ANALYSIS OF WELLBORE STABILITY OF SHALE GAS RESERVOIR DRILLING

摘要

Aiming at Posidonia shale well wall stability analysis problem in certain domestic oil filed, the Paper carries out test analysis by utilizing stress distribution and it is shown by experiment that: (1) when composite surface surfactant coordinates with water-based drilling fluid, it can effectively impede and postpone transmission of shale pore pressure and reduce shale permeability to increase shale well wall stability; (2) mechanical analysis model of horizontal well wall stability with bedding surface shale gas reservoirs has been established based on well wall stability pore elastic mechanics and single-structure surface strength theory and the model has considered the influence of shale layer bedding surface occurrence (direction and dip angle) and influence of weakening of bedding surface strength based on classic pore elasticity well wall stability model and the model can effectively guide optical design of horizontal well borehole drilling direction and drilling fluid density; (3) well wall structure type is an important factor to influence well wall stability and advantageous shale structure is a main factor to influence single well wall stability in practical drilling. Foresaid experiment result has certain guidance meaning for practical drilling process.