Optimizing Directional Drilling While Minimizing the Risk of Well Collision in Offshore Drilling

Abstract

As offshore drilling grows more crowded and more complex, greater emphasis is placed on avoiding collisions with offset wellbores. The implications of a collision with an existing well are very real, and care must be taken to minimize the risks associated with such incidents. Collision with a producing well carries additional risks, including potential well-control situations and lost income from shut-in wells. With more wells being drilled from multi-well locations, well collision is becoming a very real possibility. Today's drilling trends toward more directional, horizontal, and fishbone multilateral wells, often with several from a single slot using subsea wellheads. This paper covers the practices for sidetracking out of the well using a whipstock and minimizing the risk of collision with offset wells. Special emphasis is placed on optimizing whipstock placement (orientation and depth), use of gyroscopic tools while milling and drilling ahead, and the use of traveling cylinders for collision avoidance. Case histories are presented here to illustrate the successful application of these techniques. Introduction With the worldwide growth in drilling activities, operators are encountering increasingly complex and crowded drilling, especially in developed fields where the existing well density is high. In recent years reentry drilling has become an increasingly popular option for production optimization. One of the important aspects of reentry is to mill a window in an existing casing. Many of the wells drilled in developed fields are sidetracking from the existing wellbore. These cased-hole sidetracks are performed using a whipstock assembly. After setting the whipstock assembly, a rathole is drilled to land the drilling bottomhole assembly (BHA) to drill the rest of the section. After exiting the whipstock window, the sidetrack well will be under the magnetic interference from the parent wellbore and nearby offset wells. Depending on the proximity of the offset wells, magnetic interference can impair conventional measurement while drilling (MWD) for a substantial drilled distance. Drilling blind after exiting the window may result in catastrophic results, including colliding with a nearby existing producing wellbore. This paper emphasizes the following:Practices on whipstock placement, orientation to avoid collision risks and optimization of directional drilling at the same timeReducing directional uncertainties by using gyro MWD and single/multishot gyro tools while drilling close to the offsets wellsAnticollision management using traveling cylinder plot and spider plot

An investigation of electromagnetic anti-collision real-time measurement for drilling cluster wells

“…If not handled properly, this type of collision may cause severe environmental pollution, human injury, or death . To this effect, study regarding the prevention of wellbore collisions is of massive practical significance to the drilling industry (Guan et al, 2010;Oskarsen et al, 2009;Sharma et al, 2009;McNair et al, 2005).…”