Determination of the Minimum Testing Time for Wireline Formation Testing with the Finite Element Method

1. Introduction The first generation of formation testing tool was introduced more than half a century ago. Since then, three generations of wireline formation tester tools (WFT) have been developed. WFT is an effective method for locating the fluid contact interface (gas/oil/water), verifying the formation pressure, and estimating the fluid density in respective zones. (Michaels, et al., 1995) As a sole tool used in dynamic formation testing, especially in exploration of complex reservoirs…

Determination of the Minimum Testing Time for Wireline Formation Testing with the Finite Element Method

The wireline formation tester (WFT) is an important tool for formation evaluation, such as calculating the formation pressure and permeability, identifying the fluid type, and determining the interface between oil and water. However, in a low porosity and low permeability formation, the supercharge pressure effect exists, since the mudcake has a poor sealing ability. The mudcake cannot isolate the hydrostatic pressure of the formation around the borehole and the mud seeps into the formations, leading to inaccurate formation pressure measurement. At the same time, the tool can be easily stuck in the low porosity/low permeability formation due to the long waiting and testing time. We present a method for determining the minimum testing time for the wireline formation tester. The pressure distribution of the mudcake and the formation were respectively calculated with the finite element method (FEM). The radius of the influence of mud pressure was also computed, and the minimum testing time in low porosity/low permeability formations was determined within a range of values for different formation permeabilities. The determination of the minimum testing time ensures an accurate formation pressure measurement and minimizes possible accidents due to long waiting and testing time.