Sequence Thickness and its Response to Episodic Tectonic Evolution in Paleogene Qikou Sag, Bohaiwan Basin

The sequence stratigraphy framework of Paleogene of Qikou Sag has been built in this paper. The evolution law of episodic subsidence in Qikou Sag has been expounded, with the analysis of the characteristic of sequence thickness, as well as the study of consedimental tectonic activity, subsidence history, paleogeomorphology and the coupling relationship among them. The faults controlling action was the dominant mechanism during rifting stage I , as the depression was the dominant mechanism during rifting stage III, which embodies a process from intense disparity fault depression to integral subsidence. Meanwhile, under the control of regional faulting and later stage depression, subsidence rate centers and paleogeomorphic concave centers are always corresponding to the sequence thickness centers, and the changes of subsidence centers and paleogeomorphology concave centers are consistent with the migration of thickness centers, which presents the restriction, coupling and response among them and clarifies the law that tectonic activity controls the basin fill by means of controlling the subsidence rate and paleogeomorphology from contributing factor angle. On this basis, the dynamic evolution of the composite pattern of structure-subsidence-deposition in the fault controlling actic region during the three rifting stages and their petroleum geological significance has been discussed.

Paleogeomorphy,provenance system and sedimentary system of the Dongying formation in the Qikou sag

Reconstructed synsedimentary paleogeomorpholgy is an effective method in predicting the distribution of sandbodies and can provide valid evidence in the search for reservoirs. Based on a synsedimentary paleogeomorpholgy reconstruction of the third member of the Dongying formation (Ed3) in the Qikou sag,the basic paleogeomorphic characteristics of Ed3 are described and the spatial distributions of denudation and subsidence areas are discussed. Key boundary faults controlling the deposition of important sediment bodies are proposed and the interrelations among faulted slope-break belts or flexure belts,intra-depression uplifts and sags,sediment sources and sediments input points have been investigated.

Recognition and depiction of special geologic bodies of Member 3 of Dongying Formation in Littoral Slope Zone,Qikou Sag

The purpose of this study is to forecast the profitable oil and gas reservoir,which is the key of finding hydrocarbon,based on the conception of special geologic bodies.With the guiding methodology of the research thinking of integration of point-line-surface by using the methods and techniques of logging,seismic,seismic attribute,and logging constrained inversion in 3D data volume,the special geologic bodies of Member 3 of Dongying Formation in Littoral Slope Zone of Qikou Sag,which has important hydrocarbon exploration potential,are recognized and described under the constraint of sequence stratigraphic framework.As a result,the developed scale,geometric shape and space distribution feature of the special geologic bodies are forecasted;the inner structure and sequence structure patterns of the geologic bodies are also ascertained.From the lowstand system tract (LST) and lacustrine expanding system tract (EST) to the highstand system tract (HST),the geologic bodies have evolved from relative centralization of lake basin reducing period to three relative dispersive isolated parts of broad lake basin period.According to the relevance and regularity of the development of geologic bodies,the conclusions can be obtained that three types of potential profitable reservoir traps,including the lithologic lens traps,lithologic updip pinchout traps and structural-lithologic composite traps,are forecasted.In addition,scientific basis for further hydrocarbon exploration in new area (few-well area and no-well area) is offered in the guidance of sequence stratigraphic model.

Main Controlling Factors and Dominant Reservoir Series Analysis of Es_3 in the Qibei Area of Qikou Sag

Based on analysis of geophysical data such as core observation, rock slices identification, physical property, scanning electron microscope, X-ray diffraction, logging data etc., 16 factors of sedimentation, diagenesis, fluid pressure, and their relationships with reservoir physical property were analyzed, and the results indicate sedimentation is the internal factor controlling the reservoir property, diagenesis is the external and final decisive factor and abnormal fluid pressure is an important factor preserving the deep reservoir property. Quantitative characterization of diagenesis indicates that compaction and dissolution are more important than cementation and they respectively cause porosity change of-23.6% and 7.7% and -6.2%. Through optimizing 11 main controlling factors and constructing reservoir evaluation index （REI） according to the hierarchical cluster and principal component analysis, reservoir classification standard was established and reservoirs were divided into four classes. The studies show that Es~ SQ4 consists mainly of class I and II, while Es~ SQ6 is mainly of class III and II; the favorable zone is the north and south slope of Qibei sub-sag and the Liujianfang fault-nose. The successful application of the quantitative and comprehensive evaluation in the Qibei area verifies the advanced, practicable method of less artificial factor is suitable for the low porosity and permeability reservoir.

Comprehensive evaluation on hydrocarbon-bearing availability of fault traps in a rift basin: A case study of the Qikou sag in the Bohai Bay Basin, China

An evaluation system of hydrocarbon-bearing availability of fault traps was established based on the comprehensive analysis of fault segment growth history,fine reservoir anatomy and geochemistry tracing,with the Qikou sag in the Bohai Bay Basin as target area.The displacement/separation transform and displacement gradient method were used to prove the interpretation reliability of fault traps.The method of maximum throw subtraction was used to recover the history of fault growth and determine the availability of the forming period of fault traps.Based on the quantitative relationship between shale gouge ratio and cross-fault pressure difference of known reservoirs in southern Qikou sag,the critical shale gouge ratio of fault lateral sealing was calculated at 20%,and the quantitative evaluation chart based on the relationship of"fault throw–sand-formation ratio and hydrocarbon column height"was constructed.Based on the results of reservoir fine anatomy and quantitative fluorescence tracing test shale smear factor method is suitable for evaluating the vertical sealing of faults in the caprock of the middle submember of first member of Paleogene Shahejie Formation,and the shale smear factor critical value is 3.5.The juxtaposition thickness method is suitable for evaluating vertical sealing of faults in the caprock of the second member of Paleogene Dongying Formation,and the critical juxtaposition thickness of fault is 70–80 m.By combining four factors,the availability of fault trap interpretation,the availability of the forming period of fault trap,the availability of fault lateral sealing and the availability of fault vertical sealing,the comprehensive evaluation chart on hydrocarbon-bearing availability of fault traps in Qikou sag has been established,which provides a reasonable basis for risk assessment of fault traps.

Fault-sand combination modes and hydrocarbon accumulation in Binhai fault nose of Qikou Sag, Bohai Bay Basin, East China

Based on seismic and logging data,taking the downthrow fault nose of Binhai fault in Qikou Sag as the object of study,we analyzed fault characteristics,sand body distribution,fault-sand combinations and hydrocarbon accumulation to reveal the hydrocarbon enrichment law in the fault-rich area of fault depression lake basin.The results show that the Binhai Cenozoic fault nose is characterized by east-west zoning,the main part of the western fault segment is simple in structure,whereas the broom-shaped faults in the eastern segment are complex in structure,including several groups of faults.The difference of fault evolution controls the spatial distribution of sand bodies.The sand bodies are in continuous large pieces in the downthrow fault trough belt along the Gangdong Fault in the middle segment of the fault nose,forming consequent fault-sand combination;whereas the fault activity period of the eastern part of the fault nose was later,and the sand bodies controlled by paleogeomorphology are distributed in multi-phase north-south finger-shaped pattern,forming vertical fault-sand combination pattern matching with the fault.The configuration between faults and sand bodies,and oil sources and caprocks determine the vertical conductivity,plane distribution and vertical distribution of oil and gas.Two oil and gas accumulation modes,i.e.single main fault hydrocarbon supply-fault sand consequent matching-oil accumulation in multi-layers stereoscopically and fault system transportation-fault sand vertical matching-oil accumulation in banded overlapping layers occur in the middle and eastern segments of the fault nose respectively,and they control the difference of oil and gas distribution and enrichment degree in the Binhai fault nose.

Recognition and Depiction of the Special Geologic Bodies of the Member 3 of Dongying Formation in Littoral Slope Zone,Qikou Sag

The key of finding hydrocarbon reservoir is to find the profitable oil and gas reservoir.This paper uses the conception of"special geologic bodies"to study the profitable reservoir.Constrained by the sequence stratigraphy framework,this paper recognizes and describes the special geologic bodies of the Member 3 of Dongying Formation in Littoral Slope Zone of Qikou Sag,which have important

Genetic Types and Exploration Significance of Slope Break Belt in Paleogene in Qikou Sag,Huanghua Depression,Bohai Bay Basin,Eastern China

Enrichment of hydrocarbon reservoir relates to the slope break types in continental basin(sag)in China. Division and analysis of genetic types of slope break will help to study the enrichment regularity of hydrocarbon reservoir and is conducive to the guiding of future development in exploration and enhancing prediction accuracy.This paper,guided by the theory of sequence stratigraphy and using high-resolution three-dimensional seismic data,drilling and other information,takes into account the characteristics

Characteristics of Sediment Supply and Sediment Dispersal in Binhai District of Qikou Sag,Central Huanghua Depression

The Qikou sag is the largest hydrocarbon-rich sag in the central Huanghua depression of Bohaiwan basin.It formed as a result of Tertiary rifting and was mainly filled with Cenozoic siliciclastic sediments about 8000-10000 m thick.The petroleum exploration of Binhai district in Qikou sag hardly gained breakthrough all through because of previous ambiguous understanding of spatial and temporal patterns

Architecture of Sandstone Bodies of Paleogene Shahejie Formation in Northern Qikou Sag, Northeast China

The conception of special geologic bodies has been applied in this study to define and illustrate economic oil and gas reservoirs in sandbodies, which is helpful for hydrocarbon forecast and exploration. Using the comprehensive analysis of drilling, logging, seismic, seismic attribute extraction, and logging constrained inversion in 3D data volume, the special geologic bodies of the Shahejie Formation（Ps^1s） in northern Qikou sag, which have good hydrocarbon potential, are identified and described under the constraint of sequence stratigraphic framework. The dimensions, geometry, and spatial distribution features of the special geologic bodies, as well as their inner architectures and sequence-structure patterns, are also ascertained. The geologic bodies evolved from relative centralization in the middle part of the lacustrine basin in the early stage of Ps1~s Formation, to several dispersive isolated parts in the later stage. This shows a small cycle interval（~2.5 Ma） at the end of the whole transgressive depositional process of Ps1（~7.5 Ma） during the expansion of the lake and relative lake level rise, with the control of sediments supply and fault-related subsidence, which effect the evolution of the sedimentary system. According to the relevance and regularity of the geologic bodies＇ development, different types of potential profitable reservoir traps, including the lithologic lenticular traps, lithologic updip pinchout traps, and structural-lithologic composite traps, can be preserved in the study area. In addition, the internal architecture models provide scientific basis for further hydrocarbon exploration in the frontier basin without enough data.

Cenozoic Fault Distribution Characteristics and Evolution in Qikou Sag of Bohai Basin, China

Qikou sag, located in north-center of Huanghua depression in Bohai Basin, is a Cenozoic sag with rich hydrocarbon. As a microcosm of Bohai Basin, the fault characteristics of Cenozoic structural layers in Qikou sag could indicate and record the evolution of Cenozoic stress field in Bohai Basin. Based on the latest 3-D seismic data, the study takes statistics on the fault system of Cenozoic structural layers and analyzes the fault throws of major large faults along the strikes in different periods in Qikou sag, then the fault distribution regularities and the fault direction characteristics in each structural layer are summarized. The result shows that during Cenozoic, the fault activity strength migrates from southwest to northeast and the strikes of faults changes from northwestward in Sha-3 period to nearly east-westward since Sha-1 period.

Characteristics and origin of high-quality lacustrine carbonate reservoirs in the gentle slope area of the Qikou Sag, Bohai Bay Basin

Lacustrine carbonate reservoirs in the gentle slope(ramp)area of Qikou Sag are highly heterogeneous.Some researches about characteristics and distribution of these high quality reservoirs are less.In this study,an integrated investigation was conducted on the high-quality lacustrine carbonate reservoirs in the ramp area of Qikou Sag based on data of thin section examination,lithological log response,testing results,and mercury-injection capillary pressure measurement.In the study area,grainstone reservoirs in the lower 1st member of the Shahejie Formation are high-quality reservoirs characterized by high-medium porosity,moderate permeability,low displacement pressure,and relative large pore throat.Lithologically,these reservoirs are mainly composed of bioclastic and oolitic sparite,and reservoir storage space consists of secondary intergranular dissolved pores and fractures.Hydrodynamic conditions generally control distribution of these reservoirs,as limestone grains filled intergranularly with sparry calcite cement are usually formed under strong hydrodynamic conditions.Sparry calcite cemented limestone is subject to late dissolution with abundant soluble substances,which is one of the direct causes for the well developed secondary dissolved pores.Oolitic bank and bioclastic bank are under high-energy hydrodynamic conditions with the best reservoir petrophysical properties.Rims of beach bars are usually in an intermittently-turbulent highly-hydrodynamic environment with medium reservoir petrophysical properties.Lake bays and supratidal zones are under low-energy tranquil hydrodynamic conditions,with poor reservoir petrophysical properties.During late diagenesis,large quantities of organic acid and slightly acidic water were released from surrounding shale and migrated along the top unconformity of the 3rd member of the Shahejie Formation,resulting in development of numerous secondary dissolved pores in carbonate reservoirs,which is the main cause of high-quality reservoir formation in the sag.Additionally,early charge of hydrocarbons restrained occurrence of authigenic minerals and metasomatism of calcite,and thus promoted excellent preservation of dissolved pores.

歧口凹陷区新近系馆陶组热储特征及成因机制

渤海湾盆地黄骅坳陷歧口凹陷内赋存极为丰富的地热资源,其中新近系馆陶组热储最具开采价值,开展馆陶组热储地温场、孔渗条件、地热水循环规律和成因模式研究对认识馆陶组地热资源属性,合理开发地热资源具有重要意义。通过分析该区钻探、物探、测温、开发数据等资料,确定歧口凹陷内馆陶组热储为沉积盆地传导型地热系统,深部地幔热流和地壳内放射性生热以热传导方式传热,地热异常分布受基岩起伏的控制,在沧东断裂、滨海断裂附近出现高温地热异常,地温梯度可达5.0℃/hm以上。馆陶组热储的孔渗条件南北两侧较高、中部较低,热储孔隙率整体在26%以上,渗透率在390×10^(-3)μm^(2)以上,单井涌水量平均60 m^(3)/h,是优质热储。地热水主要来源于古大气降水,由北部燕山补给,沿地层深循环,吸取岩石热量后形成地热水。歧口凹陷区馆陶组热储地热资源量为41.81×10^(18)J,尤以天津滨海新区和河北黄骅市分布最广,占总资源量的95%,资源与需求匹配度高,具有良好的开发利用前景。

歧口凹陷沙一下亚段页岩油井增产措施地质影响因素分析

歧口凹陷沙一下亚段混合质页岩层系发育,孔隙结构主要为微孔-介孔,其中以灰质混合页岩孔隙结构最为发育,含油性以重质稠油为主。经过措施改造后,油井普遍达到工业油流,但尚未明确影响产能的地质因素,对此需要在该区开展相关研究,指导类似油井措施改造增产。根据岩石物性、岩石岩性,以及裂缝发育程度、地层压力和断裂规模、构造形态和曲率、电性参数等数据,总结出“自然产能井”“酸化有效果井”“压裂有效果井”“酸压有效果井”所对应的地质特征,以此来指导措施改造方式的选取。研究结果表明:(1)该区孔隙度低于15%、渗透率低于0.41 mD的页岩层系需经措施改造提产;(2)“自然产能井”以邻近断裂、裂缝较为发育的灰质混合页岩、长英质页岩为主,D值(井到断裂距离与垂直断距比值)普遍小于1,断裂影响较为明显,且构造曲率较大;(3)“酸化有效果井”以灰质混合页岩、云质混合页岩为主,总体上灰质含量较高,D值2.8~7.9,断裂对地层改造程度较弱,构造曲率中等,电性参数ΔGR普遍大于20 API;(4)“压裂有效果井”的D值为1.2~5.2时,以裂缝发育较差的云质混合页岩、长英质页岩为主,D值大于16时,断裂的影响极其微弱,以不发育裂缝的灰质混合页岩为主,“压裂有效果井”对应的构造曲率较小,电性参数ΔGR普遍小于20 API。基于不同产能井的地质因素影响分析,归纳提出“自然产能井”“酸化有效果井”“压裂有效果井”“酸压有效果井”适用的地质环境,指导该区新完钻井采取相应增产措施,改造后达到了工业油流产出标准,有效地提高了油气产量,对油田页岩层系提产具有积极的作用。

大港油田滨海地区钻井地质风险分析及应对措施

为确保大港油田滨海地区钻井安全,并最大限度提升钻井时效,从该地区已钻井发生的钻井复杂情况入手,分析引起该区域钻井风险的主要地质因素及原因,并提出相应的解决措施。研究表明:(1)研究区新近系馆陶组地层埋深较浅,岩石结构松散,底部发育不整合面,古近系沙河街组地层埋藏较深,原始地层压力高,气油比高,这些地质特征导致该区钻井风险较高;(2)研究区钻井复杂情况主要分为两类,一是漏失型,主要是井漏,二是溢出型,包括气侵、溢流和井涌等;(3)研究区漏失型钻井复杂情况的地质风险主要是馆陶组底部弱固结的砂砾岩及馆陶组底部的不整合面,溢出型钻井复杂情况的地质风险主要是沙一段异常高压和丰富的含气量;(4)应对漏失型钻井复杂情况地质风险的主要措施是排查馆陶组底部砂砾岩的空间分布,应对溢出型钻井复杂情况地质风险的主要措施是及时测试地层压力,并据此在钻井过程中实时调整钻井液密度。该研究成果可为滨海地区及地质条件相似的其他地区的钻井施工提供借鉴作用。

源断盖配置油气聚集时期预测方法及其应用

为确定含油气盆地油源断裂处油气富集程度,在烃源岩、断裂和盖层配置及油气聚集机制研究基础上,通过油源断裂活动期、烃源岩排烃期和泥岩盖层形成期,建立了一套源断盖配置下的油气聚集期的预测方法,并利用其预测渤海湾盆地歧口凹陷沙一下亚段内油气聚集时期。结果表明,沙三段烃源岩排烃、南大港断裂开启和沙一中亚段区域性泥岩盖层形成,均为馆陶组—明化镇组沉积期,三者配置关系良好且时期较长,有利于沙三段烃源岩排出的油气在沙一下亚段内聚集成藏,预测结果与勘探成果吻合。

渤海湾盆地歧口凹陷古近系沙三段页岩油储层非线性渗流特征

通过高压压汞与低温气体吸附实验,结合核磁共振在线检测系统和驱替实验,对渤海湾盆地歧口凹陷古近系沙三段页岩油储层的渗流特征进行了研究。研究结果表明:①歧口凹陷古近系沙三段3种岩相页岩的微孔数量占比最大。与块状泥岩相比,纹层状及层状页岩储层的孔径大于100 nm的中大孔喉更为发育,储集性及渗流能力更优。②赋存在页岩储层大孔喉中的可流动油能有效产出,但由于渗流阻力较大,微小孔喉(小于100 nm)中的油即使在很大压差下也难以产出。③页岩储层中的石油渗流具有启动压力梯度和非线性渗流的特征,但不同岩相的渗透特征差异较大,其中纹层状页岩拟启动压力梯度最小,渗流能力最强,层状页岩储层具有一定的渗流能力,块状页岩储层渗流能力最差。在相同压力梯度下,块状页岩中的流量仅为纹层状页岩中流量的10%左右,基本无自然产能。

渤海湾盆地歧口凹陷歧北次凹沙三上亚段页岩岩相特征及含油性差异

页岩岩相精细识别与类型划分是陆相页岩油资源潜力评价的重要基础。采用总有机碳质量分数测试、热解、矿物组成、显微岩石薄片、荧光薄片及高频二维核磁共振(2D-NMR)等方法,识别渤海湾盆地歧口凹陷歧北次凹沙河街组三段上亚段(沙三上亚段)主要岩相类型及特征,分析不同岩相含油性差异。结果表明:歧口凹陷歧北次凹沙三上亚段页岩富含石英、黏土和碳酸盐矿物,w(TOC)平均为1.08%,发育纹层状、薄层状和块状3类层理沉积构造,沙三上亚段细粒岩划分为纹层状页岩相、层状页岩相、块状页岩相、钙质页岩相和粉砂岩相5类岩相,不同岩相储层内部含油性不同,长英质矿物质量分数及沉积构造类型对页岩油含量具有明显的控制作用。纹层状和层状页岩相内部发育大规模由有机质、矿物纹层和薄层控制的孔—缝网结构,为页岩油提供大量的有效储集空间,具有高可动油含量特征;块状和钙质页岩相生烃潜力较差且储层结构相对致密,储集性能较差,具有低可动油含量特征。该结果为渤海湾盆地歧口凹陷歧北次凹沙三段页岩油勘探选区评价提供参考。

油源断裂输导油气演化阶段的确定方法及其应用

为了研究含油气盆地油源断裂处油气富集规律,在油源断裂输导油气条件及其演化阶段研究的基础上,根据油源断裂活动时期和源内、源外油气中转站形成时期,确定了油源断裂输导源内和源外中转站油气时期,建立了油源断裂输导油气演化阶段的确定方法,并利用其确定渤海湾盆地歧口凹陷南大港断裂向沙一下亚段输导油气演化阶段。结果表明:南大港断裂向沙一下亚段输导沙三段源内中转站油气阶段从馆陶组沉积开始至明化镇组沉积中期,输导沙三段源内外中转站油气阶段从明化镇组沉积中期至结束;经历了2个演化阶段,输导油气时期相对较长,有利于来自下伏沙三段源岩的油气在沙一下亚段内大规模聚集成藏。根据本文方法确定油源断裂输导油气演化阶段,能合理解释目前南大港断裂处沙一下亚段油气最富集的现象。此方法适用于油源断裂输导油气演化阶段的确定。

歧口凹陷滨海斜坡深凹区海探1井东营组勘探突破与启示

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