RU2054537C1 - Method for determination of quality of well cementing - Google Patents

Abstract

FIELD: construction and operation of gas and oil wells. SUBSTANCE: method for determination of quality of well cementing is based on gamma-ray logging with use of radioisotopes. In this event, tightness of well lining is determined with the use of gaseous radioisotope produced by generator of radioisotopes in annular space of well. Use of the offered method prevents contamination of environment. Generator of radioisotopes possesses nonlimited service life and produces gaseous radioisotopes at any temperature and pressure. EFFECT: higher efficiency.

Description

 The invention relates to the construction and operation of oil and gas wells, in particular to methods for determining annular fluid flows in production, exploration, technological and other purposes wells.

 It is known that in the process of drilling and operating wells, annular overflows occur along channels formed due to poor-quality cementing or other reasons. Fluid flows can manifest themselves both by access to the day surface, and by flow from one layer to another.

 The elimination of such complications causes a number of difficulties due to the imperfection of the methods for determining fluid flows: recognition of manifestation objects, the direction of fluid movement and possible migration channels.

 Known methods for researching wells, carried out by methods of electro-, radio-, acoustic and thermal logging, do not allow to identify migration routes and sources of manifestations. Conclusions are based on a complex interpretation and are sometimes controversial.

 The method of radioactive indicators is used to determine the places of absorption of the drilling fluid in the well, to detect the places of annular circulation of water, to monitor the technical condition of the wells and for other purposes. According to this technique, cement mortar, drilling mud or sand is labeled with radioactive isotopes. Then gamma radiation curves are recorded before and after the introduction of radioactive carriers into the well. The changed activity values determine the sites of absorption of radioactive carriers.

Closest to the proposed method is a method for determining the quality of cementing of a well, which consists in conducting gamma-ray logging using radioisotopes located behind the casing [1]
However, this method does not allow to determine the presence of cracks, channels and voids. Since isotopes, like solid particles, are fixed after the formation of cement stone at certain points, the possibility of their movement is impossible.

 The aim of the invention is to determine the characteristics of the quality of cementing, its solidity or the presence of violations of cracks, channels, voids.

 To achieve the goal in the method for determining the quality of well cementing, which consists in gamma-ray logging using radioisotopes located behind the casing string, the tightness of the well attachment is determined by the gaseous radioisotope produced by the radio source.

 The proposed method provides the necessary information on the possible migration routes of the formation fluid, which makes it possible to predict and adopt the necessary preventive methods before the onset of complications.

 As a generator of radioisotopes, a substance (liquid or solid) with radioisotopes is used. The substance is placed in a metal capsule. The capsule is installed in the technological equipment of the casing string and lowered into the well.

 After cementing the casing, the initial, background indications of the presence of radioisotopes at the required depth are recorded. Then, after a specified period of time, control measurements are carried out, indicating the presence or absence of fluid manifestations.

 The choice of generator activity and all work in the well is carried out in accordance with the radiation safety requirements NRB-76/87 and the basic sanitary rules for working with radioactive substances and other sources of ionizing radiation OSP-72/87.

 The specified substance with radioisotopes is a generator (parent substance) that produces, under any temperature and reservoir conditions of the well, an easily moving gaseous (daughter) active isotope. The duration of the generator is designed for the life of the well and occurs in the annular or annular space. The generator is a permanent reference point (permanent mark).

 PRI me R. Radium-226 is used as a radioisotope generator. The estimated amount of substance with radium is placed in an open metal capsule, which is installed and fixed into the drill ring retainer ring casing centralizer and lowered into the well. The size of the capsule is determined by the gap between the wall of the well and the casing and can be 3–7 mm in diameter, 30–40 mm high. After cementing the casing, geophysical studies are carried out and initial, background readings are determined. After a certain time, i.e. when the production of a gas substance (radon) occurs, a repeated control measurement is carried out, which, in the presence of channels, cracks or fluid movement, will allow to recognize the beginning of a possible complication inside the wells.

 Using the proposed method can prevent pollution, since the generated radioisotope has a short half-life. The gaseous radioisotope generator has an unlimited lifespan and produces gaseous radioisotopes at any temperature and pressure (under any downhole conditions).

Claims (1)

 METHOD FOR DETERMINING THE QUALITY OF WELL CEMENTING, consisting in gamma-ray logging using radioisotopes located behind the casing, characterized in that the tightness of the well attachment is determined by the gaseous radioisotope generated by the radio source.