Origin and Source of Deep Natural Gas in Nanpu sag, Bohai Bay Basin, China

Natural gas exploration in Nanpu sag, Bohai Bay Basin, has achieved breakthroughs in recent years, and a number of natural gas and condensate wells with high yield have been found in several structures in the beach area. Daily gas production of single wells is up to 170,000 m3, and high-yield wells are mainly distributed in？the Nanpu No. 1 structural belt.？Studies have shown that these natural gases are mainly hydrocarbon gases, with methane content about 80% to 90% and ethane 6%-9%, so they are mainly wet gas; and non-hydrocarbons are at a low level.？Carbon isotopes of methane range from -42‰ to -36‰, and ethane from -28‰ to -26‰. Calculated maturity based on the relationship between δ13C and Ro of natural gas, the gases are equivalent to those generated from organic matter when Ro is 1.0%-1.7% （mainly 1.25%-1.32%）. The natural gas is oil-type gas generated from the source rocks at mature to high mature stage, associated with condensate, so carbon isotopes of the gases are heavier. Natural gas in the Nanpu No.1 structural belt is mainly associated gas with condensate. The analysis of the origin and source of natural gas and condensate, combined with the monomer hydrocarbon carbon isotopes and biomarker, indicated that the main source rocks in the Nanpu No.1 structural belt were Es3 （the lower member of the Shahejie Formation）, followed by Es1 （the upper member of the Shahejie Formation）.？The high-mature hydrocarbons from source rocks in the deep sag mainly migrated through deep inherited faults into shallow traps and accumulated to form oil and gas pools. Therefore, there is a great potential for exploring gas in deep layers.

Dissolution mechanism of a deep-buried sandstone reservoir in a deep water area:A case study from Baiyun Sag,Zhujiang River(Pearl River)Mouth Basin

Dissolution mechanism and favorable reservoir distribution prediction are the key problems restricting oil and gas exploration in deep-buried layers.In this paper,the Enping Formation and Zhuhai Formation in Baiyun Sag of South China Sea was taken as a target.Based on the thin section,scanning electron microscopy,X-ray diffraction,porosity/permeability measurement,and mercury injection,influencing factors of dissolution were examined,and a dissolution model was established.Further,high-quality reservoirs were predicted temporally and spatially.The results show that dissolved pores constituted the main space of the Paleogene sandstone reservoir.Dissolution primarily occurred in the coarse-and medium-grained sandstones in the subaerial and subaqueous distributary channels,while dissolution was limited in fine-grained sandstones and inequigranular sandstones.The main dissolved minerals were feldspar,tuffaceous matrix,and diagenetic cement.Kaolinization of feldspar and illitization of kaolinite are the main dissolution pathways,but they occur at various depths and temperatures with different geothermal gradients.Dissolution is controlled by four factors,in terms of depositional facies,source rock evolution,overpressure,and fault activities,which co-acted at the period of 23.8–13.8 Ma,and resulted into strong dissolution.Additionally,based on these factors,high-quality reservoirs of the Enping and Zhuhai formations are predicted in the northern slope,southwestern step zone,and Liuhua uplift in the Baiyun Sag.

Diagenetic evolution and formation mechanisms of middle to deep clastic reservoirs in the Nanpu sag, Bohai Bay Basin, East China

The reservoir properties, diagenetic features and evolution of the Paleogene Shahejie Formation(Es) in the Nanpu sag, Bohai Bay Basin were analyzed based on mineralogical and petrological data, and the main controlling factors and formation mechanisms of medium to deep high-quality reservoir were revealed by multiple regression analysis. The results show that the sedimentary microfacies, rigid grains content, and dissolution process are the key factors controlling the formation of high-quality clastic reservoir in middle to deep depth in the Nanpu sag. The formation mechanisms of middle to deep sandstones of the Es in different structural belts differ widely in formation mechanism. The Es1(uppermost member of Es) sandstone reservoirs in the Nanpu No.3 structural belt is low porosity, moderate to high permeability reservoir in the mesodiagenesis A2 stage on the whole, and the formation of high-quality reservoirs is mainly attributed to strong compaction resistance ability primarily, and dissolution process secondarily. The Es3(third member of Es) sandstones in Gaoshangpu structural belt is classified as tight sandstones in the mesodiagenesis A1 stage, in which the development of favorable reservoirs is primarily controlled by dissolution. This study provides references for reservoir evaluation of deep clastic reservoirs and exploration deployment in the Bohai Bay rift basin. As there are high-quality reservoirs, it is believed that the deep clastic reservoirs in the eastern of China, such as Bohai Bay Basin still have significant exploration potential.

Petroleum geology controlled by extensive detachment thinning of continental margin crust: A case study of Baiyun sag in the deep-water area of northern South China Sea

The relationships between crustal stretching and thinning,basin structure and petroleum geology in Baiyun deep-water area were analyzed using large area 3D seismic,gravity,magnetic,ocean bottom seismic(OBS),deep-water exploration wells and integrated ocean drilling program(IODP).During the early syn-rifting period,deep-water area was a half-graben controlled by high angle faults influenced by the brittle extension of upper crust.In the mid syn-rifting period,this area was a broad-deep fault depression controlled by detachment faults undergone brittle-ductile deformation and differentiated extension in the crust.In the late syn-rifting period,this area experienced fault-sag transition due to saucer-shaped rheology change dominated by crustal ductile deformation.A broad-deep fault depression controlled by the large detachment faults penetrating through the crust is an important feature of deep-water basin.The study suggests that the broad-deep Baiyun sag provides great accommodation space for the development of massive deltaic-lacustrine deposition system and hydrocarbon source rocks.The differentiated lithospheric thinning also resulted in the different thermal subsidence during post-rifting period,and then controlled the development of continental shelf break and deep-water reservoir sedimentary environment.The high heat flow background caused by the strong thinning of lithosphere and the rise of mantle source resulted in particularities in the reservoir diagenesis,hydrocarbon generation process and accumulation of deep-water area in northern South China Sea.

Formation mechanisms and distribution of high quality reservoirs in deep strata in Palaeogene in northern steep slope zone of Bonan sag, Jiyang depression, China

Petrographic analysis combined with various techniques, such as thin section identification, petro-physical property testing, mercury penetration, oil testing results, was used to assess basic reservoir characteristics of deep strata in Palaeogene in the northern steep slope zone of the Bonan sag, China. The formation mechanisms of high quality reservoirs in deep strata were discussed according to evolution characteristics of paleopressures and paleofluids in geological period. The deep reservoirs have poor physical properties and mainly develop extra-low porosity, extra-low and ultra-low permeability reservoirs. Reservoir spaces mainly consist of secondary pores and overpressure fractures. Early overpressure, early hydrocarbon filling and dissolution by early organic acids are the major formation mechanisms of high quality reservoirs. The conglomerate in inner fan which had a poor primary physical property mainly experienced strong compaction and calcareous matrix recrystallization. The physical properties of the inner fan were poor with weak dissolution because of poor mobility of fluid. The reservoirs mainly are type IV reservoirs and the distribution extends with the burial depth. The braided channel reservoirs in the middle fan had relative good primary physical properties and strong ability to resist compaction which favored the preservation of primary pores. Large amounts of the secondary porosities were created due to dissolution by early organic acids. A series of micro-fractures generated by early overpressures would be important migration pathways for hydrocarbon and organic acids. Furthermore, early overpressures had retarded maturation of organic matters and organic acids which had flowed into reservoirs already and could keep in acid environment for a long time. This process would contribute significantly to reinforcing the dissolution and enhancing the reservoir quality. The braided channel reservoirs were charged with high oil saturation preferentially by early hydrocarbon filling which could inhibit later cementation. Therefore, the braided channel reservoirs develop a great quantity of reservoir spaces with type I, type II and type III reservoirs in the majority in the deep strata. With the burial depth, distributions of type I and type II reservoirs are narrowed and distribution of type III reservoirs decreases first and then extends. The reservoirs both in outer fan and in interdistributary of the middle fan have extremely poor physical properties because of extensive carbonate cementation. The type of the reservoirs mainly is type IV.

Diagenetic evolution and its effect on reservoir-quality of fan delta sandstones during progressive burial: Evidence from the upper part of the fourth member of Shahejie formation, Bonan sag, Jiyang depression

Petrographic analysis combined with various techniques, such as thin section identification, fluid inclusions, isotopic data, petro-physical property testing and oil testing results, was used to study diagenetic evolution and its effect on reservoir-quality of fan delta reservoirs of Es4s in the Bonan sag. The diagenesis is principally characterized by strong compaction, undercompaction, multi-phase of dissolution and cementation. Compaction played a more important role than cementation in destroying the primary porosity of the sandstones. The reservoirs have experienced complicated diagenetic environment evolution of "weak alkalineacid-alkalinity-acid-weak alkalinity" and two-stage of hydrocarbon filling. The diagenetic sequences are summarized as "early compaction/early pyrite/gypsum/calcite/dolomite cementation→feldspar dissolution/the first stage of quartz overgrowth → early hydrocarbon filling→quartz dissolution/anhydrite/Fe-carbonate cementation→Fe-carbonate dissolution/feldspar dissolution/ the second stage of quartz overgrowth→later hydrocarbon filling→later pyrite cementation. In the same diagenetic context, the diagenetic evolution processes that occurred in different sub/micro-facies during progressive burial have resulted in heterogeneous reservoir properties and oiliness. The braided channel reservoirs in fan delta plain are poorly sorted with high matrix contents. The physical properties decrease continually due to the principally strong compaction and weak dissolution. The present properties of braided channel reservoirs are extremely poor, which is evidenced by few oil layers developed in relatively shallow strata while dry layers entirely in deep. The reservoirs both in the underwater distributary channels and mouth bars are well sorted and have a strong ability to resist compaction. Abundant pores are developed in medium-deep strata because of modifications by two-stage of acidic dissolution and hydrocarbon filling. The present properties are relatively well both in the underwater distributary channels and mouth bars and plenty of oil layers are developed in different burial depth. The present reservoir properties both in interdistributary channel and pre-fan delta are poor caused by extensively cementation. Small amounts of oil layers, oil-water layers and oil-bearing layers are developed in relatively shallow strata while dry layers totally in deep.

Comparison of different spectral decompositions for non-marine deep water sandstone reservoir prediction in the Xingma area

It is difficult to identify and predict non-marine deep water sandstone reservoir facies and thickness,using routine seismic analyses in the Xingma area of the western Liaohe sag,due to low dominant frequencies,low signal-to-noise ratios,rapid lateral changes and high frequencies of layered inter-bedding.Targeting this problem,four types of frequency spectral decomposition techniques were tested for reservoir prediction.Among these,the non-orthogonal Gabor-Morlet wavelet frequency decomposition method proved to be the best,was implemented directly in our frequency analysis and proved to be adaptable to non-stationary signals as well.The method can overcome the limitations of regular spectral decomposition techniques and highlights local features of reservoir signals.The results are found to be in good agreement with well data.Using this method and a 3-D visualization technology, the distribution of non-marine deep water sandstone reservoirs can be precisely predicted.

珠江口盆地开平南大型深水深层油田发现与认识创新

开平凹陷是珠江口盆地地质条件最复杂的凹陷之一,也是重要的深水油气勘探区,由于洼陷结构、烃源分布及成藏规律认识不清,长期制约勘探进程。基于三维地震资料精细解释,开展成盆机制、烃源发育、源汇体系及成藏主控因素等研究,近期在开平南获得了大型轻质油田勘探发现。为进一步指导勘探,分析了开平凹陷油气成藏条件,总结了油气成藏模式。结果表明:(1)开平凹陷是南海北部强伸展陆缘背景下发育的“拆离-核杂岩”型凹陷,裂陷期经历“断陷—拆离—断拗”3幕演化过程;(2)开平凹陷发育文昌组优质湖相烃源岩,分布范围广、生烃潜力大,总体处于成熟至高成熟阶段;(3)开平凹陷油气运移受“源-断-脊”耦合控制,开平凹陷南部3大鼻状构造带是油气有利汇聚区,总体具有“近源强势充注-断脊差异运聚-晚期快速成藏”的模式。开平南古近系大型轻质油田的发现实现了开平凹陷勘探重大突破,开辟了珠江口盆地深水区油气勘探的新区、新领域,同时为“拆离-核杂岩”型含油气盆地的勘探提供了借鉴。

准噶尔盆地沙湾凹陷二叠系上乌尔禾组流体相态及油气藏类型

准噶尔盆地腹部地区沙湾凹陷超深层蕴含丰富的油气资源。根据烃源岩热演化模拟实验分析了沙湾凹陷二叠系上乌尔禾组烃源岩生烃产物类型,结合地层流体高温高压物性实验数据,运用相图判别法和经验参数法对沙湾凹陷征10井地层流体相态进行深入研究。研究结果表明:①沙湾凹陷征10井上乌尔禾组油气主要来自于下乌尔禾组泥质烃源岩,其有机质类型为Ⅱ1型,镜质体反射率(Ro)为1.05%~1.46%,岩石热解峰温(T_(max))为433~446℃,处于成熟—高成熟演化阶段,目前处于生轻质油阶段。②上乌尔禾组地层流体成分表现为凝析气藏的流体组成,地层温度为166.0℃,介于临界温度和临界凝析温度之间,地层压力为155MPa,远高于露点压力,地-露压差大,表明地层条件下流体呈凝析气相特征,但地下油气相态与地表采出流体相态具有一定差异。相图判别法和经验参数法烃类流体相态分析结果均显示,征10井上乌尔禾组气藏为含大油环的凝析气藏。③沙湾凹陷上乌尔禾组具有优越的成藏条件,紧邻下乌尔禾组烃源岩,油气近源垂向输导,向局部隆起区运聚,巨厚的三叠系及上乌尔禾组中上部区域盖层起到重要的封盖作用,最终在局部隆起区形成岩性-构造凝析气藏。

珠江口盆地白云凹陷古近系深层高变温背景下储层成岩作用与低渗致密化机制

珠江口盆地白云凹陷油气勘探逐渐从中-浅层韩江组-珠江组的常规储层转向深层-超深层珠海组-恩平组的低渗致密储层,特殊的高变地温地质背景使得储层成岩作用以及致密化机制与常规储层差别较大。综合运用铸体薄片鉴定、扫描电镜观察、物性测试、成岩过程重建和物性恢复等技术,系统分析了白云凹陷西北部低隆起-中部洼陷带古近系珠海组下段-恩平组砂岩储层的成岩过程及差异,结合构造演化背景、地层埋藏史和现今物性数据,研究了影响储层物性关系的主要因素以及储层致密化过程与机理。结果表明:珠海组下段-恩平组储层经历了较强的压实作用、2期碳酸盐胶结、3期硅质胶结和3期长石溶解作用。储层成岩作用过程中,地温梯度变化导致压实速率不同,经历不同开放-封闭体系的水-岩反应过程是不同区带物性差异的主要原因。压实作用是导致储层致密的主要因素,硅质胶结和碳酸盐胶结进一步增强了储层致密程度,溶解作用改善了储层物性。从低隆起到洼陷带,伴随地温梯度升高和埋藏深度增加,低隆起储层成岩阶段为中成岩A2期,斜坡带为中成岩B期,洼陷带为晚成岩期,成岩强度不断增加;成岩作用的差异使得储层物性演化显著不同。洼陷带储层在晚期烃类充注前已致密化,斜坡带储层在晚期烃类充注阶段逐渐致密,而低隆起区储层目前仍为低渗储层。斜坡带整体埋深小于5 km,且上覆地层具备良好封盖能力,是下部勘探的重点。

准噶尔盆地盆1井西凹陷石炭系火山岩凝析气藏的发现与勘探启示

准噶尔盆地石炭系火山岩油气藏是油气勘探的重点领域之一。根据录测井资料、地球化学分析数据及岩石薄片鉴定资料,结合地球物理方法,厘清了准噶尔盆地盆1井西凹陷石炭系火山岩油气成藏的主控因素,总结出深层火山岩气藏富集规律,明确了有利勘探方向。研究结果表明:(1)准噶尔盆地盆1井西凹陷风城组烃源岩厚度为100~300 m,面积约为5 400 km2,整体进入生凝析油—干气阶段,生气强度大于20×108m3/km2,为凹陷提供了丰富的天然气源。(2)研究区石炭系火山岩岩性复杂,爆发作用形成的安山质火山角砾岩受到风化淋滤作用,可形成物性较好的风化壳型储层。石炭系—二叠系大型不整合面和广泛发育的深大断裂是重要的输导体系,二叠系上乌尔禾组泥岩作为区域盖层,为凝析气成藏提供了保存条件,油藏主要分布在高部位,气藏分布于低部位。(3)通过“两宽一高”(宽方位、宽频带、高密度)技术,提高地震成像精度,联合时-频电磁技术(TFEM),实现了石炭系火山岩的精细刻画,为深层油气藏的勘探提供了有力支撑。石西16井的重大突破,证实了盆1井西凹陷石炭系火山岩具有巨大的勘探潜力。

准噶尔盆地南缘四棵树凹陷超深层构造演化与油气成藏过程

准噶尔盆地南缘下组合近年取得了重要勘探突破,随着勘探持续深化,在工业油气流圈闭附近的构造却钻探失利,下组合区域差异较大,成藏过程复杂。通过对高泉地区构造进行平衡地质剖面恢复,结合流体包裹体、埋藏史、热史和油气运聚数值模拟研究,揭示了高泉地区下组合的构造演化与成藏过程,并分析了部分井失利的原因。结果表明,高泉构造在前侏罗纪已经存在,为一宽缓古隆起,新生代早期受喜马拉雅造山运动影响,分割为若干断块构造,分割后的圈闭成藏过程具有差异性。高泉构造总体经历了3期油气充注和晚期的调整改造:第一期为中新统塔西河组沉积时期(约16 Ma)的低熟原油充注,对应包裹体荧光为黄色;第二期为独山子组沉积中期的成熟原油充注(约7 Ma),对应的是石英颗粒愈合缝内蓝色、蓝白色荧光油包裹体;第三期为上新世(约3 Ma)以来的天然气充注,天然气来源主要为四棵树凹陷,高泉地区本地烃源岩主体并未进入生气阶段。四棵树凹陷近端和远端圈闭成藏潜力和勘探远景具有较大差别,凹陷周边圈闭晚期多经历改造和调整,近端圈闭具有距离油源近、供烃充足等优势,应作为优先勘探目标,远端圈闭改造后油气源补充不足,具有较大勘探风险。

吐哈盆地台北凹陷中侏罗统西山窑组深层煤岩气地质特征与勘探潜力

深层煤岩气是吐哈盆地油气勘探的新领域,但研究程度相对较低。基于煤岩测试与基础资料,系统研究了吐哈盆地台北凹陷中侏罗统西山窑组煤层分布、煤岩煤质、储层物性、宏微观煤岩、煤储层气源及煤岩等温吸附特征,揭示了煤岩储层含气性及其影响因素,提出了深层煤岩气形成富集条件,建立了深层煤岩气富集成藏模式,预测了台北凹陷煤岩气勘探潜力。结果表明:(1)台北凹陷深层侏罗系西山窑组煤层分布广、厚度大,为中低阶、原生结构、割理发育的低灰、低水、富镜质组煤层;(2)煤储层孔渗较高且受埋深影响不明显,煤层段气测异常普遍且储层吸附性能中等—好,具有游离气与吸附气共存、试采快速见气、气组分齐全等特征;(3)台北凹陷煤岩气的油气供给充注,可以形成正向构造带“调整型”和斜坡及洼陷区“自生自储型”两种成藏模式;(4)台北凹陷煤岩气资源丰富,西山窑组主煤层煤岩气资源量近3×10^(12)m^(3)。根据煤岩气资源丰度、煤层厚度、含气量、保存条件等综合评价优选出温吉桑构造带、小草湖南斜坡为深层煤岩气勘探有利目标区。

白云南洼珠海组陆架坡折带演化特征与深水沉积耦合关系

白云南洼珠海组沉积时期,盆地处于断陷向拗陷转化阶段,陆架坡折形态以及位置发生巨大变化,导致深水沉积的类型和特征具有明显差异。针对这种坡折演化对深水沉积类型的影响开展研究,通过对白云南洼珠海组三维地震剖面进行解译,识别珠海组各层段陆架坡折带,定量分析坡折特征及其演化规律,探讨坡折演化过程与深水沉积的耦合关系。研究结果表明,通过对珠海组沉积时期陆架坡折带定量分析,将其迁移演化类型划分为下降型、平直型、低角度上升型、高角度上升型4类;在井震结合的基础上,根据地震相组合以及沉积体系分布特点,识别出斜坡扇、块状搬运沉积、深水水道体、盆底扇4种主要的深水沉积类型;并发现陆架坡折演化类型与深水沉积类型存在明显的耦合关系:平直型、高角度上升型、低角度上升型和下降型陆架边缘迁移轨迹分别对应斜坡扇、块状搬运沉积、深水水道体和盆底扇的优势发育。此外,珠海组四段至珠海组三段陆架坡折带整体由下降型向低角度上升型转变,深水沉积体系以斜坡扇及深水水道体发育为主;珠海组三段至珠海组一段早期整体由低角度上升型向下降型转变,深水沉积体系以深水水道-盆底扇沉积体系为主;珠海组一段晚期整体由下降型向高角度上升型演化,深水沉积体系几乎不发育。本研究揭示了陆架坡折迁移对深水沉积体系类型和分布的控制作用,对深入理解深水沉积过程和油气勘探具有重要意义。

准噶尔盆地盆1井西凹陷及周缘深层二叠系超压形成机制及演化特征

为明确准噶尔盆地盆1井西凹陷及周缘深层二叠系超压形成机制及演化特征,基于钻井、测井、实测地层压力等资料,运用测井曲线组合分析法和交会图版法以及盆地模拟技术,对超压成因机制及演化特征进行分析,并定量表征目的层不同成因类型超压的贡献率。结果表明:①研究区深层二叠系不同岩性地层超压成因具有明显差异,其中风城组和下乌尔禾组烃源岩层超压成因主要为生烃和欠压实作用,其中生烃作用占主导;泥岩盖层超压成因主要为欠压实作用;而风城组和下乌尔禾组储层超压成因主要为超压传递和欠压实作用。②研究区风城组烃源岩生烃增压自早二叠世开始,现今达到最大,不同构造部位增压大小差别较小,烃源岩层超压主要分布于39.43~49.16MPa,但其贡献率具有明显差异,凸起区较大,而凹陷区较小;凸起区和凹陷区生烃增压对总超压贡献率分别为84.49%~94.41%和65%~67.3%,研究区下乌尔禾组烃源岩生烃增压大小与风城组具有相似的规律;欠压实作用对泥岩盖层超压的贡献率一般为100%。③研究区二叠系储层超压传递增压主要形成于晚侏罗世至早白垩世以及古近纪至今,其贡献率在不同凸起区存在明显差异,达巴松凸起和石西凸起分别为21.86%~23.35%和100%。厘清研究区深层、超深层超压的分布规律,可以为盆地新区的进一步开发提供依据。

准噶尔盆地沙湾凹陷三叠系超深层碎屑岩储层特征及主控因素——以征10井区克拉玛依组为例

超深层碎屑岩储层由于埋藏深度大,储层物性一般较差,单井油气产能低,但中国石化探区沙湾凹陷近期钻探的征10井却在埋深6700m的三叠系克拉玛依组钻遇了优质厚层储层,常规测试即获得高产工业油气流。为了揭示该套储层的特征及有利储层主控因素,明确该地区超深层碎屑岩勘探方向,降低该区下步油气勘探的风险,通过岩心、测井、铸体薄片、物性、扫描电镜等资料综合分析,并结合储层成岩演化,探讨了该区三叠系克拉玛依组储层岩石学特征、物性特征、孔隙特征及有利储层主控因素。研究结果表明:征10井区三叠系克拉玛依组超深层碎屑岩为辫状河三角洲前缘沉积,岩性以砂砾岩、含砾细砂岩及细砂岩为主,岩石类型主要为长石岩屑砂岩,成分成熟度较低;储集空间类型以剩余原生孔隙与溶蚀孔隙为主,储层平均孔隙度为9.1%,平均渗透率为2.85mD,整体属于特低孔特低渗透及低孔低渗透储层。有利沉积相带、建设性成岩作用及异常高压共同控制了该区有利储层的发育及分布。其中,沉积微相是有利储层发育的基础,辫状河三角洲前缘水下分流河道中沉积的细砂岩分选及磨圆较好,泥质杂基含量低,储层物性较好,是有利储层发育的优势相带;早期成岩过程中产生的钠长石胶结物后期被酸性溶蚀使得溶蚀孔隙增加,是重要的建设性成岩作用;油气持续充注所形成的异常高压,形成时间早且长期持续发育,起到了重要的建设作用。研究成果对该地区下步超深层油气勘探具有指导作用。

断陷湖盆陡坡带早期斜向扇三角洲形成机制、发育规律及勘探启示:以东营凹陷北带为例

断陷湖盆作为全球最重要的含油气盆地类型之一,在盆地早期的充填演化过程中,其陡坡带往往能够形成厚达上千米的砂砾岩沉积建造,成为油气勘探的重要领域。目前对这些巨厚层砂砾岩的沉积成因认识仍存在较多的争议。本次研究以济阳坳陷典型的断陷湖盆——东营凹陷陡坡带盐家地区为例,基于高分辨率三维地震数据体、岩心、录井、测井等地质资料,综合运用地震地层学、构造地质学、沉积学和流变学分析方法,对前期在断陷湖盆陡坡带早期发现的斜向扇三角洲的发育特征及其形成演化机制进行了研究,取得了以下主要认识:(1)斜向扇三角洲沉积物中砾石含量相对较高,由牵引流和重力流共同形成,石英含量平均40%~55%,发育扇三角洲平原、扇三角洲前缘和前扇三角洲亚相,其地震响应特征在顺物源方向表现为(斜交、叠瓦和帚状)前积相,在垂直物源方向表现为充填相;(2)斜向扇三角洲主要发育于断陷早期,并于断陷中期大量消亡,扇体与边界断层以低角度斜交,角度通常不会超过45°,扇体的发育规模受到其根部所处位置的影响,扇体的消亡呈非等时性;(3)断陷湖盆陡坡带早期大型斜向扇三角洲的形成演化主要受控于4个因素:边界断层分段特征形成的转换构造为斜向扇三角洲的发育提供输送通道,断陷早期边界断层控制下的古凹槽为斜向扇三角洲的发育提供可容纳空间,断块间相互作用形成的破碎带为斜向扇三角洲的发育提供物质来源以及边界断层的硬连接导致斜向扇三角洲的消亡并向近岸水下扇转换;(4)已发现断陷湖盆陡坡带深层砂砾岩油气藏多属于斜向扇三角洲。本次研究指出陡坡带各级别转换带可作为勘探的重点靶区,布井方向应沿斜交边界断层。本研究不仅丰富了断陷湖盆陡坡带沉积理论,同时能够为中国陆相断陷盆地深层勘探提供新的思路和理论依据。

辽河盆地西部凹陷中深层超压体系成因机制研究

辽河盆地西部凹陷中深层发育明显超压,明确其超压的分布和形成机制对该地区中深层油气勘探具有重要意义。基于实测地层压力、测井曲线组合、超压成因判识图版及盆地模拟等方法,针对西部凹陷中深层超压发育特征、成因机制及超压对成藏的控制作用进行了研究。结果表明,西部凹陷整体发育超压型、常压型、低压型3类温压系统,超压主要发育在2500~4000 m的中深层,超压成因以欠压实作用为主。在中段冷家—雷家地区沙三段地层超压除欠压实作用贡献外,局部伴有生烃增压、成岩作用和构造挤压的混合贡献,北段因遭受过强烈的抬升剥蚀作用,表现为异常低压为主。采用盆地模拟手段对超压成因贡献量进行评价,其压力演化存在3期:第1期以构造沉降作用导致的欠压实作用为主;第2期由于地层抬升泄压,欠压实和流体膨胀作用经历短暂停止;第3期烃源岩到达生烃高峰,生烃增压作用逐渐增强且流体膨胀增压可达5 MPa。

渤中凹陷深层高压井地质工程一体化技术研究与应用

渤海湾盆地渤中凹陷深层潜山地质条件复杂,目的层埋藏深,钻遇地层层位多,岩性复杂多变,地层压力系统变化大,钻井过程中复杂情况频发,薄弱层易漏失,影响勘探开发进程。为此,研究了钻前井漏风险预测及地层压力校正,钻中高压段中完科学决策、潜山界面精确卡取和潜山地层压力随钻识别与控制等方面的技术,实现了钻井设计及随钻调整方案优化,形成了渤中凹陷深层高压井全过程地质工程一体化技术。渤海油田20口深层高压探井应用全过程地质工程一体化技术后,钻井复杂情况降低了60%,井漏、溢流等复杂情况处理时间缩短了40%,潜山界面识别准确率100%,单井钻井成本降低3000万元以上。全过程地质工程一体化技术为渤海油田深层超深层勘探开发提供了技术途径,具有较好的应用前景。

东海盆地西湖凹陷平湖斜坡始新统平湖组成岩相类型及对储层的控制

为了在深埋藏、强非均质性背景下寻找相对优质储层,本文以东海盆地西湖凹陷平湖组为例,基于直观微区观测、间接压汞表征及孔渗分析相结合的方法,在储层沉积学分析的基础上,先划分成岩相类型,进而明确不同成岩相的差异储集能力特征,评价成岩相储集能力。结果表明:平湖组沉积于河流和潮汐双向水动力条件的三角洲-潮坪体系,砂体多发育于水下分流河道、河口坝、潮道、砂坪和混合坪中,以细粒和极细粒为主,主要为长石岩屑砂岩和岩屑长石砂岩;基于成岩作用类型的强度差异将成岩相划分为3类,包括长石溶蚀相、富塑性压实相和钙质胶结相;同一成岩相类型孔渗特征和孔隙结构特征均一,而不同成岩相之间物性差异显著;以孔隙度、渗透率、最大连通孔喉半径为标准对3类成岩相进行量化参数分级评价,长石溶蚀相孔隙度>15%,渗透率>10.0×10^(-3)μm^(2),最大连通孔喉半径>5.0μm,物性条件优于富塑性压实相和钙质胶结相,优选出长石溶蚀相为最有利的储层砂体类型。