高温高压下可循环微泡沫钻井液管路流动试验

Flow experiment of circulative micro-foam drilling fluid in pipe under HTHP condition

以往对可循环微泡沫钻井液在铅直管路中的压力梯度或压差及有关参数等问题进行的研究中 ,由于所使用的试验装置 (有机玻璃管路 )多数耐压和耐温能力有限 ,不能模拟高温高压条件下气液两相流体的流动型态和流动规律。本文使用一套高温高压流动试验装置对可循环微泡沫钻井液在井筒条件下密度的变化规律、微泡沫钻井液在井底的实际发泡能力和空隙率的变化规律进行了研究。利用可循环微泡沫钻井液的流动试验数据和关系曲线 ,应用回归分析方法 ,得出了各温度下钻井液密度与压力的计算表达式 ,这些表达式均为一元二次多项式 ,每一多项式中的系数又为温度的函数。结果表明 ,微泡沫钻井液的密度随压力的增大而增大 ,随温度的升高而减小 ,但在井眼条件下密度随压力增大的速率要大于随温度减小的速率 ;微泡沫钻井液流过钻头喷嘴后 ,密度减小 ,泡沫更细小 ;微泡沫钻井液的空隙率随压力的增大逐渐减小 。

The vertical pipe equipment was often used in studying on the pressure gradient and differential pressure of circulative micro foam drilling fluid. However, the equipment in which lucite tube was used can not simulate flow states and indicate flow law of the fluids under HTHP condition because the bearings of pressure and high temperature of the lucite tube were limited. A new flow experiment equipment which can be used at HTHP to simulate the density changing law in holebore condition, actual foaming ability and the void factor of circulative micro foam drilling fluid was presented. According to the experimental data and relation curve, mathematical expressions about drilling fluid density and pressure in different temperature were obtained. These expressions are all quadratic polynomial in one element and the coefficients of the expressions are functions of temperature. Experimental results revealed that the density of micro foam drilling fluid increases with the increasing of the pressure and decreases with the increasing of the temperature, but in holebore condition, the incremental rate of the density with the increasing of the pressure is larger than that with the decreasing of the temperature; flowing through the bit port, the density of micro foam drilling fluid will decrease and its foam will become more fine; the void factor of micro foam drilling fluid tapers with increasing of the pressure and increases with the increasing of the temperature.