Abstract

In the last decade, Formation Pressure While Drilling (FPWD) measurement has developed from an emerging technology to a ubiquitous technology in environments ranging from ultra-deep water to land operations, as it is recognized for its cost efficiency and data quality when applied correctly. In addition to traditional uses similar to those of wireline-conveyed formation testers for reservoir evaluation, specific FPWD applications enabling real-time decision making in the well-construction process, such as drilling optimization and geo-steering, are now heavily utilized.

Many still argue that acquisition via wireline-conveyed methods produce higher quality data for reservoir evaluation, but to compare the measurements acquired by both technologies, it is necessary to understand the physics and dynamics in which both measurements are acquired. While typically the dynamic nature of FPWD data acquisition is seen to be disadvantageous because of mud circulating effects and potentially incomplete mudcake formation, operational practices during acquisition can mitigate these effects and particularly enhance test interpretation. There are unique opportunities for better understanding of test response and formation characteristics that are only available if the data are acquired early in the drilling phase. Complementing these measurements later with wireline data or even a subsequent FPWD pass while pulling out of the hole normally provides very valuable time-lapse information.

During this decade we have learnt that applying the same FPWD procedure for all environments might not obtain data of the highest possible quality because there are many variables to consider from the application to the environment. Formation types, mobilities, compaction, circulation rates, and mud types must be carefully considered during both planning and execution stages. In practice, we encounter reservoirs with variable permeabilities, different lithologies, and mud systems that are not always adequate. Lessons gathered from various environment types and innovative methods of acquiring data will be presented to address the following concerns:

  • Formation damage and time-after-drilling implications

  • At-balance/underbalance conditions

  • Static and dynamic supercharging

  • Tight and unconsolidated formations

The solutions developed through a decade of global experience and lessons learnt provide to new and existing users detailed insight into how to optimize procedures to deliver high quality data in many environments, whilst avoiding potential issues with the aim of acquiring pressure and mobility measurements as close as possible to a true representation of the formation under evaluation.

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