Knowledge of formation rock properties, in-situ stress direction, and stress magnitudes are valuable aids to the successful drilling, completion and stimulation of oil and gas wells. These factors are of even greater importance for horizontal or highly deviated wells. Problems such as wellbore collapse, breakout, and breakdown during drilling and completion can be minimized by using knowledge of in-situ stress direction and magnitude to optimize wellbore direction and/or mud weight. Knowing the azimuth of hydraulic fractures will be of great benefit on any producing or injection well. For horizontal or highly deviated boreholes, this information may be required to avoid premature screenout and unexpectedly high treating pressures if the well is fracture stimulated. These problems can be addressed with improved mud weight control during drilling and stimulation treatment designs based on knowledge of the stress magnitudes, the direction of the principal stresses, and the formation's mechanical properties.
A downhole extensometer tool has been developed (jointly by TOTAL and Halliburton) and field tested that will monitor borehole deformation responses to pressuring before, during, and after a microfracture stress test.
The borehole strain measurements before and after fracture initiation are used to determine the following parameters:
Minimum in-situ stress magnitude (closure pressure)
Width of induced fracture
In-situ shear modulus