Wang Lan, Lu Ting, Li Zhiping, Guo Xiao
Southwest Petroleum University, Chengdu 610500, Sichuan, People's Republic of China.
Shaanxi Key Laboratory of Carbon Dioxide Sequestration and Enhanced Oil Recovery, Xian 710000, Shaanxi, People's Republic of China.
ACS Omega. 2024 Jun 28;9(28):30159-30168. doi: 10.1021/acsomega.3c09738. eCollection 2024 Jul 16.
The dissolution of elemental sulfur in acidic gas leads to its precipitation as gas pressure decreases, thereby causing potential damage to the formation due to the deposition of sulfur particles. Previous sulfur deposition prediction models often relied on the solubility of sulfur in acidic gas and the stress state of sulfur particles to determine the occurrence of deposition, thus establishing predictive models. However, in the presence of complex geological conditions, the multiphase flow through porous media and the adsorption of particles on pore throat walls can also influence sulfur particle deposition to some degree. It is well known that sulfur particle deposition during gas reservoir development exhibits instability, with multiple factors influencing the deposited sulfur particles. Particularly noteworthy is the influence of airflow velocity, which can resuspend sulfur particles that are physically adsorbed on pore throat surfaces, thereby reintegrating them into the gas phase. Additionally, the dynamic deposition of larger sulfur particles involves a dynamic process. This study elucidates the dynamic process of sulfur deposition by considering the diverse transport dynamics of sulfur particles. Physical adsorption and desorption behaviors of sulfur particles are determined based on variations in reservoir conditions. The desorption status of sulfur particles with different particle sizes within the formation is established by evaluating the equilibrium between the force exerted on the pore throat wall and the suspension force generated by gas flow. The critical conditions for sulfur deposition in Yuanba gas reservoir were obtained by substituting on-site parameters into calculations. Moreover, a mathematical model is proposed to describe the dynamic deposition and migration of sulfur particles, adopting principles from continuous porous media porous flow theory, fluid flow mass conservation, as well as sulfur particle desorption and migration. The formulated model is solved, and its resulting solution process and outcomes hold significant implications for numerical simulation and predictive assessment of the development impact on gas reservoirs, particularly in later stages.
元素硫在酸性气体中的溶解会随着气体压力降低而导致其沉淀，从而因硫颗粒的沉积对地层造成潜在损害。以往的硫沉积预测模型通常依靠硫在酸性气体中的溶解度以及硫颗粒的应力状态来确定沉积的发生，进而建立预测模型。然而，在复杂地质条件下，多相流体通过多孔介质以及颗粒在孔喉壁上的吸附也会在一定程度上影响硫颗粒的沉积。众所周知，气藏开发过程中的硫颗粒沉积具有不稳定性，多种因素会影响沉积的硫颗粒。特别值得注意的是气流速度的影响，它会使物理吸附在孔喉表面的硫颗粒重新悬浮，从而使其重新进入气相。此外，较大硫颗粒的动态沉积涉及一个动态过程。本研究通过考虑硫颗粒多样的输运动力学来阐明硫沉积的动态过程。基于储层条件的变化确定硫颗粒的物理吸附和解吸行为。通过评估作用在孔喉壁上的力与气流产生的悬浮力之间的平衡，确定地层内不同粒径硫颗粒的解吸状态。将现场参数代入计算，得到了元坝气藏硫沉积的临界条件。此外，提出了一个数学模型来描述硫颗粒的动态沉积和运移，该模型采用了连续多孔介质渗流理论、流体流动质量守恒以及硫颗粒解吸和运移的原理。对所建立的模型进行求解，其求解过程和结果对气藏开发影响的数值模拟和预测评估具有重要意义，尤其是在后期阶段。
