气田盖层特征

在对我国主要大中型气田盖层的岩性、厚度等宏观参数统计分析与排替压力、扩散系数等微观参数的实验分析基础上,对我国大中型气田盖层分布进行定性和定量研究,认为我国大中型气田盖层分布具有以泥岩为主、盖层厚度大(大部分分布在50~350 m之间)、排替压力较高(主要分布在10~30 MPa之间)、大中型气田扩散系数普遍较低(主要小于10-6cm2/s)和岩性大中型气田相对其他类型大中型气田在盖层厚度和排替压力等方面要求相对较低等特征。

东海西湖凹陷大中型油气田形成条件及勘探方向

为了解决东海西湖凹陷保俶斜坡带勘探成效差以及中央背斜带勘探效果南北差异大的问题,通过盆地分析理论体系对西湖凹陷石油地质条件进行了系统研究和重新认识,认为保俶斜坡带和中央背斜带由于构造格局及构造演化的差异形成了不同的油气成藏体系,有利成藏要素的叠合区为大中型油气田的发育区。保俶斜坡带以断陷构造层为主,晚期挤压弱,构造定型早,具有"紧邻富生烃洼陷、发育多期叠置的规模储集体、形成多类型构造-岩性复合圈闭、具有良好的垂向封盖条件以及发育网毯式高效输导体系"的有利成藏条件。近生烃洼陷的断层坡折带及地貌坡折带处形成的大型潮控三角洲砂体上倾尖灭带为大中型油气田发育区。中央背斜带经历了拗陷期强烈挤压,形成了大型反转背斜,具有"先存古构造背景、发育大型构造-岩性复合圈闭、断砂配置条件好以及具备高效储盖组合"四元控藏的特征,成藏条件叠合较好的龙井、古珍珠、湖心亭等地区是大中型气田发育区。

中国低丰度大型岩性油气田形成条件和分布规律

我国低丰度岩性油气田具有很大的资源潜力和储量规模,在中、古生代地层均有广泛的分布,具备良好的油气地质背景和成藏条件,是未来油气勘探的重点领域,其形成条件及富集规律不明.本文在大量统计分析和地质研究的基础上,探讨了低丰度大油气田的形成条件、分布特征、富集规律和未来的勘探领域.研究指出了低丰度大型岩性油气田形成的几个地质背景:大面积高丰度烃源岩;平缓的构造格局;稳定的沉积背景;大规模的沉积体系;建设性成岩环境.系统分析了油气田形成控制因素和分布规律:1陆相(或海陆交互相)大型三角洲平原—前缘主河道砂体、海相高能相带(台缘礁滩、滨岸砂体)是大型岩性油气藏的有利分布区;2次生溶蚀相、白云岩化相、风化淋滤相、绿泥石薄膜胶结相和TSR相等建设性成岩作用是优质储层及大油气田分布的有利区;3古地形(古隆起、斜坡、起伏带、鼻隆等)、断裂(层/褶/坡/陷/块)带、构造反转带、裂缝发育带和地层剥蚀尖灭带是大型油气田形成的有利构造条件和富集地区;4低丰度大型岩性油气田的分布和富集普遍受控于构造、沉积和成岩三因素控制的“甜点”.研究成果可为寻找油气勘探的后备领域和储量接替提供理论基础和科学依据.

中国各类陆相盆地斜坡区大中型岩性型油气田形成特征

我国陆相含油气盆地斜坡区大中型岩性型油气田主要发育于4类盆地之中:a)陕甘宁中生界稳定克拉通盆地具有中等油气资源丰度,盆地东北部的大型河流-三角洲砂体成为大型汇烃系统,将西南部生烃中心的油气源源不断地导向盆地东北部,在燕山Ⅳ幕东部强烈隆升改造作用下,呈南北向展布的盆地东北部三角洲砂体向东尖灭,形成大中型岩性油气田;b)松辽盆地为晚白垩世大型热衰减坳陷盆地,具有高—特高油气资源丰度,东部斜坡区发生反转掀斜改造,使纵向叠置、呈径向展布的大中型三角洲砂体与区域性断层及深部隆起复合形成大中型岩性-断层型油气田;c)准噶尔、川西、塔里木等中新生代大型前陆盆地,主力凹陷常发育大中型汇烃单元,且具有中等油气资源丰度,其斜坡区发育呈径向展布的一系列中小型裙边状扇体,配合斜坡区的大型古隆起背景、地层超覆尖灭和断层,形成大中型岩性型油气田;d)我国东部中新生界张性断陷盆地构造分割性极强,以发育小型汇烃单元为主,在具有高—特高油气资源丰度的凹陷,其斜坡区坡折带纵向叠置的大型扇三角洲及水下冲积扇体,与断层、火山岩体、泥底辟等叠合形成大中型岩性型油气藏。

跨国油气勘探形势与启示

受全球新冠肺炎疫情和中低油价的持续影响,2021年全球勘探投资继续低位运行、勘探工作量有所回落,但石油公司聚焦前沿勘探领域和勘探开发重点地区,通过加深地质认识、提升圈闭识别能力,勘探成功率持续获得提升。海域勘探尤其是深水—超深水大发现不断涌现,国际石油公司包揽的跨国大—中型油气田发现主要位于“一洋一湾一海”(大西洋两岸、墨西哥湾、南里海)。通过分析深水—超深水典型油气田,总结出三方面特点:一是深耕富油气盆地,巴西盐下时隔8年再获系列油气发现;二是积累认识、战略重返,埃尼公司在科特迪瓦盆地连获油田发现;三是开发为先、拓展周边,bp在南里海再获大气田发现。针对国际石油公司开展跨国深水—超深水勘探的做法,总结出三点启示:一是超前布局,抢占有利勘探领域,灵活进退区块;二是战略跟随,不断积累经验技术,稳步提升实力;三是自主勘探,掌握关键核心技术,实现勘探创效。建议中国石油公司仍需把握一切机会,积极获取有利勘探区块,形成资源有效储备,通过“一个转变、三个加强”逐步实现“走出去”向“走上去”的跨越。

松辽盆地主要断陷大中型油气田形成分布特征

在松辽盆地深部发育的30多个中生界断陷中,已发现的大中型油气田主要分布于贯穿盆地中央区域的北北东向孙吴—双辽岩石圈断裂两侧的徐家围子、十屋、长岭等3个富油气深断陷之中。这些深断陷的成油气地质条件和大中型油气田分布规律研究表明,大中型油气田分布在箕状深断陷生烃中心周缘发育的中央断垒带、缓坡坡折带、缓坡坡垒带、陡坡坡折带上的一批近东西向继承性鼻状隆起构造与地层超覆尖灭、岩性复合圈闭之中,其中,2个深断陷之间的中央隆起带往往是大型油气田的分布区域。为进一步发现大中型油气田,下一步应该围绕富油气深断陷的上述有利区带展开深度勘探。

中国陆相含油气盆地斜坡区大中型岩性型油气田形成条件

近 10多年来 ,陆续在鄂尔多斯盆地、松辽盆地、渤海湾盆地、准噶尔陆相盆地的斜坡区发现了一批大中型岩性型油气田 ,其形成的必要条件如下 :(1)发育多套优质烃源岩 ,具特高 -中等油气资源丰度 (10× 10 4～ 6 0×10 4t/km2 ) ;(2 )发育一定规模的汇烃单元 ,保证足够数量的油气充分地向同一个构造 -地层岩性带运移 ,在大型盆地的宽缓斜坡带 ,构造分割性较小 ,砂体能够大面积稳定分布 ;(3)多套 (扇 )三角洲前缘相砂体提供了巨大的储集空间 ,且其与优质湖相烃源岩构成不等厚 -略等厚互层 ,形成面接触、体接触 ,组成高效排液组合 ,提高了区块油气资源丰度 ;(4 )在区域性断层、深部隆起或地层超覆尖灭带的产状陡变区 ,岩性型油气藏纵向叠合好 ;(5 )反转性掀斜改造常使砂体前缘由下倾尖灭转为上翘尖灭 ,抬斜性掀斜改造则使砂体获得整体性侧向封堵 ,发育大中型岩性 -构造复合型圈闭 ;(6 ) (扇 )三角洲砂体走向与地层走向垂直或大角度斜交 ,既保证油气输导系统的通畅性 ,又使得在砂体上翘方向形成大量岩性圈闭 ;(7)圈闭形成期与油气大规模运移期的适时配置 ,有利于形成大中型岩性型油气田。

中国近海油气勘探的回顾与思考

在回顾中国近海油气勘探历程的基础上,介绍了中国近海油气勘探近年来取得的主要成果,总结了近年来中国近海油气勘探的成功做法和经验,探讨了如何在中国近海走油气勘探的可持续发展之路。

“源控论”再认识——以四川盆地天然气勘探为例

烃源作为成藏的首要条件,没有陆相、海相之分,没有地域之别,也没有油藏、气藏的不同。在海相过成熟碳酸盐岩干气区由油系烃源层、煤系烃源层形成的烃源,制约着气藏的形成与展布。其成藏模式除自源型外,更多的是异源型(多为自下而上生运聚成藏)或混源型,在纵向上跨度大且往往具多次成藏史。四川盆地大中型气田勘探经验证实,在天然气上升为主要勘探对象的地层,只有气源量大于散失量才可能成藏,所以,成藏不仅要有丰富的烃源潜量,而且要有高烃潜量值(QHGG),其值一般为下古生界>上古生界一中生界>中生界—新生界。

气藏天然气聚集速率计算方法的改进——以我国41个大中型气田为例

为了更准确地研究气藏天然气聚集的能力和速度，在前人气藏天然气聚集速率计算方法研究的基础上，考虑了气藏形成后的扩散散失量，改进了气藏天然气聚集速率的计算方法。选取我国41个大中型气田为例，利用改进前后气藏天然气聚集速率计算方法对其天然气聚集速率进行了计算，得到两种计算结果差异较大，后者为前者的1．01～3．05倍，平均为1．29倍。表明改进后方法计算得到的气藏天然气聚集速率更接近真值，更能准确地反映地下实际情况。

渤海海域盆地石油地质条件与大中型油气田分布特征

在回顾渤海海域盆地(渤海湾盆地海域部分)油气勘探历程及相关石油地质理论研究的基础上,总结了渤海海域盆地的新生代构造-沉积演化历程,分析了渤海海域盆地的石油地质条件,着重指出了与相邻陆区的显著差异。首先,渤海海域盆地两期构造旋回相应发育了沙河街组和东营组两套优质烃源岩,其中东营组烃源岩为海域盆地所特有,且晚期快速沉降有助于其成熟,因此,渤海海域盆地具有更为优越的烃源条件;其次,渤海海域盆地新近系广泛发育浅水-极浅水三角洲,是海域特有的一套勘探层系;最后,郯庐断裂带海域部分的长期持续活动最终形成了渤海海域盆地大中型油气田集中分布的油气富集带,是当前渤海油气勘探的重要领域。充分认识渤海海域盆地演化的特殊性及其独特的石油地质条件和油气富集规律,对今后的渤海油气勘探及相关研究具有参考价值。

中国近海油气勘探新进展与勘探突破方向

地质认识创新为油气勘探发现提供了理论指导和科学依据。“十四五”以来,中国近海先后在渤海海域垦利地区和辽西凸起斜坡带、文昌凹陷中央断裂带、宝岛凹陷深水区及开平凹陷斜坡带等多个领域获得油气勘探重大发现,助力中国海油“油气增储上产攻坚工程”行动方案实施,进一步坚定了中国近海坚持寻找“大中型油气田”的勘探指导思想。加大岩性油气藏和潜山油气藏勘探,加快“南海万亿大气区”和“渤海万亿大气区”建设,加强风险领域勘探,是确保中国近海未来储量稳步增长的重要措施,并指出近期年中国近海原油和天然气领域有可能取得勘探突破的方向。

珠江口盆地惠州凹陷新领域勘探重大发现及意义

珠江口盆地惠州凹陷是南海东部石油工业的摇篮,也是珠江口盆地(东部)最早取得中深层古近系油气突破的地区。近10年惠州凹陷勘探遭遇瓶颈,为了寻找新的大中型油气田,开展研讨和加强石油地质条件再评价工作。通过转变思路,坚定“老油区新作为”的勘探信心,提出“立足富洼、聚焦古近系—古潜山、拓展新领域”的勘探理念;加强研究攻关,提出富油洼陷找气新认识,惠州26洼湖相混合型母质“油气兼生,晚期快速生气”,具有较大天然气资源潜力;提出环惠州26洼“古近系—古潜山”圈闭群具有“近源强势供烃、立体网状输导”成藏模式,是勘探转型、新领域突破的首选区带。近期该区带惠州26-6“古近系—古潜山”大中型油气田勘探突破证实了高成熟富油洼陷找气新方向,揭开了惠州凹陷“古近系—古潜山”勘探新篇章,极大拓展了珠江口盆地(东部)古潜山勘探新领域。