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摘要
In the past few years, many studies have been focused on how to take virgin formation fluids successfully under increasingly tough formation conditions, such as: Low permeability zones: Based on field test feedback, traditional probe has difficulty taking formation fluids sample when permeability is less than 1md. By re-designing the probe to increase its surface contact area with the formation; flowrate can be increased significantly which helps in taking formation fluids' samples. It is reported from field that the latest Saturn 3D Radial probe successfully took samples in 0.01md permeability formation because its probe area is around 500 times that of a standard traditional probe. Drilling with oil based mud: Due to oil based mud filtrate mixing with formation oil, it is difficult to take a clean virgin formation fluid sample. For this challenge, the researcher designed a special probe splitting traditional probe's flowline from single flow line into two separate flow lines; a guard line and a sample line to separately draw mud filtrate and virgin formation fluids. Virgin formation fluids collection is totally dependent on the ability to draw the fluid into the probe. Besides low permeability and fluids mixing, deep invasion is another challenge that can hinder the drawing of a clean virgin formation fluid sample. According to experiments and practice in the field, whether virgin formation fluids can be taken successfully depends mainly on the formation permeability. In theory, the higher the permeability, the easier it is to draw formation fluids into formation tester. However, with increasing invasion depths, mud filtrate occupies a bigger area surrounding the borehole and will lead to difficulty for virgin formation fluids breaking through and flowing into formation tester probe. This is because a large amount of mud filtrate will flow into the probe along different orientations. According to this research paper, in order to speed up the formation oil flow into the probe, the permeability heterogeneity plays a very important role. The numeric simulation shows that if formation permeability is more heterogeneous, the virgin formation fluids can be easier to obtain because horizontally oriented fluids will form a dominant flow channel which has a relatively higher velocity compared to the vertically oriented fluids. So, the traditional sampling method becomes increasingly difficult to take virgin formation fluids sample in both low permeability zones and high permeability homogenous zones. To solve the problems facing the ease of pumping virgin formation fluids into the probe, this paper will demonstrate a novel tool design combining traditional formation testing tools and resistivity tools to measure the formation resistivity of virgin fluids sweeping area in real time. By adding electric buttons on the Saturn probe and measuring its voltage trend during pumping, we can obtain 4 different orientations' formation resistivity trends in real time. Through inversion of the formation resistivity of sweeping area nearby borehole, we can estimate virgin formation fluids properties in real time and predict when virgin formation fluids flow into the probe.
- 出版日期2017-7
- 单位油气资源与探测国家重点实验室; 中国石油大学（北京）
