【作者】 刘四兵；

【导师】 沈忠民；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2010， 博士

【摘要】 论文针对川西坳陷中段上三叠统须家河组地层超致密、超大埋深、超高压力以及圈闭形成历史、油气富集规律复杂的特点,从基础资料入手,在研究区成藏基本条件分析的基础上,通过流体地化特征的精细研究、对比,明确了研究区天然气的成因及来源,分析了其纵向变化的运移机制,明确了研究区地层水的来源,探讨了水岩相互作用机制;在地层剥蚀厚度恢复的基础上,通过主力烃源岩生排烃史、包裹体均一温度以及K/Ar测年等多种方法综合确定主要气藏的成藏年代;最后通过典型气藏解剖,分析了研究区须家河组天然气成藏的动态过程,总结了天然气的成藏模式。论文取得的主要结论及创新性成果如下:(1)须家河组烃源岩具有厚度大、分布范围广、有机质丰度高、成熟度高、类型单一(主要以Ⅲ型为主)的特点。(2)须二段天然气与其他层段天然气相比具有甲烷碳同位素相对较高、乙烷碳同位素相对较低的特征,显示须二段天然气经历了更高的成熟度演化并来源于更好的母质类型,可能暗示了早期古油藏裂解气的混合。(3)天然气纵向上的规律性变化主要体现了天然气成熟度和运移过程中分馏作用的影响。原、次生气藏纵向上的运移机制具有较大的差异:上侏罗统天然气主要由下部须家河组天然气窜层渗流运移而来,断裂是其最重要的运移通道;中侏罗统天然气运移方式复杂,部分气藏由须家河组气源沿高速运移通道运移而来,而部分气藏是通过下部气源以水溶相的方式运移聚集成藏;须四段天然气以扩散运移方式为主,反应该层段天然气成藏时储层已相对致密;须二段天然气则以渗流方式为主,断裂在其中起到了重要的作用。(4)气源对比表明,合兴场地区侏罗系天然气主要来源于须五段烃源岩,中侏罗统源岩是其有力的补充;洛带地区侏罗系天然气主要来自于须五段和中下侏罗统源岩,须四段源岩有一定的贡献;金马地区侏罗系天然气主要来自中、下侏罗统;新场地区侏罗系天然气主要来自于须五段源岩,中、下侏罗统源岩是其有力的补充,须四段源岩对其有一定的贡献;鸭子河地区侏罗系气源为须四段烃源岩;中江地区侏罗系天然气主要来源于须五段烃源岩。丰谷地区须四段天然气主要来自于其自身烃源岩,须三段烃源岩对其有一定贡献;新场地区须四段天然气主要由须四源岩提供气源,表现为自身自储的性质;高庙子地区须二段天然气由小塘子-马鞍塘组和须二段源岩共同提供气源;新场地区须二段天然气主要来源于须二段和小塘子-马鞍塘组源岩;中江和合兴场地区须二段天然气则主要来源于小塘子-马鞍塘组烃源岩。而对于须四段天然气表现出的自生自储的性质,应主要与天然气样主要为须四上亚段的缘故,须三段源岩对下亚段天然气应具有较大的贡献。(5)研究区须家河组地层水总体表现为大气淡水背景,后期有海相地层水的入侵,泥页岩及煤层压实水对水性质影响巨大。须二段和须四段地层水地化特征相似性不仅是由于跨层流动造成的,共同来源的海相地层水和泥页岩压释水是根本原因,两者地层水的差异性主要是两者不同的水岩作用体系造成的,须四段相对须二段具有更为开放的水岩作用体系。(6)喜山期地层平均剥蚀厚度达到了1400m左右,在平面上具有如下变化特点:龙门山前从北往南剥蚀厚度逐渐变小,大邑地区具有相对最小的剥蚀厚度;从龙门山前往东,剥蚀厚度逐渐减小;从北往南地层剥蚀厚度逐渐减小;从西往东,则表现为先变小后变大的特征,鸭子河地区剥蚀较强、往东到马井地区剥蚀厚度变小,再往东到中江剥蚀厚度又变大。(7)研究区大量样品、尤其是裂缝样品的包裹体均一温度远远超过地层所经历的古地温,顺断裂、裂缝而来的热液应是造成其温度偏高的主要原因。(8)须二段天然气具有持续充注的特点,主要有3个重要的成藏期:分别为须五段-早侏罗统沉积时期、中侏罗统-早白垩沉积时期和喜山期,其中中侏罗统-早白垩沉积时期为最主要的成藏阶段,其余两个相对次要;须四段天然气同样具有持续充注的特点,其对应的主要成藏期有:须五段沉积中期-早侏罗统沉积时期、晚侏罗统-早白垩沉积时期和喜山期,晚侏罗统-早白垩沉积时期为最重要的成藏时期,喜山期主要对早期原生气藏进行改造。(9)须二段天然气富集主控因素为:1)现今构造控制了局部构造的气水分异,是油气富集的关键,古今构造高部位是天然气聚集的最有利区;2)断裂是气藏晚期调整的关键。裂缝,尤其是高角度裂缝是气藏高产的关键,同时也是地层水纵窜入侵的主要通道;3)储层的非均质性是气层非均质性分布的根本原因;4)有利的沉积微相是优质储层发育的基础。(10)须四段天然气富集主控因素为:1)古今构造是气、水分布的基础;2)裂缝和有利沉积相对控制的优质砂岩储层的叠加是须四下亚段高产、稳产的关键;3)保存条件,尤其是成藏关键时期的保存条件是形成须四上亚段目前气水分布局面的最主要因素。更多还原

【Abstract】 For the characteristics of the Triassic Xujiahe formation in the middle of the western Sichuan depression, which has super dense, super depth, high pressure and the history of trap formation and the complexity of oil and gas accumulation, this paper starts from the basic information, on the basis of the basic forming conditions of the study area, through the detailed study and contrast of fluid geochemical characteristics, we known the causes and sources of natural gas, and analyzed migration mechanism of longitudinal changes, the sources of the formation water and the mechanism of water-rock interaction. Based on the recovery of formation eroded thickness, through many methods, such as the history of the main hydrocarbon source rock generation and expulsion, the package body with homogenization temperature, and K/Ar dating, etc, we identified the forming age of major gas accumulation. Finally, through the anatomy of typical gas reservoir, we analyzed the dynamic process of natural gas accumulation of Xujiahe in the study area, and summed up the gas accumulation model. The main conclusions and innovative achievements are as follows:(1)The characteristics of hydrocarbon source rock of Xujiahe formation was large thickness, wide distribution, high organic matter abundance, high maturity, and single type(the main type wasⅢkerogen).(2)The characteristics of gas of member 2 compared with other members of Xujiahe formation shown that the methane carbon isotope of member 2 was higher than that of other members, and ethane carbon isotope of member 2 was lower than that of other members. This shown that gas of member 2 udergoed higher organic maturation evolution and came from better mother substance, which hint the blending of the ear1y paleo-oil pools pyrolysis gas.(3)The longitudinal regular change of gas mainly embodyed the gas maturity and fractionation effect in migration process. The longitudinal migration mechanism of the primary pool and the secondary pool had great difference. The main resource of the upper Jurassic gas was the underneath Xujiahe formation gas, and faults were the first migration pathway. The migration manner of the middle Jurassic gas was complex, one part came from Xujiahe formation gas through high speed migration pathway, the other came from the underneath Xujiahe formation gas in hydrotrope. The mainly gas migration manner of member 4 of Xujiahe formation was diffusion, which reflected that the reservoir bed was fine and close when the gas accumulated. The mainly gas migration manner of member 4 of Xujiahe formation was transfusion, in which faults played an important role.(4)Gas source comparison indicated that the Jurassic gas of HeXingChang mainly came from the member 5 of Xujiahe formation hydrocarbon source rocks, and the middle Jurassic source rock was its powerful supplement. Jurassic gas of LuoDai mainly came from the middle and the lower Jurassic system, the member 4 of XuJiahe formation had certain contribution. The Jurassic gas of JinMa mainly came from the middle and the lower Jurassic. The Jurassic gas of XinChang mainly came from the member 5 of XuJiahe formation hydrocarbon source rocks, the middle and the lower Jurassic source rock were its powerful supplement. Jurassic gas of LuoDai mainly came from the middle and the lower Jurassic, the member 4 of XuJiahe formation had certain contribution. Jurassic air hydrocarbon source rocks of Ducks river area mainly came from the member 4 of XuJiahe formation. The Jurassic gas of ZhongJiang mainly came from the member 5 of XuJiahe formation hydrocarbon source rocks. The Jurassic gas of the member 4 of XuJiahe formation of FengGu area mainly came from its own hydrocarbon source rocks. The gas of the member 4 of XuJiahe formation of XinChang area was mainly provided by gas source of the member 4 formation source rocks, and had nature of self-generation and self-storage. The gas of the member 2 of XuJiahe formation of GaoMiaoZi area was mainly provided by gas source of both XiaoTangZi-Saddle group and the member 2 of XuJiahe formation. The gas of the member 2 of XuJiahe formation of XinChang mainly came from the member 2 of XuJiahe formation and XiaoTangZi-Saddle group hydrocarbon source rocks. The gas of the member 2 of XuJiahe formation of XinChang and ZhongJiang mainly came from the member 2 of XuJiahe formation and XiaoTangZi-Saddle group hydrocarbon source rocks. However, for the nature of self-generation and self-storage of the gas of the member 4 of XuJiahe formation, we think that the main reason was the gas samples mainly came form the upper mild-segment of T3x4, and the mother rock of the member 3 of XuJiaHe formation should make great contribution to the lower mild-segment of member 4 of Xujiahe formation.(5)The main formation water of Xujiahe formation was atmosphere fresh water, but at the later stage there was marine facies formation water intruding, and argillutite and the coal bed compaction water affected water properties tremendously. The geochemical characteristics similarity of formation water of member 2 and member 4 of Xujiahe formation was caused not only by cross-formation flow, but also mainly by the common resource such as marine facies formation water and argillutite compaction released water. The geochemical characteristics divergence of formation water of member 2 and member 4 of Xujiahe formation was mainly caused by different water-rock interaction, for the member 2 had more open ended water-rock interaction than that of member 4.(6)The average eroded thickness of Himalayan movement formation was around the 1400m, in the plane, there had the following changeable characteristics: the eroded thickness gradually became smaller from north to south in front of Longmen Mountain, Dayi region had relatively minimal the eroded thickness. From in front of the Longmen Mountain to the east, the eroded thickness gradually reduced. The western Sichuan depression had the characteristics of the eroded thickness decreased from north to south. From west to east, the performance shown larger after smaller, the erosion of Duck River region was stronger, from east to the Horse Well region, the eroded thickness was smaller, and then east to the zhongjiang region, the eroded thickness became larger.(7)The homogenization temperature of inclusion enclave of great quantity sample, especially the fissure sample, overtook the palaeogeothermal far away, the main reason of which was hydrothermal fluid through the faults and fissures.(8)The gas of member 2 of Xujiahe formation had the characteristic of persistent infusion, which had 3 important communicating stages, as follows: member 5 of Xujiahe formation-early Jurassic sedimentation, middle Jurassic-early Crataceous sedimentation and Himalayan movement.Middle Jurassic-early Crataceous sedimentation was the foremost stage of gas communication, the other were less important relatively.The gas of member 4 of Xujiahe formation had the same characteristic of persistent infusion, and the corresponding communicating stages are the middle sedimentation of member 5 of Xujiahe formation-early Jurassic sedimentation, late Jurassic-early Crataceous sedimentation and Himalayan movement. Late Jurassic-early Crataceous sedimentation was the foremost stage of gas communication, and Himalayan movement mainly reformed the early primary gas pool.(9)The master control of natural gas concentration of member 4 of Xujiahe formation was: 1) Structure nowadays controlled the gas and water distribution of local structure, which was the key factor of oil and gas concentration, and ancient and modern structure eminence was the most favorable place for gas concentration. 2) Faults were the key factor of late period regulatory of gas pool. Fissure, especially the high angle fissure was not only the key factor of gas pool high production, but also the main invasion channel of formation water. 3) The reservoir heterogeneity was the fundamental reason of gas horizon heterogeneity. 4) The beneficial deposition microfacies were the base of superior quality reservoir development.(10)The master control of natural gas concentration of member 4 of Xujiahe formation was: 1) Ancient and modern structure was the base of gas and water distribution; 2) Cracks and favorable sedimentary facies superimposed the controlled superior quality sandstone reservoir was the key factor of high production and stable yields of the lower mild-segment of member 4 of Xujiahe formation; 3) The preservation conditions, especially the preservation conditions of reservoiring critical period, was the most key factor of gas and water distribution of the upper mild-segment of member 4 of Xujiahe formation.更多还原