Heavy oil sampling with wireline formation testers
Schlumberger's Peter Weinheber, presented a compelling paper on heavy oil sampling with Wireline Formation Test (WFT) tools at the recent December 2009 International Petroleum Technology Conference in Doha, Qatar.
The paper reviews requirements and best practices for the successfull sampling of heavy oil reservoirs with WFT tools. This includes the modeling of drawn down and flow rates before actually sampling the reservoir. The modeling information is then used to design the appropriate WFT tool string from the many options available today such as selecting the appropriate of hydraulic pumps, probe, and packer options.
The paper goes on to point out that the sampling of heavy oil has unique challenges because the oil has a high viscosity and will not flow easily. High fluid viscosity and lower mobility is often compounded in that many heavy oil reservoirs are relatively shallow and the oil at reservoir conditions is cooler and more viscous than if sampled deeper with higher temperatures. In addition to being shallow, heavy oil reservoirs tend to be unconsolidated sands and subject to stability issues. Another complicating factor is that the drilling of heavy oil reservoirs with fresh water muds tends to create oil-water emulsions which can negatively impact fluid sample quality and downhole fluid analysis.
Heavy oil fluid sampling and analysis is essential to succcessful reservoir management; applying new WFT design technology with pre-job modeling improves both sample quality and the resulting analysis.
You can download the full paper at the following link SPE 10.2523/13917-MS.
Kambiz.
