稠油油藏多轮次吞吐阻流环的分布特征及突破开采技术

Distribution characteristics and breakthrough production technology of flow-restricted ring in multi-rounds huff-and-puff heavy oil reservoir

随着稠油油藏吞吐轮次的增加,原油黏度较小的组分被优先采出,近井带周围会形成高黏阻流环,储层渗流能力降低,导致周期产油量、周期产液量,周期气油比持续降低。为了弄清阻流环的形成机制及对渗流的影响,利用物理模拟和数值模拟方法,对不同周期稠油性质、渗流特征以及阻流环影响下的黏度场、温度场、压力场和饱和度场的变化特征进行研究。结果表明:多轮次吞吐后轻质组分被优先采出,重质组分留下,在近井带40~60 m处形成以沥青质、胶质等重质组分堆积为主的环状高黏阻流环;阻流环的宽度随着吞吐周期的增加而增大,阻流环会降低储层的渗流能力,影响了油藏中流场的分布特征,对远井区稠油的渗流起到遮挡作用,导致井间的原油难以有效动用;为了消除阻流环的不利影响,形成了基于阻流环分布的“前置降黏+高压搅动”“高效降黏+气体增能”2类释放产能促效引效开采技术。研究成果为多轮次吞吐稠油油藏持续高效开发提供实验支撑和理论依据。

With the increase of huff-and-puff rounds of heavy oil reservoir,components with low viscosity are preferentially extracted.High viscous flow-restricted ring is formed around near-wellbore zone,reducing reservoir permeability and causing continuous low level of cyclic oil production,cyclic fluid production and cyclic oil-vapor ratio.In order to understand the formation mechanism of flow-restricted ring and its influence on fluid flow,physical simulation and numerical simulation methods are used to study heavy oil property and flow characteristics,and variation characteristics of viscosity field,temperature field,pressure field and saturation field influenced by flow-restricted ring of different cycles.The results show that light components are recovered and heavy components are retented after multi-rounds huff-and-puff.In near-well zone with radius of 40~60 m,circular high-viscosity flow-restricted ring is formed,mainly composed of heavy components such as asphaltene and colloidal matter,and its width increases with the increase of huff-and-puff rounds.Flow-restricted ring reduces reservoir flow capacity and affects distribution characteristics of flow field in reservoir,shielding heavy oil flow in far-well area,consequently,causing difficult mobilization of interwell oil.In order to eliminate unfavorable effect of flow-restricted ring,2 kinds of productivity-released production technologies for efficiency promotion and improvement,“preposition-fluid viscosity reduction+high pressure agitation”and“high efficient viscosity reduction+gas energy increasing”,are developed based on“flow-restricted ring”distribution.The research provides experimental support and theoretical basis for continuous high-efficiency development of multi-rounds huff-and-puff heavy oil reservoirs.