Formation pressure and mobility testing while drilling has over the last two years evolved from being a newcomer to a mature member of the Logging While Drilling (LWD technology family. Formation pressure data have always been one of the main parameters in reservoir management. The introduction of a reliable LWD formation pressure tester which allows acquiring these data while drilling has opened up a number of new applications. Traditionally, these data have been acquired with wireline formation testers, upon reaching section or well TD. In high angle wells, this is a time-consuming operation, as the tools have to be conveyed by drill-pipe. Apart from the traditional applications of such data for gradient and fluid contact determination, real-time knowledge of pore pressure ultimately allow to optimize ECD management, increase ROP, and improve safety but also assess reservoir connectivity, optimize casing plans, and help in geosteering. The main challenges associated with acquiring formation pressure in real-time while drilling and how these challenges have been overcome will be discussed. The paper uses several case histories in a wide range of hole sizes (8 1/2 - 13 1/2") performed on offshore fields in the Norwegian Continental Shelf to review the major benefits acquiring and utilizing these data while drilling, considering different field specific applications. Having the formation pressure data available when drilling is advantageous; to the petrophysicist, reservoir engineer and the drilling engineer. The paper discusses in detail the benefits of these data to the different disciplines and also addresses the effects on overall safety and cost savings. In tight formations, pressure measurements may be affected by super-charging, leading to erroneous data unsuitable for gradient work or fluid contact identification. When acquiring pressure data with wireline tools several days after the formation has been drilled, one can only assume that there is little influence from super-charging. However, with this LWD tool, time lapse pressure measurements are now possible in suspect zones, which are readily identifiable by the mobility values derived in real-time. Thus, the same formation can be tested minutes after having been drilled and then again when the BHA is being pulled, be it for a bit change or upon reaching section TD. The paper illustrates the progress that has been made in the understanding of this phenomenon with the help of time lapse pressure data."
LWD Pressure and Mobility Measurements in Challenging Environments
Gravem, Trond, Normann, Hans Petter, Halvorsen, Christian, Buysch, Arno, and Cato Daykin. "LWD Pressure and Mobility Measurements in Challenging Environments." Paper presented at the SPWLA 46th Annual Logging Symposium, New Orleans, Louisiana, June 2005.
Download citation file: