Collapse analysis and reasons investigate in Well Inyashe-2 Myanmar

Due to complex geological conditions, severe borehole instability in Block C2 Myanmar, reasons to borehole instability need be analyzed and investigated to control subsequent borehole wall instability in drilling. The exploratory well Inyashe-2 in Block C2 Myanmar encountered serious borehole collapse in ?311.1 mm hole section. The characteristics of well collapse and its instability reasons were investigated by analyzing and studying on logging data, caliper data, formation lithology, pressure traverse and drilling fluid performance. The reasons to borehole instability are thought to be the follows: first, the liquid head of drilling fluid in several well sections are lower than formation collapse pressure. Second, the sealing property of drilling fluid is not enough to prevent drilling fluid seep into the fracture formation, which results that rock strength decreases, collapse pressure increases, and borehole instability occurs.