Digital System Integration Testing of Surface Wellhead Systems
Authors: Song Fei , Sanchez Chris , Li Ke , Robinson Stuart , Guidry Kirk 
Published: January 2022

Abstract
A wellhead system includes components on the surface of an oil or gas well that provide access to the main bore of the casing or tubing or to the annulus as well as enables pressure control of a production well. The wellhead system serves as the surface termination of a wellbore that incorporates facilities for installing casing hangers during the well construction phase, and also incorporates a means of hanging the production tubing and installing the Christmas tree and surface flow-control facilities in preparation for the production phase of the well. System Integration Testing (SIT) of such a complex wellhead system is an essential step for confirming equipment interfaces and functionalities and ensuring that every component operates as expected. Such a test typically takes weeks to months of planning, scheduling, and coordinating among all participating customers, project managers, engineers, and manufacturing, planning, and service personnel. Engineers ensure all parts and tools are present and verify that the compatibility and functionalities meet the system’s design and customer requirements. Equipment is then dismantled and readied for the actual SIT in front of customers. Lengthy SIT events could also involve many HSE hazards. Further, even if a SIT is successful, expendable items must be purchased, extending the lead time.
In this paper, a model-based hybrid computational framework is developed for efficiently virtualizing the system integration test of a surface wellhead system. Such a simulation methodology can enable transformation of conventional physical SIT to digital SIT (i.e., DigiSIT) with “scan-to-assembly” experience by performing a virtual SIT on an as-built wellhead system for anomaly detection. Specifically, a laser scanner digitizes the physical parts to the point cloud. A computing engine with rapid hybrid simulation ingests the 3D geometries. A motion mechanics solver can then simulate the movement of motion-centric components to efficiently detect interference between contacting parts, which helps identify design or manufacturing flaws. A deformation mechanics solver then simulates deformation-critical components, e.g., seals, to predict stress states and contact pressures that affect structural integrity and functional seal performance. DigiSIT can deliver an unprecedented factual view of system compatibility and functionality — without damaging or sacrificing parts. The developed simulation methodology was validated by comparing the simulation results to those observed during lab tests and field operations. For example, after a physical SIT exercise revealed a failure, the failed assembly was submitted for DigiSIT analysis. It was found that DigiSIT had favorably predicted the failure observed in the physical SIT, substantially increasing confidence in the methodology and substantiating its use for root cause analysis (RCA) and design validation. Furthermore, the developed simulation methodology presented in this study is also expandable to other product lines that involves assembling process.