ABSTRACT
A new kind of polymer muds, which is generally referred to as the amphionic polymer mud, has been applied to the two horizontal well driling for the first time in the Dagang Oilfield, located in east China. In this mud system, two amphionic polymers are usually used as the main additives, the one with high molecular weight is an inhibitive encapsuler and filtration control agent, and the other one with low molecular weight is a deflocculant. The amphionic polymer, just as its name, is defined as the polymer that both organic cations and anions simultaneously exist in their molecular chains.
The design criteria, formulations and properties of this mud system are discussed. As a case history, the field performance of this new polymer mud in the different sections of the second well (by name Guan H-l, a medium-radius horizontal well) is also given.
It was shown from the laboratory and field tests that the amphionic polymer mud not only has all the advantages of the polymer muds commonly used, but is able to overcome the disadvantages of those muds, indicated by its highly inhibitive character while maintaining excellent mud performances. For this reason, the major drilling problems for horizontal wells in the Dagang Oilfield, such as hole cleaning, wellbore stability, lubricity, lost circulation and formation damage, which were hardly solved by the use of other water-based muds, could be solved successfully by the use of the amphionic polymer mud at much lower cost than the oil-based mud.
