Multi-Stage Fracturing Techniques for Open Hole Horizontal Wells in Western Sichuan Tight Gas Reservoirs

RCWestern Sichuan shallow gas reservoirs are characterized as tight formation,low porosity and low abundance.For these types of reservoirs,a multi-stage open hole fracturing of a horizontal well is an effective method.However there are some difficulties associated with this technique such as the selection of fracturing parameters,running of fracturing string,displacement of mud in horizontal section and low flowback efficiency of fracturing fluid.Based on reservoir property analysis and multi-staged fracturing experience,it is suggested to fracture the open hole horizontal wells in 8 to10 stages with proppant concentration of 17%-21%.In the stage of fluid pad injection,a proppant slug is used to treat near wellbore effect,lower the initial fracturing pressure and avoid creating multiple fractures.Fracturing string for drilling fluid displacement in the horizontal section has been developed.Measures in mud circulation,string rotation and pressure application to string has been made to ensure the fracturing string can be run to the designed location.At the same time,liquid nitrogen injection and different sized chokes were employed to improve the rate and efficiency of fracturing fluid flow-back.Those measures were applied in 8 stages fracturing of Well XP105-1H successfully and natural flowback rate naturally reached up to 95%.Gas production of this well is 6.441 2×104 m3/d,two times of that of other horizontal wells in the same formation.It can be reference for similar open hole horizontal wells in tight gas reservoirs.