Effective Method for Monitoring Oil Based Mud Contamination in Wireline Formation Testers Sampling
- W. Pineda (BP E&P) | F. Gozalpour (formerly BP E&P) | Mehdi Hagshenas (BP E&P)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 28-30 September, Houston, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2015. Society of Petroleum Engineers
- 7.2.1 Risk, Uncertainty and Risk Assessment, 4 Facilities Design, Construction and Operation, 4.3 Flow Assurance, 5.5.11 Formation Testing (e.g., Wireline, LWD), 4.3.3 Aspaltenes, 4.1 Processing Systems and Design, 5.6 Formation Evaluation & Management, 5 Reservoir Desciption & Dynamics, 7.2 Risk Management and Decision-Making, 4.1.9 Tanks and storage systems, 1.6 Drilling Operations, 7 Management and Information
- asphaltene onset pressure, focused probe, oil base mud contamination, fluid sampling, wireline formation tester
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The Wireline Formation Tester (WFT) is a well-developed technology to collect representative downhole fluid samples. Collecting low contamination downhole samples in wells drilled with miscible oil-based mud (OBM) is challenging because the process must balance the need to acquire a sample with the desired level of contamination while using the minimum rig time. In addition, quantifying the level of OBM contamination is subject to vendor's experience and their software.
We introduce a simple but effective method for monitoring WFT sampling when targeting the low levels of contamination needed for asphaltene onset pressure (AOP) analysis. Accurate AOP measurement is critical to mitigate flow assurance risks and AOP accuracy is affected by the sample contamination levels.
The intent of this method is not to replace the well-established clean out monitoring techniques but rather to complement them. This approach uses gas oil ratio GOR data from downhole fluid analyser to predict the maximum GOR that would be achieved by pumping at infinite time and use this value as a reference to determine when the clean out process should stop and filling the sample bottles should begin.
Traditional contamination prediction methods are mainly developed for single probes and face limitations when applied to sampling with concentric probes. Although the examples used are based in focused type probes, this approach is independent of probe geometry and vendor technology.
Success stories of applying the method for obtaining high quality samples in nine sampling stations from three reservoirs in the Gulf of Mexico are presented. Laboratory analysis showed the highest OBM contamination from the samples collected was less than four weight percentage of stock tank oil (STO). In five stations the contamination was equal to or less than 1%. The highest difference between the contamination predicted real time and contamination measured in the laboratory was 1.8%.
|File Size||2 MB||Number of Pages||12|
Malik M., Torres-VerdÍn C., Sepehrnoori K., Jackson R., Weinheber P., Mullins C., Elshahawi H., Dindoruk B. and Hashem M. 2008. Comparison of Wireline Formation-Tester Sampling with Focused and Conventional Probes in the Presence of Oil-Base Mud-Filtrate Invasion. SPWLA paper LL presented at 49th SPWLA Annual Logging Symposium. Edinburgh, 25-28 May.