An improved Model for Wireline Formation Tester Pumpout Time Estimation
- Waqar Ali Khan (Schlumberger) | Robert A. Wattenbarger (Texas A&M University) | Syed Shahbir Shah (Schlumberger) | Agha Hassan Akram (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 30 October-2 November, Denver, Colorado, USA
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 1.11 Drilling Fluids and Materials, 1.6 Drilling Operations, 1.5 Drill Bits, 5.5.8 History Matching, 5.3.2 Multiphase Flow
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Wireline formation testers are now in their third generation of development. These tools are used to measure formation pressure andpermeability, and to take fluid samples from the reservoir. Technological developments over the years have resulted in a modular tool that can obtain a clean formation fluid sample with minimal contamination. Sampling time varies from a few minutes to many hours depending upon different parameters i.e. depth of invasion, flow rate, formation permeability, anisotropy, porosity and the viscosity of the involved fluids including mud filtrate and formation fluids.
Total pumpout time required to obtain a clean sample is always of interest to both the operator and service company owing to economics, well stability and other factors. An approach is required that is flexible and that requires few parameters to estimate the pumpout time and the time for first formation fluid slug.
In this study a new polynomial model is developed to better estimate the time to first slug.
The new model was tested for different pumpouts from different wells and history matching was performed to test the accuracy of the model. A number of pumpouts were considered and all of those showed close matches. Software was developed to quickly calculate the total pumpout time at real time. Also in this study the previous model was tested and with the limited available data the new model showed much improved results over the previous model.
A formation tester is used to take a representative sample from the formation fluid by producing the formation through a probe set at the wellbore. This sampling process can take a variable amount of time which is a critical factor for both operator and Service Company. Several parameters influences this time. This work examines details of these parameters and models a new formulation that is simple to use and that covers the effect of these parameters in a generic way.
Drilling disturbs formations as shown in Fig. 1 and Fig. 2 when a drill bit penetrates a porous and permeable formation, fluid will flow from the well bore into the formation because the hydrostatic pressure of the mud column is greater than the pressure of the formation. Drilling mud contains particles which are deposited on the face of the formation. The purpose of these particles is to reduce the amount of fluid which enters the formation. The deposited material is called the mud cake and the fluid which enters the formation is called mud filtrate.
|File Size||492 KB||Number of Pages||9|