深层-超深层异常高压油藏工艺技术对策

Technological strategies for deep and ultra-deep reservoirs with abnormally high pressure

深层-超深层油藏地层压力高,开发过程中参数控制不合理易导致油井出砂、套损和结胶堵塞,确定合理的生产压差是油藏能否有效动用的关键。以永进油田为例,通过前期试油试采分析,认为生产压差控制不当、沥青质析出沉淀认识不足是导致该油田多年无法经济动用的关键。运用成熟软件重新进行了出砂预测,开展了井筒压力计算,以寻求合理的工作制度。实验研究了沥青质析出沉淀的原因和防治方法,结果表明,研究区地层临界生产压差为34.9 MPa,前期试油、试采射孔及生产时,压差均超过临界生产压差导致出砂;原油体系不稳定,结胶指数为2.33,井筒压力低于沥青质稳定压力,导致沥青质析出沉淀堵塞,分析认为这是早期开发效果差的主要原因。据此确定了从打开油气层开始,采取全过程压力控制的开发策略。当地层压力较高时,合理控制压力生产,可同时解决出砂和沥青质析出沉淀问题;当压力下降后,添加沥青分散剂辅助生产。矿场采取上述工艺技术试验了2口井,均取得成功。

The deep and ultra-deep reservoirs have high formation pressure,and the unreasonable parameter control during the development process can easily lead to sanding,casing damage,and cement plugging in oil wells.Determining a reasonable production pressure drop is the key to the effective use of the reservoir.Taking Yongjin Oilfield as an example,through preliminary oil test and trial production analysis,it is believed that improper production pressure drop control and inadequate understanding of asphaltene precipitation are the key factors that have prevented the oilfield from being developed economically for years.Mature software is used for sand production prediction,and wellbore pressure calculation is carried out,in order to seek a reasonable working system.The reason and prevention method of asphaltene precipitation are studied by experimental methods.The results show that the critical production pressure drop of the formation in the study area is 34.9 MPa.During the preliminary oil test,trial production perforation and production,the pressure drop exceeded the critical production pressure drop and resulted in sand production.The crude oil system is unstable,and the CI value is 2.33.The wellbore pressure is lower than the asphaltene stable pressure,which leads to asphaltene precipitation and plugging.The analysis shows that this is the main reason for the poor early development effect.Based on this,the development strategy for the whole process of pressure control is determined from the opening of the oil and gas layer.When the formation pressure is high,the reasonable pressure controlled production can solve the problems of sand production and asphaltene precipitation.When the pressure drops,asphalt dispersant is added to assist production.Two wells have been tested and all have been successful.