深盆气高孔渗富气区块成因机理物理模拟实验与解析

PHYSICAL SIMULATION EXPERIMENT AND EXPLANATION OF GAS ACCUMULATION MECHANISM IN THE DEEP BASIN GAS ACCUMULATION REGION AND ITS HIGH-PERMEABILITY SAND BLOCK

实验表明,深盆气及其富气区块的压力并非一成不变,而是随着地质条件(供气强度和供气量)的变化呈周期性变化。深盆气富气区块与周边的致密砂体在深盆气的建设阶段各形成两套独立的正压(高于静水压力)压力系统,这是由于两者之间存在孔渗性差异。在深盆气的消亡阶段,两者压力均降低,直到负压(低于静水压力)并逐渐归一,其演变特征类似于正弦曲线。负压不是深盆气的基本特征,而只是深盆气形成演化过程中消亡阶段的一个特点。深盆气富气区块形成演化要经历深盆气初期充注阶段、临界接触时刻、"甜点"充气阶段、两气相连时刻、气藏扩展阶段和调整共溶阶段共6个阶段。控制深盆气富气区块成藏机理的动力是气体膨胀力、毛细管力和浮力,它们在深盆气富气区块成藏过程的不同阶段具有不同的表现和控制作用。从而建立了实验条件下较完整的深盆气富气区块成藏序列及成因机理模式。

Physical simulation experiment indicates that, pressure of the deep basin gas accumulation and its high-permeability gas-rich zone are not invariable, but change periodically with the geologic conditions (gas providing intensity and quantity). During the construction period of deep basin gas accumulation, the high-permeability gas-rich zone of deep basin gas accumulation and the compact sand body around form 2 independent positive pressure systems respectively, due to the permeability difference between them. During the dispersing period of deep basin gas accumulation, both pressure system decrease to negative pressure state and become an united pressure system. The evolution is of the characteristics of sinusoidal curve. Negative pressure is not the basic charateristic of deep basin gas accumulation, but one characteristic of the dispersing period during the formation and evolution of deep basin gas accumulation. The formation and evolution of deep basin gas accumulation experience 6 stages: gas entrance, critical touching time, 'dessert' fornning, connection of 2 gases, expansion of gas accumulation, and adjust-mix. The controlling forces include gas expanding force, capillary pressure and buoyancy, which play different roles during different stages. Thus, relatively complete accumulation succession and mechanism model of deep basin gas accumulation and its high-permeability gas-rich zone under physical laboratory condition are established.