PSI - Issue 36

Liubov Poberezhna et al. / Procedia Structural Integrity 36 (2022) 326–333 Liubov Poberezhna, Ihor Chudyk, Volodymyr Khomyn et al./ Structural Integrity Procedia 00 (2021) 000 – 000

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of leaks are accompanied by frequent griffins, i.e. open outlets of oil and gas to the earth's surface in the downhole zone. According to the information on the completed wells, the hydrocarbon leaks are recorded visually. The approximate service life of casing is from 25 to 30 years (Poberezhny et al. (2017, 2018), Kryzhanivskyi (2019)). After this period, the pipes due to wear and corrosion must be restored or eliminated (tamponing) (Chernov et al. (2002)). According to the data on the corrosion rate (Poberezhny et al. (2017, 2019), 2019)), the expected service life of the equipment (Maruschak et al. (2014), Poberezhny et al. (2019), Zapukhliak et al. (2019)) from the moment of inspection to the maximum corrosion wear (in years) is calculated:

all    −

T  =

.

m

(1)

,

c

where ΔT – ultimate corrosion wear; δ all – allowable corrosion wear; δ m . – actual (measured) corrosion wear; υ c - average corrosion rate. Knowing the maximum corrosion wear, you can calculate the estimated service life of the equipment from the moment of its commissioning to the maximum corrosion wear:

T

act Т Т = +  ,

(2)

p

where T p – projected service life of the equipment (in years); Т act - – the actual service life of the equipment at the time of the inspection. The pump-compressor pipes can be lifted from the well and replaced, unlike the conductor, production, and technical columns, which are cemented in the well. Abandoned, decommissioned wells have such a state of the casing as in Fig. 3.

Fig. 3. Pump and compressor pipes are destroyed by corrosion.

Repair work involves re-cementing the wellhead, but the casing is subject to further destruction. Due to this, subsoil pollution can occur covertly and go to aquifers, and in the presence of favourable conditions (permeable layers of rocks) enter the atmosphere in the form of gas manifestations in the vicinity of the well - griffins. Therefore, such measures can be considered harmful from an environmental point of view. Fig. 4 shows a scheme of a well that has been decommissioned and possible ways of entering hydrocarbons in different environments from different depressurized sections of casing. The decommissioned oil and gas well consists of: 1. Concrete pedestal, which is installed during the decommissioning of the well instead of the mouth equipment; 2. Conductor - casing to insulate the upper aquifers; 3. Aquifer;