Underbalanced Completion Technology Using Gel Valve
The underbalanced completion technology using gel valve is a process to isolate upper killing fluid and reservoir with an effective sealing plug formed in the wellbore by using the gel valve gel system, so as to achieve underbalanced completion operations. The new tools developed independently include special guide shoes, special screen pipes and pipeline mixers.
Base fluid viscosity: 100~150mPa.s;
Gel viscosity: 1~6×104mPa.s;
Gelling time: 30s~180s;
Gel friction: 0.2~0.3MPa/100m;
Gel-breaking time: adjustable between 0 and 25 days;
Viscosity after gel breaking: <5mPa.s;
Technical principle of the completion technology using gel valve: injection of gel into the wellbore → forming of high-strength GBC gel → forming of an effective sealing plug → effective isolation of upper killing fluid and reservoir to prevent escape of toxic and harmful gases such as oil gas and hydrogen sulfide → round trip operations → running of completion string (such as screen pipe) → tubing running → installation of completion wellhead → backflow of gel → commissioning. The gel system is capable of sealing the wellbore while not entering into the reservoir, without causing any damage to the reservoir, so as to achieve the effective functions of isolation, sealing and pressure bearing and protect the oil gas reservoirs to a maximum extent.
The technology was first tested successfully on the site of Ya 940# Well of Yumen Oilfield in 2007. So far the completion technology using gel valve has been applied in 9 wells of Turpan-Hami, Yumen and Karamay oilfields, and the horizontal well water plugging as temporary plugging additive for reservoir protection was tested in one well with a success rate of 100%.