柴达木盆地英西地区古近系下干柴沟组上段TSR与储层改造

硫酸盐热化学还原反应（TSR）作为溶蚀作用的一种重要机制在储层研究中具有重要意义。通过岩心观察、薄片鉴定、扫描电镜、测井等资料的分析，研究了柴达木盆地英西地区下干柴沟组上段TSR特征及其对储层的改造作用。研究结果表明：①TSR反应物主要为烃类与硫酸盐岩，生成物为高含量的H₂S，CO₂及蚀变烃类、方解石、单质硫、黄铁矿、含硫有机物等，反应起始温度为100~140℃，对应英西地区地层深度为3 113~4 536 m。②英西地区下干柴沟组上段TSR造成了碳酸盐岩孔缝充填物种类繁多，主要包括晶粒状和块状黄铁矿、单质硫及沥青等蚀变矿物，含硫矿物的δ³⁴S值偏大；天然气烃组分具有甲烷含量高、重烃含量低的特征，干燥系数偏大，碳同位素δ¹³C₁值和δ¹³C₂值较大，并且常见H ₂S及相对较高含量的CO₂等TSR生成物，地层水盐度降低。③TSR相关流体对碳酸盐岩储层进行了改造，埋藏溶蚀作用发育，形成了不同规模的孔洞系统，平均增孔率可达3.5%，在一定程度上优化了储层物性。

Thermochemical sulfate reduction(TSR)and reservoir reformation of the upper Paleogene Xiaganchaigou Formation in Yingxi area,Qaidam Basin

As an important mechanism of dissolution,thermochemical sulfate reduction(TSR)is of great significance in reservoir research.Through the analysis of core observation,thin section identification,scanning electron microscope and logging data,the TSR characteristics and its effect on reservoir reformation of the upper member of Xiaganchaigou Formation in Yingxi area of Qaidam Basin were studied.The results show that:(1)The reactants of TSR are mainly hydrocarbons and sulfate rocks,and the products are high-content H₂S,CO₂,altered hydrocarbons,calcite,elemental sulfur,pyrite,sulfur-containing organic matter.The initial reaction temperature is 100-140℃,corresponding to the formation depth of 3113-4536 m in Yingxi area.(2)TSR of the upper member of Xiaganchaigou Formation in Yingxi area resulted that carbonate pores and fractures were filled with modified minerals such as granular and massive pyrite,elemental sulfur and asphalt.Theδ³⁴S value of sulfurbearing minerals is relatively heavy.The hydrocarbon components of natural gas are characterized by high methane content and low heavy hydrocarbon content,and the dryness coefficient is larger.The carbon isotopeδ¹³C₁ andδ¹³C₂ values are larger,and the TSR products such as H₂S and relatively high content of CO₂ are common.The salinity of formation water is low.(3)TSR related fluids reformed carbonate reservoir,and burial dissolution developed,forming pore systems of different sizes,with an average pore increase rate of 3.5%,which optimized reservoir physical properties.