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Casing and tubing costs are significant factors in the well cost that must be properly estimated in the authority for expenditure (AFE). In some cases, they may account for 50 to 60% of the total expenditures. The costs are dependent on well depth, size, grade requirements, and couplings.
Pipe costs are influenced heavily by several factors. Pipe size is a major consideration. Fig. 1 illustrates cost variations according to pipe size for N-80 grade long-thread and coupling (LTC) pipe that exceeds a burst rating of 5,000 psi in several sizes. Although engineering considerations should have the major impact on the pipe size selection, cost considerations should have some influence.
Costs increase with higher pipe grades. Table 1 shows costs for 40.0-lbm/ft., 9.625-in. pipe with LTC couplings. As in the case of the pipe sizes, however, pipe-grade selection is an engineering decision. Couplings are seldom selected as a result of costs. However, higher-price premium couplings may allow the use of smaller pipe sizes, which will reduce the overall well costs (Table 2).
Casing (or cementing) accessory equipment is used to accomplish an effective primary cement job. Although the equipment does not have a major impact on well costs, it should be considered. Table 3 shows a typical suite of equipment requirements for running and cementing casing. This equipment would cost approximately U.S. $3,500 for a 7⅝-in. casing string and U.S. $25,000 for a 7⅝-in. liner.
Drive pipe cost
Drive-pipe costs must be calculated for wells that utilize the pipe. The charges vary for pipe sizes and wall thickness. A drive-shoe cost must be included. Typical drive-pipe size and costs are given in Table 4.