论文部分内容阅读
以往的天然气水合物开采数值模拟研究大多集中于产能结果分析,鲜见关于降压开采过程中储层内部压力变化规律的研究.本文基于质量守恒、能量守恒和达西定律,建立了水合物降压开采气、水和水合物三相一维模型,并首次在模拟计算中引入压降半径公式,利用有限差分法,采用IMPES(隐式压力-显式饱和度)方法求解模型.文中对比研究了井口压力、温度、渗透率和水合物分解对储层内压力变化的影响,结果表明:降压开采水合物导致井口附近形成低温区,可能引起水结冰和水合物再生的现象;储层绝对渗透率越大,压降在储层内的传播越快,总产气量也越大;水合物分解引起得水气两相相对渗透率变化和分解产生的水气是影响储层内压降传播速度的主要因素.
The previous studies on numerical simulation of natural gas hydrate production focused on the analysis of productivity results and seldom studied the variation of pressure inside the reservoir during the step-down mining.Based on conservation of mass, conservation of energy and Darcy’s law, The three-phase and one-dimensional models of gas, water and hydrate were pressed open and the pressure drop radius formula was introduced into the simulation calculation for the first time, and the finite difference method was used to solve the model with IMPES (Implicit Pressure-Explicit Saturation) method. The effects of wellhead pressure, temperature, permeability and hydrate dissociation on the pressure change in the reservoir were studied. The results show that the hydrate formation at the lower pressure leads to the formation of a low temperature zone near the wellhead, which may lead to water icing and hydrate regeneration. The greater the absolute permeability is, the faster the pressure drop propagates in the reservoir and the higher the total gas production. The change of relative permeability of water and gas caused by the hydrate decomposition and the water vapor caused by the decomposition will affect the pressure drop in the reservoir The main factor in the speed of communication.