抑制油井层间水窜的固井技术探析

Cementing Technology to Prevent Fluid Channeling of Production Well

油井存在油水互层时,油层和水层间具有良好的封隔效果是延长油井见水期的方法之一。X井位于新疆油田准噶尔盆地西北缘,其目的层石炭系地层裂缝发育、油水层交错且受边底水及注水井等因素的影响,油井完井投产后油井含水率上升快并形成水淹,油井产能迅速下降。为保证完井后水层和油层间的水泥石仍然具有良好的封隔效果,采用韧性膨胀防窜水泥浆体系进行固井。文章在室内测试了该水泥浆体系的密度、流变性和失水量等基本属性,并结合力学软件和室内试验,优化水泥石的力学参数。现场应用表明,该体系既能够确保油井的固井质量,同时又能满足完井施工后水泥石完整性和封隔性要求,具有良好的防窜性能,满足封隔油井层间水窜的要求。X井固井作业的成功为同类井确保完井后水泥石力学完整性提供借鉴。

When there are oil-water interlayers in oil wells,a good isolation effect between oil layer and water layer is one of the methods to extend the water seepage period of oil wells.Well X is located in the northwestern margin of Junggar basin in Xinjiang oilfield,with fracture development in Carboniferous strata of the target layer,oil-water interleaving,and affected by edge-bottom water and water injection well.After the production of oil well,the water content of oil well increases rapidly and water flooding occurs,and the productivity of oil well decreases rapidly.In order to ensure the cement stone between water zone and oil zone still has a good sealing effect after completion,a ductile expansion anti-channeling cement slurry system is adopted.In this paper,the basic properties of the cement slurry system,such as density,rheology and water loss,are tested in laboratory,and the mechanical parameters of cement set are optimized by combining mechanical software and laboratory tests.The system can not only ensure the cementing quality of production wells,but also meet the requirements of integrity and sealing of set-cement after fracturing.The success of cementing operation in Well X provides reference for similar wells to ensure mechanical integrity of set-cement after fracturing.Laboratory test results show that it takes less than 45 minutes for the cement slurry to increase its static gel value from 48 Pa to 240 Pa in a weightless environment in the well.At the same time,the test results of poisson's ratio,Young's modulus and other mechanical properties show good elasticity and toughness.The cement is protected and basically produces no water after fracturing and production.