塔里木盆地古生界砂岩热成熟度与有效储层的预测

Sandstone Thermal Maturity and Effective Reservoir Prediction of Paleozoic of Tarim Basin

根据砂岩热成熟度的概念,认为塔里木盆地古生界砂岩的孔隙度主要受控于与地热场、埋藏时间和盆地沉降方式有关的砂岩热成熟度。用热成熟度比用深度可更合理地解释砂岩孔隙度的发育特征及其成因。TTI值可综合反映热成熟程度,TTI值越大,砂岩的热成熟度越高,成岩强度越大,被保存的孔隙度越小。若已知盆地的地温梯度,可计算出预测储层的TTI值,并可用本文提出的砂岩热成熟度—孔隙度和热成熟度—深度的两个定量关系预测砂岩区域孔隙度值和有效储层的最大保存深度。应用此法预测塔里木盆地中—上志留统岩屑砂岩和下石炭统石英砂岩有效储层最大保存深度,效果良好。

It is considered that the Paleozoic sandstone porosity of Tarim Basin is mainly controlled by sandstone thermal maturity related with geothermal field, burial time and subsidence type of the basin based on the concept. It is more reasonable to explain the charac- teristics and origin of the sandstone porosity with thermal maturity than with burial depth. The value of TTI may be used as a compos- ite index of thermal maturity. The bigger the TTI, the higher the sandstone thermal maturity, the bigger the diagenetic grade, the less the preserved sandstone porosity. The value of TTI of predict- ed reservoir may be calculated if the geothermal gradient of the basin is known. Further the regional porosity of the predicted sand- stone and the maximum preservation depth of the effective reservoir may be get by the method presented by the paper. The maximum preservation depths of the effective reservoirs of Middle-Upper Sil- urian lithic sandstone and Lower Carboniferous quartzose sandstone in Tarim Basin were predicted by this method. The result is satis- factory.