Earth Sciences Division, Sampling Geopressured Fluids: Design Considerations Based on Properties of the H2O-CH4 System.

摘要

The geopressured formations of the United States Gulf Coast contain hot brines with dissolved methane. These brines must be sampled for methane before an accurate economic assessment of the resource can be made. This has stimulated interest in use of conventional downhole fluid samplers and, recently, in development of samplers especially designed for the geopressured environments. The purpose of these tools is to obtain fluid samples at reservoir conditions and to bring them to the surface, preserving their integrity, for subsequent chemical analysis. Although the samplers may be sophisticated devices, the process consists of the following simplified sequence. First, the sampler is lowered in the wellbore to the desired depth where a valve arrangement, either clock-controlled or triggered at the surface, 1s activated, trapping the fluid in a sealed chamber. The sampler is hoisted back to the surface, and into the wellhead lubricator. A valve isolating the lubricator from the wellbore is closed, and the hot, high-pressure fluid contained in the lubricator is bled off before the sampler can be safely recovered. Finally, the fluid in the sampler is transferred via a suitable valve assembly into containers for chemical analyses.