Application of Cementing Technology for Wells with Active Shallow Gas Migration in the Tarim Oilfield

Owing to the complex geological conditions in the Tarim Oilfield, accurate identification of formation fluids is often challenging, especially in the absence of reliable data from offset wells. When active shallow hydrocarbon zones are encountered during drilling, operational constraints arise due to the shallow setting depth of the surface casing and the low fracture pressure of the overlying formations. These limitations prevent the use of higher drilling fluid densities that would otherwise be required to reduce gas migration velocity and lower gas readings while circulating prior to casing running. As a result, cementing operations are exposed to risks such as post-cementing gas channeling and sustained casing pressure in later production stages. To mitigate these issues, field practices have been leveraged to develop an integrated cementing technology suitable for wells with active shallow gas migration. Key components of this technology include: evaluation of the wellbore’s safe density window, enhanced wellbore conditioning, optimization of the fluid column structure, selection of suitable cementing methods (single-stage or two-stage), application of tailored cement slurry systems (such as self-healing and thixotropic slurries), and implementation of circulation or backpressure during the waiting-on-cement (WOC) period to balance formation pore pressure. This integrated approach has been successfully applied in several wells with active shallow gas in the Tarim Oilfield, all of which have achieved positive outcomes. No post-cementing annular gas channeling was observed, and no abnormal annular pressure was recorded at the wellhead during subsequent production.