为了研究多压力系统合采生产特征，以叠置含气系统这一特殊气藏模式为工程背景，利用自主研发的多场耦合叠置含气系统煤层气开采物理模拟试验系统开展了常规合采、定压合采和定产合采3种模式的物理模拟试验研究，探讨了不同合采模式下叠置含气系统煤层气开采产气特征及其流体流动规律，阐述了多压力系统煤层气合采过程中的流体扰动效应机制。结果表明:① 对井筒出口施加限定条件，较低初始能量煤储层易遭受压力扰动，导致近井地带出现压力上升的现象，但该压力扰动主要存在合采初期阶段，而后逐渐消弱;② 压力扰动会改变煤储层内势能的空间分布形态，尤其是初始流体能量较低的煤储层，即在近井地带形成一个高势带，导致煤储层内流体在高势带的影响下而改变其原有的流动特征;③ 定压合采会致使压力存在差异的各个煤储层与井筒之间形成一种“动态压力平衡”关系，在压力势能的作用下，来自高初始流体能量煤储层的流体向低初始流体能量煤储层流动，而定产合采将整个合采过程划分为稳产期和衰减期，在稳产期内，各煤储层的产气能力在井口定产的作用下重新分配，形成一种“动态分配”产气模式，即当流体能量高的煤储层产气能力超越定产值时，部分来自初始流体能量高煤储层的流体向初始流体能量低煤储层反向注入，加剧合采流体扰动效应。

In order to study the production characteristics of multi-pressure system under coalbed methane (CBM) coproduction based on the special gas reservoir model of superposed gas-bearing systems,three groups of CBM coproduction tests of conventional,constant wellbore pressure and constant gas production rate were conducted using the self-developed physical simulation test system of multi-field coupling testing system for CBM exploitation.The gas production characteristics and fluid flow characteristics of superposed gas-bearing system under different CBM coproduction modes were expounded,and the mechanism of fluid disturbance effect in the process of CBM coproduction were revealed.Research results obtained are as follows:① It is easy for the coal reservoir with low initial fluid energy to suffer from pressure disturbance by limiting the wellbore outlet,which leads to pressure rise near the wellbore.However,the pressure disturbance mainly exists in the initial stage of CBM coproduction and weakens with time.② The pressure disturbance will change the spatial distribution of potential energy in the coal reservoir,especially in the coal reservoir with low initial fluid energy,that is,a high potential zone will be formed near the well which changes the original flow characteristics of the fluid.③ The CBM coproduction with constant wellbore pressure will result in a “dynamic pressure balance” relationship between each coal reservoir with different pressures,and a part of gas from the coal reservoir with high initial fluid energy to the gas-bearing system with low initial fluid energy.The whole process of CBM coproduction with constant-rate can be divided into stable production period and decline production period.The gas production capacity of each coal reservoir is redistributed under the effect of constant-rate during the stable production period,and a “dynamic distribution balance” gas production mode is formed.That is,when the gas production capacity of the coal reservoir with high fluid energy exceeds the constant-rate,a part of the fluid from the coal reservoir with high initial fluid energy is injected into the coal reservoir with low initial fluid energy in the reverse direction,which aggravates the fluid disturbance effect.

1 试验装置及方法

   1.1 试验装置

   1.2 试验步骤及方案

2 试验结果

   2.1 产气动态演化规律

   2.2 套压动态演化规律

   2.3 储层压力动态演化规律

3 讨论

   3.1 合采产气特征

   3.2 煤层气流动特征

   3.3 合采流体扰动机制

4 结论