关键词: 双台阶水平井, 不稳定渗流, 耦合, 产能指数

Abstract:

Abstract：The study of percolation theory and deliverability analysis for two-stepped horizontal well is imperfect at home and
abroad. Based on the horizontal well unstable flow model and the potential superposition principle，the two-stepped horizontal
well unstable flow model is established by using a semi-analytical method and by considering the variable mass flow within the
wellbore pressure loss，the solution of the coupling model is presented under the bottomhole constant pressure. The research
results of the real examples show that the productivity index distribution along the borehole is non-uniform，which is the
asymmetric“U”shaped pattern. The productivity index at the heel is slightly higher than that at the toe. There is an obvious step
on the curve of pressure difference distribution along the wellbore，which shows that the pressure loss at the connection section
is larger. The results are meaningful and provide a theoretical basis for the two-stepped horizontal well casing design，and for
designing the field development project，computing development indicators，formulating development adjustment programs，
and therefore，to efficiently develop the complex oil and gas fields.

Key words: Key words： two-stepped horizontal well, transient fluid flow, coupling model, productivity index