For deep wells, the limitation and inefficiency of single artificial lifting method appears with increasing depth. Under some conditions, conventional single lifting method is difficult to satisfy the production requirements. Combined artificial-lift system integrates the features of two lifting techniques, and displays the advantages of both to resolve the issues which are impossible to handle with single lifting method.
In the view of lifting process principle and string structure, there are several ways to configure combined artificial-lift system. However, the design of combined consecutive lift is more complex than that of conventional single pump system. Because not only does it involve the distribution of pressure, temperature and viscosity of multiphase flowing in wellbore, but also includes intercoordination between these two pumps and respective working conditions.
In this paper, the design approach of combined lift method is established based on nodal analysis, with which intercoordination of both pumps drainage, dynamic adjustment of comprehensive parameters and setting depth interval optimization could be analyzed. All of these issues have never been considered and studied under the condition of single pump system. In Xinjiang oil field, combined lift method of sucker rod pump and injection pump has been successfully applied in wells where thin oil is doped into heavy oil to decrease the viscosity. It is shown that combined-type consecutive lifting method is feasible in field test.