Over the years, operators have used many different techniques in the attempt to solve lost circulation and underground flow problems. Recently, polymer additives and new sealing methods have been used to combat such problems. However, these additives and techniques require extensive preparation time because they must be incorporated into the mud system. While some of these systems can solve minor problems, most cannot solve severe problems associated with large underground flows, fractures, vugs, or channels in weak formations.

A new, reactive, water-based lost-circulation material (LCM) has been successful in treating lost circulation and underground flows. The success of jobs performed with this material depends on the job technique used and the material's reaction with the drilling mud. This LCM is designed to react with water-and oil-based muds as well as environmental muds. It can help stop loss of drilling and completion fluids. Additionally, it can help increase or restore the integrity of weak formations, extend casing-shoe points, and eliminate intermediate casing strings.

This LCM reacts with drilling mud to create a barrier at the face of the lost-circulation zone. The LCM develops a moldable consistency within approximately 30 seconds of reacting with the mud and forms a ductile, nonbrittle bridge against the opening of the fluid-loss zone. This bridge can conform to wellbore or near-wellbore fractures as they change shape be-cause it only minimally penetrates the formation matrix or fracture. In laboratory tests, the material penetrated samples less than 164 in.

This LCM has been successful in the Rio Nuevo, Sen, Fortuna Nacional, and Luna fields in southern Mexico, preventing the operator from having to plug and abandon the wells. Two case histories are presented in this paper.

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