Present Status and Development Comments on Horizontal Well Completion Techniques in China

Horizontal wells were drilled and completed in almost all kinds of reservoirs through decades of development,and many kinds of well completion method are available.However,two difficulties still exist in horizontal well completion in China,i.e.equilibrium drainage along horizontal wellbore in order to improve development efficiency,multi-stage fracturing in low permeability sandstone reservoirs.The technology to delay and control bottom water cresting in oil reservoirs with bottom water in China were described in detail.Those technologies included: combination control of water and gas cresting by water and gas production,selective well completion to control water cresting in perforated and open hole wells,intelligent water identification/plugging in horizontal wells and separated recovery and completion and equilibrium drainage techniques in horizontal wells.Equilibrium drainage completion techniques were introduced as a series,i.e.screen pipe water-control completion with variable blind-screen ratio,step screen pipe completion,combination of step screen pipe and screen pipe with variable blind-screen ratio,center water and pressure controlling completion.Current situation of multi-stage fracturing technologies in low-permeability formation was introduced,which included staged fracturing by hydraulic jetting,double sticking lifting,annular staged fracturing,liquid plug isolation,mechanical bridge isolation and horizontal well limited-entry fracturing.Optimal fracturing stage number was studied and it was shown that,reasonable fracturing stage number shall be determined according to the reservoir characteristics,to avoid mutual interference between fractures because of dense spacing or avoid large dead oil area because of sparse spacing.Finally,the development trend and suggestions were presented considering the development status of horizontal well completion technology in China.