Single diameter expandable casing applications continue to advance

Tag : spe pipe

Single-diameter expandable casing applications continue to advance But the pace is slow, as the high cost of the technology keeps itto a niche category of applications. It's been a long-term goal-a holy grail of well construction-tocreate a well with only one diameter of casing. The savings intime, fluids, cement, hangers and other hardware, preventingconstricted completions and their effect on production, and manyother advantages are well documented,1 and they apply roughly inproportion to the slimness of the well. In other words,advantages accrue if just one string of intermediate, telescoping casing can be eliminated.

However, the added cost of expandables can offset the savings influids, cement, etc., such that operators are only using thetechnology when they have to. But there are signs that this may bechanging. We still have some time-perhaps five or more years-beforewe see a relatively deep well drilled with only a surface conductorand a single-diameter expandable pipe. What's needed are improvements in: fatigue resistance; burst andcollapse pressures; the speed with which the pipe expands; theability to make the downhole work performed in one trip, includingexpansion(s), cementing, sleeve-sliding (if any), excess pipecutoff and so on. Other improvements needed include expansion conesand associated equipment qualified for HPHT applications; theability to over-expand (i.e., form a bell) in casing sizes as smallas 5 in.; lower cost; and operators having sufficientfamiliarity-that is, a comfort zone-with the technology, whichwill only come with routine use. The strength issue is gradually being addressed with thickercasings, cones and launchers being built to higher specifications,and it should be remembered that in the overwhelming majority ofcases, expanded pipe is reinforced by covering it with a productionliner, which is often tied back to the surface.

Routine use of single-diameter technology is not the case today,and most of the money is still spent on contingencies. But even theword contingency is getting blurred, for if you've planned on andordered technology that will likely, but not certainly, be used, isit really a contingency? Perhaps planned workaround is a betterterm. The service providers are trying to make the case that solidexpandable tubulars don't just solve problems, they also savemoney. But with a little luck, a lot of hard work and some vigorouscompetition, prices should come down as experience goes up. Thisarticle is a status report on how far this technology hasprogressed to date.