A dynamic test method for the formation leakage pressure before cementing

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.