A mathematical model for safety assessment of crawler logging

Horizontal well production technology is an increasingly important method to improve oil recovery. However, with the intensification of oil production, the problem of high water content in horizontal wells becomes more serious and causes oil recovery to rapidly reduce. The technique of water searching with a crawler can ensure that water searching and well production works are conducted simultaneously. The application of this technique achieves good economic and environmental outcomes. But in order to ensure the water searching system within the crawler is safe and reliable, mathematical models of the ground cable tension and the head tension of the crawler need to be established. These models are calculated and appraised on the basis of the engineering case, and it is gained that theoretical calculation results are in agreement with test results. Furthermore, the free fall limit depth of the crawler obtained by our theoretical calculation is in agreement with the test result. The study results show that the mathematical models can accurately predict ground cable tension and head tension of the crawler and are important to reduce the risks of the well logging as well as improve the success rate of water locating.