Real time estimation of measurement in annular pressure and their relationship with pore and fracture pressure profile

Abstract

The drilling industry still faces the challenge of acquiring accurate and viable precision of subsurface pressure data. To address this, drilling industry is keen to establish accurate and reliable measurement of pressure in wellbore and to estimate the pore pressure and fracture pressure profile with utmost precision. In any drilling operation, it is important to maintain the annulus pressure within the geo- pressure margins (collapse and pore pressure on one side and fracturing pressure on the other side) For safe and effective drilling operation, it is therefore important to employ a method of estimating pore and fracture pressure before drilling and to update these estimate as the well is drilled and new information is required. In this thesis, we describe the way to predict pressure in between the sensor points. For this purpose, we use three different methods to estimate pressure in between the sensor points. We then describe how to deal with the uncertainties in between the sensor points by interpolation methods thereby estimating pressure points. Finally, we show how to integrate these methods to better quantify the uncertainties in real time data. However there are some external factors that influence the estimation of downhole pressure. These are the actual temperature gradient along the well, the proportion of cuttings in suspension, the presence of gas in the drilling fluid, the variations of borehole size due to cuttings beds or hole enlargements. This thesis presents qualitative estimations of the influence of these factors on the pressure estimation accuracy. The proposed methodology in this thesis can help in reducing many drilling problems such as circulation loss, stuck pipe, and well collapse. As a result, the industry may save much non-productive time. In addition, well planners will have improved information to make critical decisions.