A new method for establishing regional formation pressure profile based on drilled wells data

Key words:  drilling  regional formation pressure  formation pressure matrix  formation pressure profile  depth adjustment method  spatial interpolation

Abstract:

Formation pressure is the basic data needed in drilling engineering design and operation during the exploration and development of oil and gas fields. To improve the prediction of formation pressure in a new exploration region, a method for the construction of formation pressure matrix was proposed, which was based on the effective stress theory and Eaton method. The formation pressure profile or the pressure along the wellbore with some uncertainties can be calculated according to the formation pressure matrix. A transplantation method calculating the formation pressure of the targeted wells in the region was given combining with depth adjustment and arithmetically modified distance weighting methods. Case studies were carried out to verify the method, in which the predicted formation pressure was compared with that derived from the well logging. The results show that the maximum relative errors are within 3.43%. The accuracy of the transplantation method is affected by the pressure data of the drilled wells nearby and their locations, and the spatial continuity of the formation in the targeted region. For a region with complicated geological structures, its geological characteristics need to be fully understood and analyzed, and care should be taken in using the formation pressure matrix and the transplantation method for the prediction of the formation pressure of targeted wells.