Extended reach technology (ERT) has allowed the petroleum industry to reach and capitalize on reserves inaccessible to conventional drilling and completion methods. ERT has developed rapidly in the UK and Norwegian sectors of the North Sea. Given the type of well profiles, conventional wireline techniques are not appropriate to convey tools and manipulate completion hardware. Coiled tubing (CT) is well suited to conduct such operations.
A limitation on the horizontal displacement occurs because of the frictional forces between the CT string and borehole while running in CT. This causes helical buckling and can lead to lockup of the CT, thereby limiting reach.
When coiled tubing is wound off a reel and bent over the gooseneck and then passed through the injector into the well, the coiled tubing undergoes plastic deformation and is subjected to residual bend. The residual bend imposes contact forces between the CT and the wellbore.
A CT straightener was developed to remove residual bend and improve extended reach. A description of the CT straightener experiments and trials will be outlined. Additionally, the various techniques currently in use will be addressed briefly.
"The application of extended reach technology has resulted in extended field drainage radii, increased production rates, improved reservoir management, a reduction in required platforms and well counts and improved field economics…".
ERT has developed rapidly in the U.K., Norwegian and Danish sectors of the North Sea. Given the type of well profiles, conventional wire line techniques are not appropriate to convey tools and manipulate completion hardware. Due to the high angles of the long tangent sections combined with the TVD of the reservoir, such wells are known as extended reach wells. Coiled Tubing is well suited to conduct such operations. The definition of an extended reach well is a well with a measured depth to true vertical depth ratio (MD/TVD) greater than 2.0. A mega-reach well has a MD/TVD ratio greater than 3.0.