Unconventional Challenges and Solutions in Liner Cementing: A Case History from Nigeria

Abstract

Abstract Incorporation of innovative well delivery practices has been on an increase over the years and there are several phases of operational engagement that aid in achieving the required well objectives. Primary cementing is a key phase of wellbore construction as it secures the well's structural integrity, also serving as a barrier to keep formation fluids at bay. There are several challenges associated with carrying out wellbore zonal isolation for conventional primary cementing of casings. However, a unique level of attention is required during the design and execution stages of liner cementing. The slurry design requires careful formulation to desired specifications while ensuring it is easily deployed and placed in the liner annulus. Additionally, there are several downhole tool constraints that come with liner cementing related to the complexity of the liner hanger technology. Various tool configurations are available to make up the liner hanger system. A typical system will include casing joints and the liner top packer Run in Hole (RIH) to the designed depth. The process of cementing a liner comes with unique procedures. From the design phase to the execution, special consideration of all downhole fluids to ensure flawless cement placement while preventing intermixing and contamination is critical. The complex nature of the liner hanger system requires thorough analysis in order to provide lasting solution to effectively perform cementing placement and zonal isolation throughout the liner casing, hanger assembly and liner top. One major challenge is the risk of possible contamination of the cement slurry with un-displaced mud in certain sections of the liner hanger system. The effects of mud/cement contamination can lead to grievous consequences and is fully analyzed in this paper. A high profile cementing operation carried out in the southern part of Nigeria is used as a case study on how the liner hanger configuration and drilling fluids design can positively influence the successful deployment and effective zonal isolation of the liner. Emphasis on several procedural considerations that are often overlooked while designing the drilling fluids properties and characteristics for liner hanger cementing will be presented with recommendations on tracking and with improvements in future operations noted.