First Implementation of CRA Casing in Sour HPHT Reservoirs in Deep Wells in Kuwait
- M. J. Al-Saeedi (Kuwait Oil Company) | D. Al-Enezi (Kuwait Oil Company) | M. Sounderrajan (Kuwait Oil Company) | A. K. Saxena (Kuwait Oil Company) | G. K. Gumballi (Kuwait Oil Company) | D. C. McKinnell (Total)
- Document ID
- Society of Petroleum Engineers
- North Africa Technical Conference and Exhibition, 15-17 April, Cairo, Egypt
- Publication Date
- Document Type
- Conference Paper
- 2013, Society of Petroleum Engineers
- 5.2.1 Phase Behavior and PVT Measurements, 1.6 Drilling Operations, 2.2.2 Perforating, 4.1.2 Separation and Treating, 5.8.9 HP/HT reservoirs, 1.3.1 Surface Wellheads, 1.10 Drilling Equipment, 1.14.1 Casing Design, 4.1.5 Processing Equipment, 4.2.3 Materials and Corrosion, 2.7.1 Completion Fluids
- HPHT, Jurassic, Kuwait, CRA Casing, Sour Gas
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- 429 since 2007
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Kuwait Oil Company has embarked on an ambitious project of drilling development wells to exploit the Najmah-Sargelu and Middle Marrat reservoirs at depths of 14,000 to 17,000 ft. These Jurassic formations consist of layered shales and limestones, which can be heavily fractured and highly pressured. The wells drilled to these prospects are very challenging because of HPHT conditions, narrow pore/fracture pressure windows, and high levels of H2S and CO2.
During drilling and production high concentrations of H2S and CO2 have been recorded. Given the strategic importance of these gas prospects, a study was undertaken into the metallurgy of materials planned for these production wells. With high levels of toxic gases and HP conditions, the severity of sour service was evaluated to be within the most severe area when referencing NACE standards. Dependent on well bore fluid and onset of any water production, Stress Corrosion Cracking (SCC) and Weight Loss Corrosion could occur leading to material failure and lost production. After this study, the use of CRA materials was recommended in future wells to counter these challenges.
The application of CRA for down hole tubular and surface wellhead equipment has gained wide acceptance in sour fluid service in recent years especially in HPHT wells. CRA usage has increased to; eliminate intensive corrosion inhibition programs, reduce maintenance costs and enhance safety. Considering the key parameters influencing corrosion properties of CRA (temperature, partial pressure of H2S and CO2, pH environment, chloride concentrations), it was decided to specify the use of 28 Cr CRA material for these Jurassic gas wells. This paper will discuss the initial study of the material metallurgy, the well design, the specification of tubulars and wellhead, special procedures necessary to run these exotic materials plus details of actual operations in the first wells.
Kuwait Oil Company has commenced an integrated field development project to produce gas and light oil from the Jurassic formations in the North Kuwait oilfields. This project is a major venture with currently nine deep rigs employed to drill around 120 wells to cover a nominal production of 1,000 MMscf/d of gas and 350,000 bbl/d of light oil. The wells target the Najmah-Sargelu and Middle Marrat formations in the Jurassic horizon, at depths of 14,000 to 17,000 ft. These zones consist of layered shales and limestones, which can be heavily fractured and are highly pressured.
Given the strategic importance of the North Kuwait Jurassic gas project and the related HPHT deep gas exploration well program, an extensive study was carried out to review the metallurgy of the materials used in well construction. The study targeted the main items which would be exposed to some degree of sour service; tubulars, hangers, packers, completion equipment and wellheads. For tubulars, the study concentrated on the production casings and completion tubing. The material review and recommendations were made considering the Sulfide Stress Cracking (SSC), Stress Corrosion Cracking (SCC) and any other type of corrosion which could occur for the intended applications over a well life of 12 - 15 years.
The severity of sour service was evaluated with reference to the latest NACE MR-0175/ISO 15156 severity diagram, and all proposed operating conditions were found to be within the most severe area for sour service.
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