What is the CT examination of oil and water wells?

The borehole passes through all underground oil layers, and the oil production and water absorption are different due to the vertical heterogeneity of each layer. In order to know the oil production of each group of oil layers or even each small layer and the water absorption of water injection wells in the production process, it is necessary to run professional logging instruments to measure the logging curves formed by a series of physical property changes in each layer, and obtain the liquid production profile of the oil well and the water injection profile along the wellbore. This process is like giving a patient a CT examination, and the oil absorption and water absorption of each oil layer are clear at a glance. This is production performance logging, and its function is to provide basis for dynamic analysis of oil and gas reservoirs and rational development of oil and gas fields. During the development of Karamay, Yamakaji, Cainan and Xishi oilfields, the logging data obtained from production performance logging accurately reflect the underground liquid production profile of each oil and gas field, which plays an important role in revealing the underground oil and water distribution.

According to different oil production wells or water injection wells, a large number of logging data can be obtained through production performance logging. Using these data, the ultimate recovery and recoverable reserves can be improved by taking corresponding measures of profile control, water plugging and separate injection for water injection wells and implementing reasonable stimulation measures and comprehensive management for oil production wells.

Another CT examination is engineering logging. The main inspection object is the wellbore, and a series of longitudinal logging curves of the wellbore are tested by running special logging instruments to check the damage, corrosion and inner diameter change of oil and water casings, perforation quality, pipe string structure, cementing quality of cement sheath outside the casing, leakage between oil layers outside the cement sheath and plugging effect. Different from production performance logging, engineering logging is a comprehensive inspection of cementing quality of oil and water wells to ensure stable and smooth access to underground treasures.

In the production process of oil and water wells, it is necessary to regularly check the fixing effect of cement ring on casing and sealing effect on formation, that is, to evaluate the cementing quality to ensure the "health" of oil and water wells. In this inspection, logging methods such as well temperature, acoustic amplitude, variable density and pulse echo are used to check the cementing quality of cement sheath height, interface between cement sheath and casing, and interface between cement sheath and formation.

In order to know the perforation position, the hit rate of perforation to oil layer, the number of holes, the damage of casing and cement sheath, and the deformation, rupture, dislocation, perforation and corrosion of casing, it is necessary to monitor the perforation and casing quality.

When the cement sheath outside the casing fails to seal the formation, the high-pressure reservoir, low-pressure reservoir and aquifer will be confused and leak each other, making the oil well unable to produce normally. After plugging operation, the plugging quality should be strictly monitored, that is, the monitoring of casing leakage and plugging quality. Commonly used methods include radioisotope logging, micro-well temperature logging and noise logging.