The high-profile blowout at Macondo well in the US Gulf of Mexico, brought the challenges and the risks of drilling into high-pressure, high-temperature (HPHT) fields increasingly into focus. Technology, HSE, new standards, such as new API procedures, and educating the crew seem to be vital in developing HPHT resources. High-pressure high-temperature fields broadly exist in Gulf of Mexico, North Sea, South East Asia, Africa, China and Middle East. Almost a quarter of HPHT operations worldwide is expected to happen in American continent and the majority of that solely in North America. Oil major companies have identified key challenges in HPHT development and production, and service providers have offered insights regarding current or planned technologies to meet these challenges. Drilling into some shale plays such as Haynesville or deep formations and producing oil and gas at HPHT condition, have been crucially challenging. Therefore, companies are compelled to meet or exceed a vast array of environmental, health and safety standards. This paper, as a simplified summary of the current status of HPHT global market, clarifies the existing technological gaps in the field of HPHT drilling, cementing and completion. It also contains the necessary knowledge that every engineer or geoscientist might need to know about high pressure high temperature wells. This study, not only reviews the reports from the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) and important case studies of HPHT operations around the globe but also compiles the technical solutions to better maneuver in the HPHT market. Finally, the HPHT related priorities of National Energy Technology Laboratories (NETL), operated by the US Department of Energy (DOE), and DeepStar, as a strong mix of large and mid-size operators are investigated. Introduction:
Summary Tensile and shear failures are two common cement-sheath failure criteria. Tensile failure occurs when a stress on the cement surpasses the tensile strength of the cement, and shear failure happens when a stress exceeds the shear strength of the cement. The objective of this study is to introduce a laboratory method that investigates the effects of fatigue (cyclical loading) on the cement sheath. Chances of cement-sheath failure also increase when the application involves high-pressure/high-temperature conditions; therefore, this test setup is rated to 25,000 psi and 450°F. In this method, fatigue-failure cycle and stress magnitude could reveal the extent of the fatigue tolerance of different slurry designs relative to each other. One could program and adjust casing pressure (Pi), pore pressure (PP), temperature, cycle intervals, and ramp rates to conduct a cyclical-loading test automatically. Failures caused by thermal and stress loading may occur as a result of temperature and pressure-induced stresses created by well events such as hydraulic fracturing, cyclic steam injection, steam-assisted gravity drainage, production, completion, or remedial treatments. Thermal and stress cycles could impose a risk to zonal isolation and lead to a delay in hydrocarbon production. Studying such effects could be helpful in developing a better understanding of the cement-sheath-failure threshold and, in fact, could be complementary to mechanical-properties measurement. The cement sheath fails after a certain number of cycles when reaching its fatigue-endurance limit. This research showcases examples in which the fatigue-failure cycles were identified for 1,000-, 2,000-, and 5,000-psi pressure differentials between the pore pressure (exposed to the outside of the sheath) and the casing pressure. For these experiments, the pore pressure and temperature were held constant at 15,000 psi and 330°F whereas the casing pressure varied cyclically between 15,000 and 16,000 psi (Set A), 17,000 psi (Set B), and 20,000 psi (Set C).
Chances of cement sheath failure increase considerably when the application involves deepwater, high pressure high temperature (HPHT) conditions. Such failures may occur as a result of temperature and pressure-induced stresses created by well events such as hydraulic fracturing, cyclic steam injection, steam assisted gravity drainage (SAGD), production, completion, or other remedial treatments. Thermal and stress cycles could impose the risk of losing zonal isolation and lead to delay in hydrocarbon production.Cement mechanical properties measurment solely would not be sufficient to predict the failure threshold of a cement sheath. Some experimental studies were conducted about the effect of cyclical loading on the integrity of casing and drill strings but less research have been done about the in situ cement sheath integrity under cyclical loading. This paper introduces a new Ultra HPHT experimental set up and an applicable method to evaluate cement sheath integrity under cyclical loading. It also provides insights to find the cement fatigue failure cycle for the set cement at elevated pressures and temperatures.This system was built and completed by benefiting from the capabilities of an extreme HPHT Rheometer. Cement samples could be cured for number of hours in the newly developed HPHT cell and then instantly tested under cyclical loading in various scenarios at high temperatures. The cement sheath fails after a certain number of cycles when reaches its fatigue endurance limit. This research showcases scenarios in which the fatigue failure cycles were identified for 1,000 psi, 2,000 psi and 5,000 psi, pressure differentials between the confining pressure (exposed to outside of the sheath) and the casing pressure. During these experiments, the confining pressure and temperature were held constant at 15,000 psi and 330 ̊ F while the casing pressure varied cyclically between 15,000 psi and 16,000 psi (Set A), 17,000 (Set B) and 20,000 (Set C). A stable chemistry of Class H cement plus 35% silica was used to prevent cement retrogression. Cement sheath failures such as radial cracking, debonding and disking occured due to cyclical loadings. Finally, a fatigue failure envelope was generated by the obtained data. This curve represents the extent of cement sheath endurance at HPHT conditions under cyclical loading.
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...
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