固井前地层漏失压力动态测试方法

A dynamic test method for the formation leakage pressure before cementing

准确评价地层漏失压力是低漏失压力井固井防漏施工设计的前提,但目前对漏失压力评价仍缺乏有效的理论计算和现场试验方法,导致固井防漏设计与施工缺乏定量依据。基于宾汉流体在套管与环空内流动的流变学原理,提出通过逐步提高循环排量,增加作用于目标层的动液柱压力实现地层漏失压力测试的方法。该方法根据实时循环立压,结合环空和套管的几何特征关系,可定量计算目标层动液柱压力;结合实时监控进出口钻井液排量,在发生微漏时停止测试,此时对应的动液柱压力即为地层漏失压力,或测试至满足固井防漏需要时停止。现场应用结果表明,该方法便于现场快速测定地层承压能力,为防漏固井设计优化与施工方案调整提供了数据支撑。

The accurate evaluation of formation leakage pressure is the prerequisite to the leak-proof cementing construction design of the wells with low leakage pressure. At present, however, there is no effective theoretical calculation and field test methods for evaluating leakage pressure, so no quantitative basis is available for leak-proof cementing design and construction. In this paper, a method for testing the formation leakage pressure by increasing the circulating displacement gradually to increase the dynamic liquid column pressure applied on the target layer was proposed according to the rheological principle of Bingham fluid flowing in casing and annulus. In this method, the dynamic liquid column pressure can be calculated quantitatively based on the real-time circulating pressure, combined with the geometric characteristic relationship of annulus and casing. By conducting real-time monitoring on the displacement of drilling fluid at the inlet and outlet, the test is stopped at the occurrence of micro-leakage. The corresponding dynamic liquid column at this moment is the formation leakage pressure. Otherwise, the test isn’t stopped until the leak-proof requirement of cementing is satisfied. The field application results show that this method is convenient for the on-site fast measurement of formation pressure-bearing capacity, so as to provide the data support for the optimization of leak-proof cementing design and the adjustment of construction scheme.