热欧地区残留可容纳空间分布及储集砂体预测_李宏伟

基金项目:中国石油天然气集团公司/九五0科技攻关项目(990903O 06O 01)。

作者简介:李宏伟,男,1968年3月生,1991年毕业于中国地质大学油气勘探开发专业,现为中国地质大学在读博士研究生,主要研究方向为油气储层预测与隐蔽油气藏勘探。

文章编号:0253O 2697(2002)04O 0029O 04热欧地区残留可容纳空间分布及储集砂体预测李宏伟1 邓宏文1 肖乾华2 王红亮1(1.中国地质大学 北京 100083; 2.中国矿业大学 北京 100083)摘要:辽河盆地热欧地区勘探程度低,取心资料少,砂体与油气分布具有较强的隐蔽性。

针对这一问题,首次将层序地层学的原理和方法应用于该区储集砂体分布规律的预测。

对地层的重新划分与对比发现,研究区沙三段内部存在着明显的不整合界面SB 2。

该不整合面的形成期正是河道砂储集体沿层序SQ 2O T ST 沉积初期残留可容纳空间的充填期,因此循着层序界面SB 2寻找沉积古地貌低洼区是预测砂岩储集体的关键。

对比发现,受断裂与火山岩堆集体的联合控制,古地貌低洼区沿沟谷及火山岩体侧翼的断槽一带展布,钻井证实该带是层序SQ 2O T ST 河道砂体的主要充填区。

对这些砂体的成功预测有效地指导了该地区油气勘探。

关键词:热欧地区;层序地层学;残留可容纳空间;沉积古地理;储集砂体;预测中图分类号:TE12211 文献标识码:A热欧地区位于辽河盆地东部凹陷中段,由西部缓坡带、中央断裂背斜构造带和东部潜山带三个构造单元组成(图1),是目前辽河盆地地质条件最复杂、勘探程度最低的地区之一。

长期以来,该区以构造圈闭为主要钻探目标的勘探效果不够理想。

早期的探井集中分布在由火山岩体形成的中央断裂背斜构造带之上,除少数井 图1 研究区构造位置图F ig.1 Location map of study ar ea在火山岩缝隙中获得油流外,绝大多数井在钻遇火山岩后因无良好的砂岩储层发育而停钻。

砂岩储集体分布规律不清制约了该区的油气勘探工作。

开展储集体预测须用新的观点和成熟的理论作指导。

近年来,层序地层学在国内、外受到了广泛的重视[1,2],在储集体预测、隐蔽油气藏勘探、老油田扩边挖潜以及提高采收率等方面都不乏成功的应用[3,4]。

热欧地区沉积背景的复杂性和储集砂体分布的隐蔽性决定了研究工作必须用层序地层学理论作指导。

残留可容纳空间是指可容纳空间减小到最低点时盆地内部仍残存的可容纳空间,其发育的位置在不整合与整合的转换带以下。

识别残留可容纳空间的意义在于残留可容纳空间是不整合面上剥蚀、过路而来的沉积物的堆积区,通过层序划分与对比,找到不整合面与层序界面,然后,沿层序界面通过层序对比、分析找出残留可容纳空间的分布,进而可第23卷 第4期2002年7月 石油学报ACTA PETROLEI SINICA V ol.23 No.4July 2002预测盆地内砂岩储集体的充填规律[5,6],有效指导油气勘探。

1 层序划分在层序地层的划分与对比上,层序地层学强调钻井、地震及古生物资料的综合与统一。

本次研究依据地震反射界面上的上超与削截、古生物组合与演化、火山岩年龄测定以及钻井地层的旋回性信息,将沙河街组细分为5个时限在(1~4)@106a 的三级层序、10个体系域(图2)。

图2 研究区层序地层综合划分 Fig.2 F ramew ork of litho logic sequences in the study area层序SQ 1是在房身泡组顶部不整合面SB 1之上发育起来的低位至水进期的扇三角洲沉积,含砾砂岩与薄层泥岩之中偶见塔螺化石,扇体向西部缓坡带超覆;最大湖泛期发育了富含深水介形类的前扇三角洲湖相泥岩与油页岩沉积,这套泥岩有机质丰富,并已进入生烃门限,为本区的主力烃源岩;层序SQ 1沉积晚期由于火山岩的强烈发育,极大地占据了碎屑岩在湖盆内的可容纳空间,导致可容纳空间迅速减小,盆地边缘以及盆地内部火山岩堆积体之上可见明显的不整合面SB 2发育,不整合面SB 2附近多处可见暴露沉积,火山岩蚀变强烈,局部地区不整合之下湖盆过渡为泥碳沼泽与煤层,代表了扇三角洲平原亚相,也预示着层序SQ 1一个完整的扇三角洲旋回的结束[7]。

层序SQ 2发育初期又一次发生沼泽化。

广布的碳质泥岩预示着可容纳空间的再次扩大,层序界面SB 2为可容纳空间的转换面。

在层序SQ 2中部附近发育了一套分布较为稳定的富含沼泽拟星介、似瘤田螺的泥岩,代表了最大洪泛期小型极浅水泛滥盆地沉积,这套泥岩均未进入生烃门限,但可充当下伏含油储层的稳定盖层或隔层;层序SQ 2上部界面SB 3附近发育零星的红层,断陷内部古地貌高部位可见层序SQ 2顶部地层的明显削截,这是层序SQ 2沉积结束的标志。

界面SB 3是辽河盆地沙三段与其上覆沙二段的分界面,在该界面附近,沙三段顶部地层剥蚀强烈,多处可见沙三段与上覆地层呈角度不整合接触。

在层序SQ 2顶部不整合面SB 2形成期间,断陷内部古地貌低洼部位堆积了层序SQ 3低位体系域沉积。

由以上层序划分结果不难发现,断陷内的残留可容纳空间应在层序界面SB 2附近,因此层序SQ 2O TST 是寻找砂岩储集体的目标层序,即本次研究的目的层。

2 地层对比地层的等时性对比是寻找残留可容纳空间、预测储集体的前提和保证。

在平行中央断裂背斜构造带的联井对比剖面上,对比的等时面选取层序SQ 2最大洪泛面(mfs 2),分隔层序SQ 1与SQ 2的界面SB 2在热15井区为蚀变玄武岩的顶界面,欧19井区为泥碳、煤层的顶界。

煤层的出现是层序SQ 1发育期末湖盆发生淤积、消亡及准平原化的反映[8]。

30 石 油 学 报 2002年 第23卷对比发现,进入本区生烃门限的湖相有效烃源岩主要发育于层序SQ 1水进至最大湖泛期,在热26井与欧35井之间和欧35井与欧19井之间存在断槽。

中央断裂背斜构造带主要是由火山岩堆积体形成的古地貌隆起区,层序SQ 1火山岩体的频繁发育不仅占据了碎屑岩在断陷内的可容纳空间,而且火山岩古地貌高亦成为侧向携砂水流逾越的屏障,限制了砂体在中央断裂背斜构造带上的发育。

局部地区火山岩体之上煤层的发育预示着存在古水流破坏作用极小的低能环境。

因此,层序界面SB 2附近古地貌低部位是寻找层序SQ 1沉积期末残留可容纳空间与储集砂体的重点地区(图3)。

图3 研究区南北向联井地层对比剖面Fig.3 Cross sections of sequence cor relation from south to north in the study area图4 层序SQ 2O T ST 砂体分布规律 Fig.4 Distribution of sandbodies in SQ 2O T ST3 残留可容纳空间识别与砂体预测残留可容纳空间的识别在储集体预测中有重要指导作用。

层序界面形成期的残留可容纳空间分布控制着层序界面附近的储集体的分布。

在热欧地区层序界面SB 2形成期,残留可容纳空间主要分布在中央断裂背斜构造带侧翼的断槽、沟谷一带(图4),断陷西部的中央凸起区及断陷中部的火山岩体高部位可容纳空间小于零而成为物源区与剥蚀区。

钻井与取心资料证实,层序界面SB 2附近的残留可容纳空间发育区往往是河道砂体的发育部位。

河道砂体主要沿层序界面SB 2附近的沟谷[图4(a)]与断槽[图4(b)]一带充填,古地貌高部位之上仅见洪泛期溢岸沉积。

在西斜坡之上的沟谷区,董6井、岭1井一带的冲积扇辫状河砂体呈叠置的丘状体沿沟谷顺坡而下,在热40井与欧31 第4期 李宏伟等:热欧地区残留可容纳空间分布及储集砂体预测32石油学报2002年第23卷35井一带过渡为泛滥平原顶平、底凸的河道砂透镜体。

这种顶平、底凸的透镜体经欧35井取心资料证实为具板状交错层理和槽状交错层理的油浸粗砂岩、中砂岩和细砂岩;在底部冲刷面之上含砾;中、粗砂岩中沿层面发育大量冲刷、撕裂泥砾。

与热26井相当部位发育的波状层理、泥质粉砂岩及粉砂质泥岩的天然堤溢岸相形成共生组合关系。

透镜状砂体为层序界面SB2形成期,在泛滥平原之上残留可容纳空间内河道充填成因[9]。

另外,在热26井东侧还发育了丘状双向下超充填的地震相,目前尚无探井钻遇,但据其与周围堤岸沉积的共生组合关系推测,丘状体可能是决口扇体的反映(图5)。

图5层序SQ2O T ST岩相古地理图F ig.5L itho facies palaeogeographic map of SQ2O T ST利用上述方法对热欧地区砂岩储集体的时空分布规律进行了成功的预测,在新一轮的隐蔽油气藏勘探中,部署于欧35井北部与欧26井西部的欧36井、欧37井均在层序界面SB2附近钻遇河道相砂体,并获得工业油流。

4结论以层序地层学原理和方法为指导,沿层序界面寻找残留可容纳空间的分布规律,这是预测储集砂体的一种重要途径。

一个层序沉积期末,随着可容纳空间的减小,古地貌高地区不整合面开始发育,不整合面的形成期恰是携砂水流搬运、过路而来的砂体在断陷内残留可容纳空间发育区的堆集期。

沿不整合面(或层序界面)寻找残留可容纳空间的分布对储集砂体预测具有重要指导意义。

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T he portion shale strata are evaluated as the best source rock.The average values of org anic carbon are1.84%~ 2.21%in Xiamaling and Hongshuizhuang areas.A lot of carbonate rock strata may be evaluated as the better source rock.The average values of organic carbon are0.2%~0.29%in Tieling and Gaoyuzhuang areas.The aver-age values of organic carbon is0.2%in Wumishan form ation,and some mem ber of the formation are the better source rock.A majority of org anic m atter of source rock may be highly evolved to condensate_w et_methane zone. T he organic matter of source rock of Jibei depression may be evolved into oil generation_condensate_w et zone,and that of Xiahuayuan reg ion be evolved into oil g enerative rock.The result of research show s that Jibei depression is the best reg ion for exploring oil reservo irs,and Jizhong depression is the best region for exploring g as reservoirs. Key words:hydrocarbon source rock;source potential;ex ploration prospects;Middle O Upper Proterozoic;northern ChinaSEQUENC E STRATIGRAPHIC METHODOLOGIES OF PALEOGENE IN DONGPU SAGZHENG Hong_w en(Exp loration Dep ar tment o f Zhongyuan Oilf ield Co.,SINOPEC,Puyang457001,China) ACTA2002,23(4):24~28Abstract:Based on the terrig enous sequence stratigraphic methodologies,the cy clic sequence of Shahejie Formation of fault_depressed lacustrine basin in Dong pu Sag is classified in detail,and the strata contrast framew orks of cyclic sequence of member3of the formation are proposed.T he level of lake surface changed frequently,and the landscape and structure w ere very complex in period of Paleogene in Dongpu sag.On the basis of those features,several se-quence stratigraphic patterns,such as structure_slope break,fault_slope,two_steps and high_frequency types,were developed in consideration the features of composition in different parts of structure and strata distribution.T hose patterns can be used to direct the distribution of reservoirs and determine the oil_gas exploration direction in the member3of Shahejie form ation in Dongpu sag.Key words:Dongpu sag;member3of Shahejie formation;sequence stratig raphic pattern;reservoir distributionPREDIC TION OF REMAINED ACC OMMODATION DISTRIBUTION AND SANDY RESERVOIR OF RE O OU AREA IN LIAOHE BASINV ol.23No.4July2002ACTA PET ROLEI SINICA[3]LI Hong_w ei,et al.(China Univ ersity of Geosciences,Beij ing100083,China)ACTA2002,23(4):29~32 Abstract:Re_Ou area of Liao basin has the features of low exploration degree,lack cored data,and the indecision of sandy hydrocarbon reservoirs.T he sequence stratig raphy was applied to predict the distribution of sandy reservo irs. T he sequence subdivision and correlation show ed the unconform ity of S3member of the study area,i.e.sequence boundary SB2w as discovered between the upper formation and the low er formation of S3member.The duration of the developing period of SB2is the remained accommodation w hen the channel sand bodies filled along the palaeo_ g eomorphologic low.T herefore,the palaeo_geomorphologic low along the sequence boundary SB2is the target area of the sandy reservoirs.T he palaeo_geomorphologic low in Re_Ou area w as governed by faults and volcanic rocks and mainly developed along the flank of the volcanic rocks accumulation.The prediction of sandy reservoirs deve-l oped along the palaeo_geomorphologic low w as effective and verified by drilling.Key words:Re_Ou area;Liaohe basin;sequence stratigraphy;remained accommodation;lithofacies palaeogeog raphy;sandy reservoir;predictionAPPLICATION OF STRATIMAGIC WAVEF ORM C LASSIFICATION TECHNIQUE TO RESEARC H INTO A LITHOLOGIC OIL RESERVOIR IN DAWANGZHUANG AREAZHAO Li_m in,et al.(China University o f Mining and Technology,Beij ing100083,China)ACTA2002,23(4): 33~36Abstract:T he stratimagic w aveform classification method has been used to study the transverse changes of seismic information.The forms of seismic trace can be correlatived and classified by the neural netw ork algorithm,and the horizontal changes of seism ic signals may be described,and then the map of the seismic facies matching to geological facies can be obtained.This method can be used to predict the distribution of reservoir sand body and lithologic oil reservoir.T he application of this method in Daw angzhuang area of Jizhong depression shows a good result.The lo-cations of three w ells has been provided by using the predicted results of this method.The wells has produced oil successfully.A litholog ic oil reservoir w ith a reserve of ten thousand tons has been found in this area.Key words:w aveform classification;neural netw ork algorithm;sand body;litholog ic oil reservoirFINE EVALUATION OF RESERVOIR O C AP COMBINATION USING GRAY SYSTEMSONG Zi_qi,et al.(X i.an Petroleum I nstitute,Xi.an710065,China)ACTA2002,23(4):37~41Abstract:By the use of logg ing,coring,production test and concerning g eology data to m atch,fit and extract param-eters,the eigenvalue as w ell as its accuracy and distinguishability were statistically analyzed,and the formation litholog y,physical properties,oil_bearing property and cap quality were evaluated.A cording to the characteristics of Donghe sandstone in the Silurian,Devonian and Carboniferous formations in T azhong Oilfield,the parameters,stan-dards and w eight coefficients for fine evaluation about reservoir_cap combination are presented on the basis of the g ray system.A method for the fine evaluation and the handling ex amples w ere given.In accordance to the integrat-ed interpretation results of some oilfields,such as T arim,Liaohe,north China,Er_lian,Yan_chang,the reservoir_cap strata parameters,driving pressure,breaking pressure in main intended zones were calculated.Meanwhile,the for-mation lithology,physical properties,oil_bearing property and cap quality were analyzed,and the relationship be-tw een reservoir strata and cap strata is interpreted.T he results may be the basis for prospecting various reservo irs.Key words:gray system;reservoir_cap combination;fine evaluation;standards;analysis method;application exam-ples;effect。