RIASSUNTO
Abstract
""Dope??, an inorganic compound, has been used routinely during well construction for both casing and tubing to lubricate, seal and protect against corrosion of segment-connecting threads. During the well tubular assembly a portion of the thread compound is exuded inside and outside the connection and gets access to the well fluids through the tubing and annular space. Studies presented here show that the dope forms a suspension which penetrates and damages the formation. The studies used standard fluid circulation velocities during typical completion operations. The formation damage is severe (more than 99 percent) and has been confirmed with a number of core-test experiments, presented in this work.
If the well is put on injection service and in the case of workovers such as matrix stimulation treatments, the formation damage caused by pipe dope will almost guarantee operational failure. For production the issue is different and will depend on the reservoir permeability and the ability or lack thereof of the dope compound to penetrate the rock matrix or whether it will form a removable filter cake.
Recent innovative technologies have allowed the introduction of dope-free connectivity by engineering the connections at the end of pipe sections. Avoiding the use of dope compounds has apparent benefits, one of which is the prevention of well damage. Another is the efficiency and reliability of the operation itself, removing a cumbersome, albeit routine job, a major advantage in the hectic time of a drilling rig's operation. An important side benefit are improvements in the Health & Safety indicators of the casing & tubing installation- as the number of operations to install these is significantly reduced and also on the Environmental side, as the dope-free connections produce zero effluents , the connections being ""ready-to-run?? from the factory.
We present here the clear benefits of using dope-free pipe connections by quantifying the negative effects of the alternative. Production equations using a dope-induced skin effect are presented, showing the detrimental impact on well performance.
Introduction
Formation damaged caused by excess pipe dope on the inside wall of tubing that reaches the formation has been extensively reported (Maly et al., 1976), McLeod et al., 1983), Nasr-El-Din et al., 2002, Berry et al., 2003, Curtis et al., 2003). Recent studies have been carried out in order to characterize and quantify the damage (Funes et al., 2013).
Prevention is the most prudent practice to solve the problem of pipe dope plugging. Before ""Dope-Free?? connections were available in the market, the best available field practice was to reduce to the minimum the amount of dope applied to tubing connections. The problem is that doping in the field relies on human behavior, and there is a common tendency to apply an excess amount of dope to somehow ""guarantee?? the connections lubricity and sealability, specially for API connections but extended to premium connections as well.
A historical corrective action is a tube pickling recommended as a way to remove the excess pipe dope before acid treatments. This method has its limmitations.
Today, the use of ""Dope-Free?? connections for casing and tubing tubulars is technically the perfect solution to completely eliminate the formation damage caused by pipe dope.