库车前陆盆地大北地区砂岩储层致密化与油气充注的关系

库车前陆盆地大北地区盐下致密砂岩储层具有埋藏深度大、低孔和低渗的特征，以产气为主并伴生少量的轻质原油.在对大北地区盐下致密砂岩储层特征、油气成熟度、油气充注史研究基础之上，结合致密砂岩孔隙演化特征综合分析油气充注与储层致密化的时间关系.大北地区盐下致密砂岩储层孔隙空间主要以次生溶蚀孔为主，大部分孔隙空间都被沥青充填，由孔隙和沥青组成的空间网络具有较好的连通性，压实作用为储层致密化重要成因，碳酸盐胶结作用应该主要在库车组沉积之前使孔隙度降低.致密砂岩储层中发育沥青，油气地球化学特征以及流体包裹体分析结果均表明库车前陆盆地大北地区致密砂岩储层存在两期油和一期天然气充注.晚期原油充注发生在距今5~4 Ma，对应库车组沉积早期，天然气充注发生在距今3~2 Ma，对应地层抬升剥蚀时期.库车前陆盆地大北地区盐下砂岩储层在油充注时期埋藏深度较浅，具有较高的孔隙度，而天然气充注时期，砂岩储层已经遭受了强烈的压实作用达到了致密化程度. 

Relationship between Tight Sandstone Reservoir Formation and Petroleum Charge in Dabei Area of Kuqa Foreland Basin

The tight sandstone reservoirs below the salt and gypsum unit in the Dabei area of the Kuqa foreland basin are characterized by deep burial, low porosity and permeability, which produce natural gas and minor light oil. The relationship between tight sandstone reservoir formation and petroleum charge in the Dabei area of the Kuqa foreland basin are studied by combining the porosity evolution of the tight sandstone reservoirs based on the analysis the tight sandstone reservoirs characters, natural gas and light oil maturity, and petroleum charge history. The pore space of the tight sandstone reservoirs below the salt and gypsum unit in the Dabei area are dominated by secondary intergranular dissolution pores, most of which are filled by bitumen and have an excellent interconnectivity. Strong compaction is the important cause for the development of the tight sandstone reservoirs and carbonate cements should form before the Kuqa formation deposition to cause the porosity decreasing. The presence of widespread bitumen observed in the K₁bs tight sandstone reservoir, organic geochemistry characters of light oil and gas, results of fluid inclusions investigation indicate that there had been two episodes of oil and one episode of gas charge in the tight sandstone reservoir. The late episode of oil charge identified in the tight sandstone reservoir is estimated to be at around 5-4 Ma, responding to the beginning of Kuqa formation deposition. The timing of the natural gas charge is estimated at around 3-2 Ma and are belong to the period of the uplift and erosion. The tight sandstone reservoirs below the salt and gypsum unit in the Dabei area of the Kuqa foreland basin have shallower burial deep and higher porosity during the period of oil charge than natural gas charge because the sandstone reservoirs had experienced strong compaction and cause the formation of tight sandstone reservoirs.