微泡钻井液流变性

Rheological properties of Aphron based drilling fluids

鉴于微泡钻井液在衰竭油气藏钻井中的成功应用,通过实验测试和数据分析研究了微泡钻井液的流变性及稳定性。配制了一种典型的微泡钻井液,在不同温度下对其黏度进行测试,分别采用幂律模型、宾汉塑性模型和Herschel-Bulkley模型对测试数据进行了拟合,发现Herschel-Bulkley模型更能准确描述不同温度下微泡形成前后钻井液的流变性。根据Herschel-Bulkley模型拟合结果,温度升高会提高微泡钻井液的剪切稀释程度,微泡形成后钻井液的静切力和井眼净化能力提高,且在高温下微泡钻井液性能不会明显减弱。低剪切速率下微泡钻井液具有较高的黏度,可以保证良好的孔隙堵塞效果。微泡尺寸增长速率及静态析出实验中液体析出速率可作为评价微泡稳定性的指标:微泡尺寸随时间增加增长缓慢且寿命较长,静态析出实验中液体析出速率低,说明微泡钻井液具有良好的稳定性。

A new drilling fluid system has been successfully used to drill depleted reservoirs which are known as Aphron based drilling fluids. The rheological behavior of the Aphron based drilling fluid was investigated by experimental tests and data analyses. After generating a typical Aphron based drilling fluid, its viscosity was tested at different temperatures, and the test data was fitted using Power law, Bingham Plastic and Herschel-Bulkley models. It is found that Herschel-Bulkley model is more accurate to describe flow properties for fluids before and after Aphron generation process for all temperatures. Based on Herschel Bulkley model, the shear thinning ability of the fluid increases by increasing temperature, the gel strength and hole cleaning capacity of the fluid increase after Aphron generation, and increasing temperature to high value will not debilitate Aphron drilling fluid performance significantly. The fluid has high viscosity in low shear rate conditions, so that it can provide a strong seal in pore openings to bridge the pores. Aphron bubble growth rate over the time and drainage rates are determined as criteria for Aphron bubble stability. Bubble size growth rate is very low and the longevity is long, and liquid drains in a weak rate in drainage static test, which shows a strong stability of the Aphron based drilling fluid.