吐鲁番坳陷西山窑组富煤的河流沉积与储集层的成岩作用研究

Diagenesis of the coal-rich fluvial sediments and reservoirs in the Xishanyao Formation,Turpan depression,Xinjiang

关键词:  曲流河  砂岩复合体  储集层  成岩作用

Key words:  meandering river  sandstone complex  reservoir  diagenesis

摘要:

吐鲁番坳陷西山窑组（J₂x）发育一套含煤的陆相沉积地层,本文根据钻井资料进行研究后认为这套地层属于曲流河沉积,并进一步划分出河道沙坝和漫滩沼泽等沉积类型。煤层形成于漫滩沼泽沉积环境。曲流河道砂体是主要的油气储集体。位于坳陷东南区的曲流带河道砂岩复合体是储集砂岩最发育的地区。储集砂岩类型主要为矿物成熟度较低的岩屑砂岩和长石岩屑砂岩。坳陷东南区复合体河道砂岩以长石岩屑砂岩为主,而坳陷北区河道砂岩以岩屑砂岩为主。西山窑组储集层主要的成岩作用为压实作用、胶结作用和溶解作用。坳陷东南区复合体砂岩典型的成岩作用为溶解作用,溶解作用导致砂岩形成以溶蚀孔隙为主的孔隙空间。坳陷北区河道砂岩典型的成岩作用为压实作用,压实作用导致砂岩储集层的物性很差。

Abstract:

A series of coal-bearing continental strata was laid down within the Xishanyao Forma-tion,Turpan depression,Xinjiang.These strata are interpreted in this paper as the mean-dering river deposits in accordance with well logs,which in turn may be subdivided into channel bar and backswamp deposits.The coal seams commonly occur in the backswamp environment.The meandering channel sandbodies appear as the substantial reservcir sand-stones.For instance,the channel sandstone complexes occupy the meander belts in the southeastern part of the depression,where the reservoir sandstones are well developed. The reservoir sandstones consist mostly of lithic sandstones and feldspathic litharenite with lower mineral maturity.The channel sandstone complexes are dominated by felds-pathic litharenite in the southeastern part of the depresison,where the dissolution is be-lieved to be the typical diagenesis resulting in the formation of pore spaces with solution pores of sandstones.The channel sandstones comprise the bulk of lithic sandstones in the northern part of the depression,where compaction is considered as the typical diagenesis giving rise to the poor physical properties of the reservoir sandstones.The diagenesis of the reservois in the Xishanyao Formation are mainly manifested in compaction,cementation and dissolution.