Drilling Long Salt Sections Along the U.S. Gulf Coast
- J.W. Barker (Exxon Co. Intl.) | K.W. Feland (Exxon Co. USA) | Y.H. Tsao (Exxon Production Research Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 1994
- Document Type
- Journal Paper
- 185 - 188
- 1994. Society of Petroleum Engineers
- 1.14.3 Cement Formulation (Chemistry, Properties), 2.2.3 Fluid Loss Control, 1.6 Drilling Operations, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 5.1.2 Faults and Fracture Characterisation, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.14 Casing and Cementing, 4.1.5 Processing Equipment, 4.1.2 Separation and Treating, 1.1.6 Hole Openers & Under-reamers, 1.10 Drilling Equipment, 1.11 Drilling Fluids and Materials, 5.1.1 Exploration, Development, Structural Geology, 6.5.3 Waste Management, 1.14.1 Casing Design, 4.3.4 Scale, 1.6.6 Directional Drilling
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As the petroleum industry has matured along the U.S. gulf coast, the need to drill long salt sections to reach hydrocarbons has increased. This paper summarizes the special techniques that have been developed to drill long salt sections and reviews case histories where long salt sections have been successfully drilled. A new analytical equation to predict the rate of salt creep into a wellbore is also presented.
The U.S. gulf coast basin contains the largest known deposits of salt in the world. The many possible types of hydrocarbon traps near the salt structures increase the potential of significant hydrocarbon accumulation. The ability of salt to deform under temperature and pressure and its very low permeability and porosity make it a very successful hydrocarbon trap generator. At least 500 salt domes in the gulf basin have been penetrated in search of these traps, and up to 80% of proven gulf basin reserves probably are related to salt structures. Offshore in the Gulf of Mexico, salt sheets could be concealing oil- and gas-bearing strata under as much as 60% of the gulf in < 5,000 ft of water.
While drilling through salt structures has been done successfully for many years, recent experience and methods have improved the efficiency and reliability of drilling oil wells through long salt sections. The successful drilling of these wells demonstrates that these recently developed special techniques permit reaching hydrocarbon sources that may have been unreachable in past years.
The Gulf of Mexico basin was formed in the late Middle to early Upper Jurassic periods as North America separated from South America and Africa. Shortly after formation of the basins, evaporate salt (Louann) was deposited over thousands of years. The original bedded salt thickness has been estimated to have been 4,000 to 5,000 ft thick. Varying thicknesses of this salt are thought to underlie the entire present day gulf coast basin except for some localized areas. After Louann salt deposition, the basin filled with clastics and carbonates during the Upper Jurassic and Cretaceous periods. During Cenozoic and later periods, the gulf coast basin partially filled with sediments and was molded into a structurally complex region by growth faults, diaperism, and salt flow. Fig. 1 shows a cross section through a portion of the present-day gulf basin.
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