FORECASTING THE RISKS OF JAMMING TO EXCLUDE THE POSSIBILITY OF STITCHING THE TECHNICAL SYSTEM «PERFOBUR» WHILE DRILLING BRANCHED CHANNELS IN TERRIGENOUS RESERVOIRS

Abstract

The relevance of the research. One of the promising methods of secondary formation exposing is drilling of deep perforations by the «Perfobur» radial drilling system. This article discusses the issues of forecasting and preventing freeze-in of the technical system «Perfobur» due to bit stall in the intervals of incompetent rock. The bit stall in these intervals occur due to the elastoviscoplastic deformation of the perforation channel cross section. The aim of the research is to evaluate the risks of sticking of the technical system «Perfobur» due to bit stall during the tripping operations and to develop the measures to prevent them. Objects: deep perforation channel in the terrigenous reservoir of oil field in the Volga region, which is an alternation of mudstone, siltstone and sandstone. Methods: geomechanical modeling, numerical integration, variable module method. Results. The authors have determined the movement of the deep perforation channel walls in time for the terrigenous reservoir, which is an alternation of argillite, siltstone and sandstone and obtained the dependences of the elastoviscoplastic movement of the perforation channel walls with changes in inclination angle. The elasticviscoplastic displacement of the perforation channel upper wall, as a rule, considerably (by 1,5 or more times) exceeds the elastoviscoplastic displacement of the perforation channel side wall. Consequently, the elasticviscoplastic displacement of the perforation channel upper wall is the most dangerous and determining from the point of view of bit stall during the tripping operations. Based on the established criterion of the PDC bit stall (dangerous displacement of the wall is equal to 2 mm), it is determined that the most dangerous from the point of view of bit stall is the argillite deposit and the time of safe work is one hour. To reduce the risk of the bit stall of the technical system «Perfobur», it was proposed to use a new screw downhole motor PDM-49, as well as the stabilizers, expanders, calibrators, and colmatators in perforation to prevent the elimination of possible complications in the perforation channel.

Keywords

• technical system «perfobur»
• bottom hole assembly
• bit seizure
• elastoviscoplastic deformation of rock
• bottomhole formation zone
• drilling of branched radial perforation channels