New Mechanical Solutions for Isolating Severe Losses in High Temperature Wells

Abstract In recent years, with the development of China's oil and gas exploration to deeper layers, the number of deep & ultra-deep wells has been increasing year by year. The casing layer sequence in the well structure design reaches 6 - 7 layers, which has tended to the design limit, but the handling ability is still insufficient in the face of sudden complex formations. Complications such as severe loss and different pressure systems in the same formation are encountered during drilling, resulting in early casing, which may not achieve the exploration target in the end. The open hole clad technology based on high performance solid expandable tubular is focus on solving difficult problems that weak and complex formation and severe drilling loses which cannot be effectively plugged or controlled. This paper studies the open hole clad technology based on high performance solid expandable tubular in exploration wells by using the methods of indoor test and field trials. The operation principle and technical characteristics of open hole clad technology are introduced in detail. And the test of expansion tubular performance, expansion cone performance and thread sealing strength were carried out to study the expansion tubular operation process. Then aiming at LZ1 exploration well with complications such as severe loss and different pressure systems in the same formation are encountered during drilling, the open hole clad technology field experiment was carried out, and the clad effect of expansion tubular were analyzed. The research results showed that: (1) the indoor tests of expansion tubular performance, expansion tubular cone performance and thread sealing strength verified the reliability of expandable tubular open hole clad technology which can effectively deal with the severe drilling loses on the safe drilling in exploration wells. (2) LZ-1 exploration wells have successfully created conditions for safe drilling in the target formation of LMX group by using Φ219mm expandable tubular to clad the complex formation. Through the method of mechanical seal, the sudden complex situation is solved, and the equivalent density of bottom hole is more than 2.1 g/cm3 after rapid plugging of complex strata, which make sure the drilling of the lower formation was smooth. The ability to seal complex formations with severe losses using open hole clad technology based on high performance solid expandable tubular can be used to solve the complications such as severe loss and different pressure systems in the same formation in exploration wells, making sure the drilling of the lower formation was smooth.