SU947413A2 - Method of hydrodynamic investigation of uncased wells - Google Patents

Description

FIELD OF THE INVENTION The invention relates to oilfield geophysics, namely, a k-guide for 5 dynamic studies of uncased wells with cable instruments.

According to the main auth. No. 471430 discloses a method used in oil field geophysics for investigating open hole wells with instruments on a cable by sampling formation fluid. This method involves the opening of the reservoir, the challenge of inflow, the determination of reservoir pressure and sampling at a constant rate. between the reservoir pressure and the sampling pressure, and the reservoir pressure is determined when the first sample is taken, and subsequent rtby samples are kept under constant pressure LlJ Ensuring the constant selection pressure does not prevent the undesirable process of degassing that occurs in the reservoir when sampling, if the sampling pressure less saturation fluid pressure. As a result, filtration becomes biphasic, which drastically reduces the accuracy of determining the permeability of rocks. The results may be underestimated by a few dozen times. Saturation pressure for various formations

varies widely: low in reservoirs with undersaturated oil and approaching reservoir pressure in reservoirs with a gas cap. In exploration wells, this value is unknown. Therefore, the known method does not guarantee monophase flow during hydrodynamic study.

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The purpose of the invention is to increase the effectiveness of hydrodynamic studies of wells by preventing the formation gas from being degassed during the extraction process.

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This goal is achieved by the fact that, in addition to taking the first sample, the saturation pressure is determined / and subsequent samples are taken at a pressure higher than the saturation pressure.

FIG. 1 schematically shows a device for implementing the proposed method; in fig. 2 is a plot of change of pressure.

25 in the sample chamber during the process of increasing its volume when determining the saturation pressure.

The device includes a hydraulic drive 1, a depression controller 2,

30, a sealing element 3, a decentralizer 4, a receiving chamber with a separation piston 5 on which the inflow velocity converter is installed, a switching valve 7, a pressure converter 8 and a compensator 9.

The determination of hydrodynamic parameters, for example, the permeability of rocks, by the proposed method, is performed as follows.

The device is lowered on the cable into the well and set in the study interval. The sealing element 3 is pressed against the wall of the well by the hub 4. With the help of depression to the formation created by the hydraulic actuator 1, the mudcake is pulled off the wall of the well and the bottom-hole zone is cleaned. Then, by reducing the pressure in the receiving chamber, the formation pressure is determined and the formation sample is displaced through the switching valve 7 into the well.

The saturation pressure is determined as follows. After filling a certain volume of the receiving chamber, the latter is closed by the switching valve 7 and pumping of the working fluid by the hydraulic actuator 1 from under the separating piston .5 under the compensator 9 continues. At the same time, the two-coordinate recording device records the pressure change in the receiving chamber depending on the displacement of the separating piston 5 s using converters 6, inflow speed and 8 pressure. This dependence consists of two linear sections (figure 2). Section a corresponds to the elastic expansion of the liquid, and area b to the liquid degassing and volume expansion of the gas. The break point of this dependence corresponds to the onset of degassing and characterizes the saturation pressure of the test sample. The sample is then forced into the well.

Know reservoir pressure and pressure, using a regulator

2 depressions during the subsequent sampling create a pressure drop across the reservoir less than the difference between the reservoir pressure and the saturation pressure, i.e. A sample is always taken at a pressure above the saturation pressure. This prevents the degassing of the reservoir sample in the process of its selection during hydrodynamic study of the reservoir. After this

The operation of the instrument is reset and is reset to the next interval.

The use of the invention will significantly improve the accuracy of hydrodynamic studies of open hole wells, and hence, the geological efficiency of testing the instrument on the cable.

Claims (1)

1. USSR author's certificate No. 471430, cl. E 21 V 49/02, 1972.