RU2405934C2 - Method for determination of technical condition of wells - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: method includes lowering radioactive survey tools down to well bottomhole, recording curve of distribution of natural gamma-activity from bottomhole to wellhead, radiation with neutron flux with the help of tools of pulse neutron-neutron survey. Curve of induced gamma-activity is recorded. Curves of distribution of natural and induced gamma-activity are compared along the well axis. At the same time geophysical surveys are carried out in operating well via lubricator. Radiation with neutrons flux is carried out in the intervals higher and lower than perforation holes. Recording natural and induced gamma-activity is done with the help of additional sensor installed on product line at wellhead. At the same time gamma-activity is registered before radiation of borehole annulus, after radiation of well bore interval arranged below interval of perforation and higher than specified interval in zone of occurrence of water-bearing reservoirs. Sources of water invasion of well products are determined by shape of curves of induced gamma activity, single-humped shape demonstrates underlay of bottom water, and double-humped - water supply from overlying reservoirs.

EFFECT: improved validity of wells cementing quality determination, detection of defects of cement ring behind operation string, intervals of borehole annulus untightness, sources of water supply and water invasion into well products.

1 dwg

Description

The invention relates to the oil and gas industry and can be used to determine the technical condition of wells by the method of radioactive logging: defects of the cement ring behind the production string, leakage intervals of the annulus, water supply sources and watering of the well production.

A known method for assessing the quality of cementing wells, including:

- descent of a downhole tool containing a source and receiver of radioactive radiation;

- recording (on the rise) of the curves of changes in radiation intensity, which are used to judge the density and uniformity of filling the annulus of the wells (as a function of depth and perimeter) with cement grouting (Yu.A. Gulin, D.A. Bernstein, P.A. Pryamov. “Acoustic and radiometric methods for determining the quality of cementing of oil and gas wells.” M., Nedra, 1971, pp. 5-27) (1).

The known method has the following disadvantages:

- does not reveal cracks and other defects of the cement ring, which slightly change the bulk density of the medium in the control zone;

- biologically dangerous;

- requires complex work to eliminate the consequences of a radiation accident when leaving the device with a source of radiation at the bottom of the well.

It is also known to use the method of thermometry for detecting fluid flows in the annulus of wells by recorded temperature anomalies (Journal of Oil Industry, 1978, No. 11, pp. 51-53) (2).

However, using the method of thermometry, it is possible to identify only significant volume flows of fluids that lead to noticeable temperature anomalies, and in gas wells, positive and negative temperature anomalies also arise from the effects of compression and expansion of the gas moving in the annulus of the wells (through the flow channels), those. in the general case, thermal effects are ambiguous.

Therefore, in most cases it is impossible to determine the leakage intervals of annular space and the sources of flooding of gas well products.

The closest in technical essence and the achieved result to the claimed method is a method for determining the technical condition of wells, including killing and preparing a well, launching a radioactive logging tool to the bottom of the wells, recording the distribution curve of natural gamma activity from the bottom to the wellhead, and irradiating with a neutron flux using pulsed neutron-neutron logging instruments with subsequent recording of the induced gamma-activity curve, comparison of the distribution curves of natural and nav gamma-degenerate activity along the borehole axis and defining slots leaking wells annulus (Patent RU №2199007, Cl. E 21 B 47/10, publ. 2003 YG) (3).

However, using the known method, only injectivity intervals are determined in the non-tight annulus of the well (above and below the perforation interval), and the intervals through which formation water flows and the causes of water cut in the well’s production are not revealed.

The objective of the present invention is to increase the reliability of determining the quality of cementing of wells, identifying defects in the cement ring behind the production casing, leakage intervals of annular space, sources of water supply and watering of well products.

The essence of the present invention lies in the fact that in the known method for determining the technical condition of wells, including the descent of radioactive logging tools to the bottom of the well, recording the distribution curve of natural gamma activity from the bottom to the wellhead, irradiation with a neutron flux using pulsed neutron-neutron logging tools with subsequent recording of the induced gamma activity curve, comparison of the distribution curves of natural and induced gamma activity along the axis of the well, according to the invention In geology, geophysical studies are carried out in a working well through a lubricator, irradiation with a neutron flux is carried out in the intervals above and below the perforation holes, the natural and induced gamma activity is recorded using an additional sensor mounted on the product pipeline at the wellhead, and gamma activity is recorded up to annular space irradiation, after irradiation of the borehole interval located below the perforation interval and above the specified interval in the zone beyond aquifer formation, and well production watering sources are determined by the shape of the induced gamma activity curves, the one-humped form indicates the flow of bottom water, and the two-humped form indicates the flow of water from overlying strata.

The method is as follows (see drawing).

- into the investigated well, cased by production string 1, is lowered using a logging tool 2 on a wireline 3 downhole neutron-neutron logging device 4 through a lubricator 5 and a flow fitting 6 into the bottom hole zone 7 below the reservoir 8 and the perforation interval 9;

- at the wellhead, a ground-based gamma radiation sensor 10 is installed on the product pipeline 11 and background values of gamma activity of the fluid (gas condensate mixture) entering through the perforations (not shown) in the perforation interval 9 are recorded;

- irradiate a section of the wellbore below the perforation interval 9 (bottom-hole zone) and record a change in the readings of the gamma activity sensor 10 installed on the product pipeline 11 using the field computing complex 12.

In this case, in the case of an inflow of bottom water containing sodium and chlorine ions through defects of the cement ring below (from the underlying aquifer 13), the gamma activity sensor 10 will increase due to induced gamma activity, which after irradiation with pulsed neutron neutron logging 4 will decrease. Thus, one burst of induced gamma activity is formed and recorded.

To identify possible waterlogging of well products from an overlying aquifer, studies are carried out in the following sequence:

- the pulsed neutron-neutron logging device 4 is raised from the bottom, installed above the perforation interval opposite the overlying aquifer 14 and irradiated through the production string;

- register the values of gamma activity with a sensor 10 installed on the wellhead on the product pipeline 11. In this case, in the case of inflow of water containing sodium and chlorine ions through defects in the cement ring from the upper aquifer 14, the readings of sensor 10 will increase due to induced gamma activity inside production casing 1, as well as in annular space.

After the end of irradiation with pulsed neutron-neutron logging instruments 4, a packet of fluid contained within the production string is first suitable for the gamma activity sensor 10, and then a packet of fluid contained in the annulus is suitable.

Thus, two bursts of induced gamma activity are formed and recorded.

The source of watering the products is determined by the shape of the induced gamma-activity curve, with the one-humped form indicating the flow of bottom water, and the two-humped form - the flow of water from overlying strata.

The inventive method allows to increase the reliability of determining the quality of cementing of wells, to identify defects in the cement ring behind the production casing, intervals of leakage in the annulus, sources of water supply and watering of the production of the well.

Claims (1)

A method for determining the technical condition of wells, including the descent of radioactive logging tools to the bottom of the well, recording the distribution curve of natural gamma activity from the bottom to the wellhead, irradiation with a neutron flux using pulsed neutron-neutron logging instruments, followed by recording the induced gamma activity curve, comparing the curves distribution of natural and induced gamma activity along the axis of the well, characterized in that geophysical studies are carried out in a working well h lubricator, irradiation with a neutron flux is carried out in the intervals above and below the perforation holes, the recording of natural and induced gamma activity is carried out using an additional sensor installed on the product pipeline at the wellhead, and gamma activity is recorded before the annulus is irradiated, after the barrel interval is irradiated wells located below the perforation interval and above the specified interval in the zone of occurrence of aquifers, and the sources of waterlogging products s is determined by the shape of the curves of induced gamma activity A single-form Plantar indicates inflow of water and humped - admission of water from overlying layers.