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rosion, and therefore a shorter life span. How many downhole videos have we seen of more mature wells where the casing is just one patch after another? Depending on subsurface conditions, stainless steel-constructed wells can have a serviceable life of two to four times that of mild steel or even high-strength low-alloy (HSLA) steel, more than offsetting the initial higher cost of using stainless steel. Using mill slot screen rather than a wire wrap means the well is more sus- ceptible to biofouling and mineral incrustations, which will dictate a shortened rehabilitation cycle. More frequent well rehabilitation will result in higher total costs over the life of the well. Utilizing a lower quality gravel pack can save on initial costs, but also results in the greater likelihood of mineral incrustations, sanding, and plugging with fines - once again requiring more frequent maintenance and rehabilitation, and probably shortening the useful life of the well, as well. When we put all this together, the importance of a quality design up front is crucial to the lowest overall cost of a well over its life span. The proper way to evaluate the true cost of a well is to take the initial drilling and construction costs, take into account the expected life span of the well based on the con- struction materials and design, then add in expected rehabilitation costs, expected repairs, expected electrical efficiency differences, replacement costs of a shorter life span well, and other relevant factors. The difference in overall costs between a well lasting 80 years versus a well lasting 40 years which requires a replacement well after its useful life span just may surprise you. Tom Tom Ballard may be contacted via e-mail to michele@worldwidedrillingresource.com Ballard cont’d from page 31. 36 APRIL 2019 WorldWide Drilling Resource ®