How to Use Expansion Rubber to form an Adaptive Sealing Layer to Solve Severe Loss——Materials, Effects and Theory

Abstract

Abstract During oil and gas drilling, severe loss from fractured formations is often encountered, which significantly increases drilling costs. The main reasons for failure plugging operations are twofold: firstly, it is difficult to achieve effective matching between the sizes of the plugging particle material and the fracture; Secondly, underground fractures are actually in a dynamic process of size change, leading to repeated losses, however, it is an important feature that has been seriously ignored before. This paper introduces a key material with great potential to solve the above problems—adaptive smart expansion rubber. A detailed analysis was conducted on the composition and function of the material, and water absorption equilibrium swelling evaluation experiments were conducted to investigate the strength changes and expansion force of the material before and after expansion. Furthermore, the sealing effect of the material on fractured layers was further evaluated. The evaluation results demonstrate that the expansion rubber exhibits higher strength both before and after expansion, surpassing traditional water-absorbing expansion gel particles. The material can expand by a volume ratio up to 750% and generate at least 50kPa of support stress after expansion. The evaluation of the plugging experiments indicates that the material can effectively enter the interior of the loss layer and successfully solve the loss. The plugging effect increases with the increase of water absorption and expansion time. This paper further proposes a new theory of adaptive sealing, which means that the expansion rubber can enter multi-scale fractures through elastic deformation under the differential pressure, and support the fracture wall surface through continuous expansion, thereby adapting the fracture size and sealing fractures. This paper fully utilizes this smart material to improve the success rate of primary plugging and reduce the rate of repeated losses, saving plugging time and cost, which has important reference value.