【作者】 汪华；

【导师】 刘树根；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2009， 博士

【摘要】 至今为止,在四川盆地中三叠统只发现了中坝和磨溪两个大中型气藏(田),龙女寺、潼南、罗渡三个含气构造,尚未发现区域上成带分布的气田群。中三叠统雷口坡组为一套白云岩、石灰岩、泥页岩及石膏沉积,纵向上分五段,雷五段又称天井山组。雷口坡组岩性纵向上变化频繁,横向上差异较大。四川盆地中西部中三叠统主要为局限台地相和开阔台地相沉积,部分地区为蒸发台地相,主要亚相为泻湖和潮坪,川西发育有台地边缘滩微相,川中发育有台内滩微相。中三叠统破坏性成岩作用主要有5类:压实收缩和压溶作用、胶结作用、重结晶作用、自生矿物(黄铁矿、天青石、硬石膏等)的形成、溶孔及裂缝的充填作用;建设性成岩作用主要有3类:白云石化作用、溶蚀作用(膏溶、岩溶作用)和构造破裂作用。四川盆地中部雷口坡组储层为中孔低渗,储集空间多以溶蚀孔隙为主,喉道与孔隙的连通性差,裂缝不发育。孔隙既是储集空间,也是渗滤通道,孔渗的不匹配是气藏低渗低产的主要地质因素。盆地西部雷口坡组储层孔隙度较高,裂缝发育,储层连通性好,储集类型为裂缝—孔隙型,储集空间主要为粒间、粒内溶孔,裂缝是主要的渗滤通道。中三叠统存在有四种优质储层:滩相藻砂屑白云岩储层、古岩溶储层、礁滩储层和热液白云岩储层。四川盆地中三叠统的勘探常以寻找滩相藻砂屑白云岩储层为目标。古岩溶作用能使储层物性得到有效的改善,因而古岩溶储层也成为近年来雷口坡组勘探的重要目标。龙深1井、中46井礁滩组合的确定预示着川西可能发育有礁滩储层。龙深1井、中46井、青林1井、涞1井、磨16、22井、女深2井、遂47井、营21井等多口井热液矿物组合的发现预示着川西、川中可能发育有热液白云岩储层。磨溪中三叠统气藏天然气为混源气,以煤成气为主,油型气为辅,其煤成气主要来自于上二叠统龙潭组煤系烃源岩,油型气来自二叠系腐泥型烃源岩。中坝中三叠统气藏天然气也为混源气,但以油型气为主,煤成气为辅,其油型气主要来自二叠系腐泥型烃源岩,也可能有来源于更深层位的油裂解气,其煤成气来源于上三叠统须家河组的煤系烃源。磨溪和中坝气藏都具有烃源丰富、储层优质、圈闭形成早、保存条件好四个特征。磨溪T2l11气藏成藏主要经历了三个阶段:①中～晚三叠世烃源岩持续生烃和幕式排烃;②晚三叠世末构造圈闭形成和印支—燕山期天然气聚集;③喜玛拉雅期圈闭最终形成,天然气爆发式成藏。磨溪中三叠统气藏成藏模式:通过异常高压产生的裂缝,龙女寺构造二叠系烃源岩生成的油气垂向运移到T2l11储层,再侧向运移至磨溪构造,形成磨溪中三叠统气藏。中坝T2l3段气藏成藏主要经历了四个阶段:①中三叠世末表生成岩期—近地表孔隙建造期;②晚三叠世中晚期古背斜圈闭形成;③燕山期构造继承性发展—油气聚集;④喜玛拉雅期气藏最终定型。中坝中三叠统气藏成藏模式:位于彰明断层上盘的二叠系油型裂解气向上运移至雷三储层,位于彰明断层下盘的上三叠统煤成气,在往高处运移时,穿过彰明断层,侧向“倒灌”到上盘T2l3储层中,造成天然气的混源,形成中坝中三叠统气藏。四川盆地中三叠统油气成藏的主控因素有:①丰富的烃源条件,良好的保存条件和输导体系是油气成藏的基础和前提;②古构造和古隆起对中三叠统油气分布有明显的控制作用,对油气起着早期运聚指向的作用;③沉积相、成岩作用和构造破裂作用控制了优质储层的形成和分布。更多还原

【Abstract】 So far, there were only two medium-scale gas fields found in the Middle Triassic Series (Leikoupo formation) of Sichuan Basin. The Middle Triassic Leikoupo formation is composed up of dolostone, limestone, shale and anhydrite, which could be divided into five members (Lei-1, Lei-2, Lei-3, Lei-4, and Lei-5). Lei-5 is also called Tianjingshan fromation. The lithology of Leikoupo formation varies vertically and horizontally.The restricted-platform and open-platform facies are predominant facies of Leikoupo formation in the west-Central Sichuan Basin, and the evaporative platform facies could be found as well. The main subfacies are lagoon and tidal flat. The western Sichuan basin has platform marginal bank microfacies, while the central Sichuan basin has platform inner bank microfacies. In the Leikoupo formation, compacting shrink & pressolution, cementation, recrystallization, the forming of authigenic mineral (pyrite, celestine, and anhydrite) and filling of pore or fracture are five destructive diagenesis for the pore formation. The constructive diagenesis for the pore formation is dolomitization, dissolution (anhydrite dissolution, karst) and fracturing.The Leikoupo reservoir in the Central Sichuan Basin is medium porosity and low permeability. The main reservoir space is dissolved pore, poor connectivity between throat and pore, and fracture is not developed. The non-match of porosity and permeability is the vital geological factor of low gas production rate. On the contrary, the Leikoupo reservoir in the western Sichuan basin has high porosity, and fracture is well developed with good reservoir connectivity. It is a type of fracture-pore reservoir, and the reservoir space is intergranular & intragranular dissolved pore, while fracture is the main percolation channel.There are four types of good reservoir in the Middle Triassic Series in the western-central Sichuan basin: alga arenitic dolomite reservoir of bank facies, karst reservoir, reef & bank reservoir and hydrothermal dolomite reservoir. The exploration target is used to looking for alga arenitic dolomite reservoir of bank facies in the Middle Triassic Series of Sichuan Basin. The paleokarst improved reservoir conditions effectively, thus the paleokarst reservoir are becoming the recent exploration target in Leikoupo formation. The reef & bank reservoir is possibly developed in Western Sichuan basin. Reef & bank lithology combination is discovered in the well of Longshen 1 and Zhong 46. Furthermore, the hydrothermal dolomite reservoir may be developed in the Middle-Central Sichuan resulting from the discovering of hydrothermal minerals in the well of Longshen 1, Zhong 46, Qinglin 1, Lai 1, Mo 16, Mo 22, Nvshen 2, Sui 47 and Ying 21 etc.The Moxi Middle Triassic gas field is a mix-source gas which contains main coal-genetic gas and a few petroliferous gas. The coal-genetic gas is from Upper Permian Longtan formation coal measure source rock, while the petroliferous gas is from Permain sapropel source rock. The Zhongba Middle-Triassic gas field is also a mix-source gas, but contains main petroliferous gas and a few coal-genetic gases. The petroliferous gas is possibly from Permian sapropel source rock. The coal-genetic gas is from Upper Triassic Xujiahe formation coal measure source rock .Both Moxi and Zhongba gas reservoirs have abundant hydrocarbon source, good reservoir rocks, early formed trap and good preservation condition. Moxi T2l11 gas reservoir has undergone three phases:①middle-late Triassic source rock generating hydrocarbon continuously and releasing hydrocarbon episodically,②the structure trap forming in the end of late Triassic Epoch, and gas trapped in the Yinzhi-Yanshan period,③trap finally formed in Himalaya period and the natural gas reservoir formed explosively. Moxi Middle Triassic gas reservoir forming model is: the Permian source hydrocarbon of Longnv structure migrated vertically to the T2l11 reservoir and then migrated to Moxi structure laterally through fractures caused by abnormal high formation pressure.Zhongba T2l3 gas reservoir has undergone four phases:①epidiagenetic stage in the end of Middle Triassic Epoch to the near surface pore build-up stage,②ancient shielding forming stage in the Middle-Late Triassic Epoch,③the deep buried, big scale, complex hydrocarbon forming stage during the Yanshan period,④hydrocarbon reservoir ultimately formed during the Himalaya period. Zhongba Middle Triassic gas reservoir forming model is as follows. The Permian oil cracking gas in the hanging wall of Zhangming fault migrated upwards to T2l3 reservoir. When the Upper Triassic coal-genetic gas in the footwall of Zhangming fault migrated upwards and passed through Zhangming fault, the gas moved downwards to Lei-3 reservoir and formed the gas field.Main factors controlled hydrocarbon accumulation of middle Triassic in the western-central Sichuan Basin. Rich hydrocarbon source, good conservation and conduit system are the base and precondition of hydrocarbon accumulation. Paleo-uplift and paleostructure had obviously controlled the middle Triassic hydrocarbon distribution. Depositional facies, Diagenesis and structural fracturing controlled the forming and distribution of high-quality reservoir.更多还原