Effects of Long-Term Exposure to Ultrahigh Temperature on the MechanicalParameters of Cement

Effects of Long-Term Exposure to Ultrahigh Temperature on the Mechanical Parameters of Cement David Stiles David Stiles ExxonMobil Development Co. Search for other works by this author on: This Site Google Scholar Paper presented at the IADC/SPE Drilling Conference, Miami, Florida, USA, February 2006. Paper Number: SPE-98896-MS https://doi.org/10.2118/98896-MS Published: February 21 2006 Connected Content Related to: Effects of Long-Term Exposure to Ultrahigh Temperature on the Mechanical Parameters of Cement Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Stiles, David. "Effects of Long-Term Exposure to Ultrahigh Temperature on the Mechanical Parameters of Cement." Paper presented at the IADC/SPE Drilling Conference, Miami, Florida, USA, February 2006. doi: https://doi.org/10.2118/98896-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE/IADC Drilling Conference and Exhibition Search Advanced Search AbstractLong-term mechanical durability of a cement sheath exposed to stresses in a wellbore environment is critical to maintaining zonal isolation for the life of a well. The ability of a cement sheath to remain intact when exposed to changing wellbore stresses is highly dependent upon the parameters of Young's Modulus, Poisson's Ratio and tensile strength of the cement and the surrounding rock. Wellbore stresses sufficient to cause failure of a cement sheath may result from changes in temperature, casing pressure, formation pressure, or near-wellbore tectonic stresses.Wells subjected to Cyclic Steam Stimulation (CSS) for heavy oil recovery undergo extreme temperature changes that impart substantial stresses on the cement sheath. During CSS, wellbore temperatures can fluctuate between 77°F and 645°F, potentially leading to cement sheath failure. Various Finite Element Analysis models exist that are useful in predicting the failure potential of a cement sheath. These models require input of cement mechanical parameters. Mechanical parameters of numerous cement formulations have been measured in recent years but none of those measurements was made after long-term exposure of the cement to the ultra-high temperatures encountered in CSS wells. Development of such data was required to model the risk of cement sheath failure in wells subjected to CSS.This paper presents a test methodology for measuring the mechanical parameters of five cement formulations after exposure to a temperature of 645°F. Parameters of Young's Modulus, Poisson's Ratio and tensile strength were measured. Evolution of these parameters over a two-year period is presented. The temperature conditions to which the cement was exposed was found to have a significant impact on the mechanical parameters. The Young's Modulus, Poisson's Ratio and tensile strength of systems exposed to 645°F varied significantly from systems exposed to an ambient temperature of 77°F. The mechanical parameters of each individual cement formulation were also markedly different. Specialized cement systems, such as foamed cement or blends containing flexible particles, did not necessarily have mechanical parameters that were better suited for use in CSS wells than some of the more conventional formulations.IntroductionThe Cold Lake development in Eastern Alberta, Canada has been operated by Imperial Oil Resources since the mid-1980's. It is the largest in-situ heavy oil recovery operation in Canada and one of the largest thermal heavy oil operations in the world. Production of the heavy oil is enabled by CSS, which entails injecting steam into the reservoir above fracture pressure and producing a mixture of bitumen, gas and water from the same wells.There is a continuous effort to enhance thermal well integrity at Cold Lake including providing casing integrity and hydraulic isolation throughout the life of each well. Significant casing integrity improvements have already been achieved by controlling the wellbore environment during production operations and upgrading the casing connections in order to minimize the potential for casing failure. One step to achieving further improvement was to gain a more complete understanding of cement sheath performance in the thermal environment at Cold Lake.Historically within the oil and gas industry, the only concern with cement formulations at ultra-high temperatures was chemical stability. Portland cement's loss of compressive strength and increase in permeability at temperatures above 235°F was discussed in the literature as early as 1935.[1] This phenomenon, commonly referred to as strength retrogression, is the result of the morphological changes of the crystalline structure of cement when it is exposed to elevated temperatures. Preventing strength retrogression by the addition of finely ground crystalline silica at a concentration of 35 – 40% by weight of cement (BWOC) was discovered nearly 50 years ago and has been the industry standard ever since.[2] All of the cement formulations that have been used throughout the Cold Lake project contained the recognized silica concentration. Keywords: Wellbore Design, wellbore integrity, Upstream Oil & Gas, strength, cement formulation, casing and cementing, splitting tensile strength, axial, Cold Lake, cement property Subjects: Wellbore Design, Casing and Cementing, Wellbore integrity, Cement formulation (chemistry, properties) This content is only available via PDF. 2006. IADC/SPE Drilling Conference You can access this article if you purchase or spend a download.

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