新疆三塘湖盆地二叠系构造裂缝研究

【作者】 赵小会；

【导师】 周鼎武；

【作者基本信息】 西北大学 ， 构造地质学， 2005， 硕士

【摘要】 三塘湖盆地位于新疆东北部,是一个叠置在古生代造山带褶皱基底之上的晚古生代—中新生代的叠合、改造型含油气沉积盆地。盆地沉积盖层包括二叠系—第三系,其中二叠系是盆地主要的油气储集层,并具低孔低渗特点,裂缝为主要的储集空间,因此本文对三塘湖盆地二叠系的裂缝(主要为构造裂缝)进行了研究,以便为该盆地油气勘探开发提供理论基础和基础资料。 本文遵循“整体、动态、综合”的研究原则,在对三塘湖盆地进行地质演化分析的基础上,利用地震资料、钻井岩芯资料、显微观察资料、古地磁资料及实验资料从构造地质学和储层地质学角度对三塘湖盆地的二叠系裂缝特征及低孔低渗裂缝性储层进行了初步研究,取得了如下认识: 三塘湖盆地经历了长期的地质演化,形成现今的由西南逆冲推覆隆起带、中央坳陷带和东北冲断隆起带组成的两隆夹一坳的构造格局。中央坳陷带是三塘湖盆地重要的含油气区带,该带受盆地抬升剥蚀影响缺失上二叠统和下三叠统,中侏罗统西山窑组在盆地内分布最广,中晚侏罗—早白垩世盆地构造格局定形,形成现今的南低北高、东低西高的复式向斜格局,并控制了残余沉积盖层的分布。 三塘湖盆地二叠系发育与盆地构造作用相关的三期构造裂缝,即受晚海西期区域挤压作用的影响发育在残余二叠系中的裂缝组合;受晚燕山期区域挤压构造作用的影响,在三叠系—侏罗系—下白垩统中形成的裂缝组合,该期构造同时叠加、改造二叠纪地层,形成新的裂缝组合;受喜山期挤压—走滑构造作用的叠加改造,在二叠系—三叠系—侏罗系—白垩系中形成的裂缝组合。 三塘湖盆地二叠系不同时期构造裂缝的发育,在宏观上具有与坳陷带中褶皱、断裂发育密切相关的不均一性,其产状受断层产状和褶皱的部位控制。裂缝发育以北东向、北西向为主,近东西向次之,裂缝一般宽约0.04mm—2mm,线密度在0.3条/m—5条/m之间。早期裂缝已被方解石、浊沸石充填,但并非是无效裂缝。 结合宏观裂缝和微观裂缝特征及水驱油实验进行裂缝有效性分析,认为三塘湖盆地二叠系多数构造裂缝是有效裂缝(与油气运移关系密切)。本区二叠系裂缝性储层水驱油包括定向驱油型和非定向驱油型两种基本类型。其中基质物性和裂缝特征均影响着水驱油效率,裂缝特征是主要的影响因素。同时研究表明在裂缝周围如果存在溶蚀裂缝,也有利于提高基质驱油效率。 分析裂缝对低孔低渗储层的孔隙度、渗透率和非均质性方面的影响,并结合构造演化、地震剖面、有利油藏区带分析等资料,对二叠系构造裂缝进行了评价和初步预测。认为条湖凹陷、马朗凹陷的南部逆冲推覆前缘带为最佳构造裂缝发育区,也是油气最有利聚集区带。更多还原

【Abstract】 Santanghu basin which lies to northeast of Xinjiang province is a type of rebuilt superposition sediment basin in late Paleozoic to middle Cenozoic which superposed on the fold basement of Paleozoic orogen belt. Permian to Tertiary strata comprises sedimentary cover of the basin.the Permian strata are main gas and oil reservoir of the basin,which possesses the low porosity and low permeability characteristics and the fracture is the main reservoir space.So the study on Permian structure fracture of Santanghu basin possesses important theoretical and practical significance.This paper keeps up the research principles of integration,dynamic and synthesis,on the basis of the analysis of geology evolvement make use of seismic data, core of drilled well information,microscopic study materical,paleomagnetism materical and experiment data study elementarily the characteristics of the fractures of the Santanghu basin and the fracture effecting on the low porosity and low permeability reservoir from geology and reservoir.After study ,we get to know that:Santanghu basin came through a long period of time of geology evolution and formed the structure pattern of one depression sandwiched by two uplifts from southwest to northeast which making up of thrusting nappe belt,the center depression belt and thrust uplift belt.The center depression belt is the important oil-bearing belt of Santanghu basin and the belt lacked upper Permian and late Trias trata being the Santanghu basin uplifted and denuded.Xishanyao group in mid-Jurassic of the basin distributed mostly wide.Middle and late Jurassic to early Cretaceous the basin formed the pattern which relatively high in northern and western compound syncline.And the structure pattern controlled the distributing of remainder sediment cover.Santanghu basin developed three stage structure fracture related to structure of basin.Firstly,the fracture combination developed in the remainder Permian which effected by region compression in late Hercynian.Secondly,effected by region compression in late Yanshan stage formed fractures combination in Trias,Jurassic and late cretaceous strata. In the same time ,the structure in second stage superposed and rebuilt the Permian stratum and formed new fracture combination.Thirdly,it formed fracture combination in Permian,Trias,Jurassic and Cretaceous strata effected by the compression-strike-slip structure superposed and rebuilt process.The different stage structure fracture developed in Santanghu basin possessed megascopically inhomeogeneity which related close with folds and faults of depression belt,and the occurrence was controlled by the occurrence of the faults and parts of the fold.The fracture developed very well, mostly in direction from north to east and north to west ,and secondly from east to west .And the fracture is 0.04-2mm wide.The line density is between 0.3bar/m-5bar/m.The earlier fracture was filled by the calciteand laumontite,but they still belong to the usable fracture.The most of the Permian structure fracture is useful learned by the characters of fracture and the water displacing oil experiment. To the fracture reservoir,making use of the microcosmic model to simulating the water displacing oil phenomenon,the results show that the fracture reservoir water displacing oil in this region has the two ways of the directional and undirectoinal water displacing oil.the physical property of the matrix and the fracture characteristics are also working on the water displacing oil efficiency.The fracture characteristic is the main factor.Meanwhile,if the corrosion phenomena occurs around the fracture,the formed solution fracture is propitious to improve water displacing oil efficiency in matrix.The fracture effects porosity, permeability and heterogeneity in low permeable reservoir.The Permian structure fracture is evaluated and forecasted based of the tectonic evolvement, the interpreting of seismic section, the favorable reservoir analysis. As a result, the south thrusting nappe belt of the Tiaohu depression and Malang depression are considered as the structure fractures main region, at the same time which is the greatest reservoir.更多还原