钻井液对海相储层伤害及产能的影响

Effect of Drilling Fluid on Reservoir Damage and Productivity of Marine Reservoir

为系统研究钻井液污染对海相低渗气藏储层伤害,采用室内试验评价手段,选用目标储层天然岩心在精确模拟地层条件下,开展了钻井液污染实验分析,并量化了其对产能的影响。研究表明:钻井污染后,在相同驱替压差下,渗透率伤害率随原始渗透率的增加而减小,对于达到致密级别的岩心,渗透率几乎全部丧失;提高压差进一步加重了被污染岩心的渗透率伤害,钻井液伤害主要是通过复杂多级别粒径颗粒封堵而伤害大孔道,渗透率伤害率变化曲线以驱替压差0.6 MPa为分界线,0.6 MPa内提高驱替压差对储层伤害更严重,后期渗透率伤害率变化幅度总体较小;随驱替压差的增加,不同原始渗透率岩心的渗透率伤害率曲线的间距越来越小,曲线形态由较高渗透率的大弧度状逐渐过渡到较低渗透率的“类直线”状;目标储层钻井液污染对产能的影响程度在93%以上,为此,建议对于存在钻井液污染的海相低渗储层在未解堵前不要轻易开井生产。研究成果为海相低渗储层的开发提供了重要的技术支撑。

In order to systematically study the damage of drilling fluid pollution to marine low permeability gas reservoir,the laboratory test and evaluation method were adopted to carry out the experimental analysis of drilling fluid pollution by selecting the natural core of the target reservoir under the precise simulation of formation conditions,and the influence of drilling fluid pollution on productivity was quantified.The research shows that the damage rate of permeability decreases with the increase of original permeability under the same displacement differential pressure after drilling contamination,and almost all permeability is lost for cores reaching the tight grade.Increasing the differential pressure further aggravates the permeability damage of the contaminated core.The drilling fluid damage is mainly caused by the complex multi-grade particle size plugging,and the permeability damage is divided by the displacement differential pressure of 0.6 MPa.The reservoir damage is more serious when the displacement differential pressure is increased within 0.6 MPa,and the damage in the later period is generally small.With the increase of displacement differential pressure,the spacing of permeability damage rate curves of cores with different original permeability becomes smaller and smaller,and the curve shape gradually transitions from large radian of higher permeability to“straight line”shape of lower permeability.The impact of drilling fluid pollution on the productivity of the target reservoir is more than 93%.Therefore,it is suggested that the Marine low permeability reservoir with drilling fluid pollution should not be easily opened for production before plugging is removed.The research results provide important technical support for the development of Marine low permeability reservoir.