论文详情
川中-川西地区沙溪庙组储层属于致密砂岩气藏, 具有岩石成分复杂、孔隙度低且结构复杂等特点。在构造运动作用下形成了多压力系统共存现象且地层压力在纵横向不同砂体之间变化大。针对沙溪庙组地层压力纵横向不同砂组之间变化大的情况, 提出了一种分类地层压力预测方法。根据实测地层压力数据, 在Shaker划分基础上进行垂向压力单元划分, 利用垂深、电阻率、孔隙度、三孔隙度比、含气饱和度与地层压力系数的相关性, 构建综合压力指数图版对地层压力分类预测, 图版分为超低压图版和常压低压图版两类, 先利用综合压力指数和垂深建立的超低压图版判断压力类型是否为超低压, 属于超低压则应用下伏泥岩吸水原理建立的模型实现超低压压力预测, 不属于超低压则利用常压低压图版判断其压力类型。对比Eaton法、Fillippone测井法以及有效应力法对常压和低压压力的预测结果, 选取Eaton法来预测该类型压力。图版分类符合率达到了85%, 地层压力系数总体预测结果与实测结果符合率达96.15%, 为沙溪庙组地层压力垂向上的分区分类计算和地震地层压力预测提供了刻度基础。
The Shaximiao Formation, located in the central-western Sichuan, is a tight sandstone gas reservoir with a complex rock composition, low porosity, and complex structure. Due to tectonic movements, multiple pressure systems coexist, resulting in significant variation in the formation pressure between different sand bodies vertically and horizontally. A classification formation pressure prediction method was proposed to address this issue. According to the measured formation pressure data, the vertical pressure unit was divided based on the Shaker division and we used parameters such as vertical depth, resistivity, porosity, three-porosity ratio, and gas saturation to analyze the correlation between each parameter and the formation pressure coefficient. Based on this classification, a comprehensive pressure index chart was constructed to predict the formation pressure. There are two types of charts: ultra-low-pressure charts and normal- and low-pressure charts. An ultra-low-pressure chart established by the comprehensive pressure index and vertical depth was used to determine whether the pressure type was ultralow, and the model established by the water absorption principle of the underlying mudstone was used to predict ultralow pressure. The pressure of this type is predicted according to the Eaton method, selected after comparing and predicting normal and low pressures using the Eaton, Fillippone logging, and effective stress methods. The model was based on the principle of water absorption of the underlying mudstone for predicting the ultralow pressure. The coincidence rate of chart classification reached 85%, and the overall prediction result of the formation pressure coefficient was as high as 96.15%. This outcome is consistent with the measured results and provides a calibration basis for the vertical divisional classification calculation of the formation pressure of the Shaximiao Formation and the prediction of seismic formation pressure.