注天然气油井沥青质析出规律研究

目的 解决东河区块原油在注气开采过程中沥青质沉积堵塞井筒问题。方法 采用高温高压固相沉积规律测试装置，基于光散射理论，研究了温度、压力、气油比等因素对沥青质析出特征的影响。结果 温度升高会增加沥青质在原油中的溶解度，促进原油稳定；等温降压过程中，沥青质随着压力降低逐渐析出，在泡点压力附近达到最大析出量，发生沥青质沉积堵塞油井的风险最大。DH-1井泡点压力对应井深2 140 m,与油井生产实际遇阻位置1 969 m接近，泡点压力可初步用于预测油井堵塞位置；溶解注气量越大，沥青质初始析出压力越大，沥青质析出压力区间也增大，沥青质沉积位置向油井深度下移。结论 研究揭示了注气过程沥青质的析出规律，对注天然气油井沥青质析出防治具有重要指导作用。

Study on the precipitation regular of asphaltene in gas injection well

ObjectiveThis paper aims to solve the problem of asphaltene deposition blocking wellbore in the process of gas injection production of crude oil in Donghe block. MethodsBased on light scattering theories and using a high pressure/high temperature solid deposition test device, the effects of temperature, pressure, gas-oil ratio and other factors on the precipitation behavior of asphaltenes were tested. ResultsTemperature increase improves the solubility of the asphaltene in the crude oil and promotes the stability of the crude oil. Under isothermal pressure depletion conditions, asphaltenes gradually precipitate and reach maximum precipitation near the bubble point pressure with the descend of pressure. In other words, the risk of asphaltene deposition is highest when near the bubble point pressure. The bubble point pressure of DH-1 well corresponds to the well depth of 2 140 m, which is close to the actual blocked position at 1 969 m in production well. Therefore, the bubble point pressure can be used to predict the plugging location in oil wells. The higher the amount of dissolved gas, the higher the onset asphaltene precipitation pressure, and thus the larger the asphaltene precipitation pressure range the more likely asphaltene deposits to occur in deeper well sections. ConclusionThe research reveals the asphaltene precipitation law during gas injection, which has an important guiding role in prevention and control of asphaltene precipitation in gas injection wells.