泡沫钻井液动密度随井深变化关系模拟研究

Simulation Study on How the Density of Foam Drilling Fluid Varies with Well Depth

提出了测定泡沫钻井液动密度与压力、温度关系的方法,根据现场实测温度、压力与井深的关系,测定和分析了泡沫钻井液密度随压力、温度的变化关系。结果表明,相同压力下泡沫钻井液动密度随温度的升高而降低;同一温度下随压力的升高,泡沫钻井液密度快速升高,大于一定压力后密度增加缓慢。泡沫钻井液动密度随井深的变化趋势可以分为三段:低压快速上升段、中间弯曲段和高压高温下降段。由于气泡内及气泡表面的各种力的综合影响,井深大于一定值后,温度升高引起的体积膨胀稍大于压力升高引起的体积缩小,泡沫钻井液的动密度会稍有下降,并且动密度始终是小于1.0kg／L的,能够满足现场欠平衡钻井的要求。

A method has been set up to measure the relation of the dynamic density of foam drilling fluid with temperature and pressure. The dynamic density of foam drilling fluid is measured and analyzed under different temperatures and pressures according to the data of the temperatures and pressures measured in the oilfield. The results indicate that the dynamic density of foam drilling fluid reduces with the rising of temperature under same pressure, and under the same temperature it increases quickly with the rising of pressure at the beginning and then increases slowly with the rising of pressure after a certain pressure. The varying trend of the dynamic density of foam drilling fluid can be divided into three sections: increasing rapidly in the low-pressure section, curving in the middle section, and decreasing in the high-temperature and high-pressure section. The volume expansion with the increase of temperature is a little stronger than the volume deflation with the increase of pressure below a certain well depth under the integrated influences of all kinds of forces in the bubbles and the surface of the bubbles. As a result, the dynamic density of foam drilling fluid will decrease slowly. So the dynamic density of foam drilling fluid can be kept less than 1. Okg/L during the drilling operation, which can reach the demands for the underbalanced drilling operations.