Probadores de formacion

|Title |INTERPRETATION OF THE PRESSURE RESPONSE OF THE REPEAT FORMATION TESTER |
|Authors |Stewart, George, Wittmann, Manfred, Schlumberger Technical Services |
|Source |SPE Annual Technical Conference and Exhibition, 23-26 September 1979, Las Vegas, Nevada|
|Copyright |Copyright 1979 American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. |
|Language |English |
|Preview |Abstract|
| |The analytical theory of the buildup pressure response associated with the pretest stage of the repeat formation |
| |tester operation is given. Both an infinite system and the case of a reservoir layer hounded above and below by |
| |impermeable barriers are considered. Thespherical flow analysis method for the infinite acting case yields the |
| |equivalent spherical permeability which is influenced by formation permeability which is influenced by formation |
| |anisotropy. For the bounded case two different types of spherical buildup are shown to occur and an analysis |
| |technique for each one ispresented which yields the spherical permeability and an estimate of the layer thickness. |
| |In circumstances where radial cylindrical buildup is observable, in principle, the anisotropy may also be |
| |determined. A quantitative result relating the depth of investigation of the permeability measurement to the |
||pressure gauge resolution is given. Computer simulations of composite systems involving a filtrate invaded zone |
| |around the well and an outer oil zone have shown how these affect the shape of buildup plots. Recommendations |
| |regarding the choice of water plots. Recommendations regarding the choice of water or oil physical properties in |
||data analysis are made. |
| |Introduction |
| |The Repeat Formation Tester (RFT*) is primarily a device for measuring the vertical pressuredistribution in a |
| |reservoir in open-hole wells. Point measurements are made by inserting a probe into the formation through the |
| |mud-cake and extracting a fixed volume of fluid while measuring the associated pressure drawdown and ensuing buildup|
| |to local reservoir pressure with a surface-recording gauge; this is knownpressure with a surface-recording gauge; |
| |this is known as pretest. The success of the operation depends on obtaining a good seal around the probe in order to|
| |detect reservoir pressure rather than mud hydrostatic pressure. In low permeability formations the buildup pressure.|
| |In low permeability formations the buildup followingpretest sampling may be of long duration and an extrapolation |
| |of the initial buildup response to reservoir pressure becomes necessary. This extrapolation must be carried out |
| |correctly if the true reservoir pressure is to be obtained. |
| |However the dynamics of the...