Evaluation of Polyurethanes as Potential Mud Loss Control Agents

In this article, polyurethanes have been selected as potential lost circulation materials (LCMs) that will be introduced in wellbores having experienced serious drilling mud losses. The chemicals will be mixed at surface, pumped downhole, let to bridge/foam and seal open fractures/channels.

Different tests have been carried out to investigate better ways of mixing and handling polyurethanes before pumping. In that, prospects of slowing down polyurethane reactions by decreasing the amount of activator and adding different proportions of diesel were investigated. Testing the effect of moisture on polyurethanes also was tested. Furthermore, testing using diesel, toluene, xylene, Musol, acetone, glycol, light crude oil, Safrasol as carrier fluids was undertaken. The mixing sequence of diluents and polyurethanes also was thought of and the effect of mixing water on foaming reaction also was investigated.

Placement under pressure of pumped polyurethanes also was investigated. It was revealed that pressure enhances polyurethane sealing capability. Adhesion and sealability experiments, in open fractures with apertures of 0.5 mm and 1.5 mm, also indicated that tested polyurethanes are the best candidates guaranteeing a good spreadability within open fractures. Bridging and sealing fracture apertures of up to 5 mm have been achieved with success. Sealability of even larger fracture apertures amounting to 2 inches also has been accomplished.

Keywords:

• mud loss
• lost circulation material
• polyurethanes
• fractures

Acknowledgments

The authors thank PDO (Petroleum Development Oman) for supporting this project through CTR (CR/ENG/PMRE/00/08) and Mr. Peter deMestre, the project's focal point, for his valuable contribution.

Notes

^a Polyurethane A + 5% activator.

^b Polyurethane B + 5% activator.

^c 50:50 mixture of polyurethanes A and B + 5% activator.