Optimization Analysis of Suction Probe for Formation Sampling While Drilling

Abstract

Formation sampling while drilling (FSWD) is one of the most advanced formation sampling technologies in the world. During the operation, a small probe with a cushion is pressed against the wellbore to reduce the pressure in the probe enough to break the cake seal and extract the fluid from the formation. The content of drilling mud filtrate (drilling filtrate or filtrate) in the extracted formation fluid is determined by pollution rate. When the pollution rate of the extracted formation fluid drops to the specified index, the valve in the sample chamber is opened for sampling. When the sampling volume is reached, the pump and valve are closed. The time from the pump opening to the pump closing is called sampling time. The shorter the sampling time is, the shorter the circulation time of drilling fluid will be, so as to reduce the sticking accidents. Due to the influence of wellbore radial space, the size of the suction probe is limited. In order to avoid phase change of the pumped formation fluid during the operation process, the suction pressure difference should not be too large, etc. In this paper, the finite element simulation method is used to analyze the relationship between the above changes of the suction probe and the sampling time in the simulation results from the aspects of changing the size, shape, structure and arrangement of the suction probe in the formation fluid sampling tool while drilling, so as to realize the optimal selection of the suction probe. The research results of this method have important guiding significance to the design of fluid sampling tool while drilling.