Cementing applications using a controlled mud level technology.

摘要

The petroleum industry has been making efforts since the 1990's to develop the dual gradient drilling technology. Currently, there are several available ways of achieving a dual gradient drilling, such as the Controlled Mud Level (CML). CML systems are capable of changing the bottom-hole pressure (BHP) by controlling the fluid level within riser. All mud returns are pumped though a subsea pump attached to the riser. Changes in the subsea pump rate will modify the height of the fluid column inside the riser, controlling then the BHP.;Most of the available papers demonstrate how the CML systems works. Nevertheless, they do not give many details about how the CML systems operate. A few other papers are focused mostly in drilling and well control operations. Even fewer papers have some discussions about the idea of using the CML systems to assist cementing operations, but none of them go further on the managed pressure cementing subject for CML systems. This work is the first to discuss in details how CML systems are a useful tool for managing the BHP while cementing.;A software has been developed to simulate how a cement job can be performed when a CML system is available. 35 different cases were simulated in order to study what are the advantages and disadvantages of using CML systems on managed pressure cementing. Those simulations were fun for wells with water depths reaching from 2,000 ft to 8,000 ft and operating windows as tight as 0.5 ppg. Results show that CML systems may eliminate the need for multiple stage cementing, improve mud displacement efficiency and deal with gas leakage situations after cement placement.