高温超压储层孔隙演化的物理模拟实验

Physical simulation experiments on pore evolution in high-temperature and overpressure reservoirs

目前比较常见的是常压条件下的储层演化模拟,而异常高压条件下的储层演化模拟则少见。为了进一步明确高温超压对于储层孔隙演化的定量化影响,以琼东南盆地乐东—陵水凹陷中新统“高温超压”储层为研究对象,在对该区沉积、成岩背景下温度压力场划分的基础上,应用自然类比法和物理模拟实验等手段,分析不同温压场背景下的孔隙演化特征,探讨超压、流体对储层孔隙演化的影响,明确优质储层发育的主控因素。研究结果表明:①乐东—陵水凹陷中新统储层的温压场可划分为高温常压、高温超压和高温强超压等3个区;②超压和强超压对原生孔隙具有一定的保护作用,在同一成岩阶段,超压和强超压储层的面孔率较常压储层面孔率高1.23%~6.74%,超压、强超压区地层压力每超过静水压力8 MPa、4 MPa时,其对应保护的原生孔隙约为1%;③有机酸溶蚀作用对储层次生孔隙具有较大的贡献,较正常压实储层的面孔率增加0.96%~7.38%;④大气水淋滤作用对储层物性的影响微弱,较正常压实储层的面孔率仅增加0.19%。结论认为:①有机酸溶蚀是高温常压背景下储层中最具建设性的作用;②超压对原生孔隙的保护是高温超压和强超压背景下储层中最具建设性的作用,并且超压越强对孔隙的保护作用就越大。

At present, simulation on reservoir evolution under normal pressure is common while that under abnormal pressure is rare. In this paper, the Miocene "high-temperature and overpressure" reservoir in the Ledong–Lingshui Sag of the Qiongdongnan Basin was taken as the research object to quantitatively define the effects of high pressure and overpressure on the evolution of reservoir pores. After the temperature and pressure field in this area was divided in the setting of sedimentation and diagenesis, the evolution characteristics of pores in different temperature and pressure field were analyzed by means of natural analogy and physical simulation experiment. Then, the effects of overpressure and fluids on the evolution of reservoir pores were discussed. Finally, the main factors controlling the development of high-quality reservoirs were determined. And the following research results were obtained. First, the temperature and pressure field of the Miocene reservoir in the Ledong–Lingshui Sag can be divided into three zones, i.e., high temperature and normal pressure zone, high temperature and overpressure zone, and high temperature and super overpressure zone. Second, overpressure and super overpressure can provide some preservation on primary pores. In the same diagenetic stage, the plane porosity of overpressure and super overpressure reservoirs is 1.23%–6.74% higher than that of normal pressure reservoirs. Once the reservoir pressure in overpressure and super overpressure areas is higher than hydrostatic pressure by 8 MPa and 4 MPa, respectively, about 1% primary pores are preserved. Third, the dissolution of organic acid makes greater contribution to the secondary pores in reservoirs and its plane porosity is 0.96%–7.38% higher than that of normal compacted reservoirs. Fourth, the leaching effect of meteorological water on reservoir physical properties is slight, and its plane porosity is only 0.19% higher than that of normal compacted reservoirs. In conclusion, the dissolution of organic acid is the most constructive effect for the reservoirs in high temperature and normal pressure. In addition, preservation of primary pores by overpressure is the most constructive effect for the reservoirs in high temperature and (super) overpressure, and the higher the overpressure is, the more preservation effect it provides on pores.