千米桥潜山凝析气藏低密度水包油压井液研究

Low-density oil in water well-control fluid for buried hill gas condensate reservoir of Qianmiqiao Oilfield

大港油田千米桥潜山常压凝析气藏已进入中期开采阶段,由于使用的水基压井液密度均大于1.0g/cm3,洗井时经常有压井液漏失,对储集层损害严重,严重降低产能.室内岩心研究表明,在净压力作用下,储集层的压力敏感性较强,气体流速敏感性损害程度很弱,地层水损害程度中偏严重.在模拟储集层高温条件下,对现场使用的压井液损害储集层的情况进行评价,结果显示对渗透率小于10mD的气层渗透率的损害平均为53%,这主要是压井液的滤液进入岩心的细小孔喉引起水锁伤害所致.根据不同伤害机理理研制出一种效果较好的低密度(0.84～0.90g/cm3)水包油压井液,抗温168℃,抗水、油污染容量10%,渗透率恢复值平均为90.06%,最低在87.6%以上.

The condensate gas reservoir of Qianmiqiao, Dagang Oilfield, is buried deeper than 4000m in a middle development phase. The density of the water base control fluid is over 1.0g/cm3, and fluid leakage always occurs during well cleanup, which seriously damage the reservoir and decrease the productivity. The pressure sensitivity, velocity sensitivity and damage of water invasion are analyzed and evaluated by laboratory study. The results show that under net pressure, the pressure sensitivity of the reservoir cores is strong, the velocity sensitivity is weak and the water invasion damage is middle to strong. Under the modeling conditions of high temperature, the control fluid damage of the reservoir is evaluated. The results show that the average permeability damage is 53% for the gas layers with permeability lower than 10mD. According to the damage mechanism, a low density oil in water control fluid with density of 0. 84-0. 9g/cm3, heat resistance of 168℃. water/oil pollution capacity of 10%, is proposed. The average permeability recovery is 90. 06% , and the lowest is above 87. 6%.