Research On The Clay-free And High-density Well Kill Fluid System

With the growing of the oil exploration technology, there exist varying complicated reservoir conditions in the process of the well killing construction of drilling and completion engineering. According to different situation to choose the reasonable well kill fluid formula, the reservoir can be protected effectively and the second damage can be avoided, ensuring the stable yield. Therefore, it is important to study the preparation of the clay-free or low clay content well kill fluid system.In this paper, a series of experiments have been done to test the sensitivity of rock core, including velocity sensitivity, water sensitivity, salt sensitivity, alkali sensitivity and acid sensitivity experiments. Based on the five sensitive experiments, the reservoir sensitivity is evaluated. Analyzing the situation of reservoir sensitivity, the base fluid of the well kill fluid is screened out. Through testing the permeability under different saline weighting agent, three kinds meeting the conditions are select out. Because the admixture has a certain extent effects on the performance of well kill fluid system, a lot of experiments for the admixture optimization are conducted, which includes clay stabilizer, gas layer protection agent, viscosifier and fluid loss agent and corrosion inhibitor. To analyze the performance of each type of additive in the three optimized base fluid, a large number of experiments are done, selecting out the most suitable additives for the base fluid of three projects. Then three kinds of well kill fluid formulas meeting the conditions are obtained. By the indoor experiment to simulate the reservoir environment, the performance of prepared well kill fluid is determined. Under high temperature high pressure analyzing the relationship between the velocity gradient and the shear stress of the fuild system, the rheological properties of three kinds of formulas is good. In addition, evaluating the filtration, sedimentation stability and corrosion resistance respectively, the well kill fluid system have all reached the requirements of the reservoir protection.Through the indoor experimental evaluation on three kinds of the formulas, the well kill fluid systems have good performance on stability, corrosion resistance and high temperature resistance. So these three well kill fluid formulas can meet the needs of the construction site.