What is drilling prestress?
Drilling engineering is the key link of oil and gas exploration and development, and its success directly affects the exploitation efficiency and economic benefit of oil and gas resources. However, with the gradual deepening of oil and gas exploration, more and more complex geological conditions and high-pressure formations are encountered in drilling engineering, which makes the problems of wellbore stability and safety more and more prominent. In order to cope with these challenges, drilling prestressing technology came into being.
Drilling prestressing refers to a kind of prestressing technology used in the process of drilling in order to enhance the stability of the well wall, improve the bearing capacity of the well wall and extend the service life of the well wall. This technology applies pre-designed prestress in the shaft wall to make the shaft wall structure better resistant to deformation and damage when subjected to external forces.
The purpose of prestressing drilling
Enhanced wellbore stability
In high-pressure or unstable formations, uneven distribution of ground stress around the wellbore can lead to wall collapse, fractures, or wellbore instability. By applying prestress, the stress state around the wellbore can be changed, reducing the concentration of in-situ stress, and keeping the wellbore stable during drilling and subsequent operations.
Increase carrying capacity
During the drilling process, the wellbore is subjected to a variety of loads from the upper formation, downhole pressure and drilling tools. Through the application of prestressing, the bearing capacity of the wellbore and downhole equipment is enhanced, which can better cope with high-pressure formations or complex downhole conditions and avoid wellbore deformation or damage.
Control formation stress distribution
Under some special formation conditions, the stress distribution around the wellbore may be uneven or present an unfavorable state, which is easy to cause the formation around the wellbore to break or slip. By applying prestressing, these stresses can be redistributed more evenly around the wellbore, avoiding engineering accidents caused by local stress concentration.
Extend wellbore life
Long-term changes in in-situ stress, temperature, and downhole fluid erosion can lead to gradual wellbore failure. Prestressing technology can reduce the fatigue damage of wellbore and prolong the service life of wellbore effectively by designing reasonable stress state in advance.
Prevent wall collapse and blowouts
In the process of drilling, wall collapse or blowout is a serious engineering accident, which may lead to personal safety and economic loss. Prestressing technology can improve the ability of the wellbore to resist collapse and reduce the risk of kicks and blowouts by controlling the stress state around the wellbore.
