STUDY ON SEEPAGE CHARACTERISTICS OF TIGHT RESERVOIRS UNDER MULTI-FIELD COUPLING
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摘要: 储层岩石的渗流特性对致密砂岩储层的评价及开发具有重要意义。为此,研究构建热流固耦合控制方程,采用COMSOL Multiphyics软件,针对准噶尔盆地中部4区块某三维区致密储层不同开采时间下流体渗流速度和地层孔隙压力的分布规律开展了数值模拟研究。研究结果表明,流体渗流速度最大值出现在井口及其周围地区,断层破碎过渡带流体渗流速度高于周围连续地层和断层核部;随着与井口距离的增加,开采过程中流体渗流速度变化规律由先增加后减小最后趋于稳定逐步转化为先缓慢增加后逐步趋于稳定;在开采初期,孔隙压力等压线在井口周围呈环形分布,而后低应力区沿断层的开展方向进行扩展;孔隙压力随着开采时间的增加而不断减小,同时间节点下,距离井口越远,孔隙压力越大且下降幅度越小。研究成果为正确预测开发生产指标,为提高致密油气勘探开发效果提供技术支撑。Abstract: Seepage characteristics of tight sandstone are of great significance for tight reservoir evaluation and exploitation. The fluid-solid-heat coupling control equation was built, and the COMSOL Multiphyics software was used to carry out a numerical simulation study for the distribution law of fluid seepage velocity and formation pore pressure under different production time in a 3D tight reservoir in No.4 block of central Dzungaria Basin. The results are as follows:(1) The maximum values of fluid seepage velocity appeared in the wellhead and its surrounding areas, and the velocity of fluid seepage in the transition zone of fault breakage was higher than that in the surrounding continuous formation and nuclear part of the fault. (2) With the increase of the distance from the wellhead, the variation of fluid seepage velocity changed from increasing first, then decreasing, and finally tending to be stable to gradually increasing first, then gradually tending to be stable. (3) In the initial stage of production, the pore pressure isobar was located around the wellhead, distributed with circular line and then the low stress zone extended along the direction of the fault. (4) The pore pressure was decreasing as the production time increased, at the same time, the farther from the wellhead, the larger the pore pressure was and the smaller the decrease amplitude was. The research results provide technical support for the correct prediction of development and production indexes and improvement of exploration and development effect of tight oil and gas.
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Key words:
- multi-field coupling /
- tight reservoir /
- seepage characteristics /
- pore pressure
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表 1 计算参数表
Table 1. Table of calculation parameters
介质 密度/(kg/m3) 弹性模量/GPa 泊松比 热熔系数J/(kg·K) 热传导系数W/(m·K) 热膨胀系数/K 孔隙率 连续地层 2700 28 0.22 923 2.47 5.3×10-5 0.06 破碎过渡区 2100 16.8 0.314 923 2.61 6.2×10-5 0.35 断层核部 2800 28.8 0.21 923 2.45 5.2×10-5 0.03 液相 1070 — — 4200 随温度变化 2.08×10-4 — 表 2 最优化反演数据表
Table 2. Optimized inversion data sheet
边界荷载 反演最优值/MPa 边界荷载 反演最优值/MPa 边界荷载 反演最优值/MPa 边界荷载 反演最优值/MPa P1 149.47 P5 107.61 T1 93.93 T5 -89.08 P2 91.55 P6 123.66 T2 -64.19 T6 14.19 P3 77.72 P7 131.6 T3 58.59 T7 69.59 P4 138.54 P8 86.51 T4 -16.51 T8 22.67 -
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