When most people think of the cost of a well, they usually only consider the cost to drill and construct the well and contracts for new wells are often bid accordingly. However, the true cost of a well is actually what it costs you over its useful life. This includes not only the initial cost of drilling and constructing the well, but also periodic maintenance, rehabilitation, and repairs.
When viewed correctly, the most cost-effective well over its useful lifespan is not necessarily the well that was lowest cost to install in the first place. As a matter of fact, going for the least expensive well construction often results in a more expensive well over its lifespan.
Using lower cost mild steel for casing means the well is more subject to corrosion and therefore a shorter lifespan. 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 2-4 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 susceptible 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 result in 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 lifespan. 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 lifespan of the well based on the construction materials and design, add in expected rehabilitation costs, expected repairs, expected electrical efficiency differences, replacement costs a shorter lifespan well and other relevant factors. The difference in overall costs between a well lasting 80 years versus a well lasting 40 years that requires a replacement well after its useful lifespan may just surprise you.
