Multistring Analysis of Well Growth (2004)

Multistring Analysis of Well Growth Jan A. Aasen; Jan A. Aasen Stavanger University Search for other works by this author on: This Site Google Scholar Bernt S. Aadnøy Bernt S. Aadnøy Stavanger University Search for other works by this author on: This Site Google Scholar Paper presented at the IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition, Kuala Lumpur, Malaysia, September 2004. Paper Number: SPE-88024-MS https://doi.org/10.2118/88024-MS Published: September 13 2004 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Get Permissions Search Site Citation Aasen, Jan A., and Bernt S. Aadnøy. "Multistring Analysis of Well Growth." Paper presented at the IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition, Kuala Lumpur, Malaysia, September 2004. doi: https://doi.org/10.2118/88024-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition Search Advanced Search AbstractThis paper presents simple models to describe casing loading and wellhead movement during the completion (mechanical) phase and the production (thermal) phase. A wellhead-drop incident is investigated. The theory is simple, and the formulations are suitable for hand-calculation or spreadsheet. The presented models are suitable both for conventional and HP/HT (high-pressure/high-temperature) wells.This paper also investigates an abrupt wellhead drop of several feet for an offshore well. The incident took place during wellhead cooling following a routine shutdown. The expected wellhead cooling contraction did not occur. After a cooling period the wellhead suddenly released. A corroded segment of the surface casing collapsed and the wellhead dropped.IntroductionThe platform well sits in 1000 ft of water. There is a 165-ft air-gap between the mean sea level and the wellhead deck. The 26" environmental casing is piled 330' into the mud and it is not attached to the wellhead. The completion program consists of 18–5/8", 13–3/8" and 9–5/8" casing strings. The well produces through a 5–1/2" production tubing landed in a polished bore receptacle (PBR).First we look at the casing loading that occurred during the initial well completion. Casing loads are caused by adding and removing well tubulars and well control equipment. We consider constant temperature during the completion phase. The second part deals with wellhead growth caused by natural production and rise in temperature. In the third part, the failure of the 18–5/8"casing is analyzed as the wellhead drops 43 cm (17") below its cold position. In the fourth part, the incremental loads and wellhead movement data are summed using the principle of superposition. In this final part, the axial load and buckling limits for critical well tubulars are calculated and compared for the situation following the casing failure.It is difficult to estimate both the direction and the amount of well friction during casing loading and wellhead growth. Operational procedures and actual execution of the completion phase are complex, and unexpected events increase the uncertainty associated with tubular strain caused by downhole friction. The amount of frictional strain remaining in the casing strings after completion will impact subsequent calculations. In this study the analysis is performed in a frictionless environment using the projected height concept (Ref. 1). The axial weight of the well tubular without sliding friction is equal to its unit weight multiplied by the projected pipe height, regardless of the borehole inclination and path. The frictionless approach is attractive due to its simplicity and also because it gives a conservative estimate of casing loads and wellhead movement. In this approach, we use true vertical depth (TVD) for load calculations and measured depth (MD) for thermal expansion.Throughout this investigation, contraction is considered negative and expansion is positive. Similarly, axial compression is indicated with a negative sign and tension is positive.Casing Lloading at the Time of InstallationWe analyze the casing loading caused by well construction. The initial casing loading is needed for a complete description of the axial force in the well tubulars following the 18–5/8" casing failure.The equations used for wellhead movement and multistring loading were developed using classical mechanics. See Appendix A for the theory covering a three-string model. Keywords: cross-sectional area, compression, wellhead drop, wellhead growth, loading, casing and cementing, iadc spe 88024, well control equipment, casing design, wellhead movement Subjects: Casing and Cementing, Casing design This content is only available via PDF. 2004. IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition You can access this article if you purchase or spend a download.