强敏感性稠油油藏高温热变定量表征

Quantitative characterization of high-temperature thermal changes in highly sensitive heavy oil reservoirs

金家油田沙一段为具有强敏感性的稠油油藏,在蒸汽吞吐开发过程中,高温有效降低原油黏度,但同时也引起储层内部的一系列变化,对油藏开发产生影响。为了实现敏感性稠油油藏的有效开发,针对蒸汽吞吐过程中制约油藏开发的关键因素认识不清,高温储层变化缺乏定量表征和规律化认识等问题,开展一系列物理模拟实验研究。结果表明:(1)高温条件下,随温度升高,蒙脱石晶间距逐渐减少,超过200℃时蒙脱石膨胀性显著变弱;(2)高温条件下,随温度升高,溶蚀作用加剧,当温度超过150℃时,溶蚀使得储层孔径增大,孔隙结构改善,孔喉连通性变好,孔渗增大,渗透率增幅明显高于孔隙度增幅;(3)高温条件下,高温溶蚀也产生了大量骨架和黏土等溶蚀颗粒,溶蚀颗粒中的大量黏土降低沥青沉淀点,引起原油中沥青质的析出,颗粒与沥青结合,形成油泥沉淀,在近井地带造成堵塞,引起油井供液不足,这是金家油田沙一段稠油油藏蒸汽吞吐开发的关键制约因素。以上成果认识,对具有水敏性、地层出砂的稠油油藏开发因素分析及开发对策制定具有一定的指导意义。

The first member of Shahejie Formation of Jinjia Oilfield is a highly sensitive heavy oil reservoir.During the steam stimulation development process,high temperature effectively reduces the viscosity of crude oil,but at the same time it also causes a series of changes in the reservoir,which has an impact on the development of the reservoir.In order to realize the effective development of sensitive heavy oil reservoirs,a series of physical simulation experiments were carried out to solve the problems of unclear understanding of the key factors restricting reservoir development during the steam stimulation process,lack of quantitative characterization and regular understanding of high-temperature reservoir changes.The results show that:(1)Under high temperature conditions,with the increase of temperature,the montmorillonite crystal spacing gradually decreases,and when the temperature exceeds 200℃,the swelling property of montmorillonite becomes significantly weaker;(2)Under high temperature conditions,the dissolution is intensified with the increase of temperature,when the temperature exceeds 150℃,dissolution will increase the pore size of the reservoir,improve the pore structure,improve the pore throat connectivity,increase the porosity,and increase the permeability significantly higher than the increase of porosity;(3)Under high temperature conditions,high-temperature dissolution also produces a large number of corroded particles such as framework and clay.The large amount of clay in the corroded particles reduces the precipitation point of asphalt and causes the precipitation of asphaltenes in crude oil.Insufficient liquid supply is a key restricting factor for the development of steam stimulation in heavy oil reservoirs in the first member of Shahejie Formation in Jinjia Oilfield.The above understanding of the results has certain guiding significance for the analysis of development factors and the formulation of development strategies for heavy oil reservoirs with water sensitivity and sand production.