DI-92 – “Limit States Design of Well Casing in Massive Salt Formations”

DI-92  – “Limit States Design of Well Casing in Massive Salt Formations”

Date Submitted: January 14, 2000

Title: Limit States Design of Well Casing in Massive Salt Formations

Submitted by: C-FER Technologies Inc. 200 Karl Clark Rd. Edmonton, AB, Canada T6N1H2 (780)450-3300

Principal Investigator (s): Cam Matthews – c.matthews@cfertech.com Brian Wagg – b.wagg@cfertech.com

Business Impact: One of the current approaches to casing wells through massive salt formations is to design the well for full litho static collapse pressure. It is suspected that this is an overly conservative design approach that results in heavy wall or dual-concentric-cemented casing strings that are expensive and/or difficult to handle. The proposed work would provide operating companies with a process to optimize well casing design by avoiding overly conservative designs while ensuring the required well service life.

Technical Objectives: The basic objective is to develop a semi-empirical, strain-based, limit states design approach for well casing in salt formations that explicitly addresses the formation movements and loading scenarios occurring within the salt formation and at its geomechanical boundaries.

Methodology: The work would consist of a combination of: 1) field measurements of casing deformations based on multi-sensor caliper logs processed using C-FER’s proprietary CalTran software to characterize the mechanisms of casing deformations. 2)full scale laboratory testing to establish casing performance under the loading conditions indicated by the multi-sensor caliper logs 3) 3-D numerical simulations of casing/formation interaction addressing both pipe body and connection performance under combined loading conditions benchmarked to both laboratory results and field measurements. 4) Use the combined field, lab and simulation results to develop a semi-empirical, strain based limit states method to design well casing

Deliverables: The principal deliverable would be strain limit design equations for casing with the actual “failure”, or limiting criteria based on either material strain or on functional limits of the well casing in terms of drift diameter reduction. The resulting equations would provide a comprehensive strain-based model that would predict casing response in massive salt formations for a wide range of casing sizes, weights and grades. A secondary deliverable of this analysis would be a thorough understanding of the formation movements that occur in, and adjacent to, a massive salt formation. This knowledge could lead to new drilling or completion practices that can further reduce the cost of wells or improve well casing performance.

Comments: Major operating companies in both the North Sea and Gulf of Mexico have recently made inquiries into the development of a limit states design approach for casing in massive salt formations.