Wireline and While-drilling Formation-tester Sampling with Oval, Focused, and Conventional Probe Types in the Presence of Water- and Oil-base Mud-filtrate Invasion in Deviated Wells
Author: Abdolhamid Hadibeik Nishaboori
Publisher:
Published: 2009
Total Pages:
ISBN-13:
DOWNLOAD EBOOKSpeculation about the potential of developing new fluid sampling methods with probe-type formation testers has existed since the introduction of formation pressure testing to the drilling environment in 2002. Extending the existing wireline technology requires a new pumping system capable of removing invasion fluids and then filling single-phase sample chambers. Several technological advances are necessary before these conditions are commercially possible. Although wireline pumpout tools may require hours to retrieve representative fluid samples, spending hours obtaining samples in the drilling environment may not be considered a practical alternative. The objective of this thesis is to quantify the viability of sampling in the drilling environment by way of numerical simulations. The study considers the dynamic nature of invasion while drilling when using both new and conventional probe configurations to retrieve fluid samples. Previous studies assumed a time-constant rate of invasion that was close to that of the final stages of invasion. Furthermore, most simulations of wireline formation-tester measurements assumed that invasion ended at the time when fluid pumpout began. Both of these assumptions are optimistic for a drilling tool. To realistically simulate invasion during drilling, a mudcake model is used that continues to grow in thickness and sealing effectiveness during invasion and throughout the sampling process. Simulation results focus on scenarios in which water-base mud (WBM) and oil-base mud (OBM) invade an oil-bearing zone. In addition, the accuracy of functions used to estimate contamination is studied in an OBM environment. The base model consists of a typical probe-type tool in a vertical well wherein fluid samples are retrieved using a time-constant flow rate. Invasion time is varied from 1 hour to 48 hours to compare drilling and wireline sampling tools. We quantify mudcake sealing effectiveness, as well as the effect of borehole deviation. Oval (elongated) and focusing guard-style probes are compared to standard probe configurations for various petrophysical rock types. Simulations of fluid cleanup times for a variety of rock types and wellbore deviation angles indicate that the oval focused probe retrieves the cleanest fluid sample in the shortest period of time.