Cement Sheath Durability: Increasing Cement Sheath Integrity to Reduce Gas Migration in the Marcellus Shale Play

Abstract

This study examines the effects of drilling, completion, and production operations and their associated cyclic stresses on a cement sheath. The operations performed after cement placement can damage cement sheath integrity and bond with the casing or formation resulting in loss of zonal isolation and sustained casing pressure often requiring remediation and reducing productivity. This paper describes evaluation of cement sheath failure resulting from cyclic stresses experienced while drilling, fracturing, and producing shale gas wells and showcases optimization of cement systems used for Marcellus shale play intermediate casing strings. This study correlates the durability of each cement system with mechanical properties of the cements to determine each system's ability to resist failure under cyclic stresses. Two different cement compositions were used to cement intermediate casings on a number of wells. Both had similar performance properties and were designed to prevent gas migration following cementing. Wells cemented with one of the blends experienced a higher incidence of seal failure as evidenced by sustained casing pressure. In laboratory stress endurance testing, each cement system failed at a specific quantified magnitude of cumulative energy input. The results show a higher maximum endurance for the more durable cement, which also exhibits the higher field success rate. The fatigue endurance limit gives an approximation of the stress magnitude that a cement composition can withstand. Correlating laboratory endurance measurements and mechanical properties of the cement systems to field performance further quantifies the mechanical properties needed to optimize zonal isolation. U.S. shale gas production is a major component in the future of U. S. energy supply. As such, there is focus on the drilling and production of U.S. shale plays. This study takes measured look at annular seal failure and lays the ground work to calibrate it to actual field results allowing operators and service companies to select more durable cement systems. Results from this study can ultimately decrease time and funds spent repairing compromised cement seals. Furthermore, improved seal performance equates to improved well performance with lessened environmental risk and impact. IntroductionThe study reported here is a derivative of a long--term investigation aimed to improve zonal isolation for horizontal wells drilled in the Marcellus shale with the Research Partnership to Secure Energy for America (RPSEA). The impetus for this long--term study is to optimize drilling and completion practices to reduce cost, improve zonal isolation, and improve well success rate. Due to the complex environment encountered in drilling and completing horizontal shale wells, it can be difficult to determine all of the factors necessary to optimize zonal isolation. One of the initial actions of the long--term study was assessment of well performance in the Marcellus play. Interestingly, the well success rate was much lower in the intermediate strin...

An Assessment of the Dynamic Moduli of Atmospherically Generated Foam Cements

“…Previous studies (McDaniel et al 2014) have reported PR values ranging from 0.23-0.32 for cements using a Class H base with various recipes. Reddy et al, (2007) presented dynamic PR values for foamed cements of different qualities (0-25%) that ranged between 0.17-0.23.…”

“…This trend can be significant for design optimization due to the idea that an increase in PR can lead to a decrease in compressibility, which, in turn, allows the cement to play a better role in long term cement sheath integrity (Le Roy-DeLange, et al, 2000). McDaniel, et al (2014) reported YM values of Class H cements that varied between 5.2 GPa-11.3 GPa (7.54ϫ10 5 to 1.63ϫ10 6 psi). Reddy et al, (2007) presented dynamic YM values for foamed cements of different qualities (0-25%) that ranged between 12.41GPa-19.99 GPa (1.8ϫ10 6 to 2.90ϫ10 6 psi).…”

Innovation of Annular Sealants During the Past Decades and Their Direct Relationship with On/Offshore Wellbore Economics

“…To address potential issues and help operators make well-informed decisions regarding the long-term integrity of oil and gas wells, many companies, both in the service and operation sectors, have applied to some extent a more comprehensive approach when designing OWCs, taking advantage of the evolution of OWCs, both from the chemical (new systems) and engineering (new characterization tools) perspectives, to create an optimal sealant to help ensure integrity for the life of the well (Fig. In support of this statement, many studies report successful use of such techniques in yielding optimum long-term wellbore integrity in actual or simulated downhole environments (Krusche et al 2006;Shadravan et al 2014Shadravan et al , 2015aShadravan et al , 2015bGarnier et al 2007;De Andrade et al 2015;Godoy et al 2015;McDaniel et al 2014b;Griffith et al 2004;Jain et al 2014;Wang and Dahi Taleghani 2014b;Ramos et al 2009). Multiple datasets indicate significant variations in wellbore integrity (2.6 to 75%) over different time periods (Davies et al 2014).…”

HPHT Cement Sheath Integrity Evaluation Method for Unconventional Wells

“…Industry is today capable of performing up to 60 stage frac jobs in unconventional wells. McDaniel and et al (2014) investigated cement sheath durability to reduce gas migration in the Marcellus shale. Most of the wells in that shale play, are not reaching the HPHT conditions but are all subject to stress loading during hydraulic fracturing.…”