An integrated formation testing and production technology in fractured-vuggy carbonate gas reservoirs

Natural fractures are well developed in fractured-vuggy carbonate gas reservoirs, which are prone to lost circulation during plugging after formation testing or killing before production. Moreover, such lost circulation presents large volumes and high rates, and the complex cases of high lost circulation proneness and high difficulties in plugging, and lost circulation associated with kickoff are sometimes encountered. An integrated pipe string for formation testing–temporary plugging–production was designed, and an integrated formation test and production technology, enabled by the core tool of the pressure-controlled downhole disconnection on/off valve, was developed. With the presented technology, the reservoir can be quickly plugged by annulus pressurization; the upper pipe string can be tripped out without killing; the completion string can be tied back in clear water or low-density working fluids to connect the reservoir, which allows for production with no induced flow. Field applications showed that this technology can effectively avoid lost circulation during well killing after formation testing in fractured-vuggy carbonate gas reservoirs, significantly reduce reservoir damage, and improve recovery factor of primary production. The presented technology has excellent prospects for application promotion.