Research and application of controllable crosslinking temporary plugging rubber plug for killing well

There are security risks with pressurized workover treatment and formation pollution risk with conventional killing well fluid. This paper developed a controllable crosslinking temporary plugging rubber plug for killing well which take composite modified vegetable gum as the thickening agent, organic complex compound slowly releasing center ions as crosslinking agent, influence the release of center ionic of crosslinking agent through inhibitor, and indirectly control the crosslinking time through effecting ion release. The temporary plugging rubber plug has low viscosity at room temperature (≤36 mPa·s, 1 h), can pump injection easily, create the gel rapidly in the wellbore condition, then form a solid with very high intensity and viscoelasticity. The initial viscosity of it can reach more than 30 000 mPa·s at 120 ℃, keep the state of semi-solid to ge after 48 h aging. It has good viscoelasticity, good sealing effect to the wellbore, and can be broken down within 1-4 h after contact with the blocking fluid, so it can avoid the formation damage. This technology has been applied in the high temperature sulfur well with pressure switch valve operation, the oil pressure is from 59 MPa down to 29 MPa after 4 h pump injection temporary plugging rubber plug, the subsequent replacement of main control valve with pressure is success, and the fluid flow-back is smoothly after broken down(viscosity≤5 mPa ·s), so the oil pressure recovery is quickly.