准噶尔盆地车排子地区下白垩统清水河组储层成岩作用及物性影响因素

通过岩石薄片观察、扫描电镜、X-射线衍射以及碳氧同位素分析等岩矿测试分析手段研究了准噶尔盆地车排子地区下白垩统清水河组储层的成岩作用和储层物性的影响因素。准噶尔盆地车排子地区清水河组储层主要经历了压实作用，碳酸盐、方沸石、黄铁矿和黏土矿物胶结作用，以及局部少量的长石和石英的溶蚀作用。根据胶结物的占位关系确定了研究区清水河组储层成岩演化序列，即黄铁矿胶结—方沸石胶结—碳酸盐胶结—长石和石英溶蚀。根据自生碳酸盐矿物的氧同位素值确定了研究区碳酸盐胶结发生在早成岩阶段B期。车排子地区下白垩统清水河组储层成岩相分为以下6种类型：①砾岩胶结相；②砾岩杂基充填相；③(粉)砂岩弱_中压实相；④(粉)砂岩强压实相；⑤(粉)砂岩胶结相；⑥杂(粉)砂岩杂基充填相。准噶尔盆地车排子地区清水河组储层物性直接受控于3个因素：杂基含量、压实作用以及胶结作用。杂基含量主要受控于沉积相展布，辫状分流河道和水下分流河道微相杂基含量较低，而漫滩沼泽和水下分流河道间微相杂基含量较高。压实作用主要决定于地层的埋深，研究区东南部埋深较大，故压实作用更强。胶结作用的强度不易预测，但发生时的深度小于3 800m。最后提出了车排子地区清水河组储层物性主要影响因素的综合模式。

Diagenesis and factors affecting reservoir properties of the Lower Cretaceous Qingshuihe Formation,Chepaizi area,Junggar Basin,China

Through rock thin section observation,scanning electronic microscopy(SEM),X-ray diffraction,carbon and oxygen isotope analysis and other rock & mineral analysis technologies,we studied the diagenesis and factors affecting reservoir properties of the Lower Cretaceous Qingshuihe Formation.The main diagenetic events of the reservoir are compaction,cementation of carbonate,analcime,pyrite and clay minerals and a spot of feldspar and quartz dissolution in local place.Diagenetic sequence of the Qingshuihe reservoir in the study area was identified from occupying relationship between cements,namely pyrite cementation-analcime cementation-carbonate cementation-feldspar and quartz dissolution.Carbonate cementation occurred in early diagenetic phase B in the Qingshuihe Formation according to the oxygen isotopic values of authigenic carbonate minerals.The diagenetic facies of the Lower Cretaceous Qingshuihe reservoir are:(1)conglomerate cementation facies;(2)conglomerate matrix filling facies;(3)siltstone or sandstone weak- moderate compaction facies;(4)siltstone or sandstone strong compaction facies;(5)siltstone or sandstone cementation facies;(6)graywacke or miscellaneous siltstone matrix filling facies.Properties of the Lower Cretaceous Qingshuihe reservoir are directly controlled by the following three factors:Matrix content,compaction and cementation.The content of the matrix is mainly controlled by the distribution of the sedimentary facies.Braided channel and underwater braided channel microfacies have lower matrix contents whereas back swamp and underwater distributary interchannel microfacies have higher matrix contents.The extent of compaction is mostly related to the burial depth of the formation.It is buried deeper in the southeast of the study area,so compaction is stronger there.Cementation intensity is not easy to predict,but burial depth of the strata was less than 3 800m when cementation took place.Finally,an integrated model is proposed to illustrate how theses main factors affect the properties of Qingshuihe reservoir in Chepaizi area.