Integrated Formation Evaluation Data Base Combining MWD and Real-Time Surface Measurements with Conventional Logging Data
A. Whittaker, R. Dowsett, E. Nigh, A. Brooks, J. MacPherson
Formation evaluation has traditionally involved collecting information density over protracted time periods from drilling data, mud logging, intermediate logs, cores, final logs, drill-stem tests, and other reports. After drilling was completed, information was still not complete. Log and core analyses and geochemical and paleontological evaluations required weeks or even months to be added to the data record. Thus, formation evaluation was rarely timely enough to influence exploration drilling decisions.
With measurement while drilling (MWD), a new source of quantitative data became available during the drilling process. Recently, several new sensors have been added to MWD systems, and traditional mud logging methods have been enhanced to provide correlative data sources and benchmark standards for the lithologic normalization of MWD data. These data can be integrated within a single well-site data base to provide effective formation evaluation while the drilling process continues. The data base may be so structured that later available data, such as wireline logs, can be input to confirm and refine real-time evaluations. Similarly, the data base may be primed with geophysical and geological prognoses prior to drilling. Several case histories show the effective real-time determination of true total and effective porosities, fluid saturations, and estimates of formation characteristics such as mineralogy and permeability. In each case, later wireline logs and/or fluid recovery results confirmed the real-time evaluations. Where departures between early and late data sets occur, the data variations result from changes in downhole conditions and can be used to enhance formation evaluation by adding a dynamic component.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.