石油与天然气地质
石油與天然氣地質
석유여천연기지질
OIL & GAS GEOLOGY
2015年
2期
255-261
,共7页
宋土顺%马锋%刘立%蒙启安%于严龙%刘娜%于淼
宋土順%馬鋒%劉立%矇啟安%于嚴龍%劉娜%于淼
송토순%마봉%류립%몽계안%우엄룡%류나%우묘
碳%氧同位素%方解石胶结物%岩石学%扶余油层%大庆长垣
碳%氧同位素%方解石膠結物%巖石學%扶餘油層%大慶長垣
탄%양동위소%방해석효결물%암석학%부여유층%대경장원
carbon and oxygen isotope%calcite cement%petrology%oil-bearing Fuyu layer%Daqing Placanticline
方解石是大庆长垣深层砂岩中广泛分布的一种胶结物，同时方解石胶结作用是大庆长垣扶余油层致密储层的控制因素之一。以方解石胶结物为研究对象，运用薄片鉴定，扫描电镜观察、X－射线衍射分析、包裹体测试和碳、氧同位素分析，查明方解石碳、氧同位素组成及其成因。研究结果表明，储层砂岩类型为长石岩屑砂岩和岩屑长石砂岩，粘土以I／S（伊／蒙混层）＋I（伊利石）＋K（高岭石）组合为代表。方解石的碳同位素（δ13 C，PDB）分布范围是－20.3‰～－3.2‰，氧同位素（δ18 O，PDB）的分布范围是－25.3‰～－20.3‰，平均值为－22.67‰。碳、氧同位素分析数据的计算表明，碳酸盐的相对古盐度值（ Z）介于73.92～109.89，表明其形成时的古流体均为矿化度较高的淡水；方解石的形成温度为80～100℃。方解石胶结物的同位素显示，其形成与有机酸脱羧作用有关，暗示其“碳”来源为有机碳。
方解石是大慶長垣深層砂巖中廣汎分佈的一種膠結物，同時方解石膠結作用是大慶長垣扶餘油層緻密儲層的控製因素之一。以方解石膠結物為研究對象，運用薄片鑒定，掃描電鏡觀察、X－射線衍射分析、包裹體測試和碳、氧同位素分析，查明方解石碳、氧同位素組成及其成因。研究結果錶明，儲層砂巖類型為長石巖屑砂巖和巖屑長石砂巖，粘土以I／S（伊／矇混層）＋I（伊利石）＋K（高嶺石）組閤為代錶。方解石的碳同位素（δ13 C，PDB）分佈範圍是－20.3‰～－3.2‰，氧同位素（δ18 O，PDB）的分佈範圍是－25.3‰～－20.3‰，平均值為－22.67‰。碳、氧同位素分析數據的計算錶明，碳痠鹽的相對古鹽度值（ Z）介于73.92～109.89，錶明其形成時的古流體均為礦化度較高的淡水；方解石的形成溫度為80～100℃。方解石膠結物的同位素顯示，其形成與有機痠脫羧作用有關，暗示其“碳”來源為有機碳。
방해석시대경장원심층사암중엄범분포적일충효결물，동시방해석효결작용시대경장원부여유층치밀저층적공제인소지일。이방해석효결물위연구대상，운용박편감정，소묘전경관찰、X－사선연사분석、포과체측시화탄、양동위소분석，사명방해석탄、양동위소조성급기성인。연구결과표명，저층사암류형위장석암설사암화암설장석사암，점토이I／S（이／몽혼층）＋I（이리석）＋K（고령석）조합위대표。방해석적탄동위소（δ13 C，PDB）분포범위시－20.3‰～－3.2‰，양동위소（δ18 O，PDB）적분포범위시－25.3‰～－20.3‰，평균치위－22.67‰。탄、양동위소분석수거적계산표명，탄산염적상대고염도치（ Z）개우73.92～109.89，표명기형성시적고류체균위광화도교고적담수；방해석적형성온도위80～100℃。방해석효결물적동위소현시，기형성여유궤산탈최작용유관，암시기“탄”래원위유궤탄。
Calcite is one the most widely spreading cements in deep sandstone reservoirs in Daqing Placanticline .It has also been regarded as the main factor for facilitating the formation of tight reservoirs in oil-bearing Fuyu layer .Thin sec-tion,scanning electron microscope ,X-ray diffraction,fluid inclusion and carbon/oxygen isotope analyses were carried out on calcite from cored wells penetrating the layer to identify its isotope composition and genesis .The results show that the reservoirs are mainly feldspar lithic and lithic feldspar sandstone with clay minerals represented by I /S+I+K assem-blage.The cement has its δ13C(PDB)value ranging between -20.3‰ and -3.2‰ and the δ18O(PDB)value varying from -25.3‰to -20.3‰with an average value of -22.67‰.Calculation shows that the paleosalinity Z is between 73.92 and 109.89 ,indicating a fresh water environment with high salinity for the formation of carbonate .The temperature for the calcite to be formed is between 80℃and 100℃based on converted temperature of isotopes and homogenization temperature of fluid inclusions .Isotope diagrams reveal that the formation of the calcite cement is probability connected with organic acid decarboxylation ,inferring an “organic carbon” origin for the carbon in the cement .
