川东北地区元坝气田与普光气田长兴组气藏特征对比分析 - 图文-

1、收稿日期2011208210作者简介陈丹(19812,女,2004年长江大学毕业,硕士,工程师,现主要从事油气地球化学方面的研究工作。川东北地区元坝气田与普光气田长兴组气藏特征对比分析陈丹(中国石化勘探南方分公司勘探研究院,四川成都610000摘要通过天然气地球化学特征、地层水地球化学特征对比分析表明,元坝气田和普光气田长兴组气藏天然气中烃类气体均以甲烷为主,非烃气体H 2S 含量普光气田高于元坝气田;元坝气田天然气甲、乙烷碳同位素明显重于普光气田;普光气田长兴组气藏水型为重碳酸钠型与氯化钙型,元坝长兴组气藏水型为氯化钙型,显示元坝气田长兴组在油气聚集和赋存方面可能更有优势。烃源岩分布和气源对

2、比研究认为,二叠系烃源岩是普光和元坝气田长兴组天然气的主要气源层;成藏模式的对比分析表明元坝气藏和普光气藏的输导体系存在一定的差异,普光气藏输导体系为断层和储集层,而元坝气藏为裂缝和储集层。关键词元坝气藏;普光气藏;长兴组;气藏特征中图分类号TE12211文献标识码A 文章编号100029752(20111020011204川东北目前探明了盆地储量最大、储量丰度最高的普光气藏1,2,也发现了具有大中型气田特征的元坝气藏。两气藏构造上位于开江2梁平海槽台地边缘两侧,是发育大中型生物礁气藏的有利相带3,4,具有相似的沉积和成藏背景。普光气田和元坝气田同属于台地边缘生物礁气藏,对两气藏展开成藏作用的

3、比较研究,明确其相似性和差异性,对油气成藏富集规律的研究和勘探开发都具有重要的意义。1天然气地球化学特征111天然气组分天然气组成分为烃类气和非烃类气体。烃类气体中依据CH 4所占的比例常用干燥系数(C 1/C 125表示,分别以干燥系数0195和0170为分界线,将天然气分为干气、湿气和高湿气3种类型。根据测试井段气样组分分析资料求平均值(表1,元坝气田和普光气田长兴组气藏天然气中烃类气体分别占84193%和7713%,其中均以C H 4为主,相对含量均高于9915%;C +2以上重烃很少,多数低于1%;相应的干燥系数基本上都在0199以上,高者近于110,表明为高热演化程度的干气。表1普光

4、气田和元坝气田长兴组天然气组成气藏井号组分含量/%CH 4C 2H 6C 3H 8CO 2H 2S N 2He H 2C 1/C 125相对密度/kg m -3元坝Yb189153010701198711811201010103019992016241Yb118211601060111316118012501010102019993016313Yb1018115101078010091116371154151010120165019989-Yb102841330105010391724136114501010102019991016828Yb28711201030716141540165010

5、10103019997016596普光Pg27510701240815715166014301010102019968017356Pg6751920105010281741417101490101010601999001734Pg9701530103014111416016100019995017861Pg887167010601011012111940102011019992016615天然气化学成分组成的另一个特点是非烃气体含量高,其中主要是H 2S 和CO 2。元坝气田H 2S 平11石油天然气学报(江汉石油学院学报2011年10月第33卷第10期Journal of Oil and G

6、 as T echnology (J 1J PI Oct 12011Vol 133No 110均含量5188%,CO 2平均含量6145%; 普光气田两者的平均含量远高于元坝气田,分别达11124%和10141%。由于非烃气体丰富,因而天然气相对密度较高,元坝气田平均相对密度为016495g/cm 3,普光气田其平均值达017407kg/m 3。H 2S 含量的差异,可能表明与储岩的孔隙性质及相应的TSR (硫酸盐热化学还原作用作用强度大小有关。图1元坝地区和普光地区甲烷碳同位素和乙烷碳同位素相关图112天然气碳同位素特征乙烷碳同位素反映原始母质类型,甲烷碳同位素侧重于反映热演化程度5。普光气

7、田长兴组天然气的甲烷碳同位素大多集中在-3011-3115范围,进一步说明天然气演化程度很高;相比之下,乙烷的碳同位素值分布范围相对较宽,主要分布在-2319-3213之间。元坝地区长兴组天然气甲烷碳同位素较重,13C 1值多在-28186-2918之间,明显重于普光地区的同层位气层;乙烷碳同位素也很重,13C 2值为-25131-3217(图1。元坝地区这些天然气碳同位素重的原因主要是成熟度高所致。该气层埋深达7000m 上下,古地温可能达200以上,天然气的热演化程度很高,导致烷烃气碳同位素很重,与其很干的化学组成相一致。另外,TSR 作用对烷烃气的碳同位素比值也会有重要影响,一般随TSR

8、 作用的持续增强,乙烷及甲烷碳同位素会逐渐变重。同时,元坝地区可能比普光地区含有更多陆源有机质的龙潭组烃源岩直接生成的天然气的贡献,是该区天然气的碳同位素比普光气田要重的原因之一。2地层水化学特征地层水中各种离子的含量反映了所在地层的水动力特征和水文地球化学环境,在一定程度上可以说明油气的保存和破坏条件。无机组分是油田水化学组分的重要组成部分,常量包括K +、Na +、Ca 2+、Mg 2+、Ba 2+、Cl -、HCO -3、SO 2-4等。从水型分析数据表(表2可以看出,普光地区长兴组p H 值为9,Cl -含量介于2613930005mg/L ,HCO -3含量介于13053084mg/

9、L ,Na +K +含量介于1570318813mg/L ,Ca +含量介于6363807mg/L ,总矿化度介于5098251771mg/L ,水型为重碳酸钠型与氯化钙型。元坝地区长兴组p H 值为6,Cl -含量介于37598106000mg/L ,Na +K +含量介于1211213113mg/L ,Ca +含量介于631142900mg/L ,总矿化度介于58133170000mg/L ,水型为氯化钙型。据氯钠比等特征系数,烃类聚集与水型关系的密切程度序列为:氯化钙型>重碳酸钠型>氯化镁型>硫酸钠型。这表明元坝气田和普光气田地层水在纵向水文地质剖面上具有深层交替停滞状

10、态特征,地层水处于还原环境,反映储层良好的封闭条件,对油气聚集与赋存非常有利。同时,元坝气田长兴组在油气聚集和赋存方面可能更有优势。表2元坝气田和普光气田长兴组地层水化学组成及类型气藏井号p H 值离子浓度/mg L -1Na+K+Ca2+Mg2+Cl-SO 2-4HCO -3CO 2-3总矿化度/mg L -1水型普光Pg8915703380720130005283130546751771CaCl 2Pg991881363630261399383084134250982Na 2CO 3元坝Yb96121126311211237598-58133CaCl 2Yb2613113429001730

11、1060006222460-170000CaCl 23天然气来源分析资料表明,川东北各层系海相可能烃源岩的有机质丰度有较大的差异。如图2所示,下三叠统飞仙关组(T 1f 岩性主要为鲕滩白云岩及泥晶灰岩,TOC (总有机碳含量值很低,大多在015%以21石油天然气学报(江汉石油学院学报2011年10月图2川东北各层系可能烃源岩T OC 值分布直方图下,99个样品平均值仅0131%;相比其他层位海相烃源层来说,其生烃能力很低,不能作为主要的烃源层。上二叠统长兴组(P 2ch 生物灰岩及礁灰岩的TOC 值总体上也不高,90个样品平均值为0139%。茅口组(P 1m 及栖霞组(P 1x 灰岩50个样品

12、TOC 的平均值为0177%,表明具有一定的生烃能力。上二叠统龙潭组(P 2l 烃源岩有机质含量较高,144个样品TOC 平均值达2193%,在有机质丰度上属优质烃源岩。其TOC 分布范围较大,低者不足015%,高者达10%以上。普光地区该层位以暗色泥岩、碳质泥岩及泥灰岩为主,总体的有机质含量较高,其TOC 平均值在5%7%范围。元坝地区该层位岩性出现相变,上部以泥质灰岩为主,下部以黑色泥质岩为主,TOC 值有所降低,其平均值为219%。储层沥青是古油藏原油或运移烃的热演化产物。对于高热演化的焦沥青来说,通过与烃源岩干酪根的碳同位素对比来确定其来源是一种有效的方法。正常原油的碳同位素比相应源岩

13、干酪根轻12,而固体沥青的碳同位素要比其原始原油重236。研究表明,龙潭组(吴家坪组烃源岩干酪根的13C 值为-2613-2816,普光和元坝地区长兴组沥青碳同位素主要在-25-29范围变化,这样,固体沥青的13C 值要高于烃源岩干酪根12。按照沥青2烃源岩碳同位素的数据关系,与研究区上二叠统吴家坪组泥质岩干酪根具有很好的对比性。经烃源岩分布和气源对比研究认为二叠系烃源岩是普光和元坝气田长兴组天然气的主要气源层。4成藏模式差异从基于烃源岩的生烃演化历史、圈闭发育历史、断层和裂缝的发育历史及输导体系演化历史角度,普光气田的油气藏形成过程可描述为(图3:1晚印支2早燕山期古油藏形成。该期普光构造位

14、于开江古隆起西北翼,北东向断裂发育并沟通源岩,由大气淡水溶蚀作用以及白云岩化作用形成的优质储集层也已经形成,由断层和连通性白云岩储集层共同构成垂向和侧向的输导体系。烃源岩进入生油高峰,由烃源岩生成的古原油沿断层和白云岩储集体北西和南东两个方向充注,并最终形成古油藏。2早燕山2中燕山期古油藏裂解并发生TSR 化学改造。随着地层埋深加大,古油藏的温度超过160,古油藏开始裂解,在大规模抬升剥蚀之前,古油藏温度超过200,古油藏完全裂解成气藏。在断层和储集体输导层的有效输导下,古气藏形成并局部调整。3晚燕山期2喜山期构造调整,气藏再聚集。晚燕山期以来,特别是喜山期以来,随着大巴山强烈挤压推覆,普光构

15、造的西南部隆起成为局部高点,导致古气藏在断层和储集体输导层的有效输导下调整再聚集,气2水界面也随之相应调整。元坝气田的天然气聚集成藏,大体经历以下几个阶段(图4:31第33卷第10期陈丹:川东北地区元坝气田与普光气田长兴组气藏特征对比分析 图3普光气田油气成藏演化图图4元坝气田油气成藏演化图1晚印支期2早燕山期晚印支期,上二叠统烃源岩已经成熟,但构造背景稳定,不发育断层和裂缝,使得长兴组储集层不能构成有效的输导体系。早燕山期,上二叠统烃源岩进入生油高峰,受盆缘造山挤压影响,该区其构造活动强度虽远不及宣汉普光构造,但发育了层间裂缝,沟通源岩(长兴组和龙潭组,使得原油得以在长兴组和飞仙关组聚集并形

16、成岩性油藏。2中燕山期古油藏温度超过160,开始裂解并形成气藏。此期间裂缝也较发育,与储集体一起继续构成有效输导体系,上二叠统烃源岩进入生气阶段,可能继续为气藏提供气源。3晚燕山期以来受米仓山和大巴山强烈活动影响,整个元坝区块由沉积期的向北东倾变为整体向北倾,且在元坝6井区发生局部隆起。对长兴组生物礁顶部的岩性气藏来说,可能会造成气水界面的重新调整,但仍不会破坏已经形成的天然气藏。两气藏构造上位于开江2梁平海槽台地边缘两侧,具有相似的沉积和成藏背景,油气藏形成过程分析表明,两气藏在成藏时间上具有一致性,输导体系存在一定的差异,普光气藏输导体系为断层和储集层,元坝气藏为裂缝和储集层。5结论1元坝

17、气田和普光气田长兴组气藏天然气中烃类气体均以甲烷为主,非烃气体H 2S 含量普光气田高于元坝气田;元坝气田甲、乙烷碳同位素明显重于普光气田,成熟度高和TSR 作用都对碳同位素有一定的影响;地层水化学特征表明普光气田长兴组水型为重碳酸钠型与氯化钙型,元坝气田长兴组水型为氯化钙型,相比之下,元坝气田长兴组在油气聚集和赋存方面可能更有优势。2经烃源岩分布和气源对比研究认为,二叠系烃源岩是普光和元坝气田长兴组天然气的主要气源层。3元坝气藏和普光气藏在成藏时间上具有一致性,输导体系存在一定的差异,普光气藏输导体系为断层和储集层,元坝气藏为裂缝和储集层。参考文献1Ma Y ongsheng ,Guo Xu

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19、机理J 1海相油气地质,2000,5(2:14515215戴金星,戚厚发1我国煤成烃气的13C 与R o 关系J 1科学通报,1989,34(9:69069216Machel H G ,Krouse H R ,Sassen R 1Product s and distinguishing criteria of bacterial and t hermochemical sulfate reduction J 1Ap 2plied Geochemistry ,1995,10:3733891编辑宋换新41石油天然气学报(江汉石油学院学报2011年10月【Sponsored by Yangtze U

20、 niversity】J OURNAL O F OIL AND GAS TECHNOLO GY (JOURNAL OF JIANGHAN PETR OL EUM INSTITUTEJ1JPIVol133No110Oct12011ABSTRACTS01Application of Q uantitative G rain Fluorescence(QGFAnalysis in Low Permeability Sandstone R eser2 voirsA C ase Study of Chang4+5Oil Form ation in OrdosB asinG AO Jian2bo,ZH A

21、NG H ou2he,PANG X iong2qi,CHE N Dong2xia,WANG Zhi2xin,J I ANG Zhen2xue,WANG Xue2dong,WANG Y in2zhen(Fi rst A ut hors A d d ress:CN OOC Research I nstit ute,Bei j ing100027,ChinaAbstract:About100tight sandstone core samples in Chang4+5Oil Formation in Jiyuan Area of Ordos Basin were ana2 lyzed1The re

22、sults show that Q GF index and quantitative grain fluorescence extraction(Q GF2Ein tight sandstone of Chang4+ 5Oil Formation are relatively lower and the relationship between them is complex,it indicates that the differences in reservoir formation of low permeability thin interbed sandstone are obvi

23、ous1It is divided into four types of microscopic filling mechanisms, such as peak expulsion full filling type,peak expulsion less filling type,post peak expulsion filling type,unfilling type1Q GF is effective means of detecting oil2bearing segments in low permeability thin interbed1K ey w ords:Q GF2

24、E;Q GF;low permeability;tight sandstone;reservoir formation06Ch aracteristics and Its E volution P attern of B ohu Depression in E arly2middle Jurassic System of Yanqi B asin LI X iao2gang,X U G uo2qiang,CAI K un,SH AO Wei2min,HE Jian,LI U Hang,Y AN Y ong2xin,ZH ANG Hui(Fi rstA ut hors A d dress:Col

25、lege of Energy Resources,Cheng du Universit y of Technolog y,Cheng du610059,S ichuan,Chi naAbstract:It was still a controversial issue on the natures of Mesozoic basin in Yanqi Basin,it focused on its features in early2middle J urassic system1In this paper,on the basis of predecessorsstudies,the sei

26、smic data f rom Bohu Depression were used for structural interpretation,4regional seismic profiles were selected for stratigraphic correlation,identifica2 tion and interpretation of faults,and then original structural shape of sedimentary basin was restored to find out some ev2 idences to illustrate

27、 the basins nature and its original structural shape in early2middle J urassic system(f rom J1b to J2s 1The results show that Bohu Depression is a depression basin in relatively weak shearing compressive stress in early2mid2 dle J urassic1In combination with the plain distribution of fault system an

28、d the position of the studied area,the structural evolution pattern in the area is proposed based on the distribution feature of fault system in the study area and its struc2 tural position1K ey w ords:Yanqi Basin;Bohu Depression;J urassic;basin nature;evolution mode11Difference Analysis of Changxin

29、 Formation G as R eservoir bet w een Puguang G as Field and Yu anba G as Field in the Northeast of Sichu an AreaCHE N Dan(A ut hors A d dress:Research I nstit ute of Pet roleum Ex ploration and Develop ment,S out h B ranch,S I N O P EC, Cheng du610000,S ichuan,ChinaAbstract:Through analysis of gas g

30、eo2chemical characteristics and geochemical characteristics of formation water,it indi2 cated that hydrocarbon gases of Changxin Formation in Yuanba G as Field and Puguang G as Field were mainly methane, and H2S content of non2hydrocarbon gas in Puguang Gas Field was higher than that of Yuanba G as

31、Field1The ethane car2 bon isotope of Yuanba G as Field was significantly higher than that of Puguang Gas Field1The water type was heavy sodi2 um carbonate and calcium chloride in Changxin Formation of Puguang G asField,calcium chloride was in Changxin For2 mation of Yuanba Gas Field1It indicated tha

32、t the accumulation of oil and gas occurrence may be more advantageous in Yuanba G as Field1The research indicates by distribution of source rock and gas source correlation that the main gas source is Permian source rocks1The comparative analysis of reservoir2forming pattern shows that there are some

33、 differ2 ences in transportation system in Yuanba G as reservoir and Puguang gas pool1The pathway system of Puguang G as Pool is fault and reservoir,and Yuanba Gas Reservoir is f racture and reservoir1K ey w ords:Yuanba G as Reservoir;Puguang Gas Reservoir;Changxin Formation;characteristics of gas r

34、eservoir15H ydrocarbon2generating Potential and Correlation of Oil Sources in H uizhou Oil2enriched Depression SHI Y u2ling,H OU Du2jie,MA Ning(A ut horsA d d ress:School of Energ y Resources;Key L aboratory of M arine Reservoi r Evo2 l ution and H y d rocarbon A ccumulation Mechanism(Minist ry of E

35、ducation,China Universit y of Geosciences,B ei j ing100083,Chi2 naAbstract:For the purpose of evaluating the hydrocarbon generation potential in the hydrocarbon enriched depression of Huizhou Depression,on the basis of analyzing the abundance and types of organic matter f rom54wells in Huizhou De2 p

36、ression,the hydrocarbon generation potential of the source rocks was evaluated,oil2source was correlated by means of organic petrology,rock pyrolysis and geochemistry analyses1The results show that the lacustrine facies mudstone of Wenchang Formation is the most important hydrocarbon source rock,while the coal measure mudstone of Enping Forma2 tion ha