METHOD OF DIAGNOSTICS OF FILLING OF CASING ANNULUS OF OIL AND GAS WELLS WITH LIGHT AND LIGHT-WEIGHT CEMENTS BY NEUTRON METHOD AND SCANNING DEVICE FOR ITS IMPLEMENTATION Russian patent published in 2020 - IPC G01V5/10 

FIELD: physics; oil and gas industry.

SUBSTANCE: use: for neutron logging in the mode of circular scanning of oil and gas wells. Essence of the invention consists in the fact that three-probe neutron-neutron logging is realized using epithermal neutrons – PNNLen using a downhole tool with three probes of different length. During rotation around the body axis of the instrument, the intensity of epithermal neutrons – J_c.tek.i – is detected by central and peripheral neutron counters of all PNNLen probes and the readings – J_c.tek.i are normalized to the readings of these counters in water – J_c.i, using J_c.tek.i and J_c.i, by formulae the function of F_cem cement is calculated_. Determining the distribution of cement into the annulus at different distances from the wall of a well casing, the cement and calculating deficiency functions ΔF_cem. Using minimum and maximum values of ΔF_cem., performing integral estimation of cement fraction along perimeter of circular borehole space – C_p.int.cem. by separate i sectors for each probe. Using the minimum and maximum values J_c.i, an integral estimate – C_c.int. of proportion of cement along casing annulus perimeter by the investigated interval, is calculated.

EFFECT: high reliability of investigating wells using a neutron method, which enables to perform detailed analysis of features of filling cement space with cement.

9 cl, 2 dwg