塔里木盆地库车坳陷北部构造带侏罗系阿合组储层特征及控制因素

塔里木盆地库车坳陷北部构造带具有巨大的油气勘探潜力,但储层物性平面差异性显著,控制因素不明确,制约了优质储层的预测。综合露头、岩心、薄片及成像测井资料,对库车坳陷北部构造带下侏罗统阿合组的储层特征进行了描述,分析了储层裂缝特征及形成期次,探讨了沉积、成岩和构造应力对储层的控制作用,明确了储层特征平面差异性的主控因素。结果表明:阿合组以灰白色中砂岩、粗砂岩和薄层砾岩为主,砂岩主要为长石岩屑砂岩和岩屑砂岩;储集空间在露头区以粒内溶孔、裂缝和原生粒间孔为主,在井下以微孔隙和粒内溶孔为主;储层物性在平面上具有显著差异性。阿合组主要发育直立和高角度的剪切裂缝,充填程度较低;微观裂缝在露头区以粒缘缝为主,在井下以粒内缝为主;发育3期裂缝,形成于喜马拉雅晚期的裂缝有效性最好。沉积作用主控阿合组储层基质物性,压实作用是主要的减孔作用,溶蚀作用是主要的增孔作用,但都并非储层特征平面差异性的主导因素;古构造挤压应力具有减孔降渗和造缝增渗的双重效应,控制了阿合组储层特征的平面差异性。

Characteristics and controlling factors of Jurassic Ahe reservoir of the northern tectonic belt,Kuqa Depression,Tarim Basin

The northern tectonic belt of Kuqa Depression has an enormous potential for hydrocarbon explora?tion,but the reservoir physical property of Middle and Lower Jurassic has significant horizontal difference and the controlling factors are not clear,which constrain the prediction of high quality reservoir.Based on outcrops,cores,thin sections and image logging data,petrology characteristics,reservoir space types,physical property of Lower Jurassic Ahe Formation in the northern tectonic belt of Kuqa Depression were described,and the char?acteristics and formation sequence were analyzed.Then,based on above,the controlling effects of sedimenta?tion,diagenesis and paleo-tectonic stress on reservoir were discussed,and the dominant factor of the horizontal difference of reservoir was confirmed.The results show that Ahe Formation is mainly composed of grey-white medium sandstone,coarse sandstone and conglomerate lamina,and the sandstones are primarily feldspar lithic sandstone and lithic sandstone.The reservoir spaces are mainly intragranular dissolved pore,micro fracture and original intergranular pore in outcrops,while mainly micro pore and intragranular dissolved pore underground.The reservoir physical property has significant lateral differences.The Ahe Formation primarily develops verti?cal and high angle shearing fractures,and the fractures have lower filling extent.Micro fractures are chiefly grain-edge micro fractures in outcrops while mainly intragranular micro fractures underground.There are three periods of fractures in the study area,and the fractures formed at the Late Himalayan have the best effective?ness.The deposition dominates reservoir physical property of Ahe Formation,and the compaction is the prima?ry effect of porosity loss while the dissolution is the chief effect of porosity increase.However,they are not the dominant factor for reservoir horizontal differences.The paleo tectonic stress has a double effect on reservoir.One effect is reducing porosity and permeability,and the other effect is forming fractures and increasing permea?bility,which dominate the horizontal reservoir differences of Ahe Formation.