水平井井筒内滤液侵入地层的模型评价

Setting-up a Model to Evaluate the Invasion of Drilling Fluid Filtrate to the Formations in Horizontal Wells

水平井钻井过程中,有时会由于钻井滤液侵入地层引起的伤害导致产能下降。建立了一种流体滤失模型,评价了水平井井筒内流体的移动情况。该模型可以模拟在静态或动态滤失期间含水滤液通过含油地层的径向流情况,在有泥饼和无泥饼条件下钻井液污染对渗透率的下降影响不大,但对滤失量却有一定影响,无泥饼的滤失量比有泥饼的滤失量大些;通过将水平井段的每个部分作为调查的节点并沿着每个节点单独输入地层参数,该模型能用来预测非均质储层沿着井眼的滤液侵入和污染情况,该模型对改善水平井流体滤液特性和评估滤液对地层的伤害提供了一种方法。给出了算例,计算了大港油田一口水平井的伤害半径、伤害渗透率和表皮系数。

The invasion of the drilling fluid filtrates to the formations in horizontal wells imposes great damage to the productivity of the reservoirs. A model was established for fluid filtration to evaluate the flow of the fluid in a horizontal hole. The filtration of the fluid is dynamic: the mud cake is damaged after the filtrate goes into the formation. With the thickness of the mud cakes being determined, the relation between filtration rate and time can be established and this, combined with the relative permeability curves and the effective permeability distribution, led to the conclusion that the filtration rate of muds is higher when mud cakes exist than that of muds when mud cakes vanish. The conclusion offered a good way of improving the filtrate properties and evaluating the impairment caused by the filtrates.