Reducing the Risk of Plugging of Production Liner in Unconventional Wells

The productivity of unconventional wells can be impaired by plugging of a portion of the production liner caused by the deposition of proppant or formation solids in the lateral wellbore. This paper is aimed at studying the proppant transport in the lateral during flowback and post-flowback periods to diagnose this problem and evaluate possible solutions. Simulations of 4-phase gas-oil-water-solids flow were used for identifying sites where a stationary bed of solids can be formed in a multistage hydraulically fractured well. The simulations were carried out for the same well, the same operating conditions and two distinct completion methods, a plug-and-perf completion and a sliding sleeve system. Multiple completion design details, such as number of stages, inner and outer diameter of the production liner, configuration and size of flow ports, were incorporated into the well model. Experiments were conducted for two conditions with low and ultra-low mixture Froude number (Fr≪1), which occur in many completion stages of the lateral close to the well toe. The experimental setup consists of a test section comprising a transparent 11/4-in diameter pipe having two upward inclined sections. The study revealed that there are two types of proppant dispositions in the lateral: a stationary bed and a plug. A proppant plug may be result of a temporal flow reversal in a section, where the proppant holdup in the stationary bed is large (greater 50%). The stationary bed is not formed in the heel sections of a horizontal well with a large inclination angle (of at least 60 degrees or greater). Two plugging mechanisms were identified, both mechanisms are associated with the formation of the proppant bed, which may occur in one or several sections of the liner, depending on its trajectory, the completion method, and locations of flow ports. It was found that it is necessary to apply a certain pressure difference upstream and downstream of the proppant plug to make it move along the lateral. If the drawdown is smaller than this pressure difference, the formed proppant plug will not move and the production intervals upstream of the plug will be blocked. This may result in a substantial reduction in well productivity. Passive and active mitigation strategies to reduce the impact of proppant deposition in the lateral on well productivity were proposed. EUR can be increased by an optimization of drilling and completion practices directed to minimizing the risk of plugging of sections of the lateral. Active mitigation involves using a new artificial lift system for horizontal wells.